Content:
Presentation type:
SSP – Stratigraphy, Sedimentology & Palaeontology

EGU24-2710 | Orals | MAL31-SSP | Jean Baptiste Lamarck Medal Lecture

Sedimentary carbonates: fabrics, ultrastructures and geochemistry 

Silvia Frisia

Sedimentary calcium and magnesium carbonate minerals have recorded the evolution of life, climate, and CO2 cycling for billions of years through their physical and chemical properties.  These largely depend on crystallization pathways related to fluid pH and supersaturation, biological processes, presence of additives and redox conditions.  As such, crystallization pathways define the properties of biominerals and abiotic carbonates that are used to reconstruct Earth’s history.

Crystallization pathways, often preserved in carbonate ultrastructures have been widely investigated for biominerals and bio-mediated calcium and Ca-Mg carbonates by using High-resolution Transmission Electron Microscopy (HRTEM).  Synchrotron micro-X-ray fluorescence facilitates trace element mapping highlighted heterogeneities in their distribution as related to fabrics. Nano and micro-scale investigations of biominerals and bio-mediated carbonates have revealed that they consist of crystalline, nanocrystalline and amorphous phases, which may co-exist in the same sample and influence the distribution of trace, minor and major elements. Critically, the clustering of nanoparticles is considered a marker of biotic Ca-Mg-carbonates, whereas monomer- by-monomer crystal growth seems to characterize abiotic minerals. However, HRTEM investigation of abiotic sabkha dolomicrite formed primarily by aggregation of nanoparticles as a response to fluctuating aqueous chemistry. Abiotic cave CaCO3 minerals (speleothems), when observed by HRTEM also revealed that nanoparticle attachment is one of several crystallization pathways, that result in inter-and intracrystalline micro to nano-porosity and the formation of intracrystalline defects.   Critically, both inter- and intra-crystalline porosity and defects accommodate both organic macromolecules and inorganic colloids. The exploration of non-classical crystallization pathways, exemplified by particle attachment, explains the frequently observed non-equilibrium integration of trace elements. This phenomenon extends to the heterogeneous lateral distribution of both trace elements and organic molecules, providing insights into the intricate processes shaping the crystalline matrix.

Nano-scale observations further revealed that porosity follows crystallographic orientations, which leads to a hypothesis that sector zoning is responsible for lateral heterogeneity of organic and inorganic “impurities”. However, sector zoning largely stems from a classical monomer-by-monomer growth under pH and supersaturation ranges that are commonly lower than what expected for particle attachment. It is then plausible that local pH and supersaturation conditions as well as the presence of impurities result in changes in crystallization pathways. Nanoparticles participating in non-classical particle attachment may consist of amorphous calcium carbonate (ACC), whose uptake of trace elements differs from that of calcite. Transformation of ACC into calcite may ultimately result in an observed non-equilibrium partitioning of trace elements in the final phase. This phenomenon, in addition to the possibility that pores and crystal defects host impurities, suggests that multiple crystallization pathways explain kinetic effects that hinder a direct and constant link from proxy data to environmental parameters in carbonate archives of Earth’s history.

It is proposed that fabrics of abiotic carbonates, their ultrastructure and geochemistry should be granted the same level of investigation given to biominerals when interrogating their capability to accurately record climate (or environmental) change. Examples of how this can be achieved will be presented for case-studies including Triassic dolomicrite, Pleistocene subglacial carbonates from Antarctica and Holocene tropical stalagmites.

How to cite: Frisia, S.: Sedimentary carbonates: fabrics, ultrastructures and geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2710, https://doi.org/10.5194/egusphere-egu24-2710, 2024.

EGU24-21896 | Orals | MAL31-SSP | SSP Division Outstanding Early Career Scientist Award Lecture

New technologies applied to modelling taphonomic alterations of human origins 

Miguel Ángel Maté González

Taphonomy is a discipline dedicated to the analysis of the different processes that influence the mechanisms of fossilization, affecting both fossils and their environment. In this sense, this research is focused on the premortem and postmortem processes affecting animal bones found in archaeological sites. Studies related to human evolution can be approached from different perspectives, being paleontological analyses the best procedure for identifying ancestors through fossils. Paleo-environmental studies explore the past environment and climate, conditioning human evolution and adaptation. On the other hand, archaeological studies (the area of this research), examine the material culture and behaviour of ancient populations.

 

Sites can be exclusively paleontological, with no human intervention, or archaeological, with evidence of human activity. In the latter, bones may have been altered by humans, carnivores, or natural processes. In this context, taphonomy allows to classify the origin of this alteration, being even possible to define the intervention of several agents on the same animal, such as humans, carnivores, and rodents, and the order of such intervention.

 

Evidence of human intervention on animals from the past is found in the marks left when processing meat or marrow. The analysis of cut and percussion marks is used to reveal the applied tools and methods. The research here presented is based on the implementation of technologies such as photogrammetry and geometric morphometry to document these marks in a three-dimensional way. Machine learning, deep learning, and advanced statistics are then applied to answer specific questions. In particular, three main key questions about human behaviour in past populations have been addressed:

 

What tools were used to process animal meat, and were there any preferences in raw materials? Three-dimensional reconstructions are applied to identify the morphology of cut marks and, through repeated experiments, determine which materials, such as flint, quartz, or volcanic rock, were used in the past.

 

Which carnivores occupied the sites after they were abandoned by humans, and how does this affect the paleoecology? Tooth marks on bones are analysed to differentiate with high reliability which carnivore handled a bone, providing relevant information on the paleoecological implications depending on the specific carnivore.

 

How does trampling affect bones exposed at sites, and what relevant information does it provide? Through trampling analysis, it is possible to determine when this occurred, providing important data on how long the bones were exposed before burial and the degree of site disturbance.

 

All the previous lines of research enable to assess site integrity, identify the carnivores involved, and understand human behavioural strategies in the processing of animal carcasses.

How to cite: Maté González, M. Á.: New technologies applied to modelling taphonomic alterations of human origins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21896, https://doi.org/10.5194/egusphere-egu24-21896, 2024.

SSP1 – General Sessions

EGU24-1204 | ECS | PICO | SSP1.1

Neogene biostratigraphy in the  Niger Delta by  intergrating  foraminifera and  Paleo-oceonographic implications 

Joshua Avong Solomon, Enam Obiosio, Hamidu Ibrahim, Ubit Gospower, and Linus Anyanna

The Cenozoic Niger Delta formed after the separation of the African and South American plates.An integrated micropaleontology analysis was employed based on foraminifera studies  to determine age, biostratigraphic zonation, paleowaterdepth, paleosalinity and sea-level history of the well interval based on ditch cutting samples. Foraminifera preparation was based on standard micropaleontology preparation techniques and identification, which showed a high diversity and abundance of both planktonic and benthonic foraminifera occurrence. The planktonic foraminifera: Globigerinoides bulloidues, Globigerinoides primordius, Globorotalia obesa, Globigerinoides sp.,Catapsydrax stainforthi showed the entire deposition took place during the early to late Miocene (N6-N17) based on the First Downhole Occurrence (FDO) and Last Downhole Occurrence (LDO).The boundary resolution between the Early and Middle Miocene was identified based on the FDO of Catapsydrax stainforthi and the boundary between Middle and Late Miocene based on the FDO Globorotalia obesa. Two benthic biozones are proposed for the well interval equivalent to the N11-N17 and N6-N11 based on bioevents of chronostratigrahically significant benthonic foraminifera and whose stratigraphic range were well established in the Niger Delta and worldwide. Three third-order sea-level rises and falls occurred during the Early to Late Miocene within the Niger Delta, with a corresponding paleo-waterdepth from transitional to outer neritic based on biofacies such as ; Ammonia beccarii, Quinqueloculina microcostata, Poritextularia panamensis, Uvigerina subperegrina, Brizalina mandoroveensis, Lenticulina grandis and Eponides eshira.The maximum flooding surfaces shown by,the Chiloguembelina-3 Shale (16.0 Ma), Dodo Shale (11.6 Ma) and the Uvigerina-8 Shale (9.2 Ma), were associated with transgression. The 15.5 Ma SB of Depositional Sequence 1(Early Miocene), 10.5 Ma SB of Depositional Sequence 2(Middle Miocene) and 8.5 Ma SB of Depositional Sequence 3(Late Miocene) due to progradation, resulting in three depositional sequences established within the study interval. This showed  that the study interval was exposed to three local depositional cycles (cycle 6,9and 10), three regional cycles (cycles 2.3,2.6 and 3.1) within the TB2  and TB3 super cycles, correlated to the Niger Delta chronostratigraphic sea-level chart, which indicated that the sedimentary cyclic pattern was due to tectonics, eustatic and climatic conditions. Based on the triangular plot of the foraminifera test type (arenaceous, porcelaneous and hyaline), suggests a transition from the brackish marginal marine environment to open neritic conditions. The study interval is said to have penetrated sediments of the parallic Early to Late Miocene Agbada formation.

 

Keywords: Biostratigraphy, Early-Late Miocene, Planktonic Foraminifera, Benthic Foraminifera, sedimentary cyclic pattern

How to cite: Solomon, J. A., Obiosio, E., Ibrahim, H., Gospower, U., and Anyanna, L.: Neogene biostratigraphy in the  Niger Delta by  intergrating  foraminifera and  Paleo-oceonographic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1204, https://doi.org/10.5194/egusphere-egu24-1204, 2024.

  The sandy shoreface reservoir exhibits a uniform lithology overall, with generally low overall heterogeneity. However, in the actual dynamics of reservoir development, the internal characteristics still reveal a complex oil-water relationship, indicating that the internal structure of the marine shoreface sand reservoir is intricate, and heterogeneity is pronounced. Therefore, it is imperative to conduct a quantitative characterization of the reservoir structure to provide theoretical and technical support for the interpretation of oil-water distribution and to further facilitate potential exploration.

  To solve the above problems, this paper, guided by the sedimentary genetic model, systematically quantified and characterized the architectural interfaces and architectural units in hierarchical order. On this basis, the influence of configuration interfaces and configurational units on the distribution of remaining oil was investigated, forming a set of multi-level architecture methods for quantitatively characterizing the internal structure of shoreface reservoirs. The specific steps are as follows: (1) After establishing that the third-order and fourth-order architectural elements primarily influence the oil-water distribution interface within the closely spaced well pattern area, the third-order and fourth-order architectural interfaces of the reservoir are quantitatively identified. This identification is based on the sedimentary genetic model and is integrated with data from both vertical and horizontal wells. A quantitative relationship is then established between the maximum thickness and maximum extension length of the third-order and fourth-order architectural interfaces in both parallel and vertical paleo-shoreline directions. The distribution characteristics of these interfaces, along with the progradation and regression evolution traits of the third-order architectural interfaces along the vertical paleo-shoreline, are precisely defined. (2) Building upon the identification of architectural interfaces, the focus is placed on the classification, recognition, and distribution studies of third-order and fourth-order architectural units. The distribution characteristics of different-order architectures are delineated in detail, and a developmental model for third-order architectural units is established. Finally, the reservoir architecture characterization results are validated using production dynamic data, confirming that the method accurately characterizes the internal structure of sandy shoreface facies reservoirs and quantitatively depicts their internal heterogeneity. The quantitative characterization of the marine shoreface sand reservoir architecture not only enriches the research content on reservoir architecture but also provides theoretical support for the characterization of heterogeneity in marine facies reservoirs.

How to cite: Zuo, W. and Ren, L.: Architecture Characterization of Shoreface Reservoir: A Case Study from the Donghe Sandstone Reservoir in the Hudson Oilfield, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1549, https://doi.org/10.5194/egusphere-egu24-1549, 2024.

EGU24-2319 | ECS | PICO | SSP1.1

Ontogenetic Sequence Analysis Reveals Extensive Sequence Polymorphism in Tyrannosaurus rex 

Elias Warshaw, Daniela Barrera Guevara, and Eric Yu

The study of ontogeny in fossil organisms is vital to broader understanding of their ecology and evolution. Ontogeny in Tyrannosaurus rex (Theropoda: Coelurosauria) has been studied extensively by dinosaur researchers, documenting the transition from small juvenile to gigantic adult. Previous authors have regarded this transition as largely linear, serving as a model for understanding growth and development in other tyrannosaurids as well as theropods as a whole. However, the presence of sequence polymorphism (variation in the temporal order of developmental events) has yet to be investigated for this taxon, representing a potential source of error for published ontogenetic series. Here we present the first Ontogenetic Sequence Analysis (OSA) of Tyrannosaurus, recovering extensive sequence polymorphism in a previously published ontogenetic character matrix. In contrast to ontogenetic series of Tyrannosaurus recovered by cladistic ontogenetic methods, we find a significant correlation between maturity and body size among large adult specimens, and corroborate previous assertions of a relationship between histologic and morphological indicators of maturity. Our results highlight the prevalence of sequence polymorphism among saurischian dinosaurs, and demonstrate the importance of considering such variability when attempting to reconstruct the ontogeny of fossil vertebrates. We expect that further study will reveal similar variability across closely related taxa and recommend that this possibility be incorporated into interpretations of morphological variation in tyrannosaurids.

How to cite: Warshaw, E., Barrera Guevara, D., and Yu, E.: Ontogenetic Sequence Analysis Reveals Extensive Sequence Polymorphism in Tyrannosaurus rex, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2319, https://doi.org/10.5194/egusphere-egu24-2319, 2024.

In order to clarify the sedimentary system evolution and sandbody development characteristics of Shaximiao Formation, this paper takes the Shaximiao Formation in the central Sichuan Basin as the research object to systematically study the sedimentary microfacies and sandbody genetic types of Shaximiao Formation by using core data, thin section analysis, logging and seismic data comprehensively. And the following research results are obtained.

First, due to the gradual uplifting of the Daba Mountain and the Micang Mountain on the northeast, the Sichuan Basin was a NE-SW trending foreland basin during the sedimentation of Shaximiao Formation, the topography in the basin was wide and gentle and the ancient water system was mainly in the NE-SW direction, so the sedimentary pattern of Shaximiao Formation in the central Sichuan Basin is under the joint control of the Daba Mountain on the north and the provenance on the south.

Second, glauconite minerals are common in the sandstone of the central Sichuan Basin, indicating that the depocenter of Shaximiao Formation is located in the center of the basin. Shaximiao Formation is characterized by frequent alternation of dry and wet climate, shallow and turbulent lake basin and wide and gentle terrain, and has the sedimentary background to form shallow water deltas.

Third, the shallow water deltas developed in the first Member of Shahejie Formation under the condition of semi-arid climate are mostly in the shape of lobate, with a wide distribution of sedimentary facies. In the plane, they are presented as a complex of multiple lobates, sandbodies are overlapped and developed continuously, single-phase channel sandbodies are wide and river mouth bars are common.

Fourth, branched distributary channel-type shallow water deltas are mainly developed in the second Member of Shahejie Formation under the condition of arid climate, and they are mostly in the shape of bird’s foot or branch. Sandbodies are distributed in strips along channels, which are narrow and cut each other. River mouth bars are only distributed at the channel end, with a small single scale.

In conclusion, this paper systematically analyzes the evolution and distribution laws of sedimentary facies of Shaximiao Formation in the central Sichuan Basin and summarizes the sedimentary characteristics and sandbody development models of Shaximiao Formation.

How to cite: Liang, W., Qiu, L., and Yang, Y.: Sedimentary system evolution and sandbody development characteristics of Jurassic Shaximiao Formation in the central Sichuan Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2398, https://doi.org/10.5194/egusphere-egu24-2398, 2024.

  The subaqueous coarse clastic rock fans in the Northern Bonan Depression of the Bohai Bay Basin are one of the typical reservoirs for oil and gas accumulation in the Mesozoic-Cenozoic continental rift basin. With the comprehensive exploration of oil and gas fields in eastern China transitioning from the concealed exploration phase to the refined exploration phase, the lack of understanding of the internal structure and distribution law of favorable zones within the subaqueous coarse clastic rock bodies has seriously hindered the exploration and development of such oil and gas reservoirs. This paper focuses on the subaqueous coarse clastic rocks of the third member - fourth member of the Shahejie Formation(Es3–Es4) of Northern Bonan Depression as the research objects. By integrating seismic, logging, core, and analysis tests, investigating the genetic types, sedimentary structures, and transport processes of subaqueous coarse clastic rocks under differential tectonic activities. Furthermore, a comparative analysis of reservoir characteristics and the main controlling factors for reservoir properties are carried out for different types of subaqueous coarse clastic rock bodies, aiming to provide a clear understanding of the development mechanisms of high-quality reservoirs. The following understandings have been obtained.

(1)A sedimentary evolution sequence of subaqueous coarse clastic rocks controlled by differential tectonic activity is proposed. In Es4, thesegments of the boundary faults experience a low tectonic subsidence rate, relatively gentle topography, and sufficient sediment supply, fan deltas form. The subaqueous distributary channels cut each other, migrate and swing frequently, resulting in a wide lateral distribution of the fans.In Es3,the segments of the boundary faults experience high tectonic subsidence rates and large drops, which contribute to the development of nearshore subaqueous fans. The internal migration and superposition of multi-stage fan bodies occur, while the lateral migration capacity of braided channels is weak, and vertical accretion dominates the overall deposition.

(2)This study has identified the differences in lithology, reservoir characteristics, main authigenic mineral types and contents of subaqueous coarse clastic fans during the third member - fourth member of the Shahejie Formation of Northern Bonan Depression。The parent rock of fan delta is mainly composed of metamorphic rocks, while the nearshore subaqueous fans consists of metamorphic rocks and mixed parent rock. The reservoir space type is dominated by feldspar and igneous rock fragment dissolution pore. The highest pore surface porosity is found in the fan delta, followed by the nearshore subaqueous fans。

(3)Quantitatively evaluated the differences in diagenesis subaqueous coarse clastic rock reservoirs during the third member - fourth member of the Shahejie Formation of Northern Bonan Depression,and clarified the types of favorable sedimentary facies belts. The sedimentary environment of the fan delta shows medium compaction, weak cementation, and strong dissolution, medium to strong compaction, medium to strong cementation, and weak to strong dissolution for the nearshore subaqueous fans。 The subaqueous distributary channel of fan delta, braided channels in the nearshore subaqueous fan are the most favorable sedimentary facies。

 

How to cite: zou, Y. and Qiu, L.: Depositional Characteristics and Reservoir Formation Mechanism of Subaqueous Coarse Clastic Rocks along Steep Slopes in a Continental Lacustrine Rift Basin: A Case Study of Northern Bonan Depression, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2530, https://doi.org/10.5194/egusphere-egu24-2530, 2024.

The Sichuan Basin is an expansive Mesozoic-Cenozoic basin in the southwestern mainland of China, with dinosaur fossils widely scattered and full-type accumulated in the Jurassic strata. Wangcang dinosaur fossil burial site is located at the southern foot of the Qinling Mountains and the southern wing of Micang Mountain Uplift in the northern Sichuan Basin. Geologic cross-section measurement, fieldwork, and study of 3D seismic profiles are carried out to explore the mechanism of rapid accumulation and burial of rich incomplete dinosaur fossils in Wangcang. 
The results show that both the sedimentary process and the tectonic function of the Shaximiao Formation in Wangcang have undergone major changes due to basin and mountain relationships during the sedimentary period. The Shaximiao Formation experienced a transition from the lacustrine sedimentation of the Qianfoya Formation to fluvial-deltaic facies, suggesting climatic and environmental changes. Notably, the Second Member of the Shaximiao Formation coincided with intensified seismic activities, we identified indicators of seismites, including sand pillows, seismic fractures, step faults, liquefied veins, shattering rocks, and seismic breccias, etc. Each set of seismites has different vertical sequences, and the typical liquefied structure deformation directly suggests seismic activities. Tectonically, while the Qianfoya Formation displayed reverse faults, the Shaximiao Formation showed a series of strike-slip normal faults. The seismites and sediment tectonic features reveal a correlation with the catastrophic mass mortality of dinosaurs in Wangcang. We propose that seismic events significantly impacted dinosaur habitats, leading to mass deaths and subsequent burials in the purplish-red argillaceous siltstone near Huaishu Village in Wangcang. For the first time, the seismites are presented as new evidence of tectonic shifts and seismic activities in Wangcang during the Middle Jurassic, and it provides a new perspective for dinosaur taphonomy in the Sichuan Basin.

How to cite: Guo, Y.: Seismites of the Jurassic Shaximiao Formation in NW Sichuan Basin of SW China: Implication for Dinosaur Taphonomy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2681, https://doi.org/10.5194/egusphere-egu24-2681, 2024.

EGU24-4882 | PICO | SSP1.1

Sedimentary environment of Tangenshan sandstone in southwestern Taiwan and its tectonic implications 

Tien-Kai Tang, Guan-Wei Lin, Le-Chun Wu, Kenn-Ming Yang, and Sung-Ping Chang

The most widely distributed shallow marine sandy formations in the western foothills of Taiwan is the Guizhulin Formation of late Middle Miocene to early Pliocene age, along with its contemporaneous strata. Its facies transition is also the most prominent, exhibiting an overall trend of increasing sedimentary environment depth from north to south. The lower part of the Guizhulin Formation in northern and central Taiwan, is of late Middle Miocene age and can be correlated to the Tangenshan Sandstone in southwestern Taiwan. According to numerous previous studies, in terms of tectonic evolution for the western foothills terrain, the former have been regarded as the accumulation in the early stage of the foreland basin (syn-orogenic) to the north of the Peikang High, whereas the latter represents the deposits in the passive continental margin stage (pre-orogenic) to the south of the Peikang High. In order to understand the sedimentological distinction between the lower part of the Guizhulin Formation and Tangenshan Sandstone, this study reconstructs and analyzes stratigraphic columns and lithofacies of the Tangenshan Sandstone, which is approximately 380 meters thick and exposed in the hanging wall of the Chutouchi Fault in the Kueitanchi section in the Tainan area, southwestern Taiwan. Observations and records of trace fossils were also utilized to comprehensively reveal the variations in sedimentary environment and the characteristics of depositional facies in the study area. The aim of this study is to investigate the tectonic implication for the variations in the sedimentary environment based on the sedimentology study results.

Based on the descriptions in the field, the lithofacies can be categorized into one mudstone facies, two siltstone facies, and three sandstone facies. According to the lithofacies association, they can be further subdivided into channel deposits and non-channel deposits, indicating two distinct sedimentary features. It is inferred that the sedimentary environment during the deposition was primarily an offshore depositional system dominated by storm wave and possible turbidity currents. Lithofacies association indicates that the thick sandstone layers in the study area were transported deeper in the continental shelf by turbidity currents induced by storms. These currents carried coarse-grained sediments below the average storm wave base, resulting in the formation of submarine channels and finer-grained non-channel deposits. The overall sedimentary characteristics resemble those of shallow water turbidite deposits in terms of features and mechanisms. Furthermore, with comparison with previous research results, it is inferred that the deposition of the Tangenshan Sandstone in the study area was in an atypical passive continental margin environment but rather influenced by pre-orogenic normal faulting, leading to an increase in thickness but decrease in sedimentary environment depth of the contemporaneous Tangenshan Sandstone deposits from the west (basin margin) to the east (basin center).

How to cite: Tang, T.-K., Lin, G.-W., Wu, L.-C., Yang, K.-M., and Chang, S.-P.: Sedimentary environment of Tangenshan sandstone in southwestern Taiwan and its tectonic implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4882, https://doi.org/10.5194/egusphere-egu24-4882, 2024.

 In order to better predict the connectivity of sand body in the shallow water delta front, taking the shallow water delta front sand body in the Kong 1st section of the Fenghuadian Oilfield in Huanghua Depression as an example, quantify and optimize the factors that affect the sand body connectivity, and then establish a nonlinear mapping model with the optimized parameters and the connectivity level of sand bodies to quantitatively predict the sand body connectivity by using extreme learning machine, and the predicted results are compared with those of support vector machine to analyze its effectiveness and advantages. Finally, apply the model to the study area to verify its practical application effect. The results show that: 1) Four parameters, including sand-ground ratio, interlayer thickness, interlayer density and permeability, were selected to predict sand body connectivity by using extreme learning machine algorithm, and the accuracy rate reached 92.33%. Extreme learning machine has higher training efficiency than support vector machine algorithm while ensuring prediction accuracy. 2) The extreme learning machine training model was applied to predict the sand body connectivity of ZV2-1 sand layer in the study area, and the dynamic verification coincidence rate is over 92%, which has a good application effect. 3) There are two types of inter-well sand body connectivity modes in the study area: lateral connectivity and internal connectivity. In the lateral connectivity mode, if the two sand bodies are laterally cut and have similar thicknesses, the connectivity is good. In the internal connectivity mode, if the interbeds within the sand body are not developed, the connectivity is good.

How to cite: Wang, J. and Zhang, X.: Quantitative evaluation of sand body connectivity in shallow water delta front based on extreme learning machine, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5194, https://doi.org/10.5194/egusphere-egu24-5194, 2024.

We present a heavy minerals study of several sedimentary units deposited within the Yukon-Koyukuk basin (YKB) in Alaska. The YKB started to form in middle to late Jurassic after the collision between an intraoceanic volcanic arc and the Arctic Alaska margin. The collision led to thrusting of the seafloor (mafic and ultramafic rocks of the Angayucham Terrane), over the future Brooks Range and Ruby Terrane. The basin is flanked on three sides by metamorphic rocks of the Seaward Peninsula to the west, the Ruby terrane to the east and the Brooks Range to the north. The remnants of the volcanic arc (Koyukuk Arc Terrane, KAT) divide the basin into a northern Kobuk-Koyukuk basin (KKB) and a southern Lower-Yukon basin (LYB).

We present results from the Kv, Kvg, Ks, Kms, Kmc, and Kqc units (after Patton et al.2009), collected along the Koyukuk and the Yukon rivers. The units are as follows:

  • Kv: formed by basaltic and andesitic lava flows interbedded with volcanogenic conglomerate to mudstone rocks. K-Ar ages vary from 134 Ma and 118 Ma with a U-Pb age obtained through a tuff of about 138 Ma.
  • Kvg: mainly consists of volcaniclastic greywacke and mudstone interbedded with tuffaceous layers which gave U-Pb ages comprised between 112 and 110 Ma (Albian). Molluscs of the same time have been reported throughout the entire unit.
  • Kms: mainly fine to coarse sandstone interbedded with shaly layers. Interpreted to be the marine tongue of the Ks deposits.
  • Ks: late Cretaceous in age, this unit consists of alternations of sandstone and shale layers deposited in fluvial to shallow marine environments.
  • Kmc: mafic igneous clasts conglomerate with mafic and calcareous greywacke and mudstone. Marine molluscs of Cretaceous age have been found.
  • Kqc: overall a quartz rich unit composed of conglomerate, sandstone and mudstone. Plant fossils date the unit to the Cretaceous.

We use Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN®) for heavy mineral (HM) analysis to establish a clear relationship between sediments and source regions and build a model for the basin formation and evolution. Kv and Kmc samples reflect a volcanic source, while Kvg, Kms, Ks, and Kqc display the progressive unroofing of deeper and higher grade metamorphic rocks. Combining these data with DZ and U-Pb absolute ages, we interpret the YKB to be formed prior to 138 Ma as the forearc basin of the intraoceanic arc. It evolved into a hinterland setting at about 110 Ma when the first deposition of metamorphic detritus is recorded by the Kvg unit, mainly derived from erosion of the Brooks Range.  Limited paleocurrent data along with the novel HM data attribute the Ks, Kms, Kmc and the Kqc to the erosion of the Ruby terrane as it uplifted during middle to late Cretaceous time.

How to cite: Seminara, S., Pease, V., and Toro, J.: Heavy mineral analyses to reconstruct basin evolution, an insight from the Yukon-Koyukuk basin sandstones, Alaska. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5303, https://doi.org/10.5194/egusphere-egu24-5303, 2024.

EGU24-5326 | ECS | PICO | SSP1.1

Fossil Coleoptera with in situ and adhered pollen from the Eocene of Eckfeld, Germany 

Johannes Martin Bouchal, Christian Geier, Silvia Ulrich, Dieter Uhl, Sonja Wedmann, Torsten Wappler, and Friðgeir Grímsson

The middle Eocene Eckfeld maar (c. 44 Ma) deposits in Germany are known for numerous well-preserved fossils they have yielded until today. Among these records, thousands of insects have been recorded that potentially provide direct evidence for flower visitations and entomophilic pollination processes. In order to obtain data on flower visits and possible pollinator roles, we extracted pollen from selected groups of fossil Coleoptera from Eckfeld and studied them with light microscopy (LM) and scanning electron microscopy (SEM). In total, we screened 332 Coleoptera: 51 Buprestidae (six with pollen), 21 Cerambycidae (two with pollen), 87 Chrysomelidae (four with pollen), 80 Elateridae (three with pollen), ten Eucnemidae (one with pollen), 78 Scarabaeidae (three with pollen), and five Throscidae (no pollen). The beetles were screened for both in situ pollen occurring in their digestive system and adhering pollen occurring on various parts of their exoskeleton (head, thorax, abdomen, leg etc.). The pollen was most frequently associated with members of Sagrinae, a subfamily of leaf beetles (Chrysomelidae), and Agrilinae, a subfamily of jewel beetles (Buprestidae). The adhering or in situ pollen can be assigned to at least 15 different taxa. While some are unique and only associated with one beetle specimen (e.g., Malvaceae, Moraceae), other pollen types were found associated with two or more beetle specimens, namely, Castaneoidea, Euphorbiaceae, Oleaceae, Onagraceae (Ludwigia), Sapotaceae, and Vitaceae (Parthenocissus).

How to cite: Bouchal, J. M., Geier, C., Ulrich, S., Uhl, D., Wedmann, S., Wappler, T., and Grímsson, F.: Fossil Coleoptera with in situ and adhered pollen from the Eocene of Eckfeld, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5326, https://doi.org/10.5194/egusphere-egu24-5326, 2024.

Provenance analysis is the foundation of basin analysis, and also an important means to restore the tectonic background of the sedimentary source area, estimate transport paths and distances of sediment, reconstruct paleocurrent systems, and reproduce the evolution history of sedimentary basins.The Bozi-Dabei area is located in the northwestern margin of Kuqa Depression in the Tarim Basin, where Bashijiqike Formation and Baxigai Formation of the Lower Cretaceous are held by multiple uplifts, which leads to the possibility of multiple provenances. Thus, detailed study of the provenance characteristics is needed to ascertain the the supply range and duration time of the indefinite provenances.

We identify the sediment provenance combining proportion of stratum lithology, rock and mineral compositions, and heavy mineral combination characteristic. And the paleocurrent direction is interpreted by the bedding dip direction obtained from imaging logging.

In the study area, there is an overall decreasing trend of the ratio between sandstone and stratum thickness from north to south, indicating that the South Tianshan on the north is the main provenance for this area, while the anomalous high-value zone in the southwest suggesting the possibility of regional provenance. According to the petrologic and mineralogical data of sandstone composition, detritus component, and heavy minerals, there is a certain regular variation from the northwest and northeast of the study area to the central location, such as the increasing proportion of quartz, metamorphic debris, and stable heavy minerals like garnet. Meanwhile, consistent heavy minerals combination with those in South Tianshan indicates that sediments originated from this provenance and were supplied to the study area along two paleocurrent systems.Consistent with the proportion of stratum lithology, the rock and mineral composition in the southwest, high magmatic grains and zircon for example, differs significantly from most parts of the study area. Combination characteristic of heavy mineral shows difference compared to those from South Tianshan provenance but matching those from Wensu Uplift, suggesting a local sediment supply from Wensu Uplift on the southwest. Paleocurrent data indicate three paleocurrent directions: NNW-SSE direction in northeast; NNE-SSW direction in northwest; SW-NE direction in southwest - all consistent with three paleocurrent systems indicated by rock and mineral compositions.

The results show that sediments originating from both South Tianshan and Wensu Uplift have been deposited into DFS during sedimentary period.The proportion of stratum lithology, rock and mineral composition, as well as bedding occurrence indicate that during Baxigai Formation deposition period, Wensu Uplift had a larger influence range which gradually diminished during Bashijiqike Formation deposition period - possibly implying a further tectonic uplift of Tianshan due to Himalayan movement.

How to cite: Ju, Q., Ren, L., and Luan, G.: Evolution of Early Cretaceous Multi-provenance deposition system in the northwestern margin of Kuqa Depression: Evidence from stratigraphic lithology proportions, mineral composition, and bedding dip direction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5569, https://doi.org/10.5194/egusphere-egu24-5569, 2024.

EGU24-5607 | ECS | PICO | SSP1.1

Eocene flower visitation of European Diptera and their potential pollinator role 

Christian Geier, Johannes Martin Bouchal, Silvia Ulrich, Dieter Uhl, Sonja Wedmann, Torsten Wappler, and Fridgeir Grimsson

Pollination by insects, including flies, is commonly a mutualistic interaction, in which both the plant and the insect benefit. Compared to other groups of pollinators or flower visitors relatively little is known about flower visitation by flies (Diptera) during most of the Cenozoic. Until now, the fossil record has provided only a few reliable fossils where flies are preserved with in situ or adhered pollen from flowers they visited before death and fossilization. Here, we report preliminary results from an ongoing study on flower-dipteran interactions during the middle Eocene of Central Europe. We screened 220 Diptera (19 with pollen) from the Middle Eocene of Messel and 20 Diptera (one with pollen) from the Middle Eocene of Eckfeld. The flies were screened for in situ pollen in their digestive system and adhering pollen present on various parts of their exoskeleton (head, thorax, abdomen, leg, etc.). From Messel, we studied, among other Arthropoda, 65 Brachycera (=flies; eleven with pollen) and 93 Nematocera (incl. gnats and midges; six with pollen). Out of the 20 pollen-bearing specimens, one had both gut content and adhering pollen, seven had only gut content pollen, and twelve had only adhering pollen. Each fly had between one and seven different pollen types. The number of pollen types found on the flies suggests both oligo- and polylectic feeding behaviour depending on the taxon. Only a few of the same pollen types (four pollen types) were found on different flies. In total we discovered 19 different pollen types on all the fossil fly specimens. The pollen represents, among others, Araliaceae, Cornaceae, Hamamelidaceae, Juglandaceae, Lythraceae (Decodon), Oleaceae, Rutaceae, Sapotaceae, and Vitaceae (Parthenocissus). Surprisingly, four flies carried Juglandaceae pollen on their exterior, but today, this family is mainly wind-pollinated. The amount of in situ pollen discovered was, in most cases, filling the whole digestive system of the flies, suggesting long and active feeding from anthers of flowers. About half the flies bearing adhered pollen had considerable amounts on their exterior, suggesting they could be potential pollinators of the plants they visited, especially Araliaceae, Hamamelidaceae, and Sapotaceae.

How to cite: Geier, C., Bouchal, J. M., Ulrich, S., Uhl, D., Wedmann, S., Wappler, T., and Grimsson, F.: Eocene flower visitation of European Diptera and their potential pollinator role, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5607, https://doi.org/10.5194/egusphere-egu24-5607, 2024.

EGU24-6084 | ECS | PICO | SSP1.1

Upper Pleistocene in Mallorca: Sedimentary variability of littoral deposits in relation to different structural contexts 

Federica Perazzotti, Laura Del Valle, Lluís Gómez-Pujol, and Joan J. Fornós

This comprehensive study explores the Upper Pleistocene geological history of Mallorca, employing a multifaceted approach that integrates previous findings with new insights. The research spans various coastal regions, focusing on four distinct study areas characterized by different geomorphological and structural contexts. The first structural context, exemplified by Port des Canonge, showcases folded and thrusted deposits, resulting in prominent cliffs with Jurassic and Triassic formations. The second context, observed in Caloscamps, features smoother reliefs and notable terrestrial sediment input. Meanwhile, the third context, represented by Punta de s’Avançada and Punta de n’Amer, exhibits cliffs  carved on Upper Miocene tabular deposits devoid of terrestrial sediment input. The main objective is to provide a comprehensive understanding of the geological and sedimentological characteristics of the Upper Pleistocene deposits across Mallorca's coastal regions by investigating different study areas located along the west, north-west, north-east, and east coasts, in distinct geomorphological and geological contexts through a multifaceted approach using classical sedimentological methodologies: stratigraphic analysis, X-ray analysis, microscopic techniques, and assessment of sediment color. Additionally, Optically Stimulated Luminescence (OSL) dating techniques are employed, providing a precise temporal framework spanning Marine Isotope Stage 6 (MIS 6) to Marine Isotope Stage 3 (MIS 3). The findings reveal the complex interplay of environmental factors, climatic variations, and geological evolution across Mallorca. Colluvial deposits and paleosols reflect climatic shifts. Alluvial fans and aeolianites highlight periods of intense sediment transport and deposition linked to climate fluctuations. Fossil evidence, such as tracks and trackways associated to Myotragus balearicus, contributes to understanding evolutionary adaptation and isolation, offering unique insights into the island's paleontological legacy. Finally, to provide a comprehensive overview of the outcrops present on the island, a stratigraphic correlation of the mentioned areas was conducted, integrating data from seven other study sites (Es Caló, Punta Manresa, Platja de sa Font de Sant Joan, Sa Ferradura, s’Estret des Temps, Es Carnatge and Ses Penyes Rotges). In conclusion, the study enhances our comprehension of Mallorca's coastal dynamics, geological composition, and environmental history, providing invaluable contributions to the broader understanding of Pleistocene deposits.

How to cite: Perazzotti, F., Del Valle, L., Gómez-Pujol, L., and Fornós, J. J.: Upper Pleistocene in Mallorca: Sedimentary variability of littoral deposits in relation to different structural contexts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6084, https://doi.org/10.5194/egusphere-egu24-6084, 2024.

To understand the influence of downstream changes in hydrodynamics on floodplain sedimentation and associated channel avulsion in stream-dominated alluvial fans, we studied the Cretaceous Duwon Formation in the southern Korea (Goheung area). The Duwon Formation unconformably overlies the Paleoproterozoic basements and mainly consists of braided stream and calcrete-bearing floodplain deposits. Close to the basements, channel deposits show radial paleoflow patterns, and the sediment size and ratio of channel to floodplain deposits decrease downstream over a relatively short distance (< 7 km). These lines of evidence indicate that the Duwon Formation was deposited in the stream-dominated alluvial fans under arid to semi-arid climatic conditions, which can be classified into the proximal, medial, and distal zones. In the medial zone, floodplain deposits are mainly composed of purple sandstones and compensational stacked crevasse channel and splay deposits with unsystematic paleoflow directions. Whereas in the distal zone, floodplain deposits are mainly composed of purple mudstones with calcretes and vegetation traces. They are interbedded with and overlain by progradational stacked (coarsening- and thickening-upward trends) crevasse channel and splay deposits with constant paleoflow directions. These floodplain deposits are finally overlain by braided stream deposits as a result of channel avulsion. In the medial zone, as the relatively high stream flood discharge caused frequent overbank flooding and formed multiple breaching points in channel levees, crevasse channel and splay deposits were compensational accumulated via these breaching points. On the other hand, in the distal zone, the relatively low stream flood discharge commonly supplied fine-grained sediments into floodplains, resulting in the deposition of purple mudstones. Once channel levees collapsed, vegetation stabilized the breaching point of channel levees, progressively incised by the multiple flooding events. Overbank floodwaters through the relatively stabilized-breaching point led to a continuous supply of coarse-grained sediments, resulting in progradational stacked crevasse channel and splay deposits. Thus, floodplain sedimentation, accumulation of crevasse channel and splay deposits, causes rapid filling of accommodation space in the proximal floodplains. With in-channel bed aggradation, their accumulation resulted in the growth of alluvial ridges and a gradual increase in the cross-floodplain topographic gradient. When the channel bed is sufficiently perched above the distal floodplains by alluvial ridge growth, the gradient advantages caused channel pathway to shift on floodplains with the formation of a new channel (channel avulsion). This study suggests that downstream changes in hydrodynamics and associated floodplain sedimentation are important for channel avulsion and thus, ultimately influence sediment dispersal patterns on the stream-dominated alluvial fans (fan-building processes).

How to cite: Lee, K. and Gihm, Y. S.: Influence of downstream changes in hydrodynamics on floodplain sedimentation and resultant channel avulsion in stream-dominated alluvial fans: An example from the Cretaceous Duwon Formation in the southern Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6881, https://doi.org/10.5194/egusphere-egu24-6881, 2024.

During the lower sub-member sedimentary period of the third member of the Shahejie Formation in the Boxing Sag, a transition from a humid to an arid climate occurred. Concurrently, the lacustrine basin experienced accelerated subsidence, leading to the development of thick-layered sand bodies caused by gravity flow. Provenance restoration plays a pivotal role in determining the location, properties, and sediment transport path of these sand bodies. This restoration was instrumental in predicting sand body distribution and holds great significance in elucidating the laws governing oil and gas accumulation.The study focused on the lower part of the third member of the Shahejie Formation in the western section of the Boxing Sag, undertaking a comprehensive investigation of sedimentary and provenance characteristics.

Core wells were observed, with 50 wells having a total core length of 2547m, and over 7000 core photos were analyzed to elucidate main facies types and sedimentary landmarks in the study area. Heavy minerals and cuttings were systematically analyzed, contributing to the restoration of the provenance system. By studying typical drilling cores and logging data, the sedimentary facies of individual wells and continuous wells were determined. A sedimentary development model was established based on sand body assemblage types and spatial distribution laws. Finally, through the integration of sand dispersion system analysis, seismic attribute technology, and paleogeomorphology, a sedimentary system plan for the study area was formulated.

The results show that the provenance area can be categorized into three types based on rock types and heavy mineral characteristics in the provenance area: the northwest source area, the western provenance area, and the southern provenance area. The northwestern, western, and southern provenance areas exhibited stable development during the study period, with heavy mineral assemblages remaining consistent on the horizontal development. Meanwhile, The turbidity fan in the study area primarily originated from the northwest provenance area, with minimal influence from the western and southern provenance areas on the cross-section. The characteristics of the lower provenance system of the third member of the Shahejie Formation in the Boxing Sag were clarified. Main sand body types and facies markers were summarized, leading to the establishment of an accurate sedimentary development model.

To sum up, this research aims to elucidate the accumulation laws of oil and gas reservoirs, providing a theoretical and data foundation for the identification and exploration of favorable areas, ultimately minimizing exploration risks.

How to cite: Yan, S. and Yang, Y.: Research on Sedimentary and Provenance Characteristics of the Lower Sub-member of the Third Member of Eocene Shahejie Formation in Boxing Sag, Dongying Depression, Bohai Bay Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7025, https://doi.org/10.5194/egusphere-egu24-7025, 2024.

The shallow water delta sand bodies within the Jurassic Shaximiao Formation in the Sichuan Basin play a crucial role in tight gas exploration. The efficient exploration of these areas is hindered by the establishment of the favorable reservoirs’ model. The Zitong area, situated on the northwest of the Sichuan Basin, is of particular interest. The Shaximiao Formation in this region can be subdivided into the first and second members, separated by dark leaf limb shale. The first member primarily features delta-lacustrine sediments, while the second member is dominated by fluvial-lacustrine sediments. In this study, we focus on the tight sandstone clastic reservoir within the Shaximiao Formation in the Zitong area.

Through core observations from four wells and a comprehensive analysis involving conventional slices, casting section, scanning electron microscopy, high-pressure mercury injection, nuclear magnetic resonance, and core plunger porosity and permeability, we explore the reservoir's development characteristics and controlling factors from both sedimentation and diagenesis perspectives.

The research reveals the following findings:

  • The reservoir components in the Zitong area are mainly composed of medium to fine-grained feldspar lithic sandstone and lithic feldspar sandstone. The primary reservoir space is intergranular pores, followed by intragranular dissolution pores. Porosity is mainly distributed in the range of 7-10%, and permeability ranges from 0.1-1.0 mD. While different subsegments exhibit varying physical properties, the overall characteristics indicate low porosity and ultra-low permeability, with the predominant reservoir type being pore type.
  • The advantage of relatively high-energy and stable sedimentary facies is crucial for high-quality reservoir formation. The underwater distributary channel in the delta front of the Shaximiao Formation serves as a favorable facies zone for high-quality reservoir development. Variations in particle size, sorting, and mud content contribute to the reservoir's properties, with the middle sandstone presenting optimal conditions for reservoir development.
  • Compaction and cementation emerge as the primary mechanisms reducing porosity. Utilizing the Ehrenberg (1989) model, calculations indicate that cementation contributes approximately 25.42% to porosity reduction, while compaction contributes 65.07%. Vertical distribution differences in zeolite and calcite contribute to variations in reservoir properties.
  • The dissolution of feldspar and the development of chlorite crust are identified as key factors in high-quality reservoir formation. Factors such as the preservation of primary pores, strong dissolution, weak cementation, and the role of chlorite thin films influence the constraints on high-quality reservoir development. The preservation of primary pores is particularly associated with the formation of chlorite thin films.

These findings contribute valuable insights into understanding and optimizing the exploration and development of tight gas reservoirs within the Shaximiao Formation in the Zitong area.

How to cite: Hu, Y. and Yang, Y.: Development characteristics and main controlling factors of tight sandstone reservoirs in the Shaximiao Formation in Zitong area, Sichuan Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7040, https://doi.org/10.5194/egusphere-egu24-7040, 2024.

  The fan delta reservoir is developed in many basins in China widely, with which internal sand body structure is complex and strong heterogeneity. It is of great significance for the development of high water cut oilfield to determine the single sand-body superposed pattern and the development characteristics of inside the single sand-body in reservoir.Taking the upper Es3 in Gangzhong Oilfield, Huanghua Depression as an example, this paper studies the reservoir architecture characteristics and heterogeneity of the fan delta front.Most of the studies on reservoir architecture of fan-delta front at home and abroad focus on identification and quantitative characterization, but the characteristics and heterogeneity of architecture units under the constraints of a Multi-level interface are not explained.In view of the above problems, the author combined core, well logging and seismic data and took sedimentary genetic model as the constraint condition to quantitatively characterize the architecture interface in hierarchical order. Through the classification of architecture levels, the characteristics of composite genetic sand body and single genetic sand body and the study of heterogeneity, the reservoir architecture and heterogeneity of the upper submember of Sha3 in Gangzhong Oilfield were revealed. It provides a powerful theoretical basis for the subsequent exploitation of oil fields.

  Specific steps include: (i) Combined with the sedimentary background of the fan delta front and the actual situation of the working area, the fine anatomy of the single genetic sand body and the composite genetic sand body is carried out by using the data of the dense well pattern, and the architecture model of the fan delta front in the study area is improved; (ii) Based on the identification marks of the architecture interface, the development characteristics of the architecture units constrained by the interface at all levels were defined, the overlapping mode inside the composite genetic sand body and the distribution characteristics of the sand body on the plane were established, and the characteristics of the single genetic sand body were described. The heterogeneity inside the architecture unit was analyzed according to the data, and finally the control effect of the reservoir heterogeneity was clarified by combining the sedimentary and tectonic processes; (iii) Through dynamic and static analysis, the remaining oil distribution model under the control of different reservoir architectures is established. The control effect of multi-stage architecture on remaining oil distribution is clarified, and the understanding of the control effect of reservoir architecture on remaining oil can provide reference for the exploitation of potential in the later stage of high water cut old oil field.

How to cite: Wei, T.: Study on reservoir architecture characteristics and heterogeneity of the fan delta front, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10444, https://doi.org/10.5194/egusphere-egu24-10444, 2024.

EGU24-11467 | PICO | SSP1.1

Reconstructing the Neapolitan volcanism prior to the 39.2 ka Campanian Ignimbrite: new stratigraphical results from a scientific drilling north of Naples (Italy) 

Sandro de Vita, Domenico Sparice, Mauro Antonio Di Vito, Ilenia Arienzo, Alessio Di Roberto, Biagio Giaccio, Angela Mormone, Lucia Pappalardo, Carlo Pelullo, Paola Petrosino, and Giuseppe Re

In the framework of the INGV–Pianeta Dinamico research theme TIFEHO (Trachytic Ignimbrites magma-chambers Formation and Evolution in the pre-HOlocene history of the Campania volcanic area), whose main goal is to understand the growth and evolution of the deep magmatic feeding system prior to high magnitude eruptions of the Neapolitan volcanic area, a deep scientific drilling has been performed, down to 113.2 m below the ground level, in the Ponti Rossi area, north of Naples (Italy). The drilling site was chosen for three main reasons: 1) it is external to any proposed Campi Flegrei (CF) caldera rim, topographic or structural scarp and downthrown area; 2) the surface geological record consists of a stratigraphic succession including several pyroclastic units sandwiched between the products of the 39.2 ka Campanian Ignimbrite (CI) eruption at the base and the 15 ka Neapolitan Yellow Tuff (NYT) eruption at the top, representing the two largest explosive events of CF, responsible for the caldera formation; 3) a 96 m deep scientific drilling, carried out in the same site in the late 1990’s, retrieved a pre-CI succession composed of eleven pyroclastic units totalling 61.8 m. Results from a detailed stratigraphic investigation, coupled with the sedimentological and geochemical characterization of a total of seventy-seven samples collected throughout the sequence, highlight that the Ponti Rossi borehole retrieved a stratigraphic record in which the NYT deposits represent the shallowest sediments. An important result is the absence of the CI deposits as well as of any pyroclastic deposit belonging to the CI-NYT (39-15 ka) chronostratigraphic interval, testifying a prolonged phase of strong erosion preceding the NYT eruption. Most of the cored succession, directly underlying the NYT deposits, consists of a thick pyroclastic sequence, totalling 88.05 m and representing the 78% of the retrieved succession, attributed to volcanism older than CI. The stratigraphic investigation and the X-Ray diffraction analysis (XRD) of the cored sediments allowed to identify at least thirty-four pyroclastic units older than CI, having thickness between 0.13 and 21.5 m, separated by well-developed paleosols and/or reworked volcaniclastic deposits. This pyroclastic succession consists predominantly of massive to stratified, matrix-supported to fines-poor pyroclastic current deposits, both magmatic and phreatomagmatic, and minor coarse- to fine-grained fall deposits. The features of several units (e.g., coarseness, lithic enrichment, considerable thickness) are compatible with a proximal vent while a number of units could be intermediate to distal tephra layers, some of which sourced from the Island of Ischia as highlighted by the available geochemical data. The retrieved stratigraphic record suggests the occurrence of a remarkable explosive activity >40 ka, the study of which will allow the achievement of a better knowledge of the magmatic systems feeding the volcanic activity of Neapolitan volcanoes.

How to cite: de Vita, S., Sparice, D., Di Vito, M. A., Arienzo, I., Di Roberto, A., Giaccio, B., Mormone, A., Pappalardo, L., Pelullo, C., Petrosino, P., and Re, G.: Reconstructing the Neapolitan volcanism prior to the 39.2 ka Campanian Ignimbrite: new stratigraphical results from a scientific drilling north of Naples (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11467, https://doi.org/10.5194/egusphere-egu24-11467, 2024.

Quartzose sandstone dominates the Upper Cretaceous sedimentary succession of the Barmer Basin, but its source of sediments is mostly hypothetical. This study elaborates the modal analysis of sandstone, EPMA mineral chemistry of detrital tourmaline and rutile and U-Th-total Pb monazite geochronology within the Fatehgarh Formation to track the possible source rocks. The poorly studied, fluvial- to marine-originated, Upper Cretaceous, roughly 125 m thick, locally cross-stratified formation crops out nearby the Barmer town, Rajasthan. The formation contains mainly sandstone, shale, claystone, conglomerate and evaporite beds forming nonconformity with Lathi Formation/Precambrian Malani Igneous Suites. The Fatehgarh Formation is medium- to coarse-grained, subangular to rounded grains, and moderately to well sorted. The sandstones are cemented by the silica, calcite and iron oxide cement. The QFR modal analysis classified quartzose sandstone and implies craton interior and recycled orogeny provenance for the sandstone. The presence of derital quartz overgrowth and rounded zircon, rutile and tourmaline suggest sediment recycling in the formation. The heavy mineral assemblage of the formation includes primarily tourmaline, zircon, and rutile with leucoxene, Fe-Ti minerals, staurolite, monazite, andalusite and opaque mineral. The EPMA analysis of the tourmaline reveals schorl and dravite varieties of tourmaline. The tourmaline composition Ca-Fe-Mg plot within the fields of ‘Li-poor granites and Ca-poor metapelites and metapsammites’. The tourmaline suggests their derivation from the Paleoproterozoic Pb-Zn deposits of Rajpura-Dariba, Zawarmala, Rampura-Agucha and Mangalwar Complex in the Aravalli-Delhi Fold Belt, and leucogranites of Sewariya-Govindgarh and Balda-Motiya of Delhi Supergroup. The rutile mineral chemistry shows ‘metapelitic origin’ of the majority of rutile grains for the basin. The presence of staurolite and andalusite mineral supports metamorphic source contribution for the sediments. The U-Th-total Pb dating of monazite grains shows major peaks at 950 Ma and 500 Ma. The monazite geochronology corroborates Pan-African and Delhi orogeny- related sediments for the Barmer Basin. The formation shows SW paleocurrent direction. The petrography, mineral chemistry and geochronology indicates the possible source of the sediments from the Marwar Supergroup, Malani Igneous Suites, and Aravalli-Delhi Fold Belts.

How to cite: Rajak, P. K., Banerjee, S., and Prabhakar, N.: Geochemical and petrographic study helps to understand the source of Upper Cretaceous Fatehgarh Formation, Barmer Basin, Rajasthan, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11591, https://doi.org/10.5194/egusphere-egu24-11591, 2024.

EGU24-12165 | ECS | PICO | SSP1.1

Deciphering local from global signals in Portimão Bank sedimentary dynamics  

Mélinda Martins, Gemma Ercilla, Teresa Drago, and Cristina Veiga-Pires

Paleoenvironmental studies play a pivotal role in addressing contemporary environmental challenges, enhancing our understanding of Earth's history, and informing climate change preparedness strategies. The PC06 sediment core, retrieved at the base of the Portimão Bank (PB) at a depth of 3,520 meters, southwest of the Gulf of Cadiz, specifically provides a valuable contribution spanning 49,000 cal. years BP to the present. This is a multidisciplinary study including sedimentological (grain size, carbonates, organic matter, smear slides and sand fraction composition) and geochemical analyses (based on XRF data) to elucidate the paleoenvironmental changes and related depositional processes over that time. Based on the obtained results four main sedimentary units with distinct lithofacies characterize the stratigraphy of the core; from bottom to top, they are as follows: A- Pyritic mud, B- Pyritic organic-rich mud, C- Clay-rich mud, and D- Pelagic mud. These sedimentary units show a transition from terrigenous mud deposition (A to C) to biogenic sedimentation (unit D) during the Holocene. The units A to C are marked by significant silt peaks and high D50 values, which suggests the influence of bottom currents from the deep waters of the North Atlantic, particularly during the Heinrich events (HE) 5 and 1, while unit D is characterize by a high percentage of planktonic foraminifera and coccolithophorids. Furthermore, units A to C are slightly coarser than unit D. Those observations could be interpreted as variations in the environmental changes at two different temporal scales: i) from the glacial (A to C) to interglacial (D) periods; and ii) a short-scale local variations during the A to C unit sedimentation related to the presence of pyrite. This multidisciplinary analysis yields valuable insights into the interaction of local and global signals, refining our understanding of Portimão Bank sedimentary dynamics throughout the studied period.

 

This work is a contribution of the MONTERA (CTM 2009-14157-C02 CSIC), EDUCOAST (PT-INNOVATION-067) and EMSO-PT (PINFRA/22157/2016) projects.

How to cite: Martins, M., Ercilla, G., Drago, T., and Veiga-Pires, C.: Deciphering local from global signals in Portimão Bank sedimentary dynamics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12165, https://doi.org/10.5194/egusphere-egu24-12165, 2024.

EGU24-12875 | PICO | SSP1.1

Improving the territorial awareness through paleontological heritage: preliminary results from Pietraroja site (southern Italy) 

Filomena Ornella Amore, Carmen Argenio, Mauro Antonio Di Vito, Romano Fistola, Mattia Yuri Messina, Adolfo Panarello, Andrea Rastelli, Ida Zingariello, and Rosa Anna La Rocca

This study is part of a larger research project (INSITE) - PRIN 2022 founded by MUR – Ministero dell’Università e della Ricerca. It is focused on two pilot sites to highlight the intrinsic potentialities of the paleontological heritage as a tool for valorising territorial resources, particularly referring to inner areas. These sites, Pietraroja (PTJ) and Le Ciampate del Diavolo (LCD), are areas of great paleontological importance, in the Campania region. The PTJ (Benevento) is the place where the fossil of a small dinosaur, Scypionix samniticus named CIRO, was found. The LCD ichnosite (Caserta) preserves elements that allow behavioural and structural evaluations of hominins of the middle Pleistocene. The main intention of the study refers to the attempt to broaden the spectrum of interest around these sites, suggesting mainstreaming the potentialities of the whole territorial context in which these sites are located. To identify innovative communication modalities and to develop a new knowledge model, we present here the reconstruction of Pietraroja paleoenvironment using technological tools. Using immersive technologies for virtual, augmented, and mixed-reality models, it is possible to build an immersive digital space in which the visitor will perceive the original environment and interact with the fossils' virtual avatar. The CIRO digital model was obtained based on complete information on the anatomical structure of Scipionyx samniticus and, through accurate 3D modeling, the digital model of the dinosaur was generated. The same approach was used to recreate the landscape and the marine and vegetation species.

How to cite: Amore, F. O., Argenio, C., Di Vito, M. A., Fistola, R., Messina, M. Y., Panarello, A., Rastelli, A., Zingariello, I., and La Rocca, R. A.: Improving the territorial awareness through paleontological heritage: preliminary results from Pietraroja site (southern Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12875, https://doi.org/10.5194/egusphere-egu24-12875, 2024.

EGU24-13015 | PICO | SSP1.1

Multi-proxy analysis for deciphering the Holocene record and mass transport processes at the Dor Disturbance in the Southeastern Mediterranean continental slope 

Revital Bookman, Yael Harmon, Yizhaq Makovsky, Mor Kanari, Elisabetta Boaretto, Ed Garrett, and Simona Avnaim-Katav

Sedimentary records from passive continental margins can be used to reconstruct regional climate–ocean trends while identifying mass transport deposits (MTD) and elucidating their characteristics and timing in relation to regional paleoclimate and paleoseismicity. This study used two radiocarbon-dated piston cores from the Southeastern Mediterranean continental slope that cover the Holocene period. The cores were collected from the shelf edge (122 m depth) and the mid slope (588 m depth) to the north east of the Nile Delta at the Dor Disturbance off-shore Israel.

Computed Tomography (CT) scanning showed the sedimentary record evolved along the Holocene representing a gradual change in the sediment grain size and composition, while detecting units of MTD. The base of the cores was dated to 10-11 ka BP, and the shelf edge core captured the transgression on the continental shelf. The Early Holocene sediments are characterized by coarser grain size, higher content of biogenic material and highest foraminiferal abundances that reflect stable and favorable environmental conditions. Sapropel S1 is recorded as the lowest Ti/Al and the highest Si/Al values and TOC content that indicate higher precipitation in the source region and the high discharge of Nile. The disappearance of benthic foraminifera in the slope core point to the development of bottom water anoxia. During the time interval of sapropel formation, a clear interruption is observed by a decrease in TOC and a moderate presence of benthic foraminifera indicating re-oxygenation of the see-floor in corresponds with the ~8.2 ka BP cold event. Towards the mid Holocene the Ti/Al ratio and Fe contend increase in association with the increase of weathering rates in the Ethiopian Highlands at the Nile watershed as a result of reduced rainfall, and thus reduced vegetation cover. This trend aligns well and correlates with the many studies documenting a middle to late Holocene orbital change that led to the decrease of solar insolation forcing southward migration of the summer ITCZ and a gradual decrease of monsoon precipitation making this region increasingly arid.

In the slope core, four units were identified in the CT scanning as relatively higher bulk density sediments, which is consistent with enhanced consolidation and reduction in porosity, observed in MTDs. Older and out of stratigraphical order radiocarbon ages within these MTD units point to deposition of recycled sediments. Interestingly, the Ca/Fe ratios showed prominent peaks and distinct changes are observed in the benthic foraminifera community including the total number of individuals per gram dry sediment (BF/g), species richness, dominance, and species composition. Furthermore, within all the MTD units a noticeable increase in broken BF shells is also detected. It is noteworthy that the abundances of the opportunistic benthic species stay moderately high in between MTD events, probably reflecting the instability of the benthic habitat.

How to cite: Bookman, R., Harmon, Y., Makovsky, Y., Kanari, M., Boaretto, E., Garrett, E., and Avnaim-Katav, S.: Multi-proxy analysis for deciphering the Holocene record and mass transport processes at the Dor Disturbance in the Southeastern Mediterranean continental slope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13015, https://doi.org/10.5194/egusphere-egu24-13015, 2024.

EGU24-14129 | ECS | PICO | SSP1.1

Simple parasequences in a medial shelf setting: Albian Sikanni Formation, Northwest Territories, Canada 

Angelina A. Abi Daoud and Janok P. Bhattacharya

We document medial shelf parasequences in the Upper Albian Sikanni Formation in the Liard Basin, Northwest Territories, Canada, deposited during a greenhouse climate in the Western Interior Cretaceous Seaway. It is characterised as a fine-grained glauconitic sandstone with argillaceous shales, ranging approximately 100 to 300 metres in thickness. We measured 111 metres of section, passing from sandier to more distal shale facies towards the contact with the conformably overlying Sully shale, indicating an overall deepening. The sandier section shows well-organised upward coarsening facies successions, transitioning from wave to hummocky cross stratified sandstones to pervasively bioturbated sandstones, dominated by Zoophycos to distal Cruziana ichnofacies, interpreted as a medial shelf environment. There are at least 8 well-expressed parasequences in the sandier lower part of the section, transitioning into more uniform shalier units near the contact of the Sully Formation. The sandier parasequences are sharply bounded by shales forming well-expressed ‘simple parasequences’. Simple parasequences are defined as upward-coarsening facies successions lacking evidence of key bounding surfaces indicating bypass or subaerial exposure, such as lag deposits, roots, or transgressive erosion. These are distinguished from ‘complex parasequences’, commonly containing these features. The changing environment of the more uniform muddier facies can be distinguished using increases and decreases in bioturbation, corresponding to lower and higher sedimentation rates, respectively. The Sikanni units lack evidence of subaerial exposure, indicating that it is unlikely the parasequences shallowed up to the shoreline. Nevertheless, these cycles are well-expressed, suggesting that simple parasequences can be identified in medial shelf environments. Additionally, a guiding framework based on Dene (First Nations) principles was developed as a basis for this project. The phases on the framework are: (1) Decolonisation of the Self, (2) Building Relationships and Community Consultation, (3) Community Entry and Data Collection, (4) Data Analysis, and (5) Knowledge Translation and Dissemination. A special thanks to Acho Dene Koe First Nation in the community of Acho Dene Koe, Northwest Territories, for graciously welcoming us onto their lands, into their community, and allowing us to share the geologic stories of the rocks they have coexisted with since time immemorial.

How to cite: Abi Daoud, A. A. and Bhattacharya, J. P.: Simple parasequences in a medial shelf setting: Albian Sikanni Formation, Northwest Territories, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14129, https://doi.org/10.5194/egusphere-egu24-14129, 2024.

The formation of extensive dolomite across ancient carbonate platform is widely attributed to the replacement of the calcium-carbonate so-called dolomitization. However, it is still unclear whether the extensive dolomite formation is controlled by one single or multiple mechanisms, as whether the mineralogical, petrological, and geochemical records of dolomite preserve the pristine signature or diagenetic effect is still under debate. In this study, we integrate carbon, oxygen, strontium and magnesium isotopes to provide new insights into ancient dolomite origin interpretation. 
Dolomite in the Upper Jurassic Arab Formation on the Arabian Plate has widely been studied due to the complete carbonate-evaporite cycle and relevance to oil reservoirs. Sabkha and seepage reflux dolomitization models have been proposed despite the high temperatures inferred from clumped isotopes and fluid inclusions, as well as some geochemical data such as oxygen and strontium isotopes, are inconsistent with near-surface dolomitization conditions. Here we performed integrated isotope study of the Upper Jurassic Arab Formation, and found that (1) Mg isotope data range from -2.25 ‰ to -1.78 ‰, suggesting the Mg cations for Arab dolomite formation were delivered from Late Jurassic seawater, which is consistent with the idea that dolomite is a valid archive of seawater Mg isotope composition through geological times; (2) in each cycle, more depleted Mg isotope signatures in dolomite formed at shallower depth than that formed at deeper depth, indicating top-down dolomitization process which is controlled by percolation of dense and saline fluids, suggesting the advective flow model and related seepage reflux dolomitization; (3) parts of Sr isotopic ratios are out of Late Jurassic seawater range, revealing hydrothermal or burial dolomitization probably altered the dolomite formed from near-surface conditions, which can also be verified by depleted oxygen isotopic values. This study indicates that ancient carbonate platform with massive dolomite distribution are probably generated by multi-mechanism dolomitization processes and it is necessary to integrate Mg isotope with traditional isotope methods to unravel the dolomite problem.

How to cite: Jia, X., Li, W., Xia, Z., and Alsuwaidi, M.: Geochemical fingerprints of dolomitization in Upper Jurassic Arabian carbonate platform: Evidence from carbon, oxygen, strontium and magnesium isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14160, https://doi.org/10.5194/egusphere-egu24-14160, 2024.

Tidal-dominated estuaries are a type of depositional system that is highly dynamic under the influence of tides. The interaction intensity between fluvial, tidal, and wave currents varies vertically along the coastline, resulting in a unique pattern of longitudinal gradient changes of facies associations and sediment distribution. Compared to river and delta sediments, research on ancient estuarine sediments is relatively limited. In this study, we analyzed observable data from the Late Cretaceous M1 Sandstone formation in the central northern region of the Oriente Basin, conducted in-depth research on its sedimentary characteristics, and proposed a tidal-dominated estuarine sedimentary model of this region. The rich core data provides reliable support for identifying sedimentary sequences of tidal environments, identifying a total of 14 lithofacies and 6 main types of facies associations, including tidal sand bars, tidal channels, and four types of tidal flats. These 6 types of facies associations correspond to the sediment accumulation characteristics in different sedimentary zones of the estuary, reflecting the differences in hydrodynamic conditions during the sedimentation process, such as strength, combination, and directionality. Furthermore, under the constraint of a dense well network, a detailed study of the stratigraphic pattern and deposit thickness was conducted to establish a matching relationship between sediment distribution characteristics and hydrodynamic characteristics in the entire region, providing sedimentary evidence for identifying tidal-dominated estuaries. Additionally, based on the combination relationships of tidal sequences, it was determined that there is a set of short-term sea level rise-fall cycles during episodic marine transgressions. The facies change of estuaries is sensitive to the response of sea level fluctuations. The results indicate that tidal sand bars are generally developed at the bottom of the tidal sequence. As the sea level decreases, the outer area is gradually covered by the tidal flat, of which the periodicity of the interior is clearer than that of tidal sand bars. Our research indicates a transition process from estuaries to deltas in the tidal system of M1 Sandstone formation under the influence of sea level fluctuations. The results provide evidence for a better understanding of the evolution of estuarine sediments in ancient strata.

How to cite: Zhu, S., Sun, P., and Xu, H.: Paleogeographic reconstruction and sedimentary evolution of tidal-dominated estuarine depositional systems: Insights from ancient deposit records of the Oriente Basin M1 Sandstone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14770, https://doi.org/10.5194/egusphere-egu24-14770, 2024.

EGU24-15199 | ECS | PICO | SSP1.1

Maximum depositional age and provenance of the Cretaceous Icheonri Formation in southeast Korea using detrital zircon U-Pb dating 

Ga-yeon Kim, Yong-Un Chae, Young Ji Joo, Taejin Choi, and Hyoun Soo Lim

The Gyeongsang Basin, Korea, is a non-marine sedimentary basin formed in an active continental margin setting by the subduction of proto-Pacific plates beneath the East Asian continent during Early Cretaceous time. The basin fill is divided into four Goups based on volcanism and plutonism. They are the Sindong (no volcanic materials), Hayang (some volcanic materials), Yucheon (mostly volcanic materials), and Bulguksa intrusive Groups. Since siliciclastic sediments were dominant in the early stages of basin evolution, it was relatively easy to classify the relative ages of strata through lithostratigraphy. However, the chronostratigraphic correlation of the Yucheon sediments is very difficult due to the intermittent development of siliciclastic deposits compared to volcaniclastics by increased volcanic activity. The Icheonri Formation, belonging to the Yucheon Group, is very difficult to correlate chronostratigraphy with other strata. Additionally, radiolarian-bearing chert pebbles, whose source rocks have not been reported in Korea, were recently found in the Icheonri Formation, raising interest in their provenance. Therefore, LA-MS-ICP-MS detrital zircon U-Pb dating was performed on two sandstone samples to constrain the maximum deposition age of the formation and obtain information about their provenance. Both samples showed a relatively wide age range, from the Precambrian to the Cretaceous. Among them, the weighted mean 206Pb/238U ages of the youngest age clusters were calculated to be 99.76±0.58 Ma (n=10, MSWD=1.5) and 99.86±0.38 Ma (n=25, MSWD=1.5), respectively. These ages correspond to the early Cenomanian in geological time scale. The presence of radiorarian-bearing chert pebbles and significant concentrations of Permian zircons in the Icheonri Formation raises the likelihood that some of the sediments that comprise the formation are from SW Japan. This study provides important evidence indicating that before the opening of the East Sea, the Korean Peninsula and Japan were closer together than they are now. The temporal and spatial variations of the origin and supply processes from the source to the sink, however, still require more investigation.

How to cite: Kim, G., Chae, Y.-U., Joo, Y. J., Choi, T., and Lim, H. S.: Maximum depositional age and provenance of the Cretaceous Icheonri Formation in southeast Korea using detrital zircon U-Pb dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15199, https://doi.org/10.5194/egusphere-egu24-15199, 2024.

EGU24-17714 | ECS | PICO | SSP1.1

Neogene – Quaternary evolution of the northeastern Fram gateway, European Arctic – preliminary results 

Orlando Martinez, Tom Arne Rydningen, Jan Sverre Laberg, Amando P.E Lasabuda, Andreia Plaza-Faverola, and Monica Winsborrow

An important geological event in the Cenozoic evolution of the European Arctic was the onset of the Fram Strait’s opening through the separation of Eurasia and Greenland along the Molloy Fracture Zone. This event facilitated the inclusion of the Arctic Ocean in the global ocean circulation, resulting in an influx of warm water and the subsequent transport of heat and moisture to the north. To study the Neogene – Quaternary nature of this inflow of water into the Arctic Ocean and its paleoclimatic implications, we have developed a seismic stratigraphic framework by combining all available 2D multi-channel seismic surveys with the chronostratigraphy (<5.8 Ma) from ODP sites 910, 911 and 912 located at the southern Yermak Plateau. Preliminary interpretations focus on the understanding of sedimentary processes of this period, particularly the interplay between along- and downslope processes of the northern Svalbard continental margin including the Yermak Plateau. The Yermak Plateau has been draped by contourite drifts that began depositing before ~5.8 Ma, indicating an active current system prior to the Pliocene. The flow direction into the Arctic Ocean was influenced by basement heights, primarily having a southeast to northwest orientation, resulting in a complex, southwest to northeast contourite drift migration pattern. Seismic facies analysis also permitted to the identification of at least two seismic units separated by the ~2.78 Ma seismic marker, interpreted to have been associated with offshore sediment progradation following the onset of glaciations in Svalbard.

How to cite: Martinez, O., Rydningen, T. A., Laberg, J. S., Lasabuda, A. P. E., Plaza-Faverola, A., and Winsborrow, M.: Neogene – Quaternary evolution of the northeastern Fram gateway, European Arctic – preliminary results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17714, https://doi.org/10.5194/egusphere-egu24-17714, 2024.

The Late Miocene – Pliocene is a time of significant environmental changes in western Eurasia. The intensified mountain building process between the Eurasian, African and Arabian plates restructured the regional landscapes, basins, and biotic record. It has resulted in dramatic palaeoenvironmental events, like the Messinian salinity crisis (MSC) in the Mediterranean, the shrinking of the Eastern Paratethys and the formation of present-day basins and highlands. During such prominent tectonic vents, the shift in climate contributed to formation of climatic barriers and/or corridors for the faunistic interchanges. Nevertheless, the role of tectonics the evolution of the past biotic record has been poorly studied. The Middle East as a region is considered a key paleobiogeographic tying point between Europe, Asia, and Africa and, thus, has played a vital role in the intercontinental dispersal of vertebrate communities. The present study focuses on the newly discovered late Miocene vertebrate site Tazhga in the NW Zagros belt, Kurdistan Region of Iraq. The fossiliferous horizon is enclosed in bioturbated floodplain deposits that belong to the upper Miocene fluvial deposits of the Zagros foreland Basin. This new vertebrate fauna will enable constraining the age of the deposits and shed light on the effect of tectonics on biogeography. We will compare the newly discovered fauna with local and more extensive regional scale fossil records in the Middle East to provide palaeobiogeographical information on the evolution of vertebrate communities of the region. Such data will enable us to clarify the role of the Arabia-Eurasia convergence during the late Miocene – Pliocene on both regional evolution of the biotic record and the intercontinental dispersals.

How to cite: Vasilyan, D., Koshnaw, R., and Ameen, F.: Tectonic and climatic controls on the vertebrate evolution in the Middle East: insights from a new late Miocene terrestrial vertebrate fauna from the NW Zagros foreland Basin in the Kurdistan Region of Iraq, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19039, https://doi.org/10.5194/egusphere-egu24-19039, 2024.

EGU24-22096 | PICO | SSP1.1

 Long-term Effects of Coastal Protection Measures on Sedimentology in a Dynamic Tidal Inlet: Spiekeroog, East Frisian Islands 

Anna-Lena Geßner, Jochen Wollschläger, Helge Ansgar Giebel, and Thomas Badewien
Coastal erosion and flood protection are significant global challenges and will become more important in the future. Hard coastal protection structures, such as groynes are implemented in high-risk areas to provide immediate results. However, their specific impacts on current dynamics and sediment properties, especially in tidal inlets, are inadequately understood. This study investigates the long-term effects of coastal protection measures on sedimentology and morphology, focusing on a tidal inlet in the East Frisian Islands, Northern Germany.
The erosive eastward littoral drift on the Southern North Sea coast sets an ideal backdrop. To protect the East-Frisian islands from storm surges groynes were built. A groyne on Wangerooge Island restricts the North Sea - Wadden Sea exchange, hypothesized to alter flow dynamics and sediment transport within the inlet “Harle”. Sedimentological analysis, including grain size and component analysis, reveals seven distinct sedimentological facies. Integrated multibeam data creates a facies map indicating higher grain size in main channels and the formation of a sandbar segregating the main tidal channels in the Harle. Erosion and deposition areas highlight altered current patterns, including circulation eddies and mixing shear zones.
Comparisons with an almost unaffected tidal inlet between the islands of Langeoog and Spiekeroog emphasize the enduring impacts of the coastal protection measures on sedimentology in the "Harle". This study illuminates the complex interplay between coastal protection and sedimentology in a high-dynamic tidal inlet system, providing insights coastal management amid global challenges.

 

How to cite: Geßner, A.-L., Wollschläger, J., Giebel, H. A., and Badewien, T.:  Long-term Effects of Coastal Protection Measures on Sedimentology in a Dynamic Tidal Inlet: Spiekeroog, East Frisian Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22096, https://doi.org/10.5194/egusphere-egu24-22096, 2024.

EGU24-2596 | ECS | Orals | SSP1.2

Large-scale carbon release from multiple sources caused an Early Jurassic hyperthermal event 

Wenhan Chen, David Kemp, Ying Cui, and Chao Li

The Toarcian Oceanic Anoxic Event (T-OAE, ~183 Ma) was one of the most significant hyperthermal events in the Phanerozoic, characterized by a series of climatic and environmental perturbations on land and in the oceans. The climate warming was accompanied by an abrupt negative carbon-isotope excursion (N-CIE) in the biospheric carbon reservoir, suggesting the driver of this event was the massive release of 12C-enriched carbon. However, the source, rate, and cumulative mass of carbon emitted during the T-OAE are poorly constrained, leaving the specific mechanisms of climate change uncertain. Here, we simultaneously assimilate atmospheric pCO2 reconstructions and carbon-isotope data from 24 well-constrained T-OAE profiles in an Earth system model to quantify carbon emission masses, rates, and sources. Our simulations suggest the emission of 10,900 Pg C across the event at rates of up to 0.8 Pg C yr-1. A clear pulse of extremely 12C-enriched carbon release occurred at the onset of the T-OAE, likely indicative of a biogenic (e.g., methane hydrate) source. This was followed by the release of carbon consistent with a magmatic source, with two transient pulses potentially indicative of thermogenic carbon emission superimposed on a protracted input of volcanic carbon. The complex pattern of carbon release revealed by our modeling emphasizes the interplay of both deep and surficial Earth processes in driving the T-OAE event. Negative carbon fluxes characterize the N-CIE recovery phase, underlining the crucial roles of enhanced continental weathering and massive burial of organic carbon in facilitating Earth system recovery from massive warming.

How to cite: Chen, W., Kemp, D., Cui, Y., and Li, C.: Large-scale carbon release from multiple sources caused an Early Jurassic hyperthermal event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2596, https://doi.org/10.5194/egusphere-egu24-2596, 2024.

EGU24-3736 | Orals | SSP1.2

Benthic foraminiferal morphogroups track the recovery of the deep-marine ecosystem after the K/Pg boundary 

Michael Kaminski, Syouma Hikmahtiar, and Claudia Cetean

Morphogroup analysis of benthic foraminifera is a useful tool that reflects the nature of the trophic continuum, and in particular the flux of organic matter to the sea floor and its source. In broad terms, agglutinated benthic foraminifera can be placed in four morphotypes based on their test morphology and feeding preference. Morphotype M1 constitutes tubular suspension feeders that trap food particles carried in suspension. Morphotypes M2 and M3 are the coiled multichambered forms, which are epifaunal detritivores, and M4 is the group of elongated and rectilinear infaunal deposit feeders. Their relative proportions tell us something about flux of particulate organic carbon (POM) to the sea floor and its mode of delivery, which is ultimately a function of water depth, currents, and the amount of surface-water phytoplankton production.

To assess the trophic structure of the benthic foraminiferal community across the Cretaceous/Paleogene boundary in the western Tethys, we examined >70 samples from the Scaglia Rossa Formation in Gubbio, Italy. Samples were mostly collected at 10 cm spacing. We also recalibrated the age model for the Scaglia Rossa Formation in Gubbio using the 2020 geologic time scale. In the top two meters of the Maastrichtian, a gradual increase in the proportion of M4 is observed (to ca. 20%) leading up to the K/Pg boundary. These values fall abruptly to 7% in the beds immediately above the boundary clay, with more variable values in the lower Paleocene. This pattern can be interpreted as reflecting a modest but short-lived reduction in the total sea-floor organic flux following the boundary event (but not a “Strangelove Ocean”). Morphotype M1 shows a major reduction above the boundary, and there is a concurrent increase in the M2 morphotype. This implies a reduction in the amount of POM arriving at the sea floor from suspension. The increase in M2 suggests that there was greater influence of organic matter from bacterial sources in the early Paleocene.

The recovery of the deep-marine ecosystem was prolonged, with M1 returning to Maastrichtian values approximately 3.4 m above the K/Pg boundary clay. Using our new age model, this is equivalent to 1.8 m.y. after the event. Our findings of a prolonged recovery are in line with the conclusions of nannofossil workers, who estimated that it took approximately 2 m.y. for the marine food web to fully reestablish itself after the K/Pg boundary event.

How to cite: Kaminski, M., Hikmahtiar, S., and Cetean, C.: Benthic foraminiferal morphogroups track the recovery of the deep-marine ecosystem after the K/Pg boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3736, https://doi.org/10.5194/egusphere-egu24-3736, 2024.

EGU24-4010 | ECS | Orals | SSP1.2

Investigating the influence of natural and artificial thermal maturation on sedimentary mercury (Hg) 

Asri O. Indraswari, Joost Frieling, Tamsin A. Mather, Alexander J. Dickson, Erdem Idiz, Hugh C. Jenkyns, and Stuart Robinson

In recent decades, enrichment of mercury (Hg) in sedimentary deposits has been widely used as a proxy for volcanism from Large Igneous Provinces (LIPs). Mercury is naturally released into the atmosphere through volcanic exhalations and other processes, then dispersed and sequestered in sediments. Recent studies have delved into the impact of extremely high-temperature exposure on Hg in sediments, such as intrusion and contact metamorphism. However, the behaviour of sedimentary Hg exposed to more moderate warming, such as associated with thermal maturation and hydrocarbon formation in a sedimentary basin is still underexplored.

We conducted a series of artificial maturation experiments on immature organic-rich marine mudrocks, specifically the Posidonienschiefer or Posidonia Shale (Lower Jurassic) in the Lower Saxony Basin, Germany. These pyrolysis experiments enabled us to investigate the changes in Hg concentration within rock residues and evolved organic fluids across varying maturation stages.

Our findings reveal a progressive decline in Hg concentrations in sediments with increasing thermal maturity throughout the experiments (24 hours to 5 weeks at 325 ºC). Notably, the most significant Hg concentration loss occurs between the time-steps 5 days and 15 days. However, the substantial Hg loss from the pyrolysis experiments strongly differs from observations from naturally matured Posidonia Shale. In contrast to the slight decrease observed in the pyrolysis experiments, we recorded a trend of increasing Hg concentrations associated with higher maturity on three Posidonia Shale cores., We explore the mechanisms for these striking differences between the experimental and natural maturation and how these effects may have controlled Hg mobility during hydrocarbon formation and impacted the use of sedimentary Hg as a proxy for LIP-related volcanism.

How to cite: Indraswari, A. O., Frieling, J., Mather, T. A., Dickson, A. J., Idiz, E., Jenkyns, H. C., and Robinson, S.: Investigating the influence of natural and artificial thermal maturation on sedimentary mercury (Hg), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4010, https://doi.org/10.5194/egusphere-egu24-4010, 2024.

EGU24-4627 | ECS | Posters on site | SSP1.2

Redox- and bio-productivity changes in the Trans-Saharan epicontinental seaway during and after the Cenomanian-Turonian anoxic event (OAE2): insights from stable isotopes and trace metals 

Usman Abubakar, Simon V. Hohl, Sebastian Viehmann, Stefan Weyer, and Musa Bappah Usman

Redox- and bio-productivity changes in the Trans-Saharan epicontinental seaway during and after the Cenomanian-Turonian anoxic event (OAE2): insights from stable isotopes and trace metals

Usman Abubakar 1,2*, Simon V. Hohl1, Sebastian Viehmann3, Stefan Weyer3, Musa Bappah Usman2

1State Key Laboratory of Marine Geology, Tongji University, Shanghai, P.R China

2Department of Geology, Gombe State University, Gombe, Nigeria

3Department of Mineralogy, Leibniz University Hannover, Hannover, Germany

*uabubakar2002@tongji.edu.cn

The Cenomanian-Turonian boundary (~ 94 Ma) marked a presumably global ocean anoxic event (OAE2), resulting in the widespread deposition of black shales, a positive carbon isotope excursion, biotic turnover, and significant changes in global climate. While increased volcanic activity is often linked to enhanced nutrient supply into the ocean and increasing primary productivity and O2 consumption during their decomposition, recent studies have revealed contradictory redox conditions ranging from anoxic to oxic from the open ocean to epicontinental seas. We present the first integrated geochemical data from the Ashaka quarry in one of the basins flooded by the Trans-Saharan epicontinental seaway: the Upper Benue Trough, Nigeria. The data include δ13Corg and δ238U, total organic carbon (TOC), and redox-sensitive and bio-essential trace metal concentrations. We aim to determine the possible location of OAE2 within this strata and reconstruct local variations in redox and bio-productivity systematics. δ13Corg displays a positive excursion of ~2 ‰ (-25.5 ‰ to -23.5 ‰) at the base of the section, indicating the occurrence of an OAE. However, this event coincides with relatively low TOC values (0.3-1.2 wt.%), showing regionally low burial rates at a potentially increasing influx of terrigenous organic matter, as evidenced by increasing C/N ratios from 4.4 to 10.3. Enrichment factors of redox-sensitive trace metals (UEF and MoEF) exhibit depletion, enrichment, and subsequent depletion at the beginning, middle, and end of the OAE2 within the stratigraphy, respectively. In contrast, enrichment factors of bio-essential trace metals (CdEF and ZnEF) consistently show a depletion throughout the event and display a low ratio of micronutrients to macronutrients (Cd/P and Zn/P). These patterns correspond with δ238U (-0.46 to -0.32 ‰) varying around the value of modern seawater (-0.4 ‰), suggesting fluctuations from oxic to sub-oxic redox conditions and a reduced element shuttle at possibly suppressed paleo-productivity. After the OAE2, the middle part of the Ashaka section records primarily oxic conditions supported by very low TOC and δ238U values similar to the modern ocean. The top of the section exhibits highly depleted redox-sensitive metals and high enrichment of bio-essential metals, indicating a rebound to fully open marine conditions characterized by high productivity, upwelling, and well-oxygenation concurrent with a slight positive shift in δ238U (-0.37 to -0.29).

This study demonstrates partly oxygenated conditions during the OAE2 in the epicontinental Trans-Sahara Seaway, correlating the Ashaka quarry section with strata deposited in the epicontinental Western Interior Seaway and several shallow marine environments of the Tethys Sea, bringing this new OAE2 interval into the global context for the first time.

How to cite: Abubakar, U., V. Hohl, S., Viehmann, S., Weyer, S., and Bappah Usman, M.: Redox- and bio-productivity changes in the Trans-Saharan epicontinental seaway during and after the Cenomanian-Turonian anoxic event (OAE2): insights from stable isotopes and trace metals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4627, https://doi.org/10.5194/egusphere-egu24-4627, 2024.

The Jenkyns Event (i.e. the early Toarcian Oceanic Anoxic event, ca. 183 Ma) represents a notable short-term environmental and climatic perturbations. It is hypothesized to have originated from a substantial release of 13C-depleted carbon into the global ocean-atmosphere system, culminating in a globally synchronized negative carbon isotope excursion (N-CIEs). While this event has been extensively studied within the Tethyan Ocean, it remains inadequately characterized in continental domains beyond Europe. Here, lower Toarcian lacustrine successions from the QZ-16 well in the Qiangtang Basin, situated along the northern passive continental margin of the Meso-Tethys Ocean, is studied based on a multi-proxy approach of  organic and inorganic and isotope geochemistry, mineralogy, sedimentology, and palynology.

Chronostratigraphic calibration of the successions within the Quemo Co Formation is achieved through carbon isotope (δ13Corg and δ13Ccarb) records and palynostratigraphy. Notably, a long-term positive δ13C trend is identified, which is interrupted by pronounced 4–5‰ N-CIEs in δ13Corg and δ13Ccarb during the early Toarcian. This perturbation is interpreted as the terrestrial counterpart of the marine Jenkyns Event within the Qiangtang Basin, reinforcing a synchronicity to marine records. The Toarcian interval of the Qiangtang Basin is characterized by fully oxidizing conditions intermittent with minor phases of dysoxic settings, especially during the Jenkyns Event, resulting in a low organic carbon burial within the Quemo Co Formation.

Sedimentological analyses within the Jenkyns Event interval indicate the presence of storm deposits, as evidenced by siltstones, graded siltstones, small-scale hummocky cross-stratification, and sharp erosive bases. These features suggest a strong correlation between warming events and increased tropical storm activity during this period, leading to intensified hydrological cycles. Furthermore, elevated ratios of fluvial detrital proxies, such as Si/Al and Ti/Al, along with the deposition of silty mudstone facies at the onset of the Jenkyns Event point to enhanced terrigenous input. This can be attributed to accelerated continental weathering, coinciding with the climatic changes at this time.

Palynological analyses reveal a progressive shift from arid to humid climate conditions, consistent with the carbon-isotope perturbation, supporting the accelerated hydrological cycling during the Toarcian. However, the enhanced freshwater input, associated with the enhanced hydrological cycling, was counterbalanced by a decline in lake levels. These records were completely documented in lacustrine deposits within the Qiangtang Basin dating from the isotope perturbation, which is consistent with the early Toarcian global regression. Lacustrine deposits with marine influences suggest sporadic connectivity between the Qiangtang Basin and the Tethys Ocean during the Toarcian, underscoring a strong link between regional shoreline progradation and evolution of global climate and sea-level.

How to cite: Zhang, H. and Wang, J.: Terrestrial responses to the Jenkyns Event within a lacustrine system of the Qiangtang Basin (Tibet, China): Insights from sedimentology, palynology, and carbon-isotope geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5117, https://doi.org/10.5194/egusphere-egu24-5117, 2024.

EGU24-5694 | Orals | SSP1.2

Palynofloral change across Oceanic Anoxic Event 2 in the Iberian Basin, Spain 

Ulrich Heimhofer, Fernando Barroso-Barcenilla, Mélani Berrocal-Casero, Suping Li, Katharina Müller, and Alexander Wheeler

The Cenomanian–Turonian Oceanic Anoxic Event (OAE2; ~94.5 million years ago) represents an episode of global-scale marine anoxia and biotic turnover, which corresponds to one of the warmest time intervals in the Phanerozoic. Despite its global significance, information on the dynamics of continental ecosystems during this greenhouse episode is scarce. Here we present a terrestrial palynological record combined with chemostratigraphic data from an expanded marine OAE2 section from the Iberian Basin, Central Spain. Carbon isotope records of carbonate and organic carbon from two nearby sections show the characteristic positive CIE (carbon isotope excursion) associated with OAE2 and, together with ammonite finds, facilitate the construction of a stratigraphically well-constrained composite record. The spore-pollen assemblage is dominated by non-saccate gymnosperm (Classopollis, Araucariacites, Inaperturopollenites) and angiosperm pollen (mainly representatives of the Normapolles group incl. Atlantopollis and Complexiopollis), with pteridophyte spores being quantitatively less abundant. With stratigraphic height, the spore-pollen assemblage shows distinct changes in frequency distribution including a distinct rise in the angiosperm pollen Atlantopollis within an interval assigned to the Plenus Cold Event. In contrast, a pronounced increase in Classopollis reaching >50% of the total palynoflora parallels the 2nd peak of the CIE and is followed by an abrupt decline. These palynofloral changes indicate changing proportions of arborescent conifer forests and more open, non-arborescent, angiosperm-rich vegetation. Despite the exceptional warmth associated with OAE2, the continental hinterland bordering the Iberian seaway did support a diverse vegetation, adapted to persist under elevated temperatures. Fluctuations in spore-pollen frequency distribution are considered to reflect significant climatic changes over the course of OAE2 controlled ultimately by the interplay of large-scale magmatic activity and enhanced organic carbon burial.

How to cite: Heimhofer, U., Barroso-Barcenilla, F., Berrocal-Casero, M., Li, S., Müller, K., and Wheeler, A.: Palynofloral change across Oceanic Anoxic Event 2 in the Iberian Basin, Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5694, https://doi.org/10.5194/egusphere-egu24-5694, 2024.

EGU24-6306 | Posters on site | SSP1.2

Coupling Timing and Tempo of Deccan Volcanism with the KPg Extinction: Evidence from Mercury and Tellurium Anomalies 

Thierry Adatte, Marcel Regelous, Nils Baumann, Hassan Hassan Khozyem, Jorge E. Spangenberg, Gerta Keller, Uygar Karabeyoglu, Blair Schoene, and Syed Khadri

Mercury (Hg) and more recently tellurium (Te) are indicator of large-scale volcanism in marine sediments and provide valuable insights into relative timing between biological and environmental changes, mass extinctions and delayed recovery. Several studies evaluated the relationship between Hg anomalies in sediments and LIP activity across mass extinction horizons. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 350 ky before the Cretaceous-Tertiary (KT) mass extinction. Maximum eruption rates occurred before and after the K-Pg extinction, with one such pulse initiating tens of thousands of years prior to both the bolide impact and extinction, suggesting a cause-and-effect relationship. We present a comprehensive high-resolution analysis of Deccan Traps Hg-Te loading, climate change and end-Cretaceous (KPB) mass extinction from a transect, which includes 30 sections deposited in both shallow and deep environments located in France, Spain, Italia, Denmark, Israel and Tunisia. In all sections, our findings indicate that Hg concentrations are more than 2 orders of magnitude greater during the final 100ky of the Maastrichtian up to the early Danian P1a zone (first 380 Ky of the Paleocene). Notably, Hg anomalies generally show no correlation with clay or total organic carbon contents, suggesting that the mercury enrichments resulted from higher input of atmospheric Hg species into the marine realm, rather than being driven by organic matter scavenging and/or increased run-off. Significant and coeval Hg enrichments are observed in multiples basins characterized by proximal and distal, as well as shallow and deep-water settings, supporting a direct fallout from volcanic aerosols. Hg enrichments are not observed in the Indian redboles, confirming that it is not a proximal proxy for volcanism. But significant Hg anomalies have been found in more distal intertrapeans sediments at Anjar (Gujarat), Daiwal and Podgavan (SW Nagpur, Maharashtra). Significant Hg anomalies are also found in the more distal Megalaya section. Hg isotope data from Bidart confirm a direct Hg fallout from volcanic aerosols. Furthermore, Te/Th ratios measured in the Goniuk (Turkey), Elles (Tunisia), Gubbio (Italy) and Wadi Nukhul (Egypt) sections show the same trend as Hg/TOC and are consistent with a volcanic origin, albeit a minor extraterrestrial contribution of Hg at the boundary cannot be excluded. Hg and Te maximum loadings coincide with time of maximum Deccan emission rates and volumes determined by zircon dating. Hg and Te concentrations within sediments in conjunction with Te/Th and Hg/TOC ratios are therefore robust and useful proxies to trace intensity of volcanism.

How to cite: Adatte, T., Regelous, M., Baumann, N., Hassan Khozyem, H., Spangenberg, J. E., Keller, G., Karabeyoglu, U., Schoene, B., and Khadri, S.: Coupling Timing and Tempo of Deccan Volcanism with the KPg Extinction: Evidence from Mercury and Tellurium Anomalies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6306, https://doi.org/10.5194/egusphere-egu24-6306, 2024.

EGU24-6595 | Orals | SSP1.2

Fine silicate dust from Chicxulub crater excavation shuts down photosynthesis for up to 2 years after the K-Pg impact.  

Philippe Claeys, Cem Berk Senel, Pim Kaskes, Orkun Temel, Johan Vellekoop, Steven Goderis, Maarten A. Prins, and Ozgur Karatekin

Formation of the ± 200 km in size Chicxulub crater is widely regarded as the leading cause of the Cretaceous-Paleogene (K-Pg) boundary mass extinction, 66 million years ago. Nevertheless, the precise climatic outcome of the various debris ejected into the atmosphere following the crater excavation, thus the killing mechanisms remain not definitely understood. Present paleoclimate scenarios confer a substantial role in sulfur components released by the vaporization of evaporite layers present in the upper part of the target rock. Sedimentological constraints acquired from an expanded terrestrial K-Pg boundary deposit in North Dakota and measured volumetric size distribution of silicate dust indicate the release into the atmosphere of fine silicate dust (~0.8-8 μm). The new general circulation model simulations of the injection of such a plume of micrometer-sized silicate dust (2x1018g) suggest a long atmospheric residence time (±15 years) with a global-average surface temperature falling by as much as 15ºC. Simulated effects on the post-impact active solar radiation support a dust-induced photosynthetic shut-down for approximately 2 years. Contrary to previous work, these new paleoclimate simulations, relying on robust sedimentological field data at the K-Pg boundary revealed that the impact-generated silicate dust plume plays a pivotal role in driving the K-Pg climate and biotic crisis. The new scenarios showcase that the global darkness and prolonged loss in the planet's photosynthetic activity happen solely in the silicate dust scenario, up to nearly 1.7 years after impact; a sufficiently long timescale to pose severe challenges for terrestrial and marine habitats. Biotic groups not adapted to survive the dark, cold, and food-deprived conditions for almost two years, experienced massive extinctions. In addition, this emission scenario shows that the photosynthetic recovery to the pre-impact levels first occurred in the austral summer season, ~1.7 years after impact. This would imply a potential earlier recovery of primary productivity in the Southern Hemisphere. These new findings highlight that the photosynthetic shut-down induced by the large volume of silicate dust, together with additional effects of sulfur and soot likely led to the collapse of primary productivity in land and ocean realms, steering the global mass extinction at the K-Pg boundary.

How to cite: Claeys, P., Senel, C. B., Kaskes, P., Temel, O., Vellekoop, J., Goderis, S., Prins, M. A., and Karatekin, O.: Fine silicate dust from Chicxulub crater excavation shuts down photosynthesis for up to 2 years after the K-Pg impact. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6595, https://doi.org/10.5194/egusphere-egu24-6595, 2024.

EGU24-6915 | Orals | SSP1.2

Massive changes in marine sedimentation rates during the Carnian Pluvial Episode (Late Triassic) 

Jacopo Dal Corso, Yadong Sun, and David B. Kemp

The Carnian is marked by major environmental changes, including multiple carbon-cycle perturbations, global warming and enhanced hydrological cycling that have been linked to the effects of the emplacement of Wrangellia large igneous province. The environmental perturbations occurred in an interval of about 1–2 Myr between the Julian 2 and the base of the Tuvalian 2. This interval is named Carnian Pluvial Episode (CPE). The widespread and pronounced sedimentological changes observed in marine sedimentary records, which abruptly shift towards mainly siliciclastic deposition, point to general higher continental runoff during the CPE. However, quantification of actual changes in sediment flux to marine basins is still lacking. We calculated changes in linear and relative sedimentation rates in Carnian well age-constrained marine successions. During the Julian 2, the lithological changes are coupled to increases of up to ca. 3000% in relative sedimentation rates in the marine sequences of Western Tethys and Panthalassa, and to slight decreases (< -100%) in sedimentation rates in successions of Eastern Tethys. Sedimentation rates then decrease in the Tuvalian 1 in all the successions. The higher siliciclastic delivery to the basins is likely the result of the interplay of higher precipitation and continental runoff under conditions of higher atmospheric pCO2, eustatic sea-level changes and local depositional contraints, which could all be relatable to the effects of volcanic gases emissions from Wrangellia large igneous province.

How to cite: Dal Corso, J., Sun, Y., and Kemp, D. B.: Massive changes in marine sedimentation rates during the Carnian Pluvial Episode (Late Triassic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6915, https://doi.org/10.5194/egusphere-egu24-6915, 2024.

Oceanic Anoxic Event 1a (OAE 1a, ~120Ma) during the early Aptian represents a dramatic perturbation of the global carbon cycle and is associated to widely deposition of black shale [1]. The emplacement of the Ontong Java Plateau is considered to be the trigger of OAE 1a, which led to a series of environmental perturbations including marine anoxia [2]. However, whether Ontong Java Plateau volcanism is the direct driving factor of oceanic deoxygenation is still under debate. Most research suggested that the eruption of Ontong Java Plateau injected enormous CO2 into the atmosphere-ocean system and accelerated continental weathering, which eventually resulted in ocean anoxic/euxinic conditions [1]. Few argued that oceanic deoxygenation was an immediate response to the Ontong Java Plateau volcanism [3].

Here, we select DSDP Site 463 and ODP Site 866A in the Pacific Ocean near Ontong Java Plateau as study sections. We present high-resolution δ98Mo records to reflect changes in ocean redox conditions and use Mn and Fe abundances and Eu/Eu* ratios to resolve volcanic phases. Combined with other redox, biological productivity, and weathering proxies, we reconstruct the history of Ontong Java Plateau eruption and ocean redox environment across OAE 1a. Our data reveal that oceanic deoxygenation started before OAE 1a and was driven by Ontong Java Plateau volcanism instead of continental weathering. Volcanically sourced nutrients fluxed into the ocean and stimulated local organic productivity, resulting in ocean deoxygenation. During OAE 1a, ocean maintained anoxic/euxinic conditions. The coeval global seawater δ98Mo was probably around or greater than 2.1‰.

 

[1] Jenkyns, 2010, Geochemistry Geophysics Geosystems 11.

[2] Percival et al., 2021, Global and Planetary Change 200.

[3] Bauer et al., 2021, Geology 49, 1452-1456.

How to cite: Wu, S., Li, C., Huang, J., and Sun, W.: The influence of Ontong Java Plateau volcanism on oceanic deoxygenation during Oceanic Anoxic Event 1a: evidence from Mo isotope, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7064, https://doi.org/10.5194/egusphere-egu24-7064, 2024.

EGU24-7374 | ECS | Posters on site | SSP1.2

Onset of the Carnian Pluvial Episode: a record by clay minerals from the Misurina stratigraphic succession (Dolomites, Italy) 

Greta Alverà, Jacopo Dal Corso, Giuseppe Cruciani, Marcello Caggiati, and Piero Gianolla

The Carnian Pluvial Episode (CPE) was a climate and biological crisis that occurred in the early Late Triassic (~232–234 Ma) and has been linked to large igneous province volcanism, which would have injected large quantities of volcanic CO2 into the Carnian atmosphere and triggered global warming and a strong enhancement of the hydrological cycle. In the marine sedimentary succession of the Dolomites, the CPE is marked by a crisis of the early Carnian microbial-dominated high-relief carbonate platforms and an increase of siliciclastic deposition. To understand weathering processes related to the more humid climate that occurred at the onset of the CPE, we present organic-carbon isotope data and clay mineralogical composition of 112 fine-grained samples taken from a basinal stratigraphic series outcropping near Misurina (Auronzo di Cadore, Dolomites, Italy). The succession encompasses the topmost San Cassiano (early Carnian) and the base of the Heiligkreuz (late early Carnian) formations, corresponding to the interval recording the onset of the CPE. Overall quantitative mineralogical composition was obtained from whole-rock samples XRD analysis using Rietveld method. Analyses on oriented mounts of the <2µm fraction in air-dried, ethylene-glycol saturated, and heated form, were also performed for the accurate identification of clay minerals. The Misurina section consists mainly of argillaceous and calcareous marls where two sharp δ13CTOC excursions (CIE 1a and 1b), corresponding to the first global C-cycle perturbation of the CPE, were identified. The CIE 1b can be correlated to the negative shift previously recorded in the nearby Milieres reference section. At Misurina, the C-isotope perturbation can be divided in six phases: I) background; II) negative δ13CTOC shift 1a; III) positive rebound 1a; IV) negative δ13CTOC shift 1b; V) positive rebound 1b; VI) return to background. These C-isotope changes are linked to changes in clay mineralogy. We accurately quantified the clay mineral assemblages composed of Chlorite (0.26–4.33%), Kaolinite (0.70–14.46%), Illite (2.29–14.08%) and the major component Illite/Smectite (IS) mixed-layer (67.93–95.77%). From phase I to phase II, Kaolinite increases from average 1.52 % to 2.92 %, as well as Kaolinite/Illite ratio. Kaolinite and Kaolinite/Illite remain higher during phases III (avg 2.70 %) and IV (avg 3.26 %) with respect to background values (avg 1.52 %). A further increase in Kaolinite content (avg 5.53 %) is recorded in phase V. Phase VI records a relative increase of the siliciclastic component and a parallel relative increase of Chlorite, Kaolinite and Illite with respect to IS. The mineralogical variations during the C-isotope phases IV, V, VI at Misurina are parallel to variations in the relative abundance of Kaolinite, Kaolinite/Illite and Quartz + Feldspars at Milieres section. An increase of Kaolinite content during phases II-V are interpreted to reflect an increase of the intensity of silicate hydrolysis on land, which is in agreement with the CPE onset model. Our high-resolution dataset shows that the onset of the CPE was marked by repeated perturbations of the C-cycle and an increase of the chemical weathering as observed in other marine and terrestrial settings within the same stratigraphic interval. 

How to cite: Alverà, G., Dal Corso, J., Cruciani, G., Caggiati, M., and Gianolla, P.: Onset of the Carnian Pluvial Episode: a record by clay minerals from the Misurina stratigraphic succession (Dolomites, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7374, https://doi.org/10.5194/egusphere-egu24-7374, 2024.

EGU24-7601 | ECS | Posters on site | SSP1.2

The Te and Hg Record of Deccan Traps and NAIP Volcanism in Late Maastrichtian – Early Eocene Sediments 

Nils Björn Baumann, Marcel Regelous, Thierry Adatte, Hassan Khozyem, Anette Regelous, and Karsten Haase

The Cretaceous-Paleogene (K-Pg; ~66 Ma) extinction and the Paleocene Eocene Thermal Maximum (PETM; ~56 Ma) were two major environmental and biotic crises in Earth’s history. While both coincide with the emplacement of Large Igneous Provinces (LIPs), uncertainties persist about the role of the Deccan Traps and the North Atlantic Igneous Province (NAIP) respectively in these events.

In both cases, the reconstruction of cause and effect of environmental perturbations is hampered by the difficulty in determining the timing of volcanism relative to environmental change and extinction. The main phase of the Deccan volcanism initiated at ~66.5 Ma in C24n and lasted for about 1 Myr, overlapping with the Chicxulub impact at ~66.03 Ma and the Cretaceous-Paleogene boundary (KPB) extinction.
In case of the NAIP, linking the eruptive history to the light carbon excursion (CIE) and rapid warming at the P-E boundary (~56.01 Ma) remains difficult, thus raising questions about the trigger for the CIE. Some studies found volcanic degassing to be sufficient to account for the CIE, in which case the main period of volcanic activity was short, and initiated at the Paleocene-Eocene boundary. Alternatively, the light carbon originates from magmatic tapping of carbon-rich sediments or destabilization of methane clathrates.

In order to tie Large Igneous Province (LIP) volcanism to consequent environmental perturbations, we present tellurium (Te), mercury (Hg) and other trace element proxies from a complete sedimentary profile at Wadi Nukhul, Egypt spanning about 12 Myr from the late Maastrichtian to the early Eocene. A peak in Te in the latest Maastrichtian corresponds to the Late Maastrichtian Warming Event, and may be coincident with early Deccan volcanism on the Malwa Plateau. Te concentrations rise again up to 467 ppb immediately before the KPB, possibly reflecting eruptions of the massive Wai Formation at the Deccan Traps. Te concentrations are close to crustal average values (~10 ppb) throughout most of the Paleocene, and another spike of 465 ppb can be recognized at Paleocene – Eocene (PE) boundary. In contrast, the Hg record for this period is less clearly influenced by volcanism. Hg/TOC ratios peak in the Late Maastrichtian and earliest Eocene, but similarly high values occur throughout the section.

Using a vast set of trace elements, we rule out changes in lithology, accessory mineral content, or changing redox and productivity conditions as controlling factors on Te concentrations. We use nannofossil zone ages to calculate sedimentation rates and elemental fluxes. We show that an increase in Te during the late Cretaceous coincides with the late Maastrichtian warming event and that the eruption of the Wai group initiated before the Chicxulub impact. Deccan volcanism likely contributed to climate instability and may have amplified the effects of bolide impact on the biotic crisis.
Furthermore, an abrupt increase in Te concentrations coinciding with the opening of the North Atlantic at the P-E boundary, suggest highest volcanic degassing concurrent with the CIE. We, therefore, conclude that atmospheric injection of volcanic CO2 may have been the major driver of the negative CIE.

How to cite: Baumann, N. B., Regelous, M., Adatte, T., Khozyem, H., Regelous, A., and Haase, K.: The Te and Hg Record of Deccan Traps and NAIP Volcanism in Late Maastrichtian – Early Eocene Sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7601, https://doi.org/10.5194/egusphere-egu24-7601, 2024.

EGU24-9283 | ECS | Posters on site | SSP1.2

Mid-Cretaceous Oceanic Anoxic Events in the outer Eastern Carpathians: biostratigraphic and chemostratigraphic events 

Vlad Apotrosoaei, Relu-Dumitru Roban, Andrei Briceag, and Mihaela Melinte-Dobrinescu

The mid-Cretaceous times are characterized by the presence of the most numerous Oceanic Anoxic Events (OAEs) in the whole Mesozoic, reflecting the occurrence of superplumes, associated with high ocean crust formation rates and increased volcanism (i.e., Larson, 1991; Jenkyns, 2010). In general, the Romanian Carpathians, and especially the Eastern Carpathian bend, enclose significant successions of a deep-water setting, deposited during mid-Cretaceous times. The investigated successions are mainly composed of black and dark-grey shales, grey marls, and sparse cm-thick radiolarites. Based on the calcareous nannofossil biostratigraphy, the studied successions cover the late Albian-Cenomanian interval, encompassing the UC0 up to UC3a biozones. Within the studied successions, the isotope δ13Corgshow several fluctuations. The oldest peak is situated in the UC0 nannofossil zone, across the Albian-Cenomanian boundary interval, starting slightly below the LO (last occurrence) of the nannofossil Hayesites albiensis. The youngest recorded peak is placed in UC3a nannofossil subzone and encloses the FO (first occurrence) of the nannofossil Lithraphidites acutus. We assume that the oldest positive excursion identified correspond to the Albian-Cenomanian Boundary Event (ACBE), while the youngest one is most probably the chemostratigraphic overprint of the MCE (mid-Cenomanian Event). Both depositional intervals that contains the ACBE and MCE are characterized by the deposition of rich-organic black shales.

How to cite: Apotrosoaei, V., Roban, R.-D., Briceag, A., and Melinte-Dobrinescu, M.: Mid-Cretaceous Oceanic Anoxic Events in the outer Eastern Carpathians: biostratigraphic and chemostratigraphic events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9283, https://doi.org/10.5194/egusphere-egu24-9283, 2024.

EGU24-9491 | ECS | Orals | SSP1.2

Enhanced global weathering in response to Central Atlantic Magmatic Province volcanism across the Triassic–Jurassic transition: an osmium isotope record from the Prees borehole (UK) 

Giorgia Ballabio, Weimu Xu, Daniel Hnatyshin, Micha Ruhl, David van Acken, Alex J Dickson, and Stephen P Hesselbo

The Triassic–Jurassic transition (~201.5 Ma) is marked by abrupt positive and negative Carbon-isotope excursions in marine and terrestrial sedimentary records. These excursions reflect global carbon cycle perturbations occurring in response to the massive volume of carbon released from the Central Atlantic Magmatic Province (CAMP). The subsequent doubling to tripling in atmospheric pCO2 led to ocean acidification and the development of marine anoxia, thought to have caused the end-Triassic mass extinction, one of the biggest mass extinctions of the Phanerozoic. Organic-rich sediments can record the evolution of the seawater osmium (Os) isotopic composition, which is controlled by the balance between weathering inputs from continental crustal rocks (187Os/188Os ~ 1.4) and from mafic and ultramafic basalts (187Os/188Os ~ 0.13). Here, we present the first 187Os/188Os isotope data across the Triassic–Jurassic transition from the Prees core (Cheshire Basin, UK), drilled for the International Continental Scientific Drilling Program (ICDP) Early Jurassic Earth System and Time-scale (JET) project. Our new Os-isotope data show two major excursions towards mantle 187Os/188Os signature across the Triassic–Jurassic transition which we interpret to be the result of the emplacement of CAMP and the fast weathering of juvenile basalts.

How to cite: Ballabio, G., Xu, W., Hnatyshin, D., Ruhl, M., van Acken, D., Dickson, A. J., and Hesselbo, S. P.: Enhanced global weathering in response to Central Atlantic Magmatic Province volcanism across the Triassic–Jurassic transition: an osmium isotope record from the Prees borehole (UK), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9491, https://doi.org/10.5194/egusphere-egu24-9491, 2024.

EGU24-10625 | ECS | Orals | SSP1.2 | Highlight

Permian-Triassic CO2 before, during and after the mass extinction 

Hana Jurikova, Ross Whiteford, Claudio Garbelli, Wenquian Wang, Guang Rong Shi, Shuzhong Shen, Lucia Angiolini, and James Rae

The study of mass extinctions is invaluable for understanding the effects of extreme environmental change on the different components of the Earth system and their responses and implications. Growing interest in extinctions, combined with new field evidence and analytical breakthroughs over recent years, has enabled us to zoom into individual events, construct their high-resolution chronologies and proxy records and start untangling their cause mechanisms from consequences. This is fundamental to progressing our knowledge, however, how far can we zoom in without overlooking the wider context? To what extent does the prior background climate state influence the outcome and magnitude of an extinction? For example, how would our understanding of the Permian-Triassic mass extinction change if we were to find the late Permian had low or high background CO2? And what was CO2’s fate in its aftermath? We present a new multi-million-year boron isotope-derived record of ocean pH and atmospheric CO2 spanning the Permian-Triassic, which allows us to establish the climate conditions before and after the mass extinction, as well as during the eruption of the Siberian Traps Large Igneous Province (LIPs) considered the ultimate cause (i.e. the trigger) of the extinction. We discuss the implications of our new CO2 record, and more broadly reflect on the role of background climate as a generalizable component of extinctions.

How to cite: Jurikova, H., Whiteford, R., Garbelli, C., Wang, W., Shi, G. R., Shen, S., Angiolini, L., and Rae, J.: Permian-Triassic CO2 before, during and after the mass extinction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10625, https://doi.org/10.5194/egusphere-egu24-10625, 2024.

EGU24-10757 | ECS | Posters on site | SSP1.2

Biosphere changes during the Carnian-Norian in Tasmania: A new perspective from PAH analysis from the Paleo Antarctic Circle. 

Indodeep Ghoshal, Aisha Al Suwaidi, Calum P Fox, Ohkouchi Naohiko, Ogawa Nanako O, and Suga Hisami

 

The Carnian–Norian, Late Triassic was a period of major global climatic change, often associated with a transition from arid to more humid conditions that began with the Carnian Pluvial Episode (CPE). This transition to wetter conditions is often linked to the emplacement of the Wrangellia Large Igneous Province (LIP), ~233 Mya in northern Panthalassa. Here, we present new organic geochemical data (molecular fossils) combined with organic carbon isotopes and elemental data from sediments of the Bicheno 3A core. These sediments represent fluvial deposits of the Upper Parmeener Supergroup, a freshwater sequence from eastern Tasmania. They offer a unique opportunity to examine the impact of this major climate transition at high latitudes in the paleo-southern polar circle. During the Late Triassic Tasmania was located at a latitude of -69°S, a position today occupied by the frozen continent of Antarctica.

 

Sediment samples from the BIC 3A core were processed and then analyzed in a gas chromatography (GC: Agilent 7890A System) for n-alkane and Polycyclic Aromatic Hydrocarbon (PAH) compounds. They were detected using a GC/mass spectrometry (Agilent 5975C Triple-Axis Detector.) Preliminary results from this study show an increase in soil erosion through the core based on higher concentrations of dibenzofuran and dibenzothiophene. A rise in retene concentrations during a similar time interval suggests an increased influx of terrestrial inputs further supporting enhanced hydrological conditions through the Late Triassic. Concentrations of an aggregate of PAHs spanning 3 to 7 rings associated with biomass burning also increase during a similar interval, suggesting increased wildfire activity, possibly driven by a shift to more humid conditions. When comparing the higher molecular weight PAHs (5- to 7-ringed PAHs) to the lower molecular weight PAHs (3-ring PAHs), a higher burning intensity and temperature towards the upper section of the core is observed since higher temperature wildfires produce PAHs with higher molecular weights. This upper section also shows indications of localized fire. Parameters including that of fluoranthene/ (fluoranthene + pyrene) and 1- and 2-methylphenanthrene/phenanthrene used to determine the origin of PAHs support that the PAHs from this sediment are of pyrogenic origin. This PAH profile from Tasmania represents a unique continuous record of climate change in high latitude Southern Hemisphere through the Carnian Pluvial Episode into the Norian, highlighting the complex interplay between fire and intensified rainfall in the Triassic paleo-Antarctic, as well as the major climatic and ecosystem changes experienced during this period.

How to cite: Ghoshal, I., Al Suwaidi, A., P Fox, C., Naohiko, O., Nanako O, O., and Hisami, S.: Biosphere changes during the Carnian-Norian in Tasmania: A new perspective from PAH analysis from the Paleo Antarctic Circle., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10757, https://doi.org/10.5194/egusphere-egu24-10757, 2024.

EGU24-10827 | Orals | SSP1.2

Assessment of Hg speciation changes from thermal desorption characteristics in sedimentary rocks 

Joost Frieling, Isabel M. Fendley, Muaz A. Nawaz, and Tamsin A. Mather

The total Hg (HgT) concentration data for geological samples, of interest as it may link to enhanced volcanic activity or other environmental changes, is a complex amalgamation of numerous surface and sediment processes. Drawdown by organic matter (OM) and sulfides (often approximated by total sediment sulfur concentrations, TS) have long been recognized as key drivers of variability in sedimentary HgT data. Most studies, therefore, employ a degree of normalization to a Hg “host” (HgT/TOC, HgT/TS) to extract anomalous Hg cycle behavior. The dominant host is often determined solely based on the strongest observed (linear) correlation but this widely applied method has been shown to suffer from various non-linearities in environmental processes and conditions that underlie the host-Hg relations and, crucially, does not allow succession-level, let alone sample-level, Hg speciation changes to be taken into account.

We here explore the use of thermal desorption characteristics for geological sediment (rock) samples. Thermal desorption profiles (TDPs) for many Hg species are well-established and have been used to, for example, distinguish between OM-bound Hg and different Hg sulfides, as well as Hg-oxides in (sub-)recent sediments. The typical method of analysis for TDPs is to use long (>15 minutes) multi-step temperature ramps. We adapt this technique to use only the rapid (< 3 minute) desorption that is obtained as standard for each sample analyzed in continuous-flow direct Hg analyzers. Using the rapid TDPs, we can clearly distinguish at least two Hg release phases, and find that (almost) all of the analyzed sedimentary silt and mud rock samples of Tithonian age (ca. 146 – 145 Ma) contain multiple Hg release phases. Analysis of each TDP allows quantification of the abundance of each phase, which can then be compared to potential hosts (TOC, TS) and other geochemical data on a sample and succession level.

Initial analyses of the TDP-informed Hg release for our samples indicate TOC concentration may determine 60 – 70% of the variability in the first (lower temperature) Hg release phase in our succession. This is a stark difference with the total Hg released from the same samples, for which only 20% of variation can be explained by TOC variability. The difference results from the variable presence of a later-stage (higher temperature) Hg phase that is anti-correlated with TOC.

The TDPs provide insight into sample-level Hg speciation and clearly demonstrate that the common assumption that Hg is exclusively associated with a single phase in sedimentary rocks throughout a succession is a large oversimplification. Further, we show that differences in Hg speciation can be detected and quantified in individual samples with minor adaptations of existing techniques. The TDPs offer a novel perspective on Hg analyses in geological samples and have the potential to test, validate, and supplement existing statistical models to detect anomalous Hg cycle behavior.

How to cite: Frieling, J., Fendley, I. M., Nawaz, M. A., and Mather, T. A.: Assessment of Hg speciation changes from thermal desorption characteristics in sedimentary rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10827, https://doi.org/10.5194/egusphere-egu24-10827, 2024.

EGU24-11863 | Orals | SSP1.2

Uranium-isotope records of global ocean deoxygenation during the Early Aptian Oceanic Anoxic Event (OAE 1a) 

Lawrence Percival, Alexander Dickson, Anirban Basu, José Castro, Pedro Ruiz-Ortiz, Cinzia Bottini, Elisabetta Erba, Jörg Mutterlose, Steven Goderis, and Philippe Claeys

The Phanerozoic Aeon was marked by several variations in global oxygenation levels, occuring both gradually over multi-million year timescales and also more abruptly as transient perturbations lasting typically a million years or less. Following an overall trend of rising atmospheric oxygen levels in the mid–late Palaeozoic, marine redox conditions are thought to have been close to modern by the time of the Cretaceous Period (145–66 Ma). However, the Cretaceous Period also featured multiple episodes of geologically abrupt depletions in seawater oxygen levels, known as Oceanic Anoxic Events (OAEs), one of the most severe of which occurred during the Early Aptian (OAE 1a, ~120 Ma). This environmental crisis is thought to have been triggered by major carbon emissions related to the volcanic formation of the Greater Ontong-Java Plateau. Several OAE 1a sites are marked by the preservation of organic-rich laminated shales, indicative of oxygen-depleted conditions in the water column and at the sediment-water interface. However, the relative paucity of Early Aptian open-ocean sedimentary records means that the degree to which anoxic conditions spread throughout the global marine realm during OAE 1a remains poorly constrained.

Here, we aim to verify the nature of seawater oxygen levels prior to, during, and after OAE 1a, using uranium-isotope (δ238U) records of that event. Under iron-reducing conditions, soluble U6+ transforms to insoluble U4+, which is associated with a pronounced isotopic fractionation in favour of 238U in U4+ ions. Thus, the subsequent sequestration of U4+ in organic-rich sediments causes depletion of 238U in the water column and a shift to an isotopically lighter δ238U composition of seawater. This change in marine δ238U is recorded by carbonates precipitated in seawater. Thus, δ238U trends across various records of OAE 1a enable the hypothesis that background Cretaceous ocean redox conditions were comparable to today to be tested, and the change in geographic extent of anoxic water masses during the environmental change quantified. By further comparing the δ238U data with other geochemical proxies (e.g., carbon-isotope evidence of organic-matter burial; osmium-isotope evidence of volcanism), we further explore the causes and environmental consequences of transient ocean redox fluctuations in the Early Cretaceous oceans.

How to cite: Percival, L., Dickson, A., Basu, A., Castro, J., Ruiz-Ortiz, P., Bottini, C., Erba, E., Mutterlose, J., Goderis, S., and Claeys, P.: Uranium-isotope records of global ocean deoxygenation during the Early Aptian Oceanic Anoxic Event (OAE 1a), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11863, https://doi.org/10.5194/egusphere-egu24-11863, 2024.

EGU24-12292 | Orals | SSP1.2

Volcanic proxies from the northern Pangean margin across the Permian-Triassic boundary: Evidence of intermittent Siberian Traps activity 

Morgan Jones, Alan Rooney, Valentin Zuchuat, Holly Turner, Joost Frieling, Tamsin Mather, Lars Augland, Arve Sleveland, Kim Senger, Peter Betlem, Anna Sartell, Øyvind Hammer, Jan Inge Faleide, and Sverre Planke

The End Permian Mass Extinction (EPME) occurred at 251.9 Ma and is the largest extinction event in the Phanerozoic. More than 80% of marine species and ~75% of terrestrial species were wiped out in <100 kyr. The event is marked by a negative carbon isotope excursion (CIE) that has a rapid onset and sustained duration, indicating the release of huge volumes of isotopically light carbon to the ocean-atmosphere system. The scientific consensus is that the carbon cycle disturbances were caused by the emplacement of the Siberian Traps large igneous province (LIP), likely from a combination of magmatic degassing and contact metamorphism in the organic carbon- and evaporite-rich Tunguska Basin. However, the timing and tempo of the Siberian Traps emplacement relative to the environmental disturbances can be better constrained. We investigated four shallow localities from Svalbard and the Barents Sea, which during the Permian-Triassic interval were part of a semi-enclosed epicontinental sea on the northern margin of Pangaea. We use osmium isotopes (188Os/187Os) and mercury (Hg) enrichments to identify when the Siberian Traps were most active with respect to carbon cycle disturbances (δ13Corg) through these four shallow marine archives. Our results indicate a strong volcanic signature coincident with the main negative CIE, with fluctuating signals through the body of the CIE itself that are indicative of pulsed Siberian Traps activity. Osmium isotopes show considerable variations through the Permian-Triassic boundary, suggesting that the enclosed nature of the seaway preserved rapid seawater chemistry changes in response to changing climatic and volcanic conditions. These far-field results can be directly tied to biomarker and radiometric age estimates of the EPME to improve the relative and absolute chronologies of the extinction event and the elevated magmatic activity.

How to cite: Jones, M., Rooney, A., Zuchuat, V., Turner, H., Frieling, J., Mather, T., Augland, L., Sleveland, A., Senger, K., Betlem, P., Sartell, A., Hammer, Ø., Faleide, J. I., and Planke, S.: Volcanic proxies from the northern Pangean margin across the Permian-Triassic boundary: Evidence of intermittent Siberian Traps activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12292, https://doi.org/10.5194/egusphere-egu24-12292, 2024.

EGU24-13288 | Posters on site | SSP1.2

Volcanic and thermogenic emissions from the North Atlantic Igneous Province: Insights from melt and fluid inclusions 

Stephen Jones, Manfredo Capriolo, David Muirhead, and Christian Tegner

Throughout the Phanerozoic, temporal coincidence between Large Igneous Provinces (LIPs) and climate perturbations points to a potential causality via volcanic and thermogenic emissions. The best documented example of this association consists in the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), which represents the most recent natural analogue for anthropogenic greenhouse gas emissions flux [1]. The NAIP extends from Greenland to the Scandinavian Peninsula and the British Isles, but the East Greenland margin preserves one of the most studied magmatic systems: the Skaergaard intrusion and its overlying 6-8 km thick lava pile, close to the centre of the province [2]. Melt and fluid inclusions within intrusive and effusive rock samples from East Greenland were screened and selected to investigate their volatile content by confocal Raman microspectroscopy. In the effusive rock samples, phenocrysts of olivine, clinopyroxene and sometimes plagioclase host primary melt inclusions containing gas bubbles. On the contrary, in the intrusive rock samples, most of primary melt inclusions within olivine crystals do not contain any gas bubble. However, in these rock samples, quartz often occurs as interstitial subhedral crystals or forms graphic textures with alkali feldspar, and hosts abundant multiphase (i.e., gaseous ± liquid ± solid phases) fluid inclusions. In general, the investigation of volatile species preserved by melt and fluid inclusions within magmatic minerals allows the reconstruction of volcanic and thermogenic emissions from LIPs [3; 4]. Here, we present preliminary data of this ongoing project that aims to constrain the role of volatiles from the NAIP in driving the synchronous PETM.

 

[1] Jones et al. (2019), Nat. Commun. 10, 5547.

[2] Larsen & Tegner (2006), Lithos 92, 181–197.

[3] Capriolo et al. (2020), Nat. Commun. 11, 1670.

[4] Capriolo et al. (2021), Nat. Commun. 12, 5534.

How to cite: Jones, S., Capriolo, M., Muirhead, D., and Tegner, C.: Volcanic and thermogenic emissions from the North Atlantic Igneous Province: Insights from melt and fluid inclusions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13288, https://doi.org/10.5194/egusphere-egu24-13288, 2024.

EGU24-14532 | ECS | Orals | SSP1.2

The age and extent of the late Maastrichtian calcification stress at Bidart, France 

Subham Patra, Kebenle Kesen, Gerta Keller, Eric Font, Thierry Adatte, and Jahnavi Punekar

The final 0.5 m of the Cretaceous-Paleogene (K/Pg) boundary at Bidart (France) is characterized by geochemical, taphonomic, and biotic vestiges of an ocean acidification event linked with Deccan volcanism. The larger (>150 μm) planktic foraminifera morphogroups show varying populations (absolute abundance), with lowered abundances within the Deccan benchmark (final 0.5 m) and a demographic collapse at the K/Pg boundary. Additionally, the Deccan benchmark exhibits diminished test size (p: <0.00001), wall thickness (p: 0.0005), and mixed-layer diversity (p: 0.000967), suggesting the presence of calcification stress. Nevertheless, the benthic environment presents contrasting results, with rare occurrences of size and wall thickness reduction or significant census disturbances in the benchmark, suggesting a lower degree of environmental stress. Notably, a significant increase in the relative proportion of Cibicidoides spp. (~48%; p: <0.00001), Steinsioenia spp. (~11%; p: <0.00001) and Coryphostoma spp. (~9%; p: 0.000033) is recorded at the K/Pg. Near the boundary, there is a significant decrease in the relative abundance (p: 0.001097) and diversity of infaunal benthic foraminifera (p: 0.000035). This decline signifies a collapse in productivity, aligning with a negative excursion in the carbon isotope signature at the K/Pg boundary. These results suggest that the acidification was restricted to the surface ocean and had a limited effect on benthic environment. This is consistent with the lack of extinction within the benthic community at K/Pg. A Graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles (Tunisia) through Hg peaks constrain the Deccan benchmark interval to the final ~58 ky of the late Maastrichtian, culminating in the K/Pg mass extinction.

How to cite: Patra, S., Kesen, K., Keller, G., Font, E., Adatte, T., and Punekar, J.: The age and extent of the late Maastrichtian calcification stress at Bidart, France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14532, https://doi.org/10.5194/egusphere-egu24-14532, 2024.

EGU24-14747 | ECS | Posters on site | SSP1.2

The massive weathering of the Central Atlantic Magmatic Provinces reconstructed from marine osmium isotopic ratio records 

Ryota Murai, Junichiro Kuroda, Kazumasa Mukai, Nanako O. Ogawa, Katsuhiko Suzuki, Naohiko Ohkouchi, and Rie S. Hori

It is widely recognized that one of the main cause of the end-Triassic Mass Extinction (~201.4 Ma) was the formation of one of the Large Igneous Provinces (LIPs), the Central Atlantic Magmatic Province (CAMP). CAMP consists of extrusive and intrusive rocks, mainly basalt, but most of the extrusive rocks is not present today. This is interpreted as a result of the rapid weathering of the extrusive rocks. However, temporal constraints of the weathering events have not been well-established yet, leaving the linkage with paleoenvironmental changes unclear. Osmium isotopic ratio (187Os/188Os) in the ocean is one of the geochemical proxies to reconstruct the past activities of LIPs. The osmium isotopic ratio reflects the relative contribution from three sources: upper continental crust (187Os/188Os=~1.3), extraterrestrial material (~0.13), and mantle (~0.13). Therefore, the rapid weathering of the CAMP extrusive rocks, which are mantle-derived, is expected to have decreased the marine osmium isotopic ratio. In this study, we aimed to clarify the relationship between the igneous activity caused by the CAMP formation and the fluctuations in the marine osmium isotopic ratio by examining the changes in osmium isotopic ratio of Panthalassa at the end-Triassic. In this study, we investigated the Miyanoura Section located in Shikoku, southwest Japan. This section is a bedded cherts sequence in the southern Chichibu Belt. The age of sediment was roughly estimated as Upper Triassic based on radiolarian biostratigraphy, although the radiolarian tests are poorly preserved. Measurements of osmium concentration, rhenium (Re) concentration, and Os isotopic ratio were performed. The initial osmium isotopic ratio (187Os/188Osi) was determined by age correction of 200 Ma for the bedded chert in the Miyanoura section. The results revealed a significant decrease in the marine Os isotopic ratio over approximately 100,000 years at the end-Triassic. The onset of this decrease coincides with a negative isotopic excursion of total organic carbon, which is correlated to the widely recognized Initial Carbon Isotope Excursion (ICIE), one of the characteristic changes in the end-Triassic, and also overlaps with the formation period of the CAMP. This suggests that the decrease in the marine Os isotopic ratio during this period was caused by the massive and rapid weathering of the CAMP extrusive rocks. In this presentation, I will introduce a quantitative evaluation using a simple box model and further discuss the paleoenvironmental changes that triggered this weathering event.

How to cite: Murai, R., Kuroda, J., Mukai, K., O. Ogawa, N., Suzuki, K., Ohkouchi, N., and S. Hori, R.: The massive weathering of the Central Atlantic Magmatic Provinces reconstructed from marine osmium isotopic ratio records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14747, https://doi.org/10.5194/egusphere-egu24-14747, 2024.

EGU24-16343 | ECS | Posters on site | SSP1.2

Testimonies from Tethys:  Faunal and environment shifts across the Cretaceous–Paleogene boundary (KPB) 

Uygar Karabeyoglu, Thierry Adatte, Marcel Regelous, and Jorge Spangenberg

The interplay between Large Igneous Provinces (LIPs) and significant mass extinctions has been widely acknowledged for a long time (e.g., Courtillot and Renne, 2003). What makes the K/Pg boundary (KPB) extinction significant is the simultaneous occurrence of two major catastrophic events – the Deccan volcanism and the Chicxulub impact – within a very brief timeframe (Schoene et al., 2019). To better understand the link between volcanic eruptions and the resulting environmental stress, it's crucial to delve into the impact of the Deccan volcanic activity on the ecosystem. To uncover this phenomenon, our focus lies in detailing this relationship using detailed counts of species along with isotope and geochemical analyses conducted on two complete sections within the Mudurnu-Göynük and Haymana basins in central Anatolia (Turkey).

Over the late Maastrichtian period, our examination of δ13C measurements in the Haymana Basin exhibits cyclical patterns that underscore the influence of precession cycles on the δ13C record. Intriguingly, each cycle concludes with a sudden cooling event (a positive shift in δ18O values). A quantitative assessment of planktic foraminifera, on the other hand, shows a continual decline in species diversity throughout the late Maastrichtian (Karabeyoglu et al., 2019). This decline seems to accelerate just before reaching the K/Pg boundary. In the Göynük and Okçular sections, this decline aligns with distinct intervals of low magnetic susceptibility, hinting at a possible event of ocean acidification during the late Maastrichtian.

The K/Pg boundary itself is identifiable by a reddish oxidized layer measuring 2-3 mm in thickness. This layer provides evidence of a sequence of events: the abrupt disappearance of large, specialized ecological specialists (such as globotruncanids, racemiguembelinids, planoglobulinids), a surge in mercury (Hg), and increased levels of trace elements (e.g., Iridium (Ir), Tellurium (Te), Nickel (Ni), Chromium (Cr), and Cobalt (Co)). Notably, the correlation between Hg/Te suggests that Te might serve as a proxy for volcanic activity. In terms of the faunal record, we observed peaks in Thoracosphaera and Guembelitria cretacea, signifying an ecosystem collapse following the KPB.

In summary, our comprehensive examination of paleontological, isotopic, and geochemical data indicates that the detrimental impacts of Deccan volcanism had already begun prior to the Chicxulub impact. This predisposed the fauna to an eventual extinction event at the K/Pg boundary.

References

Courtillot, V.E., Renne, P.R. 2003. On the ages of flood basalt events. Comptes Rendus Geoscience, 335, 113–140.

Schoene, B., Eddy, M.P., Samperton, K.M., Keller, C.B., Keller, G., Adatte, T., Khadri, S.F.R. 2019. U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction. Science, 363, 862-866.

Karabeyoglu, A.U., Özkan-Altıner, S., Altıner, D. 2019. Quantitative analysis of planktonic foraminifera across the Cretaceous-Paleogene transition and observations on the extinction horizon, Haymana Basin, Turkey. Cretaceous Research, 104, 104169.

How to cite: Karabeyoglu, U., Adatte, T., Regelous, M., and Spangenberg, J.: Testimonies from Tethys:  Faunal and environment shifts across the Cretaceous–Paleogene boundary (KPB), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16343, https://doi.org/10.5194/egusphere-egu24-16343, 2024.

EGU24-16856 | Orals | SSP1.2

Challenges and insights from zircon and baddeleyite U-Pb ages and Hf isotope analyses of Karoo and Siberian LIP intrusive rocks 

Urs Schaltegger, Sean P. Gaynor, Andre Paul, Joshua H.F.L. Davies, Henrik Svensen, and Jahandar Ramezani

The emplacement of Large Igneous Provinces (LIPs) has been interpreted as the cause of many environmental and biotic crises during Earth's history, largely due to their potential for introducing massive volumes of volcanogenic and thermogenic gases into the atmosphere. To assess this potential link, it is crucial to evaluate the potential coincidence of environmental perturbation, fluctuations in biodiversity, and extinction periods with LIP emplacement, requiring high-precision geochronology of LIP rocks. Volumetrically, most magmas and lavas associated LIPs are mafic, which presents as a significant challenge for high-precision geochronology, as mafic magmas rarely saturate U-bearing minerals, such as zircon or baddeleyite. In such a case, 40Ar/39Ar dating of plagioclase from these rocks is carried out, which has geological and analytical complications that may lead to inaccurate ages, and subsequently to flawed geologic models (Antoine et al., 2022).

Recent work has shown that high-silica melt pockets in LIP intrusions, contaminated by wall rock at the emplacement level, can crystallize mineral phases useful for high-precision U-Pb dating. The process of sedimentary wall rock contamination directly affects the composition of these minerals, as anatexis of this material significantly shifts the Hf isotope composition of zircon (and baddeleyite) away from mantle composition. These interactions between LIP intrusions and their wall rock can cause significant complications within the age spectra of these mineral phases.

Baddeleyite, the first U-rich phase to saturate during LIP magma crystallization, commonly yields anomalously young and scattering dates from partial loss of radiogenic Pb. Zircon is a rare mineral in these rocks. Its scatter in U-Pb dates is a combination of residual Pb loss after chemical abrasion and traces of xenocrystic components in the zircon grain, derived from inherited zircon during the contamination process. Zircon U-Pb ages are particularly significant, as zircon crystallization not only records igneous solidification, but also wall rock interaction and thermogenic gas generation, allowing for high-precision geochronology of potential climate altering events.

We will present new data sets of high-precision zircon and baddeleyite U-Pb and Hf isotope data, from sills of the Karoo and the Siberian Trap LIPs and highlight the potential implications for thorough understanding of the intrusive emplacement mechanisms. The Hf isotope compositions from both LIPs indicate localized contamination of the magma, indicating entrainment, anatexis and assimilation of wall rock during emplacement and sill inflation. Interpreted U-Pb ages of samples throughout the intrusive structure of the Siberian Trap LIP and the Karoo LIP indicate that not only was magma emplacement protracted over a few 100 ky within their subvolcanic domains, but that there was a similar temporal-structural progression of downward migrating emplacement through intrusive assembly. Finally, intrusive emplacement and associated wall rock thermogenic reactions for both LIPs are coeval with well documented periods of global climate change and carbon cycle perturbation in the lower Toarcian and lower Triassic, respectively.

Cited reference: Antoine et al. (2022) Chem. Geol. 610, 121086

How to cite: Schaltegger, U., Gaynor, S. P., Paul, A., Davies, J. H. F. L., Svensen, H., and Ramezani, J.: Challenges and insights from zircon and baddeleyite U-Pb ages and Hf isotope analyses of Karoo and Siberian LIP intrusive rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16856, https://doi.org/10.5194/egusphere-egu24-16856, 2024.

EGU24-18517 | ECS | Orals | SSP1.2

The Bonarelli level (Gubbio, Italy) reveals a potential correlation between the occurrence of oceanic anoxic events and large-scale magmatic activity 

Giulia Marras, Vincenzo Stagno, Luca Aldega, Marino Domenico Barberio, Federica Benedetti, Irene Cornacchia, Jabrane Labidi, Guia Morelli, Nereo Preto, Valentina Rimondi, and Marco Brandano

Global and local paleo-environmental changes across Earth’s history can be tracked by investigating the sedimentary record. Large Igneous Provinces (LIPs), whose activity spans from 250 to 50 Ma, are known to be coeval to the Phanerozoic largest mass extinctions and the Oceanic Anoxic Events (OAEs), the latter identified in the marine sedimentary rocks through key geochemical proxies such as high organic matter content (up to 30%) and positive excursions in the δ13C values. The Bonarelli level, a ~0.9-m thick layer made up of organic-rich shales, cropping out at Valle della Contessa section in Gubbio (Italy) within the pelagic limestones of the Scaglia Bianca Formation, is the stratigraphic marker of OAE2 (Cenomanian-Turonian, ~93 Ma). This event was likely triggered by submarine volcanism of the High Arctic and Caribbean LIPs, although clear evidence is missing at present, that might be given by the study of geochemical markers like mercury (Hg) claimed as a signature within sedimentary layers for large volcanic eruptions.
We present the results of X-ray diffraction, petrographic and geochemical (Total Organic Carbon, Hg concentration, trace elements, Hg, S and Sr isotopes) analyses on eleven rock samples collected from the Bonarelli level along with eleven rocks samples from the Scaglia Bianca Formation, to establish a potential link between OAEs and LIP volcanism.
LIP-related basalts are known to have 1 to 4 µg/kg of Hg (Yin et al. 2022). Interestingly, our results show a sharp Hg anomaly up to ~1600 µg/kg measured in the black shales, pointing out episodes of large Hg emissions accompanied by volatile degassing. Such anomaly correlates positively with the concentration of chalcophile elements such as Cu, Ni and Fe and with the amount of sulfate (barite and jarosite) + sulfide (pyrite), likely the main Hg-bearing minerals. A major effect of organic matter accumulation on the Hg contents was excluded because of the high Hg/TOC ratios. Hg isotopic data suggest a (deep) mantle-derived magmatic contribution that is not accompanied by a similar mantle signature of Sr and S isotopes. In contrast, we observed a continental input for Sr and S signature controlled by diagenetic processes in marine environment (e.g., pyrite deposition in anoxic seawater), atmospheric oxidation and seawater mixing. We interpret these findings as evidence of large-scale magmatism, which triggered greenhouse state increasing continental weathering. 


Yin, R., et al. (2022). Mantle Hg isotopic heterogeneity and evidence of oceanic Hg recycling into the mantle. Nature communications, 13(1), 948.

How to cite: Marras, G., Stagno, V., Aldega, L., Barberio, M. D., Benedetti, F., Cornacchia, I., Labidi, J., Morelli, G., Preto, N., Rimondi, V., and Brandano, M.: The Bonarelli level (Gubbio, Italy) reveals a potential correlation between the occurrence of oceanic anoxic events and large-scale magmatic activity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18517, https://doi.org/10.5194/egusphere-egu24-18517, 2024.

EGU24-20588 | Orals | SSP1.2

Marine snowstorm during the Permian−Triassic mass extinction   

Stephen Grasby, Omid Ardakani, Xiaojun Liu, David Bond, Paul Wignall, and Lorna Strachan

The Permian−Triassic mass extinction (PTME) interval is marked by major excursions in both inorganic and organic carbon (C) isotopes. Carbon cycle models predict that these trends were driven by large increases in productivity, yet organic C−rich rocks are not recorded in most PTME shelf sedimentary successions. Anomalous C-rich facies have been reported from rare abyssal plains records now exposed in Japan and New Zealand, where black shales at the PTME are extraordinarily organic-rich units. We examined organic matter at the Waiheke, New Zealand, section, and results show that these deposits are dominated by lamalginites composed of unicellar solitary or colonial phytoplankton produced during algal blooms that falls as “marine snow.” We modeled the impact of ash fall from eruptions in the Siberian Traps large igneous province and argue that they fertilized the Panthalassa Ocean with P and Fe, leading to a marine “snowstorm” and significant C drawdown marking this major biobloom during the PTME.

How to cite: Grasby, S., Ardakani, O., Liu, X., Bond, D., Wignall, P., and Strachan, L.: Marine snowstorm during the Permian−Triassic mass extinction  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20588, https://doi.org/10.5194/egusphere-egu24-20588, 2024.

EGU24-22199 | Orals | SSP1.2

Earliest eruption of the Deccan Large Igneous Province: a potential trigger of the Late Maastrichtian abrupt warming event  

Rilla McKeegan, Thierry Adatte, Blair Schoene, Michael P Eddy, Matthieu Galvez, Syed FR Khadri, and Silvia Omodeo Sale

The Chicxulub impact in Mexico and Deccan volcanism in India are both linked to the end-Cretaceous mass extinction but the relative timing of the impact, volcanic eruptions, and environmental changes remain controversial, precluding a full assessment of their respective roles. The bulk (80%) of Deccan Trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology reveals the onset of this main eruption phase 350 ky before the Cretaceous-Tertiary (KT) mass extinction.

U-Pb zircon geochronology from Malwa Plateau basalts on the northern margin of the Deccan LIP are temporally correlative with the first pulse of Deccan volcanism, which is coeval with a ∼200 kyr Late Maastrichtian warming event preserved globally in contemporaneous stratigraphic sections. This 2.5–8°C warming has been inferred by several studies on the basis of δ18O in benthic foraminifera, pedogenic carbonate and bivalve shells, as well as changes in leaf morphology. The onset of this excursion is temporally correlative to the initial decline in oceanic 187Os/188Os toward more radiogenic values and increasing Hg contents.

This first pulse of Deccan magmatism erupted through organic-rich sedimentary Permian rocks of the Narmada-Tapi rift basin. Direct CO2 emissions from basalt are unlikely to cause this magnitude of warming, except at extreme eruption rates, which is difficult to reconcile with the likely longer duration and lower eruption rates inferred from this first eruptive pulse. Thermal contact metamorphism of these sediments could have been a source of sufficient CO2 to drive the Late Maastrichtian warming event. The aim of this study is to understand the fate of C, Hg and S during the contact metamorphism associated with the first Deccan pulse and to evaluate the importance of this process in the global C, Hg and S cycles.

Our data are based on measurements of contact aureoles around several dikes and sills intruding in Permian organic-rich coal located in the Narmada-Tapi rift basin. We focused on TOC, Hg and S contents. While the sediments further away from the intrusions show high levels of TOC (>20%) and significant contents in Hg and S, the samples located in the aureoles (around 5 m thick) show a nearly total loss of the same elements. Our initial results demonstrate that the global C, S and Hg cycles can be substantially perturbed after LIP-scale sill and dyke emplacement in organic-rich sedimentary rocks. Deccan volcanism likely contributed to climate instability in the late Cretaceous and may have exacerbated the environmental effects of the Chicxulub impact.

How to cite: McKeegan, R., Adatte, T., Schoene, B., Eddy, M. P., Galvez, M., Khadri, S. F., and Omodeo Sale, S.: Earliest eruption of the Deccan Large Igneous Province: a potential trigger of the Late Maastrichtian abrupt warming event , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22199, https://doi.org/10.5194/egusphere-egu24-22199, 2024.

EGU24-22352 | Orals | SSP1.2

Anomalies of sulfur compound-specific molecular fossils link terrestrial ecosystem collapse to the end-Triassic crisis 

Linhao Fang, Hongjia Li, Xiaoyu Zhang, Guangli Wang, Yuanzheng Lu, Shenghui Deng, Meijun Li, Paul Wignall, and Robert Newton

The end-Triassic mass extinction (ETE), one of the “Big Five” in Earth history, was triggered by Central Atlantic Magmatic Province (CAMP) volcanism, releasing voluminous CO2, SO2 and halocarbons, which affected global marine and terrestrial ecosystems through atmospheric circulations. The terrestrial ecosystem collapse is commonly attributed to CO2-drivengreenhouse effects changing climates that consequently impacted flora and fauna, but this fails to explain why atmospheric CO2 with long retention timejust dominates a range of short-lived crises. Here, we investigate two terrestrial Triassic-Jurassic sections in each high- and low/middle- paleolatitude, finding anomalies of sulfur-associated molecular fossils, biomarker proxies of “high-temperature wildfires” and higher plants burial. These coincide with relatively short CAMP climax (lasting ~ 60,000 years). We propose a novel hypothesis that the high-intensity pulses of acid rains originated from CAMP climax dominated catastrophic defoliation, which oversupply dead moisture-free biomass as fuels in unusual rates, leaving coeval widespread abnormally high-temperature wildfires and spikes of sulfur compound-specific molecules in terrestrial sediments as fingerprints of acid rain deposition.

 

How to cite: Fang, L., Li, H., Zhang, X., Wang, G., Lu, Y., Deng, S., Li, M., Wignall, P., and Newton, R.: Anomalies of sulfur compound-specific molecular fossils link terrestrial ecosystem collapse to the end-Triassic crisis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22352, https://doi.org/10.5194/egusphere-egu24-22352, 2024.

EGU24-225 | ECS | Posters on site | SSP1.3

An examination of episodic dolomite cementation in an Early-Miocene Eger Rift lake deposits (Czech Republic) 

Daniel A. Petrash, Philip T. Staudigel, Miguel Bernecker, Patricia Roeser, and Giovanna Della Porta

This study aims to enhance the understanding of geomicrobiological processes and low-temperature dolomite formation, a field significantly developed by Judith A. McKenzie1. It focuses on shallow burial diagenetic dolomite from the onset of the Miocene Climatic Optimum (MCO, 16.9-14.7 Ma)2. Our investigation entailed examining interstitial ferroan and calcian dolomite in claystone (dolomitic mudstone), and integrates bulk-rock stable isotopes (C, N, Δ47 and Δ48) and elemental concentration analyses. The mineral is partially ordered (mean I(015)/I(110)=0.42), microcrystalline (2 to 12 μm) and predominantly subhedral (planar-s). Isotopic data revealed it formed under substantial benthic microbial activity, as evidenced by δ15N values suggestive of sustained N2 losses (+8.59 ± 2.51 ‰, median 9.50 ‰, N=19)—as typically observed in sedimentary settings featuring high rates of denitrification and anammox. Dolomite δ¹³C values (+1.41 to +11.44 ‰, median 7.58‰, N=19) record a mixture of dissolved inorganic carbon sources, dominated by methanogenic CO2. In the ca. 70 m-thick, partially eroded lacustrine succession, conspicuous correlation between dolomite abundances and bulk-rock potassium and barium levels provides evidence of episodic increases in chemical weathering during the warm and humid MCO climate2. The results reveal complex causal interactions linked to fluctuating pore-water dolomite precipitation potentials. Accordingly, Miocene oscillations in pCO2 levels accelerated silicate weathering in catchment areas dominated by alkaline igneous bedrocks, including  trachybasalt3, K-rich peridotite and granitoids, thus enriching nearby prevalently anoxic rift paleolake with dolomite-ankerite reactants (i.e., reducible Fe3+, Mg2+ and Ca2+)3 and macronutrients (e.g., iron(III) oxide-bound PO43-). Overall, these sedimentary dynamics, coupled with the influx of soil-derived oxidized nutrients, enhanced benthic ferric iron-based respiration and the sediment redox buffering capacity, which was conducive to punctuated, interstitial dolomite cementation. The dolomite-bearing claystone levels, characterized by Post-Archean Shale-normalized positive europium anomalies, challenge traditional hydrothermal interpretations of dolomitization in rift lakes. Their coupled isotope values (∆47 and ∆48, Bernecker et al., 2024: EGU24-11056) point to formation at temperatures below 40°C, and in a shallow-burial diagenetic realm where the pore fluids and dolomite interacted within a closed system4.  Climate variability during the onset of the MCO, along with changes in precipitation and weathering regimes, likely played a fundamental role in establishing the internal boundary conditions necessary for lacustrine dolomite formation.

References

1. Vasconcelos, C., McKenzie, J., Bernasconi, S. et al. Nature 377, 220–222 (1995).
2. Kříbek, B., et al. J. Paleolimnol. 58, 169–190 (2017).
3. Rapprich, V. et al. Depos. Rec. 9, 871–894 (2023).
4. Staudigel, P., et al. Geochemistry, Geophysics, Geosystems 24, e2023GC011117 (2023).

How to cite: Petrash, D. A., Staudigel, P. T., Bernecker, M., Roeser, P., and Della Porta, G.: An examination of episodic dolomite cementation in an Early-Miocene Eger Rift lake deposits (Czech Republic), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-225, https://doi.org/10.5194/egusphere-egu24-225, 2024.

The hydration structure at the mineral-water interface is decisive for understanding fundamental reactions taking place at mineral surfaces, including mineral dissolution, growth and weathering. Recent advancements in three-dimensional atomic force microscopy (3D AFM) have opened the potential to directly image the hydration structure above a surface, providing unparalleled structural insights into mineral−water interfaces [1].

Here, the hydration structures at the calcite-water [2] and dolomite-water [3] interface will be presented with an emphasis on discussing the differences that arise from the presence of magnesium in dolomite as compared to calcium in calcite. Analysing site-specific vertical positions of hydration layers and comparing them with molecular dynamics simulations unambiguously unravels the minute but decisive difference in ion hydration and provides a clear means for telling calcium and magnesium ions apart.

 

[1]         T. Fukuma, Y. Ueda, S. Yoshioka, H. Asakawa, Phys. Rev. Lett. 2010, 104, 016101

[2]         H. Söngen, M. Nalbach, H. Adam, A. Kühnle, Rev. Sci. Instrum. 2016, 87, 063704

[3]         H. Söngen, C. Marutschke, P. Spijker, E. Holmgren, I. Hermes, R. Bechstein, S. Klassen, J. Tracey, A. S. Foster, A. Kühnle, Langmuir 2017, 33, 125

How to cite: Kühnle, A.: Hydration structure on dolomite: Telling calcium and magnesium apart, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1334, https://doi.org/10.5194/egusphere-egu24-1334, 2024.

EGU24-2796 | Orals | SSP1.3

The origin of Jurassic FeMn deposits and their reliability as geochemical archives for Tethian seawater 

Sebastian Viehmann, Viona Klamt, Dennis Kraemer, Ingo Horn, Claus Rüscher, Simon V. Hohl, Oscar Fernandez, and Stefan Weyer

Modern to Cenozoic hydrogenetic FeMn nodules and crusts are reliable geochemical archives of past seawater chemistry. In this study, we report the first petrographic and geochemical data of Jurassic FeMn nodules and crusts from the Calcaereous Alps of the Pyhrntal area (Austria) that were formed ca. 170 million years ago and, thus, ~ 10 million years after the Toarcian extinction event. The combined approach of petrographic data, including XRD and SEM+BSE, with major and trace element signatures and stable U-Mo isotopes of individual FeMn nodule and crust layers obtained by tandem ICP-MS and MC-ICP-MS, respectively, is used to extend the geochemical record of marine FeMn deposits roughly 100 million years back in time and evaluate their reliability as archives for Jurassic seawater. Trace elements and redox-sensitive U-Mo isotopes aid in reconstructing the origin of the FeMn nodules and redox conditions of Tethian seawater in the aftermath of the Toarcian extinction event.

The FeMn deposits of the Pyhrntal area can be subdivided into four types: Type I nodules rich in carbonates (< 90wt %; calcite, rhodochrosite) with minor Fe-oxides (10 wt%; hematite, goethite) and clays (< 20 wt %). Manganese-rich type II nodules (< 75 %; todorokite, ranceite) contain fewer carbonates (< 47 wt %), Fe oxides (<40 wt %), and clays (< 10 wt %). Type III nodules and crusts rich in Fe oxides (< 60 wt %) and carbonates (< 60 wt %) with minor Mn oxides and type IV nodules with Fe- (< 50 wt %) and Mn- oxides (10 wt %), carbonates (< 30 wt %) and < 12 wt % of clay. Despite their different mineralogy, all four FeMn deposit types show sub-parallel shale-normalized rare earth elements and yttrium (REYSN) patterns that are typical of (modern) hydrogenetic FeMn deep-sea nodules and crusts, suggesting a seawater-derived origin. Typical REYSN features include strong positive CeSN anomalies due to the oxidation of Ce3+ to Ce4+ on (hydr)oxide surfaces and a negative YSN anomaly related to higher complex stability of Y in seawater relative to neighboring REY. Furthermore, stable U and Mo isotope compositions of all four types show a narrow range in δ98/95Mo (-0.97 to -0.56 ‰) and δ238/235U (-0.75 to -0.47 ‰), consistent with isotopic values observed in modern and Cenozoic FeMn deposits, suggesting an overall oxic water column at latest 18 Ma after the Toarcian extinction event.

The approach using petrography with major and trace element systematics in combination with stable U-Mo isotope signatures highlights the Tethian FeMn deposits as unique geochemical archives of Jurassic seawater that enable a reliable reconstruction of the origin of the Alpine FeMn deposits and the ambient redox conditions in Tethian paleo-environments. 

How to cite: Viehmann, S., Klamt, V., Kraemer, D., Horn, I., Rüscher, C., Hohl, S. V., Fernandez, O., and Weyer, S.: The origin of Jurassic FeMn deposits and their reliability as geochemical archives for Tethian seawater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2796, https://doi.org/10.5194/egusphere-egu24-2796, 2024.

During the Cretaceous, the Berriasian-Aptian interval witnessed a transition from a relatively cool climate with intermittent polar ice to a greenhouse state that persisted throughout the Late Cretaceous. These palaeoclimatic changes were associated with the construction of Large Igneous Provinces (LIPs), which significantly perturbed the ocean-atmosphere system by introducing large amounts of CO2, trace metals, and micronutrients, thereby impacting the biosphere. Our study focused on the Tethyan Ocean during the Early Cretaceous, examining the resilience of planktonic and shallow-water benthic calcifying algae to environmental changes. We observed their adaptation, recovery dynamics, and the influence of palaeoCO2 levels on their resilience. Calcification patterns of calcareous nannoplankton served as a proxy for ecological and engineering resilience. While calcareous nannoplankton as a whole showed high resistance, individual taxa exhibited varying levels of resilience. Nannoconids, particularly narrow-canal ones, were highly sensitive and had low resistance. In contrast, Watznaueria barnesiae showed the least sensitivity and highest resistance, likely due to its adaptive strategies and long lifespan. Nannoplankton calcification recovery (engineering resilience) from the Weissert Event took approximately 3 million years. After OAE1a, instead, nannoplankton did not return to pre-perturbation conditions. In shallow-water platforms, Dasycladales, aragonitic benthic calcifiers, exhibited lower resilience compared to nannofossils. They experienced a decline in species diversity across both the Weissert Event and the OAE 1a, which could indicate higher sensitivity to reduced carbonate saturation under high pCO2 conditions. After the Valanginian Weissert Event, Dasycladales were able to recover, albeit they show a much lower engineering resilience compared to nannoconids, as it took nearly 10 million years to revert to pre-disturbance diversity. The OAE 1a represented a more intense perturbation: their decrease of species diversity was much more drastic and permanent, and Dasycladales were unable to recover, losing their dominant role as carbonate platform biocalcifiers for the remainder of the Cretaceous. Our study provides an assessment of the resilience of Tethyan phytoplanktonic and shallow-water benthic calcifying algae to disturbances during the Early Cretaceous, with implications for tipping points associated with palaeo-CO2 levels. The differential responses in terms of timing and magnitude and the recovery dynamics contribute to the understanding of the potential impacts of current and future global changes on the resilience of marine ecosystems and the thresholds that may lead to ecological crises.

How to cite: Erba, E. and Parente, M.: The resilience of Tethyan planktonic and benthic calcifying algae to Early Cretaceous perturbations: comparison between the Valanginian Weissert Event and the early Aptian Oceanic Anoxic Event 1a, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2826, https://doi.org/10.5194/egusphere-egu24-2826, 2024.

At Schoenmakerskop on the coast near Gqeberha (Port Elizabeth), modern microbialite deposits are forming where CaCO₃-supersaturated groundwater emerges at the contact between Pleistocene aeolianites and the underlying Cape Supergroup bedrock (Edwards et al. 2017). Two different systems were investigated: well-laminated spring line tufa deposits above intertidal beachrocks, and a series of barrage pools with active and remnant rimstone deposits showing thrombolitic and laminated mesofabrics. Petrographic light-microscopy and scanning electron microscopy (SEM) were used to investigate the relative contributions of biotic and abiotic processes in the formation of these microbialites.

Light-microscopy identified isopachous light-brown sparry crusts consisting of tabular or platy carbonate, interpreted to have formed predominantly by chemical precipitation. Hybrid crusts were also found comprising alternating organic-rich layers and sparry crusts, along with colloform and micritic microtextures. Fossilised algal filaments were identified and SEM observations revealed both densely and loosely packed layers of hollow, unbranched filaments encrusted by microcrystalline carbonate. Exceptionally well-preserved draping biofilms were also found in some samples. Evidence for trapping and binding of clastic material was very limited, with only occasional diatom fragments. Taken together our observations point to a system dominated by chemical precipitation of carbonate with rapid precipitation leading to exceptional preservation of biofilms in submerged samples, and entombment of algal and sometimes microbial filaments. Evidence for biologically induced extracellular mineralisation of the algal filaments and microbial biofilms is recorded in these microbialites. The potential of these deposits to serve as analogues for chemical stromatolites in the fossil record is explored.

Edwards et al. (2017). Macro- and Meso-fabric structures of peritidal tufa stromatolites along the Eastern Cape coast of South Africa. Sedimentary Geology 359: 62-75.

How to cite: McLoughlin, N. and Mahlapha, K.: Microtextures of modern tufa stromatolites from the peritidal zone near Schoenmakerskop, Eastern Cape, South Africa: investigating the relative contributions of microbes, algae and chemical precipitation to microbialite growth   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3371, https://doi.org/10.5194/egusphere-egu24-3371, 2024.

Early lithification of carbonate mud during the subaerial exposure stage, under semiarid conditions, has been proposed to facilitate dolomite formation. However, how the biogeochemical processes during subaerial diagenesis promote dolomite formation remains unclear. Here, we employ a multiproxy approach to investigate the process of dolomite formation by analyzing modern dolomite crusts forming in lagoon Brejo do Espinho (LBE). Petrological analysis reveals that the crusts comprise coexisting high-Mg calcite (HMC) and dolomite. Low Fe and Mn concentrations indicate the formation of dolomite under oxic conditions, while a higher Sr concentration in well-lithified crust suggests primary bacterial-induced dolomite precipitation. The Mg isotopic composition of the crusts exhibits a lighter value compared to that of modern sabkha dolomite, suggesting different dolomitization processes and Mg sources. More negative δ13C values of the crusts than unlithified carbonate mud in LBE, indicating the incorporation of 13C depleted organic carbon. The biogeochemical processes related to decaying organic matter during subaerial diagenesis generate partially oxidized organic matter that promotes Mg2+ dehydration and enhances the dissolution of primary HMC, ultimately triggering the transition of HMC to dolomite or/and direct dolomite precipitation. The ancient "dolomite factory" operated through cyclic deposition of carbonate sediments and penecontemporaneous subaerial diagenesis.

How to cite: Ning, M., McKenzie, J. A., Vasconcelos, C., and Shen, B.: Dolomite formation during penecontemporaneous subaerial diagenesis: Evidence from modern dolomite crusts forming in lagoon Brejo do Espinho, Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3489, https://doi.org/10.5194/egusphere-egu24-3489, 2024.

 

Fundamentals of C-isotope geochemistry were established in the mid-1950s. Its use as a proxy in paleoceanography and paleoclimatology was long underestimated. While oxygen isotope geochemistry was identified early as a powerful tool in Ice Age history, carbon isotope geochemistry evolved only in the 1970s into a valuable instrument in paleoceanography and paleolimnology.  In 1976, Judy McKenzie was offered the chance to build the first stable isotope lab at ETH Zürich. Judy was, together with her team, among the first geoscientists searching for applications of C-isotope geochemistry in paleoceanography and limnogeology. Seasonal fluctuations in lake productivity were monitored in C-isotope composition of lake sediments and C-isotope records measured in pelagic carbonates served as a tracer of circulation and productivity in Cenozoic and Mesozoic oceans. In the eighties C-isotope geochemistry was recognized as a proxy of the global carbon cycle and its history was traced in C-isotope records measured in pelagic carbonates. The ETH Lab contributed with the several publications on C-isotopes and the carbon cycle to the seminal Chapman conference on “The Carbon Cycle and Atmospheric CO₂: Natural Variations Archean to Present” (Florida, 1984). An improved understanding of marine carbon fractionation processes allowed to use paired carbonate and organic carbon isotope analyses as a proxy for past atmospheric carbon dioxide concentrations. Today C-isotope geochemistry is established as a most valuable tool in paleoclimatology and paleoceanography, in sedimentology and geomicrobiology.

How to cite: Weissert, H.: Early days of carbon isotope geochemistry in paleoceanography and limnogeology - tales from Judy’s ETH Lab , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3855, https://doi.org/10.5194/egusphere-egu24-3855, 2024.

Hamelin Pool in Shark Bay, Western Australia, is a natural laboratory to study in situ stromatolitic carbonate formation in a hypersaline lagoon. Stromatolitic carbonates sampled at three different tidal environments (supratidal, intertidal and subtidal; cf. Martin et al., 2023) show a gradual increase in Ba isotopic compositions (d138Ba) from -0.12 ‰ to modern open ocean values (up to 0.6 ‰) with decreasing Ba concentrations following classic Rayleigh pattern. Declining Ba/Ca ratios (0.93 to 0.32) follow conservative mixing trends with increasing Co, Li, Sr and Ni concentrations from the shore to subtidal environments. Due to the lack of riverine influx into Shark Bay, groundwater discharge is the likeliest source for two end-members mixing with seawater. We observe fingerprints of the groundwater end-member in a supratidal sample showing particular low, stable Ba isotope values (-0.12 ‰), which further corresponds with elevated Mn/Sr ratios and the lowest O isotope compositions (2.9 ‰) as an indicator for a meteoric origin. This end-member likely reflects carbonate precipitation near shore under the influence of groundwater discharge and reaction with high alkalinity fluids derived from the local Tamala Limestone aquifer (d138Ba = 0.09 to 0.24 ‰ at 0.3 to 19 PSU; cf., Mayfield et al., 2021). In contrast, the stromatolitic carbonates that form in equilibrium with a saline end-member show heavy Ba isotope compositions (0.57‰).

Injection of alkaline groundwaters into the hypersaline waters of Hamelin Pool likely contributed to an enhanced rate of carbonate precipitation, possibly catalysed by nucleation within or onto extra-polymeric substances of diverse microbial mats. Interaction of benthic microbes, especially cyanobacteria, in alkaline waters may offer promising carbon sequestration pathways in the modern high pCO2 atmosphere and small-scale mitigation to the harmful impacts of the current climate crisis.

References: Martin et al., 2023, GCA; Mayfield et al., 2021, Nature Communications

How to cite: Hohl, S. V., Lin, Y., Viehmann, S., and Martin, A.: Conservative mixing of highly alkaline groundwater with hypersaline seawater at Shark Bay recorded by Ba isotopic compositions in stromatolitic carbonates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4713, https://doi.org/10.5194/egusphere-egu24-4713, 2024.

EGU24-6853 | Posters on site | SSP1.3

Controls of sulfur authigenesis in lacustrine sediments of the (pre-)Anthropocene: Sulfur and oxygen isotopes can tell 

Michael E. Böttcher, Patricia Roeser, Jens Kallmeyer, Vera Winde, Albrecht Leis, Tillman Harum, Anna Noffke, Iris Schmiedinger, Antje Schwalb, Martin Wessels, and Thomas Wolf

Benthic sulfur cycling in fresh-water lakes is typically characterized by low concentrations of dissolved sulfate in the overlying water column. This electron acceptor is the major driver for the anaerobic mineralization of organic matter in brackish-marine systems. Post-glacial development in marginal seas like the Baltic or Black Sea are often characterized by a transition from fresh to brackish water conditions, and initial sulfur isotope signatures of lacustrine sediments are often found to be superimposed by later diagenesis. To better understand the link between sulfate sources and the developing sedimentary sulfur isotope signatures in lake systems, Lake Constance’s main inflows, vertical water column profiles and sediment samples were geochemically and isotopically (S-34, O-18) characterized.

We found that dissolved sulfate concentrations and stable isotope signatures for the two major riverine contributors, Alpenrhein and Bregenzer Aach, differed substantially in their isotopic composition. The Alpenrhein dominates sulfate contribution into the lake system and its contribution could be traced throughout the lake with some indication for potential minor sulfur cycling within the water column. Wells demonstrated that the Bregenzer Aach lost water to an underground passage towards Lake Constance. Water-rock interactions also provided minor amounts of sulfate to the migrating groundwater.

The top 10 cm of surface sediments, representing the Anthropocene, indicated fast gross and net dissimilatory sulfate reduction and the formation of iron sulfides that are isotopically close to water column sulfate, but they were found to be depleted in the heavier isotope at greater depth, indicating lower ratios of net sulfate reduction versus sulfate replenishing rates in the past.

How to cite: Böttcher, M. E., Roeser, P., Kallmeyer, J., Winde, V., Leis, A., Harum, T., Noffke, A., Schmiedinger, I., Schwalb, A., Wessels, M., and Wolf, T.: Controls of sulfur authigenesis in lacustrine sediments of the (pre-)Anthropocene: Sulfur and oxygen isotopes can tell, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6853, https://doi.org/10.5194/egusphere-egu24-6853, 2024.

EGU24-7279 | Posters on site | SSP1.3

Insights into the genesis and geological significance of iron-manganese precipitates in the Baltic Sea, Gulf of Finland seafloor 

Martin Liira, Johanna Maria Ojap, Aivo Lepland, Sten Suuroja, Markus Ausmeel, Beata Szymczycha, Wei-Li Hong, Michael E. Böttcher, Joonas Virtasalo, Hannah Mikenberg, Atko Heinsalu, and Krete Roopõld

This study investigates the distribution and geological implications of iron-manganese (Fe-Mn) oxyhydroxide precipitates on the seafloor of the Gulf of Finland, with a particular focus on associated pockmarks and Fe-Mn concretions. The formations occur in regions devoid of modern sediment deposition, revealing exposure of late glacial glacio-lacustrine varved clays, glacial tills, or bedrock. Pockmarks, up to 3 m deep and 30-60 m wide, coexist with Fe-Mn concretions, exhibiting sub-vertical walls and microbial colonies, suggesting active seepage of chemically reduced fluids from underlying strata.

Globally occurring Fe-Mn concretions, sedimentary bodies primarily composed of iron and manganese compounds, exhibiting round or crust-like shapes formed through redox-driven processes in seabed environments. Microbial activity accelerates necessary redox reactions, influencing the growth of these concretions. The study delves into the morphological, chemical, and mineralogical characteristics of Fe-Mn concretions in the Gulf of Finland, identifying two distinct types—concentric and crust-like—with varied compositions, hinting at diverse formation mechanisms.

Elevated concentrations of precious and rare earth metals in these concretions raise interest for potential industrial applications. Fe-Mn concretions also serve as valuable indicators of sedimentary processes' geological history, exposing environmental changes over time, including anthropogenic pollution. Despite advancements, the genetic types of Fe-Mn concretions in Estonian sea areas remain elusive, emphasizing the need for further research.

The study integrates findings from three recent international expeditions to the central Gulf of Finland, aiming to comprehensively understand the relationships between fluid seepage, Fe-Mn concretions, and seafloor features. These expeditions collect representative materials, focusing on the timing and controls of groundwater discharge, mineral precipitation, and associated seafloor microbial processes. The preliminary results provide insights into the intricate geological processes underlying the observed seafloor features.

In conclusion, this collaborative effort contributes valuable information about the distribution and genetic characteristics of Fe-Mn precipitates and associated features in the Gulf of Finland. The simultaneous investigation of pockmarks and Fe-Mn concretions, along with their geological implications, enhances our understanding of these complex marine environments. Further research is essential to unravel the exact genetic types of Fe-Mn concretions in Estonian sea areas and to refine our knowledge of the dynamic interactions between fluid seepage, mineral precipitation, and microbial processes on the seafloor.

How to cite: Liira, M., Ojap, J. M., Lepland, A., Suuroja, S., Ausmeel, M., Szymczycha, B., Hong, W.-L., Böttcher, M. E., Virtasalo, J., Mikenberg, H., Heinsalu, A., and Roopõld, K.: Insights into the genesis and geological significance of iron-manganese precipitates in the Baltic Sea, Gulf of Finland seafloor, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7279, https://doi.org/10.5194/egusphere-egu24-7279, 2024.

EGU24-8073 | Posters on site | SSP1.3

Millennial-scale growth of (proto)dolomite in Lake Neusiedl (Austria) is consistent with Ostwald's step rule 

Patrick Meister, Susanne Gier, Erich Draganits, Peter Steier, Monika Bolka, Franz Ottner, Christoph Spötl, Dorothee Hippler, and Stephanie Neuhuber

Authigenic Mg-calcite and dolomite are currently forming in Lake Neusiedl (Neuhuber et al. 2024), an episodically evaporative shallow lake in eastern Austria (Draganits et al., 2022). Radiocarbon dating by Neuhuber et al. (2024) revealed average ages of 200 to 3700 cal yr BP, reflecting extremely slow precipitation rates. The relatively high ages of fine-grained crystals agree with high radiocarbon ages of dolomite from Deep Springs Lake (California; Peterson et al., 1963). Such comparably high ages are commonly explained by the slow formation of dolomite due to its high kinetic barrier. Close examination by transmission electron microscopy (Meister et al., 2023) revealed concentric zones of Mg-rich carbonate replacing less Mg-rich precursors. However, no considerable progress in ripening has been noticed in older layers buried below 30 cm depth, which are no longer affected by sediment reworking (Fussmann et al., 2023). It appears that ripening of the metastable phase to the stable phase does not occur as long as the porewater remains supersaturated with respect to a metastable Mg-calcite phase. Ripening of Mg-calcite to protodolomite and ordered dolomite may however occur at the sediment-water interface, where the bottom water becomes episodically undersaturated with respect to Mg-calcite. Fussmann et al. (2023) observed a drop in pH in the benthic boundary layer, which can be caused by the release of acidic fermentation products and aerobic respiration.

Ripening due to episodic undersaturation of water with respect to a metastable Mg-calcite phase is consistent with a model of dolomite formation under conditions fluctuating between supersaturation and undersaturation with respect to the metastable phase, conforming to Ostwald’s step rule. This effect has recently been reproduced using density function theory (Kim et al., 2023). This model could also explain the formation of nano-domains of ordered dolomite in coherent crystallographic orientation within the protodolomite due to oscillating conditions at the recrystallization front (Meister et al., 2023). The case of authigenic carbonate formation in Lake Neusiedl exemplifies that the model of dolomite formation under fluctuating hydrochemical conditions is well applicable to natural conditions in modern, as well as ancient, environments.

 

Draganits, E. et al. (2022) Lake Neusiedl Area: A Particular Lakescape at the Boundary Between Alps and Pannonian Basin. In: Embleton-Hamann, C. (ed.), Landscapes and Landforms of Austria. World Geomorphological Landscapes. Springer, Cham, pp. 207-222.

Fussmann, D. et al. (2020) Authigenic formation of Mg-Ca-carbonates in shallow alkaline water in Lake Neusiedl, Austria. Biogeosciences 17, 2085–2106.

Kim, J. et al. (2023) Dissolution enables dolomite crystal growth near ambient conditions. Science 382, 915–920.

Meister, P. et al. (2023) Nanoscale pathway of modern dolomite formation in a shallow, alkaline lake. Cryst. Growth Des. 23, 3202–3212.

Neuhuber, S. et al. (2024) Radiocarbon ages of microcrystalline authigenic carbonate in Lake Neusiedl (Austria) suggest millennial-scale growth of Mg-calcite and protodolomite. Sedimentology in press.

Peterson, M.N.A. et al. (1963) Radiocarbon studies of recent dolomite from Deep Spring Lake, California. J. Geophys. Res. 68, 6493–6505.

How to cite: Meister, P., Gier, S., Draganits, E., Steier, P., Bolka, M., Ottner, F., Spötl, C., Hippler, D., and Neuhuber, S.: Millennial-scale growth of (proto)dolomite in Lake Neusiedl (Austria) is consistent with Ostwald's step rule, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8073, https://doi.org/10.5194/egusphere-egu24-8073, 2024.

EGU24-8190 | Orals | SSP1.3

Understanding the origin of dolomite in the sedimentary record: the contribution of clumped isotope thermometry. 

Stefano Bernasconi, Ricarda Rosskopf, Nathan Looser, and Jordon Hemingway

The formation of dolomite in the sediments of the Sabkha of Abu Dhabi was the subject of Judy’s PhD thesis and the question of the origin of dolomite remained at the center of her scientific interests throughout her career. The main focus was on the influence of microbial activity on dolomite formation, both in the field and through laboratory experiments. Over the years, Judy’s contributions particularly advanced our understanding of the role of microbes in the formation of dolomite.

With the development of clumped isotope geochemistry, a new tool is now available to better characterize the conditions leading to the formation of dolomite in the geological record. This tool exploits the preference of13C-18O bonds in carbonate molecules to form with decreasing temperature and provides a thermometer that can be used to constrain the formation temperature and the oxygen isotope composition of the fluids involved in the precipitation of dolomite. The interpretation of dolomite clumped isotopes in the geological record, however, is complicated by the fact that early-diagenetic dolomite is generally poorly ordered and non-stoichiometric, and it converts to a more stable form during diagenesis. In this contribution we will present case studies from the Alps to show how the original clumped isotope compositions of dolomite are modified during diagenesis under different thermal regimes, and we will discuss the preservation of clumped isotope signatures in dolomite.

How to cite: Bernasconi, S., Rosskopf, R., Looser, N., and Hemingway, J.: Understanding the origin of dolomite in the sedimentary record: the contribution of clumped isotope thermometry., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8190, https://doi.org/10.5194/egusphere-egu24-8190, 2024.

EGU24-9000 | ECS | Orals | SSP1.3

Baltic Sea ferromanganese concretion growth rates and conditions 

Renata Majamäki, Lotta Purkamo, Jenni Hultman, Joonas Wasiljeff, Eero Asmala, Pirjo Yli-Hemminki, Kirsten Jorgensen, Karoliina Koho, Jukka Kuva, and Joonas Virtasalo

The transition to renewable energy and the acceleration of technology demand vast amounts of hi-tech metals that are critical in green energy technology. Due to increasing demand for hi-tech metals, rising interest in mining from more unconventional sources, such as the seafloor, is inevitable. Ferromanganese concretions, which are centimeter-scale accumulations of iron and manganese oxides, are common in the Baltic Sea. In addition to iron and manganese, concretions contain hi-tech metals, such as cobalt. The Fe-Mn concretions are important reaction surfaces for diverse microbial communities, and they regulate metal and nutrient cycling in the concretions. Extraction of Fe-Mn concretions from the Baltic Sea could impact the seafloor ecosystem, biogeochemical cycling of elements, concretion growth, and recovery. This study provides information on Baltic Sea Fe-Mn concretion growth rates and conditions in laboratory experiments.

The ferromanganese concretions were collected from the Baltic Sea during May and June 2022 for a 12-week laboratory incubation and metal tracer experiments. Triplicate concretion samples and one abiotic control sample were collected into bottles containing artificial brackish seawater and incubated in the dark at +5 °C in an orbital shaker at 100 rpm to imitate seafloor conditions. Bottles were sampled at the beginning and the end of the 12-week incubation experiment. We assessed the concretion growth with X-ray computed tomography and freshly formed concretion material with a scanning electron microscope. We analyzed the headspace methane concentrations and pH of the incubation solution. We measured phosphorus and metal (Mn, Fe, Co, V, Ni, Zn, Mo) concentrations of the incubation solution with triple quadrupole ICP-MS.

The results provide new information on the growth rates and conditions of Fe-Mn concretions. It was confirmed that concretions grew in laboratory conditions, and new growth was as much as 10 µm in 12 weeks. Headspace methane concentrations decreased in all samples during incubation, but least in abiotic controls, where the microbial activity was eliminated. The microbes living on the surface of concretions utilized methane, indicating that concretions have methanotrophic communities. Incubation solutions’ metal analysis showed that metal concentrations increased more in the abiotic controls than in biotic triplicates after a 12-week incubation, thus metals dissolved from concretions into the incubation solution faster without the activity of microbial communities. We suggest that microbes occupying the concretions have an important role in the concretions’ growth and the factors affecting the accumulation and release processes of metals.

This work was supported by the Finnish Natural Resources Research Foundation and the Research Council of Finland (Fermaid project, grant 332249).

How to cite: Majamäki, R., Purkamo, L., Hultman, J., Wasiljeff, J., Asmala, E., Yli-Hemminki, P., Jorgensen, K., Koho, K., Kuva, J., and Virtasalo, J.: Baltic Sea ferromanganese concretion growth rates and conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9000, https://doi.org/10.5194/egusphere-egu24-9000, 2024.

EGU24-9689 | Orals | SSP1.3

The intriguing hypothesis of a modern “Rosengarten” in the subsurface of the deep Ionian Basin 

Angelo Camerlenghi, Christian Huebscher, Aaron Micallef, Claudia Bertoni, Giovanni Aloisi, and Johanna Lofi

From 2016 to 2020, Judy McKenzie joined the community of COST Action CA15103 - Uncovering the Mediterranean salt giant (MEDSALT) to verify her hypothesis that an ongoing dolomitization front exists in the pelagic sediments overlying Messinian evaporites below the Messina Abyssal Plain, in ~4000 water depth in the Ionian Sea, central Mediterranean. Legacy scientific ocean drilling data from DSDP Leg 42A, Site 374 reveal a 25 m-thick latest Miocene dolomitic mudstone capped by 8.5 m of earliest Pliocene dolomite above gypsum/dolomitic mudstone cycles and anhydrite and salts. The Pliocene dolomite is made of dolomicrite with an unusual crystal morphology, suggesting diagenetic replacement of the original pelagic calcite ooze. The underlying latest Messinian dolomitic mudstone with minor gypsum layers contains Ca-rich dolomite with white spherules of lüneburgite. DSDP Site 374 shipboard interstitial water geochemical profiles further indicate that saline brine is diffusing upwards into the early Pliocene dolomicrite. A significant decrease in sulfate concentration suggests ongoing bacterial sulfate reduction, whereas the chloride profile remains constant.

Following discussion and brainstorming with Judy, a geophysical site investigation cruise on the RV Meteor was organized by the University of Hamburg. Cruise M-144 was conducted in 2018 with a multi-channel reflection seismic survey centered at DSDP Leg 42A, Site 374 using a 6 kjoule sparker source and a digital 144-channel streamer with an active length of 600 m. The objectives of the cruise were to:

  • Obtain a detailed seismic stratigraphy in the surrounding of DSDP Leg 42A, Site 374, which was targeted as re-occupation Site within IODP Proposal 857C - The demise of a salt giant: climatic-environmental transition during the terminal Messinian Salinity Crisis (Claudia Bertoni and co-workers);
  • Estimate the lateral dimensions of the combined dolomite/evaporite lithologic units in the lonian Sea.

Objective 1 was achieved, and the drilling proposal supported by the R/V Meteor Site Survey was forwarded by the Science Evaluation Panel to the JR Facility Board for scheduling. Unfortunately scheduling could not happen before the end of IODP.

Objective 2 was based on the assumption that the acoustic impedance contrasts induced by the dolomitization front could be detected in relatively high-resolution seismic reflection data. In the M-144 data, the uppermost Messinian dolomite- and gypsum-bearing sediments are characterized by a package of strong and positive reflection amplitudes (High Amplitude Reflection Package, HARP). The lateral continuity of the reflections is very low and the upper boundary is quite irregular. Based on the seismic data, the areal extent of the dolomite deposit beneath the lonian abyssal plain can be estimated in a few tens of thousands km2. This would be the Rosengarten of the Ionian Sea that Judy was looking for.

This abstract will present previous and new seismic data, collected with Meteor Cruise M-199 in February-March 2024 with similar acquisition parameters to those of M-144, to further address objective 2. However, crucial sedimentological and geochemical data to validate Judy’s fascinating hypothesis can only be derived from new scientific drilling.

How to cite: Camerlenghi, A., Huebscher, C., Micallef, A., Bertoni, C., Aloisi, G., and Lofi, J.: The intriguing hypothesis of a modern “Rosengarten” in the subsurface of the deep Ionian Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9689, https://doi.org/10.5194/egusphere-egu24-9689, 2024.

EGU24-11076 | Orals | SSP1.3

Subsurface biosphere, pore water geochemistry and mineral biosignatures along the 1 Ma sediment archive of ferruginous Lake Towuti, Indonesia 

Jens Kallmeyer, Fátima Ruiz-Blas, Cynthia Henny, James Russell, Hendrik Vogel, and Aurèle Vuillemin

Ferruginous conditions prevailed in the oceans through much of Earth’s history. However, past biogeochemical cycling inferred from mineral components in ancient iron formations remain poorly constrained in terms of microbial processes prior to lithification. In Lake Towuti, Indonesia, ferruginous sediments are deposited under stratified conditions that mimic the Earth’s early oceans. Over geologic time, Lake Towuti experienced dynamic redox conditions, resulting in variable ferric and organic matter fluxes feeding microbial life at the lake floor. Although environmental conditions exert control over microbial assemblages at the time of deposition, geochemical evolution of these substrates select for specific groups of microorganisms capable of maintaining metabolic activity during entombment.

The 100 m long core retrieved by the ICDP Towuti Drilling Project allowed for investigations of the subsurface biosphere, pore water geochemistry and diagenesis of iron minerals. We established the abundance and phylogenetic distribution of microorganisms along the 1 Ma stratigraphic record, and created integrated environmental and geochemical datasets in order to identify the main taxa and metabolic features involved in sediment mineralization. Ferruginous conditions predominantly selected for Bathyarchaeia. Relevant metabolisms identified from metagenome-assembled genomes indicated sulfur transformation and (homo)acetogenesis, suggesting that heterotrophic dark carbon fixation and cryptic sulfur cycling linked to iron minerals may be prominent features of microbial life in this ferruginous system.

Changes in environmental processes and conditions lead to variability in metal and organic substrate concentrations with depth, while sustaining different microbial processes in various depth intervals. Geochemical profiles reflect microbial activity after deposition and demonstrated mineral precipitation induced by microbial mineralization. Precipitation of magnetite (Fe3O4), millerite (NiS), siderite (FeCO3), and vivianite (Fe3[PO4]2 · 8H2O) from pore water constitute biosignatures of microbial iron and sulfate reduction, fermentation and methanogenesis. For example, oxygen, iron, and carbon isotopes measured on siderites enabled us to differentiate between depositional and diagenetic signals. Siderite δ18O signatures reflected in-lake hydrological fluctuations. Low negative δ56Fe values recorded periods of water column stratification and oxygenation events, with minor diagenetic redistribution. Negative δ13C signatures reflected incorporation of biogenic HCO3- during organic matter fermentation, whereas positive δ13C excursions indicated mass balance due to increased production of biogenic methane.

How to cite: Kallmeyer, J., Ruiz-Blas, F., Henny, C., Russell, J., Vogel, H., and Vuillemin, A.: Subsurface biosphere, pore water geochemistry and mineral biosignatures along the 1 Ma sediment archive of ferruginous Lake Towuti, Indonesia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11076, https://doi.org/10.5194/egusphere-egu24-11076, 2024.

EGU24-11488 | Orals | SSP1.3

Swiss lakes as model oceans: A mixed carbonate-siliciclastic shelf drift hosting a 10-km-long chain of 170 submerged Neolithic mounds 

Flavio Anselmetti, Dominic Perler, Simone Benguerel, Hansjörg Brem, Florence Gilliard, Jens Hornung, Thomas Keiser, Urs Leuzinger, Sebastian Schaller, Sönke Szidat, Hendrik Vogel, and Martin Wessels

Judith McKenzie contributed pivotal studies in using lacustrine sedimentary systems as natural analogues for the much larger marine environment. In this context, she introduced marine depositional processes and concepts to lakes, and in turn, used their smaller dimensions and more controllable boundary conditions to gain more insights into the controls of lithological and geochemical signals in any sedimentary system. One example of using this approach is the study of the prograding mixed carbonate-siliciclastic shallow-water shelf of Lake Constance, that is characterized by endogenic carbonate production ('lacustrine chalk'), water currents, progradation and related drift deposits, as they also have been investigated in the marine domain. A recent bathymetric survey of Lake Constance revealed ~170 mysterious mounds composed of loosely deposited rocks aligned in a ~10-km-long chain along the southern Swiss shoreline of Lake Constance in a water depth of 3–5 m. The mounds are 10–30 m in diameter and up to 1.5 m high. Over their entire length of occurrence, the mounds are estimated to be composed of ~60 million individual boulders, with a total weight of ~78,000 t. A ground penetrating radar (GPR) survey showed that the mounds are not linked to the glacial substrate but were rather deposited artificially on the edge of a prograding shelf composed of mixed carbonate-siliciclastic Late Glacial to Holocene lake sediments. Here, we present the results of a coring campaign with four piston cores along a GPR transect across one of the mounds. The cores recovered the full postglacial sedimentary succession all the way into the basal till that is overlain by lacustrine sediments dating back to ~14,400 cal. BP. The four cores are merged into a ~12.4-m-long composite section reflecting continuous sedimentation from the siliciclastic-dominated Late Glacial to the carbonate-rich Late Holocene. The stratigraphic horizon representing the mound's construction was radiocarbon-dated to ~5,600–5,300 cal. BP, placing them in the Neolithic period. This age was confirmed by radiocarbon dating of wood samples collected during underwater excavation of the mounds. Geochemical analysis of the Holocene sedimentary succession shows generally high carbonate contents (average of 69%). The interval from 5,750 to 4,950 cal. BP, a part of the mound period, is characterized by a Holocene minimum in carbonate content (average of 57%) and by larger mean grain sizes. Comparing these values to those from a recent surface-sediment depth transect indicates that this was a period of rather low lake levels, which might have favored mound construction. Correlations to nearby archaeological sites and to the general West-Central European lake-level record indicates that the mounds likely were built during a short phase of low lake levels during a general trend of climatic cooling followed by a lake-level transgression.

How to cite: Anselmetti, F., Perler, D., Benguerel, S., Brem, H., Gilliard, F., Hornung, J., Keiser, T., Leuzinger, U., Schaller, S., Szidat, S., Vogel, H., and Wessels, M.: Swiss lakes as model oceans: A mixed carbonate-siliciclastic shelf drift hosting a 10-km-long chain of 170 submerged Neolithic mounds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11488, https://doi.org/10.5194/egusphere-egu24-11488, 2024.

The pioneering work of Judith McKenzie and her colleague Kerry Kelts identified the presence of dolomites associated with the oxidation of organic material in sediments obtained from the Deep Sea Drilling Project.  This discovery led to the wide spread recognition that dolomites form in association with microbial sulfate reduction.   Later Judy’s work proposed that the microbes were more than agents of creating a suitable geochemical environments, but actually were instrumental in precipitating dolomite.  This work stimulated the research of many, but the questions have always arisen as to what degree microbial processes are responsible for dolomite formation and other carbonate minerals in the ancient record.  Some have proposed different geochemical indices such as carbon or magnesium isotopes or the concentration of certain elements, maybe diagnostic of microbial processes.  However, these tools frequently provide equivocal evidence and therefore are not definitive. In this presentation we provide several examples of the use of a new geochemical tool, the dual clumped isotope proxy (Δ47 and Δ48).  Deviations from equilibrium, particular of Δ48 values, provide strong evidence of the influence of different mechanisms of the precipitation of dolomite and calcite.  In this presentation we present several examples in which the dual clumped isotope proxy has been employed.  These include not only dolomites, but also meteoric LMC calcite cements, previously believed to have form without the influence of microbial processes.  While the dual clumped proxy may also yield equivocal results, it will be a welcome addition to the tools used to understand the roles of microbes during carbonate precipitation.

 

How to cite: Swart, P. and Lu, C.: Identification of microbial influences on carbonate precipitation using dual clumped isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12046, https://doi.org/10.5194/egusphere-egu24-12046, 2024.

EGU24-12162 | Posters on site | SSP1.3

Dolomite formation in Jurassic carbonate platforms of Southern Germany 

Inigo A. Müller, Marion Peral, Perach Nuriel, and Philippe Claeys

During the Jurassic, southern Germany was covered by a shallow sea environment with active formation of carbonate platforms. As these platforms never experienced extreme pressure and temperature conditions due to deep burial or metamorphic overprint from nearby orogeny, we expect them to preserve relatively pristine formation fabrics. Still the top of these mainly limestone buildups are dolomitized and it is not well understood how this dolomitization proceeded.

We study the origin of the dolomitization process of these Jurassic platforms with microscopic cathodoluminescence imaging to visualize different formation events, clumped isotope thermometry to derive the formation temperature and with the analysis of the elemental concentration distribution by µ-XRF we aim to obtain new insights on the formation process and the origin of the precipitation fluid.

How to cite: Müller, I. A., Peral, M., Nuriel, P., and Claeys, P.: Dolomite formation in Jurassic carbonate platforms of Southern Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12162, https://doi.org/10.5194/egusphere-egu24-12162, 2024.

EGU24-13688 | ECS | Posters on site | SSP1.3

Carbonate Mineralization Related to Weathering of Mafic and Ultramafic Rocks in the Pali Aike Volcanic Field, Extra-Andean Patagonia, Chile 

Carolina Henriquez, Mauricio Calderon Nettle, Leonardo Cury, Paulo Quezada, and Anelize Bahniuk

On geological timescales, the volume of CO2 in the atmosphere is influenced by processes such as silicate weathering. In particular, the weathering of basaltic rocks increase the availability of divalent cations such as Mg2+ and Ca2+ in natural waters enabling carbonate formation under atmospheric conditions. Therefore, the existence of carbonate deposits in basaltic provinces provides an excellent opportunity to contribute for the regional environmental record. The Pali Aike Volcanic Field consist of basaltic rocks that covers an area of ca. 4500 km2 in southernmost South America, which were sourced from a deep Mantle source since ca. 4 Ma until the Holocene. The Laguna Timone is a maar filled by a brine developed after explosive volcanic eruptions and constitutes an endorheic hydrological system where carbonate precipitation (calcite and magnesium calcite) is controlled by enrichment of Ca2+ and Mg2+ ions released during the weathering of alkaline basalts. X- ray fluorescence analyses in basaltic rocks reveal high concentration of elements such as CaO (9.73 - 10.57 wt.%) and MgO (9.49-12.76 wt.%).  X-ray diffraction results verify that basalts contain pyroxene (Na, Ca) (Mg, Fe, Al) (Al, Si)2O6, olivine (Fe, Mg)2SiO4 and plagioclase NaAlSi3O8-CaAl2Si2O8 which are suitable phases for the mineral carbonation process. The δ13C DIC values of lake range between −12‰ and −16‰ while for the water of the river values of -7‰. These isotopic ratios are associated to three possible sources/processes: weathering of silicates by carbonic acid, atmospheric CO2 and degradation of organic matter. Furthermore, Sr isotope ratios of carbonates (tufa fragments and thin crust in pebbles) define a range between 0.70408 and 0.70475 which is discussed on basis of the data of basaltic rocks (0.70316 to 0.70351) and top soils (0.705382) in the PAVF. Although the Sr isotope ratios of carbonates are indicative of their derivation from the weathering of basalts an exogenous input from relatively enriched 87Sr material is required, this could be associated to 87Sr leached from the top soils and transported by strong wind. Contrastingly a carbonate vein preserved in the tuff ring deposit of the maar has Sr isotope ratios ranging from 0.70265 to 0.70314, similar to the compositional range of the Mantle xenoliths (0.70264 to 0.70431) and basalts. These data indicate that primary sources of carbonates in the lake are related to in-situ weathering of mafic and ultramafic rocks.

How to cite: Henriquez, C., Calderon Nettle, M., Cury, L., Quezada, P., and Bahniuk, A.: Carbonate Mineralization Related to Weathering of Mafic and Ultramafic Rocks in the Pali Aike Volcanic Field, Extra-Andean Patagonia, Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13688, https://doi.org/10.5194/egusphere-egu24-13688, 2024.

EGU24-13960 | ECS | Posters on site | SSP1.3

Sedimentological and geochemical aspects of the Botijuela travertine systems , Antofalla Salar- Central Andes, Argentina. 

Guido Ezequiel Alonso, Leonardo Fadel Cury, and Tatiana Mariel Stepanenko

Carbonate accumulation processes in modern non-marine systems producing tufa and travertine deposits have gained relevance in recent years due to their importance as possible analogues to the hydrocarbon reservoirs of the Brazilian and African Pre-Salt. The biotic/abiotic genesis of these carbonates is related to the fact that these rocks create favorable situations for the proliferation of benthic microbial communities, which can influence the genesis of travertine and/or its final form. The aim of this study is to characterize the carbonate deposits and the biotic influence in the Botijuela travertine systems, located on the western margin of the Salar de Antofalla in the Puna region of Argentina. Descriptions of morphological features and sedimentary facies in the outcrops, thin-slice petrography, mineralogical analysis by X-ray diffraction (XRD), chemical analysis by X-ray fluorescence (XRF), and stable isotopes of C and O (V-DPB) were done. The Botijuela was divided into two active systems: Vega Verde and Vega Blanca. The vent of the first one is a conical mound (~15m) with a length of 530 m, and the second one is a fissure ridge with fractures with a length of 325m, also with two fossilized travertine systems, named I and II. At the proximal depositional zone of Vega Verde, the system presents carbonate facies of mudstones with bubbles, shrub-boundstones, and oncoidal (~0.5cm diameter) rudstones. The fractures of Vega Blanca in the proximal zone present halite and subsequent development of carbonate pools (transversal 2–7 cm) and big oncoids (~2 cm in diameter). Dams and barrages in the pools present botryoids in areas that show subaerial exposure. Oncoids and dendriform shrubs are well developed in the proximal-intermediate depositional zones in low-slope areas. Intermediate zones of both systems are characterized by higher-energy carbonate facies: crenulated mudstones, oncoidal grainstones, and rudstones. The distal area of Vega Verde presents rudstones with detrital fragments, diatoms, and ostracods that interbed with siliciclastic sediments of the Antofalla Salar basin. Vega Blanca presents bigger (~15cm) transversal carbonate pools with oncoids and botryoids at the dams. Mineralogically, the systems are mainly calcite, and calcite low in Mg. Geochemically, Vega Verde shows a content of CaO of ~51.05% and Vega Blanca ~46.63%, with average loss of ignition values of ~40% for both. Vega Verde proximal zone is characterized by a high Fe-As-Pb content (Fe2O3 ~4.3%, Pb-As 0.5 to 1.7%) with an isotopic signature of δ13C (1.97-10.84) and δ18O (-0.67-8.91). In comparation, Vega Blanca systems show averagely higher values of SiO2 (I~10.79% -, II~5.17%) and Na2O (I~ 0.32; II~1.47%), with isotopical signatures for system I of δ13C (5.31~14.78) and δ18O (-4.86~ -0.24), for system II of δ13C (6.34~15.36) and δ18O (-3.20~ -0.71). Signatures indicate a water hypogene origin with δ13C fractionation enrichment towards the Antofalla basin. Geochemical data allows us to infer that the systems have a different water origin. Overall, high-resolution facies analysis of travertine systems and their integration with their geochemical framework and tectonic setting constitute a step forward regarding the environmental distribution of microbially related deposits and the comprehension of their main constraints.

How to cite: Alonso, G. E., Fadel Cury, L., and Stepanenko, T. M.: Sedimentological and geochemical aspects of the Botijuela travertine systems , Antofalla Salar- Central Andes, Argentina., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13960, https://doi.org/10.5194/egusphere-egu24-13960, 2024.

EGU24-14127 | ECS | Posters on site | SSP1.3

A multi-method approach to understand the origin of lacustrine tufa deposition in Lago Sarmiento (Chilean Patagonia)  

Paulo Quezada, Leonardo Fadel Cury, Mauricio Calderón, Carolina Henríquez, Joicy Micheletto, Nicolás Bruna, José Manuel Pérez-Donoso, Gustavo Barbosa Athayde, and Anelize Bahniuk Rumbelsperger

The study focuses on the deposition of freshwater lacustrine tufa in recently deglaciated areas, specifically in Lago Sarmiento. Lago Sarmiento is a large (water volume of ca. 9 km3 and a maximum depth of ca. 310 m), alkaline and oligotrophic lake situated on folded, mudstone-rich turbiditic deposits from the Upper Cretaceous. The lake margin features a semicontinuous tufa section, reaching up to approximately 10 meters in thickness. This section comprises variably amalgamated tufa mounds that can merge into terraces or be arranged as isolated mounds, domes, and V-shaped build-ups of metric sizes. The deposits are irregular, displaying a clotted to slightly dendritic fabric, and high porosity. Vugs within them are filled with authigenic materials (peloids and gastropods) and terrigenous grains (quartz + plagioclase ± Fe-Mg silicates). Microbialites records are discernible at the microscale within the tufa framework. These records consist of variably micritized and/or eroded shrubs composed of fascicular Mg-calcite (mostly 6 - 8.5 mol% MgCO3) encrusting filamentous structures interpreted as formed after the calcification of EPS around radially organized cyanobacteria of the genus Rivularia, as deduced from 16S rRNA analysis in a microbial mat sample. Scant framboidal pyrite is observed in SEM images, suggesting minimal contributions of sulfate-reducing bacteria to carbonate precipitation. Stable isotope analysis of the tufa (δ13C and δ18O) and lake waters (δ2H, δ18O, and δ13C-DIC) indicates that the positive δ13C tufa composition results from variable amounts of CO2 degassing and microbial photosynthesis over a lake DIC pool that remained near isotopic equilibrium with atmospheric CO2. The slightly negative δ18O tufa composition is interpreted as precipitation during warm/dry periods in the Holocene. Lake water chemistry is characterized by relatively low Mg/Ca molar ratios (0.51 – 1.8), intermediate alkalinity (6 – 11.6 meq/L), and low Ca/Alk ratios (0.1 – 0.59 meq/L). In lakes with similar water chemistry, the supply of Ca+2 and Mg+2 is required to achieve carbonate saturation, e.g., through groundwater discharge. A distinctive record of tufa filling fractures in the mudstones that compose the bedrock is identified in the uppermost portions of the lacustrine tufa section, resembling a seepage system that fed the lake. The putative "seepage carbonates" include thicker infills (up to 20 cm) with microfabrics similar to lacustrine tufa, as well as thin (> 2 cm) and laminated cements with syntaxial crystal growth, arranged as interconnected vein-like structures. The "seepage carbonates" exhibit higher aragonite content, Sr/Ca ratio, and lower content of Mg in calcite than the lacustrine tufa. However, the similar δ13C and δ18O composition among both groups suggest the precipitation of the former in sub-lacustrine conditions. In-situ 87Sr/86Sr analysis of lacustrine tufa formed in opposed margins of the lake reveals strong heterogeneity in the source of Sr, with 87Sr/86Sr compositions spanning between those of the bedrock (~0.7075) and Holocene volcanism in southern Patagonia (~0.7050). These findings indicate complex interactions between intrabasinal and extrabasinal sources, climate, and microbial mediation that influenced the multi-episodic growth of the tufa deposits after the local retreat of the glaciers approximately 12.5 ka BP.

How to cite: Quezada, P., Fadel Cury, L., Calderón, M., Henríquez, C., Micheletto, J., Bruna, N., Pérez-Donoso, J. M., Barbosa Athayde, G., and Bahniuk Rumbelsperger, A.: A multi-method approach to understand the origin of lacustrine tufa deposition in Lago Sarmiento (Chilean Patagonia) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14127, https://doi.org/10.5194/egusphere-egu24-14127, 2024.

EGU24-14614 | ECS | Posters on site | SSP1.3

Geochemical and microbiological signatures in the Vega Verde carbonate system, Botijuela, Puna Argentina. 

Tatiana Stepanenko, Guido Alonso, Anelize Bahniuk, and Leonardo Cury

      Botijuela travertine system is located at the western edge of the Salar de Antofalla at 3433 meters above sea level, the area shows several hot springs still active and several fossilized carbonate deposits. One of the main outcrops of this area is Vega Verde, which develops in a north-south direction where the carbonate deposits start from a vent and reach the Salar de Antofalla basin. In this place, it was possible to observe the development of several microbial ecosystems: non-lithified and lithified microbial mats in the closest area to the vent, as well as cyanobacterial biofilms and lithified stromatolites in the mixing zone between freshwater and thalassic water. In this work, we present the geochemical and mineralogical characterization of these microbial ecosystems. Mineralogically, the lithified ecosystems were composed mainly of calcite, and a less extended Mg-bearing calcite, aragonite, gypsum, and halite. Stable Isotopes C & O analyses showed that the samples from the vent presented an isotopic signature related to hydrothermal origin with δ13C (2,05 – 7,82) and δ18O (-6,59- -9,77) values. While the stromatolite from the Salar de Antofalla (in the mixing zone) showed high δ18O (0,8-1,12) and δ13C (7,63-13,26) values, which suggests that the evaporation process is the main fractionation force.   Although is considered that the main processes driving the travertine mineral precipitation are degassing and evaporation, petrological and SEM analyses showed that microbial activity appears to be contributing to the sedimentological textures of Vega Verde samples rocks. Moreover, the mineral morphologies and carbonate growth structures found in the SEM rock samples were also found in the in vitro carbonate precipitation experiments, but exclusively when microbial mats were present, and not in the negative control. These results suggest a strong influence of hydrothermal flows, evaporation process, and microbiological mediation during the Vega Verde carbonate systems formation.

How to cite: Stepanenko, T., Alonso, G., Bahniuk, A., and Cury, L.: Geochemical and microbiological signatures in the Vega Verde carbonate system, Botijuela, Puna Argentina., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14614, https://doi.org/10.5194/egusphere-egu24-14614, 2024.

The formation of leaf compressions is dependent on the type of sediment in which the leaves are buried and on burial depth because greater burial depth leads to a more anoxic environment conducive to fossilization. Recent research has hypothesized that the presence of a microbial biofilm on leaf surfaces in the early stages of decay also enhances preservation. In decaying leaves, the biofilm community is likely influenced by the same factors: sediment type and burial depth. Here we investigate experimentally the microbial community composition of microbial biofilms formed on floating and buried leaves of living Ginkgo in four sediment types—montmorillonite clay, kaolin clay, quartz sand, and pond mud. Leaves were placed in aquariums with pond water under identical light conditions and room temperatures for three months. The leaves, sediments, and pond water were then evaluated with 16S and ITS sequencing to identify the bacterial and fungal communities. We found that the biofilms on the floating and buried leaves differed in their basic microbial community composition. The leaves buried in the kaolin clay showed the most distinctive microbial communities, while the montmorillonite clay buried leaves contained several genera noted for biomineralization. In general, the buried leaves had microbial communities that were more diverse than those on the floating leaves and richer in anaerobic microbes and biomineralizers. These results suggest that biofilms form best in very fine-grained sediments with low organic content, such as kaolin and montmorillonite clays, and under burial conditions fostering anaerobic environments and the incorporation of minerals that enhance biomineralization on leaf surfaces. Our results provide new insights into the role of microbial biofilms and microbe–sediment interactions in the early stages of leaf fossilization.

How to cite: Palmer, B., Karacic, S., Bierbaum, G., and Gee, C.: Deciphering Fossilization Pathways: Sediment Composition Impacts Biofilm-Forming and Biomineralizing Microbial Communities in Early Stages of Leaf Taphonomy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14998, https://doi.org/10.5194/egusphere-egu24-14998, 2024.

Judith McKenzie's scientific pursuit focused on comprehending the processes that lead to observable phenomena in the geological record. She consistently emphasized to students and colleagues the fundamental importance of this understanding before delving into any attempt to use proxies. In the late nineties, Judy joined us for a field trip in Patagonia, where we conducted fieldwork in the Maquinchao Basin, Argentina. This location hosts both living and fossil microbialites, presenting a unique opportunity to investigate their formation processes—a goal aligned with Judy's scientific philosophy.

Fossil microbialites, distinguished by their globular and cauliflower shapes, populate a continuous palaeoshoreline of a former lake at an altitude of 830 m. Meanwhile, their living counterparts thrive exclusively in the tranquil waters of sheltered or meandering sections of the Maquinchao River. To unravel the intricate interplay between environmental and biological factors governing their development, we sampled and studied living microbialites and their host waters. Contemporary microbialites appear exclusively in freshwater environments with elevated Ca2+ levels. Microscopic inspection reveals heightened photosynthetic organisms in the upper green layer, associated with crypto/microcrystalline calcite (nanoglobules), compared to the lower beige-white biofilm. The latter contains more low-Mg calcite (rhombohedra) precipitates, forming millimeter-sized aggregates in the underlying anoxic layer. While sulphate-reducing bacteria are present throughout the mat, their abundance is more notable in the lower beige-white layer, always associated with Mg calcite.

Distinct conditions, such as low salinity and low-turbidity water, coupled with microbial (photosynthetic and heterotrophic) activity, emerge as pivotal factors promoting low-Mg calcite precipitation in the Maquinchao Basin. Notably, these conditions sharply contrast with those proposed for recently described lacustrine microbialites at high altitudes in the subtropical and tropical Andes, as well as in Chilean Patagonia. These observations underscore the significance of geomicrobiological studies in discerning proxies for the hydrological conditions prevailing during the formation of freshwater microbialites.

How to cite: Ariztegui, D.: Unlocking the Formation Dynamics of Modern Microbialites: A Geomicrobiological Study in the Maquinchao Basin, Argentina, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15945, https://doi.org/10.5194/egusphere-egu24-15945, 2024.

EGU24-16540 | ECS | Orals | SSP1.3

Morphology-Driven Magnetic Characteristics of Shallow-Water Ferromanganese Concretions 

Joonas Wasiljeff, Johanna Salminen, Andrew Roberts, Pengxiang Hu, Maxwell Brown, Jukka Kuva, Sari Lukkari, Ester Jolis, Atko Heinsalu, Wei-Li Hong, Aivo Lepland, Sten Suuroja, Joni Parkkonen, and Joonas Virtasalo

Ferromanganese concretions, ubiquitous both in deep ocean environments and shallow-water coastal regions worldwide, are the subject of renewed scientific interest due to their multifaceted importance as underwater habitats, critical raw material sources, and invaluable repositories of paleoceanographic information. The magnetic properties of ferrimagnetic minerals within concretions, as well as the origins of their natural remanent magnetization, represent areas of study that are still in their early stages of exploration. Recent findings have unveiled the role of biogenic magnetite in the development of biogeochemical remanent magnetization within deep ocean crusts and nodules, pointing to the influence of microbial catalysis in their precipitation. While extensive research on magnetic properties of deep ocean Fe-Mn deposits has been conducted, similar investigations in fast-growing shallow-water concretions have remained notably absent. Furthermore, the specific mechanisms governing the formation and (bio)mineralization of diverse concretion morphotypes (crust-like, discoidal and spheroidal) in shallow-water setting remain enigmatic.

Our work focuses on ferromanganese concretions in shelf areas and seas, with samples from the the Baltic Sea. We report here the magnetic characteristics, microstructure, and origin of Baltic Sea concretions, which sheds light on their formation processes and environmental implications. To achieve this, we combined nano- and micro-computed tomography imaging, electron microscopy, micro-X-ray fluorescence spectroscopy, and a suite of detailed magnetic property investigations. Spheroidal concretions are prevalent in many parts of the coastal Baltic Sea and contain a higher proportion of fine-grained magnetite with evidence of bullet-shaped magnetofossils produced by magnetotactic bacteria. Bullet-shaped magnetofossils are usually produced in eutrophic and less oxic environments, as supported by the possible presence of rhodochrosite, which indicates diagenetic Mn release from surrounding sediments, especially in deeper water settings. In contrast, crust and discoidal concretions in shallower waters contain higher proportions of detrital (including magnetically hard) minerals, which reflects an increased continental influence. Microstructural analysis of the concretions reveals multiple growth stages, with laminated, columnar, and dendritic structures indicating varying hydrodynamic and depositional conditions. In general, spheroidal concretions seem to form in more tranquil settings compared to discoidal and crust concretions.

Our results provide insights into the complex interplay of environmental conditions, biogenic processes, and mineralogical composition that influence ferromanganese concretion growth and magnetic properties in the Baltic Sea. We further argue that biogenic magnetite contributes globally to the remanent magnetization of shallow and deep-sea ferromanganese concretions.  

This work was supported by the Research Council of Finland (Fermaid project, grant 332249).

How to cite: Wasiljeff, J., Salminen, J., Roberts, A., Hu, P., Brown, M., Kuva, J., Lukkari, S., Jolis, E., Heinsalu, A., Hong, W.-L., Lepland, A., Suuroja, S., Parkkonen, J., and Virtasalo, J.: Morphology-Driven Magnetic Characteristics of Shallow-Water Ferromanganese Concretions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16540, https://doi.org/10.5194/egusphere-egu24-16540, 2024.

EGU24-17528 | Posters on site | SSP1.3

Modern Microbial Carbonates Deposits in South America: New insights of sedimentation and diagenesis in alkaline lakes. 

Anelize Bahhniuk, Paulo Quezada Pozo, Carolina Henriquez Valenzuela, Mauricio Calderón, Guido Alonso, and Leonardo Cury

The sedimentation in the alkaline lakes could be understood as a product of intrinsic and extrinsic factors’ interaction, where both can exert influence with alternating or progressive predominance due to the large-scale geochemical scenario, promoted by the tectonic and geomorphological settings, the climate and hydrology, the sedimentation, and the environments of deposition. Sedimentological studies of modern carbonate deposits in extreme environments provide access to a better understanding of physical-chemical reactions under the intense influence of natural conditions of desert climate, such as UV radiation, temperature variation, altitude, and heavy winds. Modern carbonate environments, where alkaline lakes are forming under comparable geomorphological, biological, climatic, volcanic, and tectonics characteristics as those during the formation of the Aptian Pre-Salt lakes on the Brazilian continental shelf, are possible analogues to improve our understanding of the physical-chemical processes involved the formation of ancient carbonate deposits. Nevertheless, it is difficult to study a single modern example, which fulfils all the criteria required to define a realistic evolutionary model for the Aptian equivalent. Thus, we have selected for our evaluation several modern alkaline lake locations, which form under variable environmental conditions, e.g., the Pantanal, Central Brazil, and Patagonia, Chile. These environments present vastly different conditions, which can furnish important insights, and taken together provide fundamental information to decipher relationships between the inorganic and organic processes involved in carbonate reservoir formation. In the Pantanal region, thousands of lakes are distributed throughout one of the largest fan river systems. Microbial activity in many of these water bodies mediates the production of carbonates associated with authigenic clay mineral precipitation, e.g., smectite. In Chile’s Patagonia Torres Del Paine region, the Sarmiento and Amarga lakes are located in an area of glacial regression, which represents an environment with recent microbialite formation in a cold and arid climate. Additionally, in this cold, arid region, Lake Pali Aike, situated in the crater of a dormant volcano, is potentially an interesting case study. Each of these three different regions is characterized by extreme environmental conditions, such as a desert climate with high temperatures during the day and very low temperatures at night, strong winds, and a high incidence of solar radiation. The primary goal of integrating studies of these three distinctly diverse environments located in varying geological settings is to develop an actualistic facies model representing the ancient conditions of the various Pre-Salt lacustrine depositional environments, ranging from deep subaqueous, intermediate subaqueous, shallow subaqueous, and subaerial systems.

How to cite: Bahhniuk, A., Quezada Pozo, P., Valenzuela, C. H., Calderón, M., Alonso, G., and Cury, L.: Modern Microbial Carbonates Deposits in South America: New insights of sedimentation and diagenesis in alkaline lakes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17528, https://doi.org/10.5194/egusphere-egu24-17528, 2024.

EGU24-17887 | Posters on site | SSP1.3

Exploring Low-Temperature Dolomite as a Biosignature 

Mónica Sánchez-Román

Carbonates are prevalent in the geologic record throughout Earth's history and are also found on Mars and within meteorites. The chemical and isotopic compositions of carbonates have been used to elucidate the composition of ancient oceans and the prevailing conditions during the development of life and its subsequent rapid evolution1-5. Carbonate mineral compositions reflect the environmental conditions under which they were formed4,5 .

 

Dolomite is particularly abundant in ancient rock formations but is scarce in modern sedimentary environments. Many ancient dolomites are suspected of being alteration products of preexisting dolomite phases rather than being originally formed, unaltered dolomites6. The geochemical and neomorphic alteration of dolomite have been studied extensively, with the principal driving forces for neomorphism being the inherent thermodynamic instability of non-stoichiometric dolomites and the surface free energy-driven recrystallization of fine crystalline mosaics to coarser crystalline6.  Recent studies have demonstrated that microorganisms can produce dolomite with a geochemical signature distinct from those formed abiotically1-4. Our research integrates field studies, state-of-the-art laboratory experiments, mineralogical, and geochemical analyses to investigate the processes and environmental conditions that control the chemical composition of low-temperature carbonates. The role of inorganic-organic interactions is evaluated in natural field laboratories and carefully controlled laboratory experiments performed under abiotic and biotic conditions.

 

In summary, the research focuses on understanding the processes and environmental conditions that control the chemical composition of low-temperature dolomite. A multidisciplinary approach, integrating field studies, laboratory experiments, microscopic, mineralogical, and geochemical analyses, is employed to investigate the role of inorganic-organic interactions in the formation of these carbonates. This work has the potential to provide insights into the development of life on Earth and the evolution of terrestrial and Martian carbonates.

 

References:

[1] Sánchez-Román M., et al. (2011) Chemical Geology 281, 143 - 150.

[2] Sánchez-Román M., et al. (2014) Scientific Reports 4, 4767.

[3] Sanchez-Roman M., et al (2023) Geochimica et Cosmochimica Acta 356, 66-82.

[4] Sánchez-Román M., et al. (2011) Geochimica et Cosmochimica Acta 75, 887-904.

[5] Li M., et al. (2021) Geology 49, 698–702.

[6] Mazzullo, S.J., et al. (1991) Carbonates Evaporites 7, 21–37.

 

 

How to cite: Sánchez-Román, M.: Exploring Low-Temperature Dolomite as a Biosignature, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17887, https://doi.org/10.5194/egusphere-egu24-17887, 2024.

EGU24-17897 | Posters on site | SSP1.3

Carbon diagenesis in dolomite- and calcite-bearing limnic sediments: A multi-phase stable isotope geochemical perspective on Lake Constance 

Patricia Roeser, Michael Böttcher, Alina Liebezeit, Ulrich Harms, Laura Epp, Ulli Raschke, David Schleheck, Iris Schmiedinger, Flavio Anselmetti, Martin Wessels, and Antje Schwalb

Placed in a carbonate-rich catchment at the northern foot of the Alps, Lake Constance is one of the largest lakes in Central Europe, and the hard water lake chemistry makes it a natural laboratory to investigate in detail the carbonate formation, preservation, and the interactions with the detrital carbonate fraction, the latter with a major dolomite component. The highly reactive lacustrine carbonates are great paleoenvironment archives - due to the climate sensitivity in their formation either as erosional sources of suspended matter or through lake internal processes; still, they are prone to diagenetic overprints that shall be considered in a major context. For that, the (post-)glacial sediment deposits were investigated up to 24 m long cores recovered from the northernmost deep portions of Lake Constance, at approximately 200 mwd. The benthic carbon cycle and mineral sources and (trans)formations, were investigated through porewaters and sedimentary solid phases analyses for stable isotope signatures (CHOS), and major- and trace element compositions.

The water isotope signatures display a trend towards lighter data with depth, indicating the development in the lake water composition with time, superimposed by diffusion processes in the sediments. The dissolved inorganic carbon (DIC) concentrations increase below the sediment-water interface and are generally higher in the postglacial sediments, indicating that mineralization rates followed the enhancement of lake productivity under milder climate conditions. The δ13C-DIC shows the lightest values in the glacial sediments and displays an enrichment in Holocene sediments, together with pore water hydrochemistry, indicative of organic matter (OM) oxidation, carbonate dissolution, and potential involvement of methane. The sulfur isotope record indicates that minor dissimilatory sulfate reduction is involved in OM degradation. Bulk carbonate C and O isotope signatures show strong variations partly induced by non-authigenic dolomite. Vertical variations in the composition of porewaters, bulk, and acid-soluble phases, in combination with SEM investigations, allow insights about the (trans)formation of authigenic mineral phases and the destruction of allochthonous carbonates, as possible modifiers of the sedimentary record.

How to cite: Roeser, P., Böttcher, M., Liebezeit, A., Harms, U., Epp, L., Raschke, U., Schleheck, D., Schmiedinger, I., Anselmetti, F., Wessels, M., and Schwalb, A.: Carbon diagenesis in dolomite- and calcite-bearing limnic sediments: A multi-phase stable isotope geochemical perspective on Lake Constance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17897, https://doi.org/10.5194/egusphere-egu24-17897, 2024.

EGU24-17981 | ECS | Orals | SSP1.3

Evaporation of seawater produces amorphous calcium-magnesium carbonate when aragonite precipitation is inhibited 

Peter Methley, Clancy Jiang, Justin Strauss, and Nicholas Tosca

As a metastable precursor to crystalline carbonate minerals, amorphous calcium-magnesium carbonate (ACMC) has been implicated in the formation of enigmatic fabrics and minerals, such as calcite microspar, fibrous cements and fabric-retentive dolomite, that characterise both modern and ancient carbonate systems (e.g. Wang et al., 2012). The detection of nanocrystals within ancient dolomicrite, using high-resolution transmission electron microscopy, strengthens this hypothesis (Meister & Frisia, 2019).

However, it has remained unclear whether natural, abiotic processes could produce ACMC, because of a requirement for extreme carbonate supersaturation. This study tests the hypothesis that – in the presence of micromolar concentrations of aqueous phosphate, which can inhibit aragonite precipitation (Roest-Ellis et al., 2021) – the evaporation of Neoproterozoic seawater may have increased alkalinity, pH, and carbonate saturation enough to precipitate ACMC in shallow-water settings.

We conducted evaporation experiments using phosphate-free and phosphate-bearing ([PO4]Total = 50 μmol/kg) synthetic seawater with Tonian composition. Solution samples, pH and alkalinity measurements were collected at regular intervals over 9-14 days. Final solids were collected and analysed using X-ray diffraction, Raman spectroscopy, and scanning electron microscopy.

Experimental data show that phosphate-bearing seawater undergoing evaporative concentration reaches increasingly high alkalinity, pH and carbonate saturation until the first solid phase forms. Analytical data indicate that ACMC precipitated during evaporation of phosphate-bearing seawater, whereas aragonite dominated in phosphate-free systems. When evaporating the water more slowly, the ACMC is observed to recrystallise into other metastable carbonate minerals – either fibrous monohydrocalcite or needles of hydromagnesite, depending on the solution’s initial Mg/Ca ratio.

These results suggest that low concentrations of species which inhibit crystalline carbonate precipitation allow extreme carbonate supersaturation to be reached upon evaporation. We speculate that this pathway may have facilitated platform-scale production of metastable precursors to syndepositional and early diagenetic dolomite in shallow-water late Proterozoic carbonate sediments, consistent with sedimentological and stratigraphic evidence for evaporation.

How to cite: Methley, P., Jiang, C., Strauss, J., and Tosca, N.: Evaporation of seawater produces amorphous calcium-magnesium carbonate when aragonite precipitation is inhibited, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17981, https://doi.org/10.5194/egusphere-egu24-17981, 2024.

EGU24-18286 | Posters on site | SSP1.3

Unraveling the early South Atlantic records: in situ 87Sr/86Sr isotopic analysis in Aptian carbonates from the conjugated margins of Brazil and Angola. 

Leonardo Cury, Kei Sato, Joicy Micheletto, Larissa Santos, Joachim Amthor, and Anelize Bahniuk

The 87Sr/86Sr ratio stands as a crucial isotopic marker for the paleogeographic and paleoenvironmental reconstruction of Aptian carbonate sequences in the offshore Campos and Santos basins in Brazil, as well as the Namibe basin in Angola. It facilitates the identification of distinct stratigraphic successions and alterations in the basin's source areas, allowing for valuable geological correlations and interpretations on both margins. Furthermore, it can indicate diagenetic processes, hydrothermal events involving chemical mobility, and textural modifications associated with regional tectonic events linked to the evolution of the South Atlantic rift.

In isotopic dilution analyses, the quality of the results is ensured by eliminating interferences and ensuring a stable signal during spectrometric reading, where the 87Sr/86Sr ratios have analytical precision between the 5th and 6th decimal place. However, samples with a significant compositional variation, such as laminations, microstructures, microveins, or even with clastic minerals, may yield scrambled distinct signals during the grinding and homogenization processes, making it difficult to recognize subtle variations. Strontium isotope analyses by laser ablation coupled to multi-collector ICP-MS Neptune Plus, obtained through the in situ 87Sr/86Sr method have great potential and broad applicability in cases where the search for gentle isotopic signal variations is relevant, such as in the study of drilling cores. By using integrated petrographic information, it has become possible to perform high-resolution analyses, addressing different components of the crystalline system, with strontium intensities ranging from 200 mg/L to ~ 6000 mg/L. The speed of the analyses, from sampling rock fragments to performing laser-based analyses, provides a large volume of results in a relatively short period of time, facilitating correlations between stratigraphic intervals.

The in situ 87Sr/86Sr method has analytical precision between the 4th and 5th decimal place, with sufficient sensitivity to characterize different groups defined by ratios in the ranges of 0.712 - 0.714 (predominantly continental), 0.710 - 0.711 (mixed), and 0.709 - 0.710 (marine influence). Its application in the study of pre-salt carbonates brings a significant advancement in recognizing the environment, and its genetic and diagenetic processes, with great potential to advance our understanding of chemostratigraphy and unravel the transition between continental and marine environments in the early stages of the South Atlantic Ocean's history.

How to cite: Cury, L., Sato, K., Micheletto, J., Santos, L., Amthor, J., and Bahniuk, A.: Unraveling the early South Atlantic records: in situ 87Sr/86Sr isotopic analysis in Aptian carbonates from the conjugated margins of Brazil and Angola., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18286, https://doi.org/10.5194/egusphere-egu24-18286, 2024.

EGU24-18784 | ECS | Orals | SSP1.3

Non-Classical Crystallization in Moon-Milk Deposits in the Nerja Cave, Spain  

Sarah Bonilla-Correa, Encarnación Ruiz-Agudo, María Pilar Asta Andrés, Lisa Huber, Concepción Jiménez de Cisneros, and Cristina Liñán-Baena

The Nerja Cave is located in an alpine folding chain, specifically in the Inner Zone of the Betic Range (SE, Spain), and it is developed within middle Triassic dolomite marbles (Carrasco et al., 1998). Its mean annual temperature is 18.1 ± 0.1 °C (Jiménez de Cisneros et al., 2021). Moon-milk deposits, a white substance present inside caves. Samples were collected in the touristic part of the cave and were characterized using synchrotron high-resolution XRD (HR-XRD), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). We detected the presence of amorphous magnesium carbonate (AMC), huntite, and dolomite. Additionally, the AMC formation and the subsequent crystallization process were studied in laboratory conditions to gain a more comprehensive understanding of the processes occurring in the cave. We performed titration experiments using magnesium and calcium chloride solutions and potassium carbonate buffers to investigate nucleation and transformation processes at elapsed times (1, 2, 7, and 14 days). The filtered solids were characterized by XRD, SEM, FTIR, Raman, and TEM. The results of these analyses highlighted the critical role of AMC in the formation of Ca-Mg crystalline carbonates.

Acknowledgment to financial support is given by the Spanish Ministry of Science and Innovation through the research project PID2021-125305NB-I00 and the project from the Junta de Andalucía through the EMERGIA research program under the grant agreement EMERGIA20_38594.

Carrasco F, Durán JJ, Andreo B, Liñán C, Vadillo I (1998) Consideraciones sobre el karst de Nerja. Karst en Andalucía 173–181

Jiménez de Cisneros, C., Peña, A., Caballero, E., & Liñán, C. (2021). A multiparametric approach for evaluating the current carbonate precipitation and external soil of Nerja Cave (Málaga, Spain). International Journal of Environmental Research, 15, 231-243.

How to cite: Bonilla-Correa, S., Ruiz-Agudo, E., Asta Andrés, M. P., Huber, L., Jiménez de Cisneros, C., and Liñán-Baena, C.: Non-Classical Crystallization in Moon-Milk Deposits in the Nerja Cave, Spain , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18784, https://doi.org/10.5194/egusphere-egu24-18784, 2024.

EGU24-19036 | Posters on site | SSP1.3

Role of extracellular polymeric substances (EPS) in mineral precipitation in the ocean water column 

Francisca Martinez-Ruiz, Adina Paytan, Crisogono Vasconcelos, Fadwa Jroundi, Maria del Mar Abad, Victor Villasante, and Maria Teresa Gonzalez-Muñoz

The investigation of mechanisms involved in barite formation in the mesopelagic zone has served to demonstrate the importance of extracellular polymeric substances (EPS) in promoting microenvironments in which Ba can precipitate. Barite formation in the ocean was not fully understood until experimental work and observations from microenvironments of intense organic matter mineralization in the ocean water column demonstrated the role of bacteria and EPS in concentrating Ba. The organomineralization processes leading to barite formation are expected to be similar to those involved in the formation of other biominerals in which bacterial cells and EPS provide charged surfaces that bind metals inducing mineralization. Thus, EPS production plays a major role in promoting locally high concentrations of Ba leading to barite precipitation. Regarding the crystallization pathway, scanning and high-resolution transmission electron microscopy analyses have shown the occurrence of P-rich amorphous precursor phases, which supports that phosphate groups in EPS and bacterial cells are the main sites for binding Ba. These P-rich amorphous particles evolve into poorly crystallized barite and eventually into micrometer-sized barite crystals. The ubiquitous presence of bacteria and EPS in aquatic systems, and in the mesopelagic zone at depths of intense organic matter mineralization, and their inherent ability to biomineralize, make them extremely important agents in driving the Ba biogeochemical cycle. Thus, further investigating microbial processes in the open ocean is essential to better understand metal cycling. The strong link between organo-mineralization and microbial processes further supports the microbial role in biogeochemical cycles. Other than Ba, EPS may also play an important role in concentrating other metals in seawater, which still needs further investigation.

How to cite: Martinez-Ruiz, F., Paytan, A., Vasconcelos, C., Jroundi, F., Abad, M. M., Villasante, V., and Gonzalez-Muñoz, M. T.: Role of extracellular polymeric substances (EPS) in mineral precipitation in the ocean water column, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19036, https://doi.org/10.5194/egusphere-egu24-19036, 2024.

EGU24-19412 | ECS | Posters on site | SSP1.3

14C Bomb Spike Signal Constrains Microbial Mat Growth Rates 

Franziska R. Blattmann, Tomaso R.R. Bontognali, Negar Haghipour, Simon E. Rouwendaal, and Timothy Eglinton

Microbial mats are considered among the earliest forms of life to have inhabited our planet and occur in early Archean sedimentary sequences. Living mats consist of a coherent network of metabolically diverse microorganisms that produce extracellular polymeric substances, which allows them to thrive in harsh environments. Despite their importance for the study of early life on Earth and their relevance in the search for life on Mars, growth rates as well as carbon cycling of microbial mats remain unclear. Past radiocarbon (14C) studies of microbial mats show the presence of allochthonous organic particles trapped within the autochthonous biomass which complicate reconstruction of the mat growth rates (Bahniuk Rumbelsperger, 2013). In this study, millimeter-scale sampling and radiocarbon analysis was conducted on vertical profiles of microbial mats and lagoon water samples from two modern coastal sabkhas located on the Northwest and South coast of Qatar, respectively. The 14C measurements of mats from both studied sabkhas show increasing Δ14C values from the surface downwards, from an average of -25 ‰ up to a maximum 180 ‰. At the base of the mat there is an abrupt ~150 ‰ decrease in Δ14C values. This clear and shared trend between different sites and profiles shows that in both sites organic matter is predominantly being produced in situ via photosynthesis. Moreover, this 14C trend correlates with the global bomb spike carbon signal (Graven, 2015) and implies that these 45-55 mm thick mats are relatively modern structures and cannot be more than 60 - 70 years old. Therefore, the microbial mat growth rate is higher than previously estimated, suggesting that stromatolites, possibly those from earlier in Earth history, may have formed in a relatively short time. The trend also shows that most organic bound carbon is not extensively recycled within the mat. Instead, the primary source of in-situ produced organic carbon is the dissolved inorganic carbon of the lagoon water. These findings shed new light on the development of one of the earliest life forms on our planet.

REFERENCES
Bahniuk Rumbelsperger A.M., 2013. Coupling organic and inorganic methods to study growth and diagenesis of modern microbial carbonates, Rio de Janeiro State, Brazil: Implications for interpreting ancient microbialite facies development, PhD Thesis ETH Zurich, ETH No. 20984.
Graven, H.D., 2015. Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century. Proceedings of the National Academy of Sciences, 112(31): 9542-9545.

How to cite: Blattmann, F. R., Bontognali, T. R. R., Haghipour, N., Rouwendaal, S. E., and Eglinton, T.: 14C Bomb Spike Signal Constrains Microbial Mat Growth Rates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19412, https://doi.org/10.5194/egusphere-egu24-19412, 2024.

EGU24-22168 | Orals | SSP1.3

Nanoscale insights: unraveling fungal-induced precipitation of CaCO3 polymorphs for self-healing concrete 

Jean Rene Marius Tuyishime, Edith Hammer, Martí Pla i Ferriol, Karina Thånell, Carl Alwmark, and Hanbang Zou

Routine methods of concrete production contribute 9% to anthropogenic CO2 emissions and demands 2-3% energy, along with 9% water consumption. Despite these environmental costs, concrete structures frequently undergo deterioration due to unavoidable physical, chemical, and biochemical stressors, resulting in cracks that permit gas diffusion, water, and pollutants penetration, ultimately compromising its integrity and internal steel reinforcement. Microbially induced CaCO3 precipitation has emerged as a sustainable way of concrete protection and self-healing. However, the detailed mechanisms and formation of various CaCO3 polymorphs remain inadequately explored.

In this ongoing study, samples were prepared by inoculating a growth medium, containing urea and nutrients, with different fungi under diverse growth conditions. High-resolution Scanning Transmission X-ray Microscopy (STXM) in the Ca 2p energy range (340−360 eV) were employed to investigate the fungal-induced formation and chemical speciation of CaCO3 at the cellular base or interface between hypha and the surrounding ions. To discriminate potential absorption saturation effects, only spectra (NEXAFS) extracted from thin regions (≈ 30 nm) of the entire sample thickness were considered for spectral analysis. Furthermore, SEM with EDS was used to reveal morphology and elemental distribution, and composition in studied sample thin sections.

The preliminary results suggest that the samples spectra resembled those of pure calcite and aragonite, according to reference spectra. These are the most stable CaCO3 biomaterials. Notably, the intensity of weak peaks preceding each main resonance peak of the Ca L3 and Ca L2 edges were relatively smaller for aragonite-dominated spots than in calcite-dominated spots. As revealed by the spectral analysis, some fungi showed the ability to form CaCO3, predominantly in the form of either calcite or aragonite. Other fungal strains demonstrated a more heterogeneous precipitation behavior by forming both phases, albeit in distinct nano spots within the same sample. Furthermore, a few fungal species exhibited the ability to precipitate other crystalline Ca minerals, most likely CaPO4, as shown by SEM/EDS analyses.

In conclusion, the results of this ongoing investigation provided not only valuable insight on distinctive fungal behaviors in the biomineralization process, but also revealed spatial nanoscale heterogeneity in CaCO3 speciation under the same fungal conditions.

How to cite: Tuyishime, J. R. M., Hammer, E., Pla i Ferriol, M., Thånell, K., Alwmark, C., and Zou, H.: Nanoscale insights: unraveling fungal-induced precipitation of CaCO3 polymorphs for self-healing concrete, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22168, https://doi.org/10.5194/egusphere-egu24-22168, 2024.

EGU24-94 | ECS | Posters on site | SSP1.4

Sedimentology and Geochemistry of Evaporites in Bâlâ-Karakeçili Basin (SE Ankara, Central Anatolia) 

Erhan Karakuş and Erdoğan Tekin

Evaporitic precipitates exposed in the research area consist of gypsum. Seven gypsum lithofacies which massive gypsum (F1), bedded gypsum (F2), laminated gypsum (F3), nodular gypsum (F4), selenitic gypsum (F5), gypsum domes (F6) and satin-spar gypsum (F7) are recognized which are precipitated both shallow water and deep water environments in a restricted basin. Alabastrine, balatino, granoblastic and detritic textures are observed in petrographic studies. SEM/EDS analysis showed that celestite accompanied the gypsum precipitation. The strontium content of gypsum ranges between 197-22970 ppm which indicates the precipitation occured under marine conditions. Low barium content (2-129.4 ppm) indicates that there is no hydrothermal activity during gypsum precipitation, and arsenic, molybdenum and wolfram values lower than 1 ppm show that precipitation occurred under non-reductant conditions. Isotope values of δ34SSO4 range between 20.76‰ to 23.42‰ and δ18OSO4 ranges between 10‰ to 14.49‰ compatible with sulphur and oxygen values of Paleogene (Eocene-Oligocene) seawater. Furthermore, 87/86Sr values range from 0.707747‰  to 0.708558‰. These values correspond with late Eocene – early Oligocene seawater.

All data indicate that the precipitation of evaporite in the study area occurred under marine environmental conditions during the late Eocene - early Oligocene time interval, in the last phase of the regression processes of the remnant Eocene sea, as a result of the horizontal movements of the Eocene period seen almost everywhere in the Anatolian microcontinent.

How to cite: Karakuş, E. and Tekin, E.: Sedimentology and Geochemistry of Evaporites in Bâlâ-Karakeçili Basin (SE Ankara, Central Anatolia), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-94, https://doi.org/10.5194/egusphere-egu24-94, 2024.

EGU24-399 | ECS | Orals | SSP1.4

Probing large paleoenvironmental variability of Mediterranean during the Miocene-Pliocene transition via advanced multivariate statistical analysis on lipid biomarker multiproxy. 

Francesco Pilade, Michele Licata, Iuliana Vasiliev, Daniel Birgel, Francesco Dela Pierre, Marcello Natalicchio, Alan Mancini, Andreas Mulch, and Rocco Gennari

The quantitative reconstruction of paleoclimatic and paleoenvironmental conditions in regions and in time periods characterized by recurrent and significant fluctuations is challenging. An example of strong paleoenvironmental change occurred in the Mediterranean Basin across the Miocene – Pliocene boundary (5.33 Ma), marked by the restoration of normal marine conditions after the 'Lago-Mare' terminal phase of the Messinian salinity crisis. Environmental conditions during the Lago-Mare phase are still uncertain due to the controversial body fossil record, consisting of freshwater to brackish assemblages (ostracods, dinocysts, mollusks, and foraminifera), as well as marine microfossils (otoliths of marine fishes, calcareous plankton).

However, two scenarios were suggested to describe this transition: 1) a catastrophic and sudden sea level rise causing the drastic change from freshwater to marine deep environments; 2) a gradual sea level rise, characterized by a fast to gradual transition from brackish to marine environments.

To quantify the changing conditions during the Miocene–Pliocene transition, we used a multivariate statistical approach to interpret a large array of terrestrial and aquatic molecular-based indices, in a sedimentary succession of the Northern Mediterranean (Maccarone section, Central Italy). The statistical procedure was specifically developed to address the complexities emerging from the heterogeneous dataset.

An illustrative example suggests that using the TEX86, UK37’, and MBT´5ME paleothermometers, we obtained different values and trends in the changing Mediterranean during the study interval. While the study acknowledges the validity of UK37’ as a paleothermometer in variable environments, it highlights that TEX86and MBT´5ME are sometimes compromised by other sources, such as reworked sediment or other organisms that produce the same lipid inventory. In these cases, these proxies provide information about environmental processes rather different than temperatures.

Cluster analysis supports a stepwise evolution during the Miocene-Pliocene transition, besides redundancy analysis (RDA) indicates that the water column structure changed from stratified (Tetrahymanol) during the Messinian to mixed during the Zanclean. A second gradual change is instead related to terrestrial vegetation modifications, indicating a gradual coastal environment reconfiguration after a marine transgression with the distancing of the costal line and  a reduction of wetland aquatic plants signal. Finally, molecular fossils are also influenced by cyclical changes, not related to the Messinian salinity crisis demise but linked to astronomical-driven climatic cycles.

How to cite: Pilade, F., Licata, M., Vasiliev, I., Birgel, D., Dela Pierre, F., Natalicchio, M., Mancini, A., Mulch, A., and Gennari, R.: Probing large paleoenvironmental variability of Mediterranean during the Miocene-Pliocene transition via advanced multivariate statistical analysis on lipid biomarker multiproxy., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-399, https://doi.org/10.5194/egusphere-egu24-399, 2024.

EGU24-570 | ECS | Orals | SSP1.4

Tracing the origin of Lago Mare biota: ostracods and mollusks from the late Neogene of the Slavonian mountains in the southern Pannonian Basin (NE Croatia)  

Katja Mužek, Oleg Mandic, Valentina Hajek Tadesse, Mathias Harzhauser, Marijan Kovačić, Tomislav Kurečić, and Đurđica Pezelj

Lake Pannon was a huge central European long-lived endorheic lake settled in the Pannonian Basin System and surrounded by the Alps, Carpathians and Dinarides mountain ranges during the late Neogene. The rise of brackish Lake Pannon enabled establishment of specific environmental conditions which triggered a spectacular adaptive radiation of a great number of autochthonous mollusk and ostracod species. The latter species represent excellent regional paleoecological proxies and biostratigraphic markers due to their good preservation-potential and taxonomic richness. Although dominantly endemic to Lake Pannon, some of its taxa managed to migrate into the Eastern Paratethys and have also been reported from the Mediterranean. These species are restricted to the Lago Mare interval, representing the ultimate stage of the Messinian Salinity Crisis, a significant environmental perturbation characterized by massive evaporite deposition. The Lago Mare interval was apparently forced by a drainage of the Eastern Paratethys brackish water into the Mediterranean. The Bozara section is situated in the southern Pannonian Basin at the southern slopes of Mt. Papuk and carries a well-preserved benthic fauna representative of Lake Pannon. The 27 -m-thick section consists of alternating pelitic sediments and sand packages divided into 4 facies: silty marl and calcareous silt (F1), sand (F2), intercalation of sand and sandy silt (F3) and clayey silt (F4). According to the regional stratigraphic division it belongs to the Nova Gradiška Formation. We detected therein 25 ostracod and 17 mollusk taxa allowing an integrated evaluation of the depositional setting, biostratigraphic position and paleogeographic distribution pattern. The paleoecology of Bozara fauna documents a general shallowing upward trend along the section from calm deep-water sublittoral to deltaic high-energy littoral conditions. Based on presence of several biostratigraphic markers, such as the bivalve Rhombocongeria rhomboidea and the ostracod Caspiocypris pontica the stratigraphic position of the Bozara section is constrained to the Portaferrian substage (8.0-4.5 Ma).
From 16 ostracod taxa determined at species level, 10 can be found in the Eastern Paratethys deposits, whereas only 3 are shared with the Mediterranean Lago Mare. In contrast, among 12 corresponding mollusk taxa, only 4 are shared with the Eastern Paratethys, while being completely absent from the Lago Mare interval. Such a paleobiogeographic pattern suggests that the Lake Pannon outflow and faunal migration into the Eastern Paratethys, ceased distinctly before the Lago Mare phase and the corresponding migration of Paratethys biota into the Mediterranean basin.

 

How to cite: Mužek, K., Mandic, O., Hajek Tadesse, V., Harzhauser, M., Kovačić, M., Kurečić, T., and Pezelj, Đ.: Tracing the origin of Lago Mare biota: ostracods and mollusks from the late Neogene of the Slavonian mountains in the southern Pannonian Basin (NE Croatia) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-570, https://doi.org/10.5194/egusphere-egu24-570, 2024.

EGU24-2095 | ECS | Posters on site | SSP1.4

From turbidites to evaporites: the Messinian Salinity crisis record of the Tabernas Basin (SE Spain) 

Gustavo Kenji Lacerda Orita, Fernando Pérez-Valera, Jesús Soria, Enrique Gomez-Rivas, Hugo Corbi, Núria Sierra Ramirez, Jingjing Liu, and Luis Gibert

The Messinian Salinity crisis (MSC) was a major ecological crisis triggered by a combination of climatic and tectonic drivers that led to the progressive restriction of the Mediterranean, and culminated with the formation of large evaporite deposits. The Tabernas Basin (SE Spain) presents an exceptional Miocene sedimentary record, key for understanding the evolution of a turbiditic basin during the MSC. A composite stratigraphic section (>200m long) from the early Messinian to the early Pliocene shows different phases of the MSC in the Yesón Alto area (~20 km from Almeria City). Our study allows recognizing pre-evaporitic, syn-evaporitic, and post-evaporitic units. Two stratigraphic sections, one in the Yeson Alto and the other in Rambla de Lanujar were measured, sampled and documented for their petrological, geochemical and sedimentary facies characterization. Paleontological data, obtained through the analysis of foraminifera and marine macrofossils, enabled bio-stratigraphic dating. Magnetostratigraphic sampling along the pre- and post-evaporitic units was executed, although only the post-evaporitic deposits allowed the isolation of the primary Characteristic Remanent Magnetization. The preliminary results indicate that sedimentation rates during the pre-evaporitic phase were approximately four times greater than those of the correlated Abad member in the neighbouring Sorbas Basin The examined pre-evaporitic unit (90 m-thick) predominantly comprises fine-grained deposits intercalated with levels of sandstones and limestones. Abundant benthic and planktonic foraminifera, together with other marine fauna, facilitated the identification of 13 bioevents in the succession. The presence of Turborotalita quinqueloba and Orbulina taxa allows correlation with the last Messinian biozone (d) of Mediterranean biostratigraphy. Decimeter-thick beds of fossiliferous packstones/wackestones and barren mixed-siliciclastic carbonates occur toward the uppermost part of the unit, at the transition with the evaporites, indicating the initiation of evaporitic conditions preceding the deposition of the first gypsum bed. Soft-sediment deformation in these transitional beds suggests the occurrence of an important seismic event in Tabernas basins during initial stage of the MSC. The evaporitic unit in this area comprises only three cycles of massive selenitic gypsum beds intercalated with mudstones, in contrast with the Sorbas Basin, where up to 15 cycles have been described. δS analysis of these selenites reveals values expected for Miocene marine evaporites. A level with abundant marine fossils in the second inter-evaporitic level indicates at least an episode of dilution from >150gr/l to <40gr/l during the evaporitic deposition phase, where normal marine conditions prevailed. Towards the basin margins (Rambla de Lanujar section), the pre-evaporitic unit is characterized by the alternation of siliciclastic mudstones and gravity flow deposits, including boulder-grained breccias. The evaporitic unit is represented here by two beds of secondary nodular gypsum and centimetriclenite crystals forming Selenite supercones up to 2.5 m in diameter. Conformably overlying the last gypsum bed, a cyclic sequence of interbedded conglomeratic sandstones, matrix-supported conglomerates, and siliciclastic mudstones occurs. The paleomagnetic analysis reveals a reverse polarity for this unit, suggesting its correlation with the chron C3r. The presence of a fossiliferous assemblage, indicative of marine conditions with high salinity, also supports the conclusion that the post-evaporitic phase began during the Messinian times.

How to cite: Lacerda Orita, G. K., Pérez-Valera, F., Soria, J., Gomez-Rivas, E., Corbi, H., Sierra Ramirez, N., Liu, J., and Gibert, L.: From turbidites to evaporites: the Messinian Salinity crisis record of the Tabernas Basin (SE Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2095, https://doi.org/10.5194/egusphere-egu24-2095, 2024.

A simple box model is developed to access the astronomical-modulated exchange of Atlantic seawater with the Mediterranean during the Late Miocene salinity crisis. Key to the calculations is an activity coefficient that reduces the rate of evaporation as salinity increases. The model uses a narrow and shallow portal in order to get salinity to increase to saturation for gypsum, halite and the most soluble potash and magnesium salts. Flow through the Atlantic entry portal changes in direction as climate oscillates from arid to wet during each precession cycle. The model addresses the geochemical riddle of “low salinity gypsum” with calculations showing that rain and rivers supply eight times more water to the Mediterranean brine than seawater. The sulfate isotopes in gypsum come in with the ocean and those in the water of hydration in gypsum from atmospheric precipitation. The evolving chloride, sulfate, potassium and magnesium ions observed from fluid inclusions in gypsum and halite are reproduced in the calculations. The mass of computed halite is approximate to the volume of acoustically-transparent halite observed in reflection profiles. The rates of gypsum, halite and kainite precipitation diminish with time as the result of the decreasing activity coefficient and the associated reduction in the amount of Atlantic inflow. The evaporative model’s reduction in the Atlantic-Mediterranean exchange conforms with the sedimentological and geochemical observations of the gypsum deposits on margins and halite on deep basin floors.

How to cite: Ryan, W. and Raad, F.: Computations to account for composition of the Mediterranean’s Messinian gypsum and halite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3231, https://doi.org/10.5194/egusphere-egu24-3231, 2024.

EGU24-4237 | Posters on site | SSP1.4 | Highlight

Preliminary results of IODP Expedition 401, the first element of the Miocene Mediterranean-Atlantic Gateway (IMMAGE) Land-2-Sea drilling project 

Rachel Flecker, Emmanuelle Ducassou, and Trevor Williams and the IODP Expedition 401 participants

Warm and saline Mediterranean overflow today is an important driver of thermohaline circulation in the North Atlantic. In the latest Miocene, Mediterranean salinity varied dramatically as the Messinian salt giant formed. The precipitation of a ~1.5 km thick evaporite layer across the Mediterranean seafloor requires substantial changes both to the geometry of the Atlantic-Mediterranean gateway and the nature of exchange between the two basins. This salinity crisis was the consequence of on-going Africa-Eurasia collision, which formed, narrowed, and ultimately closed the two ancestral marine connections that pre-date the Gibraltar Strait. One of these connections is now preserved on land in southern Spain, the other in northern Morocco. Both the initiation of Mediterranean overflow, variations in its size and salinity, and the establishment of the present-day overflow pattern in the early Pliocene are likely to have impacted thermohaline circulation, climatic change and deep water sedimentation during the late Miocene and Pliocene.

IMMAGE (Investigating Miocene Mediterranean-Atlantic Gateway Exchange) is a land-2-sea drilling project designed to recover a complete record of Late Miocene-Pliocene exchange (8-4Ma) offshore with International Ocean Discovery Program (IODP) in both the Atlantic and Mediterranean and onshore with International Continental Scientific Drilling Program (ICDP) in Morocco and Spain. IODP Expedition 401 is the first element of the land-2-sea drilling to take place. At the time of abstract submission, Expedition 401 is at sea (December 2023-February 2024) in the process of recovering these critical records. We propose to present an overview of the sediments recovered during the expedition and initial shipboard analytical results.

How to cite: Flecker, R., Ducassou, E., and Williams, T. and the IODP Expedition 401 participants: Preliminary results of IODP Expedition 401, the first element of the Miocene Mediterranean-Atlantic Gateway (IMMAGE) Land-2-Sea drilling project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4237, https://doi.org/10.5194/egusphere-egu24-4237, 2024.

EGU24-5056 | ECS | Orals | SSP1.4

Tracing the opening and connectivity of the South Atlantic with Sr and Os isotopes 

Rafaela Cardoso Dantas, Rachel Flecker, Ian Parkinson, Maurice Tucker, Dan Palcu, Paul Meijer, André Pires Negrão, and Luigi Jovane

The temporal and geological characteristics surrounding the initiation of the Proto-South Atlantic in the Early Cretaceous are presently unclear, marked by potential marine ingressions from both the northern Tethys- and the southern-ocean, ultimately culminating in the generation of immense salt deposits. The Araripe Basin in Northeast Brazil contains crucial outcropping records of these phenomena with its origin and development intricately linked to the tectonic forces orchestrating the disintegration of the Gondwana Supercontinent. The basin underwent distinct tectonic phases, transitioning from a pre-rift continental environment to a syn-rift lacustrine setting, and finally to evaporitic systems in the post-rift/sag phase.

The post-rift stage is notably represented by the Santana Group, which chronicles significant environmental shifts, including the potential existence of a seaway linking the waters of the Tethys to the Proto-South Atlantic, intermittent marine incursions, and the presence of substantial evaporite layers. Despite extensive study, the paleoenvironment of this unit remains contentious, with hypotheses ranging from epicontinental sea to a basin with non-marine and transitional environments under marine influence.

To address this ambiguity, we employ geochemical, paleomagnetic, and isotopic records (strontium 87Sr/86Sr and osmium 187Os/188Os) as indicators of hydrological connectivity. These tools serve as invaluable aids in reconstructing the paleoenvironment during the deposition of both pre- and post-salt phases in the basin.

 

Keywords: Salt giant, South Atlantic opening, marine gateways, strontium isotopes, osmium isotopes

How to cite: Cardoso Dantas, R., Flecker, R., Parkinson, I., Tucker, M., Palcu, D., Meijer, P., Pires Negrão, A., and Jovane, L.: Tracing the opening and connectivity of the South Atlantic with Sr and Os isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5056, https://doi.org/10.5194/egusphere-egu24-5056, 2024.

EGU24-5651 | Posters on site | SSP1.4

Marine functional connectivity through the ages: geological and historical perspectives 

Konstantina Agiadi, Bryony Caswell, and Audrey Darnaude and the the Q-MARE - SEA-UNICORN workshop participants

Marine Functional Connectivity (MFC) refers to all the unimpeded flows of matter, genes and energy that are caused by the movements of marine life that occur at various spatial and temporal scales. Climate, palaeogeography, ocean circulation, biogeochemical cycles, evolution of Life and human activities control MFC over the long term. The geological and historical records offer valuable data on ecological and societal change that can be used to understand the evolution of MFC over time. We explain the links between these long-term drivers and MFC processes, as well as the diverse archives that can be used to study them: the sedimentary record, biogeochemical proxies, fossil assemblages, sclerochronological archives, genetic data, zooarchaeological remains, archaeological artefacts and historical sources.

How to cite: Agiadi, K., Caswell, B., and Darnaude, A. and the the Q-MARE - SEA-UNICORN workshop participants: Marine functional connectivity through the ages: geological and historical perspectives, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5651, https://doi.org/10.5194/egusphere-egu24-5651, 2024.

EGU24-6137 | ECS | Posters on site | SSP1.4

Functional diversity of the Mediterranean bivalve fauna across the Late Miocene ecological crisis 

Barbara Vesely, Mathias Harzhauser, Stefano Dominici, Efterpi Koskeridou, Danae Thivaiou, and Konstantina Agiadi

The Late Miocene was a period of major paleogeographic, climatic and biotic changes for the Mediterranean due to the restriction of the marine gateway to the Atlantic, which culminated to the Messinian Salinity Crisis (MSC), and the ongoing global climatic cooling. The Late Miocene ecological crisis very likely affected biodiversity of bivalves living in the Mediterranean during that time. In this study, we investigate the consequences of the Messinian Salinity Crisis and its preconditioning phase for the evolution of functional diversity of the Mediterranean bivalve fauna. The biodiversity of bivalves is quantified for the Tortonian, the pre-evaporitic Messinian and the Zanclean of the Mediterranean using the functional richness index, by considering the following bivalve species traits: lifestyle, depth range, maximum adult size, trophic role and substrate affinity. The analysis is based on a recently compiled dataset containing the updated fossil record of the Mediterranean bivalves for this time interval. The traits of the species in this dataset is obtained from online open-access databases and the literature. Our results support a decrease in the functional diversity of bivalves in the Mediterranean from the Tortonian to the Early Messinian and a full recovery in the Early Pliocene.

How to cite: Vesely, B., Harzhauser, M., Dominici, S., Koskeridou, E., Thivaiou, D., and Agiadi, K.: Functional diversity of the Mediterranean bivalve fauna across the Late Miocene ecological crisis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6137, https://doi.org/10.5194/egusphere-egu24-6137, 2024.

EGU24-7757 | ECS | Posters on site | SSP1.4

Middle Miocene calcareous nannofossil and isotope fluctuations in the Central Paratethyan Realm (Eastern Carpathians) 

Eliza Anton, Vlad Apotrosoaei, Iulian Pojar, Constantin Lazar, and Mihaela Melinte-Dobrinescu

This work presents the fluctuation pattern related to the modifications in the calcareous nannofossil diversity and abundance and shift in δ13C and δ18O isotopes identified in a succession situated in the Outer Moldavide nappe system of the Eastern Carpathians. The studied section is mainly made by clays and marls and includes a cm-thick volcanic ash layer dated as 13.32 ± 0.07 Ma (de Leeuw et al., 2018). We have pointed out the biotical response to the environmental changes that took place as a consequence of the “Badenian Evaporitic Crisis” of the Central Paratethyan Realm. 

Based on the biostratigraphy of the calcareous nannofossils, we identified the Badenian NN5 biozone, argued by the co-occurrence of Sphenolithus heteromorphus, Coronocyclus nitescens and Cyclicargolithus floridanus. The semiqualitative analysis point out the abundant presence of Helicosphaera spp. (mainly H. carteri), which together with Sphenolithus spp., Cyclicargolithus floridanus, Reticulofenestra pseudoumbilicus and Braarudosphaera bigelowii accounted up to 50% calcareous nannofossil assemblages. Most of the found specimens of Braarudosphaera bigelowii are “rounded” morphotypes, as previously identified in several Central Paratethyan Miocene successions (Melinte-Dobrinescu & Stoica, 2013; Peryt et al., 2021), whereas the “classical” specimens with sharp edges and trapezoidal segments are extremely rare. In the studied interval, the values of δ13C and δ18O isotopes show wide ranges, with a significant negative shift of δ13C isotope values towards the top of the studied succession.

References

De Leeuw, A., Tulbure, M., Kuiper, K.F., Melinte-Dobrinescu, M.C., Stoica, M., Krijgsman, W., 2018. New 40Ar/39Ar, magnetostratigraphic and biostratigraphic constraints on the termination of the Badenian Salinity Crisis: Indications for tectonic improvement of basin interconnectivity in Southern Europe. Global and Planetary Change, 169, 1-15.

Melinte-Dobrinescu, M.C., Stoica, M., 2013. Badenian Calcareous Nannofossil Fluctuation in the Eastern Carpathians: Palaeoenvironmental significance. Acta Palaeontologica Romaniae, 9(2), 47-56.

Peryt, D., Garecka, M., Peryt, T.M., 2021. Foraminiferal and calcareous nannoplankton biostratigraphy of the upper Badenian–lower Sarmatian strata in the SE Polish Carpathian Foredeep. Geological Quarterly, 65(18), 1-22.

How to cite: Anton, E., Apotrosoaei, V., Pojar, I., Lazar, C., and Melinte-Dobrinescu, M.: Middle Miocene calcareous nannofossil and isotope fluctuations in the Central Paratethyan Realm (Eastern Carpathians), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7757, https://doi.org/10.5194/egusphere-egu24-7757, 2024.

EGU24-9263 | Posters on site | SSP1.4

Calcareous nannofossil fluctuation related to the Messinian Salinity Crisis 

Mihaela Melinte-Dobrinescu, Jean-Pierre Suc, and Popescu Speranta-Maria

In the Mediterranean, the latest Miocene was characterized by an exceptional event caused by the severe drop of the sea-level, leading to the Messinian Salinity Crisis (MSC). This event is characterized throughout the whole Mediterranean by the occurrence of thick evaporites in its deep basins and huge fluvial canyons within its margins (i.e., Cita et al., 1978; Cornée et al., 2006; Clauzon et al., 2008). This significant event triggered important faunas and floras modifications from the Mediterranean region and the surrounding basins, affecting the assemblage diversity, abundance, and composition. One of the most sensitive marine planktonic organisms, the calcareous nannoplankton, is well reflecting the palaeoenvironmental setting of the Messinian-Zanclean boundary interval.

This study presents the fluctuation pattern before, during and after the MSC, as identified in several studied successions of the Western and Eastern Mediterranean regions. Below the MSC, the calcareous nannofossil assemblages are characterized by high diversity and abundance, with dominance of the warm-water taxa, such as the discoasterids. At the beginning of the MSC, brackish environment dominated the late Messinian, which is barren of nannofossils, but some marine influxes are to be assumed, as in some Mediterranean areas the salinity was high enough to allow the nannoplankton survival. Calcareous nannoplankton assemblages recorded in the Messinian deposits (NN11b nannofossil subzone) are dominated by long-ranging and diagenetical resistant taxa (i.e., Reticulofenestra spp., Sphenolithus moriformis, and Coccolithus pelagicus). In most investigated sections, during the MSC, almost monospecific assemblages containing Braarudosphaera bigelowii, indicating strong salinity variations, were observed. Around the base and the top of the above-mentioned intervals, blooms of the calcareous dinoflagellate genus Thoracosphaera (suggesting unstable palaeosetting) were also identified. A marine environment is restored within the base of the Pliocene (early Zanclean), being most probably related to the important transgressive event, linked to the reconnection of Mediterranean with the open-ocean. The earliest Pliocene nannofossil assemblages of the NN12 zone are dominated by Discoaster and Sphenolithus taxa, indicative for warm-surface waters and an open-marine environment.

References

Cita, M.B., Ryan, W.B.F., Kidd, R.B., 1978. Sedimentation rates in Neogene deep sea sediments from the Mediterranean and geodynamic implications of their changes. Initial Reports DSDP 42A, 991–1002.

Clauzon, G., Suc, J.-P., Popescu, S.-M., Melinte-Dobrinescu, M.C., Quillévéré, F., Warny, S.A., Fauquette, S., Armijo, R., Meyer, B., Rubino, J.-L., Lericolais, G., Gillet, H., Çağatay, M.N., Ucarkus, G., Escarguel, G., Jouannic, G., Dalesme, F., 2008. Chronology of the Messinian events and paleogeography of the Mediterranean region s.l. CIESM Workshop Monographs 33, 31–37.

Cornée, J.-J., Ferrandini, M., Saint Martin, J.-P., Münch, P., Moullade, M., Ribaud Laurenti, A., Roger, S., Saint Martin, S., Ferrandini, J., 2006. The late Messinian erosional surface and the subsequent reflooding in the Mediterranean: new insights from the Melilla–Nador basin (Morocco). Palaeogeography, Palaeoclimatology, Palaeoecology 230 (1–2), 129–154.

How to cite: Melinte-Dobrinescu, M., Suc, J.-P., and Speranta-Maria, P.: Calcareous nannofossil fluctuation related to the Messinian Salinity Crisis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9263, https://doi.org/10.5194/egusphere-egu24-9263, 2024.

Between 5.97 and 5.33 Ma, the Mediterranean area was fundamentally impacted by the Messinian Salinity Crisis (MSC), a pivotal event that led to the transformation of the Mediterranean Sea into an extensive evaporitic basin, caused by rapidly changing environmental conditions. The MSC was caused by a combination of tectonic and climatic factors, resulting in severe connectivity restriction between the Mediterranean-Paratethys system and the Atlantic Ocean. The Sorbas Basin, thanks to its proximity to the Atlantic gateway and astronomically dated sedimentary succession, represents a key element in understanding the nature of palaeoceanographic transformations affecting the Western Mediterranean, preceding and announcing the MSC. Here, we present the first sea surface temperature (SST) and sea surface salinity (SSS) estimates recorded in Sorbas (i.e., Western Mediterranean) for the time interval between 7.3 to 6.0 Ma. The studied section includes the lower Abad Member (cyclic alternations of homogenous marls and indurated layers) and the upper Abad Member (cyclic alternations of sapropels, diatomites and marls). SSTs were estimated using TEX86 and UK´37 biomarker-based proxies, with cross validation at distinct levels. To further constrain the SSS changes, we combined the TEX86 and UK´37 based SST estimates with δ18O values measured at the same stratigraphic levels on the planktonic foraminifera Orbulina universa. The temperature estimates vary between 17 and 27 °C, with a pronounced cold (17 °C) peak at 7.1 Ma, following the restriction of the Betic and Rifian corridors. This cooling is followed by a generally warmer period lasting until 6.27 Ma, when a colder trend emerges and lasts until 6.18 Ma. A marked and sharp cooling from 27 to 18 °C is observed at 6 Ma, preceding the onset of the MSC. The SST-δ18O- calculated salinity ranges between 34 and 44 for most of the levels. However, several levels around 7.0, 6.74, 6.52 and 6.06 Ma, generated SSS values as low as 20, provoked by exceptionally low, yet not fully understood , δ18OO. universa component in our SSS calculation. The low values might be associated with a significant local influx of fresh water, considering the basin's restricted nature. When comparing our results to coeval records existing for the Eastern and Central Mediterranean (Agios Myron, Kalamaki and Monte dei Corvi), we notice a correlation of warmer and colder peaks across the Mediterranean, albeit with minor leads and lags. Importantly, the Sorbas SST values are well within the range of SSTs in the Eastern and Central Mediterranean. The SSS values of Sorbas are also within the range reported in the Eastern Mediterranean with the exception of those levels presumably affected by fresh water input. In the absence of a full explanation for the associated low-δ18OO. universa values, we observe the dominance of the C37:4 alkenone component, exclusively associated with fresh to brackish water environments, at some of these levels, strongly suggesting the occurrence of repeated fresh water influx into the basin.

How to cite: Lanterna, F., Sierro, F. J., Mulch, A., and Vasiliev, I.: Sorbas’ basin secrets unveiled: First record of Sea Surface Temperature and Sea Surface Salinity in the Western Mediterranean prior to the onset of the Messinian Salinity Crisis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9714, https://doi.org/10.5194/egusphere-egu24-9714, 2024.

EGU24-11589 | ECS | Posters on site | SSP1.4

Laminar Gypsum deposited during the Messinian salinity crisis acme: a case study from the Racalmuto basin (Sicily, Italy). 

Enrico Nallino, Mathia Sabino, Francesco Dela Pierre, and Marcello Natalicchio

During the late Miocene Messinian salinity crisis (MSC), the Mediterranean Basin was transformed into the youngest salt giant in Earth's history. The acme phase of the MSC appeared to have coincided with a high-magnitude sea level drop, resulting in widespread erosion of sulphate evaporites deposited in shallow, marginal basins during the early phase of the MSC. Clastic gypsum deposits were consequently emplaced by submarine mass movements and low to high-density gravity flows in deep basins interfingering with thick halite deposits and hemipelagic, laminated sediments including organic-rich shales and laminar gypsum. Deciphering the depositional mechanisms behind hemipelagites is pivotal to reconstruct the paleoenvironmental and paleoceanographic conditions of deep Mediterranean basins during the MSC acme, including water depth and chemical, physical and biological characteristics of the aquatic system. This work focuses on the Racalmuto basin (Sicily, Italy), where a continuous sedimentary record from the pre-evaporitic Tripoli Fm. to the final stages of the MSC (Upper Gypsum) is exposed. Here, the MSC acme is recorded by gypsum turbidites and a chaotic interval, interbedded with laminar gypsum (“balatino”) formed by nucleation of gypsum crystals in the water column and their subsequent deposition on the sea floor (cumulate deposits). The most typical microfacies consist of an intricated network of gypsum crystals with a rhombohedral to prismatic elongated habit (< 1 mm in size). Petrographic observations show textural changes across the studied interval. The size of the crystals progressively decreases upwards across the studied section, possibly reflecting the increase in the saturation of the brine approaching the time of halite deposition in the deeper parts of the basin. The appearance of a diversified calcareous nannofossils assemblage, interbedded with gypsum laminae immediately below the bottom-grown selenitic gypsum of the Upper Gypsum (final stage of the MSC) suggests that normal marine conditions were intermittently established in the upper water column approaching the end of the MSC acme.

How to cite: Nallino, E., Sabino, M., Dela Pierre, F., and Natalicchio, M.: Laminar Gypsum deposited during the Messinian salinity crisis acme: a case study from the Racalmuto basin (Sicily, Italy)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11589, https://doi.org/10.5194/egusphere-egu24-11589, 2024.

The coquina along the Oued Beth south of Dar bel Hamri near Sidi Slimane is known for its fossil-richness, but the stratigraphic position has long been debated for Late Miocene or Early Pliocene age. A review of fossils and samples taken during field work in the mid-70ies supports an Early Pliocene age. Recently, I described the rich otolith-based fish fauna from these rocks, which are positioned in a funnel-shaped embayment close to the Strait of Gibraltar ideally situated as a reservoir for remigration of biota into the Mediterranean following the Messinian Salinity Crisis. The analysis of the fish fauna revealed that:

1.- The diversification of the fish fauna is exceptionally high and dominated by otoliths from adult specimens, which probably indicates a high food supply at moderate depth on a middle to lower shelf position during the deposition of the coquina.

2.- The otolith-based fish fauna from the Early Pliocene of the Rharb Basin shows a good resemblance not only to the coeval fauna of the Mediterranean, but also exhibits a notable proportion of putative endemic species and species related to today’s tropical West African fauna.

3.- The faunal composition thus exhibits a unique character that is sufficiently different from known or deduced neighboring bioprovinces, and thus a “Maghrebian bioprovince” is proposed for the Early Pliocene NW African region.

4.- The faunal comparison between Early Pliocene Mediterranean and NW African fish fauna reveals few candidates for allopatric speciation and in situ survival in the Mediterranean.

How to cite: Schwarzhans, W.: The Early Pliocene fish fauna of the Rharb Basin in NW Morocco based on otoliths - a reservoir for remigration into the Mediterranean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13099, https://doi.org/10.5194/egusphere-egu24-13099, 2024.

EGU24-14271 | Posters on site | SSP1.4

A similarly warm but drier Mediterranean region at the Miocene - Pliocene transition 

Iuliana Vasiliev-Popa, Konstantina Agiadi, Katharina Methner, Jens Fiebig, and Andreas Mulch

Between 5.97-5.33 Ma, kilometre-thick evaporite units were deposited in the Mediterranean Basin during an event known as the Messinian Salinity Crisis (MSC). The MSC was characterised by a strongly negative hydrological budget, with a net evaporative loss of Mediterranean basin water exceeding precipitation and riverine runoff inputs. Despite evident proves of environmental crisis at the end of the Messinian, the Mediterranean domain still lacks quantitative estimates of temperature change across the transition from the (brackish) Lago Mare, marking the end of the Miocene, to the fully marine Pliocene. Here we reconstruct continental mean annual temperatures (MAT) using branched glycerol dialkyl glycerol tetraether (brGDGT) biomarkers for the time period corresponding to the MSC Stage 3 (5.55-5.33 Ma) and compare them with continental temperature values obtained from Δ47 clumped isotope geochemistry measured on paleosol carbonate nodules found at few locations in the Mediterranean basin. The well-preserved organic biomarkers were extracted from outcrops onshore and offshore covering a vast portion of the Mediterranean Basin; onshore (Malaga, Sicily, Cyprus) and offshore (DSDP core holes 124 and 134 from the Balearic abyssal plane, hole 374 from the Ionian Basin and hole 376 drilled west of Cyprus). Calculated MATs for the 5.55 to 5.33 Ma time interval show values around 16 to 19 ºC for the Malaga, Sicily and Cyprus outcrops. The MAT values calculated for DSDP Leg 13 holes 124, 134 and Leg 42A holes 374 and 376 are lower, around 13 to 16 ºC. Comparing the brGDGT-MAT values with Δ47-MAT values from carbonate nodules, shows high congruence between both approaches. For the northern Mediterranean Δ47-MAT is 24.6 ± 1.6 °C and brGDGT-MAT is 19 ± 4.8 ºC. For Cyprus Δ47-MAT is 20.3 ± 1.7 °C and brGDGT-MAT is 18 ºC ± 4.8 ºC. Given the very different nature of the used paleoproxies, the similarity of the obtained MAT values provides a strong indication of their (cross)validity in sampled sections. Additionally, the measured δ18O values for the carbonate nodules used for the Δ47-MAT show high δ18O of the soil water (in the range of -5 ±0.7‰) indicate highly evaporative conditions for the two onland sites where these were collected (Northern Apennines and Cyprus). We conclude that between 5.55 to 5.33 Ma the temperatures in the Mediterranean region were similar to present-day conditions, yet the region has suffered from excess evaporation as indicated by combined high δ18O values from (inorganic) carbonate nodules and δ2H values from (organic) biomarkers.

How to cite: Vasiliev-Popa, I., Agiadi, K., Methner, K., Fiebig, J., and Mulch, A.: A similarly warm but drier Mediterranean region at the Miocene - Pliocene transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14271, https://doi.org/10.5194/egusphere-egu24-14271, 2024.

The Messinian Salinity Crisis is an event that not only led to the youngest known salt giant, but also impacted the global ocean salinity due to the mass of ions trapped in the Mediterranean Sea. Understanding its full implications requires comprehensive understanding of the events, and due to limitations in data acquisition, modeling is essential to bridge knowledge gaps.
Our latest box model aims to include those processes and aspects that have been indicated to be the most influential by previous model studies. It is forced by (1) a reconstructed freshwater budget with the option to include a salinity feedback, (2) the depth of the Sstrait of Gibraltar and (3) changes in the sea level of the Atlantic. The circulation in the Mediterranean includes the exchange between the eastern and the western basin across the sill  of Sicily on the horizontal level, as well as vertical exchange between two layers. The shapes of the boxes are determined by the hypsometry of the basin, which allows for realistic drawdown and refilling scenarios. The latter offers the option to test the influence of the Paratethys.
To assess the validity of scenarios, the model output is compared to the volume of the known deposits as well as the cycles recorded in gypsum outcrops. An additional tracer in the model is the Sr isotope signal. 
Our findings highlight the importance of horizontal gradients in explaining gypsum deposits in the western basin, unlike the more uniform distribution of gypsum and halite the model produces in the eastern basin. While the onset of gypsum deposition may not necessarily differ between the basins, our results support the theory that halite precipitation began earlier in the east than in the west. This type of model will not answer all questions, but it might guide us to the new ones.

How to cite: Ebner, R., Meijer, P., and Aloisi, G.: From marine to brine and back – a new box model approach to investigate the external influences on the Messinian salinity crisis  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16605, https://doi.org/10.5194/egusphere-egu24-16605, 2024.

EGU24-20769 | Orals | SSP1.4

What controlled the Mediterranean Sea level during the Lago-Mare stage of the Messinian salinity crisis? 

Daniel Garcia-Castellanos, Hanneke Heida, Dan Palcu, and Vanni Aloisi

Stratigraphic and geochemical evidence suggests that the Mediterranean Sea underwent widespread salinization and a kilometer-scale evaporative drawdown between 5.97 to 5.33 million years ago, during the period known as the Messinian salinity crisis (MSC). The mechanisms responsible for the accumulation of one million cubic kilometers of salt on the sea floor and the impact on terrestrial and marine fauna and on climate are being better understood in the last decades. However, the presence of relatively fresh water sediment containing fossil fauna of eastern (Paratethyan) provenance in the last stages of the MSC poses severe problems to understand the ending of the crisis. These brackish-water deposits, known as the Lago-Mare unit, are sometimes found at elevations close to the present sea level, in apparent contradiction with the coetaneous evaporitic sediment found in deeper, central parts of the Mediterranean.

 

We make use of landscape evolution models calibrated with sediment transport and river incision data to explore plausible scenarios of climate and sea level changes during the MSC. The results show that, upon full isolation, the large initial evaporative sea level fall of the Mediterranean leads to a progressive capture of the waters from nearby lacustrine basins such as the Black Sea or the Pannonian Basin. This drainage area expansion triggers a gradual sea level rise in the Mediterranean. Milankovic climate oscillations superimposed to this trend lead to large-amplitude (500-1000 m) harmonic sea level variations reaching ever-higher levels. This is consistent with the salt precipitation in deeper areas during lowstands and Lago-Mare deposition during highstands in marginal areas. This model may also explain the seemingly contradiction between the high-level Lago-Mare deposits and the km-scale sea level drop estimated from erosion markers and implicit in the Zanclean cataclysmic reflooding model.

How to cite: Garcia-Castellanos, D., Heida, H., Palcu, D., and Aloisi, V.: What controlled the Mediterranean Sea level during the Lago-Mare stage of the Messinian salinity crisis?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20769, https://doi.org/10.5194/egusphere-egu24-20769, 2024.

EGU24-21155 | Orals | SSP1.4

The history of the Eastern Paratethys during the Serravallian-Tortonian from a restricted marine basin to a megalake: integrated stratigraphy, hydrological evolution and biotic record 

Davit Vasilyan, Oleg Mandic, Marius Stoica, Kakhabe Koiava, Stjepan Coric, Pavel Goldin, Mathias Harzhauser, Wout Krijgsman, and Sergei Lazarev

During the late Middle – Late Miocene, the large epicontinental Paratethys Sea that occupied the vast territory of West Eurasia’s interior underwent a remarkable hydrological transformation. At 12.6 Ma, driven by the interplay between the climatically controlled basin water budget and tectonically controlled gateway dynamics, the Paratethys became hydrologically isolated from the global ocean. During the following Sarmatian s.l. Stage (12.65 – 7.6 Ma), the largest eastern branch of the Paratethys – The Eastern Paratethys – became an endorheic basin with the hydrological balance being primarily controlled by the climate (ratio of evaporation/precipitation). Variations in the hydrological balance affected water chemistry, leading to a high level of aquatic ecosystem endemism/radiation and later to their extinction. Despite relatively well-documented trends of biotic evolution in the Sarmatian s.l., aspects such as comprehensive age constraints, (substage) biozonation, and depositional characteristics of strong water-level fluctuations are still missing. This gap of knowledge complicates interregional paleo(bio)geographic, tectonic, and paleoenvironmental studies of the five million-year-long portion of West Eurasian history.

In this study, we present the results of our multidisciplinary research project dedicated to geochronology, biostratigraphy, environmental evolution, and dynamics/response of the biotic record of the Eastern Paratethys during the Sarmatian s.l. The periods (i.e. stages) prior to (Konkian) and after (Maeotian) the isolation have been also considered in this study to provide a complete picture of the basin’s hydrological transformation. Three representative sections, located in the Caspian Sea, Transcaucasian Strait and the Black Sea covering the Konkian – Sarmatian s.l. – lower Maoetian, have been studied. Systematic sampling of the sections for magnetostratigraphy, mollusk, ostracod, foraminifera and nannofossils allowed to create a consecutive and well-dated biotic record and enabled evaluation of the synchronicity of the biozones in different parts and depositional settings of the basin. Moreover, the marine vertebrate fauna (fishes, marine mammals) across the Konkian-Maeotian has also been documented and studied.

Our data provides integrated stratigraphic constraints of the Serravallian-Tortonian of the Eastern Paratethys and completes the so far missing ages of the Sarmatian s.l. substages and biozones. Further, the reconstruction of depositional environments of the Eastern Paratethys during the Sarmatian s.l., especially for the Caspian Basin part, helped to understand the scale of the extreme Sarmatian s.l. water level oscillations. Integration of the age model, depositional setting and marine vertebrate faunal record suggest a very diverse and abundant fish and marine mammalian fauna in the Volynian (early Sarmatian s.l.), which, however, gradually decrease in the Bessarabian (middle Sarmatian s.l.) and entirely vanishes by the end of the Khersonian (late Sarmatian s.l.).

How to cite: Vasilyan, D., Mandic, O., Stoica, M., Koiava, K., Coric, S., Goldin, P., Harzhauser, M., Krijgsman, W., and Lazarev, S.: The history of the Eastern Paratethys during the Serravallian-Tortonian from a restricted marine basin to a megalake: integrated stratigraphy, hydrological evolution and biotic record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21155, https://doi.org/10.5194/egusphere-egu24-21155, 2024.

EGU24-22572 | Posters on site | SSP1.4

Multi-proxy characterization of the Messinian Salinity Crisis deposits in the Sorbas Basin (SE Spain): Implications on the paleo-environmental evolution during the uppermost Miocene 

Fadl Raad, Philippe Pezard, Cesar Viseras, Francisco J. Sierro, Luis M. Yeste, Andrea Schleifer, Johanna Lofi, Angelo Camerlenghi, and Giovanni Aloisi

The Sorbas Basin (Spain) has been a key study area for the understanding of the Late Miocene Messinian Salinity Crisis (MSC) (5.97-5.33 Ma). The MSC deposits of the Sorbas Basin consist of four sedimentary units: (1) the pre-MSC Abad marls topped by (2) the evaporitic Yesares gypsum member, followed by two non-evaporitic units known as the (3) Sorbas and (4) Zorreras members. These deposits have been widely studied almost exclusively in the several outcrops across the basin.


In 2021, four ~175m-long boreholes (named SG0, 1, 2 and 3) covering most of the MSC sequence were drilled, cored, and logged in the Marylen gypsum mine in Sorbas. These successions provided for the first time a continuous, non-outcropping succession of the MSC record. In addition to the recovered cores (~75% recovery), downhole geophysical logging data was obtained from the four holes and digital images of the area were collected with a drone.


Optical borehole wall images provide mm-scale images of the borehole walls, highlighting the sedimentological and structural characteristics of the deposits. Downhole geophysical measurements included acoustic velocity, electric resistivity and magnetic susceptibility, and natural spectral gamma ray. In addition to the petrophysical logs, a Vertical Seismic Profile, including a walk-away distributed acoustic sensing experiment, was acquired in holes SG2 and SG3.


Preliminary results confirmed not only the astronomical precession-driven cyclicity observed elsewhere in the Messinian gypsum, but also potentially higher-frequency cyclicity in the post-evaporitic Sorbas Mb. The Digital Outcrop Model allowed for a detailed correlation between the wells while recognizing various discontinuities and obtaining 3D data of geometry and dimensions of the different geobodies that respond to the interaction of auto and allocyclic processes that conditioned erosion and sedimentation in this western sector of the Mediterranean.

How to cite: Raad, F., Pezard, P., Viseras, C., Sierro, F. J., Yeste, L. M., Schleifer, A., Lofi, J., Camerlenghi, A., and Aloisi, G.: Multi-proxy characterization of the Messinian Salinity Crisis deposits in the Sorbas Basin (SE Spain): Implications on the paleo-environmental evolution during the uppermost Miocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22572, https://doi.org/10.5194/egusphere-egu24-22572, 2024.

EGU24-22574 | Orals | SSP1.4

Gateway to a salt giant: a new record of the Messinian Salinity Crisis from the westernmost part of the Mediterranean 

Emmanuelle Ducassou, Rachel Flecker, and Trevor Williams and the IODP Expedition 401 participants

Salt giant formation is dependent on the dimensions of the connection linking the marginal basin to the open ocean and the nature of exchange between then. However, records from these connecting straits are rare, making it difficult to test connectivity scenarios. As part of the IMMAGE Land-2-Sea project, Integrated Ocean Discovery Program Expedition 401 drilled a new site, U1611, in the Alborán Sea. This basin is thought to have been part of the corridor that linked the Mediterranean with the Atlantic during the formation of the late Miocene salt giant. More than 600 m of sediments were recovered from Site U1611 spanning the early Messinian to early Pliocene. Here we present preliminary results and consider their implications for the origin and evolution of the Messinian Salinity Crisis.

How to cite: Ducassou, E., Flecker, R., and Williams, T. and the IODP Expedition 401 participants: Gateway to a salt giant: a new record of the Messinian Salinity Crisis from the westernmost part of the Mediterranean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22574, https://doi.org/10.5194/egusphere-egu24-22574, 2024.

Carbon capture and storage technology is a necessary means to achieve the temperature control goal of 1.5 degrees Celsius under the background of peak carbon dioxide emissions and carbon neutrality. The storage of carbon dioxide in oil and gas reservoirs has the advantages of high safety, large storage capacity, and less additional cost. The reservoir-caprock configuration can provide favorable space for the storage of carbon dioxide geological bodies. To make clear the distribution range of geological bodies suitable for carbon dioxide sequestration, taking the middle-south section of the eastern sag of Liaohe as an example, based on the model of the ratio of mud to ground and caprock effectiveness division, the control factors of caprock sealing were analyzed by entropy weight method combined with TOPSIS method, and the effective thickness of reservoir was determined by clarifying the relationship between reservoir lithology, physical properties, oil content and electricity. The results show that the lower limit of the effective caprock mud-to-ground ratio in the sand-mud interbedding sequence is 70.6%, and the sealing ability of caprock is mainly affected by the thickness of the fault and the thickness of the caprock single layer; The two sets of caprocks in the Shahejie Formation and Dongying Formation are relatively stable, with good fault-caprock configuration sealing, and the fault juxtaposition thickness in the Shahejie Formation is characterized by "thick in the north and thin in the south"; The effective reservoirs of the Dongying Formation are distributed in the whole region, the effective reservoirs of Es1 are distributed in the north of Rongxingtun, and the distribution range is smaller than that of the Dongying Formation, while the effective reservoirs of Es3 are mainly distributed in Huangyure area at the northern end of the study area, and the distribution range is further reduced. According to the reservoir-caprock configuration, carbon dioxide storage types can be divided into three types: shallow storage type, deep storage type, and multi-layer storage type. The lower caprock is well sealed and the lower effective thick reservoir controls the deep enrichment of carbon dioxide; The lower caprock is poorly sealed, and the effective thick reservoir in the middle or upper part controls the multi-layer enrichment of carbon dioxide; The lower caprock is poorly sealed, the upper caprock is well sealed, and the upper effective thick reservoir controls the shallow enrichment of carbon dioxide. The relationship between the effective thickness of the reservoir and the sealing ability of the caprock determines the vertical distribution series of carbon dioxide.

How to cite: li, H. and jiang, Y.: Study on Reservoir-caprock Configuration for Carbon Dioxide Sequestration in oil and gas reservoirs , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-86, https://doi.org/10.5194/egusphere-egu24-86, 2024.

EGU24-362 | ECS | Posters on site | ERE1.8

Towards net-zero: assessing the carbon storage potential of onshore saline aquifers in Brazil 

Francyne B. Amarante, Juliano Kuchle, and Mauricio B. Haag

Global warming poses a major challenge that humanity will face during the 21st century, requiring a significant reduction in anthropogenic CO2 emissions to mitigate the escalating global temperature. Several governments worldwide, including Brazil, have committed to achieving net-zero CO2 emissions by 2050, which will be impossible without Carbon Capture, Utilisation and Storage (CCUS) deployment. Ranked 12th globally in CO2 emissions (and 1st in South America), Brazil is in the early stages of studying CCUS. At present, CCUS efforts in the country primarily revolve around enhanced oil recovery, with limited exploration of CO2 injection in alternative geological settings. A total of 31 sedimentary basins span Brazilian territory, encompassing an area of approximately 6.4 million km2, 75% of which is situated onshore. The potential for CO2 storage in saline aquifers is gaining attention globally, proving a successful and effective approach in various sites. In this work we combine the available surface (geological maps, roads, and gas pipelines) and subsurface data (seismic lines and borehole data) to assess the logistics and feasibility of utilizing saline formations in onshore intracratonic basins as CO2 sinks, aiming to enable Brazil to reach net-zero CO2 emissions by 2050. Previous studies indicate that the Parnaíba, São Francisco, Amazonas, and Paraná basins present saline formations with favorable characteristics for CO2 injection, such as adequate depths, porosity, and permeability. Building upon prior research, we introduce the onshore portion of Espírito Santo Basin to the list of potential sinks, where the target saline aquifer is the pre-salt Mucuri Formation. Results show that greenhouse gases emissions from industrial processes are notably higher in the southeast region of Brazil. Within this region, two formations exhibit considerable potential for carbon sequestration in saline aquifers: (i) the Mucuri Formation, located in the onshore Espírito Santo Basin, reaching 350 m of thickness and shallowest depths of about 950 m, and (ii) the Rio Bonito Formation, in the proximities of the São Paulo state, with over 100 m of thickness and shallowest depths of about 650 m. For large-scale projects, CO2 transport in the region can be accomplished using the available infrastructure and the available gas pipelines, while smaller-scale research projects can utilize trucks, rail, and ships. Brazil's untapped potential for CCUS presents a unique funding opportunity from the private sector, marking a crucial step toward sustainable and impactful climate action.

How to cite: B. Amarante, F., Kuchle, J., and B. Haag, M.: Towards net-zero: assessing the carbon storage potential of onshore saline aquifers in Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-362, https://doi.org/10.5194/egusphere-egu24-362, 2024.

EGU24-800 | ECS | Posters on site | ERE1.8

Ultrasonic Evaluation of Shales vis-à-vis Temperature: A Case Study from Permian Damodar Valley Basin 

Varun Dev Jamwal and Ravi Sharma

Despite constituting two-thirds of the sedimentary rock volume, shales are a few of the least understood rocks. The varied depositional processes and environments give rise to complexity and anisotropy in them. Understanding unconventional resources like shales becomes crucial given their abundance in the petroleum systems and reservoirs and their potential suitability for sub-surface carbon and radioactive waste storage. Therefore, paramount significance lies in understanding the petrophysical and rock physical characteristics of shales to develop feasibility models for the sustainable use of these rock types.
 
This investigation focuses on the Barren Measures and Raniganj Formation shales in the Damodar Valley of Eastern India, which are primarily rich in clays, carbon, and iron and are of fluvio-lacustrine origin. These relatively shallow formations can be good sites for storage and sequestration as they are overlain by shaley and clayey formations acting as traps. The anisotropy in shales is even more challenging as its imponderables range from a micro to a macro scale. This changes even further with factors like organic-hosted porosity and maturity. The inherent anisotropy in shales necessitates a multiscale examination. These multiscale discontinuities, coupled with parameters like organic matter and maturity, impact the elastic properties of the rocks, as evidenced by the ultrasonic evaluations.
 
In this study, acoustic characterization of samples was conducted using a benchtop ultrasonic wave propagation setup. The samples were clustered based on their colour and observed megascopic properties. Some sandstones were also included in the study to contrast sandstones with respect to shales. The wave velocities were determined for samples subjected to progressive heating up to 200°C (gas window), and the consecutive changes in the elastic parameters and resultant wave velocities of the rock were studied. Inputs from other methods utilizing different physics, such as FE-SEM, XRD were integrated to refine our interpretation. Notable changes were seen in wave velocities, especially in clusters with elevated organic content, while the density and Vp cross plots gave a good correlation with an R2 value of around 0.7.
This study advances our understanding of the impact of temperature on the elastic properties of shales, an aspect less explored than factors like stress and pressure. Thoroughly characterizing these parameters through acoustic methods provides critical insights into shale's storage capacity, carbon sequestration potential, and additional hydrocarbon recovery, specifically with respect to the Damodar Valley shales, aiding India to offset the projected peak of 4 GT CO2 emissions to achieve the carbon neutral goal promised at COP 26 and fulfilling UN Sustainable Development Goals.

How to cite: Jamwal, V. D. and Sharma, R.: Ultrasonic Evaluation of Shales vis-à-vis Temperature: A Case Study from Permian Damodar Valley Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-800, https://doi.org/10.5194/egusphere-egu24-800, 2024.

EGU24-1674 | ECS | Posters on site | ERE1.8

Using FracpaQ and seismic attributes to assess seismic scale fractures in carbonate reservoirs 

Hager Elattar, Richard Collier, and Paul W.J. Glover

Abstract: Fractured carbonate reservoirs are of great importance in the oil industry due to their significant role in global oil reserves and complex nature, where the majority of these reservoirs are naturally fractured, making them complex and challenging for oil recovery. The detection and characterization of fractures are essential for understanding the reservoir's petrophysical properties and hydrocarbon recovery potential as they play a critical role in reservoir performance. In this paper we have used 3D seismic from the Razzak field in the Western Desert, Egypt, with a specific focus on the Alamein dolomite reservoir. The reservoir holds significance due to its prolific oil-bearing nature, and featuring widespread lateral distribution in the northern Western Desert. Additionally, its contribution to an active Mesozoic petroleum system emphasizes its importance. Using Petrel software, the Alamein top and visible faults were identified, leading to the creation of a structural map illustrating the WSW-ENE axes of the Alamein's structural culminations in the southern part of the horst block. Owing to an extensional force during the Jurassic period with a NE-SW orientation, resulting from rifting, was evident, marked by the formation of normal faults associated with the opening of the Neotethys in the NE-SW direction. In the interpretation of 3D seismic data for Alamein dolomite reservoir, only one major listric normal fault was identified. However, the presence of minor faults or fractures, not easily discernible with conventional seismic techniques, is plausible. To address this, volume attributes were applied to detect subtle changes in seismic properties: (i) the curvature operation calculated the dip and azimuth angles, aiding in identifying structural complexities like faults and fractures, (ii) the maximum curvature value highlighted areas of steeply dipping or folded structures, (iii) Edge detection emphasized sharp boundaries, yet no hidden fractures or minor faults were revealed. The variance attribute yielded limited information, but Ant tracking on the variance cube effectively identified hidden minor faults and fractures. Incorporating the Ant track attribute into FRACPAQ software provided an objective methodology for quantifying fracture patterns, revealing NW-SE-oriented fracture segments in contrast to the WSW-ENE orientation of the major fault. Consequently, seismic attributes will unveil concealed fractures, and the application of FRACPAQ will prove effective in furnishing data on fracture orientation and length statistics.

Key words: FracpaQ; seismic attributes; fractured carbonate; Razzak field

How to cite: Elattar, H.A., Collier, R., and Glover, P. W. J.: Using FracPaQ and seismic attributes to assess seismic scale fractures in carbonate reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1674, https://doi.org/10.5194/egusphere-egu24-1674, 2024.

How to cite: Elattar, H., Collier, R., and Glover, P. W. J.: Using FracpaQ and seismic attributes to assess seismic scale fractures in carbonate reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1674, https://doi.org/10.5194/egusphere-egu24-1674, 2024.

Revealing the thermal structure of subsurface is crucial for various projects including geothermal energy exploitation, CCS and hydrocarbon exploration. For instance, temperature is one of the key physical underground parameters governing the type of Geothermal systems, whether injected CO2 remains in supercritical fluid stage and the depth of Golden Zone at where the hydrocarbon accumulations occur. Thus, understanding the temperature and geothermal gradient change in 1D-2D-3D sense indicates sweet spots and helps geoscientists to build more robust models to reduce the risks.

Based on this concept, this study aims to demonstrate the outcomes of a game-changer method which is the conversion of interval velocities into temperatures, thermal conductivities and heat flows by the help of recently proposed empirical relationships. As a case study, Northern Arabian Plate, SE Turkey is selected due to the neglection of thermal conditions in the area. Therefore, oil & gas industry-wide accepted methodologies have been applied to better understand thermal behaviour of the subsurface and how it has been controlled by regional tectonic edifices including large-scale thrust and strike slip faults.

In terms of methodology, as the first step, dynamic bottom hole temperatures of the wells have been converted into static ones by the help of “Temperature Analyser” web application. The converted temperature measurements have been used to generate regional temperature and geothermal gradient maps for every 500 meters. On the other hand, for 3D temperature models, seismic velocities have been converted into temperature cubes after calibration with the converted BHT measurements. Generated temperature cubes have been reflected on seismic sections to display lateral and vertical variations in temperature behaviour. It also allows the detection of meaningful temperature anomalies corresponding to possible fluid content.

The results reveal that abrupt temperature increase on maps directly coincides with the locations of oil producing fields. The same behaviour was noted globally both for hydrocarbon and geothermal fields. The change in temperature trend is also dominated by regional tectonics of the focus area. Large thrust fault systems act as boundaries for thermal anomaly regions while sinistral Mosul Fault Zone displaces and separates high temperature zones in a NW-SE sense. This movement can be easily associated with the Northern slip of the Arabian Plate since the continental collision occurred in the Miocene.

 

Based on these observations, the workflows and results of this study can be used for detailed investigation of subsurface geology, thermal conditions, and their effect on potential reservoirs for geothermal and CO2 storage. Workflows used to generate thermal models might allow the development of more efficient sustainable energy projects not only for the Northern sector of the Arabian plate but also for the other regions of the World.

How to cite: Uyanik, A.: Conversion of Interval Velocities into Thermal Models: A Game Changer Method for Subsurface Energy Exploitation Projects , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1739, https://doi.org/10.5194/egusphere-egu24-1739, 2024.

EGU24-2177 | Orals | ERE1.8

Short and long-term multiphase reactive transport processes during a pilot test of air injection into a sandstone gas storage facility 

Laurent De Windt, Irina Sin, Camille Banc, Anélia Petit, and David Dequidt

This study is based on unique field data on a 3-year pilot test during which air containing 8 mol% O2(g) was injected as a cushion gas into a natural gas reservoir, a carbonate-cemented sandstone aquifer located in the Paris Basin (France) [1]. The oxygen was fully depleted several months after injection completion, meanwhile CO2(g) was detected around 2–6 mol%; the pH decreased from 8 to 6, while reducing conditions shifted to mildly oxidizing ones with increasing concentration of sulfates in equilibrium with gypsum. After the test completion, the long-term evolution of the aquifer was assessed by a 15-year survey. The pH gradually returned to its near initial state and sulfates were reduced by 2 to 3 times. Data on the release of trace metals (Ba, Cu, Pb, Zn) during and after the test were also available.

Multiphase reactive transport models were developed on these field data using the HYTEC reactive transport code in 2D-reservoir configurations [1]. At the short-term scale, modeling focused on the gas-water-rock reactive sequence during the air injection: 1/ depletion of the injected O2(g) due to pyrite oxidation, 2/ leading to acidity production and dissolved sulfates, 3/ acidity buffering by calcite dissolution, 4/ followed by gypsum precipitation and CO2(g) exsolution. At the long-term scale, the modeling tackled with the progressive return to the baseline chemistry of the deep aquifer that was 1/ mostly driven by transport processes and 2/ to a lesser extent, slow water/rock chemical interactions.

These field-based models developed at short and long-term could be used as a workflow for other gas storage facilities, e.g. biomethane, compressed air, and CO2.

[1] Sin, I., De Windt, L., Banc, C., Goblet, P., Dequidt, D. (2023). Assessment of the oxygen reactivity in a gas storage facility by multiphase reactive transport modeling of field data for air injection into a sandstone reservoir in the Paris Basin, France. Science of The Total Environment 869, 161657.

How to cite: De Windt, L., Sin, I., Banc, C., Petit, A., and Dequidt, D.: Short and long-term multiphase reactive transport processes during a pilot test of air injection into a sandstone gas storage facility, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2177, https://doi.org/10.5194/egusphere-egu24-2177, 2024.

Kerogen is typically categorized in three types: type I is associated with lacustrine, type II associated with marine, and type III associated with terrestrial sources, respectively. The Kerogen type is a crucial factor affecting oil-generative properties as it significantly influences the initiation and potential for hydrocarbon generation in source rocks. Geoscientists traditionally use Rock-Eval pyrolysis to determine kerogen types, maturity, and pyrolysis reaction temperature (Tmax), and calculate hydrocarbon potential, essential factors in assessing oil reserves and understanding the oil window. Such method, however, has insufficient resolution and is time-consuming. In this study, we employ a temperature-dependent infrared (IR) spectroscopy method to precisely determine kerogen type, maturity, and Tmax. Specifically, our IR spectroscopy is combined with a numerical analysis model developed for the analysis of various organic matter samples. Through measurements of the IR spectra of samples at different temperatures (Heating-FTIR), we determine the maximum sedimentary burial temperature and the pyrolysis Tmax of kerogen. By applying the conversion formula by Shibaoka & Bennett (1977), (R0)a=Ra+btI*exp(cTm), we derive a virtual vitrinite reflectance, which is strongly correlated with our IR spectroscopy results, with insights into the maturation. This Heating-FTIR technique is a valuable tool for petroleum geology, facilitating the assessment of oil potential and maturity. Future refinement of the numerical model and improvement of the instrumentation are required to apply this technique to broader fields, such as sedimentary temperature for ancient geothermal gradient with better understanding of the sedimentary history.

How to cite: Chen, Y.-Y. and Chang, Y.-J.: Evaluation of Oil Source Rocks Using Temperature-dependent Infrared Spectroscopy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2449, https://doi.org/10.5194/egusphere-egu24-2449, 2024.

EGU24-3199 | ECS | Posters virtual | ERE1.8

 Using Quantitative Diagenesis to characterise and understand carbonate CCUS prospects 

Omar Mohammed-Sajed, Fraidoon Rashid, Paul Glover, Richard Collier, and Piroska Lorinczi

Recent years have seen the growth of new techniques that combine conventional stratigraphic and observational approaches to characterizing the type, scope, extent, timing and effects of diagenetic processes with petrophysical measurements of their rock microstructure. These Quantitative Diagenetic (QD) techniques can be used to predict post- and pre-dolomitisation porosities and permeabilities as well as trace the pathway of the diagenetically evolving rock through different stages of diagenesis that may turn a low-quality carbonate reservoir into a high-quality reservoir, or vice versa. While these new QD techniques are becoming useful for the characterization of hydrocarbon reservoirs, they are also extremely useful in the characterization of carbonate reservoirs for prospective CCUS use. This paper will briefly explain some of the main approaches to QD including dolomitisation prediction, petrodiagenetic pathways, reservoir quality fields, and Fracture Effect Index (FEI), before examining how they can be used to ensure that the prospective CCUS target reservoir is sufficiently well characterized that effective reservoir modelling can take place, and that the volume, flow and trapping of CO2 in the reservoir can be effectively monitored. Dolomitisation is known to be affected by the presence of CO2, with CO2 dissolving in aqueous pore fluids to form carbonic acid that directly affects porosity through dissolution and indirectly by affecting the dynamics of the dolomitisation process itself. There are two current QD methods for predicting the change in porosity upon dolomitisation. One is affected by both the direct and indirect effects, while the other is only sensitive to the indirect effects. Both the direct and the indirect effects can be plotted on a petrodiagenetic pathway. The presence of fractures is also a key aspect of how injected CO2 will flow in a CCUS reservoir. The QD parameter FEI describes the change in permeability of a rock concomitant upon a unit change in fracture porosity (i.e., what increase in flow results from a given increase on fracture porosity). This varies depending upon the degree to which fractures are connected and can be extremely useful in predicting the flow of CO2 within a fractured legacy carbonate CCUS prospect. In summary, QD approaches have the potential to provide those who need to characterise and model carbonate CCUS prospects with new and useful tools.

 

How to cite: Mohammed-Sajed, O., Rashid, F., Glover, P., Collier, R., and Lorinczi, P.:  Using Quantitative Diagenesis to characterise and understand carbonate CCUS prospects, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3199, https://doi.org/10.5194/egusphere-egu24-3199, 2024.

EGU24-3696 | ECS | Posters virtual | ERE1.8

Simulation experiment evaluation and chemical kinetics prediction of the composition of n-alkanes components 

Song Bo, Haitao Xue, and Shuangfang Lu

          It is pivotal to predict the overall composition of subsurface oil and gas reservoirs to assess their fluidity, phase behavior, and recovery potential. Recognizing the significance of n-alkanes as key constituents of mature oil and gas, this study conducted a thermal simulation experiment of gold tube hydrocarbon generation on the source rock of Gulong Sag. The experiment included comprehensive analysis and measurement of the n-alkanes components in a representative sample. Subsequently, an empirical regression evaluation formula was established to evaluate the n-alkanes composition at various maturity stages. Furthermore, a chemical dynamics model for the formation of individual n-alkanes single molecule components was developed and calibrated based on the principles of chemical kinetics. Combined with the stratigraphic burial history and thermal evolution history of the target area, the distribution and evolution characteristics of n-alkanes components in different evolutionary stages of geological conditions can be quantitatively evaluated and predicted. Moreover, the phase behavior of n-alkanes components can be determined based on the evolution characteristics of these components. Experimental results indicate that the methane yield continues to increase with temperature under both heating rates. Additionally, the yield of n-C to n-C initially reaches its maximum with the temperature increase, and subsequently decreases. Furthermore, the hydrocarbon generation characteristics of n-alkanes follow a Gaussian distribution trend. The kinetic results demonstrate that the activation energy of n-alkanes falls within the range of 190-280 kJ/mol, while the distribution of pre-exponential factors is uneven. By considering the geological conditions, it has been determined that the light component in the Gulong Sag is currently experiencing a favorable generation period, whereas the heavy component has reached its peak formation stage, with some undergoing cracking. The oil and gas produced under these geological conditions exist as single-phase unsaturated fluids within volatile reservoirs. The evaluation value of the experimental regression formula, along with the predicted value from the dynamic model, aligns well with the experimental data, providing a solid foundation for the geological application of the model. Therefore, this research serves as a stepping stone towards furthering our understanding of hydrocarbon composition prediction, as well as evaluating phase behavior, mobility, and recovery of underground oil and gas in conjunction with geological conditions. 

How to cite: Bo, S., Xue, H., and Lu, S.: Simulation experiment evaluation and chemical kinetics prediction of the composition of n-alkanes components, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3696, https://doi.org/10.5194/egusphere-egu24-3696, 2024.

EGU24-3700 | ECS | Posters virtual | ERE1.8

Characteristics and factors controlling Permian shale gas reservoirs in the Hongxing area, Sichuan Basin, China 

BaiZHi Li, Nengwu Zhou, and Shuangfang Lu

Successful exploration of Permian shale gas in the Hongxing area has broadened shale gas exploration in the Sichuan Basin; however, the target layer is newly discovered, and reservoir research, which is key to shale gas exploration and development, is limited, thus restricting the screening and evaluation of the section containing the shale gas target layer. In this study, using organic carbon, whole-rock mineral analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and other experimental methods, and by systematically identifying different lithofacies, we clarified the organic‒inorganic composition and microscopic pore structure characteristics of Permian shales in different phases of the Hongxing area and revealed the main factors controlling high-quality reservoirs and favorable lithofacies types for exploration. The results show that the shale in the study area mainly features six types of lithofacies: high-carbon siliceous shale (RS), high-carbon mixed shale (RM), high-carbon calcareous shale (RC), high-carbon muddy shale (RCM), low-carbon muddy shale (LCM), and low-carbon calcareous shale (LC). Organic pores are mainly present in RS, RM, RC, and RCM, while inorganic pores are dominant in LC and LCM. The pores are dominantly micropores, some mesopores are present, and very few macropores are present. Among them, the degree of micropore development is mainly affected by organic matter (abundance, maturity, and type), that of mesopores is mainly affected by clay minerals, and that of macropores is mainly affected by siliceous and clay minerals. There are obvious differences in the pore structure of different lithologies. The RS has the highest pore volume and specific surface area, with average values of 13.8×10-3 cm3/g and 21.57 m2/g, respectively, and its pore morphology is ink-bottle type, with pore diameters mainly <10 nm. The storage space of RM, RC, RCM, and LCM is moderate, with low-carbon argillaceous shale (LM) having the lowest.

How to cite: Li, B., Zhou, N., and Lu, S.: Characteristics and factors controlling Permian shale gas reservoirs in the Hongxing area, Sichuan Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3700, https://doi.org/10.5194/egusphere-egu24-3700, 2024.

EGU24-3864 * | ECS | Orals | ERE1.8 | Highlight

From hydrocarbons to geothermal energy: a case study from the Dutch subsurface 

Annelotte Weert, Francesco Vinci, David Iacopini, Paul van der Vegt, Stefano Tavani, and Kei Ogata

The West Netherlands Basin, which has a long history in exploration as a former prosperous hydrocarbon province, is currently a geothermal hotspot. Being exploited since the 1950’s, most of its oil and gas fields are now in their final phase of production. In the past decade, interest shifted to sustainable energy sources. The geothermal industry in the area is developing quickly, helped by the legacy of the hydrocarbon industry: a wealth of publicly available seismic and well data. Currently, the area has 14 realized, and at least 3 projects in the development phase, with the Late Jurassic Nieuwerkerk Formation being the main target.

Conversely to petroleum systems, in which anticlines are the preferential target for hydrocarbon exploration, synclines are the most suitable sites for geothermal exploration. They offer higher temperatures with respect to the limbs and anticlines, and possible remaining hydrocarbons are not expected to be located inside the central portions of the synclines.

The West Netherlands Basin is a former rift basin that developed during the Mesozoic in the framework of the North Sea rift, and subsequently inverted during the Late Cretaceous. The Nieuwerkerk Formation was deposited during the last major rifting phase. Thus, the thickest packages of its fluvial-deltaic deposits are fault-controlled and commonly located in the synclines. The heterogeneity of fluvial reservoirs causes lateral and vertical quality variations in porosity, permeability and net-to-gross ratios. With the hydrocarbon industry focussing on the stratigraphic highs, there is only limited well data available for the central portions of the synclines.

With reprocessed 3D seismic data, our study uses an image processing approach, coupling traditional amplitude mapping with seismic attributes. This will help to reconstruct the evolution of the fluvial architecture of the Nieuwerkerk Formation over time. By tying the seismic with well data, a better prediction of the quality of the sandy bodies per location can be made. These results can be implemented in de-risking geothermal well planning across fluvial reservoirs in inverted rift basins.

How to cite: Weert, A., Vinci, F., Iacopini, D., van der Vegt, P., Tavani, S., and Ogata, K.: From hydrocarbons to geothermal energy: a case study from the Dutch subsurface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3864, https://doi.org/10.5194/egusphere-egu24-3864, 2024.

EGU24-4657 | ECS | Orals | ERE1.8

Wave velocities as a proxy to forecast deformation during cyclic loading-unloading in porous reservoir rocks 

Debanjan Chandra, Barbara Perez Salgado, and Auke Barnhoorn

Porous reservoir rocks like sandstones have gained utmost important in the last decade as a potential sink for CO2. Most of the targeted reservoirs are depleted oil and gas fields, which has caprocks to ensure the containment of the injected CO2. Injecting CO2 into porous reservoirs increase the pore pressure, which therefore reduces the effective horizontal and vertical stresses. Depending on the pre-injection stress-condition and permeability of the reservoir, utmost care should be taken to define the upper limit of CO2 injection pressure, in order to prevent any permanent damage to the reservoir which can lead to leakage or induced seismicity. Lab-scale experiments provide key insights to the deformation behavior of reservoir rocks under different stress-conditions, which can be upscaled to understand reservoir scale processes. To simulate the stress perturbation caused by CO2 injection operations, we have subjected porous reservoir rocks (coreplugs) collected from different depths of offshore North Sea under cyclic axial loading and unloading with a confining pressure increment from 10-50 MPa between each cycle. The P and S wave velocities along the axial direction of the coreplugs were recorded in every 10 s to assess the change in wave properties during deformation. It was observed that during each loading cycle, wave velocities are highest at the elastic-plastic transition zone, which can be attributed to the compression of pores and closure of microcracks perpendicular to the loading direction. The wave velocities decrease sharply after the onset of plastic deformation, which can be attributed to the formation of microcracks in the coreplug due to increasing load. The static and dynamic Young’s modulus (E) of the coreplugs during each cycle of increasing confinement show linear increase. Plugs with lower porosity shows higher E with steeper increment at higher confining pressure. The correlation between the wave properties and mechanical response of the reservoir rocks under cyclic loading reveal that constant monitoring of wave velocities during CO2 injection can act as an efficient tool for monitoring stress-state of the reservoir, facilitating safer CO2 storage operations.

How to cite: Chandra, D., Salgado, B. P., and Barnhoorn, A.: Wave velocities as a proxy to forecast deformation during cyclic loading-unloading in porous reservoir rocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4657, https://doi.org/10.5194/egusphere-egu24-4657, 2024.

EGU24-5508 | ECS | Orals | ERE1.8

Cushion gas requirements for hydrogen storage in global underground gas storage facilities 

Mayukh Talukdar, Chinmaya Behera, Niklas Heinemann, Johannes Miocic, and Philipp Blum
To ensure system security and flexibility, storing excess renewable energy as hydrogen is considered an integral component of future energy systems. Cyclic underground hydrogen storage (UHS) with injection production cycles is planned to meet energy demand until new subsurface sites are prepared for storage. To avoid geomechanical risks caused by dynamic pressure fluctuations during cyclic storage, cushion gas is stored in such reservoirs. Cushion gas requirements for sites are still unknown. Therefore, in this study, we calculate the cushion gas requirement of various hydrogen storage sites using reservoir properties.
 
Hydrogen requires less cushion gas by volume than methane. Cushion gas volume in UHS sites varies with the initial reservoir pressure, gas flow rate, well tubing size, and erosional velocity. Cushion gas requirement decreases with increasing reservoir pressure, increasing gas flow, increasing well tubing size, and decreasing erosional velocity. In the studied sites, cushion gas volume ranged from a few % (0-5%) to 99% of the total gas volume. Shallow sites cannot store much hydrogen because of the high cushion gas %. On the other hand, sites deeper than 1100 m are unsuitable owing to insufficient structural trapping and enhanced biogeochemical reactions. Considering these factors, we report the optimum cushion gas volumes for various underground storage sites worldwide.

How to cite: Talukdar, M., Behera, C., Heinemann, N., Miocic, J., and Blum, P.: Cushion gas requirements for hydrogen storage in global underground gas storage facilities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5508, https://doi.org/10.5194/egusphere-egu24-5508, 2024.

EGU24-7216 | ECS | Posters virtual | ERE1.8

Land Use Change Characteristics in the Pan-Pearl River Basin in China from 1985 to 2020 

Wei Fan and Xiankun Yang

The changes in land use/cover are essential aspects of studying the impact of human activities on the Earth's surface and global transformations. In this study, utilizing the ESRI Global Land Cover data (ESRI land cover 2020) and the China Land Cover Data (CLCD), along with historical imagery from Google Earth, a comparative analysis scheme for land use classification results was designed. The CLCD dataset was updated, leading to the creation of a land use dataset for the Pan-Pearl River Basin spanning from 1985 to 2020. This dataset was then employed for the analysis of land use changes in the Pan-Pearl River Basin over the past 35 years.The results indicate:(1) Among the seven land use types, the most significant changes in area occurred in the following order: build -up land, cropland, forest land, grassland, shrubland, waterbody, and barren. Notably, there was a substantial increase in the areas of build-up land and forest land, while cropland, grassland, and shrubland experienced significant decreases. The waterbody’area showed a slight overall increase trend.(2) The major land use types undergoing changes varied among sub-basins, with the intensity of land use change ranked as follows: Pearl River Delta region(1.9%) > Coastal rivers in southern Guangdong and western Guangxi(0.20%) > Dongjiang River Basin(0.13%) > Hanjiang River Basin(0.12%) > Xijiang River Basin(0.10%) > Beijiang River Basin(0.08%) > Hainan Island region(0.02%).(3) Within the sub-basins of the Pan-Pearl River Basin, the most significant increase was observed in the area of built-up land, exhibiting a continuous expansion trend with a total increase of 12184 km2. This increase was primarily due to the conversion of cropland, forest land, and waterbody. The most significant decrease occurred in cropland, with a total reduction of 10435 km2, mainly transitioning to built-up land and forest land. The phenomenon of built-up land encroaching on cropland was particularly prominent, especially in the Pearl River Delta region. Forest land also showed a decreasing trend, mainly attributed to cultivation and the encroachment of built-up land. The reduction in grassland area was more pronounced in the Xijiang River Basin, primarily transforming into forest land, cropland, and built-up land. The study reveals that the rapid development of socio-economics and industry, coupled with an increase in residents' consumption levels, serves as the primary driving force behind land use changes in the Pan-Pearl River Basin. Additionally, land use and management policies play a crucial role as driving factors in the region's land use changes. This research aims to provide a scientific basis for formulating policies related to the region's land resources and land management, holding significant importance for preserving ecological balance and fostering sustainable development in the basin.

How to cite: Fan, W. and Yang, X.: Land Use Change Characteristics in the Pan-Pearl River Basin in China from 1985 to 2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7216, https://doi.org/10.5194/egusphere-egu24-7216, 2024.

EGU24-7761 | Posters on site | ERE1.8 | Highlight

Reutilising hydrocarbon wells as deep heat exchangers to decarbonise heating in the Northern Netherlands  

Johannes Miocic, Jan Drenth, and Pieter van Benthem

To meet the climate targets outlined in the Paris Agreement, European Green Deal, and the goal of reducing dependence on fossil fuel imports per the REPower EU Action, decarbonizing and reducing energy consumption in the heating and cooling sector is imperative. This sector, a major contributor to household energy use, plays a pivotal role in achieving sustainable energy goals.

Geothermal energy, particularly through geothermal doublets, stands out as an ideal solution for supplying energy for space heating and cooling. However, the inherent risks associated with fluid exchange with the subsurface make it scientifically or politically challenging in certain areas. Addressing this concern, deep borehole heat exchangers function as closed-loop systems, eliminating fluid exchange with the subsurface.

In this study, we explore the feasibility of repurposing existing oil and gas wells in the Northern Netherlands as deep coaxial borehole heat exchangers to provide heat to local communities. Utilizing analytical solutions, we calculate the thermal power output of 365 gas wells suitable for retrofitting. These wells exhibit bottom hole temperatures exceeding 80°C, capable of delivering temperatures above 60°C or thermal powers exceeding 800 kW, depending on flow rate and inflow temperature.

Our analysis includes assessing the proximity of well locations to high-density heat demand neighborhoods within a 6 km radius, facilitating the provision of supply temperatures for future local heat district networks. Notably, heat loss from well to neighborhood generally remains below 2°C, ensuring sufficient heating power supply to nearby residential areas. Several well clusters demonstrate significant heat over-supply, suggesting the potential for transporting excess heat to more distant locations. In cases where heat supply from wells is too low, in particularly in neighbourhoods with very low building efficiency rating (<E), heat pumps can be utilised to supply the needed energy.

Our findings indicate that repurposing existing hydrocarbon wells as coaxial heat exchangers offers a viable option for providing low-carbon heating to numerous residential areas in the Northern Netherlands. However, the geographical distribution reveals that not all high heat demand neighbourhoods have well sites in proximity, underscoring the importance of implementing a diverse heat supply strategy.

How to cite: Miocic, J., Drenth, J., and van Benthem, P.: Reutilising hydrocarbon wells as deep heat exchangers to decarbonise heating in the Northern Netherlands , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7761, https://doi.org/10.5194/egusphere-egu24-7761, 2024.

EGU24-8307 | ECS | Posters virtual | ERE1.8

Using machine learning to discriminate between mineral phases and pore morphologies in carbonate systems 

Wurood Alwan, Paul Glover, and Richard Collier

Digital rock models are becoming an essential tool not only for the modelling of fundamental petrophysical processes, but in specific key applications, such as Carbon Capture and Underground Storage (CCUS), geothermal energy exploration, and radioactive waste storage. By utilizing advanced imaging and simulation techniques, digital rocks provide indispensable insights into the porous structures of geological formations, crucial for optimizing CO2 storage, enhancing geothermal reservoir characterization, and ensuring the secure containment of radioactive waste. This abstract aims to present new advances using digital rocks to study these pressing environmental and energy challenges.

Estimating the physical properties of rocks, a crucial and time-consuming process in both the characterisation of hydrocarbon, geothermal and CCUS resources, has seen a shift from traditional laboratory experiments to the increasingly prevalent use of digital rock physics. A key requirement of many forms of pore structure image analysis is that they require binary images showing pore-space vs. non-pore space (mineral phases). These are typically obtained by thresholding grey scale SEM or X-ray tomographic images to separate the two phases. In this paper, we have adapted a 2D process-driven MATLAB model to generate synthetic porous media images, laying the foundation for simulating authentic SEM images. The objective of the computational framework outlined in this study is to train a machine-learning model capable of predicting various types of porosity. Drawing inspiration from recent advances in machine learning applied to porous media research, our approach involves the development of deep learning models utilizing Convolutional Neural Networks (CNN). Specifically, we aim to quantitatively characterize the inner structure of the 2D porous media based on their binary images through the implementation of these CNN models. This framework consists of: (i) Generating synthetic porous media images through a process-driven model, (ii) training a neural network that takes a labelled synthetic image as input and gives two types of porosity as output, (iii) whereupon the trained model can be applied to provide types of porosities for new images that are not in the training database. The generated data are divided into training, validation, and testing datasets. The training dataset optimizes CNN parameters for accuracy, the validation dataset aids in hyperparameter selection and prevents overfitting, and the testing dataset evaluates the predictive performance of the trained CNN model.

This research not only advances the understanding of fundamental geological processes but also plays a crucial role in optimizing the utilization of renewable energy sources such as geothermal and contributing to the effective management of carbon capture and storage initiatives.

How to cite: Alwan, W.S., Glover, P. W. J., and Collier, R.: Using machine learning to discriminate between mineral phases and pore morphologies in carbonate systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8307, https://doi.org/10.5194/egusphere-egu24-8307, 2024.

How to cite: Alwan, W., Glover, P., and Collier, R.: Using machine learning to discriminate between mineral phases and pore morphologies in carbonate systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8307, https://doi.org/10.5194/egusphere-egu24-8307, 2024.

EGU24-8973 | ECS | Orals | ERE1.8

Assessing earthquake focal mechanisms in the North Sea for risk mitigation of large-scale CO2 injections 

Evgeniia Martuganova, David F. Naranjo Hernandez, Daniela Kühn, and Auke Barnhoorn

Decarbonisation of the European economy represents one of the current challenges to both society and the energy sector. The advancement and further application of carbon capture and sequestration (CCS) technologies are crucial components of the EU’s effort to become climate-neutral by 2050. The success of CCS depends heavily on understanding the present-day stress field to anticipate reservoir and cap rock response to fluid injection. Despite its importance, many proposed carbon storage sites in the North Sea are located in areas with little to no borehole stress data available, presenting a significant challenge.

Within the ACT project SHARP Storage framework, we have addressed this gap by generating a comprehensive earthquake bulletin for the North Sea, revealing spatial clusters of seismic events with the majority of earthquakes with ML < 4. Focal mechanisms of earthquakes are excellent indicators of crustal dynamics, which are essential for assessing the present-day stress field. Therefore, to improve the understanding of the in-situ stress conditions, we created a comprehensive workflow to evaluate focal mechanisms based on data from the North Sea (Kettlety et al., 2023). First, we developed a routine for the seismological bulletin to aggregate the recorded earthquakes from international seismological centres. The following step included retrieval of the waveforms from data centres and quality control routines, which included dead channels check, exclusion of files with significant recording gaps and low signal-to-noise ratio, and corrections of errors in the station XML files. Then, a subset of data traces with sufficient quality was selected for moment tensor computations using a Bayesian bootstrap-based probabilistic inversion scheme (see Heimann et al., 2018). Using existing focal mechanism solutions for the North Sea region, we calibrated our processing routine and then applied it to selected earthquakes (after 1990, M > 3.5) to expand the existing focal mechanisms database.

The newly computed focal mechanism solutions provide valuable insight into the present-day stress field in areas outside the main hydrocarbon provinces and improve the risk assessment of ongoing and future CCS projects. Furthermore, we will release our processing workflow as an open-source package and a new focal mechanisms database of the North Sea to establish a standard processing routine that can be readily utilised for similar seismological studies.

How to cite: Martuganova, E., Naranjo Hernandez, D. F., Kühn, D., and Barnhoorn, A.: Assessing earthquake focal mechanisms in the North Sea for risk mitigation of large-scale CO2 injections, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8973, https://doi.org/10.5194/egusphere-egu24-8973, 2024.

EGU24-9206 | ECS | Orals | ERE1.8

Storage potential of CO2 by repurposing oil and gas-related injection wells in the Montney Play, northeast British Columbia, Canada 

Hongyu Yu, Bei Wang, Honn Kao, Ryan Visser, and Malakai Jobin

From 2005 to 2020, Canada achieved a 9.3% reduction in green house gas emission (69 Mt CO2 eq), meanwhile British Columbia witnessed a 5% increase (3.0 Mt CO2 eq) from 2007 to 2019. Exploiting unconventional oil and gas resources in northeast British Columbia (NEBC) has become the province’s second-largest source of greenhouse gas emissions. In pursuit of a cost-effective and seismic risk-aware approach for carbon emission reduction, this study evaluates the CO2 geological storage capacity in NEBC with a focus on repurposing existing injection wells for carbon storage.

We particularly emphasize the Montney and Debolt formations. These formations are the main targets of a diverse array of injection wells, including those for hydraulic fracturing, enhanced hydrocarbon recovery, and wastewater disposal. Three trapping mechanisms in the NEBC area are examined: physical and solubility trapping for wastewater disposal wells in the Debolt Formation, and physical and mineral trapping for hydraulic fracturing and enhanced recovery wells in the Montney Formation. Furthermore, we incorporate an assessment of seismic hazards, informed by the latest insights into injection-induced seismicity in NEBC, as a potential indicator of CO2 leakage risk.

Our findings underscore the favorable conditions of the Debolt Formation with lower seismicity hazard and a substantial CO2 storage capacity (19.3 Gt; ~284.4 years of CO2 emissions in BC). Depleted oil and gas reservoirs within the Montney Formation are also deemed suitable for CO2 storage, estimated at 1671.8 Mt (approximately 24.5 years), particularly in the Upper Montney due to its higher storage capacity and lower seismic risk.

Overall, this research offers an assessment of CO2 geological storage potential at the formation-scale in NEBC. The emphasis on well suitability and seismic risks effectively bridges the gap between the regional-scale geological assessments and site-scale engineering evaluations. It paves the path for future studies on addressing more practical topics related to the choices of project sites and injection strategies.

How to cite: Yu, H., Wang, B., Kao, H., Visser, R., and Jobin, M.: Storage potential of CO2 by repurposing oil and gas-related injection wells in the Montney Play, northeast British Columbia, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9206, https://doi.org/10.5194/egusphere-egu24-9206, 2024.

EGU24-9509 | ECS | Orals | ERE1.8

Quantifying flow reduction during injection of CO2 into legacy hydrocarbon reservoirs for CCUS 

Qian Wang, Glover Paul, and Lorinczi Piroska

In the development of hydrocarbon fields, it is becoming known that CO2 injection (which is sometimes done to improve hydrocarbon production) can cause pore blockage and wettability alteration by the promotion of asphaltene deposition. In hydrocarbon reservoirs, the result is poor oil recovery performance during carbon dioxide (CO2) injection. If CO2 is being injected into a legacy hydrocarbon reservoir (i.e., one that still contains residual oil) the same process will occur. Once again, the ability of fluid (this time supercritical CO2) to flow will be impeded, but it is also possible that asphaltene deposition will also reduce the overall pore volumes in which CO2 could otherwise be stored. In this work, the residual oil distribution and the permeability decline caused by organic and inorganic precipitation after miscible CO2 flooding and water-alternating-CO2 (CO2-WAG) flooding have been studied by carrying out core-flooding experiments at high pressures and temperatures in an artificial three layer system. For simple CO2 injection during CCUS operations, flooding experimental results indicate that the low-permeability layers retain a large oil production potential even in the late stages of production, which could impede CO2 emplacement and provide significant heterogeneity, while the permeability decline due to asphaltene precipitation is more significant in high-permeability rocks. In contrast, we found that CO2-WAG can reduce the influence of heterogeneity on the oil production, but it results in more serious reservoir damage, with permeability decline caused by CO2–brine–rock interactions becoming significant. In addition, miscible CO2 flooding has been carried out for rocks with similar permeabilities but different wettabilities and different pore-throat microstructures in order to study the effects of wettability and pore-throat microstructure on formation damage. Reservoir rocks with smaller pore-throat sizes and more heterogeneous pore-throat microstructures were found to be more sensitive to asphaltene precipitation, making these less attractive for CCUS reservoirs. However, rocks with larger, more connected pore-throat microstructures became less water wet due to asphaltene precipitation to pore surfaces, ultimately leading to a lower pore volume in which CO2 can be stored. Taken together, there may be a case for not simply injecting CO2 in CCUS operations, but alternating the CO2 injection with injection of water in order to stabilise CO2 flow and reduce formation damage by asphaltene precipitation.

How to cite: Wang, Q., Paul, G., and Piroska, L.: Quantifying flow reduction during injection of CO2 into legacy hydrocarbon reservoirs for CCUS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9509, https://doi.org/10.5194/egusphere-egu24-9509, 2024.

Though global energy needs continue to grow, fossil fuels, and their associated CO2 emissions, are increasingly being opposed as our main source of energy. Instead, to achieve net zero greenhouse gas emissions goals, we are currently transitioning to more sustainable sources of energy, such as solar and wind power and geothermal energy, coupled with storage of waste, such as CO2. However, these new technologies come with their own challenges, as they continue to rely on (re-)use of the subsurface landscape. The intermittency of solar and wind power will require storage of renewably generated electricity. Hydrogen fuel has been marked as a potential energy carrier, enabling us to store large quantities of energy for prolonged periods of time, such as required to supply large industries or communities during winter months. To store this hydrogen fuel, the subsurface offers the largest storage space available, such as in (offshore) depleted hydrocarbon fields, but reproduction of the stored fluid is crucial. Geothermal energy production will require the extraction of hot fluids from depth and will often be performed in populated areas, close to the consumers, meaning that phenomena such as surface subsidence and induced seismicity are highly undesirable. The safe storage of CO2 for thousands of years also entails fluid injection, but containment is of vital importance to keep the CO2 out of our atmosphere. So though we have a vast history of exploitation of the subsurface through the oil and gas industry, which we can and should build upon, these new sustainable energy developments also pose their own, new challenges. While fluid production changes the physical equilibrium of the system, these new uses will also impact the chemical equilibrium through the injection of new fluids. Furthermore, containment and safety play an even bigger role than before to ensure the longevity of these new subsurface operations. In this contribution, I will outline what the challenges are that we are facing and how geoscientists can contribute to solving these challenges, across all areas from rock physics, geochemistry and hydrology, to sedimentology, structural geology and policy.

How to cite: Hangx, S.: Same same but different: the scientific challenges when re-using the subsurface for sustainable energy developments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12486, https://doi.org/10.5194/egusphere-egu24-12486, 2024.

EGU24-12846 | Posters on site | ERE1.8

Exploring the Relationship between CT Scanning Resolutions and Sandstone Porosity for CCS Applications 

Jyh-Jaan Steven Huang, Yao-Ming Liou, Arata Kioka, and Tzu-Ruei Yang

In the context of Carbon Capture and Storage (CCS), the porosity of potential storage formations is a critical factor. Our study explores this aspect using computed tomography (CT) to assess how different scanning resolutions impact the accuracy of porosity measurements. We employed three CT systems - Geotek RXCT (resolution ~20-150 μm), Bruker 1272 (resolution ~5 μm), and DELab μCT-100 (resolution ~9 μm) - to scan sandstone cores of varying porosities. The aim was to identify an optimal scanning resolution that balances detail with practicality for CCS evaluations.

This research addresses the challenges in high-resolution CT scanning, such as denoising effects that can alter accuracy, and the complexities of thresholding segmentation across various systems. Additionally, we examined the partial volume effect, crucial for interpreting pore sizes and distributions accurately.

Our preliminary results suggest that scanning resolution significantly affects the perceived porosity. Different resolutions uncover diverse aspects of pore structure, highlighting the importance of choosing an appropriate resolution. Advanced image processing techniques, including effective denoising and accurate thresholding, are vital for reducing errors in porosity measurement.

The study provides valuable insights into the use of CT scanning for CCS applications, emphasizing the need for a balanced approach in resolution selection and sophisticated image processing. These findings are instrumental in enhancing the reliability of geological evaluations for potential CCS sites, contributing to the broader efforts in carbon storage and climate change mitigation.

How to cite: Huang, J.-J. S., Liou, Y.-M., Kioka, A., and Yang, T.-R.: Exploring the Relationship between CT Scanning Resolutions and Sandstone Porosity for CCS Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12846, https://doi.org/10.5194/egusphere-egu24-12846, 2024.

EGU24-13835 | ECS | Posters on site | ERE1.8

Characterising functionalised nanoparticles for improving fluid flow for CCUS in legacy hydrocarbon reservoirs  

Louey Tliba, Afif Hetnawi, Farad Sagala, Robert Menzel, Paul Glover, and Ali Hassanpour

In recent years there has been rapid development of nanoparticles (NPs). Nanoparticles can be used both as a probe into restricted spaces, such as the pores within a reservoir rock, and as tools for altering wettability or deliberately blocking pore throats to enhance fluid movement in less connected pores. Silica nanoparticles can have functional surfaces allowing them to react specifically to oils or water. Nanoparticles can be used to enhance oil production by releasing oil on mineral surfaces and improving fluid flow. However, they also have the potential for improving CO2 flow in CCUS reservoirs while enhancing the pore volume available for CO2 storage. In this paper we evaluate the performance of different non-functionalised and functionalised nanoparticles for enhancement of oil production, CO2 emplacement and gas flow. Different forms of silica NPs have been made, either unfunctionalized, or functionalised with branched amino-based polymer (hydrophilic) or a silane-based agent (hydrophobic). Their stability has been characterised using a range of laboratory methods. The microscopic performance of the nanoparticles has been measured using contact angle measurements. Their ability to enhance oil production and CO2 emplacement has been tested using imbibition and drainage experiments. 

The contact angles, measured in the presence of brine, no modified silica NPs, branched amino-based polymer (hydrophilic) modified silica NPs and silane-based agent (hydrophobic) modified silica NPs showed contact angle values of approximately 110°, 116°, 124°, and 136°, respectively. These results show that introduction of nanofluids led to a change in substrate wettability from water-wet to strongly water-wet. Notably amongst the tested nanoparticles the Silane-based NPs demonstrated the highest hydrophilic surface. The spontaneous imbibition tests conducted on various sandstone cores revealed that silane-based NPs yielded the highest oil recovery rates among the tested NPs. Specifically, these nanoparticles showed an approximate 12% and 50% enhancement in oil recovery compared to non-modified silica nanoparticle, and branched amino-based polymer (hydrophilic) modified silica NPs. In summary, nanofluids have been shown to substantially improve the wettability alteration of the rock surface from oil-wet to water-wet, which can lead to improve the volume and flow characteristics of legacy CCUS prospects. Our future plan is to investigate the enhancement of carbon dioxide (CO2) solubility in brine through the utilization of the prepared nanoparticles, with the objective of advancing carbon capture technologies.

How to cite: Tliba, L., Hetnawi, A., Sagala, F., Menzel, R., Glover, P., and Hassanpour, A.: Characterising functionalised nanoparticles for improving fluid flow for CCUS in legacy hydrocarbon reservoirs , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13835, https://doi.org/10.5194/egusphere-egu24-13835, 2024.

EGU24-14959 | Orals | ERE1.8

TRANSGEO - Transforming abandoned wells for geothermal energy production 

Hannes Hofmann, Julie Friddell, Ingo Sass, Thomas Höding, Katrin Sieron, Max Svetina, Monika Hölzel, Robert Philipp, György Márton, Balázs Borkovits, Klára Bődi, Alen Višnjić, Tomislav Kurevija, and Bojan Vogrinčič

TRANSGEO is a regional development project that aims to explore the potential for producing sustainable geothermal energy from abandoned oil and gas wells in central Europe.  Composed of 11 partner organizations and 10 associated partners in 5 countries, TRANSGEO is developing a Transnational Strategy and Action Plan to address this technical and economic opportunity.  Our primary objective is to support rural communities and industries in the energy transition by providing tools and information that highlight sustainable redevelopment priorities and opportunities.

To reach this objective and promote the switch from fossil fuels to green energy, TRANSGEO is developing reuse procedures for five different geothermal technologies and validating them via numerical modelling, to assess their performance in repurposing existing hydrocarbon infrastructure and determine the optimal reuse conditions and configurations.  The five geothermal technologies are Aquifer Thermal Energy Storage, Borehole Thermal Energy Storage, Deep Borehole Heat Exchangers, Enhanced Geothermal Systems, and Hydrothermal Energy production.  The modelling studies focus on reference sites in our study areas, the North German Basin, the South German Molasse Basin, the Vienna Basin, and the Pannonian Basin.  Comparison of varying wellbore and reservoir parameters in the numerical modelling studies will provide input to a new online well assessment tool which will be available publicly to determine well suitability and guide planning for future reuse projects.  The online tool will be informed by a database of abandoned wells in Austria, Croatia, Germany, Hungary, and Slovenia and will include local reference data, such as geology, topography, heat demand, and utilities.  This will facilitate well reuse by matching candidate wells with local energy demand and heating networks.  Additional work on socio-economic and policy analyses will provide financial and liability information for the 5 different geothermal technologies, across the project countries.  Finally, the partnership will propose a legal policy and incentive framework to facilitate and expand reuse of abandoned wells for geothermal energy production and storage across central Europe.

TRANSGEO is co-funded by the European Commission’s Interreg CENTRAL EUROPE programme.

How to cite: Hofmann, H., Friddell, J., Sass, I., Höding, T., Sieron, K., Svetina, M., Hölzel, M., Philipp, R., Márton, G., Borkovits, B., Bődi, K., Višnjić, A., Kurevija, T., and Vogrinčič, B.: TRANSGEO - Transforming abandoned wells for geothermal energy production, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14959, https://doi.org/10.5194/egusphere-egu24-14959, 2024.

EGU24-16266 | ECS | Orals | ERE1.8

Geological characterization of the “Fonts-Bouillants” helium discovery - France 

Russier Emma, Géraud Yves, Hauville Benoît, Tarantola Alexandre, Beccaletto Laurent, and Diraison Marc

Geological characterization of the “Fonts-Bouillants” helium discovery - France

Russier E1,2, Géraud Y2, Hauville B1, Tarantola A2 ,Beccaletto Land Diraison M1

1 45-8 ENERGY, France

2 GeoRessources, University of Lorraine, France

3 BRGM, F-45060, Orléans, France

 

ABSTRACT

Helium is essential for the manufacturing of many of our daily commodities such as optical fibres, computers or cell phones (semiconductors and processors), medical use (MRI scanners) or in other more specific applications such as airlifts, leak detection, gas chromatography or diving. Nowadays, Europe imports 100% of its helium needs from overseas and is facing regular shortages, reason why 45-8 Energy embarked five years ago on helium exploration and production in Europe.

 

Helium is a noble gas mostly coming from the natural radioactive decay of Uranium and Thorium contained in the crust and the basement. Its migration and accumulation are strongly linked to a vector fluid that can be CO2, N2, CH4 or water. Helium and its vector fluids are then trapped and sealed in a rock reservoir.

 

The Fonts-Bouillants area is located at the southern edge of the Paris Basin at the vicinity of the French Massif Central and Limagne rift. The 45-8 Energy project aims to jointly produce He and CO2 from a gas which is naturally seeping through the major Saint-Parize fault (SPF).  Geological origin and migration pathway of He are therefore key questions to define the exploration guide, in particular to locate production wells to produce the seeping gas and process it. A multidisciplinary approach involving geology, geophysics, petrophysics and geochemistry has therefore been deployed.

 

Because geological context was hardly documented in this area, a wide range of geophysical data were acquired or reprocessed and coupled with field geology to build a regional geological model. The initial geological model was considerably updated and a hidden and thick Late Palaeozoic depocenter was especially highlighted below the Mesozoic series. Well data in nearby analogous basins as well as outcrops enabled rock collections to conduct petrophysical and geochemical characterization. The main reservoirs discovered currently are in Triassic and Jurassic sandstones, and fault like Saint-Parize fault acted as barrier and drain. 

Our outcrops petrophysical and geochemical study highlight the importance of Late Palaeozoic basin for the helium system:

  • As a potential rock source, with higher U-Th concentrations (3-13.5, 8-24 ppm) than typical crustal U-Th concentrations (1.8 and 7.2 ppm, [1]).
  • As a potential migration pathway and reservoir, with sandstones and conglomerates porosity higher than 20% and permeability higher than 100 mD.

 

Finally, gas sampling was performed in local natural springs, but also during well testing conducted in shallow boreholes which have encountered gas bearing reservoirs in the Mesozoic along the SPF. Helium generation system was modelled with geochemical data from the rocks and the fluids and from the volumetric capacity of the Palaeozoic basin.

 

Keywords: Helium exploration, Geophysics, Petrophysics, Geochemistry

Themes: Helium exploration

 

References:

[1] Krauskopf, K. B., & Bird, D. K. (1967). Introduction to geochemistry (Vol. 721). McGraw-Hill New York.

 

How to cite: Emma, R., Yves, G., Benoît, H., Alexandre, T., Laurent, B., and Marc, D.: Geological characterization of the “Fonts-Bouillants” helium discovery - France, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16266, https://doi.org/10.5194/egusphere-egu24-16266, 2024.

Natural gas storage is currently considered as one key pillar of the EU strategy to ensure security of energy supply. In view of CH4 storage, Oldenburg [1] demonstrated in a theoretical study that using CO2 as cushion gas instead of CH4 has the advantage of increasing natural gas storage capacities of geologic reservoirs by up to 30 %. This is due to CO2 undergoing a significant density change when its’ critical pressure is exceeded during CH4 injection. Kühn et al. [2] investigated a comparable scenario with CH4 gas storage in a closed cycle with CO2 in one reservoir to temporarily store and reuse wind and solar energy. However, the potential qualitative degradation of the stored CH4 due to mixing with the CO2 cushion gas has not yet been sufficiently addressed in terms of the impact of the modeller’s choice of diffusion coefficients. Hence, the present study focuses on a quantitative assessment of the mixing behaviour of CH4 and CO2 under consideration of dynamic binary diffusion coefficients in a reference numerical simulation benchmark [1,3]. The TRANSPORTSE numerical simulator [4,5] is used with dedicated measures to mitigate the initially high numerical dispersion, introduced by the benchmark’s relatively coarse grid discretisation. The simulation results show that the mixing region is substantially reduced if dynamic binary diffusion coefficients are applied instead of a global constant for both gas components. Consequently, it is demonstrated that previous numerical assessments of natural gas storage with a carbon dioxide cushion gas overestimate the simulated CH4-CO2-mixing area, and thus the calculated mixing losses. Hence, combined gas storage of CH4 and CO2 is more efficient than expected so far.

[1] Oldenburg, C. M. (2003) Carbon Dioxide as Cushion Gas for Natural Gas Storage. Energy Fuels 17(1), 240−246. https://doi.org/10.1021/ef020162b

[2] Kühn, M., Nakaten, N. C., Streibel, M., Kempka, T. (2014): CO2 Geological Storage and Utilization for a Carbon Neutral “Power-to-gas-to-power” Cycle to Even Out Fluctuations of Renewable Energy Provision. Energy Procedia, 63, 8044-8049. https://doi.org/10.1016/j.egypro.2014.11.841

[3] Ma, J., Li, Q., Kempka, T., Kühn, M. (2019) Hydromechanical Response and Impact of Gas Mixing Behavior in Subsurface CH4 Storage with CO2-Based Cushion Gas Energy & Fuels 33 (7), 6527-6541. https://doi.org/10.1021/acs.energyfuels.9b00518

[4] Kempka, T. (2020) Verification of a Python-based TRANsport Simulation Environment for density-driven fluid flow and coupled transport of heat and chemical species. Advances in Geosciences, 54, 67-77. https://doi.org/10.5194/adgeo-54-67-2020

[5] Kempka, T., Steding, S., Kühn, M. (2022) Verification of TRANSPORT Simulation Environment coupling with PHREEQC for reactive transport modelling. Advances in Geosciences, 58, 19-29. https://doi.org/10.5194/adgeo-58-19-2022

How to cite: Kempka, T. and Kühn, M.: Geologic CH4 storage with CO2 cushion gas: using dynamic binary diffusion coefficients instead of a global constant in numerical simulations is more precise and results in lower mixing losses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17184, https://doi.org/10.5194/egusphere-egu24-17184, 2024.

Since the end of the XIX century, many wells have been drilled worldwide for both Oil & Gas exploration purposes. Most of them are now abandoned and subjected to mining closure because exhausted or sterile. In the new epoch of energy transition scenario, the possibility to adapt and reuse these existing boreholes to exploit geothermal energy seems very promising. In fact, considering that approximately 40% of the total costs for a new geothermal project are devoted to drilling activity, the possibility of repurposing abandoned oil and gas wells offers a wide range of applications and exploitation of underground heat uses. The drilled borehole available data (e.g., underground temperature, lithology) provide helpful information about the sub-surface reservoirs, reducing the mining risk level, and wells allow direct access to the sub-surface heat energy. However, to develop a commercially viable geothermal power/thermal generating system, one must consider several factors, i.e., available prospecting, drilling and reservoir technologies, energy costs in the area, and resource durability.

This research aims to analyze the potential and feasibility of deep closed-loop systems solutions for heat and power energy production in Italy, in areas characterized by both normal and anomalous geothermal gradients and the distribution of available abandoned oil and gas wells. A prominent result is the development of a workflow leading to the feasibility assessment of deep closed-loop systems development, based on the identification of suitable abandoned O&G wells through the geological and thermal underground characterization and wells construction characteristics (diameter, depth, borehole material). Furthermore, a sensitivity analysis of the main parameters affecting most of the retrofitting of abandoned wells for geothermal purposes is performed thanks to thermal FEM modelling.

Finally, identifying the possible end-users in a suitable case study area, this research work provides preliminary insights into the quantity of thermal energy and electric power that this technology could produce.

How to cite: Facci, M. and Galgaro, A.: Numerical sensitivity analysis of energy performance of geothermal deep closed loop heat exchangers derived from the reuse of abandoned oil and gas wells, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17674, https://doi.org/10.5194/egusphere-egu24-17674, 2024.

EGU24-18605 | Orals | ERE1.8

Modelling dynamics of sedimentary basins: using geological history to predict subsurface activities at large-scale 

Claude Gout, Marie-Christine Cacas-Stentz, Adriana Traby, and Nathalie Collard

The dynamics of sedimentary basins is a complex combination of synchronous generally non-linear processes. In these natural systems, fluids migration and associated transfers play a fundamental role, even more so as they represent resources that are or may become essential for human societies. One way of assessing the potential of sedimentary basins is to model their past behaviour numerically.

Basin models have been developed since the 1990s for the needs of the oil industry, with the initial aim of assessing the thermal history, i.e. the maturation and expulsion of hydrocarbons from source rocks with variable kinetics and initial composition. These models are used for hydrocarbon prospect assessment in a wide range of sedimentary basins. They have evolved with the integration of the simulation of compaction mechanisms and fluid migration by Darcean single-phase or multi-phase flows. Still with an operational objective in mind, one of these models has been extended to simulate the transport of thermal energy and chemical elements in fluids, thereby helping to assess the geothermal and large-scale storage potential of a basin. The explicit representation of faults and unconformities, as well as the calculation of seal or reservoir formation fracturing as a function of fluid pressures, enables the plumbing system to be represented on a basin scale. In this network of drains, single- or multiphase fluids carrying compounds can interact with the rocks, according to the principles of reactive transport. Some of these simulations are being experimented using AI techniques. In these digital experiments, elements tracking could be a true added value for basin’s dynamics understanding.

A coupled simulation of this kind, combining conductive and advective thermal physics, mechanics (particularly of porous media), the hydraulics of multiphase fluids in porous media, chemistry of reactive transport and even the impact of bioactivity on basin’s fluids, representing geological processes in the subsurface on a large scale, makes it possible to quantify mass and energy transfers in the past. The result is a physically balanced model of the current spatial distribution of pressure, stress, temperature, mass, solid or fluid elements.

These results can be useful both in economic applications for first-order assessment of the resources of any sedimentary basin and in the scientific field for defining the boundary conditions of more specialised models. Initial experiments demonstrating the use of multiphysics models on a basin scale for CCS applications and geothermal energy assessment will be shown.

How to cite: Gout, C., Cacas-Stentz, M.-C., Traby, A., and Collard, N.: Modelling dynamics of sedimentary basins: using geological history to predict subsurface activities at large-scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18605, https://doi.org/10.5194/egusphere-egu24-18605, 2024.

With the advancement of exploration theory and technology, deep and ultra-deep carbonate rocks have gradually become an important new field for the development of oil and gas resources. High-quality carbonate reservoirs have become the focus of attention for oil and gas exploration and research in deep and ultra-deep fields. The Tarim Basin is the largest intracontinental oil and gas basin in China. The thick carbonate strata developed in the Lower Paleozoic are the main layers for oil and gas exploration, and the Ordovician carbonate strata are the main oil and gas producing layers. The predecessors have studied the tectonic evolution, sedimentary background and rock types of the Ordovician in the Tarim Basin. Combined with the analysis of the sedimentary thickness, lithology distribution and seismic profile structure of the Early Ordovician, it is believed that the Lower Ordovician sedimentary period inherited the Cambrian sedimentary pattern and transformed it into a gentle slope sedimentary background with a 'uplift-sag 'pattern, with obvious differentiation. Under the sedimentary background of the gentle slope of the Penglaiba Formation, the three paleo-uplifts of southwestern, northern and central Tarim are inherited geomorphological highs, and the inner gentle slope tidal flat facies is developed. The thickness of the stratum is obviously thinner, and it is mainly developed to represent the tidal flat environment. The periclinal part around the paleo-uplift is the middle gentle slope, which is characterized by dolomite and limestone interbeds. The proportion of granular rocks is high, which is a favorable development area for granular beaches. In this study, the deep drilling cores of the Lower Ordovician Penglaiba Formation in the central Tarim Basin were taken as the key research object, and the lithofacies, reservoir characteristics and dominant reservoir control factors of dolomite reservoirs were systematically analyzed by using macro-micro, qualitative-quantitative reservoir petrology analysis methods. Through research, it is clear that the rock types of the Lower Ordovician Penglaiba Formation in the central Tarim Basin are mainly crystalline dolomite and ( residual ) granular dolomite, and also contain a small amount of limestone, siliceous rocks and transitional rocks. There are various types of reservoir space, mainly including non-fabric selective dissolution pores, intercrystalline pores and various fractures. Combined with previous studies on the genesis and diagenetic evolution of the Lower Ordovician dolomite in the Tarim Basin, it is considered that the development of high-quality dolomite reservoirs in the Lower Ordovician Penglaiba Formation in the central part of Tarim Basin is controlled by many factors. It is the result of a combination of favorable sedimentary facies belts, short-term sea-level changes, exposure and dissolution, early dolomitization, and late tectonic hydrothermal adjustment and transformation.

How to cite: Li, X. and Xu, Q.: Development characteristics and controlling factors of deep dolomite reservoirs of Lower Ordovician in Tazhong area, Tarim Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20142, https://doi.org/10.5194/egusphere-egu24-20142, 2024.

Seismic data integration plays a pivotal role in enhancing the capabilities of geological modelling

software. Our current research focuses on the improvement of seismic interpretation tools within the

PZero software in the framework of the Geosciences IR project lead by the Italian Geological

Survey GitHub - andrea-bistacchi/PZero. The objective is to seamlessly incorporate seismic data

into the geological modelling workflow, enabling more comprehensive and accurate models of

subsurface structures.

The initial phase of our work involved using various libraries to import and analyze seismic

datasets, either 2D or 3D within the PZero framework. We have successfully achieved the

importation of SEGY files into PZero, marking a significant milestone in our efforts. Integrating

seismic data is a crucial step that sets the foundation for constructing detailed geological models,

allowing us to enhance our understanding of subsurface geological features.

Soon, our research trajectory aims to develop advanced algorithms for stochastic simulation tailored

explicitly for modelling clastic sedimentary alluvial plains. The ongoing work includes developing

advanced stochastic simulation algorithms tailored for modelling clastic sedimentary environments,

relevant to both conventional energy resources and emerging sustainable energy storage solutions.

These advancements in seismic data integration and simulation within PZero will significantly

contribute to the field of reservoir modelling. They provide a robust framework for predicting the

behavior of subsurface energy storage systems, which is pivotal in the transition to a low-carbon

energy future.

How to cite: Hussain, W. and Bistacchi, A.: Advancements in Seismic Data Integration and Stochastic Simulation for Geological Modeling in PZero, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22365, https://doi.org/10.5194/egusphere-egu24-22365, 2024.

EGU24-1239 | Posters on site | TS2.1

Constraints on the Formation Age of the Chukchi Basin, Arctic Ocean, inferred from Marine Heat Flow Measurements 

Young-Gyun Kim, Jong Kuk Hong, Young Keun Jin, and Byung Dal So

The Amerasia Basin, one of two major basins that comprise the Arctic Ocean, is thought to have a more complex formation history than its counterpart, the Eurasian Basin. Because the harsh conditions for marine expeditions last the entire year, there is a lack of observational data for constraining the tectonic history of the Chukchi Basin. Thus, there are multiple existing hypotheses for its tectonic history, with contrasting formation ages ranging from Mesozoic to Cenozoic and crustal types ranging from hyper-extended continental crust to oceanic crust. Recently, during the 2018 and 2021 Arctic expeditions of the Korean ice-breaking research vessel Araon, we obtained the new marine heat flow data along the east-west and northeast-southwest transect lines from the abyssal plain to the continental slope/shelf of the basin. These data may play an important role in constraining the formation age of the basin, as the extending axis among the hypotheses is likely oriented from north-south. Assuming an oceanic crust, the formation age can be inferred to be Late Cretaceous. This information concerning the formation age enhances our understanding of the underestimated complex tectonic history of the Amerasia Basin, because such inferred timing aligns with the formation age of the adjacent Chukchi Borderland.

How to cite: Kim, Y.-G., Hong, J. K., Jin, Y. K., and So, B. D.: Constraints on the Formation Age of the Chukchi Basin, Arctic Ocean, inferred from Marine Heat Flow Measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1239, https://doi.org/10.5194/egusphere-egu24-1239, 2024.

EGU24-1615 | ECS | Orals | TS2.1

Evolution and activation of an orogen-scale shear zone in the northern Aegean Rift System: insights from the Mykonos Detachment, Cyclades, Greece 

Costantino Zuccari, Francesco Mazzarini, Enrico Tavarnelli, Giulio Viola, Luca Aldega, Roelant Van der Lelij, and Giovanni Musumeci

Extensional detachments are commonly considered key structures in accommodating the exhumation of deeply buried or subducted crustal slivers, and in facilitating the syndeformation emplacement of plutons during the evolution of wide rift systems (i.e., Basin and Range type). In those settings, ductile shear zones and brittle faults may act for several million years to accommodate important vertical and horizontal displacements such that multiply reactivated and highly complex shear zones and faults may form. The analysis of these complexities, together with the possibility to constrain the age of strain and deformation localisation, is thus pivotal in reconstructing the onset and evolution of the processes that steer(ed) the crustal extension.

Aiming at better understanding these structural/chronological intricacies, we have studied the brittle Mykonos Detachment (MD), which is thought to have facilitated the emplacement of the Mykonos granite starting in the Middle Miocene (~14-9 Ma) and following the activation of the earlier (ductile) Livada Detachment (LD) that would have favoured the beginning of pluton cooling during the structuring of the Aegean rifting. The Mid. Miocene age of the MD is, however, only loosely constrained by the stratigraphic age of syn-tectonic siliciclastic deposits in the hanging wall of the fault. No absolute ages exist yet on the activation of the brittle MD or the ductile LD, and a detailed description of the internal architecture of the MD is still not available.

Aiming to fill this gap(s), we carried out a detailed study that couples a Brittle Structural Facies – based structural analysis with K-Ar dating on authigenic illite from fault gouge(s) that compose the MD fault core. Fault gouges normally rest on and are cut by the MD principal slip surface (PSS), which reasonably postdates the gouge formation and represents the effects of the latest fault activity. We have obtained a 7.1 ± 0.1 Ma K-Ar age from a fault gouge suggesting that the MD activation postdated the widely accepted ~14-9 Ma of the granite cooling, also considering that the PSS postdates the 7.1 Ma gouge, as indicated by field evidence. On this ground, together with published thermochronological data showing that the granite experienced a rapid cooling from ~14 to ~11 Ma before experiencing slow cooling until ~9 Ma, we can state that most of the granite exhumation cannot be ascribed to the MD, the activation of which postdates the late stage of the granite cooling.

These new geochronological data (which are soon to be implemented with new K-Ar dates) and the description of the architectural evolution of the MD fault zone, stress the role of the detachment during the unroofing of the Mykonos granite in the Aegean rifting context. In this perspective, the granite exhumed is mostly assisted by the ductile LD, which acted before the MD. The latter acted instead only at a later stage when it juxtaposed the Miocene siliciclastic against an already cooled and unroofed granite, which had reached a temperature of ~40°C about 2Ma before the latest Late Miocene activation of the MD, as shown by our preliminary age constraint.

How to cite: Zuccari, C., Mazzarini, F., Tavarnelli, E., Viola, G., Aldega, L., Van der Lelij, R., and Musumeci, G.: Evolution and activation of an orogen-scale shear zone in the northern Aegean Rift System: insights from the Mykonos Detachment, Cyclades, Greece, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1615, https://doi.org/10.5194/egusphere-egu24-1615, 2024.

A new onshore-offshore 3-D constrained gravity inversion methodology that incorporates onshore topography and laterally variable inversion mesh depths is used to determine the crustal density distributions, Moho depths, and crustal thicknesses of Iberia, Morocco, and their respective rifted continental margins. The results largely show an excellent correspondence with crustal characteristics determined from sparsely distributed controlled-source and passive seismic experiments, while also allowing the layered density structure of the region to be explored and analyzed in terms of upper, middle, and lower crustal layers. These detailed regional views as a function of depth can improve characterization of crustal types (continental versus oceanic versus transitional), and the resulting interpretations can be directly compared against equivalently derived crustal characteristics for onshore-offshore Atlantic Canada, which encapsulates both Iberia’s and Morocco’s conjugate rifted margins. Collectively, the conjugate 3-D crustal-scale density models allow for the extraction of mega-transects across both sides of the southern North Atlantic, joined together back through geological time using kinematic plate reconstructions.

How to cite: Welford, J. K.: Crustal structure of onshore-offshore Iberia, Morocco, and their rifted continental margins, from constrained 3-D gravity inversion using variable mesh depths, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3196, https://doi.org/10.5194/egusphere-egu24-3196, 2024.

EGU24-3979 | ECS | Posters on site | TS2.1

Three-dimensional crustal velocity structure of the north-eastern Gulf of Aden continental margin 

Jie Chen, Sylvie Leroy, Louise Watremez, and Adam Robinson

Continental rifting is the Earth’s fundamental tectonic process that may result in a new plate boundary, i.e., mid-ocean ridges, with the accretion of new oceanic crust. At present, continental rifted margins are classified into two end-members based on the amount of magmatism that occurred during the rifting process: magma-rich and magma-poor. However, various factors influence the formation of these margins, such as the inheritance of segmentation, extension obliquity, syn-rift magmatism, and sedimentation. The Gulf of Aden represents a good example for understanding such spatial variations in the formation of rifted margins. It consists of an oblique rifting system, with young and segmented margins (34-17.6 Ma) and thin sediments. In addition, the Gulf of Aden exhibits magma-rich margins in the west, related to the Afar hotpot, and magma-poor margins in the east, with a possible zone of exhumed continental mantle.

In this study, we develop a 3-D P-wave velocity model across the north-eastern Gulf of Aden continental margin, using wide-angle seismic refraction data from a combined onshore-offshore survey with 35 ocean-bottom seismometers and 13 land seismometers. Approximately 187,000 P-wave first arrivals were picked and inverted in 3-D, with the modelling informed by constraints from previously published 2-D velocity models. Here, we present our preliminary tomographic results that illustrate the spatial variations in the crustal velocity structure of the continent, continent-to-ocean transition (COT), and oceanic domains, as well as the comparison between our 3-D and the published 2-D velocity structures of the north-eastern Gulf of Aden continental margin.

How to cite: Chen, J., Leroy, S., Watremez, L., and Robinson, A.: Three-dimensional crustal velocity structure of the north-eastern Gulf of Aden continental margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3979, https://doi.org/10.5194/egusphere-egu24-3979, 2024.

During the final stages of breakup at magma-poor rifted margins, mantle rocks are commonly exhumed and altered to serpentinite due to the ingress of ocean water. This mantle exhumation phase is followed by an increase in magmatism as new oceanic crust begins to form. However, the degree to which serpentinisation is focused at faults and whether the onset of magmatism is abrupt or gradual are both unclear. These processes are difficult to untangle with seismic data alone because the P wave velocities of mafic crustal rocks and partially serpentinised mantle rocks can be similar. However, serpentinised mantle rocks are generally more conductive, often by about an order of magnitude, than mafic crustal rocks, so controlled source electromagnetic (CSEM) and magnetotelluric (MT) techniques provide a promising route to resolve controversies around the structure of lithosphere formed during the onset of seafloor spreading.

To take advantage of the complementary information provided by seismic and electromagnetic data, in September 2023 we acquired a coincident and densely sampled wide-angle seismic, CSEM and MT datasets across the continent-ocean transition at Goban Spur, southwest of the UK. Our c. 200-km profile is coincident with a pre-existing high-quality seismic reflection profile. It extends from thinned continental crust, whose nature is confirmed by drilling, across a broad zone that is inferred on the basis of a previous wide-angle seismic experiment to be composed of exhumed and serpentinised mantle, and into oceanic crust, evidenced by the presence of the prominent seafloor-spreading magnetic anomaly A34. Along this profile, we deployed 49 seafloor instruments at c. 4-km spacing that were each capable of recording seismic, electric field and magnetometer data, plus an additional two instruments recording the inline electric field on 200-m dipoles. These instruments were on the seafloor for about two weeks. During this time we acquired two wide-angle seismic profiles: one using a 5200 cu. in. airgun array shot at 90-s intervals and a second using a 3900 cu. in. airgun array shot at 30-s intervals. We also acquired a frequency-domain  CSEM profile using a transmitter towed c. 100 m above the seabed that powered a 300-m electric dipole with a c. 100-A current at a fundamental frequency of 0.25 Hz. Preliminary data analysis showed that seismic signals were recorded to c. 90 km offset and CSEM signals to c. 8 km offset, while high-quality MT data were recorded at periods of 20-10000 s.

Thus we expect to recover coincident high-resolution images of the seismic velocity and resistivity structure of the upper few km of the basement, sufficient to image patterns of serpentinisation and mafic intrusion. We also expect to recover lower-resolution images of the resistivity to tens of km below the seabed and thus to distinguish continental mantle lithosphere from depleted oceanic lithosphere. We will present examples of the data acquired and the results of some preliminary analysis.    

How to cite: Minshull, T., Bayrakci, G., and Constable, S.: An integrated seismic, controlled source electromagnetic and magnetotelluric study of the continent-ocean transition southwest of the UK, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6227, https://doi.org/10.5194/egusphere-egu24-6227, 2024.

EGU24-6331 | ECS | Orals | TS2.1

How developing grabens dictate volcanism shifts in rifts 

Gaetano Ferrante, Eleonora Rivalta, and Francesco Maccaferri

Volcanism in continental rifts is generally observed to shift over time from the inside of the graben to its flanks and back. These patterns are commonly observed across rifts from different tectonic contexts, different abundance of melt, and regardless of the rifts' specific complexities, suggesting a common control. However, despite recent advances, the mechanisms governing the spatio-temporal evolution of rift magmatism are still poorly understood. Here we test the hypothesis that the spatio-temporal evolution of rift volcanism is controlled by the crustal stresses produced during the development of the rift basin. To do so, we couple a gravitational unloading model of crustal stresses with a boundary element dike propagation code to investigate the effect of a deepening graben on the evolution of magma trajectories in rifts. We find that the progressive deepening of a graben rotates the direction of the principal stresses in the crust, deflecting ascending dikes. This causes a relatively sudden shift of volcanism from the inside of the graben to its flanks during the early stages of rifting. The intensification of this stress pattern, caused by further deepening of the basin, promotes the formation of lower crustal sill-like intrusions. These horizontal bodies can stack under the rift, shallowing the depth at which dikes nucleate, eventually causing a late stage of in-rift axial volcanism, which can alternatively be induced by compensation of graben unloading by sediment infill. Our model reproduces the general patterns of volcanism in rifts and provides a framework to explain their commonalities and account for possible differences. Given the agreement between our model results and observations, we conclude that the evolution of the stresses generated by a developing rift basin can account alone for the major aspects of the spatio-temporal evolution of rift magmatism.

How to cite: Ferrante, G., Rivalta, E., and Maccaferri, F.: How developing grabens dictate volcanism shifts in rifts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6331, https://doi.org/10.5194/egusphere-egu24-6331, 2024.

EGU24-6401 | ECS | Posters on site | TS2.1

Reactivation of inherited faults in rift basins: insight from analogue modeling 

Pauline Gayrin, Daniele Maestrelli, Giacomo Corti, Sascha Brune, and Chiara Del Ventisette

Continental rifts accommodate shallow extensional stresses both by brittle deformation (normal faulting) and volcanism (i.e. dykes and lava flows). Lava flows, together with clastic sedimentation reshape the topography of the rift floor, forming fresh new layers of rock that cover ancient faults. Therefore, the influence of the inherited buried faults on the development of the new faults and the processes of linkage at depth between them remain difficult to investigate. Here we use analogue brittle-ductile modeling with orthogonal extension to elucidate fault growth and reactivation modes, and then compare the results with data from natural rift systems.

In our models, deformation is produced above an elastic band placed between a fixed and a moving wall controlled by a stepper motor. A  layer of viscous material distributes the deformation within the model. On top of the viscous material we use a  layer of sand mixture to simulate the brittle properties of the upper crust. A first phase of extension develops an entire normal fault network, which is then carefully buried under a variable thickness of sand, simulating a cover of sedimentary or volcanic deposits. A second phase of extension allows us to study the mode of reactivation of the inherited faults.The progress of the deformation is tracked using top view images and digital elevation models interpolated from perspective images. At the very end of the model, cross sections cut at regular intervals show the faults at depth by overlaying coloured brittle layers. The high quality of the images allow us to map and analyze the network semi-automatically. We derive displacement/length profiles to characterize the style of fault growth and propagation mode.

Model results show the development of normal faults creating systems of fault-bounded basins, horst-graben structures and conjugated faults. The setup creates a gradient of deformation from the moving wall, where the faults nucleate first near the fixed wall. We thus observe the coexistence of faults of slightly different ages on the same model, as would occur in nature over time. The cross-section shows an upward propagation and the propagation of faults from depth to surface. The preliminary results indicate different styles of reactivation depending on the stage of fault development: reactivation according to a propagating fault mode where faults still have space at tips to develop and a constant-length fault mode where the network is already fully developed. In addition, we find that the surface overlying the inherited structures first bends, then fractures (without observable vertical displacement), and finally develops from the fracture into a proper fault before it finally propagates to connect laterally within the network. This latter growth mode is consistent with the process observed in Iceland by Braham et al. (2021). Understanding the processes of fault network inheritance holds broader applications to many areas where lava or sediments cover faults, layer after layer, such as magma rich rifts like the Eastern Africa Rift or Iceland.

How to cite: Gayrin, P., Maestrelli, D., Corti, G., Brune, S., and Del Ventisette, C.: Reactivation of inherited faults in rift basins: insight from analogue modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6401, https://doi.org/10.5194/egusphere-egu24-6401, 2024.

EGU24-6489 | Orals | TS2.1

Continental back-arc extension, molten lower crust and syn-kinematic granites: insights from Cycladic MCCs 

Laurent Jolivet, Laurent Arbaret, and Romain Augier

Rifting in back-arc basins is characterized by large extension rates, low-angle normal faults and metamorphic core complexes (MCC) displaying partially molten cores and granitic intrusions. The Aegean metamorphic core complexes (MCC) were exhumed underneath crustal-scale detachments accommodating large displacements of the order of 50-100 km and were intruded by Miocene syn-kinematic granites. A common finite geometry and kinematics of all these detachment/pluton systems is recognized with asymmetric intrusive bodies extracted from anatectic lower crust, whose internal structure is controlled by the large-scale dynamics, from the magmatic stage to mylonitization and final exhumation in brittle conditions. Detachments are organized in sets of structures working sequentially evolving from ductile to brittle, the successive branches of the detachment being progressively inactivated by emplacing plutonic batches. The Mykonos-Delos-Rheneia (MDR) MCC shows these interactions between lower crustal migmatites and different syn-kinematic plutons. Our new detailed map of Delos (1/5000) shows geometrical and kinematic relationships between the different magmatic venues during deformation. A strong internal orientation of granites is observed from the magmatic stage until the last ultramylonites below the upper detachments. The deepest magmatic batches are rich in high-grade rocks septae and mafic enclaves, also oriented parallel to regional stretching. Evidence for magma mixing and mingling further indicates interactions with mafic venues at the base of the crust from the mantle. Large high-grade rocks septae are intensely molten and the contact zone between host gneiss and plutons shows intense migmatitization with a foliation parallel to the granite magmatic foliation. Characteristic banded facies marking the contacts between the different intrusions result from high-temperature shearing at the magmatic stage. At all scales foliation and lineation in magmatic rocks and surrounding gneisses are parallel, suggesting a similar weak rheology. Delos shows the roots of these intrusions emplaced as a large-scale sheath-fold whose axis is parallel to the regional stretching direction. The quality of outcrops in Delos, Rheneia and Mykonos, as well as the links between magma emplacement and regional tectonics makes the MDR MCC a natural laboratory for studying the interactions between magmatic intrusions and crustal deformation in tectonically active and hot contexts. In such contexts magmatic and tectonic processes in the lower and middle crusts appear closely interconnected, working at a similar pace and interacting with mantle deformation and melting.

How to cite: Jolivet, L., Arbaret, L., and Augier, R.: Continental back-arc extension, molten lower crust and syn-kinematic granites: insights from Cycladic MCCs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6489, https://doi.org/10.5194/egusphere-egu24-6489, 2024.

EGU24-6912 | ECS | Orals | TS2.1

Upper mantle anisotropy under the strike-slip Dead Sea rift 

Huikai Xu, Youqiang Yu, and Jiaji Xi

Continental rifting is one of the fundamental tectonics of the Earth evolution while our current knowledge on the dynamic mechanism of the strike-slip ones are seriously limited. Here, a systematically shear-wave splitting investigation has been performed in the typical strike-slip Dead Sea rift to illuminate the upper mantle azimuthal anisotropic status across a transform boundary. Totally, 1855 well-defined anisotropic measurements are observed from 102 stations with dominantly N-S fast orientation, which is parallel to the rift strike but deviate from the absolute plate motion direction, mainly result from the plate-driven mantle flow deflected by the thick lithosphere of the eastern Arabian plate. Additionally, the significant fluctuation patterns of splitting times are identified on both the rift-parallel and rift-orthogonal profiles, among which the relatively large splitting times are generally concentrated at the rift zone and attributed to additional coupling lithospheric deformation from the shearing-oriented melt pockets. The consistent rift-parallel fast orientations, combined with the other geoscientific evidences, rule out the role of mantle plume or edge-driven convection in the rift development and further infer the Dead Sea rift to evolve in a passive mode.

How to cite: Xu, H., Yu, Y., and Xi, J.: Upper mantle anisotropy under the strike-slip Dead Sea rift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6912, https://doi.org/10.5194/egusphere-egu24-6912, 2024.

EGU24-7884 | ECS | Posters on site | TS2.1

A tale of two terrane boundaries – variable impact of terrane boundaries on rift geometry in the Great South Basin, New Zealand 

Malte Froemchen, Ken McCaffrey, Tom Phillips, Mark Allen, and Jeroen van Hunen

The evolution of continental rifts is influenced by the pre-rift rheology of the lithosphere and discrete lithospheric structures that segment the rift. The Great South Basin, offshore New Zealand, is a Cretaceous rift system that formed across heterogenous basement terranes which influence the rift architecture. Faults locally rotate or splay and segment along these terrane boundaries. While the impact of terrane boundaries on rift architecture is well understood, the temporal evolution of these rotated faults is poorly constrained. Here we use 3D reflection seismic data to investigate the timing and slip rate evolution of the rotated and segmented faults along two terrane boundaries. Our results show that these have a significant but variable impact on rift evolution and architecture: Faults in the Murihiku terrane show asymmetric throw-length profiles and are rotated along the terrane boundary to the Dun Mountain-Maitai terrane, as they detach into shallow crustal fabrics. Faults in the DMM terrane show less evidence of rotation and more symmetric throw-length profiles but are segmented along the DMM and Caples terrane boundary. The curving faults of the Murihiku terrane likely formed early on but remained as isolated segments only linking up during later stages of rifting when other faults became inactive. These results show the influence of the terrane boundaries was not only active early during initial segmentation but also during the linkage of curved fault segments in the later stages of rifting. These results may help understand the temporal evolution of lithospheric and crustal inheritance on rift evolution in other regions around the world like East Africa or North China.  

How to cite: Froemchen, M., McCaffrey, K., Phillips, T., Allen, M., and van Hunen, J.: A tale of two terrane boundaries – variable impact of terrane boundaries on rift geometry in the Great South Basin, New Zealand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7884, https://doi.org/10.5194/egusphere-egu24-7884, 2024.

Lithospheric extension leads to rift formation and may continue to the point of breakup, with oceanic ridge initiation and the formation of two conjugate rifted margins. In some settings, extension can cease, and the rift may be abandoned. These so-called failed rifts archive snapshots of early phases of deformation, with geometries that may help better constrain the parameters that can prevent a rift from reaching breakup, such as lithospheric rheology, thermal state, rift opening direction and rate, inheritance.

This contribution summarizes a study of the Norwegian Continental Shelf which includes the North Sea Rift and the Møre and Vøring rifted margins. We proceeded to the interpretation of a new dataset of deep penetrating seismic reflection profiles and worked at the regional scale, deliberately ignoring local particularities, to focus on the large-scale structural picture. The aim is to list architectural similarities and differences between the failed rift and the successful rifted margins.

The mapping shows that the North Sea structural geometries and basement seismic facies are very similar to the observations listed for the adjacent Møre and Vøring rifted margins. Various types of tectonic structures are observed, from thick anastomosing shear zones possibly evolving into core-complex geometries, to composite large-scale detachment faults and standard high-angle normal faults. These are categorized into five classes and interpreted as exemplifying the rift tectonic evolution through distinct generations of deformation structures that can activate, de-activate and re-activate. Based on these observations, rift failure dynamics are discussed, and it is proposed that the North Sea rift abandonment may not be related to pre-rift local conditions but rather to the ability to initiate specific tectonic structures such as distal breakaway complexes.

How to cite: Peron-Pinvidic, G.: Structural observations of the northern North Sea: insights into rift failure dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7915, https://doi.org/10.5194/egusphere-egu24-7915, 2024.

EGU24-8883 | Posters on site | TS2.1

Structural inheritance and the evolution of an incipient rift: interaction between the Eger Graben and the Elbe Zone, Central Europe 

David Ulicny, Vladimír Cajz, Karel Mach, Lenka Špičáková, Matěj Machek, Stanislav Čech, Radomír Grygar, Jan Mrlina, and Filip Havlíček

The present-day surface morphology and fabric of the lithosphere of west-central Europe in the foreland of the Alpine orogen have been significantly affected by formation of a system of rifts and associated volcanic domains during the Oligocene and Neogene, known as the European Cenozoic Rift System (ECRIS). In order to better understand the geodynamic causes of formation of ECRIS and its volcanism, it is important to improve the knowledge of chronology of tectonic events in the entire ECRIS, and to test the validity of existing palaeostress interpretations. The Oligo-Miocene Eger Rift, so far the least-studied part of ECRIS, has the potential to bring new clues to some persisting controversies.

The axis of the Eger Rift roughly follows the trend of a major Variscan lithosphere-scale boundary, the Teplá-Barrandian/ Saxothuringian suture (TSS) formed during the collisional phases about 380-320 Ma. Following the Variscan collision, the lithosphere of the Bohemian Massif was affected by formation of a Late Paleozoic extensional basin system which in the western part of the Bohemian Massif largely follows the NE strike of the TSS. Another major structure in the basement underlying the Eger Rift is the WNW-striking Elbe Zone, with main periods of activity during the Paleozoic and Mesozoic through early Cenozoic.

We present a synthesis of presently available structural and stratigraphic data and a resulting first-order interpretation of tectonic evolution of central and eastern Eger Rift. The main data sources were borehole, outcrop, seismic reflection data, targeted field mapping, digital elevation models, and gravity data from both public and industry sources. Several stratigraphic levels (within the Neogene, Cretaceous, and top of Late Palaeozoic) were used as structural datums.

Analysis of fault populations in central and eastern Eger Rift shows that overall, the Late Paleozoic fracturation of the upper crust of the Bohemian Massif was key for localization of the main fault systems of the Eger Rift. This includes dextral shearing within the Elbe Zone that affected the basement structural grain responsible for segmentation of the Eger Rift during the Cenozoic. Changes between oblique and orthogonal extension modes are interpreted from the geometries and temporal relationships of key structures - both in time, likely due to a changing regional paleostress field, and in space, due to different orientations of basement structures between the rift segments.

This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S.

How to cite: Ulicny, D., Cajz, V., Mach, K., Špičáková, L., Machek, M., Čech, S., Grygar, R., Mrlina, J., and Havlíček, F.: Structural inheritance and the evolution of an incipient rift: interaction between the Eger Graben and the Elbe Zone, Central Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8883, https://doi.org/10.5194/egusphere-egu24-8883, 2024.

Ocean closure and collisional orogeny frequently enrich the lithospheric mantle in incompatible chemical elements. The most intensive enrichment usually occurs during the subduction of continent-derived sediments and continental crust. Radioactive isotopes of uranium and thorium are part of the HFSE (high-field-strength elements) group of incompatible elements and, therefore, can be also characterized by increased concentration within the post-orogenic lithospheric mantle in comparison to the common lithospheric mantle. The anomalously high content of uranium and thorium within the post-orogenic mantle lithosphere is reflected by the composition of potassic and ultrapotassic magmas, which are sometimes extremely enriched in these radioactive elements. This enrichment is well documented by numerous studies and, therefore, cannot be ignored during the numerical modelling of rifting processes.

According to pure conductive thermal modelling, the anomalously increased content of radioactive elements within the post-orogenic lithospheric mantle causes a time-dependent rise in temperature, providing favourable conditions for intracontinental rifting more than 20-100 million years after the closure of the ocean. A time gap between the orogeny and highly increased temperature within the lithosphere is controlled by two major factors: (1) the amount of thorium and uranium and (2) the size of the anomalous lithospheric mantle. According to numerical thermo-mechanic modelling, the post-orogenic increase in temperature not only weakens the lithosphere but also causes thermal expansion of the lithosphere which can be sufficient to initiate the first stage of intracontinental rifting without involving regional extensional forces.

Therefore, we propose a new concept of intracontinental rift initiation as a result of time-dependent temperature increase and thermal expansion of the post-orogenic mantle lithosphere due to the decay of radioactive elements. The described rather simple mechanism of rift formation provides a significant advance in our understanding of both local rift processes and global tectonic cycles on our planet.

How to cite: Maystrenko, Y. and Slagstad, T.: Post-orogenic radiogenic initiation of intracontinental rifting within the lithospheric mantle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9325, https://doi.org/10.5194/egusphere-egu24-9325, 2024.

EGU24-9513 | Posters on site | TS2.1

Early relief growth at the edge of an incipient rift – the Eger Graben, Bohemia 

Michal Rajchl, Karel Mach, Filip Havlíček, David Uličný, and Matěj Machek

The present-day geological and morphological expression of the Cenozoic Eger Rift in central Europe is dominated by the faulted edge of the Krušné Hory (Erzgebirge) Mts., a plateau uplifted to c. 1 km above sea level following the mid-Miocene, resulting in partial deformation and erosion of parts of the Eger Rift sedimentary and volcanic infill. The main phase of the uplift is considered to have occurred in Plio-Quaternary times, but details of this process and its relation to the Eger Rift itself remain unclear.

The Oligo – Miocene Most Basin is the most extensive sedimentary basin preserved within the Eger Rift. The basin, bounded at the NW by the Krušné Hory uplift, is characterized by an economically important coal seam, up to 35 m thick. Previous research has shown that during the formation of the basinwide swamps in early Miocene the basin was hydrologically open, with at least one but probably more outlets draining its area toward the North and Northwest, across today’s Krušné Hory (Erzgebirge) Fault Zone (KHFZ). During the earliest Miocene times, most of the region of today’s Krušné Hory / Erzgebirge uplifted block was thus a generally low-relief area. Paleogeographic changes in the Most Basin suggest an increasing activity of its marginal faults, some of which were predecessors of the present-day KHFZ, still during the early to mid-Miocene. For understanding the formation of this major fault zone it is important to answer the question of the timing, magnitude and character of initial relief growth along the nw. edge of the Eger Rift.

The stratigraphic and structural record exposed recently at the KHFZ provides evidence of a small-scale relay ramp that formed between two overlapping normal faults of E-W general strike and breached later by a normal fault of NE strike. Debris-flows conglomerates were found interbedded with carbonaceous mudstones and lignite layers belonging to the early Miocene main coal seam, in the close vicinity of the lower bounding fault containing boulders from a tectonic breccia of the fault damage zone. This fact indicates the existence of a prominent fault scarp developed along the fault plane of the above fault and considered the source of coarse-grained clastics during the initial, coal-bearing, phase of the basin formation. The subsequent acceleration of the Most Basin subsidence that resulted in basin-wide expansion of the swamp environment, can be explained by linkage of the border faults accompanied by breaching and drowning of some relay ramps.

The studied sedimentary record provides evidence of faulted relief with an elevation of tens of metres that contributed to the supply of clastic material to the incipient rift during early Miocene time. The subsequent breakage and drowning of the relay ramp provide evidence for syn-sedimentary activity some of NE-SW segments of the KHFZ previously thought to be a manifestation of later, post-rift deformation.

This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S. We acknowledge support by the Severní energetická, a.s., and Ing. Petr Šulcek in conducting research in the Důl ČSA Mine.

How to cite: Rajchl, M., Mach, K., Havlíček, F., Uličný, D., and Machek, M.: Early relief growth at the edge of an incipient rift – the Eger Graben, Bohemia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9513, https://doi.org/10.5194/egusphere-egu24-9513, 2024.

EGU24-9770 | Posters on site | TS2.1

Modelling the effects of changing extension directions in a segmented rift: application to the Eger Rift, Central Europe 

Filip Havlíček, David Uličný, Ondřej Krýza, Matěj Machek, Michael Warsitzka, and Prokop Závada

Continental lithosphere undergoing the process of rifting has typically previously experienced a complex deformation history resulting in a highly heterogeneous mechanical structure. This structural inheritance can affect the developing continental rift across all scales, from rift localization and segmentation to individual fault geometries. Assessing the impact of such inherited structures on extensional basin geometries can be difficult, especially in the case of fossil rifts where uncertainties may arise about the orientation of regional stresses during extension. One such example is the Eger Rift which developed during the Oligocene to early Miocene as the easternmost branch of the European Cenozoic Rift System (ECRIS). Earlier interpretation proposed a two-phase extensional history for the rift.

We use a series of crustal-scale, brittle-viscous analogue models, based on the geometry of the central and eastern parts of the Eger Rift, to explore the development of a segmented rift in a multiphase setting with evolving extension direction. Our model crust rests on a basal velocity discontinuity (VD), a discrete boundary of a mobile base plate simulating a reactivated basement weakness localizing our model rift. The geometry of this weakness is a simplified representation of the geometry of older, mainly Upper Paleozoic basins, which are hypothesized to have greatly influenced the localization and geometry of principal fault systems and rift segments that they define. The VD thus consists of 3 segments oriented at various angles with respect to extension direction. The Model surface is imaged by stereoscopic cameras and analyzed by Particle Image Velocimetry (PIV) techniques to track surface deformation and topography evolution during the run.

Our results confirm that in a setting with an abrupt change in extension direction, the first extensional phase plays a key role in defining the final observed fault pattern with new second-phase faults generally being few in number and of limited length. This effect is enhanced above a segmented VD. If a larger portion of the VD is optimally oriented with respect to the first-phase extension, the final fault pattern is dominated by first-phase structures with the growth of second-phase faults being nearly inhibited. In a contrasting scenario, where most of the VD is initially oblique to extension direction, second-phase faults are more abundant, leading to a bimodal final fault pattern. By comparing our results with newly mapped fault populations in the Eger Rift we conclude that the proposed two-phase history for the rift is plausible with a major role of the initial phase of approximately N-S extension.

This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S.

How to cite: Havlíček, F., Uličný, D., Krýza, O., Machek, M., Warsitzka, M., and Závada, P.: Modelling the effects of changing extension directions in a segmented rift: application to the Eger Rift, Central Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9770, https://doi.org/10.5194/egusphere-egu24-9770, 2024.

EGU24-9947 | ECS | Orals | TS2.1

New results on the crustal configuration of the Newfoundland margin: Implications for rifting 

Laura Gómez de la Peña, César R. Ranero, Manel Prada, Donna Shillington, and Valentí Sallarès

Driven by discovery of contrasting structures of Continent to Ocean Transition (COT) discovered at rifted continental margins during the 90’s, several high-quality seismic datasets were acquired in these margins during the early 2000 to unravel the structure of unexplored regions. Despite the fact that some of these datasets are basically comparable to modern data in quality, the processing, imaging and modelling methodologies at the time of acquisition can be now refined and improved. Recent developments in parallel computing and novel geophysical approaches provide now the means to obtain a new look at the structure with enhanced resolution seismic models and a mathematically-robust analysis of the data uncertainty, that was formerly difficult, if not unfeasible, to achieve. 

We focused on the Newfoundland margin and applied up-to-date methodologies to the high-quality SCREECH dataset (2000). These data include three primary transects with coincident multichannel seismic (MCS) reflection data acquired with a 6-km streamer and wide-angle data recorded by short-period OBS and OBH spaced at ~15 km. We reprocessed the streamer data and also performed the join inversion of streamer and wide-angle OBS/OBH seismic data, using reflections and refraction arrivals, which significantly improved the resolution of the velocity model. We performed a statistical uncertainty analysis of the resulting model, supporting the reliability of the observed features. In particular the new velocity model provides a detailed definition of the top of the basement where the largest abrupt velocity change occurs. The comparatively high-resolution velocity model obtained from the joint tomography allowed to properly perform a Pre-Stack Depth Migration of the MCS. The improved velocity model and seismic images permit to characterize the different crustal domains of the margin with less uncertainty that previous attempts, and relate them to the tectonic structure.

The different domains reveal previously undetected crustal characteristics that change over short distances. The reprocessing of the MCS data allowed to a better understanding of the crustal structure, as the Moho is imaged for the first time under the slope domain.

Comparison of these new results on the Newfoundland margin with the most modern data on the West Iberian margin, acquired during FRAME (2018) and ATLANTIS (2022) cruises provides a new view of the evolution of the North Atlantic opening.

How to cite: Gómez de la Peña, L., R. Ranero, C., Prada, M., Shillington, D., and Sallarès, V.: New results on the crustal configuration of the Newfoundland margin: Implications for rifting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9947, https://doi.org/10.5194/egusphere-egu24-9947, 2024.

EGU24-11403 | Posters on site | TS2.1

The story of double spreading centers formed during continental rifting in 2D 

Laetitia Le Pourhiet and Fan Zhou

It is common wisdom, based on many years of published simulations of continental rifting followed by spreading that in 2D when a mid-oceanic ridge form in a numerical simulation of continental rifting, extension stops and spreading take over the extension. This is generally due to the complete loss of strength of the mantle lithosphere that cannot transmit forces horizontally across the spreading zone anymore. Actually, in general even the onset of mantle lithosphere necking in a simulation can cause the end of the extension and for many years, I actually claimed very load in the past that two active necking system must be the signature of some obliquity causing 3D extensional conditions. However, recently, a whole series of 2D simulations produced systematically two spreading centers active at the same time. These results surprised me a lot. These simulations were very complex, including a lot of inheritance, the first easy conclusion could have been to say that inheritance causes multiple spreading… But we spent some time and effort to understand if this behavior was due to inheritance or something else. Simplifying our model set-up to the strict minimum, we found it was not inheritance, but a quite cold mantle temperature which permitted a larger shear coupling between the upper mantle dynamics and the mantle lithosphere.  A 50°C difference in mantle temperature radically change the results of the simulation and thanks to our failure, we have found the embryo of an alternative explanation to 3D interactions for the occurrence multiple active necking zones.

How to cite: Le Pourhiet, L. and Zhou, F.: The story of double spreading centers formed during continental rifting in 2D, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11403, https://doi.org/10.5194/egusphere-egu24-11403, 2024.

EGU24-11494 | ECS | Posters on site | TS2.1

The seismic structure of the NW Moroccan margin, Gulf of Cadiz, from new high-quality multichannel seismic reflection data 

Silvia Foiada, Marta Neres, Pedro Brito, Laura Gomez de la Peña, Irene Merino, and César Ranero

The FRAME geophysical cruise, conducted in 2018 onboard the Spanish R/V Sarmiento de Gamboa, acquired new multichannel seismic reflection (MCS) data on the SW Iberia and NW Moroccan margins. MCS data were acquired with a 6 km long solid-state digital streamer Sercel SENTINEL towed at 19 m water depth, and a 3920 c.i. source with two sub-arrays with 20 guns towed at 10 m depth. The system was designed to provide high penetration and map the entire crust and the upper mantle structure and retain enough resolution to image well the stratigraphy.

In this work we present a 220 km long seismic line acquired on the NW Moroccan margin, from the shallow continental shelf across the continental slope and extending across the deep abyssal plain of the Gulf of Cadiz. The NW Africa margin was selected because the region was the focus of several geophysical campaigns, and several DSDP drill sites that drilled into the synrift strata.  However, limited modern data has imaged the crustal-scale tectonic structure to unravel the late Triassic - early Jurassic rift history of the region.

We applied a seismic processing flow tailored to the attenuation of the multiple energy, signal designature and for the creation of a detailed macro-velocity model to image the lateral changes of the synrift tectonic structure and stratigraphy. The high-quality image of the structure of this rifted margin reveals a complex tectonic structure from the shelf to the deep-water basin where a deep basement containing salt bodies across the entire profile extension. These new results are of high importance for the understanding of the rifting and continent-ocean transition (COT) processes on the northern Central Atlantic and Neothetys domains, as well as for the subsequent compressive deformation processes in the Gulf of Cadiz related to the Africa-Eurasia plate collision.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds through the project LISA (https://doi.org/10.54499/PTDC/CTA-GEF/1666/2020).

How to cite: Foiada, S., Neres, M., Brito, P., Gomez de la Peña, L., Merino, I., and Ranero, C.: The seismic structure of the NW Moroccan margin, Gulf of Cadiz, from new high-quality multichannel seismic reflection data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11494, https://doi.org/10.5194/egusphere-egu24-11494, 2024.

EGU24-11825 | ECS | Posters on site | TS2.1

Tectonostratigraphic evolution of the Tainan Margin (NE South China Sea): comparison with the Pearl River Mouth Basin 

Mateus Rodrigues de Vargas, Geoffroy Mohn, Julie Tugend, Nick Kusznir, and Andrew Lin

The wide rifting mode that preceded the opening of the South China Sea (SCS) in the Cenozoic generated a set of Paleogene rift basins presently buried under thick post-rift sedimentary infill. Much of the tectonostratigraphic evolution of the South China Sea is now relatively well-constrained (e.g., Pearl River Mouth Basin). However, the SCS's northeasternmost part (i.e., the Tainan margin sensu lato), which might represent the oldest passive margin segment, remains to be integrated into the framework of the rifting and opening of the SCS.

This work aims to review and revisit the tectonostratigraphic evolution of the Tainan margin. To do so, an integrative approach has been used combining the analysis of seismic reflection and gravity data. We use 3D gravity inversion to determine the distribution of Moho depth and crustal thickness within this margin segment. The gravity inversion scheme incorporates a lithosphere thermal gravity anomaly correction, which is critically important because of the elevated geothermal gradient within the young oceanic lithosphere of the South China Sea and its continental margins. In the Tainan margin, results show contrasted crustal domains from the continental shelf, to the distal margin and oceanic domain.

Only limited crustal thinning is observed over the continental shelf where a succession of rift basins is documented (i.e., Taihsi, Nanjihtao, and Penghu basins) that are part of the Northern Rift System. In contrast, the distal Tainan margin shows greater crustal thinning to less than 10 km thick under an aborted breakup basin, thereby forming the Southern Rift System. To the south, this basin is separated from the unambiguous oceanic domain (6 to 8 km thick) by a comparatively thicker crustal block (~ 10 to 15 km thick). This crustal block forms the Southern High where numerous volcanic edifices and magmatic intrusions are observed or inferred.

Half-grabens of the Northern Rift System are controlled by counter-regional faults and filled by Paleocene to Eocene syn-rift sediments. For the distal domain, no well calibration is available. There, we identified several seismic units bounded by regional unconformities. Our results show relatively thin syn-rift sediments locally controlled by a low-angle normal fault system in the Southern Rift System. In contrast, thick post-rift sequences are observed except over the Southern High.

Based on our results, we propose a review of structural style and age correlations from the continental shelf to the distal domains of the Tainan margin. To illustrate along-strike variations of the crustal structure and stratigraphic style, we build an array of regional geological cross-sections that are further compared with existing observations in the adjacent Pearl River Mouth Basin.

How to cite: Rodrigues de Vargas, M., Mohn, G., Tugend, J., Kusznir, N., and Lin, A.: Tectonostratigraphic evolution of the Tainan Margin (NE South China Sea): comparison with the Pearl River Mouth Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11825, https://doi.org/10.5194/egusphere-egu24-11825, 2024.

EGU24-11854 | Posters on site | TS2.1

Rifting style and continental breakup of Marginal Seas 

Geoffroy Mohn, Jean-Claude Ringenbach, Etienne Legeay, Julie Tugend, William Vetel, and François Sapin

Marginal Seas are extensional basins formed in a convergent setting near active subduction zones. They are characterized by a short life (<25 Ma), as well as unstable and changing directions of seafloor spreading. However, the processes related to their formation from rifting to seafloor spreading initiation remain debated (supra-subduction convection/extension, slab-pull). This problem is further compounded by the fact that our understanding of continental breakup used to be derived from the evolution of magma-poor and magma-rich Continent-Ocean Transitions (COT) of Atlantic margins.

Here, we describe and discuss the rifting style and the mode of continental breakup of three main Marginal Seas located in the Western Pacific, namely the South China Sea, the Coral Sea and the Woodlark Basin. All three examples formed under rapid extension rates and propagation of seafloor spreading.

In these three examples, continental extension is accommodated by a succession of hyper-extended basins controlled by low-angle normal faults that may form and be active at 30° (or less). These hyper-extended basins are filled by polyphase syn-rift sequences showing atypical geometries. These complex stratigraphic architectures result from the development of the low-angle normal faults interacting with antithetic faults, controlling the formation of extensional fishtails for example. The formation of such low-angle normal fault systems is enhanced by basement inheritance of the previous orogenic system.

Continental breakup and final extension are contemporaneous with an important magmatic activity emplaced in the distalmost part of these margins including volcanoes, dykes and sills. Continent-Ocean transitions (COTs) are characterized by a sharp juxtaposition of the continental crust against igneous oceanic crust suggesting that a rapid shift from rifting to spreading occurred. High extension rate prevents conductive cooling allowing the focusing of volcanic activity in sharp COTs, quickly evolving to magmatic accretion.

In conclusion, the rifting style and mode continental breakup are most likely associated with initial rheological conditions with hot geotherm combined with fast extensions rates likely directed by kinematic boundary conditions directly or indirectly controlled by nearby subduction zones.

How to cite: Mohn, G., Ringenbach, J.-C., Legeay, E., Tugend, J., Vetel, W., and Sapin, F.: Rifting style and continental breakup of Marginal Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11854, https://doi.org/10.5194/egusphere-egu24-11854, 2024.

EGU24-11873 | Posters on site | TS2.1

Palaeobathymetry of the Mid-Norwegian volcanic margin during continental breakup and paleoclimate implications 

Julie Tugend, Geoffroy Mohn, Nick Kusznir, Sverre Planke, Christian Berndt, Ben Manton, Dmitrii Zastrozhnov, and John, M. Millet

The Mid-Norwegian volcanic rifted margin and its NE-Greenland conjugate formed in relation to continental breakup in the latest Palaeocene to earliest Eocene during the emplacement of the North Atlantic Igneous Province (NAIP). The development of the NAIP and opening of the North Atlantic occurred contemporaneous to the Paleocene Eocene Thermal Maximum (PETM) which corresponded to a rapid 5-6 °C global warming episode.

The cause of this rapid global warming, explored as part of IODP Expedition 396, is thought to relate to the thermogenic gases released to the atmosphere via thousands of hydrothermal vents. The thermogenic gases were produced by contact metamorphism of carbon-rich sediments during widespread sill emplacement from the NAIP. The potential of hydrothermally-released greenhouse gases to influence climate depends strongly on the water depth at which they get released. Unless it is released in a shallow marine environment most methane will be oxidized before it reaches the atmosphere.

Early results from IODP Expedition 396 have documented that at least one of the Mid-Norwegian hydrothermal vents was emplaced in shallow marine to potentially sub-aerial conditions. The aim of this contribution is to constrain further the paleo-water depth at which hydrothermal vents formed along the other parts of the mid-Norwegian volcanic rifted margin. This study focuses on an integrated workflow of quantitative geophysical and geodynamic analyses calibrated by new IODP drilling results and structural and stratigraphic observations. We use a 3D flexural-backstripping, decompaction and reverse thermal subsidence modelling to predict the palaeobathymetry and palaeostructure at keys stages of the syn- to post-breakup evolution that can be compared with palaeo-water depths estimated from biostratigraphic data.

Results provide new constraints on the paleobathymetry of hydrothermal vent complexes required to confirm whether the global warming recorded by the PETM was triggered by the magma-rich continental breakup leading to the opening of the northeast Atlantic Ocean. 

How to cite: Tugend, J., Mohn, G., Kusznir, N., Planke, S., Berndt, C., Manton, B., Zastrozhnov, D., and Millet, J. M.: Palaeobathymetry of the Mid-Norwegian volcanic margin during continental breakup and paleoclimate implications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11873, https://doi.org/10.5194/egusphere-egu24-11873, 2024.

EGU24-11877 | Orals | TS2.1

Along-strike magma-poor/magma-rich spreading transitions 

Michal Nemcok and Brian Frost

1D/2D data-based studies of active spreading centres brought the knowledge of extension ratedependent stretching-dominated v. buoyancy-dominated spreading. 3D reflection seismic data from the extinct centre of an initial oceanic corridor in the Caribbean allow us to see an along-strike transition between stretching- and buoyancy-dominated spreading where the spreading through detachment faulting is a precursor to the magma-assisted spreading. Studying progressively more evolved portions of the spreading centre, going from its end towards its centre, we see a progressively higher ascent of the asthenosphere, which heats the developing

core complex in the exhuming footwall of the initial stretching-dominated system. The asthenospheric ascent is associated with thermal weakening of the core complex, which eventually results in ductile deformation reaching the upper portion of the complex. Subsequently, the core complex is penetrated by the dyke located at the top of the asthenospheric body. The dyke, which subsequently evolves to a diapir-shaped body, reaches the sea floor

and establishes a magma-assisted steady-state seafloor spreading. These observations lead to a model explaining the initiation of the magma-assisted spreading in the initial oceanic corridor. Furthermore, they also improve our knowledge of multiple interacting mechanisms involved in the breakup of the last continental lithospheric layer, subsequent disorganized spreading and younger organized spreading.

How to cite: Nemcok, M. and Frost, B.: Along-strike magma-poor/magma-rich spreading transitions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11877, https://doi.org/10.5194/egusphere-egu24-11877, 2024.

EGU24-12130 | ECS | Posters on site | TS2.1

Structure and Dynamics of the Porcupine Magma-Poor Continental Margin from new Ocean Bottom Seismometer Data 

Ibrahim Yusuf, Stephen M Jones, Tim Reston, Thomas Funck, Brian M O'Reilly, and John R Hopper

The Porcupine Basin, situated in the North Atlantic, serves as a unique natural laboratory for investigating the temporal evolution of magma-poor rifts. Notably, the basin exhibits a progressive increase in the total degree of stretching from north to south, offering a valuable opportunity to interpret its structure in terms of the temporal evolution of magma-poor rifted margins. This study, as part of the broader PORO-CLIM project, focuses on Profile 2 to construct a whole-crustal seismic velocity model and integrate it with existing data to unravel the complete rifting history of the Porcupine Basin.

In the northern region, Reston et al. (2004) identified a detachment fault, the P-reflector, indicating substantial rifting  [1]. Recent analyses by Prada et al. (2017) extended this understanding to the central basin, revealing progressive crustal thinning and mantle serpentinization [2]. However, the southern sector remains largely unexplored. This project aims to capitalise on newly acquired Ocean Bottom Seismometer (OBS) data from PORO-CLIM Profile 2 to image the deep crustal structure and complement this with basement mapping of the southern Porcupine Basin using industry 2D seismic data.

Seismic refraction data from 20 OBS along a 226 km transect form the basis for constructing a comprehensive crustal velocity model. Utilising the RAYINV modelling package, a layer-by-layer forward modelling approach is employed to correlate calculated and observed travel times. Concurrently, structural mapping using long-offset 2D seismic reflection data assists in delineating major faults and regions of mantle unroofing, contributing to the understanding of the Porcupine Basin's subsurface. Preliminary findings reveal extreme crustal thinning and asymmetry, highlighting north-to-south crustal thinning and the emergence of the P-reflector in the southern region of the Porcupine Basin.

[1] Reston, T.J., Gaw, V., Pennell, J., Klaeschen, D., Stubenrauch, A. and Walker, I. (2004). Extreme crustal thinning in the south Porcupine Basin and the nature of the Porcupine Median High: implications for the formation of non-volcanic rifted margins. Journal of the Geological Society, [online] 161, pp.783–798.

[2] Prada, M., Watremez, L., Chen, C., O’Reilly, B.M., Minshull, T.A., Reston, T.J., Shannon, P.M., Klaeschen, D., Wagner, G. and Gaw, V. (2017). Crustal strain dependent serpentinisation in the Porcupine Basin, offshore Ireland. Earth and Planetary Science Letters, [online] 474, pp.148–159.

How to cite: Yusuf, I., M Jones, S., Reston, T., Funck, T., M O'Reilly, B., and R Hopper, J.: Structure and Dynamics of the Porcupine Magma-Poor Continental Margin from new Ocean Bottom Seismometer Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12130, https://doi.org/10.5194/egusphere-egu24-12130, 2024.

EGU24-12991 | ECS | Orals | TS2.1

Tectonic structure and evolution of Brazilian Equatorial Margin  

Julia Fonseca, César Ranero, Paola Vannucchi, David Iacopini, and Helenice Vital

The Brazilian Equatorial Margin (BEM) is classically interpreted as a transform margin formed during the last phases of the Atlantic rifting of Gondwana. However, rift kinematics and subsequent continental break up has not been constrained.

We present a new model based on the interpretation of a 2D seismic grid acquired along the BEM. The datasets, provided by the Brazilian National Agency for Petroleum (ANP), expand for ~600 km of the margin and consist of approximately 10.000 km of crustal scale 2D seismic reflection profiles which have been calibrated with industry drillholes. The integration of crustal-scale tectonic structures and age and distribution of synrift sediment deposits allowed to determine the style and the timing of the different tectonic phases and to define the crustal thinning evolution of the entire rift system along the Potiguar and East Ceará Basins (NE Brazil).

Our findings indicate that: 1. rifting started ~140-136 My, 2. extension stopped earlier (late Aptian) in the shallow sector of the basin than in the deep-water (early Albian) domains. The shallow basin domains presents minor crustal thinning (~35 thick crust over ~100 km wide), whereas in the deep-water domains, about ~60 km wide, the crust is 4-8 km thick and it extended into the early Albian (116-110 My).

The distribution of deformation structures supports a model of rift evolution where: deformation is initially distributed while forming a shallow basin; it evolves by focusing the extension; finally, extension migrates toward the basin centre to form the deep-water domain. Constraints from seismic reflection data and drillholes help define an abrupt continent to ocean transition (COT), and breakup occurred during the early Albian. Basin sedimentation from its onset to the late Aptian is terrigenous, indicating an isolated environment disconnected from the Northern and Southern Atlantic oceans. Sedimentation changed during the late-most Aptian to the early Albian when marine facies deposited during a rapid ocean water infill of a previously endorheic basin.

The seismic images document that rifting across the margin is not dominated by transcurrent deformation, with strike-slip faulting limited to a relatively small sector, whereas most of the margin extended through normal faulting deformation during opening.

From the interpretation of the 2D seismic reflection grid it was possible to distinguish abrupt lateral changes in the architecture of the basement. These changes defined three distinct, first order segments along the margin named Southern, Central, and Northern segments. The different evolution of the three segments throughout the rifting process is defined by thickness map of the basement. The Northern segment is the only region that shows evidence of potential late synrift magmatism, likely formed during the COT emplacement, which defines second order segmentation. Our interpretation suggests a spatial correlation between first-order tectonic segmentation and second-order magmatic segmentation during the embryonic formation of the spreading center with the definition of fracture zone/transform faults. These findings suggest that most transform faults formed on the spreading centers may have originated from the pattern of continental segmentation during rifting.

How to cite: Fonseca, J., Ranero, C., Vannucchi, P., Iacopini, D., and Vital, H.: Tectonic structure and evolution of Brazilian Equatorial Margin , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12991, https://doi.org/10.5194/egusphere-egu24-12991, 2024.

EGU24-13269 | ECS | Posters on site | TS2.1

Crustal Structure of Continental Margin and Oceanic Basin at the Southern Mozambique Margin 

Wei Wang, Satish Singh, Zhikai Wang, Aiguo Ruan, Yong Tang, Jérôme Dyment, Sylvie Leroy, Louise Watremez, Zhaocai Wu, He Li, and Chongzhi Dong

During the Jurassic period, the Gondwana Continent progressively rifted from north to south along three huge transform faults (Davie Fracture Zone (DFZ), Mozambique Fracture Zone (MFZ) and Agulhas-Falkland Fracture Zone (AFFZ)), forming the northern, central and southern continental margins along Mozambique, producing a series of divergent and strike-slip margins. These margins are crucial areas for understanding the evolution of Gondwana as their crustal nature and geometry have strongly impacted the kinematic reconstruction of Gondwana. Especially, the debate about continental or oceanic crust for the Mozambique Coastal Plain (MCP) and North Natal Valley (NNV) at the southern Mozambique margin led to tens of kinematic reconstruction models of Gondwana. Based on the OBS and MCS data results of PAMELA MOZ3/5 Cruises, MCP and NNV were identified as continental crust. This has led the scientific community to reconsider the issue, for example, the opening time of the oceanic basin, the movement direction of rifting, and the intense magmatism during the rifting and break-up of Gondwana.

In June 2021, the Second China-Mozambique Joint Cruise was conducted onboard the R/V “Dayang hao”. Three wide-angle seismic OBS profiles were acquired where 70 four-component OBSs were deployed along profiles DZ02 and DZ04 oriented nearly W-E and DZ01 oriented nearly N-S. Four Bolt air guns with a total volume of 8000 in3 in total were towed at ~100 m behind the R/V “Dayang hao” at ~10 m below the sea surface. The shot interval was 200 m.

Here, we present the tomographic results of P-wave velocity along 442 km long profile DZ02, where 21 OBSs were deployed. It traverses through the Continent Ocean Transition (COT) and extends into the Mozambique ocean basin. Approximately 19,000 P-wave arrivals were manually picked, using the travel-time tomography inversion to get the velocity model. The tomographic result shows an apparent decrease in crust thickness from COT to the ocean basin, and the thickness of the oceanic crust is about 8 km. We also observe high-velocity anomalies up to 7.4 km/s in the lower crust above Moho, suggestive of more primitive melt. We will also present the S-wave velocity model for DZ02.  

How to cite: Wang, W., Singh, S., Wang, Z., Ruan, A., Tang, Y., Dyment, J., Leroy, S., Watremez, L., Wu, Z., Li, H., and Dong, C.: Crustal Structure of Continental Margin and Oceanic Basin at the Southern Mozambique Margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13269, https://doi.org/10.5194/egusphere-egu24-13269, 2024.

EGU24-13432 | Orals | TS2.1

Structural Evolution of the Black Sea Basin Using Sectioned Computational Models 

Armagan Kaykun and Russell Pysklywec

The tectonic formation of the Black Sea Basin (BSB) has been an ongoing debate: primarily, there is still not a consensus on whether the basin was rifted as one east-west oriented basin, or as two separate basins named Eastern and Western Black Sea Basins. These interpretations are based largely on deep-sea drilling projects and a growing dataset of seismic information (of variable access for academic use). Supporting the two-basin idea is the semi-parallel ridge and depression geometry of the BSB with NW-SE orientation in the Eastern portion of the Black Sea Basin; and W-E orientation in the Western portion of the Black Sea Basin. On the other hand, interpretations for a single basin are supported by the regional structure of the BSB being aligned with the geodynamic models of the basins rifted as a result of slab roll-back. Complicating the understanding of the basin extension and development is the inferred tectonic inversion to shortening in the region starting in the Late Eocene.

To propose a model to answer ongoing debates, we interpreted 24 long-offset 2D seismic lines acquired by GWL in 2011 in a structural geology context. We focused on the structural elements such as big scale normal faults, reverse faults, and tectonic inversion features to create a basis for our 2D computational models for both east and west portions of the BSB. One important finding was to determine the null points on basin bounding faults where the extensional tectonic movements stopped, and the compressional tectonic movements started. Utilizing the ASPECT geodynamic code, we built 2D computational models parallel to the selected two 2D seismic profiles. We compared our findings in our seismic interpretations with the results to understand the timing and basin-wide distribution of structural highs and the compressional tectonic features that shaped the BSB.

How to cite: Kaykun, A. and Pysklywec, R.: Structural Evolution of the Black Sea Basin Using Sectioned Computational Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13432, https://doi.org/10.5194/egusphere-egu24-13432, 2024.

Many orogenic belts today preserve evidence of past crustal rifting. During the syn-rifting, the crust undergoes thinning, forming rift basins with thick sedimentary deposits. The upwelling of the mantle during this extensional phase increases the geothermal gradient within the basin, affecting the crust and sedimentary rocks.

In this study, we used numerical models to simulate the temperature changes in sedimentary rocks within rift basins during both the active rifting phase and the passive continental margin phase after rifting cessation. We found that under a stretching rate of 0.7 cm per year, after 20 million years of continuous stretching, the geothermal gradient within the basin can reach 50-60°C per kilometer, with sedimentary rocks reaching temperatures as high as 450-500°C. After 20 million years of cooling following the end of stretching, the temperatures of the sedimentary rocks decrease by nearly 100°C, and the geothermal gradient reduces to approximately 30°C per kilometer.

We believe that these phenomena can be correlated with the evolution of the Hsuehshan Range in Taiwan, which experienced a transition from rifting to a passive continental margin. During the rifting phase, the temperatures of the sedimentary rocks within the basin reached high metamorphic temperatures of 450-500°C, as indicated by carbonaceous material Raman spectroscopy (RSCM). As the region entered the passive continental margin phase, the rocks gradually cooled, with a temperature decrease of nearly 100°C prior to the onset of mountain building in Taiwan. Similar high-temperature metamorphic temperatures were obtained through RSCM analysis along the Central Cross-Island Highway and Northern Cross-Island Highway, exceeding the closure temperatures of zircon core tracks. However, some zircon core tracks in certain areas did not yield closure ages, suggesting that the high metamorphic temperatures obtained from RSCM analysis were inherited from previous stretching events rather than occurring during the Penglai orogeny.

How to cite: zheng, M., Lee, Y.-H., and Tan, E.: Numerical modelling of continental margin of the Eurasian Plate Rifting and Tectonic evolution.Causes of the highest metamorphic temperature in the Hsuehshan Range and Backbone Range , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14297, https://doi.org/10.5194/egusphere-egu24-14297, 2024.

EGU24-14808 | Orals | TS2.1

Some evidence of a wide rotational extension in East Antarctica preceding Gondwana breakup 

Egidio Armadillo, Daniele Rizzello, Pietro Balbi, Alessandro Ghirotto, Davide Scafidi, Guy Paxman, Andrea Zunino, Fausto Ferraccioli, Laura Crispini, Andreas Läufer, Frank Lisker, Antonia Ruppel, Danilo Morelli, and Martin Siegert

Recent sub-ice topography compilations of East Antarctica have imaged a wide sector, spanning from 100° E to 160° E in longitude and from the Oates, George V and Adelie coastlines to 85° S in latitude, which contains numerous low-lying basins of variable size and uncertain origin. The sector shows a Basin and Range style tectonics comprising two major basins of continental proportions, the Wilkes Basin and the Aurora Basin complex, and many smaller basins such as the Adventure, Concordia, Aurora and Vostok trenches. The main longitudinal axes of the basins consistently point towards the South Pole and many exhibit intriguing distinct triangular shapes, sitting within an approximately 2000 x 2000 km fan-shaped physiographic region limited by a semi-circular coast line. We name this region as the East Antarctic Fan shaped Basin Province (EAFBP). To the West, this sector is limited by the intraplate Gamburtsev Mountains (GM) and to the East by the Transantarctic Mountains (TAM) constituting the uplifted shoulder of the Cenozoic West Antarctic Rift System (WARS).

Origins and inter-relationships between these four fundamental Antarctic tectonic units (WARS, TAM, EAFBP, GM) are still poorly understood and strongly debated. Very little is known about the mechanism generating the basins in the EAFBP, their formation time, whether they are all coeval and if and how they relate to Australia basins before Antarctica-Australia rifting. Present genetic hypotheses for some of the basins span from continental rifting to a purely flexural origin or a combination of the two. Also, post-tectonic erosional and depositional processes may have had a significant impact on the present-day topographic configuration.

Here we interpret the EAFBP as the result of a single genetic mechanism: a wide fan-shaped intra-continental extension around a near pivot point at about 135° E, 85° S that likely occurred at the Mesozoic-Cenozoic transition. We discuss evidence from the sub-ice topography and potential field airborne and satellite data. We have applied image segmentation techniques to the rebounded sub-ice topography to semi-automatically trace the first order shape of the sub-ice basins, that we assume to be fault controlled. Then we have fitted the edges of the basins by maximum circles and estimated the best Euler pole identified by their intersection. Potential field anomalies have been taken into account in order to enlighten major discontinuities not revealed by the sub-ice topography.

The reconnaissance of this large sector of East Antarctica as the result of rotational extension may have major implications on global and regional tectonics plate reconstructions, plate deformation assumptions and new tectonic evolutionary models of WARS, TAM, and GM.

How to cite: Armadillo, E., Rizzello, D., Balbi, P., Ghirotto, A., Scafidi, D., Paxman, G., Zunino, A., Ferraccioli, F., Crispini, L., Läufer, A., Lisker, F., Ruppel, A., Morelli, D., and Siegert, M.: Some evidence of a wide rotational extension in East Antarctica preceding Gondwana breakup, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14808, https://doi.org/10.5194/egusphere-egu24-14808, 2024.

EGU24-14829 | Orals | TS2.1 | Highlight

The November 2023 Grindavik dike injection in Iceland:  Implications for continental rifting, dike formation in extensional tectonic settings, and giant dike swarms 

Freysteinn Sigmundsson, Michelle Parks, Halldór Geirsson, Andrew Hooper, Vincent Drouin, Kristín Vogfjörð, Benedikt Ófeigsson, Sonja H. M. Greiner, Yilin Yang, Chiara Lanzi, Gregory Paul De Pascale, Kristín Jónsdóttir, Sigrún Hreinsdóttir, Valentyn Tolpekin, Hildur María Friðriksdóttir, Páll Einarsson, and Sara Barsotti

A 15 km long dike formed rapidly in the Reykjanes Peninsula oblique rift on 10 November 2023 and propagated under the town of Grindavík.  From just before noon on 10 November until midnight, around 25 MW≥4 earthquakes occurred, two of which were of MW~5.2. Three-dimensional ground deformation is well resolved both temporally and spatially with dense Global Navigation Satellite System (GNSS) geodetic observations, which record cumulative displacements up to about 80 cm occurring mostly over 6 hours in the evening of 10 November and continuing at much reduced rates in the following days. Interferometric analysis of synthetic aperture radar images using Sentinel-1, COSMO-SkyMed, and ICEYE satellites records also well the dike deformation, which occurred simultaneously with deflation over the nearby central part of the Svartsengi volcanic system. Geodetic modelling, assuming uniform elastic host rock behavior, infers a dike volume of (130-139)×106 m3, with up to ~8 m dike opening, as well as some strike-slip shear motion. Deflation at Svartsengi in our model is best fit using a spherical point source with a volume decrease of (76-82)×106 m3up until 12 November. The temporal evolution of the dike opening was further modelled using hourly GNSS displacements, allowing better derivation of the temporal evolution of the flow rate into the dike and the contraction volume of the subsidence source. The maximum flow rate into the dike is inferred to be ~9500 m3/s, between 18:00 and 19:00 on November 10. We infer that the massive magma flow into the dike was established with only modest overpressure in the feeding magma body, a sufficiently large pathway opening at the boundary of the magma body, and pre-failure lowering of pressure along the pathway that had occurred through gradual build-up of high tensile stress over the previous eight centuries. This explains the unprecedented fast maximum magma flow rates that we infer. Such high flow rates provide insight into the formation of giant dike swarms under conditions of high tensile stress, and imply a high hazard potential for dike intrusions, considering their potential to transition into eruptions.

 

How to cite: Sigmundsson, F., Parks, M., Geirsson, H., Hooper, A., Drouin, V., Vogfjörð, K., Ófeigsson, B., Greiner, S. H. M., Yang, Y., Lanzi, C., De Pascale, G. P., Jónsdóttir, K., Hreinsdóttir, S., Tolpekin, V., Friðriksdóttir, H. M., Einarsson, P., and Barsotti, S.: The November 2023 Grindavik dike injection in Iceland:  Implications for continental rifting, dike formation in extensional tectonic settings, and giant dike swarms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14829, https://doi.org/10.5194/egusphere-egu24-14829, 2024.

EGU24-14830 | Posters on site | TS2.1

High precision U-Pb geochronology of Cenozoic phonolite volcanic bodies in Cenozoic Eger rift basin (Bohemian Massif) 

Prokop Závada, Vladimír Cajz, Andrew Kylander-Clark, and David Uličný

A new set of high-precision U-Pb data was acquired for two groups of phonolite bodies emplaced in the volcano-sedimentary sequence of the Cenozoic Eger Rift in Bohemian Massif. The phonolites are located in the western (5 bodies) and eastern (3 bodies) edge of this monogenetic volcanic field, stretched along the central part of the Eger Rift system. The selected phonolite bodies represent lava flows, cryptodomes or extrusive domes emplaced in phreatomagmatic maar-diatremes, remnants of dykes, and a laccolith. The U-Pb dates were acquired using the Laser Ablation Split Stream system at Santa Barbara University geochronology lab, which provides the coupled geochronology and also REE and selected major element geochemistry. Despite the great variety of internal zircon textures from oscillatory zoning to complex patchy patterns with a large range of cathodoluminescence intensity, the groups of spots gained coherent and surprisingly precise ages for each sample. The western group of phonolite bodies, namely the Bořeň, Želenický vrch, Špičák, Hněvín, and Ryzelský vrch display clusters of ages ranging between 33Ma and 36Ma, while zircons of the eastern group of the phonolites, Krompach, Mariánská hora and Luž (Lausche) indicate ages between 30Ma and 32Ma. Terra-Wasserburg diagrams for individual samples revealed remarkable precision marked by errors of only 90-180 thousand years (5 samples) and 300-650 thousand years (2 samples). The U-Pb zircon ages are interpreted to reflect primarily the high-temperature overprint of inherited (and possibly newly crystallized) zircons before emplacement of the phonolite bodies in the upper crust. In addition, titanite grains measured alongside the zircon grains (in another run) either overlap (Bořeň) with the zircon age error on Terra-Wasserburg diagrams (geochrone) or are 2 Ma years younger than corresponding zircon ages (Špičák phonolite body). REE binary diagrams revealed separate clusters of Sm/Nd and also Hf content of the zircons, which can be attributed to different degrees of partial melting of parental magma in the source upper mantle or the lower crust for both groups of sampled phonolites. In summary, the results suggest that U-Pb geochronology using the LASS system is a powerful tool with a great potential for deciphering the evolution of phonolites in the Cenozoic Rift system in Bohemian Massif and possibly other rift systems in the foreland of the Alpine orogeny.

This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S.

How to cite: Závada, P., Cajz, V., Kylander-Clark, A., and Uličný, D.: High precision U-Pb geochronology of Cenozoic phonolite volcanic bodies in Cenozoic Eger rift basin (Bohemian Massif), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14830, https://doi.org/10.5194/egusphere-egu24-14830, 2024.

EGU24-15107 | ECS | Posters on site | TS2.1

The evolution of fault networks during multiphase deformation: An analogue modeling approach 

Jun Liu, Matthias Rosenau, Ehsan Kosari, Sascha Brune, Frank Zwaan, and Onno Oncken

It is well known that triaxial deformation is a common feature of continental tectonics, and is accommodated by complex polymodal fault networks. Field investigations confirm that multiple phases involving time-dependent three-dimensional strain conditions (e.g. constriction, plane, and flattening strain) affect the spatial and temporal interaction of polymodal fault systems. However, a key question remains: How do changing strain conditions affect the reactivation of fault systems that formed during a previous deformation phase? Here, we conduct scaled analogue models with time-dependent boundary conditions to investigate how fault networks evolve under changing boundary conditions, including  reactivation and formation of new faults.

We have developed a setup in which a basal rubber sheet is stretched in one direction, so that longitudinal extension and layer thinning are accompanied by lateral shortening, hence producing triaxial deformation (Liu et al. in revision). According to previous brittle-viscous experiments with this set-up, an increase in longitudinal extension velocity results in a higher coupling between the rubber base and brittle layer, generating increasing transmission of lateral shortening from the base into the brittle layer. We thus induce constriction-to-plane strain conditions in the brittle layer as a function of longitudinal extension velocity by varying the magnitude of lateral contraction. In a new set of experiments, by varying extension velocity either stepwise or continuously, we realize time-dependent kinematic boundary conditions including deformation phases and secular changes, respectively. Digital image correlation (DIC) and photogrammetry (structure from motion, SFM) are employed to track the 3D kinematic surface and topography evolution, respectively.

Preliminary observations show both the formation of new faults and the reactivation of early phase faults through a change from plane to constriction strain. Conversely, a change from constriction to plane strain conditions results in the abandonment of the early phase fault network as it becomes overprinted by fault systems of the subsequent phase. Moreover, early-phase fault systems influence the propagation and linkage of fault populations in subsequent phases. Our analogue models highlight the impact of strain conditions on the overall plan-view geometry of fault populations, providing alternative explanations for complex fault patterns and interactions (e.g. the Jeanne d’Arc basin, the North Træna Basin, and the Beagle Platform).

How to cite: Liu, J., Rosenau, M., Kosari, E., Brune, S., Zwaan, F., and Oncken, O.: The evolution of fault networks during multiphase deformation: An analogue modeling approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15107, https://doi.org/10.5194/egusphere-egu24-15107, 2024.

EGU24-15188 | Posters on site | TS2.1

Insights into Miocene paleostress history of the Eger Rift from mining-related structural datasets: the Most Basin, Bohemia 

Radomír Grygar, Karel Mach, Roman Gramblička, and Tomáš Novotný

The Most Basin is the largest and best-preserved of sedimentary basins formed within the Eger Rift, the easternmost part of the European Cenozoic Rift System. Previous work on the tectono-sedimentary history of the basin and its surroundings has led to an interpretation of two main extensional phases that governed the Oligo-Miocene rift initiation and subsequent evolution. That interpretation has been derived mainly from large-scale considerations of main fault geometries, while a satisfactory support by a large mesoscopic dataset from the basin infill was lacking.

 

Systematic acquisition of mesoscopic structural data in some of the open-cast coal mines operating in the Most Basin has been motivated by prevention of accidents of bucket wheel excavators, threatened by sliding of blocks of mainly clayey sediments. As a result, over 5 thousand mesoscopic measurements were acquired in the Bílina Mine alone and hundreds in other mines over the past 13 years. In the Most Basin, the main coal seam is located close to the base of the basin fill. Open-case mines thus expose a thick overburden and, locally, also the underlying basement. The structural measurements involved the superposition and evolution of mesoscopic structural features in geological time, from Variscan metamorphic rocks through Cretaceous sediments and Oligocene volcanics through the Miocene coals and clastics of the basin fill.

 

Structural analysis of the dataset and statistical comparison of specific regions focused on

spatial and stratigraphic distribution of fault directions and inclination arrays, resulting in interpretation of spatial and stratigraphic distribution of local paleostress. The principal results are as follows:

  • the number of detected mesoscopic fault populations, as well as of interpreted deformation phases decreases upward through the stratigraphic column;
  • orientation of faults generally changes from a dominant E-W and NW-SE strike of population in the pre-Miocene formations into dominant SW-NE up to WSW-ENE strike within the youngest Libkovice Member (Early Miocene);
  • a trend of decreasing fault inclination from older, more consolidated formations to younger ones, most probably linked to rheological (stage of lithification) on brittle deformations;
  • generally, data evaluation of inclination and direction of faults gave generally similar results for the Bílina and Libouš mines, in spite of the 60 km distance between them and their proximity to different leading fault systems (Bílina and Victoria faults in the former case and the Ahníkov and Kralupy faults in the latter);
  • the large dataset of mesoscopic fault-slip data shows a generally more complex picture of possible paleostress evolution than the one derived from the geometries of the main bounding fault systems, due to the influence of local stress fields of normal and transtensional faults. The general picture, however, implies a plausible gradual evolution of extension vector from NNE-SSW to NW-SE orientations. throughout the early Miocene.

 

The Severočeské doly, a.s., supported the long-term acquisition of the structural dataset and its utilization for basic research purposes. This research has been supported by the Czech Science Foundation (GAČR) project 22-13980S.

How to cite: Grygar, R., Mach, K., Gramblička, R., and Novotný, T.: Insights into Miocene paleostress history of the Eger Rift from mining-related structural datasets: the Most Basin, Bohemia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15188, https://doi.org/10.5194/egusphere-egu24-15188, 2024.

EGU24-15268 | Orals | TS2.1

Shallow sources of upper mantle seismic anisotropy in East Africa  

Cynthia Ebinger, Miriam Reiss, Ian Bastow, and Mary Karanja

The East African rift overlies one or more mantle upwellings and it traverses heterogeneous Archaean-Paleozoic lithosphere rifted in Mesozoic and Cenozoic time. We re-analyze XKS shear wave splitting at publicly available stations to evaluate models for rifting above mantle plumes. We use consistent criteria to compare and contrast both splitting direction and strength, infilling critical gaps with new data from the Turkana Depression and North Tanzania Divergence sectors of the East African rift system. Our results show large spatial variations in the amount of splitting (0.1–2.5 s) but consistent orientations of the fast axes within rift zones: they are predominantly sub-parallel to the orientation of Cenozoic rifts underlain by thinned lithosphere with and without surface magmatism. The amount of splitting increases with lithospheric thinning and magmatic modification. Nowhere are fast axes perpendicular to the rift, arguing against the development of extensional strain fabrics. Thick cratons are characterized by small amounts of splitting (≤0.5 s) with a variety of orientations that may characterize mantle plume flow. Splitting rotates to rift parallel and increases in strength over short distances into rift zones, implying a shallow depth range for the anisotropy in some places. The shallow source and correlation between splitting direction and the shape of upper mantle thin zones suggests that the combination of channel flow and oriented melt pockets contribute > 1 s to the observed splitting delays. Enhanced flow, metasomatism, and melt intrusion at the lithosphere-asthenosphere boundary suggest that fluid infiltration to the base of the lithosphere may facilitate rifting of cratonic lithosphere. 

How to cite: Ebinger, C., Reiss, M., Bastow, I., and Karanja, M.: Shallow sources of upper mantle seismic anisotropy in East Africa , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15268, https://doi.org/10.5194/egusphere-egu24-15268, 2024.

EGU24-16081 | Orals | TS2.1

Reduced magmatism in the Turkana Depression: a consequence of inefficient melt transport 

Adina E. Pusok, Yuan Li, Richard F. Katz, Tim Davis, and Dave A. May

Geophysical studies along the Main Ethiopian Rift and Eastern Rift in Kenya indicate that strain accommodation is dominated by magmatic intrusion rather than tectonic extension (e.g., Ebinger and Casey, 2001). However, it remains unclear how magmatic extension developed in the Turkana Depression, the low-lying, broadly rifted region separating the Ethiopian and East African plateaus. We investigate the rifting dynamics of the Turkana Depression with two-phase flow numerical models of melt transport through the ductile–brittle lithosphere. These models suggest that the pre-rift rheological structure of the lithosphere exerts a counter-intuitive control on melt extraction, which can explain the character of the Turkana region.

Recent seismic imaging shows that both the Turkana Depression and the uplifted plateaus are underlain by deep-seated, hot, partially-molten, buoyant mantle that ponds below a thinned plate (Kounoudis et al., 2021). Yet, Ogden et al. (2023) estimated the Moho is 10–20 km shallower throughout the Turkana Depression (~20–25 km) than surrounding regions (~35–40 km). Here, we hypothesise that variations in lithospheric strength across the Turkana Depression and the Ethiopian Plateau have influenced magma transport across the lithosphere and rift development (Morley, 1994). 

Our models of melt extraction through the ductile–brittle lithosphere incorporate a new poro-viscoelastic–viscoplastic theory with a free surface (Li et al., 2023), designed and validated as a consistent means to model dykes. We initialise models with a source of partial melt in the asthenosphere and investigate how rheology of the overlying lithosphere impacts melt migration to the surface. Experiments are performed for buoyancy-driven magma transport under no tectonic extension, and for low background tectonic extension rates typical to the Turkana Depression (4 mm/yr; e.g., Knappe et al., 2020). Results indicate that both the rheology of lithosphere and extension rate control the efficiency of magma extraction. Magma transport across a thick, elastic lithosphere is more efficient than across a thin, more ductile lithosphere, and increases with extension. Our results suggest that surface volcanism in the Ethiopian Plateau is more likely to occur compared with the Turkana Depression, and at earlier times. 

References

Ebinger and Casey (2001), Geology, DOI: 10.1130/0091-7613(2001)029<0527:cbimpa>2.0.co;2

Kounoudis et al. (2021), G-cubed, DOI: 10.1029/2021GC009782

Ogden et al. (2023), EPSL, DOI: 10.1016/j.epsl.2023.118088

Morley (1994), Tectonophys., DOI: 10.1016/0040- 1951(94)90170-8

Knappe et al. (2020), JGR: Solid Earth, DOI: 10.1029/2019JB018469

Li et al. (2023), GJI, DOI: 10.1093/gji/ggad173

How to cite: Pusok, A. E., Li, Y., Katz, R. F., Davis, T., and May, D. A.: Reduced magmatism in the Turkana Depression: a consequence of inefficient melt transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16081, https://doi.org/10.5194/egusphere-egu24-16081, 2024.

EGU24-16240 | ECS | Posters on site | TS2.1

Insights into the tectonic evolution of the northern Norwegian passive margin: Integrating field observations and plate modeling over 200 million years. 

Amber Distelbrink, Grace E. Shephard, Jean-Baptiste P. Koehl, Steffen G. Bergh, and Anouk Beniest

Constraining the evolution of the opening of the northernmost region of the Northeast Atlantic Ocean is of particular importance for understanding the diversity of ocean basin opening dynamics, including the development of oblique margins and shear zones. Accurately determining the timing and kinematics of the motion along the Senja Shear Zone and opening of the Fram Strait is of particular importance for climate research as this region forms the only deep-water gateway between the Northeast Atlantic Ocean and Arctic Ocean. This study combines new and legacy data and presents an analysis of the tectonic evolution of the northern Norwegian passive margin over the past 200 Ma, including integrating structural field observations and plate tectonics models.

Fieldwork took place on the islands of Senja and Kvaløya in Troms County of northern Norway. The field observations reveal four dominant brittle fault groups corresponding to four normal-oblique extension directions: E-W, NNW-SSE, NW-SE, NE-SW. In the Senja Shear Zone, the strike-slip faults are predominantly oriented NNW-SSE to NW-SE. Analysis of existing plate motion models for the region for 200 Ma to present day includes three prominent extension phases in chronological order: E-W, NNW-SSE, and NW-SE.

This study suggests that during the E-W oriented crustal thinning phase, normal faulting and minor strike-slip faulting dominated and gave way to basement-seated strike-slip faults during the NNW-SSE oriented extension phase. The presence of mid-upper crust faulting is argued by fault mineral striation assemblages and hydrothermal alteration. In the NW-SE oriented extensional phase, both normal faults and strike-slip faults were active. Comparisons to existing rigid plate tectonic models for the region suggest a revised deformable plate framework is required, and offers insights into the original thickness of the North-American and European plates and the role of mid-crustal tectonics in the breakup. The role of inheritance, including earlier shear zones and extensional phases will also be discussed. In addition, the present research encourages scientists to digitize analogue maps and data, preventing loss of knowledge during the analogue to digital transition.

How to cite: Distelbrink, A., Shephard, G. E., Koehl, J.-B. P., Bergh, S. G., and Beniest, A.: Insights into the tectonic evolution of the northern Norwegian passive margin: Integrating field observations and plate modeling over 200 million years., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16240, https://doi.org/10.5194/egusphere-egu24-16240, 2024.

EGU24-17089 | Posters on site | TS2.1

The ANR project “FirstMove”: first movements of divergence between future tectonic plates 

Julia Autin, Roxane Mathey, Harmony Suire, Mélanie Ballay, Marc Ulrich, Gianreto Manatschal, Daniel Sauter, Benoît Petri, Marc Schaming, and Luis Somoza Losada

As two tectonic plates drift away, the earlier movements, prior to oceanic crust formation, are ill-constrained. We are convinced that the kinematic models of plate movements could be significantly enhanced by focusing on the divergence before final lithospheric breakup. During this phase of transition several problems arise. Firstly, the classical interpretations of magnetic anomalies are not trustworthy (debated geometry and/or origin of anomalies). Secondly, the movements are more complex than in oceanic domain (polyphase deformation, obliquity, asymmetry). Those particularities occur especially if plate breakup happens in magma-poor conditions where mantle is exhumed at the surface (in about 50% of instances).

We focus on two pairs of conjugate magma-poor rifted margins: the Bay of Biscay and the Australia-Antarctica margins. In these areas, magnetic anomalies are controversial and seafloor formation started with large domains of hyperextended continental crust and exhumed mantle. Thus, the location and age of the LaLOC (landward limit of the oceanic crust) are uncertain. We aim to better define these domains in space, divergence direction and time through geophysical data and localized petrological observations and dating. This project is in its starting phase, it includes 2 PhD thesis. This presentation focuses on the general framework of the project and the preliminary results.

How to cite: Autin, J., Mathey, R., Suire, H., Ballay, M., Ulrich, M., Manatschal, G., Sauter, D., Petri, B., Schaming, M., and Somoza Losada, L.: The ANR project “FirstMove”: first movements of divergence between future tectonic plates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17089, https://doi.org/10.5194/egusphere-egu24-17089, 2024.

EGU24-17201 | ECS | Posters on site | TS2.1

Structural Mode and Evolution of Multi-stage Normal Fault Development in Jieyang Depression, NE South China Sea 

Chao-Hsun Wang, Ping-Rong Wu, Kenn-Ming Yang, Chih-Cheng Yang, and Bieng-Zih Hsieh

Jieyang Depression is located between the Southern Depression of the Taixinan Basin and the Chaoshan Depression of the Pearl River Mouth Basin in northern South China Sea. A series of NE-SW striking half graben developed in this area from late Mesozoic to early Paleogene, and then another two stages of normal faulting happened during Neogene. The development of these stages of normal faults are separated by the breakup unconformity and a post-rift truncation. The main purposes of this study are to investigate the evolutionary sequences of the multi-stages of normal faults and the truncations during the multi-stages of extension, the spatial distribution of each phase of normal faults, and how the younger normal faults were affected by the pre-existing ones.

The normal faults in the Jieyang Depression can be divided into three types. Type 1 faults are related to the Paleogene half graben formation and only cut through the pre-rift and syn-rift strata. Type 2 normal faults only developed and cut through the post-rift strata. Type 3 normal faults cut through the syn-rift and post-rift strata. In this study, we further divide the Type 2 normal faults into two different kinds. Type 2-1 faults developed above the Paleogene half graben and cut off by the post-rift truncation. Type 2-2 faults developed after the truncation. Type 3 normal faults can be divided into two different kinds as well. Type 3-1 faults developed in the syn-rift stage and yet were reactivated and linked with the faults developing in the later extension. Type 3-2 faults are the Type 2 faults that developed continuously cutting downward into the syn-rift strata.

In terms of spatial distribution, Type 1 normal faults strike NE-SW, forming the half grabens. Most of the Type 2 normal faults are located far away from continental shelf. Type 3 normal faults mostly distribute on the northeast and northwest sides of the study area, close to the continental shelf, and most of them are cut by the post-rift truncation.

As a result, from the late Mesozoic to the early Paleogene, the northern slope of the South China Sea experienced a NW-SE extension. At the end of the Paleogene, the extension ceased, forming the breakup unconformity. In the Neogene, the Jieyang Depression experienced second extension. In this time the extension orientation was NNW-SSE, developing Type 2-1 and Type 3 faults before the post-rift truncation. The subsequent truncation cuts Type 2-1 faults and the upper part of the Type 3 faults. After accumulating new strata above truncation, the third stage of extension happened and Type 2-2 faults developed after the post-rift truncation.

Key words: South China Sea, Jieyang Depression, normal fault, multi-stage extension, truncation

How to cite: Wang, C.-H., Wu, P.-R., Yang, K.-M., Yang, C.-C., and Hsieh, B.-Z.: Structural Mode and Evolution of Multi-stage Normal Fault Development in Jieyang Depression, NE South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17201, https://doi.org/10.5194/egusphere-egu24-17201, 2024.

EGU24-17395 | ECS | Orals | TS2.1

Structure and kinematics of the Danakil Depression, Afar, Ethiopia: insights into the formation of a magma-rich margin 

Valentin Rime, Anneleen Foubert, Derek Keir, and Tesfaye Kidane

The Danakil Depression is situated in the northern part of the Afar Depression in Ethiopia and Eritrea and is in an advanced phase of rifting close to continental breakup. It forms the equivalent of a magma-rich margin. As it is currently active and emerged, it offers a unique opportunity to study the processes of formation of these types of passive margins.

We combine seismic reflection data, field data, and remote sensing to constrain the structure and kinematics of this basin. Seismic data reveal the formation of Seaward Dipping Reflectors (SDRs). Surprisingly, field data show that these SDRs are dominated by clastic sediments and only contain relatively minor amount of magmatic material. Paleoshorelines and other proxies allow to quantify uplift and subsidence rates across the basin. These data highlight high spatial variability and allow to better understand the structure and evolution of older, deeply buried passive margins.

How to cite: Rime, V., Foubert, A., Keir, D., and Kidane, T.: Structure and kinematics of the Danakil Depression, Afar, Ethiopia: insights into the formation of a magma-rich margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17395, https://doi.org/10.5194/egusphere-egu24-17395, 2024.

EGU24-17937 | ECS | Posters on site | TS2.1

Using U-Pb geochronology of syn-faulting calcite-mineralised veins to track the evolution of superimposed rifting events: the Inner Moray Firth Basin. 

Alexandra Tamas, Robert E. Holdsworth, Dan M. Tamas, Edward D. Dempsey, Kit Hardman, Anna Bird, John R. Underhill, Dave McCarthy, Ken J.W. McCaffrey, and David Selby

Constraining the age of formation and movement along fault arrays in superimposed basins helps us to better unravel their kinematic history as well as the role of bounding faults or inherited structures in basin evolution. The Inner Moray Firth Basin (IMFB, western North Sea) comprises a series of superimposed basins overlying rocks of the Caledonian basement, the pre-existing Devonian-Carboniferous Orcadian Basin and a regionally developed Permo-Triassic North Sea basin system. The IMFB rifting occurred mainly in the Upper Jurassic – Lower Cretaceous after a long period of subsidence followed by localised uplift in its eastern parts due to thermal doming in the central North Sea (in the middle Jurassic). The rift basin later experienced further episodes of regional tilting, uplift and fault reactivation during Cenozoic.

New detailed field observations augmented by drone photography and creation of 3D digital outcrops, coupled with U-Pb geochronology of syn-faulting calcite-mineralised veins are used to constrain the absolute timing of fault movements and decipher the kinematic history of basin opening. It also helps to identify those deformation structures associated with earlier basin-forming events.

Five regional deformation events emerge: Devonian rifting associated with the older Orcadian Basin; Late Carboniferous inversion related to dextral Great Glen fault movements; Permian thermal subsidence with some evidence of minor fracturing; Late Jurassic – Early Cretaceous rifting and Cenozoic reactivation and local inversion. We were also able to isolate characteristic structures, fault kinematics, fault rock developments and associated mineralisation types related to many of these events.

How to cite: Tamas, A., Holdsworth, R. E., Tamas, D. M., Dempsey, E. D., Hardman, K., Bird, A., Underhill, J. R., McCarthy, D., McCaffrey, K. J. W., and Selby, D.: Using U-Pb geochronology of syn-faulting calcite-mineralised veins to track the evolution of superimposed rifting events: the Inner Moray Firth Basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17937, https://doi.org/10.5194/egusphere-egu24-17937, 2024.

The presentation is based on the results of the research work of the Arktic-2011, Arktic-2014 and Arktic-2022 expeditions and contains the results of analysis of the structure of the sedimentary cover of the Eurasian basin of the Arctic Ocean. For the first time, the entire array of seismic data, including Russian and foreign seismic profiles, was used for tectonic constructions. The results obtained make it possible to reconstruct extensive areas of continental lithosphere development in the Eurasian basin. Based on the analysis of the structure of the sedimentary cover of the Amundsen Basin, four stages of the geological history of the formation of the sedimentary system of the Eurasian basin of the Arctic Ocean are substantiated. During the first (Cretaceous-Paleocene) stage, extensive axis-symmetric epicontinental paleo-basins of the Amundsen and Nansen Basins were formed on the shoulders of the continental rift, which were subsequently separated by seafloor spreading. Evidence of similar riftogenic settings in the second half of the Cretaceous is recorded along the entire periphery of the Arctic basin from Greenland to the Chukchi Rise. The second (Eocene)-spreading stage was characterised by stage accretion of the oceanic crust in the Gakkel Ridge and was accompanied by a gradual expansion of the sedimentary basin up to the present-day boundaries of the Eurasian basin. The third stage (Oligocene-Miocene) of sedimentary flexure corresponded to the accumulation of a thick undisturbed sedimentary cover over the entire Eurasian basin, indicating the temporary cessation of spreading in the Gakkel Ridge and the establishment of a tectonic quiescence regime. Similar conditions at this stage are recorded throughout the periphery of the Arctic basin. The resumption of spreading processes occurred at the fourth (Pliocene-Quaternary) neotectonic stage. As the result of the intensification of spreading processes in the Norwegian-Greenland Basin, tectonic stresses penetrated intothe Eurasian Basin along the axis of the Gakkel Ridge. The distinct morphological division of the Gakkel Ridge into Siberian-Marine and Atlantic segments is explained by the jump-like transmission of tectonic stresses of the North Atlantic, which is also confirmed by the anomalously high tectonic, volcanic and hydrothermal activity of the Gakkel Ridge.

How to cite: Neevin, I., Rekant, P., and Budanov, L.: MODEL OF THE FORMATION OF THE SEDIMENTATION SYSTEM OF THE EURASIAN BASIN OF THE ARCTIC OCEAN AS A BASIS FOR RECONSTRUCTING Its TECTONIC HISTORY, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18255, https://doi.org/10.5194/egusphere-egu24-18255, 2024.

EGU24-19671 | Orals | TS2.1

A generic crustal architecture data model for rift and passive margin analysis: Application to the conjugate South Atlantic margins 

Christian Heine, Ken McDermott, James Eldrett, Colin Grant, and Philip Thompson

The spatio-temporal analysis of rifts and passive margin evolution is often done based on regional case studies, using non-standardized terminology and classification models to characterize crustal boundaries and basin infill. As example, the use of “continent-ocean boundary” to delineate crustal types or “syn-rift” as basin infill characterization has proven to be no longer adequate, given our evolved understanding of passive margins. In general, such local approaches do not lean themselves to aggregate data for global and large-scale comparative analysis and often struggle to reconcile the spatially varying magmatic/weakly magmatic margin architecture in a rift system context. They also do not allow efficient deployment of spatio-temporal data analytic models due to a lack of standardized data classification.

To overcome these limitations, we have designed a novel “data science-ready” data model for crustal architecture that is based on commonly accepted terminologies, can be used independent of input data heterogeneity and can be deployed globally across the whole spectrum of margin types and complex 3D margin geometries/microplate settings. We classify two key crustal boundaries, the oceanward limit of continental crust ("OLCC") and the landward limit of oceanic crust ("LaLOC"), along with several key crustal interfaces, such as the top basement and base crust which are further subdivided into sub-categories. This approach allows us to easily generate standardized data products on rift system scale, which quantitatively describe key parameters relevant to understand lithosphere extension dynamics, such as volumes, ratio, and distribution of continental and magmatic crust, crustal stretching factors, and amount of crustal embrittlement. Coupled with plate kinematic models, these data products allow to build reproducible, extensible, and quantitative models of rift and margin evolution through time and highlight the dynamics of stretching, localization of deformation, the basin infill response, and spatio-temporally varying patterns and types of magmatism.

Applying this data model, we have characterized the crustal architecture of the conjugate South Atlantic passive margins, interpreting more than 100k line-kilometers of 2D and 3D seismic reflection data. Our findings highlight substantial shortcomings of current plate models to reconcile the crustal type distributions in the southern South Atlantic with a tight pre-breakup fit, the temporal emplacement dynamics of SDRs and plume-related magmatism along the whole South Atlantic rift, as well as the localization of deformation and dynamics of basin infill.

How to cite: Heine, C., McDermott, K., Eldrett, J., Grant, C., and Thompson, P.: A generic crustal architecture data model for rift and passive margin analysis: Application to the conjugate South Atlantic margins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19671, https://doi.org/10.5194/egusphere-egu24-19671, 2024.

EGU24-19853 | Posters on site | TS2.1

Synrift and postrift thermal evolution of margins: a re-evaluation of classic models of rifting 

Marta Pérez-Gussinyé, Yangfan Xin, Tiago Cunha, Raghu Ram, Miguel Andres-Martinez, Dongdong Dong, and Javier Garcia-Pintado

The thermal history of margins controls the development of hydrothermal systems during rifting, diagenetic processes in the sediments and the generation and preservation of hydrocarbons. It also affects the depth of the oceanic gateways formed during continental break-up, thereby influencing ocean circulation and ultimately climate (Brune et al., 2023, Pérez-Gussinyé et al., 2023, Peron-Pinvidic et al., 2019). Observed heat-flow values however, do not always comply with classic rifting models. Here, we use 2D numerical models to investigate the relationship between rifting, sedimentation and thermal history of margins. We find that during the synrift, the basement heat flow and temperature are not only controlled by extension factor, but also by synrift sediment thickness and the evolution of deformation. As this progressively focuses oceanward, the proximal sectors thermally relax, while the distal sectors experience peak temperatures. This time lag is important for wide rifted margins. In the postrift, the lithosphere under the hyperextended margins does not return to its original state, at least for ~100 Myrs after breakup. Instead, it mimics that of the adjacent oceanic plate, which is thinner than that of the original continental plate. This results in heat flow values increasing oceanward at postrift stages where classic rifting theory predicts complete thermal relaxation. Our increased heat-flow estimations, may extend hydrocarbon plays into distal margin sectors and adjacent oceanic crust, previously discarded as immature. Finally, our models indicate that commonly used temperature approximations in basin analysis may strongly differ from those occurring in nature (Pérez-Gussinyé et al., 2024).

 

Brune, S., Kolawole, F., Olive, JA. et al. Geodynamics of continental rift initiation and evolution. Nat Rev Earth Environ 4, 235–253 (2023). https://doi.org/10.1038/s43017-023-00391-3

Pérez-Gussinyé, M., Collier, J., Armitage, J., Hopper, J. R., Sun, Z., and Ranero, C. R., Towards a process-based understanding of rifted continental margins, in Nature Reviews Earth and Environment, 2023, doi: 10.1038/s43017-022-00380-y

Marta Pérez-Gussinyé, Yanfang Xin, Tiago Cunha,  Raghu Ram, Miguel Andrés-Martínez, Dongdong Dong, Javier García-Pintado,Synrift and postrift thermal evolution of rifted margins: a re-evaluation of classic models of extension, in press, Geol. Soc Spec. Publ., 2024

Peron-Pinvidic, G., Manatschal, G., eta al. Rifted Margins: State of the Art and Future Challenges, Front. Earth Sci., 22 August 2019, Sec. Structural Geology and Tectonics, Volume 7 - 2, https://doi.org/10.3389/feart.2019.00218.

How to cite: Pérez-Gussinyé, M., Xin, Y., Cunha, T., Ram, R., Andres-Martinez, M., Dong, D., and Garcia-Pintado, J.: Synrift and postrift thermal evolution of margins: a re-evaluation of classic models of rifting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19853, https://doi.org/10.5194/egusphere-egu24-19853, 2024.

EGU24-19947 | ECS | Posters on site | TS2.1

Interactions between pre-existing fabrics and fault patterns during oblique rifting revealed by enhanced-gravity analog modeling 

Yaoyao Zou, Daniele Maestrelli, Giacomo Corti, Chiara Del Ventisette, Liang Wang, Xiaofan Wan, Yanjie Gao, and Chuanbo Shen

 

Multiple fault populations with different orientations and complex fault patterns can be observed during oblique rifting, conditions which result from a complex rift kinematics which combines dip-slip and strike-slip motion. Although analysis of different natural cases and analog or numerical modeling have shed light on the relations between rift obliquity and the related fault architecture, many aspects of the process remain poorly understood. One of these aspects is related to the existence of pre-existing fabrics in the upper crust, which may further complicate the fault pattern by forcing the development of faults with atypical geometries and orientation.

Here, we performed enhanced-gravity analog models of oblique narrow rifting to characterize the evolution and architecture of rift-related faults developing in a brittle upper crust characterized by inherited fabrics. The models reproduce a rift obliquity of 30° (angle between the rift trend and the orthogonal to the direction of extension), kept constant in all the experiments, and pre-existing vertical fabrics with variable orientation (from 0°, i.e. orthogonal to extension, to 90°, i.e. extension-parallel). Modeling results suggest that inherited fabrics have an important influence on rift-related faulting, with a significant correlation between the intensity of reactivation and their trend with respect to the extension direction. When the pre-existing fabrics trend perpendicular to the extension direction (obliquity 0°), they are strongly reactivated, localizing deformation and promoting the rapid development of faults and grabens perpendicular to the extensional direction. When the pre-existing fabrics trend at moderate obliquity (15°-45°), they are still reactivated and localize deformation causing the development of atypical fault trends and patterns. The degree of reactivation tends to gradually decrease with increasing obliquity; similarly, the influence of pre-existing structures decreases with progressive extension, and the fault pattern and evolution are progressively dominated by extension kinematics and crustal thinning. When the pre-existing fabrics trend at high obliquity (≥ 60°), they have almost no influence on the fault geometry and architecture.

This study has significant implications for explaining the fault geometry and evolution of some natural rift basins worldwide, such as basins of the East African Rift system, the North Sea Rift, and some offshore rift basins in eastern China.

How to cite: Zou, Y., Maestrelli, D., Corti, G., Del Ventisette, C., Wang, L., Wan, X., Gao, Y., and Shen, C.: Interactions between pre-existing fabrics and fault patterns during oblique rifting revealed by enhanced-gravity analog modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19947, https://doi.org/10.5194/egusphere-egu24-19947, 2024.

EGU24-20162 | ECS | Posters on site | TS2.1 | Highlight

 The Last Fissural Eruptions of the Manda Hararo Magmatic Segment, Central Afar (Ethiopia), Constrained from New cosmogenic Ages 

Yafet Gebrewold Birhane, Raphael Pik, Nicolas Bellahsen, Irene Schimmelpfennig, Lydéric France, Jessica Flahaut, Dereje Ayalew, and Gezahegn Yirgu

The Afar depression at the northern end of the East African Rift system is presently experiencing the final stage of continental break-up and progressive onset of steady magmatic spreading. The Magmatic Rift Segments in Afar broadly analogous to those observed within the mid oceanic ridges, offer the opportunity to study both mantle and crustal processes. Investigating the crustal architecture of those magmatic segments represents a key aspect to decipher fundamental parameters that control focussing of magmatic and tectonic activity during the generation of magmatic crust. Here, we present the typical organization of a 32 km long subsegment of the Manda Hararo magmatic rift system, with fissural activities symmetrical to an apparent mid segment magmatic reservoir and establish geochronology of the last eruptive history. We combine field investigations, precise mapping of volcanological and tectonic features, cosmogenic 36Cl exposure dating and geochemical analysis of lavas to constrain the temporal frame and the dynamics of magmatic processes. Our results show that the recent historical volcanic events (~ 500 to 2000 years) are sourced from calderas and fissures representing an alternating sequence of effusive and explosive (block fields) activities related to a coherent rifting episode along a single self-consistent magmatic sub-segment. Those recent fissural flows resurfaced a large portion of the segment and emplaced on older thick pahoehoe flows with a rather long lag-time of about 75 kyr separating the two episodes. Strongly contrasted geochemical signatures are also observed between those two volcanic episodes, with more differentiated and trace elements enriched basalts for the recent one, compared to the older one which are characterized by a unusual depleted signature. These new results for the Central Afar Manda Hararo rift have important implications for: (i) the local hazards along the segments, and (ii) the volcano-tectonic organization of the segment with coexistence of contrasted melt reservoirs on the underlying transcrustal plumbing system.

How to cite: Birhane, Y. G., Pik, R., Bellahsen, N., Schimmelpfennig, I., France, L., Flahaut, J., Ayalew, D., and Yirgu, G.:  The Last Fissural Eruptions of the Manda Hararo Magmatic Segment, Central Afar (Ethiopia), Constrained from New cosmogenic Ages, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20162, https://doi.org/10.5194/egusphere-egu24-20162, 2024.

EGU24-20218 | ECS | Posters on site | TS2.1

Unraveling Tectonic From Hydrological Subsidence Of The Okavango Graben (Botswana) Using FLATSIM InSAR Data. 

Louis Gaudaré, Cécile Doubre, Marc Jolivet, Olivier Dauteuil, Samuel Corgne, Raphaël Grandin, Marie-Pierre Doin, and Philippe Durand

Located at the southwestern terminus of the East African Rift System, the Okavango Rift System represents an opportunity to study the propagation of an active rift at its early stages (Gaudaré et al., in review). The Okavango Graben (northern Botswana) is an active half-graben of the Okavango Rift System, which shows normal to dextral strike-slip tectonic displacements of the order of 1 mm per year (Pastier et al., 2017). In addition to the impact of tectonics, large volumes of water (~10 km3 per year) brought in by the annual flood of the Okavango River generate seasonal subsidence of over 2 cm in the graben (Dauteuil et al., 2023). The prevalence of the hydrologic signal over the tectonic signal makes it challenging to provide clear interpretations of the Rift dynamics within the Okavango Graben. The previous studies are based on a network of GNSS stations, providing punctual data on displacements. To quantify the deformation field over the Okavango Graben, we analyze interferometric synthetic aperture radar (InSAR) data produced by the ForM@Ter LArge-scale multi-Temporal Sentinel-1 InterferoMetry service (FLATSIM, Thollard et al., 2021). FLATSIM automatically computes interferograms from Sentinel-1 synthetic aperture radar data and inverts them into displacement time series. The products span from April 2016 to April 2021 with a temporal resolution of 12 days, a spatial resolution of 115 x 115 m and cover the entire Okavango Rift System. We analyze and compare the seasonality of both the interferometric coherences and the InSAR displacement time series. Change detection in the interferometric coherence allows us to delineate flooded surfaces through time in the Okavango Graben, from which we deduce water loadings on the lithosphere and model the corresponding flexural response of the lithosphere. We then compare this response to the spatial distribution of annual vertical oscillations extracted from the displacement time series. Taking these seasonal signals into account, our objective is to estimate the rates of the tectonic subsidence in the Okavango Graben to better constrain the propagation of the East African Rift System at its southwestern end.

Dauteuil, O., Jolivet, M., Gaudaré, L., & Pastier, A.-M. (2023). Rainfall-induced ground deformation in southern Africa. Terra Nova, 00, 1–7. https://doi.org/10.1111/ter.12650

Gaudaré, L., Dauteuil, O., & Jolivet, M. Geomorphology of the Makgadikgadi Basin (Botswana): insight into the propagation of the East African Rift System. Tectonics, in review.

Pastier, A.-M., Dauteuil, O., Murray-Hudson, M., Moreau, F., Walpersdorf, A., & Makati, K. (2017). Is the Okavango Delta the terminus of the East African Rift System? Towards a new geodynamic model: Geodetic study and geophysical review. Tectonophysics 712–713, 469–481. https://doi.org/10.1016/j.tecto.2017.05.035

Thollard, F., Clesse, D., Doin, M.-P., Donadieu, J., Durand, P., Grandin, R., Lasserre, C., Laurent, C., Deschamps-Ostanciaux, E., Pathier, E., Pointal, E., Proy, C., & Specht, B. (2021). FLATSIM: The ForM@Ter LArge-Scale Multi-Temporal Sentinel-1 InterferoMetry Service. Remote Sensing, 13(18), 3734. https://doi.org/10.3390/rs13183734

How to cite: Gaudaré, L., Doubre, C., Jolivet, M., Dauteuil, O., Corgne, S., Grandin, R., Doin, M.-P., and Durand, P.: Unraveling Tectonic From Hydrological Subsidence Of The Okavango Graben (Botswana) Using FLATSIM InSAR Data., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20218, https://doi.org/10.5194/egusphere-egu24-20218, 2024.

EGU24-20223 | Posters on site | TS2.1

Interaction of tectonics and surface process during oblique rifted margin formation. Insights from 3-D forward coupled geodynamic-surface process modelling. 

Thomas Theunissen, Ritske S. Huismans, Delphine Rouby, Sebastian Wolf, and Dave A. May

The magma-poor passive rifted conjugate margins in the Southern Equatorial Atlantic, North Atlantic/Arctic oceans, and Northern Mozambique Channel display en-echelon extensional segments separated by long transform faults (>300 km), influenced by inherited weaknesses. Using advanced 3-D forward geodynamic modeling coupled with surface processes, we investigate the formation of oblique rifts and passive margins. Our focus is on pre-existing weaknesses parallel to the extension direction, exploring the system's sensitivity to various erodibility factors. Key findings include: (1) erodibility within a low to moderate range has limited influence on the morpho-structural evolution of the oblique continental rift, (2) pure-strike slip faults reactivating transform weaknesses result in reduced topography, (3) major catchments sink in the inner corner at the tip of each extensional segments, and (4) hinterland drainage network capture along extensional segments is absent, controlled by isostatic rebound during rift flank drainage divide migration. This study enhances our understanding of the complex interplay between inherited weaknesses, erodibility, and the evolving morphology of oblique rifted margins.

How to cite: Theunissen, T., Huismans, R. S., Rouby, D., Wolf, S., and May, D. A.: Interaction of tectonics and surface process during oblique rifted margin formation. Insights from 3-D forward coupled geodynamic-surface process modelling., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20223, https://doi.org/10.5194/egusphere-egu24-20223, 2024.

EGU24-20850 | Posters on site | TS2.1

The Ross Sea formation: enquiring the sensitivity of basin architecture to prior conditions, with numerical models and a parameter search 

Martina Busetti, Alberto Pastorutti, Magdala Tesauro, Carla Braitenberg, Florence Colleoni, and Laura De Santis

The basins composing the 1000-km wide West Antarctica Rift System (WARS), derived from extensional dynamics lasting from the Cretaceous to the Middle Neogene, bear evidence of a peculiar evolution through time: a transition from a diffuse to a localized thinning style and a migration of the focus of deformation, which likely progressed towards the cratonic domains of West Antarctica. Using the current observations, we aim at identifying which inherited starting conditions [1] result in outcomes compatible with the present-time structures and which do not allow so, unless other factors are accounted for.

To this aim, we turn to an extensive grid search in the parameter space, running a large number of forward numerical models to cover the possible permutations of parameters under test. We use the open source Underworld2 code [2] with a simplified scheme of starting conditions and kinematics boundaries, for lithospheric-scale 2-D thermomechanical models. We analyse the results obtained by changing a great number of parameters, including initial geometries of the crust and lithosphere, different rheologies, inherited structures, such as strain-weakening scars and thermal remnants of slabs.

We identify that a high crustal thickness (more than 45 km) is required to accommodate the first rifting phase (170 km ca. of cumulated extension, [3]) without producing crustal necking and eventual ocean formation. Parameters that favour a weaker strength profile, chiefly temperature (due to a thicker crust and/or a shallow lithosphere-asthenosphere boundary), are also required to avoid an early transition to localized deformation, in agreement with previous studies [4]. Smaller scale features, such as partition in multiple sub-basins, require additional factors, such as inherited weak-zone seeds (“scars”) in the crust and mantle, which are likely remnants of previous compressive phases [5].

[1] Perron, P., Le Pourhiet, L., Guiraud, M., Vennin, E., Moretti, I., Portier, É., & Konaté, M. (2021). Control of inherited accreted lithospheric heterogeneity on the architecture and the low, long-term subsidence rate of intracratonic basins. BSGF - Earth Sciences Bulletin, 192. https://doi.org/10.1051/bsgf/2020038

[2] Mansour, J., Giordani, J., Moresi, L., Beucher, R., Kaluza, O., Velic, M., Farrington, R., Quenette, S., & Beall, A. (2020). Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud. Journal of Open Source Software, 5(47), 1797. https://doi.org/10.21105/joss.01797

[3] Brancolini, G., Busetti, M., Coren, F., De Cillia, C., Marchetti, M., De Santis, L., Zanolla, C., Cooper, A.K., Cochrane, G.R., Zayatz, I., Belyaev, V., Knyazev, M., Vinnikovskaya, O., Davey, F.J., Hinz, K., 1995. ANTOSTRAT Project, seismic stratigraphic atlas of the Ross Sea, Antarctica. In: Cooper, A.K., Barker, P.F., Brancolini, G., (Eds.), Geology and Seismic Stratigraphy of the Antarctic Margin. Antarctic Research Series, vol. 68, https://doi.org/10.1029/AR068

[4] Huerta, A. D., & Harry, D. L. (2007). The transition from diffuse to focused extension: Modeled evolution of the West Antarctic Rift system. Earth and Planetary Science Letters, 255(1–2), 133–147. https://doi.org/10.1016/j.epsl.2006.12.011

[5] Talarico, F., Ghezzo, C., & Kleinschmidt, G. (2022). The Antarctic Continent in Gondwana: a perspective from the Ross Embayment and Potential Research Targets for Future Investigations. In Antarctic Climate Evolution (pp. 219–296). Elsevier. https://doi.org/10.1016/B978-0-12-819109-5.00004-9

How to cite: Busetti, M., Pastorutti, A., Tesauro, M., Braitenberg, C., Colleoni, F., and De Santis, L.: The Ross Sea formation: enquiring the sensitivity of basin architecture to prior conditions, with numerical models and a parameter search, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20850, https://doi.org/10.5194/egusphere-egu24-20850, 2024.

EGU24-617 | Posters virtual | GM6.4

Assessment of Suspended Sediment Dynamics in the Largest Peninsular Basin of India 

Anubhuti Singh, Somil Swarnkar, Soumya Kundu, and Shivendra Prakash

The Godavari River Basin (GRB), the biggest Peninsular Indian basin, has experienced a major decline in both streamflow and sediment discharge since 1965, with a particularly notable loss occurring after around 1990. Previous studies reported an overall decrease of suspended sediment load around 123 Mt/year in the GRB, which places it as the third highest among all major river basins worldwide. However, there is a lack of adequate understanding of the consequences of reservoir operations, variations in flow, and the broader dynamics of sediment.  Here, we employed a dataset provided by the Central Water Commission (CWC), India, to better comprehend the fluctuations in suspended sediment load and discharge throughout different regions of the GRB. Our research focuses on analyzing the relationship between the variability of suspended sediment load and its response to factors such as dam constructions and discharge fluctuations. Our research findings indicate that a significant number of gauging stations had a decline of more than 50% in suspended sediment load after 1990. Further investigation clearly demonstrates a substantial decrease in suspended sediment load after 1990 due to the entrapment of suspended sediment load induced by the installation of large-scale dams. The temporal change in suspended sediment load in the Godavari and its main tributaries is associated with the rise in human activities observed in recent decades. The findings of this study have important significance for recognizing the complex relationships between land use land cover, suspended sediment loads, soil erosion, and reservoir management in the GRB.  In addition, this study can provide valuable information for policymakers to adopt more effective reservoir management, soil erosion control, and soil-water conservation measures in the GRB.

How to cite: Singh, A., Swarnkar, S., Kundu, S., and Prakash, S.: Assessment of Suspended Sediment Dynamics in the Largest Peninsular Basin of India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-617, https://doi.org/10.5194/egusphere-egu24-617, 2024.

EGU24-2975 | ECS | Posters on site | GM6.4

Initiation of the Central Tibet Watershed Mountains in Qiangtang: Insights from Provenance Mapping of Detrital Zircon Data Set 

Jiawei Zhang, Yalin Li, Huiping Zhang, and Jiarun Tu

The heterogeneous Tibetan lithosphere has led to the formation of distinct geomorphic units on the plateau surface over the past ~250 Myr. One prominent topographical feature is the delineation of intervening sedimentary basins by high mountain belts. Unlike the high and rugged Kunlun, Gangdese and Himalaya Mountains, the Central Tibet Watershed Mountains (CTWM) in the Qiangtang terrane exhibit a relatively low relief of ~1 km or less compared with surrounding basins. They are important geological and geographical barriers with perspectives on the formation process that are subject to dispute. The outburst of detrital zircon geochronology data sets in the Qiangtang basin provides an opportunity to address this issue. The combination of inverse and forward modeling of 6197 detrital zircon U-Pb ages enables the establishment of provenance mapping, which averts tedious descriptions of individual age modes. Integrated with petrographic analysis and paleocurrents, the provenance of the Jurassic Qiangtang basin is quantitatively constrained. The CTWM remained consistently significant sources throughout the Jurassic time. Internal sources of Triassic and Jurassic magmatic rocks locally supplied younger zircon grains. The source proportion of the Hoh Xil- Songpan Ganze (HSG) terrane increased across the basin in the Middle Jurassic but decreased dramatically in the Southern Qiangtang in the Late Jurassic. Contextualized in geological details, an embryonic watershed that separates rivers flowing into the Pacific and Indian oceans formed in central Tibet during the Late Jurassic.

How to cite: Zhang, J., Li, Y., Zhang, H., and Tu, J.: Initiation of the Central Tibet Watershed Mountains in Qiangtang: Insights from Provenance Mapping of Detrital Zircon Data Set, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2975, https://doi.org/10.5194/egusphere-egu24-2975, 2024.

EGU24-3451 | ECS | Orals | GM6.4

Grain size distribution of bulk-sample, detrital zircons and rutiles from the Yangtze River: implications for the sediment routing 

Rujun Guo, Xilin Sun, Chang’an Li, Wencke Wegner, Zengjie Zhang, Chuanyi Wei, Yawei Li, and Urs Klotzli

Changes in the grain size distribution of river sediment have environmental, ecological and social implications. This study investigated the variation of the grain size of bulk samples, detrital zircons and rutiles from the mainstream and major tributaries of the Yangtze River. The mean size of bulk samples from the upper reaches is significantly higher than the mid-lower reaches. The Equivalent Spherical Diameter (ESD) of most zircons (from previous work) and rutile grains fall within the range of 32-250 μm with dominant size of 63-125 μm. Coarse-sized zircons and rutiles with ESD of 125-250 μm are found in higher proportions in the upper reaches than in the mid-lower reaches, and a significant grain size decrease is observed downstream of the Three Gorges Dam. The significantly decreasing in coarse grains downstream of the dam indicates that the massive sediment contributed by the Three Gorges Dam (TGD), especially coarse-sized sediment. Our study demonstrates that a complex sediment routing system like the Yangtze River is interrupted by the Three Gorges Dam. The problem of grain-size bias caused by human activities on age-data acquisition and interpretation of detrital minerals (rutile and zircon) from large rivers is not negligible and deserves more attention when using single grain geochronology to constrain sediment provenance and tectonic evolution.

How to cite: Guo, R., Sun, X., Li, C., Wegner, W., Zhang, Z., Wei, C., Li, Y., and Klotzli, U.: Grain size distribution of bulk-sample, detrital zircons and rutiles from the Yangtze River: implications for the sediment routing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3451, https://doi.org/10.5194/egusphere-egu24-3451, 2024.

EGU24-4832 | Posters on site | GM6.4

Dynamic drainage reorganization in the eastern Tibetan Plateau: A perspective from the First Bend of the Yangtze River 

Xudong Zhao, Huiping Zhang, Yifei Li, and Richard Lease

The establishment of modern drainage patterns of large rivers in eastern Tibet is thought to have resulted from drainage reorganization by serial river capture and reversal events, but the timing and driving mechanisms are still under debate. The capture that created the First Bend of the Yangtze River (YFB) is the most well-known event but also the most controversial. Here, sedimentary provenance of Late Miocene–Quaternary Dali basin strata south of the YFB demonstrates that a south-flowing Jinsha River briefly drained the Dali basin at ~7.4–6.4 Ma. This would require the occurrence of two fluvial diversions at the YFB, before 7.4 Ma and after 6.4 Ma, respectively. Together with landscape evolution modeling results, we infer that a river-blocking landslide downstream of the YFB and resulting lake overspill may have been responsible for this drainage reorganization process. Our results highlight for the first time that river-damming landslides may be a key mechanism for driving dynamic drainage reorganization in eastern Tibet.

How to cite: Zhao, X., Zhang, H., Li, Y., and Lease, R.: Dynamic drainage reorganization in the eastern Tibetan Plateau: A perspective from the First Bend of the Yangtze River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4832, https://doi.org/10.5194/egusphere-egu24-4832, 2024.

EGU24-8988 | ECS | Orals | GM6.4

Autogenic vs Subsidence Controls on Fluvial Stratigraphic Grain Size Fining through Multi-Channel Landscape Evolution Modelling 

Amanda Wild, Jean Braun, Alex Whittaker, and Sebastien Castelltort

Grain size within the stratigraphic record is often used to interpret changes in tectonics and climate. For example, past work has described the influence of underlying subsidence or flux oscillations due to climate on grain size fining rates within the basin. However, little research has deconstructed the role of internal dynamics in shaping the grain size fining rates preserved within strata under varied basin geometries, precipitation gradients, and bypass states of basin evolution. Through the combination of a landscape evolution model based on the Stream Power Law modified for sedimentation by Yuan et al. (2019) with an extension of the self-similar grain size model of Fedele and Paola (2007) into multiple dimensions (i.e., along dynamically evolving river channels) by Wild et al (in review), we have developed a steady-state framework identifying autogenic vs subsidence dominated grain size fining. When basin accommodation is high relative to incoming flux, or early in the basin evolution, grain size fining is primarily subsidence-dominated regardless of precipitation gradients and basin geometries. Alternatively, under high bypass and low underlying accommodation, grain size fining is autogenically dominated and controlled by relative upstream discharge (or the ratio of the upstream, mountain catchment area vs the downstream, sedimentary system area). Foreland basins (eg: the Alberta foreland basin) with ample downstream area tend to evolve from a high subsidence to autogenic dominated state as they fill over time. Constrained downstream areas (eg: Death Valley fans) display a minimal autogenic impact on grain size fining regardless of their bypass state. We will present our modelled stratigraphic results and compare them to natural systems, such as the Alberta Foreland basin and alluvial fans of Death Valley.

How to cite: Wild, A., Braun, J., Whittaker, A., and Castelltort, S.: Autogenic vs Subsidence Controls on Fluvial Stratigraphic Grain Size Fining through Multi-Channel Landscape Evolution Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8988, https://doi.org/10.5194/egusphere-egu24-8988, 2024.

EGU24-9769 | ECS | Orals | GM6.4 | Highlight

Understanding coastal response to sea level rise in Northern Italy: the Holocene history of the Tagliamento river delta 

Wouter Gerats, Timme Donders, Maarten van der Vegt, Alessandro Fontana, Esther Stouthamer, and Kim Cohen

Many deltas worldwide are at the risk of drowning under projected future rates of sea-level rise. Understanding the morphodynamic response of deltas through stages in the Holocene, is crucial to know their current state and determine their future and to take effective action.

To understand the relation of coastal-plain morphology and substrate with history of vegetation cover, sediment supply, tides and salinity gradients, between vegetation cover, sediment supply and coastal morphology we examine the history of the Tagliamento river delta in Northern Italy, a backbarrier coastal system with large lagoonal areas. This river mouth is one of the morphologically intact in Europe, even though it has experienced a long history of human presence. We combine a large dataset of 4,000 core descriptions with detailed proxy-analyses of multiple cores to map accretion surfaces in time and link them to past changes in vegetation, sea level and climate. Lithology, pollen data and C-14 ages provide quantitative information on infill rates and landscape change and human influence. Resulting geologic transects and paleogeographic maps show the 3D infill history of the former lagoon and provide constraints on sediment fluxes and degree of marine ingression. First results from pollen analysis and sedimentology show clear local and region changes in vegetation cover but relatively late and low direct human influence. Further work will attempt to confront the reconstructions with idealized model simulations of sediment budgets and geomorphology at selected moments in time.

How to cite: Gerats, W., Donders, T., van der Vegt, M., Fontana, A., Stouthamer, E., and Cohen, K.: Understanding coastal response to sea level rise in Northern Italy: the Holocene history of the Tagliamento river delta, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9769, https://doi.org/10.5194/egusphere-egu24-9769, 2024.

EGU24-9855 | Orals | GM6.4

A two-stage river capture event in Corsica and its impact on erosion rates and offshore sedimentation 

Marco Giovanni Malusa', Alberto Resentini, and Hella Wittmann

The source-to-sink system of the Golo River, the largest catchment of Corsica (Western Mediterranean) is a well-established test case for inferring erosion rate variations from the sedimentary record in a quiescent tectonic setting. Previous studies have analyzed the onshore part of the source-to-sink system during late Quaternary climatic and sea level variations, and the offshore sink to highlight the main variations in sediment yield during the late Pleistocene and the last glacial cycle. Here we expand the analysis of the river network of Corsica and of the offshore sink back to the Miocene, when the region was still tectonically active. Based on a unique set of geological and in situ 10Be cosmogenic data, we show how the landscape have responded and is still responding to the disequilibrium caused by the late Miocene uplift of Alpine Corsica, and we provide evidence of a two-stage river capture event affecting the river network during the Pliocene. Our data reveal that ~1280 km2 of basin area originally draining towards the Ligurian Sea was abruptly connected in the Pliocene to the Tyrrhenian Sea through headward erosion. River capture led to the formation of a large Pliocene-Quaternary submarine fan offshore the Tyrrhenian coast, associated to an increased sediment yield that was three times greater than the average sediment yield in the same source-to-sink system during the Holocene. Such a major change in sediment flux towards the Tyrrhenian margin was greater magnitude than any subsequent peaks in sediment yield documented during Pleistocene glaciations. In situ 10Be cosmogenic data demonstrate that erosion is focused on previous capture sites even today, which indicates persistence of disequilibrium after millions of years. Our findings suggest that using the sedimentary archive to infer tectonic growth of topography or climate changes is not straightforward and may lead to incorrect interpretation unless river piracy can be safely excluded.

How to cite: Malusa', M. G., Resentini, A., and Wittmann, H.: A two-stage river capture event in Corsica and its impact on erosion rates and offshore sedimentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9855, https://doi.org/10.5194/egusphere-egu24-9855, 2024.

EGU24-10220 | Posters on site | GM6.4

Grain-size and morphoscopy analyses of surficial cover associated with an alluvial fan complex and low river terraces in the Grande and Fêmeas Rivers, western region of the state of Bahia, Brazil. 

Tania Augusto da Silva Santos, Icaro Gabriel Lima Machado, João Pedro Bedendo, Artur Magalhães Brito, Emanuelly Cristina Leal Silva, José João Lelis Leal de Souza, and André de Oliveira Souza

Located in the western region of Bahia state, Brazil, the Fêmeas and Grande rivers are important tributaries of the São Francisco River. Despite the significance of these systems for the regional and national contexts, few studies have addressed the geomorphological processes and dynamics throughout the Holocene in these areas. Thus, through the characterization of grain size and morphoscopy of 100 quartz grains from deposits corresponding to an alluvial fan complex and low fluvial terrace on the left bank of the Fêmeas River, as well as two low fluvial terraces of the Grande River (one on each bank), we aim to identify discontinuities indicative of changes in morphodynamic processes throughout the Holocene. The results have shown that in the low fluvial terrace on the left bank of the Grande River, the deeper layers (45-90 cm) present values for the silt and clay fractions of 1.7% and 1.3%, respectively. On the other hand, in the more superficial layer (0-10 cm), the values for the silt and clay fractions were 5.5% and 6.7%, respectively. The values for the fine sand fraction in all layers averaged from 69.8% to 86.4%. No changes were observed in the morphoscopy of quartz grains, with rounded and sub-discoidal grains being predominant. On the right bank, the fluvial deposit predominantly showed silt and clay fractions with values of 24.8% and 29.9% at greater depths (40-60 cm), while on the surface (0-30 cm), the values for these fractions significantly decreased, reaching values of 6.3% and 12.7%. Morphoscopy analyses resulted in mostly sub-rounded and sub-discoidal grains. In the alluvial fan complex of the Fêmeas River basin, erosive-depositional discontinuities were identified in a deposit corresponding to the proximal facies of the complex. The results have shown differentiations in the clay, silt, fine sand, and coarse sand fractions at 0-70 cm, as well as an increase in the clay fraction in deeper layers, with values ranging between 36.9% and 40.8%. Morphoscopy analyses indicated 36.8% sub-rounded grains and 50% spherical-rounded grains. In another deposit with a thickness of 140 cm and corresponding to the distal facies of the alluvial fan complex, the results showed a decrease in coarse sand values to fine sand in deeper layers. Morphoscopy indicated predominantly sub-rounded grains in the more superficial layers (0-50 cm), predominantly rounded grains in the intermediate layer (50-70 cm), while the deeper layers (70-140 cm) presented sub-rounded and rounded grains. Overall, this deposit showed 13.2% sub-angular grains. Finally, our results indicated significant variations in silt and clay fractions, which, when analysed together with morphoscopy, suggest energetic variations in depositional processes throughout the Holocene. This research has been funded by the Bahia State Research Support Foundation (Grant 4341/2022).

How to cite: Santos, T. A. D. S., Machado, I. G. L., Bedendo, J. P., Brito, A. M., Silva, E. C. L., de Souza, J. J. L. L., and Souza, A. D. O.: Grain-size and morphoscopy analyses of surficial cover associated with an alluvial fan complex and low river terraces in the Grande and Fêmeas Rivers, western region of the state of Bahia, Brazil., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10220, https://doi.org/10.5194/egusphere-egu24-10220, 2024.

EGU24-11242 | Orals | GM6.4

Foredeep inclusions into foreland molasse in the North Dalmatian foreland basin, Croatia – from sink to source? 

Katarina Gobo, Borna Lužar-Oberiter, Danijel Čičak, and Ervin Mrinjek

The sedimentary infill of peripheral foreland basins records an intricate relationship between the development of the thrust wedge and related isostatic adjustments, eustasy, and sedimentation processes, posing challenges to the classical source-to-sink concept. The evolution of such basins commences with an “underfilled” flysch stage in the foredeep depozone and passes to a filled and finally an “overfilled” molasse stage in the orogen-proximal zone (Sinclair, 1997). On basin-scale, progressively younger sediments exhibit a regressive character, with the molasse commonly being deposited in alluvial environments.

This study from the North Dalmatian foreland basin in Croatia documents a peculiar gravel association in the alluvial conglomerates of the foreland molasse. These deposits are the youngest unit of the Promina Beds – a calciclastic succession that was deposited in the wedge-top depozone in shallow-marine, marginal marine, and terrestrial environments from the middle Eocene to the late Oligocene (Mrinjek et al., 2012). The alluvial conglomerates were deposited on Oligocene alluvial fans or in proximal braided-river settings (Mrinjek et al., 2012). Besides limestone clasts derived from Cretaceous bedrock, these conglomerates comprise well-rounded calciclastic cobbles and boulders. These clasts are fine-grained calcarenites, whose carbonate content ranges from 61 to 99%. Their macroscopic features resemble sandstones of Eocene flysch that crop out 16 km to the southwest, but samples from these two units show significant differences in microfossil content and heavy mineral associations. Large benthic foraminifera and sporadic planktic forms are found in the Eocene flysch, which was deposited in the prodelta zone of a river-fed delta (Babić & Zupanič, 2008). Contrarily, the calciclastic gravel clasts of the alluvial unit bear more planktic than benthic foraminifera, suggesting original deposition in a deeper and more distal marine environment. The clasts are rich in muscovite (32%), opaque heavy minerals (24%), and biotite (19%), with subordinate transparent heavy minerals (12%). Flysch samples show a coequal abundance of opaque (39%) and transparent heavy minerals (40%). Among the latter, garnet is the most abundant.

These preliminary results suggest that the calciclastic gravel clasts of the alluvial unit most likely derive from a foredeep setting older than the Eocene flysch, that was probably located in the hinterland of the present-day thrust-wedge. The heavy mineral assemblage suggests provenance from metamorphic, igneous, or recycled sedimentary rocks from the Internal Dinarides. Therefore, drastic geomorphic changes must have occurred during the development of the foreland basin, with deep-marine sediments being deposited, subsequently uplifted, eroded, transported, and deposited in continental environments, which will eventually become a new source for a future sink.

 

CITED REFERENCES:

Babić, Lj., Zupanič, J. 2008. Evolution of a river-fed foreland basin fill: the North Dalmatian flysch revisited (Eocene, Outer Dinarides). Natura Croatica, 17/4, 357–374.

Mrinjek, E., Nemec, W., Pencinger, V., Mikša, G., Vlahović, I., Ćosović, V., Velić, I., Bergant, S., Matičec, D. 2012. The Eocene-Oligocene Promina Beds of the Dinaric Foreland Basin in northern Dalmatia. Journal of Alpine Geology, 55, 409–451.

Sinclair, H.D. 1997. Tectonostratigraphic model for underfilled peripheral foreland basins: An Alpine perspective. GSA Bulletin, 109/3, 324–346.

How to cite: Gobo, K., Lužar-Oberiter, B., Čičak, D., and Mrinjek, E.: Foredeep inclusions into foreland molasse in the North Dalmatian foreland basin, Croatia – from sink to source?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11242, https://doi.org/10.5194/egusphere-egu24-11242, 2024.

EGU24-11556 | ECS | Posters on site | GM6.4

Modelling Solutions for Ferricrete Formation and their Impacts on Topography 

Caroline Fenske, Jean Braun, François Guillocheau, and Cécile Robin

Ferricretes, or iron duricrusts, are hard iron layers, which predominantly develop in tropical and subtropical environments. They commonly cap elevated topographical features, potentially safeguarding old landscapes. The genesis of duricrusts is intricately tied to climatic conditions, particularly relying on intense seasonal precipitation cycles.

Two hypotheses for iron duricrust formation exist: the hydrological or horizontal hypothesis and the laterisation or vertical hypothesis. In the first case, elements forming the duricrust are transported from distant areas and concentrated by hydrological processes. In the second case, the protolith is the underlying basement, and ferricretes form through leaching of soluble elements and compaction of less soluble ones.

As no numerical model has been proposed for ferricrete formation until recently, we incorporated both formation hypotheses in a previously described numerical model for regolith formation (Braun et al., 2016).  The hydrological model was profusely described last year (Fenske et al. at EGU23), thus, we will concentrate on the laterisation model. In accordance with the second hypothesis, ferricrete formation follows laterisation of the regolith. During laterisation, the most soluble elements gradually dissolve and leach, resulting in the enrichment of non-soluble elements like iron and compaction. The model is characterized by two parameters: the time scales for iron enrichment τl and compaction τc, respectively. Various numerical scenarios were performed under diverse tectonic and climatic. The threshold Ωmin was determined to state formation or not of ferricretes.

To calibrate the model, a case study has been defined in the southeastern part of Brazil, the Quadrilátero Ferrífero (QF) region. Ranging almost 7 000 km², this region is known for its abundance in iron ores and distinct topography with escarpments and high plateaus commonly topped by cangas. Cangas are a type of ferricrete which form from the weathering of BIFs (Banded Iron Formations). The oldest registered formations are up to 70 Ma old and seem to protect some of the mountain peaks for extended periods of time. Multiple scenarios are proposed to describe today’s landscape, with different climatic and tectonic parameters in play. With the help of the laterisation model, it is possible to model different scenarios to attempt to depict the formation of the QF.

How to cite: Fenske, C., Braun, J., Guillocheau, F., and Robin, C.: Modelling Solutions for Ferricrete Formation and their Impacts on Topography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11556, https://doi.org/10.5194/egusphere-egu24-11556, 2024.

EGU24-11612 | Posters on site | GM6.4

Reconstructing Proterozoic Planforms and Channel Dynamics: New insights from the 1.2 Ga Stoer Group, NW Scotland 

Alex Whittaker, Jeff Valenza, Vamsi Ganti, Jonah McLeod, and Amanda Wild

A fundamental shift in fluvial architecture is often argued to coincide with the evolution of terrestrial plants in the Silurian period. This shift away from “sheet-braided” conditions has traditionally been attributed to the influence of vegetation on river geometry and planform, resulting in Earth’s first single-threaded rivers. However, recent paleohydraulic reconstructions of Proterozoic rivers suggest that rivers of this time commonly attained aspect ratios and slopes similar to modern meandering and anastomosing rivers. At the same time, a wider range of channel planforms is increasingly recognised for pre-Silurian strata, although these interpretations have resulted from varied methodologies. Thus, a consistent and multi-faceted approach, applied to a series of fluvial successions, is needed to develop a unified model of pre-vegetation fluvial morphodynamics. Here, we present field observations and paleohydraulic reconstructions of fluvial strata from the exceptionally well-preserved Mesoproterozoic (1.2-1 Ga) Stoer Group located in NW Scotland. These strata host a range of fluvial architectures, from low aspect-ratio channel bodies isolated within muddy floodplain sediments, to amalgamated channel facies forming apparent “sheet-braided” successions with high sand/mud ratios. Reconstructions and bar-dune orientations from the Clachtoll, Bay of Stoer, and Meall Dearg Formations of the Stoer Group reveal a range of channel morphologies, including meandering, wandering, and braided planforms. Furthermore, we show that mud, even in relatively low volumes, was capable of providing sufficient cohesion to foster single-threaded planforms. We propose that evolving channel kinematics post the greening of the continents was as important as changing planform for determining the fluvial architectures we see preserved in the rock record.

How to cite: Whittaker, A., Valenza, J., Ganti, V., McLeod, J., and Wild, A.: Reconstructing Proterozoic Planforms and Channel Dynamics: New insights from the 1.2 Ga Stoer Group, NW Scotland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11612, https://doi.org/10.5194/egusphere-egu24-11612, 2024.

EGU24-11979 | Posters on site | GM6.4

Chemical analyses of surficial covers associated with alluvial fans in the western state of Bahia, Brazil 

Artur Magalhães Brito, Tania Augusto da Silva Santos, Icaro Gabriel Lima Machado, João Pedro Bedendo, Emanuelly Cristina Leal Silva, José João Lelis Leal Souza, and André de Oliveira Souza

This work aimed to present partial results of chemical analyses conducted on surficial cover samples collected in alluvial fans located in the lower course of the Fêmeas River, in the Western region of Bahia, Brazil. This region is characterized by a sub-humid climate with two well-defined seasons: a rainy season (November to April) and a dry season (May to October). The hypothesis of this study considers that the deposits exhibit erosive-depositional discontinuities with different values of potassium (K) and sodium (Na), which could indicate the influence of complex morphodynamic processes throughout the Holocene. Therefore, the amounts of K and Na in different layers identified in the field and confirmed through laboratory textural analyses were measured. The analysis of these two cations allows for the possibility to infer a relative geochronology considering different exposures of the layers to weathering. The samples were collected at three sites on the left bank of the Rio das Fêmeas (LQME4; LQME5; LQME6). In LQME4, the results showed high potassium and sodium content at 20-30 cm (K=358 mg/dm³, Na=36.73 mg/dm³), 30-50 cm (K=347 mg/dm³, Na=36.73 mg/dm³), and 50-70 cm (K=307 mg/dm³, Na=53.38), except for the more superficial layer at 0-20 cm (K=8 mg/dm³, Na=16.08). This result suggests that the deeper layers underwent less weathering, while the low values of K and Na in the surface layer are possibly due to leaching from the runoff. With two layers, LQME5 presented high K and low Na values in the deeper layer of 20-60 cm (K=228 mg/dm³, Na=4.95 mg/dm³) contrasting with the more superficial layer at 0-20 cm (K=111 mg/dm³, Na=13.88 mg/dm³), where the K value decreases considerably while Na increases. The values in the most superficial layer are correlated with the modern sub-humid period that has resulted in lower runoff activity and, therefore, influencing mineral dissolution as indicated by the low Na value. The deeper layer suggests more humid periods characterized by lower K and higher Na values, indicating a more humid period resulting in more efficient mineral dissolution. In LQME6, six layers were analysed: 0-10 cm (K=195 mg/dm³, Na=11.07), 10-50 cm (K=147 mg/dm³, Na=11.49), 50-60 cm (K=69 mg/dm³, Na=13.72 mg/dm³), 60-75 cm (K=42 mg/dm³, Na=13.19), 75-85 cm (K=85 mg/dm³, Na=12.90 mg/dm³), 85-140 cm (K=87 mg/dm³, Na=16.30). The first two layers presented the highest K value in contrast to the other layers showing low values. LQME6 exhibits several discontinuities in K values, indicating that the upper layers underwent less weathering than the deepest ones. This research is being funded by the Bahia State Research Support Foundation (Grant 4341/2022).

How to cite: Brito, A. M., Santos, T. A. D. S., Machado, I. G. L., Bedendo, J. P., Silva, E. C. L., Souza, J. J. L. L., and Souza, A. D. O.: Chemical analyses of surficial covers associated with alluvial fans in the western state of Bahia, Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11979, https://doi.org/10.5194/egusphere-egu24-11979, 2024.

EGU24-12448 | ECS | Posters on site | GM6.4

Anthropogenic stratigraphic signals downstream a metropolis:Extracting Vienna’s signature from Danube river plain archives  

Diana Hatzenbühler, Michael Weißl, Christian Baumgartner, Karin Hain, Alexander Hubmer, Andreas Lang, and Michael Wagreich

The Anthropocene describes a potential new chronostratigraphic unit of the Geological Time Scale of intensified anthropogenic influence on environmental and geological processes, leaving traces in geological archives. Even though this human impact can be seen on a global scale, regional studies characterizing the scope and growth of anthropogenic influence, are scarce, especially for urban or peri-urban environments.

In this study, we investigate the anthropogenic impact of the metropolis Vienna on its peri-urban environment and the potential base of the Anthropocene epoch in the 1950s CE by applying sedimentological and geochemical methods.

The human influence in urban sedimentary archives of Vienna has already been detected in previous studies by Wagreich et al. (2022) using artificial isotopes and trace metals as Anthropocene stratigraphic markers on urban coarse artificial ground. The study area is set downstream of Vienna, in the National Park Donau-Auen, where direct human intervention into the archived Danube river sediments is currently nil. These river sediments represent an ‘Urban Anthropocene Field Lab’ to trace and quantify the human stratigraphic fingerprint and to search for potential markers and correlations to proposed GSSP Golden Spikes of the Anthropocene.

Within the proximal flood plain sediments of the Danube, i.e. erosional profiles and sediment cores, sedimentological, geochronological and chemostratigraphic markers are applied to characterize and date the anthropogenic strata in this area. First observations indicate three periods of distinct sedimentation patterns, potentially corresponding to the natural state prior to significant human intervention, the river system’s reaction to the first extensive river channelization in the 1870s CE, and it’s following response to the construction of hydropower stations (1956-1998 CE) and second river regulation (1990s). The lowermost section is characterised by clay and organic rich thin layers (few cm to mm) being suddenly replaced by alternating silt and sand packages of 5 to 20 cm beds. The uppermost silt to fine-sand dominated section is massive and shows almost not sediment structures, unlike the other sections, and exhibits a uniform light grey colour distinct from the light beige and dark brown colour of the underlying deposits.

The archive of natural Danube deposits is further analysed for artificial radiogenic isotopes, trace metals, and (micro-)plastics with the aim (i) to disentangle the anthropogenic fingerprint of Vienna from the sediment and characterise the interplay between upstream human interventions and local river dynamics, (ii) to identify and evaluate the proposed Holocene-Anthropocene geological boundary around 1950 CE, and (iii) to evaluate markers for the Anthropocene and a potential correlative stratigraphic reference section downstream of Vienna.

 

Reference:  
Wagreich, M., et al. 2022. The Anthropocene Review 10, 316–329.

How to cite: Hatzenbühler, D., Weißl, M., Baumgartner, C., Hain, K., Hubmer, A., Lang, A., and Wagreich, M.: Anthropogenic stratigraphic signals downstream a metropolis:Extracting Vienna’s signature from Danube river plain archives , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12448, https://doi.org/10.5194/egusphere-egu24-12448, 2024.

EGU24-16308 | Orals | GM6.4

Glacial-Holocene variability in sediment accumulation and erosion along submarine blind canyons: a case study from Eastern Mediterranean Sea  

Oded Katz, Naomi Moshe, Adi Torfstein, Mor Kanari, Pere Masque, and Orit Hyams-Kaphzan

Submarine canyons serve as important sediment transport conduits from littoral zones to the deep sea, with strong impacts on the sedimentation patterns in marginal areas of the ocean. Here, we present a study of the geological history and the recent activity of the Nahariya submarine canyon, the longest of a system of ~15 small blind canyons located in the eastern Mediterranean Sea, offshore Israel. Two piston cores retrieved from the middle and outlet of the canyon, at 650 m and 915 m water depth, respectively, were the focus of a multi-proxy study aiming to characterize sediment transport and deposition along the canyon during the Last Glacial and up to the present.

Both cores reveal a sequence of homogenous sediment of late last glacial age, which are capped by an unconformity overlying by fine laminated sediment dated to the last ~200 years. Thus, the deglacial and most of the Holocene intervals are absent from the record. Evidence for down canyon sediment transport are abundant and include a 70 cm interval of mud clasts with disordered glacial ages that appears immediately below the hiatus, as well as broken calcareous shells of dead benthic foraminiferal species of shallow marine habitats, which are abundant throughout both cores. Similarly, shelf-derived living benthic foraminiferal species were found in the core-tops, indicating that active sediment transport persists along this canyon today.

We conclude that the history of Nahariya submarine canyon includes a period of sediment accumulation that lasted until the last deglaciation. Thereafter, the canyon was dominated by an erosive regime that persisted throughout the Holocene. Sediment accumulation resumed ~200 years ago. We suggest that the recent resumption of sediment-accumulation is a result of anthropogenic amplification of on-land soil erosion accompanied by a wet period that persisted in the region and enhanced land to sea sediment transport.

How to cite: Katz, O., Moshe, N., Torfstein, A., Kanari, M., Masque, P., and Hyams-Kaphzan, O.: Glacial-Holocene variability in sediment accumulation and erosion along submarine blind canyons: a case study from Eastern Mediterranean Sea , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16308, https://doi.org/10.5194/egusphere-egu24-16308, 2024.

EGU24-17622 | Orals | GM6.4

From outcrop to spectrum 

Nils Keno Lünsdorf, Jan Ontje Lünsdorf, Gábor Újvári, István Dunkl, Lukas Wolfram, Adrian Hobrecht, Lothar Laake, and Hilmar von Eynatten

Reconstructing source to sink relationships or the origin of sediments and sedimentary rocks is the main goal of sedimentary provenance analysis. Several processes alter the source signal during transport and deposition and the extraction of the initial provenance signal is usually realized by combination of multiple single grain methods determining mineralogy, chemical composition or radiometric ages. However, such methods are mostly applied to sand-sized sediments or sedimentary rocks, while finer grained material is usually analyzed by whole-rock geochemical means and seldom by single-grain methods. Considering the abundance of fine-grained sedimentary archives and that short lived climatic signals are frequently encoded in such archives (e.g. loess, varves, etc.), a strong need for single-grain, multi-method analyses of silt-sized sediments is obvious.

Therefore, we developed a highly automated approach to modal mineralogy of silt-sized sediments and sedimentary rocks based on image segmentation and object detection capabilities of machine learning methods, which allows for correlative analysis (e.g. optical microscopy, Raman spectroscopy, SEM, EPMA, LA-ICP-MS) and increased sample throughput.

To test if our approach is feasible for silt-sized sediments, we sampled three loess-paleosol-sequences (LPS) of similar age and from different loess domains. Based on heavy mineral compositional data and zircon U-Pb age distributions the LPSs can readily be differentiated, verifying the feasibility of our approach. Consequently, we hypothesize that this novel multi-method, high-throughput data acquisition within a highly automated workflow will allow for hitherto unprecedented spatial and temporal resolution as well as statistical significance of provenance information, potentially enabling new research pathways in sedimentary provenance analysis.

How to cite: Lünsdorf, N. K., Lünsdorf, J. O., Újvári, G., Dunkl, I., Wolfram, L., Hobrecht, A., Laake, L., and von Eynatten, H.: From outcrop to spectrum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17622, https://doi.org/10.5194/egusphere-egu24-17622, 2024.

EGU24-17742 * | Orals | GM6.4 | Highlight

Landscape evolution on early Mars: a look inside a martian fan system 

Sanjeev Gupta, Kathryn Stack Morgan, Nicolas Mangold, Elizabeth Ives, Samantha Gwizd, Gwénaël Caravaca, Rebecca Williams, Robert Barnes, Nicolas Randazzo, Bryony Horgan, Kirsten Siebach, Christian Tate, Jorge Núñez, Steven Sholes, Linda Kah, Gerhard Paar, Justin Maki, and Jim Bell III

The modern surface of Mars does not sustain liquid water, however relict landforms observed on orbital images provide strong evidence of past aqueous activity. Nevertheless on-the-ground analysis of sedimentary strata are required to robustly characterise the specific nature of early Mars palaeoenvironments. The Mars 2020 Perseverance rover is exploring a prominent sedimentary fan deposit at the western margin of Jezero crater – the Western fan – which has been interpreted to be an river delta that prograded into an ancient lake basin during the Late Noachian-Early Hesperian epochs on Mars (~3.6-3.8 Ga). Perseverance’s traverse across the fan in 2022-2023 provides a remarkable window into a fossilised sediment routing system on Mars with potential to understand how water and sediment were distributed across a Martian landscape under a markedly different climate to present day. Here we use the rover’s Mastcam-Z cameras to characterise sedimentary geometries in a distal to proximal transect across the western fan and reconstruct sediment dynamics on the Western fan and infer past environmental change. The distal reaches of the preserved fan show a sedimentary succession that records a transition from distal alluvial fan into lacustrine and subsequently foreset delta deposits. This succession records the initiation of a martian lake system and lake level rise, though the delta stratal geometries suggest deposition during episodes of lake level fall. In the medial sector of the upper exhumed portion of the fan, complex stratal geometries are observed with a variety of scenarios for palaeoenvironmental interactions possible. In particular, the presence of large-scale foreset units preserved in this ‘mid-fan’ sector possibly suggests complex deltaic interfingering with fluvial strata during lake level fluctuations. In more proximal and stratigraphically higher (and hence younger) sectors of the fan, we observe strata deposited by progradation of fluvial systems culminating in a sequence of rounded boulder-containing deposits that signal transition to a routing system characterised by high discharges. Misquoting Shakira “the sediments don’t lie”; they record a history of sustained water transport and habitability on early Mars.

How to cite: Gupta, S., Stack Morgan, K., Mangold, N., Ives, E., Gwizd, S., Caravaca, G., Williams, R., Barnes, R., Randazzo, N., Horgan, B., Siebach, K., Tate, C., Núñez, J., Sholes, S., Kah, L., Paar, G., Maki, J., and Bell III, J.: Landscape evolution on early Mars: a look inside a martian fan system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17742, https://doi.org/10.5194/egusphere-egu24-17742, 2024.

EGU24-63 | ECS | PICO | TS5.2

Harmonic Dynamic of the Earth 

Xianwu Xin

The Harmonic Motion Phenomenon of the Earth is introduced through Experiments: Under the Combined Action of Tidal Force and the Earth's Rotation, Continental Unit Body Segments, like Caterpillars, actively crawl westward on the Mantle. Based on the Force Analysis of the Earth Motion Process and the Generalized Hooke's Law, the Harmonic Motion Equation and the Crustal Motion Equation of the Earth are derived, also the Conversion Equation of Continental Drift Datum has been derived. The Velocity Field of Continent Latitudinal Movement is calculated, and compared with the Measured Value of ITRF2000 station. From the Perspective of Kinematics, it is proved that the Harmonic Motion of the Earth is the Basic Dynamic Mechanism of the crust and inside of the Earth Movement. The Degree of Dominance which this Dynamic Process to Continental Drift is 72% to 97.4%. It's Energy comes from the Rotation Energy of the Earth. Using the results of Motion Calculation to was reconstructed the Proto Ancient Continent, that was it moment of started cracked at before 250 million years. In addition, the Driving Force Equation of the Earth’s Harmonic Motion is derived. Discussed the Driving Force accumulation process and the formation mechanism of Earthquake: The Thrust of the Rock Stratum to the Hindered Portion slowly increases with the Creep between stratus and the Successive Compression each time it from Peak Point to Valley Point. Continuously increase the Elevation and Area of the Compression Zone. When the Driving Forces Accumulation reaches the Limit of the Strength of the Hindered Rock Stratum, sudden movement or Fracture Occurs, and an Earthquake formation. Earthquakes are a Process of Concentrated Energy Release. In High-Temperature and High-Pressure Areas within 700km underground, when Earthquakes, some Rocks melt to form Magma, and driven by Harmonic Motion, enriches westward along Rock Fractures and enters the Ocean Ridges Bottoms and the Below of the Volcano. The Magma of Below the Volcano erupts from the Earth's Surface after increasing Pressure. The Magma at the Bottom of the Ocean Ridge is driven by the Footpath Board Effect and moves upwards along the Cracks, and Condensed on the Surface of the Sidewall, when change the Gaps of the Cracks along with the Ocean Floor Undulating, the Ocean Floor on Both sides of the Ocean Ridge is pushed apart from each other. This kind of process of Ocean Floor Fluctuate Spreading leads to Gradual wear and tear of the Ocean Floor, Ultimately Subducting beneath Land or trenches and returning to the Mantle. In Passive Mantle Convection and Ocean Floor Fluctuate Spreading, the Driven Force of Magma flow is provide by the Earth's Rotation through Fluctuate Processes, magma does not output Power. At last, according to the Driving Force Equation of Earth‘s Harmonic Motion, the Energy Conversion Equation is given. The Total Power of Earth‘s Harmonic Motion is calculated, and compared with the Relevant Measured Values. It is further proved from the Perspective of Dynamics and Energy Conversion: The Harmonic Dynamic Proces of the Earth is the Basic Dynamical Proces of Tectonic Movement.

How to cite: Xin, X.: Harmonic Dynamic of the Earth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-63, https://doi.org/10.5194/egusphere-egu24-63, 2024.

Fold-and-thrust belts (FTBs) evolve over a mechanically weak basal décollement that separates overlying intensely deformed rocks from the underlying less deformed or undeformed rocks. Although fold-and-thrust belts are often considered laterally cylindrical in nature, a closer inspection reveals remarkable variations in structural style (e.g., fold geometry) both along and across the strike of mountain belts. Using crustal scale thin-sheet laboratory experiments, this study focuses on the role of laterally varying coupling strength of the basal décollement on the evolution of structural styles in natural FTBs. In this study, we used a rectangular slab of silicon putty, a linear viscous material, of uniform thickness in all experiments to simulate the crustal section and the models were deformed at a uniform convergence velocity of ~7.649 × 10-5 ms-1. Analyses of experimental results show remarkable changes in the wedge growth with the introduction of along strike variations in décollement strength. The segment of the deforming wedge over weakly coupled décollement propagates at a faster rate towards the frontal direction compared to the laterally continuous segment over a strongly coupled décollement, leading to an overall sinuous geometry of the deformation front. In contrast, an approximately linear deformation front represents a condition of uniform along-strike coupling strength at the basal décollement. Based on our experimental results, we argue that the broad arcuation of the mountain front along the eastern margin of the Zagros fold-thrust belt (i.e., Fars arc region) might have resulted due to along strike variations in the décollement strength, while the occurrence of a linear deformation front from the central to western margin of the fold-and-thrust belt represents a segment of the wedge with a uniform coupling strength at the basal décollement. Our experimental results can be carefully used to explain the cause of strike-wise segmentation of tectonic processes in orogenic belts, variations in topography and earthquake activities.   

How to cite: Roy, S., Willingshofer, E., and Bose, S.: Influence of lateral variations of décollement strength on the structure of orogenic wedges: insights from experimental viscous wedge models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3310, https://doi.org/10.5194/egusphere-egu24-3310, 2024.

With the wide application of high-quality three-dimensional (3-D) seismic volumes in hydrocarbon exploration, it has been found that a special type of fault system, i.e., conjugate strike-slip fault system, is often developed in the Cratonic basins (e.g., Tarim Basin, Sichuan Basin, and Ordos Basin in China). They not only can directly indicate the principal stress direction, but also play a crucial role in controlling the transport and formation of hydrocarbons in the basin. Analysis of 3-D seismic data revealed that the Tarim Basin exhibited typical X-shaped (symmetrical) and asymmetrical (two sets of faults differing greatly in number) conjugate strike-slip fault systems. However, there is a lack of analogue models on the geometries and progressive evolution of conjugate strike-slip faults, as well as a poor understanding of the mechanisms of asymmetric conjugate strike-slip fault systems. Additionally, previous experiments have not been compared with such natural examples.

Based on the structural analysis of strike-slip faults in the Tarim Basin using seismic reflection data, we used three sets of symmetric (rectangular shape) and two sets of asymmetric (parallelogram shape) rubber basement models to investigate the geometries and progressive evolution of conjugate strike-slip faults. In this study, our research successfully modelled the kinematic and geometric evolution of different types of conjugate strike-slip fault systems, and found that they have the same acute angle and that the direction of their angular bisectors is parallel to the direction of contraction. In symmetric models, we observed the development of numerous typical X-shaped conjugate strike-slip faults were developed. Conversely, the development of two sets of faults in the asymmetric models showed an asymmetry, i.e., one set of faults was more obviously developed than the other, and with the degree of asymmetry increased, the asymmetry was even more obvious. Furthermore, we analysed the stress state of the models using the Mohr space and inferred that the stress state of the model changed from the strike-slip in the early stages to the extension in the later stages.

We proposed two synoptic models, namely, the symmetric conjugate strike-slip fault system (SCSFS) model and the asymmetric conjugate strike-slip fault system (ACSFS) model, for conjugate strike-slip fault systems based on the results of the different models. The models and experimental results were compared with natural examples of the two sets of strike-slip fault systems in the Tabei uplift in China’s Tarim Basin, which exhibited many strong similarities in their structural geometries, and they also provided further insight into the mechanisms of strike-slip faults in the Tabei uplift. These synoptic models proposed based on the analogue models may provide useful templates for the seismic interpretation and mechanism of different types of conjugate strike-slip fault systems in nature and for inferring the orientation of the maximum principal stress.

How to cite: Xiao, K. and Tong, H.: Analogue modelling of conjugate strike-slip faults in the Cratonic basin: A case from the Tarim Basin, NW China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3751, https://doi.org/10.5194/egusphere-egu24-3751, 2024.

Fault evolution is influenced by multiple factors, including the reactivation of pre-existing structures, stress transmission within ductile detachment layers, and the growth, interaction, and connection of newly formed fault segments. In the same stress field, displacement vectors of fault strikes, dip-slip vectors, and subtle fractures accommodate strain distributed everywhere. This study employs PIV analysis and model reconstruction to simulate oblique extensional fault systems formed at four different angles. Simulation modelling indicates that oblique extensional reactivation of pre-existing structures controls the linear arrangement of fault segments in the overlying strata. Arcuate faults can be classified into linear master fault segments controlled by pre-existing structures, curved splay faults in termination zones, and normal fault segments responding to regional stress fields. Along-strike displacement is regulated by linear segments within the master strike-slip fault, while progressive bending of splay faults, relay ramps' dislocation, and inclined displacements are regulated by relay ramps within the overlap zone. Small-angle (15°) oblique extension favours the formation of fault segments with distinct step-like features, leading to additional relay ramps. In contrast, high-angle (60°) oblique extension often results in the development of more continuous fault segments. As faults continuously evolve, new fault segments tend to deviate from the control of pre-existing structures, concentrating more on the development of planar and continuous master faults. Finally, we compared the established model with the transtensional fault system within the intraplate rift system in eastern China, demonstrating that the oblique extension angle controls the composite characteristics of the overlying strata faults.

How to cite: Wang, Y. and Yu, F.: The Linkage Evolution of Strike-Slip Faults with Normal Faults—Insights from Analogue Modelling at Various Oblique Extension., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4813, https://doi.org/10.5194/egusphere-egu24-4813, 2024.

EGU24-6667 | ECS | PICO | TS5.2

Decoding the extensional phase of the Atlas system: Unraveling Crustal Stretching during rifting:  

Mouad Ankach, Mohamed Gouiza, and Khalid Amrouch

The Atlas fold and thrust belt extend from the Atlantic rifted margin of Morocco to Tunisia over a distance of 2500km. Before its inversion in the Cenozoic to the present, the Atlas system evolved initially as a rift basin that opened simultaneously with the Atlantic rift in the west and the Tethys in the north, during the upper Triassic-Jurassic period.

The Western High Atlas is believed to be influenced by the Atlantic Ocean (also known as the Atlantic domain), where the Triassic to Early Jurassic strata are considered to be syn-rift, while the Middle Jurassic to Cretaceous deposits are labelled as post-rift. In contrast, the Marrakech High Atlas (MHA), Central High Atlas (CHA), Middle Atlas (MA), and the Eastern High Atlas (EHA) are assumed to be influenced by the Tethys Ocean (also known as Tethyan domain), where the Triassic to Jurassic sediments are considered to be syn-rift. This implies that the Mesozoic rifting along the Atlas was diachronous, making it difficult to determine the exact timing and kinematic of crustal stretching. Constraining the extensional phases in the Atlas system is crucial for understanding how the Atlas crust was stretched and thinned. Our work aims to quantify the magnitude and regional kinematic of stretching in the Atlas system using various methods, namely, thickness variation method, subsidence analysis and palinspatic reconstruction of 2D cross-sections.

Our preliminary results indicate that the maximum stretching factor (beta factor) in the Atlas is β = 1.25; and that crustal thinning did not exceed 20%, based on tectonic subsidence analysis. While the palinspatic restoration suggest that the Moroccan Atlas system underwent approximately a uniform stretching with β = 1.11 in EHA (Midelt-Errachidia area), β = 1.08 in CHA (Imilchil area), and β = 1.12 in the East Marrakech High Atlas (EMHA: Demnat area). These values indicate that the Moroccan Atlas crustal thickness has been thinned by 9% in EHA, 8% in CHA, and 11% in EMHA. In addition, the geological context of the High and Middle Atlas regions, where the estimated shortening is reported to be less than 20%, the stretching factor (β) was calculated based on the crust thickness. The initial crustal thickness (IC) of the Meseta block, which constitutes one of the Atlasic rift shoulders, considered an undeformed area, served as a reference. Accounting for the observed shortening, the final crustal thickness was deduced by subtracting the reported shortening value representing 7.8 km from the observed crustal thickness (39 km), resulting in a β value of 1.25, which is consistent with the result obtained from the subsidence analysis.

Keywords: Atlas system, extension, stretching factor, Thinning factor,

 

 

 

How to cite: Ankach, M., Gouiza, M., and Amrouch, K.: Decoding the extensional phase of the Atlas system: Unraveling Crustal Stretching during rifting: , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6667, https://doi.org/10.5194/egusphere-egu24-6667, 2024.

EGU24-6869 | ECS | PICO | TS5.2 | Highlight

Multiscale, multisensor analysis of scaled seismotectonic models: Bridging the Gap Between Laboratory and Nature through Machine Learning 

Giacomo Mastella, Fabio Corbi, Jonathan Bedford, Elvira Latypova, Federico Pignalberi, Marco Scuderi, and Francesca Funiciello

Despite considerable progress in monitoring natural subduction zones, key aspects of megathrust seismicity remain puzzling, mainly due to the temporally incomplete and spatially fragmented available record. Scaled seismotectonic models yield valuable insights by spontaneously creating multiple stick-slip cycles in controlled, downscaled three-dimensional laboratory replicas. Here we report recent progress in analog modeling of the megathrust seismicity, particularly focusing on a meters-scale elasto-plastic model featuring a frictionally segmented, granular fault that mimics the subduction channel at natural subduction zones. We showcase how by employing analog materials under low-stress conditions, the potentialities of monitoring can be maximized using three diverse techniques: 1)  Precise monitoring of surface spatial deformation over time is achieved through digital image correlation techniques, mirroring a uniformly distributed dense geodetic network spanning land to trench in real subduction zones. 2) A Micro-Electro-Mechanical (MEMS) accelerometric network, emulating a seismic network, captures seismic wave propagation at the model surface. 3) Embedded piezoelectric sensors within the granular analog fault capture near-field acoustic signatures of frictional instabilities. These diverse monitoring techniques allow for investigating the consistency between continuous seismic activity and surface deformation data, offering insight into both micro and macroscopic features of analog seismic cycles. At the macroscopic level, the models' frictional behavior can be numerically reproduced via rate and state numerical simulations, considering earthquake fault slip as a nonlinear dynamical process dominated by a single slip plane. At smaller scales, the model accounts for complexities in fault slip emerging from grain interactions, reflecting nonlinearities that arise when considering faults as distributed three-dimensional volumes. These fundamental attributes, coupled with their capacity to create extensive catalogs of small labquakes, make scaled seismotectonic models exceptional apparati for employing Machine Learning (ML) in comprehending multi-scale spatiotemporal seismic processes. Cutting-edge Deep Learning methods are employed to predict the spatiotemporal evolution of surface deformation, where regression algorithms not only forecast timing but also the propagation and magnitude of analog earthquakes across diverse spatiotemporal scales. Given that one of the monitoring systems used in seismotectonic analog models mimics a geodetic-like network in nature (GNSS data-Global Navigation Satellite Systems), an attempt to generalize the promising outcomes achieved in the laboratory to natural subduction faults is proposed.  Such promising avenues emphasize the potential for ML to bridge the gap between laboratory experiments and real-world seismic events. These initial findings, combined with advancements in the instrumentation of fault laboratories in nature and expanding data reservoirs, reinforce the belief that ML can significantly augment our understanding of the multiscale behaviors of natural faults.

How to cite: Mastella, G., Corbi, F., Bedford, J., Latypova, E., Pignalberi, F., Scuderi, M., and Funiciello, F.: Multiscale, multisensor analysis of scaled seismotectonic models: Bridging the Gap Between Laboratory and Nature through Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6869, https://doi.org/10.5194/egusphere-egu24-6869, 2024.

EGU24-7785 | ECS | PICO | TS5.2

Haromonic Curvature and Bedding Uncertainty Across Scales 

David Nathan, Mario Zelic, Eun-Jung Holden, Daniel Wedge, and Christopher Gonzalez

Observations of geological structures are often made at different scales and often can cross multple orders of magnitude. This attribute of scale though is often not explicitly incorporated into the workflow of geological modeling and is usually treated as data preparation or sampling bias. The spectral properties of the discrete Laplacian operator, when applied to reconstructed surfaces from implicit modeling though offer a potential means of bridging this gap, when also combined with appropriate directional statistical anaysis. We present an example of how bedding orientation measurements from a 1:5000 scale surface map and drillhole bedding orientation picks from borehole televiewer images can be integrated using the manifold harmonics of the Laplacian operator and a mixture of von-Mises Fisher probability distributions. This provides automated insights for sampling for modeling and also possible kinematic and tectonics processes.

How to cite: Nathan, D., Zelic, M., Holden, E.-J., Wedge, D., and Gonzalez, C.: Haromonic Curvature and Bedding Uncertainty Across Scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7785, https://doi.org/10.5194/egusphere-egu24-7785, 2024.

This study investigates a fold-and-thrust belt (FTB) beneath the South Yellow Sea Basin, a noteworthy petroleum exploration target, featuring a basement high and a detachment layer. In the central basin, magnetic anomalies reveal the development of the basement high. Seismic reflection data, in conjunction with drilling information, disclose the presence of the Lower Silurian Gaojiabian Formation, exceeding ~500 m, acting as a low-cohesion detachment layer. However, the impact of these features on regional structures and the resulting hydrocarbon preservation conditions remains uncertain. This study explores the kinematic characteristics and deformation localization associated with the basement high and intermediate detachment using four sandbox models and particle velocity analysis within the FTB framework. Model 1, the reference, utilized pure quartz sand without either feature. Model 2 examined the role of the intermediate detachment using glass microbeads, revealing a limited effect in generating typical thin-skinned FTB. Model 3 considered the basement high and found that it strongly influenced the deformation regime of the wedge. Model 4 examined both features and suggested their combined influence on FTB deformation processes. In Model 2, lacking a pre-existing basement high, the intermediate detachment did not contribute to FTB deformation. In Model 3, lacking an intermediate detachment, deformation propagated along the surface of the basement high upon reaching its edge. In Model 4, shortening propagated upward along the edge of the basement high and then into the intermediate detachment, producing comparable structural geometry to the prototype, including both thick- and thin-skinned FTBs in nature. The results indicate that in the central South Yellow Sea Basin, structural layers between the basement high and detachment are likely to experience weak deformation; thus, favorable hydrocarbon preservation conditions can be anticipated in this region. This study holds significant importance in guiding future petroleum exploration efforts in the central South Yellow Sea Basin.

How to cite: Zhang, P., Fu, Y., and Yan, B.:  Influence of Basement High and Detachment on the Kinematics of a Fold-and-Thrust Belt in the Central South Yellow Sea Basin with Implications for Hydrocarbon Preservation: Insights from Analog Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8859, https://doi.org/10.5194/egusphere-egu24-8859, 2024.

EGU24-10540 | ECS | PICO | TS5.2

Proto-ophiolite serpentinization may influence ophiolite emplacement: Insights from numerical models  

Afonso Gomes, Filipe Rosas, Nicolas Riel, João Duarte, Wouter P. Schellart, and Jaime Almeida

Ophiolites are exposed remnants of oceanic lithosphere that are critical to our understanding of the structure, composition, and evolution of oceanic plates.

Some ophiolites (e.g., some Tethyan-type ophiolites) originate in the oceanic forearc of an intra-oceanic subduction system (i.e., in the overriding plate). If the trailing edge of the subducting oceanic lithosphere is connected to a continental passive margin, then that passive margin may also be subducted (beneath the forearc and proto-ophiolite) once all the oceanic lithosphere is “consumed” at the trench. The subduction of the continental passive margin means that a buoyant continental crust will underthrust the oceanic forearc (i.e., proto-ophiolite). This crust goes through a burial-exhumation cycle, and as it exhumes it can drag and detach the tip of the overlaying oceanic forearc, creating an ophiolite klippe. The exhumation-emplacement process is, however, still not fully understood, particularly regarding the constraints imposed by the forearc itself. For example, the detachment of the tip of the forearc (ophiolite) from the remainder of the plate should, at least in part, be controlled by the mechanical properties of the forearc (i.e., presumably the tip of a “weak” forearc will detach more easily than the tip of a “strong” forearc).

Present-day intra-oceanic subduction forearcs (i.e., present-day model-types for Tethyan-type ophiolites) experience significant chemical alteration induced by the circulation of metamorphic fluids originating from the dehydration of the underlying subducting plate. This chemical alteration occurs mostly in the form of serpentinization of forearc peridotites, leading to a substantial weakening of the forearc lithospheric mantle. The circulation of these fluids, and hence the serpentinization process, is thought to occur primarily along preexisting deeply rooted fault systems, further weakening these strain-localizing structures, although some diffuse alteration probably also occurs. It is then reasonable to assume that the paleo forearcs that originated Tethyan-type ophiolites were also subject to these chemical and mechanical alterations, which are then expected to have affected the ophiolite emplacement process.  

Here we present novel 2D and 3D dynamic numerical models that investigate the role of forearc weakening on ophiolite emplacement processes. Specifically, we test different mechanical weakening patterns, i.e., localized (serpentinized faults) vs homogeneous (diffuse serpentinization) weakening.

Preliminary results suggest that prior serpentinization of the forearc has a critical control on ophiolite emplacement. Furthermore, differing degrees of forearc serpentinization, as well as serpentinization distribution patterns, result in different tectonic regimes of ophiolite emplacement.

 

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020) and through scholarship SFRH/BD/146726/2019.

How to cite: Gomes, A., Rosas, F., Riel, N., Duarte, J., P. Schellart, W., and Almeida, J.: Proto-ophiolite serpentinization may influence ophiolite emplacement: Insights from numerical models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10540, https://doi.org/10.5194/egusphere-egu24-10540, 2024.

EGU24-12208 | PICO | TS5.2

Numerical and analogue modelling of boudinage under non-coaxial shear strain 

Filipe Rosas, Afonso Gomes, Jaime Almeida, João Duarte, Nicolas Riel, and Wouter Schellart

The recognition of different boudinage patterns is of key importance to the unravelling of the tectono-metamorphic evolution of different domains in different tectonic contexts and at different considered spatio-temporal scales.

The main reason for this is twofold: (1) Boudins tend to preserve the relic metamorphic conditions that characterize deformation prior to the one recorded by matrix fabrics and associated mineral associations. (2) Specially under shear deformation regimes, quarter-structure geometric patterns comprising rotated boudins and folded matrix planar fabrics, can be used to determine the shear sense of the later (sin-boudinage) deformation.

In the present work, we present preliminary numerical and analogue modelling results of boudinage, under non-coaxial (shear strain) deformation. We specifically investigate the potential influence of three main parameters on the genesis of different (boudins-folds) quarter structures patterns: i) the viscosity contrast between the boudin and the matrix; ii) the original position of the non-equidimensional boudin; and ii) the assumed (bulk) shear strain rate.

We proceed by presenting a preliminary comparison of our results with archetypical natural examples of boudinage, in different tectonic-structural contexts and at different scales, further illustrating the potential value of these type of structures in the unravelling of the deformation history in different situations.

Acknowledgements

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).

How to cite: Rosas, F., Gomes, A., Almeida, J., Duarte, J., Riel, N., and Schellart, W.: Numerical and analogue modelling of boudinage under non-coaxial shear strain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12208, https://doi.org/10.5194/egusphere-egu24-12208, 2024.

EGU24-12468 | ECS | PICO | TS5.2

Asthenospheric flow-driven lithospheric deformation in analogue models – a novel methodological approach and implications for natural systems  

Nemanja Krstekanic, Ernst Willingshofer, Antoine Auzemery, Liviu Matenco, and Jasper Smits

In subduction systems, asthenospheric flow, generated by subducting slabs, is considered as one of the key forces contributing to the deformation of the overlying lithosphere. Previous analogue modelling studies predominantly focused on understanding the kinematics and dynamics of subduction roll-back-driven asthenospheric flow, without looking at the influence of that flow on upper-plate deformation due to the modelling setups or methodological limitations. We developed a novel analogue modelling approach where gravity-driven asthenospheric flow represents the main driver for upper plate deformation. Volume-constant flow within the deformation box is achieved by an inlet-outlet system. In the models, we gradually increase the setup complexity from single-layer asthenosphere-only models to 4-layer asthenosphere-lithosphere models to test flow velocity distribution and its sensitivity to the outlet size, model thickness and rheological stratification of the model, as well as the transfer of deformation from the asthenosphere to the overlying lithosphere. Furthermore, we study the effects of the inherited lithospheric structures, such as weak zones representing old sutures, on deformation transfer. The results are compared with the Pannonian-Carpathians system of south-eastern Europe, where the large Pannonian back-arc basin formed during the Miocene retreat of the Carpathians slab.

For the methodological approach, the results show that asthenospheric flow can be fully controlled by the inlet-outlet system by adjusting the outlet size, which provides an efficient mechanism for the deformation of the overlying mechanically stratified lithosphere. The models also demonstrate that the back-arc extension is initiated farther away from the asthenospheric flow origin (i.e., the outlet in the models or slab-roll back in nature). The subsequent deformation propagates in two directions, towards the flow origin, and farther away from it, both directions controlled by the shape of an indenter located laterally to the subduction zone. Most of the back-arc extension and the lithospheric thinning are accommodated in the area farther to the “slab” due to the strain shadow effect of the indenter. The indenter also contributes significantly to the strain partitioning in its closer proximity where a complex pattern of bi-directional extension, transtensional, strike-slip and transpressional deformation forms. The weak zones accommodate the onset of back-arc extension or act as transfer zones between areas with different extension rates, depending on their orientation relative to the asthenospheric flow. These models show several similarities with the Pannonian-Carpathians system, where most of the Pannonian lithospheric thinning is located at a significant distance from the subducting Carpathians slab, bypassing the Transylvanian-Apuseni area. This extension started by reactivation of the Neotethys suture zone, while the Mid-Hungarian Fault zone transferred the deformation between areas of higher extension to the south and lower extension to the north. Furthermore, several triangular-shaped sub-basins within and at the margin of the Pannonian Basin are radially located around the Moesian NW corner, similar to our modelling results. The complex pattern of the bi-directional extension and strike-slip observed in the models were recorded by the Carpathians-Balkanides orocline in the vicinity of the Moesian indenter.

How to cite: Krstekanic, N., Willingshofer, E., Auzemery, A., Matenco, L., and Smits, J.: Asthenospheric flow-driven lithospheric deformation in analogue models – a novel methodological approach and implications for natural systems , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12468, https://doi.org/10.5194/egusphere-egu24-12468, 2024.

EGU24-13464 | ECS | PICO | TS5.2

A new geodynamic model of the Azores archipelago: preliminary results 

Jaime Almeida, João Duarte, Filipe Rosas, Rui Fernandes, Fernando Geraldes, Luis Carvalho, and Ricardo Ramalho

The Azores archipelago is an integral part of the Macaronesian geographic region (which also includes the volcanic archipelagos of Madeira, Selvagens, Canaries and Cape Verde). This region, located in the centre of Atlantic Ocean, has its individual islands spread around a triple junction, which has been suggested to affected by a plume-ridge interaction (Storch et al., 2020; Beier et al., 2022). One of the major questions surrounding its history concern the why/how the Terceira Rift (i.e., the NW-SE oriented connection between the mid-ocean ridge and the Gloria Fault Zone) was formed.

To explore this issue, we have run sets of 3D viscoelastoplastic models for the region using the state-of-the-art modelling code LaMEM (Kaus et al., 2016). As our objective was to evaluate how the geological data and the suggested evolution for the region fit geodynamic constraints. We based our numerical models on previously established evolutionary models for the region, such as the leaky transform model (Madeira and Ribeiro, 1990).

Preliminary results hint that the formation of the Terceira Rift could be formed as the result of a shift in the regional tectonic forcing, which we attribute to the collision between the Iberian and Eurasian plates. Furthermore, our results suggest that a strong rheological contrast in the region was required to ensure the localization of deformation. Models without this feature tended to maintain a simple E-W connection between the Gloria Fault Zone and the southern part of the mid-ocean ridge.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through projects GEMMA (https://doi.org/10.54499/PTDC/CTA-GEO/2083/2021) and national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).

 

References

Beier, C. et al. (2022) ‘The submarine Azores Plateau: Evidence for a waning mantle plume?’, Marine Geology, 451, p. 106858. Available at: https://doi.org/10.1016/j.margeo.2022.106858.

Kaus, B.J.P. et al. (2016) ‘Forward and Inverse Modelling of Lithospheric Deformation on Geological Timescales’, NIC Series, 48, pp. 978–3.

Luis, J.F. and Miranda, J.M. (2008) ‘Reevaluation of magnetic chrons in the North Atlantic between 35°N and 47°N: Implications for the formation of the Azores Triple Junction and associated plateau’, Journal of Geophysical Research: Solid Earth, 113(B10). Available at: https://doi.org/10.1029/2007JB005573.

Madeira, J. and Ribeiro, A. (1990) ‘Geodynamic models for the Azores triple junction: A contribution from tectonics’, Tectonophysics, 184(3–4), pp. 405–415. Available at: https://doi.org/10.1016/0040-1951(90)90452-E.

Storch, B. et al. (2020) ‘Rifting of the oceanic Azores Plateau with episodic volcanic activity’, Scientific Reports, 10(1), p. 19718. Available at: https://doi.org/10.1038/s41598-020-76691-1.

How to cite: Almeida, J., Duarte, J., Rosas, F., Fernandes, R., Geraldes, F., Carvalho, L., and Ramalho, R.: A new geodynamic model of the Azores archipelago: preliminary results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13464, https://doi.org/10.5194/egusphere-egu24-13464, 2024.

Eastern Sichuan fold belt, a prolific hydrocarbon province in China, shows the similar fold styles to the Swiss Jura Mountain fold belt, which’s therefore called as Jura-type fold by Chinese geologists. However, it’s still a matter of geologist’s debate on the formation mechanism of the eastern Sichuan fold belt.

To unravel how this type of fold trains form, a systematic scaled 2D contractional analogue experiments with composite materials were conducted. Silica-sand represents the overburden with added mica-flakes, and a stiff plasticine interlayer introducing different mechanical anisotropies. Viscous silicone rubber represents the salt detachment. The following 3 main issues have been investigated: 1) what type mechanical stratigraphy can form the fold train during lateral contraction; 2) what are the mutual interaction between faulting and folding during the formation process of detachment fold; 3)what are kinematics and its related strain distribution patterns for a detachment fold system.

The modelling results indicate that the presence of a stiff plasticine layer is the key perquisite for the formation of a concentric fold train for the following reasons: 1) it encourages the shortening to be periodically accommodated by sinusoidal-symmetric buckle folds at the inceptive folding stage; 2) it can keep the break-thrust ramps from being activated with further shorting delaying the development of faulted detachment folds at the later folding stage. As for silicone detachment, it mainly plays a role in the amplification of detachment folds via the redistribution of ductile material between the syncline and anticline domain.

DIC strain data show that the main sections of detachment fold-the limbs, especially in the forelimb, and the hinge are easily strained. More specifically, the normal faults and breakthrusts can form in the anticlinal hinge and limbs, respectively, when the detachment fold cannot be tightened any more. However, the strain is not easily accumulated in the syncline domain.

Our modelling result together with the latest interpretation of seismic reflection suggest that the eastern Sichuan fold belt is a result of faulted detachment folds, mainly controlled by the competence contrast within the overburden and the thickness of both the weak viscous detachment and strong brittle overburden.

Keywords: Eastern Sichuan Basin; Analogue modelling; DIC; Fold-thrust belt; Detachment fold

How to cite: Feng, G., Adam, J., Chen, S., and Wang, X.: Key controlling factors on the formation of Jura-type fold in eastern Sichuan Basin, South China: insights from analogue modelling with optical strain monitoring (Digital Image Correlation), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13637, https://doi.org/10.5194/egusphere-egu24-13637, 2024.

EGU24-13652 | ECS | PICO | TS5.2

Crust-mantle delamination enables continental subduction and flake tectonics: insights from numerical modelling 

Nuno Rodrigues, Filipe Rosas, Nicolas Riel, Jaime Almeida, Afonso Gomes, and João Duarte

Continental collision occurs when two continents are dragged towards each other by the pull of the attached subducting oceanic lithosphere. Previous geodynamic modeling studies of collisional systems focused on first-order processes (such as coupled/decoupled regimes, continental delamination, slab break-off dynamics) and regional or even local scale dynamics (e.g., exhumation of HP/UHP rocks, surface topography). However, continuous subduction of continental lithospheric mantle after the onset of collision and long-term dynamics of continental subduction remains poorly constrained. Long-term continental subduction bears major geodynamic implications for the evolution of past and present collision zones.

To this aim, we use the geodynamic code LaMEM to perform high-resolution (2048 × 512) 2D buoyancy-driven numerical models, coupled with phase diagrams to account for density changes, of continued continental subduction with conditions that favor flake tectonics. We investigate the role of lower crust rheology to assess which rheological scenarios allow continental flaking and, thus, continued subduction of continental lithospheric mantle.

Our preliminary results exhibit long-term continental subduction, due to decoupling of the lower crust from the subducting continental mantle and/or density changes. This separation allows the deformation to be transmitted onto the overriding plate, with the emplacement of the subducting plate crust onto the overriding plate spanning more than 350 km and lasting over 100 Myr.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), and through scholarship UI/BD/154679/2023.

How to cite: Rodrigues, N., Rosas, F., Riel, N., Almeida, J., Gomes, A., and Duarte, J.: Crust-mantle delamination enables continental subduction and flake tectonics: insights from numerical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13652, https://doi.org/10.5194/egusphere-egu24-13652, 2024.

The deformation associated with the evolution of fold-thrust tectonic (FTT) wedge has been in the focus of research due to their association with hydrocarbons resources. Analogue sandbox modelling has been proven to be useful in characterizing FTT wedge. However, it is less convenient to interpret the influence of complex boundary conditions and material rheological parameters and to derive the stress distribution pattern from the analogue models. Nonetheless, these challenges can be accomplished competently by means of an exact numerical equivalence of those analogue models. Therefore, we undertook a numerical replication of the analogue sand-box with an absolute identical set up. This makes the attempt unique from earlier approaches, where lengths, rheology, and/or cohesive strengths were likely varied for converging the solutions in codes. Here, propagation parallel profile of sandbox experiments is numerically modelled in a 2-dimensional (2D) space with a plain strain assumption. For simplicity, the models are devoid of complex geological phenomena such as isostasy, pore fluid pressure and surficial processes. The present model enforces an elastoplastic constitutive relationship having exactly same rheology as our sand-box model. The model comprises cover material resting over a rigid decollement with frictional interaction. The cover material is subjected to asymmetrical push from one end as in physical experiment. With the identical rheology, dimensions, and geometry our numerical model successfully produced comparable results with our physical sandbox models. The measured kinematic attributes of the wedge such as taper angle, wedge width, thrust spacing, displacement along thrust from our numerical model are found in good agreement both qualitatively and quantitively with their analogue counterparts. The dynamics of deformation has also been investigated by extracting the magnitudes of stresses from each node of the numerical mesh of the present models.  From the dynamic analysis, the spatial distribution of stresses revealed that within a deforming wedge all the stress parameters are maxed periodically at a certain distance away from the pushing end boundary. The position of maximum stress is found consistent with the zone localized failure. Monitoring the periodic peaks of stress approximate the location of failure, in return leading to measure the thrust spacing. Furthermore, empirical relationships for stress distribution within a collisional wedge have been successfully developed from the observed stress distribution patterns. With the help of these relationships, mathematical expressions were developed for predicting 2D curvature of a thrust plane within a tectonic wedge. 

How to cite: Behera, A. and Bhattacharjee, D.: The dynamics of fold-thrust tectonic wedge: An insight from impeccable simulation of Physical Sandbox Experiment with Finite Element Model., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14388, https://doi.org/10.5194/egusphere-egu24-14388, 2024.

EGU24-14511 | PICO | TS5.2

Machine learning reveals the width of fault damage zones in northeast Sichuan Basin, China 

Jingbo Zhang, Sixian Chen, and Zonghu Liao

Abstract

Accurate understanding and identification of faults architecture is crucial in seismic data interpretation and earthquake analysis, where fault slip surfaces may interact with damage rocks, forming damage zones with a width larger than hundred meters. We use machine learning (ML) to show 10 kinds of seismic attributes from a seismic survey could be applied in identification and quantification of fault damage zone in northeast Sichuan Basin, China. The results indicate: (1) Six seismic attributes provide highest contribution to the fault characterization, including root mean square amplitude attributes, azimuth angle attributes, reverse attributes, original attributes, chaotic body attributes and ant body attributes; (2) The application of SHAP (SHapley Additive exPlanations) algorithm improves the model's accuracy, as the loss value (Mean Square Error , MSE) of the test data is restored from 17.86% to 16.03%; (3) Width estimation from the kernel density estimation algorithm (KDE) show the fault damage zone ranges from 0.3 to 1.2 km. Our work provides new insights into the interpretation of fault architecture in the subsurface, and we argue the geometrical parameters of the fault damage zone is significant for understanding the evolution of fault and earthquake simulations.

Keywords:  Fault damage zone; Seismic interpretation; Machine learning (ML); Geometrical parameters

Figure1.The seismic attributes of the actual work area entered into the model and the model calculation results: (A) Original attributes of the work area. (B) Variance attribute of the work area. (C) Results calculated by the ML model

Figure2. Thermal diagram presents the structure of the fault damage zone: (A) A vertical line perpendicular to the fault orientation correction; (B) indicates the fault range with a thermal index greater than 1.572; (C) indicates a fault range with a thermal index greater than 2.065; (D) indicates a thermal index greater than 2.401 fault range. The width of the damage zone could be estimated by these figures.

 

Figure3. Descriptive diagram of fault damage zone width. Fault_1 represents the direction of fault width with thermal index greater than 1.572; Fault_2 represents the direction of fault width with thermal index greater than 2.065; Fault_3 represents the fault width trend map with thermal index greater than 2.401

How to cite: Zhang, J., Chen, S., and Liao, Z.: Machine learning reveals the width of fault damage zones in northeast Sichuan Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14511, https://doi.org/10.5194/egusphere-egu24-14511, 2024.

EGU24-16472 | PICO | TS5.2

How the rigidity of the subducting plate affects the geometry of accretionary prisms? 

Laetitia Le Pourhiet, Alexis Gauthier, Nadaya Cubas, Julie Tugend, and Geoffroy Mohn

Simulations of accretionary prisms are most of the time realized either using a simplified set up that cannot account for the evolution of temperature with the growth of the prism nor deformable basement or using a very large size simulation of the complete subduction zone using a larger resolution locally. The first method is over-simplified and discards the possibility to study crustal scale accretionary prism, the second method is very costly numerically.  

Here, we present simulations of accretionary prisms that use 1/ heatflux as boundary condition allowing the temperature at the base of the model to evolve as the accretionary prism grows and 2/ flexural deformation of the basement in response to the growth of the accretionary prism. This new boundary condition is very cheap to compute as we implemented it by solving analytically the flexure equation using sinus decomposition and image method.  

We then present a set of numerical simulations of crustal scale accretionary prism with particular focus on the geometry of the subducting basement in order to better understand how the alternation between period of subduction erosion and accretion affects the geometry of the accretionary prism and its thermal history as a function of the rigidity of the subducting plate. We compare our simulations with a set of east-west trending seismic profiles located southwest of Taiwan showing along strike structural variations of the accretionary prism.    

How to cite: Le Pourhiet, L., Gauthier, A., Cubas, N., Tugend, J., and Mohn, G.: How the rigidity of the subducting plate affects the geometry of accretionary prisms?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16472, https://doi.org/10.5194/egusphere-egu24-16472, 2024.

EGU24-17730 | ECS | PICO | TS5.2

Numerical simulation of Landscape Evolution using Landlab: A case study of Dibang Basin, North-East India 

Uma Narayan M, Surendra Kumar Sahu, Rishikesh Bharti, and Archana M Nair

The continual modification of the topography due to varied processes results in diverse and dynamic terrain. Landscape evolution studies can link the effect of small-scale topographic quantities on long-term landscape evolution. In this study, the evolutionary pattern of the Dibang basin, located at the limb of the Eastern Himalayan Syntaxis stretch along the active tectonic region of northeast India is analysed using the stream power incision model (SPIM). SPIM is an empirical power law equation linking erosion with channel area and bed slope.  With constant tectonic forcing and homogeneous physical properties, river profiles deviate from linearity and exhibit convexity (indicating uplift) and concavity (indicating erosion) in their longitudinal profiles. These deviations indicate the transient responses of the river profile due to tectonics. Here, the landscape is modelled assuming that the Dibang River lying close to the mountain front shows bedrock properties. The evolved topography is seen to exhibit an erosion-dominated landscape with a rapid decrease in the mean elevation. The profile of the Dibang River exhibits a concave-convex-concave shape, indicating that the river channel is in a state of disequilibrium. The steepness index is observed to be varying across the Dibang basin with higher values in the middle and upper right parts of the basin. The χ plot also reveals the transient nature of the river profile.

How to cite: Narayan M, U., Sahu, S. K., Bharti, R., and Nair, A. M.: Numerical simulation of Landscape Evolution using Landlab: A case study of Dibang Basin, North-East India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17730, https://doi.org/10.5194/egusphere-egu24-17730, 2024.

EGU24-18656 | PICO | TS5.2

Fracture and magma pathways development above sill like magmatic chambers in strike-slip setting 

Martin Staněk, Prokop Závada, and Ondřej Krýza

The Reykjanes Peninsula (RP) in southwestern Iceland represents a zone of oblique rifting where the divergent boundary of the Mid-Atlantic ridge is offset to the eastern Iceland along a left-lateral transform fault - the South Iceland Seismic Zone (SISZ). RP and the SISZ represent regions of the most abundant earthquake activity on Iceland, development of fissure arrays and occasional lava eruptions. A series of earthquake swarms at RP in the 2021-2023 period indicates development of distributed fracture networks along ENE direction of the transform fault and two new fissure arrays trending NE divided by a gap in seismicity. In the last 3 years, the volcanic activity culminated two times in volcanic eruptions, bringing magmas from Moho depth at 15 km.

Inspired by the recent tectonic activity at RP, we conducted a series of analogue experiments consisting of a silicone magma chamber embedded in a photoelastic gelatine crust. The aim of our study is to constrain the links between the depth level of the magma chamber, the crustal scale fracture arrays, faults, magma pathways, superficial fractures and the location of related potential volcanic activity in a transform setting. Inducing strike slip deformation of the system, we explored the influence of shape and orientation of the magmatic chamber on the evolution and pattern of progressively developed fractures along the central shear domain. During the experiment, we captured the stress fringe patterns in the fractured gelatine. The surface deformation was traced by a stereoscopic digital image correlation (DIC) system employing two high-speed LaVision cameras. Analog magma spreading was traced using fluorescent dye mixed to the silicone or into the gelatine interlayer.

Modelling results show that decoupling of the crust above the magma reservoir in strike-slip setting produces a domain with higher vorticity bounded by a conjugate set of tensional fractures. The largest open fractures initiate at and propagate from the intersection of the principal strike-slip fault plane with the vertical contact of the magma chamber and the surrounding crust. Including other open fractures, the orientation of the fracture set is oblique (~ 60°) to the fault plane. With formation approximately coeval to those of the fractures, fine wrinkles at the crust surface are observed with orientation of ~ 120° with respect to the fault plane.

How to cite: Staněk, M., Závada, P., and Krýza, O.: Fracture and magma pathways development above sill like magmatic chambers in strike-slip setting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18656, https://doi.org/10.5194/egusphere-egu24-18656, 2024.

EGU24-1630 | ECS | Posters on site | EMRP3.3

A multi-disciplinary approach to investigate particle dynamics in the South Atlantic Magnetic Anomaly 

Kirolosse Girgis, Tohru Hada, Akimasa Yoshikawa, and Shuichi Matsukiyo

The South Atlantic Anomaly (SAA) represents the minimum magnetic field intensity on Earth, influencing the energetic particle motion within the radiation belts, drawing them closer to our planet. The anomaly region serves as a key location for understanding the dynamics of the radiation belts affected by the magnetospheric response to solar activity.

Our investigation relied mainly on our recent numerical simulation results of the inner radiation belt during two magnetic storm events: May 15, 2005, and February 3-4, 2022. We developed a test particle simulation code to compute the 70-180 MeV proton trajectories in the inner magnetosphere. The IGRF and Tsyganenko models provided the background time-dependent electromagnetic field in response to the input solar conditions. The AP8 model and SAC-C satellite observation confirmed the numerical results. We summarize that protons tend to concentrate more in the SAA’s southern region, while further research found that electrons exhibit a higher tendency to populate the SAA’s northern region due to wave-particle interaction. In light of this conclusion, we identified prolonged Pc5 waves in the ground magnetic field data acquired from stations near the SAA’s northern region provided by MAGDAS/CPMN network.

Examining the particle dynamics inside the SAA is crucial for predicting the radiation environment of LEO missions, forecasting the thermosphere’s response to intense space weather, and anticipating the possible long-term climate changes.

How to cite: Girgis, K., Hada, T., Yoshikawa, A., and Matsukiyo, S.: A multi-disciplinary approach to investigate particle dynamics in the South Atlantic Magnetic Anomaly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1630, https://doi.org/10.5194/egusphere-egu24-1630, 2024.

Thermal core-mantle interactions affect the convection pattern in the outer core and thus the morphology of the generated geomagnetic field.
Correlations between longitudes of lowermost mantle seismic anomalies and prominent geomagnetic flux patches (normal and reversed) provide
evidence for mantle control on the geodynamo (Gubbins et al., 2007, Terra-Nova et al., 2016). Analyses of geomagnetic field models and numerical dynamos with heterogeneous outer boundary heat flux inferred from lower mantle seismic anomalies demonstrated that the SAA longitudinal preferred position is also mantle controlled (Terra-Nova et al., 2019). In contrast, the present latitude of SAA was seldom reproduced. For fundamental understanging of the type of CMB heat flux pattern that may lead to large latitudes of surface intensity minima, we explore dynamo models with different single harmonic CMB heat flux patterns. Our goal is to unravel the core-mantle interaction that induces recurrent large latitude surface intensity minima. Here we show preliminary results from these simulations.

How to cite: Terra Nova dos Santos, F. and Amit, H.: Necessary core-mantle boundary heat flux pattern ingredients for observed latitudes of geomagnetic surface intensity minima, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7419, https://doi.org/10.5194/egusphere-egu24-7419, 2024.

EGU24-7439 | ECS | Orals | EMRP3.3

Archeo- and paleomagnetic records from Saint Helena, South Atlantic 

Patrick Arneitz, Elisabeth Schnepp, and Roman Leonhardt

The South Atlantic Anomaly (SAA) is a dynamic feature of the geomagnetic field. Systematic observations have revealed an expansion of the SAA in terms of its geographical extent and a decrease in field strength over the last decades. Its evolution can be reconstructed further back in time by means of archeo- and paleomagnetic investigations conducted on suitable recorders of the ancient geomagnetic field. Historical geomagnetic field models indicate a westward movement of the SAA from Africa during the last centuries, while its emergence is still under debate, mainly due to the lack of ancient field records in the Southern hemisphere. However, even on much longer timescales, paleomagnetic studies on volcanic rocks from the South Atlantic have suggested a persistence or recurrence of the anomaly.
Here we present ancient geomagnetic field records from the island of Saint Helena from two different periods. Archeomagnetic directions and intensity were obtained from a historical lime kiln that operated until the middle of the 19th century. The reconstructed geomagnetic field components agree well with available instrumental measurements from the island. Geological timescales are covered by paleomagnetic examinations of lava flow profiles from Prosperous Bay and Munden’s Hill. A geomagnetic polarity transition was recorded by some flows at Properous Bay. Several other flows characterized by stable field directions are associated with weak intensities below 20 µT. These results suggest a prolonged anomalous field behavior in the South Atlantic region as indicated by previous studies.

How to cite: Arneitz, P., Schnepp, E., and Leonhardt, R.: Archeo- and paleomagnetic records from Saint Helena, South Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7439, https://doi.org/10.5194/egusphere-egu24-7439, 2024.

EGU24-8153 | Orals | EMRP3.3

The first continental geomagnetic record of an elusive Porcupine? 

Emilio L. Pueyo, Luis Otaño, Roi Silva-Casal, Pablo Calvín, César Laplana, Mª Angeles Galindo-Pellicena, Mathieu Duval, Mª Pilar Mata, Josep María Parés, and Arsenio Muñoz

 

The Porcupine geomagnetic excursion was firstly described at the IODP Site U1308 (North Atlantic). It is a reverse polarity record defined near the top of the Gauss chron (within C2An.1n) and chronostratigraphically constrained between the Kaena and the base of Matuyama reversed chrons. So far, it has been only reported in two different core sections from that site (U1308C-20H-5 and U1308F-20H-2; Channell et al., Q Sci. Rev. 2016). The Porcupine excursion displays a mean age of 2.737 Ma (with an undefined duration) and corresponds to MIS G6 and G7.

The almost 100 m-thick sedimentary infill of the Villarroya Basin (NE Spain), covers part of the Pliocene-Pleistocene period, from about 3.2 Ma to 2.6 Ma. It has been chronologically constrained by means of biostratigraphic and magnetostratigraphic analysis from the middle-upper part of Gauss (chron C2An.2n between Kaena and Mammoth reversed subchrons) to the lower-middle part of Matuyama chron (above the Feni normal event, formerly Réunion). In that work, a short reversal was identified in the upper part of the normal interval N2 of the local magnetostratigraphic sequence attributed to the top of the Gauss chron (C2An.1n around meter 17, figure 7 in Pueyo et al. IJES, 2016), which could possibly represent the first continental record of the Porcupine excursion (ca 2.7 Ma). Such identification was made possible by the occurrence of an outstanding lithological record; annually varved millimetric-scale lacustrine deposits at the base of the basin displaying unusually high sedimentation rates, which may have enabled the detection of such short magnetic excursion.

Given these encouraging results, these deposits were specifically targeted for a subsequent high-resolution palaeomagnetic study focused on ca. 6 m thick subsection where 55 new stratigraphic levels (mean spacing of 10 cm) were studied in detail. In total, more than 120 new specimens were analyzed. Both, stepwise AF and TH demagnetizations of samples were carried out in the paleomagnetic laboratories of the University of Burgos and the National Research Centre on Human Evolution (CENIEH) using 2-G cryogenic superconducting magnetometers. ChRM directions unblocking temperatures between 250-550°C yield the best results and document a complex reverse polarity record. A preliminary and cautious estimation of the time span of this excursion based on the number of annually varved sediments gives a duration of less than 0.5 ka if the sedimentation rate is assumed to be constant and significant sedimentary hiatuses are ruled out.

 

Channell, J. E. T., Hodell, D. A., & Curtis, J. H. (2016). Relative paleointensity (RPI) and oxygen isotope stratigraphy at IODP Site U1308: North Atlantic RPI stack for 1.2–2.2 Ma (NARPI-2200) and age of the Olduvai Subchron. Quaternary Science Reviews, 131, 1-19.

Pueyo, E. L., Muñoz, A., Laplana, C., & Parés, J. M. (2016). The last appearance datum of Hipparion in Western Europe: magnetostratigraphy along the Pliocene–Pleistocene boundary in the Villarroya basin (Northern Spain). International Journal of Earth Sciences, 105, 2203-2220.

How to cite: Pueyo, E. L., Otaño, L., Silva-Casal, R., Calvín, P., Laplana, C., Galindo-Pellicena, M. A., Duval, M., Mata, M. P., Parés, J. M., and Muñoz, A.: The first continental geomagnetic record of an elusive Porcupine?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8153, https://doi.org/10.5194/egusphere-egu24-8153, 2024.

EGU24-9314 | ECS | Orals | EMRP3.3

The Culprit of Bias in the Shaw-type Method of Estimating Geomagnetic Paleointensity and an Innovative Computational Method for Enhanced Reliability 

Kaixian Qi, Shuhui Cai, Huafeng Qin, Chenglong Deng, Yongxin Pan, Yuhji Yamamoto, Xin Cheng, Hanning Wu, and Rixiang Zhu

Retrieving precise information about the ancient geomagnetic field strength (paleointensity) is crucial for understanding the Earth's interior evolution. The Shaw-type method is one of the major protocols used to estimate paleointensity, characterized by relatively expeditious processes and high success rates. However, albeit employing strict selection criteria, Shaw-type paleointensity results occasionally exhibit bias, necessitating further methodological development. Despite the significance of identifying the causes of these biased estimates, there has been limited detailed discussion on this issue.

To clarify the culprit of bias in Shaw-type paleointensity, we conducted a pseudo-Tsunakawa-Shaw experiment using Permian basalts from the Tarim large igneous province (TLIP). In this experiment, the "NRMs (natural remanent magnetizations)" of the samples were acquired in a controlled lab field. We then monitored changes in various rock magnetic parameters, such as squareness (Mrs/Ms), coercivity (Bc), ARM, amtLTD (amount of remanence demagnetized by low-temperature treatment), MDF (median destructive field), and R (the ratio of thermal remanent magnetization (TRM) to anhysteretic remanent magnetization (ARM)), before and after heating, and compared them to the recovered paleointensities.

Our analysis uncover a proportional relationship between changes in R and the bias in paleointensity, likely attributed to variations in grain sizes. Combining with microscopic observations, we further reveal samples with particular magnetic grain sizes (~200 nm) are more prone to alteration in the integral TRM/ARM efficiency during heating. Building on these findings, we propose an innovative computational method exploiting the linear regression of R with various cut-off coercivity intervals for Shaw-type paleointensities (LoRA-Shaw), which yield accurate results in both laboratory-tested and modern lava samples. We also invoke curve fits for samples with “folding” phenomenon which are not suitable for linear regression. The LoRA-Shaw method combined with curve fits may help in mitigating bias from the thermal alteration and multi-domain effect in paleointensity study, and enhance the success rate in paleointensity determinations for constraining geomagnetic field evolution.

How to cite: Qi, K., Cai, S., Qin, H., Deng, C., Pan, Y., Yamamoto, Y., Cheng, X., Wu, H., and Zhu, R.: The Culprit of Bias in the Shaw-type Method of Estimating Geomagnetic Paleointensity and an Innovative Computational Method for Enhanced Reliability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9314, https://doi.org/10.5194/egusphere-egu24-9314, 2024.

EGU24-9550 | ECS | Orals | EMRP3.3

Robustness of new models of the Matuyama-Brunhes field reversal 

Ahmed Nasser Mahgoub Ahmed, Monika Korte, and Sanja Panovska

Paleomagnetic data enables the global reconstruction of the Earth's magnetic field, allowing the investigation of significant global events like polarity reversal. When compared to prior polarity reversals, the most recent one, the Matuyama-Brunhes (MB), is the best recorded reversal event in terms of the amount of available paleomagnetic data. Nevertheless, the majority of these data have poor age control, and they are not distributed equally over the world. Few global spherical harmonic (SH) models have been presented so far for the MB; the most recent is the GGFMB model. These models investigated the evolution of the dipole and non-dipole field components during the reversal process, as well as the morphology of the magnetic field at core-mantle boundary and at the Earth's surface. However, the accuracy of the models features is limited by the aforementioned issues associated with the MB data. In this study, a set of eight SH models were generated for the MB from sub-sets of data, which were classified according to their geographic distribution, timescale reliability, temporal resolution, and type. Comparing the model outputs will allow us to assess how robustly the MB's models can resolve characteristics of the reversal.

How to cite: Ahmed, A. N. M., Korte, M., and Panovska, S.: Robustness of new models of the Matuyama-Brunhes field reversal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9550, https://doi.org/10.5194/egusphere-egu24-9550, 2024.

EGU24-10662 | ECS | Posters on site | EMRP3.3

Spline-based geomagnetic field  modeling revisited 

Maximilian Arthus Schanner, Monika Korte, and Matthias Holschneider

Many existing global geomagnetic field models for historical and longer timescales are based on spherical harmonics for the spatial part and low order basis splines for the temporal dynamics. The related modeling procedure is well established and implements a regularized non-linear least squares inversion. Early papers on the methodology already mention uncertainty estimation in this context. Even though they use a different language, this connects the regularized least squares approach to Bayesian statistics. However, most likely due to computational costs, the ideas from the early papers were lost in subsequent studies and most presented models rely on bootstrapping methods for uncertainty estimation or do not include uncertainties at all. In a statistical setting, this translates to presenting a point estimate (mean or mode) of the posterior distribution.

We revised the established spline based modeling formalism in order to excavate the procedure for uncertainty estimation and complement the point estimate by covariance matrices. This way, uncertainty estimates can be provided for many existing models retrospectively. Using ensemble techniques, the estimated uncertainty can also be propagated to derived quantities like the PSV-index or geomagnetic shielding. Finally, the statistical view provides a new way of estimating the regularization parameters using marginal likelihood optimization. The presented method is applicable to satellite based models in principle, although it is less relevant there due to the large amount of data and uncertainties from other sources (e.g. external fields).

How to cite: Schanner, M. A., Korte, M., and Holschneider, M.: Spline-based geomagnetic field  modeling revisited, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10662, https://doi.org/10.5194/egusphere-egu24-10662, 2024.

The Earth's magnetic field provides protection against highly energetic particles from the Sun and outer space. Throughout geological epochs, the time-varying geomagnetic field exhibited periods of dramatic changes, both in intensity and direction. Recent data compilations of paleomagnetic records enable us to model the long-term, global evolution of the geomagnetic field and better understand the internal dynamics and underlying phenomena. Until now, global reconstructions of the geomagnetic field cover the past 100,000 years and the Matuyama-Brunhes reversal. A few models are available for the Laschamps excursion 41,000 years ago, a period marked by globally low intensity and a complex, multipolar field structure. These models enable the identification of robust characteristics of the geomagnetic field's behavior during this extreme event.

The spatial and temporal changes influence the shielding and cosmogenic nuclide production rates. In general, the higher the field intensity, the larger the shielding and the fewer cosmogenic nuclides are produced in the atmosphere. Variations in the production rates of cosmogenic radionuclides reconstructed from ice cores and sediments provide an independent proxy of paleointensity variations. On the one hand, models constrained by paleomagnetic data can be validated through comparison with actual measurements from ice and marine cores. On the other hand, the cosmogenic radionuclide data can be jointly inverted with the paleomagnetic data to build multi-proxy models of the geomagnetic field. Cosmogenic radionuclide records also serve as a proxy for solar variability and extreme solar events. Global geomagnetic field reconstructions are used to assess the space weather effects during an extreme solar storm event over the past millennia.

How to cite: Panovska, S.: Long-term changes of the geomagnetic field: recent progress, challenges and applications , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10977, https://doi.org/10.5194/egusphere-egu24-10977, 2024.

New paleomagnetic measurements, coupled with 40Ar/39Ar dating of terrestrial lava sequences, are revolutionizing our understanding of the geodynamo by providing high resolution records of the paleomagnetic field. As part of an investigation of the short-term behavior of the geomagnetic field, we have sampled 25 cooling units of the Mauna Kuwale Wai’anae Volcano, Oahu Hawaii. After the flank collapse of the volcano 22 Icelanditic and 3 Rhyodacitic units were identified and sampled in detail for paleomagnetic, rock magnetic and petrofabric (AMS) studies. We performed both NRM and induced magnetic detailed experiments of the 25 individual cooling units. At least eight samples, collected from each of 25 successive cooling units at Mauna Kuwale, were stepwise demagnetized by both alternating field (5 mT to 100 mT) and thermal (from 28°C to 575650°C) methods. Mean directions were obtained by principal component analysis. All samples yielded a strong and stable ChRM trending towards the origin of vector demagnetization diagrams based on seven or more demagnetization steps, with thermal and AF results differing insignificantly. Low-field susceptibility vs. temperature (k–T) analysis conducted on individual lava flows indicated approximately half with reversible curves. Curie point determinations from these analyses revealed a temperature close to or equal to 580°C, indicative of almost pure magnetite ranging from single domain (SD) to pseudo-single domain (PSD) grain sizes for most of the flows. FORCs were also determined. The mean directions of magnetization of the entire section sampled indicate a normal polarity, with 12 transitional cooling units of the sequence characterized by excursional directions. The record shows paleosecular variation within the transitional portion of the record similar to the Lower Mammoth polarity transition found on 3 adjacent units of the Wai’anae volcano. The 40Ar/39Ar isotopic determinations yielded an integrated age obtained from several specimens of 3.314+/- 0.034 Ma.

 

How to cite: Herrero-Bervera, E., Moreira, M., and Jicha, B.: A geomagnetic  and AMSrecord of the  Lower Mammoth  (ca. 3.314+/- 0.034 Ma)  polarity transition recorded in the Icelandic and Rhyodacite  Mauna Kuwale long volcanic sequence Wai’ane Volcano, Oahu, Hawaii, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12842, https://doi.org/10.5194/egusphere-egu24-12842, 2024.

EGU24-13316 | Orals | EMRP3.3

Archeomagnetic study at low latitude - North Atlantic Ocean (Fogo Island, Cabo Verde Archipelago) 

Pedro Silva, Ricardo Ramalho, José Madeira, Mário Moreira, João Mata, António Brum Silveira, and Silvia Foiada

The recovery of the secular variation of the Earth's magnetic field in places of low latitude and in volcanic oceanic islands is crucial for the development of more precise models. Fogo Island (Lat. N14º57’; Long. W24º20’) in the Cabo-Verde Archipelago (Atlantic Ocean) is formed by a major conical and asymmetrical Quaternary strato-volcano with a summit depression (Chã das Caldeiras). It presents itself as a good object of study given its geographical position and frequency of eruptive events, 28 since 1460 A.D.. Accordingly, around Chã das Caldeiras and the east flank of the island, were sampled for paleomagnetic purposes 40 historical and prehistorical lava flows, representing 55 sampling sites. Rock magnetic and petrographic analyses reveal as main magnetic carriers several phases of the titanomagnetite solid solution without visible effects of alteration, as expected for such young basaltic rocks and semi-arid climate. The anisotropy of magnetic susceptibility ellipsoid is low and no effect in the paleomagnetic directions is observed. Thermal and alternating field demagnetizations were successful, retrieving well clustered mean characteristic remanent magnetizations (ChRM) directions. In a first instance twelve ChRM of lava flows previously mapped as historical were compared with known models of secular variation, revealing that nine are in close agreement with the suspected ages while the remaining three failed that concordance, corresponding to prehistoric eruptions. Moreover, it is possible to verify that ChRM of prehistoric lava flows closely follow known secular variation curves showing a small and consistent angular difference. Therefore, such results contribute for a better constraint of the volcano stratigraphy of this island and supply new paleomagnetic directions needed to improve the accuracy of secular variation models.

This research has been funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work is a contribution to projects REGENA (Ref. PTDC /GEO-FIQ/3648/2012) and GEMMA (Ref. PTDC/CTA-GEO/2083/2021).

How to cite: Silva, P., Ramalho, R., Madeira, J., Moreira, M., Mata, J., Brum Silveira, A., and Foiada, S.: Archeomagnetic study at low latitude - North Atlantic Ocean (Fogo Island, Cabo Verde Archipelago), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13316, https://doi.org/10.5194/egusphere-egu24-13316, 2024.

EGU24-13711 | ECS | Orals | EMRP3.3

Evolution and Disappearance of the paleo-West Pacific Anomaly: implications to the South Atlantic Anomaly 

Yaochen Yue, Jiawei Gao, Yong Wei, Fei He, Shuhui Cai, Huapei Wang, Yuqi Wang, and Zhaojin Rong

Paleomagnetism and modern geomagnetic measurements indicate that SAA is undergoing rapid changes, with rapid expansion of area and rapid decreasing of intensity. Even in recent years SAA has expanded the minor minima seen in southern Africa. This has led to speculation that the expanding SAA may be an indicator of an upcoming geomagnetic reversal. However, how to know the future evolution direction of SAA is still debatable.

Apparently, the study of the changes of other SAA-like structure anomaly regions in history has important implications for the study of SAA evolution. Here, we focus on the evolution and disappearance of the paleo West Pacific Anomaly (WPA). Utilizing the gufm1 model, it is found that WPA occurred between 1620 and 1810 CE. Over its duration, WPA underwent phases of rapid expansion, drift, and split, eventually the primary part vanished, while a new segment persisted and expanded. The striking similarity in evolutionary behavior between WPA and the rapid expansion, drift, and recent splitting in the SAA over the past century is noteworthy. This similarity can be attributed to the fact that WPA, like the SAA, is controlled by the reversal flux patch in the CMB on the northern hemisphere. Therefore, we posit WPA as a significant magnetic anomaly in the Northern Hemisphere, and propose that its evolutionary patterns can serve as predictive indicators for the future evolution of the SAA. Studying the evolution of WPA is an important means to understand the global magnetic field and the evolution of Southeast Asia magnetic field. It is of great significance for us to understand the nature of SAA and predict the evolution trend of SAA.

How to cite: Yue, Y., Gao, J., Wei, Y., He, F., Cai, S., Wang, H., Wang, Y., and Rong, Z.: Evolution and Disappearance of the paleo-West Pacific Anomaly: implications to the South Atlantic Anomaly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13711, https://doi.org/10.5194/egusphere-egu24-13711, 2024.

EGU24-13724 | ECS | Posters on site | EMRP3.3

Influence of the South Atlantic Anomaly on Low-Earth Orbit Lightning Observations 

Austin Clark, Shing Fung, Natasha Buzulukova, Timothy Lang, and Burcu Kosar

We present spatiotemporal patterns of interference in low-Earth orbit (LEO) lightning observations within the South Atlantic Anomaly (SAA) and compare them to the patterns obtained from modeled and in situ observations of particle energies and fluxes. In particular, the high sampling frequency of the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) allowed mapping of the SAA to reveal its seasonal and diurnal variability. Overall, lightning observation interference patterns in the SAA have been observed to vary with solar cycle, to lag in peak timing between solar cycle and maximum interference, and to drift longitudinally, similarly to the generally known behaviors of the SAA. However, the seasonality of the SAA from TRMM LIS differed from that of the higher altitude Optical Transient Detector (OTD) and previous studies, e.g., Schaefer et al. (2016), which have shown a bimodal seasonality compared to the more unimodal pattern from TRMM LIS. This is indicative of other potential influences on the interference patterns at the TRMM LIS altitude of 400km.

The LIS and OTD were optical lightning instruments operating in low-Earth orbit from 1995-2023. These packages were designed to observe the near-infrared (777.4-nm) channel, which is emitted by lightning and scattered by the clouds to produce a detectable signal, with a charge-coupled device (CCD) array. Radiation in the low-Earth environment would also impact the sensors and lead to false detections. Much of this noise could be filtered out given the typically random spatiotemporal distribution of radiation, especially when compared to the more organized lightning signal. Recently, however, spatiotemporal patterns have been noted in some portions of these lightning records within the SAA. The trapped radiation in the SAA yields far more false detections than anywhere else for these instruments, and occasionally this increased volume of noise can overwhelm the sensors’ processing capabilities and render it unable to intake new data, effectively blinding it. The blinded state is known as a First-In First-Out (FIFO) buffer overflow and is recognizable as a reduction in the time that the instrument was operating nominally over a given region. Although this effect also occurred with large and intense thunderstorm systems, it was an order of magnitude more common in the SAA, leading to reductions in nominal observation time of up to 80% (per-month for LIS; lifetime for OTD). Tracking the nominal observation time and the FIFO buffer flagging reported by the science data has allowed for the SAA patterns of interference to be extracted, as lightning itself is unaffected by the SAA. The differences in altitude and inclination angle between the OTD and the LIS on TRMM and the International Space Station (ISS) allow for interesting inter-instrument comparisons within these patterns as well, including coincidence with other instruments aboard the ISS during the ISS LIS lifetime.

Schaefer, R.K., Paxton, L.J., Selby, C., Ogorzalek, B.S., Romeo, G., Wolven, B.C., and Hsieh, S.Y., 2016: Observation and modeling of the South Atlantic Anomaly in low Earth orbit using photometric instrument data. Space Weather, 14, 330–342. doi: 10.1002/2016SW001371.

How to cite: Clark, A., Fung, S., Buzulukova, N., Lang, T., and Kosar, B.: Influence of the South Atlantic Anomaly on Low-Earth Orbit Lightning Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13724, https://doi.org/10.5194/egusphere-egu24-13724, 2024.

EGU24-15530 | Posters on site | EMRP3.3

The Gauss and Matuyama recorded in drift sediments from the North Atlantic: preliminary study from IODP Expedition 395C. 

Anita Di Chiara, Sara Satolli, Sarah Friedman, Deepa Dwyer, Boris Th. Karatsolis, Paul N. Pearson, Tom Dunkley Jones, Takuma Suzuki, Anne Briais, Ross E. Parnell Turner, and Leah J. LeVay and the Expedition 395 Science Team

Drift sediments are characterized by a rapid accumulation rate (≥10 cm/kyr), which can provide high-resolution records of the geomagnetic field behavior. Previous ocean drilling in the North Atlantic (e.g., ODP Leg 162 and IODP Exp 306) discovered magnetic instabilities of short duration, such as the Iceland Basin Excursion (188 ka). These records have contributed to our understanding of Earth’s magnetic field variations in the geological past and the foundation of the Geomagnetic Instability Time Scale (GITS) in the Quaternary (0-2.58 Ma).

Between 2020 and 2023, IODP Expeditions 384, 395C, and 395 drilled six sites: five along a transect on the eastern side of the modern Mid-Atlantic Ridge (between 20-30°W at a latitude of ~60°N) and one on the western side, off the coast of Greenland. The expedition aims to investigate the formation of V-shaped ridges and V-shaped troughs in the Reykjanes Ridge and the evolution of deepwater currents.

Shipboard paleomagnetic and microfossil data provided a preliminary age model for all sites, extending the regional record to 11 Ma.

During the Expeditions(s), archive half sections were subjected to alternating field stepwise demagnetization cleaning of natural remanent magnetization. Shipboard paleomagnetic data were processed to remove edge effect, core disturbance, and are integrated with data from discrete samples. All directional data were interpreted, isolating the primary magnetization through the principal component analysis. The discrete samples confirm all polarity changes recognized in the shipboard inclination data. Here, we present the preliminary results from two of the sites drilled during the Expeditions 395C, U1555 (~2.7 Ma) and U1563 (~5.2 Ma), where most of the magnetic events (including excursions and reversals) reported in the Geomagnetic Instability Time Scale of the Quaternary are recognized. These high-resolution records provide the potential to extend the GITS further in the past, expanding the potential of using magnetic instabilities as a dating tool and help to refine our understanding of how the Earth’s magnetic field changed in the past.

How to cite: Di Chiara, A., Satolli, S., Friedman, S., Dwyer, D., Karatsolis, B. Th., Pearson, P. N., Dunkley Jones, T., Suzuki, T., Briais, A., Parnell Turner, R. E., and LeVay, L. J. and the Expedition 395 Science Team: The Gauss and Matuyama recorded in drift sediments from the North Atlantic: preliminary study from IODP Expedition 395C., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15530, https://doi.org/10.5194/egusphere-egu24-15530, 2024.

EGU24-15636 | Posters on site | EMRP3.3

Evaluation of archaeological and pleistocene magnetic field models and their common features 

Ingo Wardinski and Filipe Terra-Nova
Archeo- and paleomagnetic field models show a wide range of temporal variability and of spatial content. While the temporal variability may reflect true geomagnetic field variation, the different spatial content of individual models could be explained by different modeling strategies and data sources, but most likely by data uncertainties. To overcome these problems, we derive a time-dependent mean, median and robust Huber models over the last 100 kyrs from a large suite of different archeo- and paleomagnetic field models (AFM-M, AFM-Md and AFM-H, respectively). These models allow to identify common features of the past field  and to qualitatively assess the robustness and the significance of these spatial features throughout time.
We evaluate each model over the entire period and compute structural criteria that quantify axial dipole dominance, equatorial symmetry, zonality and radial flux concentration at the CMB. These criteria are used to quantify the Earth-likeness of numerical dynamo simulations. Over 100 kyrs, the criteria show larger fluctuations than previously assumed, which implicates a wider range of numerical dynamo simulations to be considered as Earth-like.

How to cite: Wardinski, I. and Terra-Nova, F.: Evaluation of archaeological and pleistocene magnetic field models and their common features, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15636, https://doi.org/10.5194/egusphere-egu24-15636, 2024.

EGU24-17017 | ECS | Orals | EMRP3.3

Paleomagnetism and Relative Paleointensity of Estremenho Limestone Massif stalagmites, from Portugal 

Rafael Dinis, Eric Font, Josep Parés, Janine Carmo, Ricardo Trindade, Luís Vilhena, Ana Sofia Reboleira, Altug Hasözbek, Fernando Jimenez-Barredo, and Emanuel Carvalho

Speleothems magnetism is considered an excellent recorder of short-lived variations of the Earth’s magnetic field. Here we provide new geochronological, petrographic, paleomagnetic, and rock magnetic data of a stalagmite from the Estremenho Limestone Massif (from Central Portugal). The stalagmite was dated at 114.7 (±1.5) k.y. B.P. to 106.3 (±1.6) k.y. B.P. based on the U-Th series. This time interval is coeval with the age of the Blake Geomagnetic Excursion (~116.5 ± 0.7 k.y. B.P. and 112.0 ± 1.9 k.y. B.P.). Petrographic observations under a binocular stereo microscope of two thin sections located at the lower part of the stalagmite and scanning electron microscopic observation of rock fragments show the alternance of porous and compact columnar calcite and dendritic calcite, which are typical features of primary calcite precipitation. No significant gap in the calcite growth was identified along the two thin sections. After alternating field demagnetization, a viscous secondary magnetization was cleaned below 10 mT, followed by a primary magnetization pointing to the origin. Magnetic vectors have an average declination of 60.3° with a mean inclination of 20.1°. No geomagnetic excursion or reversal was identified along the stalagmite. Analysis of Isothermal Remanent Magnetization curves shows the presence of two components. Component 1 has a mean coercivity of ~35 mT and DP ~0,20-0.25, typical of pedogenic/detrital magnetite, and contributed to 75% of the total remanence. Component 2 has a mean coercivity of ~95 mT and DP ~0.30, interpreted as being hematite, and contributing to 25% of the total remanence. We also calculated relative paleointensity (RPI) based on the Pseudo-Thellier method. The RPI curve exhibits a consistent and gradual increase from the base to the top of the stalagmite, with a pattern of variation comparable to the reference curves of marine sediments from the Portuguese margin, in the same time interval. In summary, petrographic and magnetic data point to a primary origin for the calcite precipitation and the corresponding remanent magnetization. The absence of the record of the Blake excursion in this stalagmite still remains to be resolved.

 

This work was supported by the SAMEPA project funded by FCT (ref. PTDC/CTA-GEO/0125/2021) and is part of the Ph.D. of Rafael Dinis (FCT-10216.2022.BD).

How to cite: Dinis, R., Font, E., Parés, J., Carmo, J., Trindade, R., Vilhena, L., Reboleira, A. S., Hasözbek, A., Jimenez-Barredo, F., and Carvalho, E.: Paleomagnetism and Relative Paleointensity of Estremenho Limestone Massif stalagmites, from Portugal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17017, https://doi.org/10.5194/egusphere-egu24-17017, 2024.

EGU24-18282 | ECS | Posters virtual | EMRP3.3

South Atlantic Anomaly as marker of geomagnetic jerks during satellite era 

Saioa A. Campuzano, Angelo De Santis, F. Javier Pavón-Carrasco, and Enkelejda Qamili

The South Atlantic Anomaly (SAA) is an area with values of the geomagnetic field intensity lower than expected ones. The SAA represents one of the most important features of the present geomagnetic field and it is related to the presence of reversed flux patches at the Core-Mantle Boundary. In the satellite era, it has been observed that the SAA areal extent has been continuously growing, with periods alternating positive and negative accelerations. Periods with minima in the acceleration of the SAA areal extent seem to be related to the occurrences of geomagnetic jerks for the last 2 decades. This finding was published in 2021 using the CHAOS-7.2 model. Here, we use the new updated CHAOS-7.16 release to confirm these results, especially relevant in very recent times when edge effects could have affected previous calculations. This new analysis reinforces the proposed link and weaken the idea of a connection by chance. We have also analyzed the acceleration of the areal extent of South American and African reversed flux patches at the Core-Mantle Boundary related to the presence of the SAA at surface and have registered minima in the same periods when they are observed in the SAA at surface. As geomagnetic jerks are sudden changes in the geomagnetic field secular variation related to changes in outer core flow patterns, this result could reinforce the hypothesis that the core dynamics involved in the origin of jerks is related to the physical processes that produce the reversed flux patches, and in turn the SAA evolution.

How to cite: Campuzano, S. A., De Santis, A., Pavón-Carrasco, F. J., and Qamili, E.: South Atlantic Anomaly as marker of geomagnetic jerks during satellite era, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18282, https://doi.org/10.5194/egusphere-egu24-18282, 2024.

EGU24-19081 | ECS | Posters on site | EMRP3.3

Full vector record of the Earth’s Magnetic Field from Upper Pleistocene to prehistoric Holocene lava-flows in La Palma (Canary Islands, Spain) 

Eva Vernet Tarragó, Manuel Calvo Rathert, Ángel Carrancho Alonso, Yuhji Yamamoto, Josep Parés, and Vicente Soler

La Palma, located in the westernmost part of the Canarian Archipelago, is one of the youngest islands in the archipelago. In this study, we present a paleomagnetic and paleointensity study performed in lava-flows from Upper Pleistocene and Holocene prehistoric eruptions from Cumbre Vieja volcano, in the southern part of La Palma Island. Thirteen different sites, each one with a different isotopic age date (Guillou et al., 1998; 2001), have been sampled including basalts, tephrites and phonolites. These rocks represent most of the Upper Pleistocene and prehistoric Holocene dated lava flows in the island.

The aim of this study is to obtain a full-vector record of the Earth’s Magnetic Field in the island during a period comprised between 56 to 1 ka BP. This has been accomplished using alternating field and thermal stepwise demagnetizations to retrieve paleomagnetic directions. For absolute paleointensity determinations, a multi-method approach has been conducted using both Thellier-Coe with pTRM checks and Tsunakawa-Shaw methods, obtaining several consistent results. The agreement of the results with different paleointensity methods provides an additional paleointensity reliability check. In addition, different rock magnetic experiments have been performed, such as magnetization versus temperature curves, isothermal remanent magnetization (IRM) curves, hysteresis loops, backfield and FORCs, showing low coercitivity and variable Curie temperatures, displaying magnetite with different cation substitutions as the main magnetic mineral carriers. All these experiments have been carried out at the University of Burgos, the CENIEH research centre in Burgos (Spain) and the Marine Core Research Institute in Kochi University (Japan) Paleomagnetic Laboratories.

 

Guillou, H., Carracedo, J. C. Day, S. J., Carracedo, J. C. (1998). Dating of the Upper Pleistocene Holocene volcanic activity of La Palma using the unspiked K-Ar technique. Journal of Volcanology and Geothermal Research, 86(1–4), 137-149.

Guillou, H., Carracedo, J. C., Duncan, R. A. (2001). K–Ar, 40Ar–39Ar ages and magnetostratigraphy of Brunhes and Matuyama lava sequences from La Palma Island. Journal of Volcanology and Geothermal Research. 106(3), 175-194.

How to cite: Vernet Tarragó, E., Calvo Rathert, M., Carrancho Alonso, Á., Yamamoto, Y., Parés, J., and Soler, V.: Full vector record of the Earth’s Magnetic Field from Upper Pleistocene to prehistoric Holocene lava-flows in La Palma (Canary Islands, Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19081, https://doi.org/10.5194/egusphere-egu24-19081, 2024.

EGU24-19446 | ECS | Orals | EMRP3.3

Temporal variability in Earth's length of day and its connection with the geomagnetic field energy over the last 3,000 years 

Marina Puente-Borque, F. Javier Pavón-Carrasco, Saioa A. Campuzano, María Luisa Osete, Alicia González-López, and Marta Folgueira

Historical records of lunisolar eclipses and star occultations provide us useful information on the variation of the length of day (LOD) over the last 3,000 years. Besides a steadily increasing trend caused by tidal friction effects, there is evidence for a 1300-year oscillation in the LOD. An adequate explanation for this phenomenon requires considering an interaction between the Earth's mantle and core. Several mechanisms in which the geomagnetic field is directly or indirectly involved have been suggested, including electromagnetic coupling or angular momentum exchange. This study explores the potential connection between fluctuations in the length of day and the energy of the Earth's magnetic field. Through a frequency domain analysis and correlation tests, we examined non-tidal observations in LOD and geomagnetic field energy, using the latest archaeoreconstructions of the global magnetic field spanning the last 3,000 years. As a result, we have found a shared 1,300-year period in the LOD and energy of the non-axial terms of the Earth's magnetic field. These findings are interesting and open a possibility for further research in this field to validate and enhance our understanding of the nature and underlying causes of this potential connection between the Earth's magnetic field and the temporal variability in the LOD

How to cite: Puente-Borque, M., Pavón-Carrasco, F. J., Campuzano, S. A., Osete, M. L., González-López, A., and Folgueira, M.: Temporal variability in Earth's length of day and its connection with the geomagnetic field energy over the last 3,000 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19446, https://doi.org/10.5194/egusphere-egu24-19446, 2024.

EGU24-19724 | ECS | Posters virtual | EMRP3.3

First paleosecular variation intensity curve for the las 4k years for Central Asia  

Raquel Bonilla Alba, Miriam Gómez-Paccard, F. Javier Pavón-Carrasco, Elisabet Beamud, Saioa Arquero Campuzano, Verónica Martinez-Ferreras, José María Gurt-Esparraguera, and María Luisa Osete

Thanks to recent archaeomagnetic studies, it has been observed that the intensity of the magnetic field undergoes abrupt variations in different eras and regions of the planet. In particular, the Levantine Iron Age Anomaly (LIAA), first observed in Israel, has been studied. This phenomenon is characterised by reaching exceptionally high levels of intensity in a short period of time, followed by a rapid decline. Despite the importance of this anomaly, the geographical limit of the LIAA to the east is poorly constrained, with very few studies from Central Asia. The aim of this work is twofold: first, to provide the first high-quality archaeointensity data for the 2nd millennium BC in Central Asia. For this propose, 76 potteries sherds, collected from three different archaeological sites in Uzbekistan date between 2000 and 300 BC, were analysed by Thellier-Thellier method. The second objective is to present a first paleosecular variation (PSV) intensity curve for the last 4000 years, which allows a detailed understanding of the magnetic intensity behaviour in Central Asia. This work not only deepens our understanding of the LIAA and its magnetic implications, but also contributes to the global understanding of variations in the Earth's magnetic field over time.

How to cite: Bonilla Alba, R., Gómez-Paccard, M., Pavón-Carrasco, F. J., Beamud, E., Campuzano, S. A., Martinez-Ferreras, V., Gurt-Esparraguera, J. M., and Osete, M. L.: First paleosecular variation intensity curve for the las 4k years for Central Asia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19724, https://doi.org/10.5194/egusphere-egu24-19724, 2024.

EGU24-19772 | ECS | Posters virtual | EMRP3.3

Magnetic core field anomalies in the non-axial field: approach with a monopole. 

Pablo Rivera, F. Javier Pavón-Carrasco, Angelo De Santis, Maria Luisa Osete, Saioa A. Campuzano, and Gianfranco Cianchini

The continuous update of the archaeomagnetic database spanning the last 3000 years has facilitated the refinement of geomagnetic models, unveiling the presence of non-dipolar anomalies previous to instrumental measurements. Within the Holocene epoch, two anomalies have become notably well-defined. The South Atlantic Anomaly (SAA), characterized by low geomagnetic intensities in the South Atlantic, stands out as the most significant present-day anomaly. Its origin and evolution before instrumental records is still under debate and has been suggested as a possible persistent or recurrent feature of the field. In addition, the Levantine Iron Age Anomaly (LIAA) has been defined as a geomagnetic spike characterized by abnormally high intensities affecting Levant and Europe during the first half of the first millennium BCE.

We approach to the analysis of these anomalies with a simple model, using a monopolar source to locally fit the non-axial field around these anomalies. The movement of the monopoles associated with SAA and LIAA seems to align with regions of the mantle characterized by low shear velocity, particularly the edges of the African Large Low Shear Velocity Province (LLSVP), suggesting a correlation with lower mantle heterogeneities.

 

How to cite: Rivera, P., Pavón-Carrasco, F. J., De Santis, A., Osete, M. L., Campuzano, S. A., and Cianchini, G.: Magnetic core field anomalies in the non-axial field: approach with a monopole., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19772, https://doi.org/10.5194/egusphere-egu24-19772, 2024.

EGU24-21570 | Orals | EMRP3.3

Monte Somma magneto-stratigraphy and growth 

Claudia Principe, Debora Brocchini, Simone Arrighi, Jonas Malfatti, Avto Gogichaishvili, Ilaria Cerbai, Marina Devidze, Sergio Crocetti, Annarita Paolillo, Sonia La Felice, and Daniele Giordano

This work, based on cartographic, morphologic, structural, paleo-magnetic, stratigraphic, and petro-chemical data, depict a new scenario of the Monte Somma growth and the volcanic evolution of this portion of Somma-Vesuvius volcanic complex. The volcanic growth is dominated by the migration of the volcanic source along three main tectonic trends (N040-050°, N070°, and N320°) that governed the formation of the poly-phased Somma caldera. Stratigraphic evidences, stressed by the UBSU use and by age clustering, reveal the occurrence of important climatic changes during Monte Somma formation, affecting its morphology and producing huge volcaniclastic glacial deposits. Magneto-stratigraphic data confirm the presence of an old edifice (Proto Somma Super-Synthem, 25,000 – 39,000 a BP) in the Cognoli di Trocchia area, beheaded by the Pomici di Base flank collapse about 22 ka ago. After this cataclysmic event, volcanic activity produced news volcanic morphologies (Somma Super-Synthem, 5,600 – 25,000 a BP). This second portion of the reconstructed and dated stratigraphic series is subdivided on the four main units: Cognoli di Santa Anastasia, Cognoli di Ottaviano, Cognoli di Levante, and Mercato Synthems. 

How to cite: Principe, C., Brocchini, D., Arrighi, S., Malfatti, J., Gogichaishvili, A., Cerbai, I., Devidze, M., Crocetti, S., Paolillo, A., La Felice, S., and Giordano, D.: Monte Somma magneto-stratigraphy and growth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21570, https://doi.org/10.5194/egusphere-egu24-21570, 2024.

Abstract:

The Deccan Continental flood basalts (DCFB) are associated with three major dyke swarms: the Narmada-Satpura-Tapi (N-S-T), the Western Coastal and the Nasik-Pune dyke swarm. The DCFB around Pachmarhi is characterized by a lower Magnesium number (Mg#) and higher TiO2 content, suggesting more evolved Deccan basalts compared to others. Approximately 244 mappable doleritic and basaltic dykes around Pachmarhi, located in the eastern part of the N-S-T dykes within the DCFB, have lengths ranging from 140 m to 22 km, with a mean of ~5.15 km. The Pachmarhi dyke swarms exhibit emplacement within preexisting fractures, with a discernible preferred orientation aligning at ~N82°E, roughly following an ~E-W trending trajectory. This alignment corresponds to the general trend of the Narmada-Son lineament (NSL) and is perpendicular to the direction of the minimum horizontal stress (σ3). This σ3 direction aligns with the ~N-S trending paleoextension during the period of dyke emplacement. Selected dykes in Pachmarhi have been studied using the Anisotropy of Magnetic Susceptibility (AMS) technique. The primary aim is to determine the direction and sense of magma flow within the dykes, providing insights into the depth, number, and spatial distribution of magma chambers and their potential association with the mantle plume. The Rock magnetic studies on the Pachmarhi dykes have unveiled the presence of high-titanium magnetite particles, predominantly of Pseudo-Single Domain (PSD) nature, with a lesser proportion of Multi-Domain (MD) grains.

To ascertain the direction and sense of magma flow in dyke margins with oblate fabric, the imbrication of the magnetic foliation plane (dip and strike of the K1-K2 plane) has been employed. For dyke margins exhibiting prolate fabric, the imbrication of the magnetic lineation (plunge of the K1 axis) has been utilized. However, in cases where one dyke margin features an oblate ellipsoid and the other a prolate ellipsoid, the imbrication of the magnetic foliation is used for the former, while the imbrication of the magnetic lineation is used for the latter. This thorough analysis has revealed multiple trends of magma flow ranging from vertical/sub-vertical to inclined suggesting that most of the dykes were close to the magma sources, with just a single dyke exhibiting a sub-horizontal flow pattern, based on the angle measurements from the horizontal.

The intersection of imbrication within the margins of each dyke provides valuable information about the flow geometry of the area, suggesting the presence of multiple shallow subcrustal magma chambers. This finding aligns with earlier confirmations through structural attributes (length and thickness of dykes) by quantifying the magmatic overpressure and the source depth of the magma chamber of the Pachmarhi dykes and Nandurbar-Dhule dykes. The multiple trends of flow indicate a polycentric flow pattern for the Pachmarhi dykes, similar to the Nandurbar-Dhule dyke swarms in the western region of the N-S-T dykes. Consequently, it can be inferred that the emplacement of dykes in the NSL region was primarily facilitated by a "polycentric flow" mechanism through sub-crustal magma chambers, whereby magma was injected through crustal fissures, resulting in a significant volume of magma being generated in the DCFB.

How to cite: Shukla, G., Mallik, J., Krishna, Y., and Banerjee, S.: Fissure-Driven Volcanic Processes in the Deccan Province arising from Shallow Subcrustal Magma Chambers: conclusions derived from the magnetic fabric examination of the Pachmarhi Dyke Swarm, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-283, https://doi.org/10.5194/egusphere-egu24-283, 2024.

EGU24-463 | ECS | Orals | EMRP3.2

The Ediacaran Apparent Polar Wander Path of the Río de la Plata craton revisited: Paleogeographic implications. 

Andres Cukjati, Pablo Franceschinis, María Julia Arrouy, Lucia Gómez-Peral, Daniel Poiré, Ricardo Trindade, and Augusto Rapalini

The Ediacaran apparent polar wander path for the Rio de la Plata Craton was analyzed and a new alternative path is presented. This revised path was constructed considering an opposite polarity for poles older than ca. 590 Ma. This path is more consistent with that recently proposed for West Africa, whose large oscillations were attributed to two events of inertial interchange true polar wander (IITPW). A compilation and selection of Ediacaran paleomagnetic data from the main cratons were analyzed leading to a set of global paleogeographic reconstructions throughout the Ediacaran. This model assumes that a “Clymene Ocean” existed between Central Gondwana and West Africa – Amazonia along this period. All cratons with reliable paleomagnetic information, share similar motions during two time-intervals. The first one (615-590 Ma) can be described by rotation around an Euler pole located in the equator, while the second one (575-565 Ma) by another around an Euler pole on the tropics. Whether these apparent large and fast displacements can be assigned to IITPW events is discussed along with the consistency of considering a large Clymene Ocean during this time.

How to cite: Cukjati, A., Franceschinis, P., Arrouy, M. J., Gómez-Peral, L., Poiré, D., Trindade, R., and Rapalini, A.: The Ediacaran Apparent Polar Wander Path of the Río de la Plata craton revisited: Paleogeographic implications., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-463, https://doi.org/10.5194/egusphere-egu24-463, 2024.

Considering the latest data in paleomagnetic, tectonic-geodynamic, paleogeographical mapping, and event stratigraphy [1], several essential characteristics of the sites of the most ancient hominin of the Levant are generalized. The region transitioning from the East African dispersal of ancient hominin to the Eastern Mediterranean is called the Levantine Corridor. In the Late Cenozoic, it was a carbonate platform cut by the essential tectonic element – the Dead Sea Transform (DST). This structure determined the nature of geodynamics, volcanic processes, and landscape conditions during the ancient hominin movement from Africa to Eurasia. An elevated sea level carbonate platform was within the Levantine corridor in the Late Pliocene and Eopleistocene, corresponding to paleomagnetic Chrons of Gauss and Matuyama (C2An-C1r). In the west, the platform 2.0-2.5 Ma was covered by marine transgression, with levels up to 200 m higher than today. Three habitat zones were determined in the Levant to describe the ancient hominin dispersal: (a) Lacustrine-alluvial basin of the Kinneret-Kinnarot depression (Israel) within the DST. Two suites of sedimentary rocks are developed here – 'Ubeidiya (zone C2r) with numerous artifact horizons and Erk el-Ahmar (C2An) – by paleomagnetic data. According to facies data, these are typically pluvial complexes of terrigenous-carbonate rocks, which we compared with the Akchagylian hydrosphere maximum [1]. Palinspastic reconstructions of paleomagnetic maps showed that to the north, the 'Ubeidiya lacustrine basin is replaced by an extensive field of Ruman basalts with radiometric dates of 2.04-2.52 Ma and reverse magnetization rocks averagely corresponding to the paleomagnetic zone C2r; (b) Volcanic-swamp-alluvial Zarqa basin (Jordan) within the DST-shifted northeastern block of the Negev terrane. A complex of volcanogenic-sedimentary rocks is developed here, clearly dated paleomagnetically and radiometrically (1.98-2.52 Ma), with a dominant reverse magnetization of the rocks (C2r) (Scardia et al., 2019). Oldowan artifacts are developed in the upper alluvial layer of the section; (c) Volcanic-alluvial basin of the Yiron plateau of the Upper Galilee uplift on the eastern margin of the Galilea-Lebanon terrane. Here, as in the Zarqa section on the opposite side of the DST, the Ruman basalts series, with a radiometric age of 2.22-2.47 Ma, is developed. It is underlain by gravel-clayey formations, forming an erosional incision with an amplitude of up to 20 m, and is covered by a younger soil-volcanogenic layer. Artifacts attributed to the Acheulean in the incision and soil horizon were found [2]. Thus, all three landscape zones of the Levantine Corridor indicate the development of a unified pluvial complex ('Ubeidiya formation corresponding to the paleomagnetic zone C2 (Early Matuyama)) of lacustrine and alluvial formations on both sides of the DST and in the Kinnarot basin. During this epoch, optimal conditions were formed for the large-scale hominin dispersal from East Africa to Eurasia through the Levantine Corridor.

References

[1] Eppelbaum, L.V. and Katz, Y.I., 2023. Multidisciplinary Geological-Geophysical Analysis Unmasks Anthropological Site Structure in the Northern Part of the Levantine Corridor. Jour. of Anthropological and Archaeological Sci., 8(3), 1056-1078.

[2] Ronen, A., 1991. The Yiron-gravel lithic assemblage artifacts older than 2.4 Ma in Israel. Archäologisches Korrespondenzblatt, 21(2), 159-164.

How to cite: Eppelbaum, L. and Katz, Y.: The landscape-structural zones of the Levant ancient hominin habitat: Revisiting combined paleomagnetic and tectonic-geodynamic analysis, paleogeographic mapping, and event stratigraphy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1363, https://doi.org/10.5194/egusphere-egu24-1363, 2024.

EGU24-2358 | ECS | Orals | EMRP3.2

New Early Carboniferous paleomagnetic results from the Qaidam Block, Northern Tibetan Plateau 

Ruiyang Chai, Yanan Zhou, and Hanning Wu

The Qaidam Block, situated in the North Tibetan Plateau, is the nexus of the Tarim and North China Blocks. Since the scarcity of geological records documenting the collision age between the Qaidam and Tarim Blocks, the drift history of the Qaidam Block becomes imperative for gaining insights into the formation of East Eurasia. In this study, rock magnetic and paleomagnetic studies were performed on the early Carboniferous sedimentary rocks in the Huaitoutala area. A stable characteristic remanent magnetization component, carried by magnetite, was isolated from 24 sites (204 samples). This component passed the fold tests at a high level a mean yielding the paleopole position at λ=-24.9°N, φ=123.7°E, A95=3.9°. It corresponds to a paleolatitude of ~22.5°N for the QB about 350 Ma. Combined with paleomagnetic data and geological evidence from Qaidam Block and its adjacent regions, we suggest that a convergence between the Qaidam Block and the North China Block at 430-400 Ma, subsequently merged with the Tarim Block at approximately 260-250 Ma.

How to cite: Chai, R., Zhou, Y., and Wu, H.: New Early Carboniferous paleomagnetic results from the Qaidam Block, Northern Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2358, https://doi.org/10.5194/egusphere-egu24-2358, 2024.

EGU24-2854 | ECS | Orals | EMRP3.2

Paleomagnetic Dating Constraints on the Genesis of the Leqingla Pb-Zn Deposit, South Tibet, China 

Longyun Xing, Xin Cheng, and Hanning Wu

The Leqingla deposit serves as a representative skarn-type Pb-Zn deposit in the Gangdese polymetallic belt, South Tibet, China. Although numerous studies have been conducted on this deposit, there is no consensus about its specific genesis, particularly concerning the timing of mineralization. Recent studies indicate that paleomagnetic dating techniques, employed on newly formed magnetic carrier associated with mineralized fluids, permit precise determination of mineralization timing. Hence, a systematic paleomagnetic and petrologic investigation was conducted on the host rock of the Leqingla deposit, which is characterized by the middle Permian Luobadui Formation sandstone. The results reveal that the dominant magnetic carrier in the host rock is hydrothermal authigenic pyrrhotite. The stable characteristic remanent components display maximum clustering when flattened to -5.5% ± 13.5% after tilt corrected. The obtained paleomagnetic pole (Plat = 74.5°N, Plong = 222.5°E, at N = 8, A95 = 2.9°) is consistent with that of the Pana Formation volcanic rock in the same area. Further combined with the chronological and geological evidences, we refer that the hydrothermal authigenic pyrrhotite in the host rock may record chemical remagnetization information acquired between 54-47 Ma. The magmatic activity (54-47 Ma) induced by the India-Asia collision is closely related to remagnetization and the formation of the Leqingla deposit.

How to cite: Xing, L., Cheng, X., and Wu, H.: Paleomagnetic Dating Constraints on the Genesis of the Leqingla Pb-Zn Deposit, South Tibet, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2854, https://doi.org/10.5194/egusphere-egu24-2854, 2024.

The India-Eurasia collision reactivated the Tian Shan belt of Central Asia and led to crustal shortening which has
been accommodated by fold-and-thrust belts on both flanks of the orogen. Southward propagation into the Tarim
Basin has been accommodated by the Kuqa fold-and-thrust belts which record a range of well-preserved syntectonic
continental sequences. Using existing magnetostratigraphic age constraints, we have conducted an indepth
paleomagnetic and rock magnetic investigation of this fold-and-thrust belt with the aim of linking the
neotectonic deformation to the uplift of the Tian Shan orogen to the north. Anisotropy of magnetic susceptibility
(AMS) shows “pencil structure” fabrics between levels dated 31.0 and 5.5 Ma. These are succeeded by incipient
deformation fabrics at ~5.3 Ma, which dates an abrupt decrease in shortening by synsedimentary strain. This
change coincides with the timing of initial syntectonic growth strata in the foreland basin of the Southern Tian
Shan and contemporaneous vertical-axis rotations in the Yaha section. Collectively this evidence implies that the
Southern Tian Shan piedmont underwent transpressional deformation with rotation accompanying strain partitioning
during a regional sinistral shear. The extreme aridification which has occurred in the Tarim Basin since
the latest Miocene is interpreted in terms of the deflection of the ambient westerly airstream away from this
region due to the growth of the Tian Shan and its final collision with the Pamir.

How to cite: Qiao, Q.: Paleomagnetic constraints on neotectonic deformation within the SouthernTian Shan piedmont and implications for the latest Miocene enhancedaridification in the Tarim Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5409, https://doi.org/10.5194/egusphere-egu24-5409, 2024.

EGU24-5486 | ECS | Posters on site | EMRP3.2

Belianske Tatry Mts: a story of burial and tectonic strain 

Dorota Staneczek, Rafał Szaniawski, and Leszek Marynowski

The geological evolution of the Tatra Mts (Carpathian range) is very complex. It involves many different episodes/steps: Late Cretaceous thrusting of nappes, Paleocene uplift, Oligocene burial, and final Miocene exhumation of the metamorphic crystalline basement coupled with tilt of the whole massif. Although Tatra Mts are a relatively small mountain range, the intensity of processes affecting them is not uniform throughout the range’s extent. The main goal of our study is to investigate the petromagnetic properties, magnetic fabrics, and paleotemperatures that affected Cretaceous marly limestones, a member of the Mesozoic thrust nappe, and post-thrusting Oligocene black shales in the easternmost part of the Tatra massif: the Belianskie Tatry Mts. In-phase magnetic susceptibility (ipMS) is rather consistent in the black shales and points to a significant contribution of paramagnetic minerals. The most common ferromagnetic mineral, as derived from Isothermal Remanent Magnetization analyses, is magnetite with a minor contribution of hematite and goethite. The marly limestones are characterized by high ferromagnetics to paramagnetics ratio and the presence of superparamagnetic magnetite which can be linked with thermal alteration. Their ipMS is strongly site-dependent. Magnetic fabrics documented in the Belianske Tatry show a complex, multifaceted evolution that was affected by the elevated burial temperatures. In-phase Anisotropy of Magnetic Susceptibility (ipAMS) lineation in Oligocene shales records the uplift-related Early Miocene shortening. Ferromagnetic fabrics as out-of-phase AMS (opAMS) and Anisotropy of Anhysteretic Remanent Magnetization show mixed sedimentary-tectonic features which may be linked with the Oligocene extension of the sedimentary basin. In Cretaceous marly limestones, magnetic fabrics documented by different methods (ipAMS, opAMS, AARM) for each site are consistent which suggests that the orientation of ferromagnetic minerals controls each anisotropy. The origin of magnetic lineation in these rocks is ambiguous and may be linked either with nappe emplacement or later compressional uplift.

How to cite: Staneczek, D., Szaniawski, R., and Marynowski, L.: Belianske Tatry Mts: a story of burial and tectonic strain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5486, https://doi.org/10.5194/egusphere-egu24-5486, 2024.

EGU24-7946 | Posters on site | EMRP3.2

Bottom ocean currents revealed by Anisotropy of Magnetic Susceptibility in the North Atlantic Ocean: Data from IODP Expeditions 384, 395C and 395 

Sara Satolli, Anita Di Chiara, Sarah Friedman, Deepa Dwyer, and Gary Acton and the IODP Expedition 395 Science Party

We report preliminary results from the magnetic stratigraphy and the anisotropy of magnetic susceptibility (AMS) of 6 sites drilled from the International Ocean Discovery Program Expeditions 384, 395C and 395 in the North Atlantic Ocean. Five sites were drilled along a transect on the eastern side of the modern Reykjanes Ridge (including Gardar drift and Bjorn drift), and one on its western side, close to Greenland (Eirik drift).

The magnetic stratigraphy provides a precise record of geomagnetic reversals that, coupled with biostratigraphic data, was used to build an age model for each site. The resulting age models provide constraints on variations in sedimentation rate, as well as variations in the AMS parameters.

The AMS was used to investigate the strength and direction of bottom currents, with implications for oceanic gateway evolution. The AMS data were reoriented using the shipboard mean declination of the cores at 20 mT, assuming a geocentric axial dipole hypothesis, and time-averaged paleosecular variation.

The AMS parameters (lineation, foliation, anisotropy factor, and shape parameter) document the onset and change in the strength of bottom currents. The current direction is generally consistent with that of modern instrumental measurements (NNE - SSW), at least in the last 2.5 Myr.

How to cite: Satolli, S., Di Chiara, A., Friedman, S., Dwyer, D., and Acton, G. and the IODP Expedition 395 Science Party: Bottom ocean currents revealed by Anisotropy of Magnetic Susceptibility in the North Atlantic Ocean: Data from IODP Expeditions 384, 395C and 395, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7946, https://doi.org/10.5194/egusphere-egu24-7946, 2024.

EGU24-9942 | Posters on site | EMRP3.2

Reproducibility of high field magnetic remanence: Implications for precision of high field remanence anisotropy 

Frantisek Hrouda, Martin Chadima, and Josef Jezek

It was shown in the earlier model studies that the precision in the determination of the anisotropy of magnetic susceptibility (AMS) depends in a directly proportional way on the precision of the measurement of the directional susceptibility in relation to the degree of anisotropy. These results can be closely applied to the measurement of the anisotropy of magnetic remanence (AMR).

While the AMR imparted in weak to moderate fields is relatively frequently used in rock fabric studies, only a few attempts to establish the anisotropy of magnetic remanence imparted in high fields (HFRA) were reported. The reasons for the virtual absence of the HFRA studies may be both instrumental (insufficient precision in setting up the intensity of magnetizing field, insufficiently homogeneous magnetizing field) and methodological (time variation of imparted remanence, unknown properties of high field remanence).

Recently, an impulse magnetizer was developed (commercial name PUMA) that enables the standard palaeomagnetic specimen to be magnetized in a defined orientation in the wide range of magnetic fields from 1 mT to 5 T. Elaborate design of the instrument provides precise setting of the pulse intensity as well as high homogeneity of the field over entire specimen volume. In addition, reproducibility in imparting the remanence in the same direction by the same field was investigated as well as it was investigated whether it is desirable to demagnetize the specimen between individual magnetizations to improve the remanence reproducibility despite that each high field magnetization (“saturation”) theoretically obliterates the previous remanence. The investigations were made on specimens having single mineral ferromagnetic fraction (magnetite, hematite and pyrrhotite ones). The results help us to decide whether the HFRA is convenient to most rocks or only to strongly magnetic and strongly anisotropic ones.

How to cite: Hrouda, F., Chadima, M., and Jezek, J.: Reproducibility of high field magnetic remanence: Implications for precision of high field remanence anisotropy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9942, https://doi.org/10.5194/egusphere-egu24-9942, 2024.

EGU24-10116 | ECS | Orals | EMRP3.2

The localized rotations in Junggar Block for the last 50 Myr: new paleomagnetic constraints  

Mengting Zhong, Vadim Kravchinsky, Rui Zhang, and Xin Cheng

We present an analysis of paleomagnetic data from Cenozoic sedimentary rocks of the northern Junggar Block in central Asia to assess if the northern Junggar Block has suffered vertical axis rotations with respect to stable Eurasia. Stepwise thermal demagnetizations isolated a stable high-temperature component of magnetization in most specimens, which we interpret as the primary magnetization from the positive reversal test. Based on high-resolution magnetostratigraphic studies (Zhang et al., 2007, 2012), we calculated the mean direction of each 5 Myrs of 44-30 Ma and 25-17 Ma covered by the sample age and yielded seven mean directions in 45-37.5 Ma, 40-35 Ma, 37.5-32.5 Ma, 35-30 Ma, 25-20 Ma, 22.5-17.5 Ma, respectively. The variation between the observed declination from the study area and the reference declination from Eurasia indicates that a local counterclockwise rotation of 18.8 ± 11.4° took place during 40±2.5 - 35±2.5 Ma. Together with the paleomagnetic data during 23-3.1 Ma in the southern part of the Junggar Basin (Charreau et al., 2005, 2009), it can be concluded that Junggar Block experienced local counterclockwise rotation with respect to the Eurasia in the piedmont of the north and south rim successively due to the strike-slip fault. At a larger scale, the blocks in the Central Asia Right–Slip Fault Zone have experienced tectonic rotation at different times under the far-field effect of India-Eurasia collision, that is, formed an overall counterclockwise vertical axis rotation mode of different stages because of strike-slip faulting.

How to cite: Zhong, M., Kravchinsky, V., Zhang, R., and Cheng, X.: The localized rotations in Junggar Block for the last 50 Myr: new paleomagnetic constraints , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10116, https://doi.org/10.5194/egusphere-egu24-10116, 2024.

EGU24-10173 | Posters on site | EMRP3.2

Magnetic fabric, anisotropy of magnetic susceptibility (AMS), and inferred flow directions of dikes from Fogo Volcano, Cape Verde. 

Mario Moreira, José Madeira, Joao Mata, Pedro Silva, Ricardo Ramalho, and António Silveira

Fogo Island is an active volcano with at least 28 eruptions since 1460, the latest of which in 2014-2015. It is formed by a major conical and asymmetrical Quaternary strato-volcano with a summit depression (Chã das Caldeiras), within which a 1 km-tall cone rises to 2829 m, the maximum elevation of the island. The 8 km-wide Chã das Caldeiras is truncated by a large eastward flank collapse. Morphologically this depression is formed by two intersecting calderas, a northern and a southern one, separated by a spur (Monte Amarelo). The depression is surrounded on the north, west and south by an almost vertical wall (Bordeira) that reaches a maximum height of 1000 m. More than 500 dikes and sills, with widths ranging between 0.5m to 8m are exposed crosscutting the Bordeira wall, most of them broadly radial.
We studied 34 dikes along the base of Bordeira. The mean orientations of the dikes show two convergence areas. One, poorly constrained, located in the northern caldera, east of the Monte Amarelo spur, and another, well defined, broadly in the centre of southern caldera. These two convergence points are inferred as the origin of most of the radial dikes and suggest two distinct magmatic centres, which collapsed to form the calderas.
Magnetic susceptibility (MS) of the 34 studied dikes is lower than 140×10-3 SI units, without any noticeable systematic differentiation between the MS of the dikes of the different sectors.
Most of the dikes/margins (79%) show “Normal Magnetic Fabric”, defining an interpretable imbrication angle between the magnetic foliation plane (MFP) and dike margin. This behaviour shows that magnetic fabric (MF) orientation at the time of intrusion and late stages of cooling, was controlled by the dynamics of the magma flow. Just a few dikes mostly located in the intersection of the calderas display Intermediate or Inverse MF.
Thermo-magnetic k(T) analysis shows titanomagnetite as main magnetic carrier with compositions varying between Ti-rich to Ti-poor. Some samples show multiple magnetic phases identified by different Curie temperatures. Hysteresis measurements show that most of the samples fall in the PSD region with some samples showing a SD characteristic. This is consistent with the Intermediate and/or Inverse MF, observed in some margins, suggesting coexisting mixtures of inverse (SD grains) and normal (PSD and MD grains), magnetic fabrics.
Considering only the normal magnetic fabric margins (with usually triaxial or oblate AMS ellipsoid) and using the model of the imbrication of the MFP we obtain in 39 margins (57%), a reliable result that enables to infer a direction and sense of the magmatic flow. Results indicate an outward and mostly horizontal to near-horizontal flow, suggesting shallow magmatic sources. A few dikes show margins with asymmetric (“scissored”) magnetic fabrics which may indicate strike-slip shearing along the dike in the last phases of magma cooling.
This research has been funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work is a contribution to project GEMMA (Ref. PTDC/CTA-GEO/2083/2021)

How to cite: Moreira, M., Madeira, J., Mata, J., Silva, P., Ramalho, R., and Silveira, A.: Magnetic fabric, anisotropy of magnetic susceptibility (AMS), and inferred flow directions of dikes from Fogo Volcano, Cape Verde., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10173, https://doi.org/10.5194/egusphere-egu24-10173, 2024.

EGU24-11793 | ECS | Orals | EMRP3.2

Novel paleomagnetic insights into the timing of serpentinization of peridotites in the Troodos ophiolite 

James Hepworth, Antony Morris, Michelle Harris, Alec Brenner, Roger Fu, Richard Harrison, and Esther Schwarzenbach

Large volumes of mantle peridotite are exposed at the Earth’s surface in ophiolites, becoming vulnerable to the concurrent chemical alteration processes of serpentinization and carbonation. Serpentinization frequently results in the production of secondary magnetite that records the direction of the Earth’s magnetic field at the time of its formation, allowing paleomagnetism to be used as a tool to investigate this process. 

Many ophiolites also experienced large-scale tectonic rotations during their evolution. In some cases, the timing of these rotations is well-documented paleomagnetically, potentially allowing the timing of different phases of serpentinization to be constrained if the magnetization directions of secondary magnetite assemblages can be determined and compared to known rotation histories. Here we present the first attempt to combine paleomagnetic analysis with Quantum Diamond Microscopy (QDM) observations of individual magnetic grain assemblages to test whether sequential phases of alteration can be dated in serpentinized peridotites in this way. 


We focus on the Late Cretaceous Troodos ophiolite of Cyprus that underwent a ~90 CCW tectonic rotation that began shortly after it formed by seafloor spreading. The timing of this rotation is well-constrained by paleomagnetic analysis of the sedimentary rocks that were deposited continuously while the underlying oceanic crust rotated. In this context, different magnetization directions would be expected to be carried by magnetite assemblages produced by serpentinization during: (i) early exposure on the seafloor or deep fluid circulation during Late Cretaceous seafloor spreading; (ii) subsequent progressive tectonic rotation; and (iii) Plio-Quaternary to Recent tectonic uplift and/or reaction with modern meteoric water.


Magnetization directions within the Troodos serpentinites are shown to be highly variable, and include: (i) samples carrying W-directed, high-coercivity components, inferred to be acquired in the Late Cretaceous, and NNW-N-directed, low-coercivity overprints, inferred to be acquired post-rotation; (ii) samples with single component, NW-directed magnetizations, inferred to have been acquired partway through the rotation; (iii) samples with single component, N-directed magnetizations inferred to have been acquired post-rotation; and (iv) one site where samples exhibit antipodal normal and reversed polarity, N-S-directed magnetizations inferred to have been acquired post-rotation but before the Brunhes-Matuyama reversal (780 ka). Overall, these data demonstrate that serpentinization occurred throughout the entire history of the Troodos Ophiolite, with six sites showing evidence of serpentinization in the Late Cretaceous or partway through the rotation and six sites where serpentinization occurred post-rotation from the Eocene to the present day. QDM data from one site where samples exhibit a W-directed ChRM and a NNW-N-directed overprint confirm that all observed magnetite associated with serpentine veins carries the early ChRM, inferred to be acquired during the Late Cretaceous. The source of the low stability component in these samples was not observed in QDM images and remains elusive, but is interpreted to be a modern magnetic overprint.

How to cite: Hepworth, J., Morris, A., Harris, M., Brenner, A., Fu, R., Harrison, R., and Schwarzenbach, E.: Novel paleomagnetic insights into the timing of serpentinization of peridotites in the Troodos ophiolite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11793, https://doi.org/10.5194/egusphere-egu24-11793, 2024.

The anisotropy of magnetic susceptibility (AMS) has great potential in deciphering weakly deformed fabrics that may be related to tectonic stress. Previous studies have suggested that magnetic lineation is a good indicator of paleostrain direction. It is unclear whether the magnetic fabric can also be used to indicate the present-day strain field. To verify this idea, we measured the AMS of freshly consolidated lacustrine fine-grained and horizontal-bedding sediments at 11 locations in the Qaidam and Chaka-Gonghe basins of the northeastern Tibetan Plateau and compared it with the present-day strain field deduced from the Global Position System (GPS) velocity field. The AMS of these sediments appears a weakly deformed fabric with clear foliation and lineation. The optical and scanning electron microscope (SEM) images of the thin sections show that the elongated particles display an orientation parallel or subparallel to the magnetic lineation direction, confirming the effectiveness of magnetic lineation. The magnetic lineations of both room-temperature and low-temperature AMS are roughly perpendicular to the GPS-derived tectonic shortening direction within the error range, suggesting that the AMS of freshly consolidated muds is an effective indicator of the present-day strain field, even if the sediments appear undeformed at the outcrop scale.

How to cite: Xie, H. and Liu, C.: Magnetic Fabric of Freshly Consolidated Lacustrine Mudstones Constrains the “Present-Day” Strain Field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14634, https://doi.org/10.5194/egusphere-egu24-14634, 2024.

EGU24-16032 | ECS | Orals | EMRP3.2

New palaeomagnetic data from tillites of Neoproterozoic Polarisbreen Group, Nordaustlandet, Svalbard 

Szczepan Bal, Krzysztof Michalski, Geoffrey Manby, Krzysztof Nejbert, Jarosław Majka, Justyna Domańska-Siuda, and Aleksandra Hołda-Michalska

New demagnetization results of 53 independently oriented palaeomagnetic samples (145 specimens) of diamictite-rich units from 8 sites collected from the Neoproterozoic sequence of Murchisonfjord, Western Nordaustlandet are presented. The palaeomagnetic samples were obtained from 2 distinct stratigraphical units of Polarisbreen Group: Petrovbreen Member of Elbobreen Formation (2 sites) and Wilsonbreen Formation (6 sites) which represent Marinoan Neoproterozoic glaciation (Halverson et al. 2004). The sequence is a part of Eastern Svalbard Caledonian Terrane/Northeastern Basement Province.

Principal component analyses revealed strong contribution of post-folding high-inclination palaeomagnetic component TILL L/M demagnetized up to 320°C (D = 32.3°, I = 83.6°,  α95=6.6, κ=103.7 recognized in 6 sites, in 35 independently oriented samples and in 77 demagnetized specimens). Calculated paleopole TILL L/M (Φ = 83.24°, Λ = 114.0°; Dp/Dm = 12.7°/13.0°) fall into Late Cretaceous – Paleogene – Neogene sector of Baltica Apparent Polar Wander Path (Torsvik et al. 2012). That suggests a possible relation of TILL L/M remagnetization with Late Cretaceous Svalbard magmatism (e.g. Senger et al. 2014). Great circle analyses point to the additional contribution of low-inclination component, potentially related to Caledonian remagnetization (compare Michalski et al. 2023). At this data processing stage, in investigated tillites no pre-Caledonian paleomagnetic record was recognized. Preliminary rock-magnetic results suggest the presence of maghemite and magnetite. Paleomagnetic, rock-magnetic as well as investigations of Anisotropy of Magnetic Susceptibility (AMS) were conducted at the Laboratory of Palaeomagnetism Department of Magnetism Institute of Geophysics, Polish Academy of Sciences.

All investigated tillites were subjected detailed petrographic and mineralogical observations (reflected /transmitted light microscopy, scanning electron microscopy – SEM, electron microprobe) at the University of Warsaw Inter – Institute Analytical Complex, in the Faculty of Geology and at the Uppsala University in the Department of Earth Sciences. Separated detrital zircons is being subjected to U-Pb dating at the Department of Geological Processes, Czech Academy of Sciences.

This study is part of the NEOMAGRATE project 2022–2025: “Rate of tectonic plates movement in Neoproterozoic – verification of Neoproterozoic True Polar Wander hypothesis”, funded by the Polish National Science Centre (NSC); grant number:2021/41/B/ST10/02390.

References:

Halverson, G.P., Maloof, A.C. and Hoffman, P.F. 2004. The Marinoan glaciations (Neoproterozoic) in northeast Svalbard. Basin Research, 16, 297-324.

Michalski, K., Manby, G.M., Nejbert, K., Domańska-Siuda, J. and Burzyński, M. 2023. Palaeomagnetic investigations across Hinlopenstretet border zone: from Caledonian metamorphosed rocks of Ny Friesland to foreland facies of Nordaustlandet (NE Svalbard). Journal of the Geological Society, 180.

Senger, K., Tveranger, J., Ogata, K., Braathen, A. And Planke, S. 2014. Late Mesozoic magmatism in Svalbard: A revive. Earth-Science Revievs, 139, 123-144.

Torsvik, T.H., Van der Voo, R., Preeden, U., Mac Niocaill, C., Steinberger, B., Doubrovine, P.V., van Hinsbergen, D.J.J., Domeier, M., Gaina, C., Tohver, E., Meert, J.G., McCausland, P.J.A. and Cocks, L.R.M. 2012. Phanerozoic polar wander, paleogeography and dynamics. Earth-Science Reviews, 114, 325–368.

How to cite: Bal, S., Michalski, K., Manby, G., Nejbert, K., Majka, J., Domańska-Siuda, J., and Hołda-Michalska, A.: New palaeomagnetic data from tillites of Neoproterozoic Polarisbreen Group, Nordaustlandet, Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16032, https://doi.org/10.5194/egusphere-egu24-16032, 2024.

EGU24-16117 | ECS | Orals | EMRP3.2

A 3D Cretaceous palinspastic model from paleomagnetic data in the Central High Atlas (Morocco) 

Laura Yenes, Pablo Calvín, Pablo Santolaria, Juan José Villalaín, and Marcos Marcén

The Central High Atlas is the Moroccan segment of the Atlas System, which is the largest intraplate mountain range in North Africa. The Mesozoic evolution of the High Atlas is related with extensional tectonics, magmatic activity, and salt tectonics. It primarily consists of basins developed during the Triassic and Jurassic that underwent inversion during the Cenozoic. The region exhibits dominant NE-SW and ENE-WSW trending folds, intertwined with smaller-scale oblique or perpendicular folds.

Previous paleomagnetic investigations have revealed that sedimentary Jurassic rocks (both carbonates and red beds) in the Central High Atlas are affected by a Cretaceous regional remagnetization. This interfolding remagnetization, occurred after the syn-sedimentary tectonic extensional stage but before the Cenozoic basin inversion linked to the convergence between the African and European plates. The reference of remagnetization direction has been determined using the Small Circle Intersection (SCI) technique and, by comparing it with the African Aparent Polar Wander Path (APWP), has been dated to approximately 100 million years (Ma), representing a synchronous phenomenon across the entire High Atlas. Once the reference is stablished, paleomagnetic data can be used to calculate the paleobedding of each site at the remagnetization time (i.e. between extension and compressional stages) and to restore the structure at 100 Ma. This procedure allows to quantitatively separate the compressional imprint from the extensional one in the present-day structure.

This work presents a high-resolution paleomagnetic study in the Anemzi syncline area, encompassing 91 sites within the paradigmatic structures of the Central High Atlas, covering an area of 35 km². The Anemzi syncline features a southern limb bounding with a vertical set of Jurassic intrusive bodies and Triassic shales and basalts, while the northern limb exhibits Lower Jurassic carbonates overthrusting northwards Middle Jurassic rocks.

By applying Small Circle analysis to remagnetization directions, 91 paleobeddings corresponding to the age of remagnetization (i.e., 100 Ma) were determined. These paleobeddings were employed to construct seriated geological cross-sections, depicting the structural architecture 100 Ma ago. These cross-sections were then compared with their present-day counterparts. Both series of cross-sections were the base to develop two 3D geological models, showcasing the present-day and restored structures at 100 Ma, integrating both paleomagnetic results and structural data.

Comparisons between palinspastic and present-day cross-sections and 3D models provide insights into the evolution of the Central High Atlas, spanning both the basinal stage and subsequent inversion. This comparative analysis offers valuable clues for understanding the significance of inherited extensional structures (such as normal faults, gabbro intrusion, diapirism, etc.) in the context of compressional structuring.

How to cite: Yenes, L., Calvín, P., Santolaria, P., Villalaín, J. J., and Marcén, M.: A 3D Cretaceous palinspastic model from paleomagnetic data in the Central High Atlas (Morocco), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16117, https://doi.org/10.5194/egusphere-egu24-16117, 2024.

Magnetic fabrics derived from the anisotropy of magnetic susceptibility (AMS) depict the preferred alignment of grains and crystal lattices in minerals contributing to magnetic susceptibility. These fabrics serve as reliable indicators of strain in deformed terrains. Early research primarily focused on rocks lacking visible fabrics, such as granites and quartzites. However, there has been a recent surge in the application of magnetic fabric analysis to Himalayan rocks, particularly for insights into tectonic activity. In the present study, structural and magnetic data along the Alaknanda-Dhauliganga valley is presented majorly focusing on the sheared rocks of the MCTz. The aim of the present work is to elucidate the utility of magnetic fabrics in resolving the ambiguity of the MCT, distinguishing between the Munsiari Thrust (MCT-I) and Vaikrita Thrust (MCT-II). The analysis shows a gradual change in compactional oblate fabric along with the parallel alignment of thrust-induced magnetic fabrics, reflecting its geometry and proximity to intense deformation zones. Here, a notable change in the degree of anisotropy (Pj) is also observed as the rocks transition towards the thrust zones. This transition is accompanied by a shift to a quantitatively more prolate fabric, indicating a change in nature of strain. The study observes an anisotropy degree (Pj) ranging from 1.1 to 3.2, with mostly positive shape parameter (T), except near MCT where negative values are noted. Additionally, we also investigate contributors of magnetic fabric by estimating the mean magnetic susceptibility (Km) for all the samples and cross-verify the results with petrographic and magneto-mineralogy studies. Vibrating Sample Magnetometry (VSM) was also employed to identify magnetic carrier types. This study also shows a strong correlation between macroscopic features and magnetic fabrics indicating dominance of structural deformation (independent of magnetic mineral assemblages) in the region. In conclusion, the study highlights that strain within the studied area varies with distance from areas of intense deformation, and these variations are distinctly characterized by changes in magnetic fabrics.

How to cite: Borgohain, A., Bhatt, S., and Banerjee, S.: Magnetic Fabric Analysis of Sheared Rocks along the Alaknanda-Dhauliganga Valley: Insights into the Structural Deformation and Evolution of the Main Central Thrust in the Himalayan Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16950, https://doi.org/10.5194/egusphere-egu24-16950, 2024.

The Xigaze forearc basin was formed along the southern margin of Asia as the Neo-Tethys Ocean subducted beneath Asia. Among the strata within the Xigaze forearc basin, the Padana Formation (Fm) comprises purple-red and gray shale interbedded with sandstone, and likely holds crucial evolution information of the southern Asian margin during the Late Cretaceous prior to the India-Asia collision. However, the chronology of the Padana Fm has not been well constrained. To refine the chronology of the Padana Fm and better constrain the paleopositions of the southern margin of Asia, we conducted a paleomagnetic study of the strata in the Xigaze forearc basin, with a particular focus on the Padana Fm. A total of 263 paleomagnetic samples were collected and subjected to stepwise thermal demagnetization, revealing two-component magnetizations. The low temperature component (LTC) was removed by ~300℃, representing overprints of the present geomagnetic field. The high-temperature component (HTC) was typically unblocked at 580∼680 °C, indicating magnetite and hematite as major remanence carriers. A total of 110 reliable HTCs were isolated from the sandstones in the Padana Fm and passed reversal tests, representing primary remanence. Changes in polarities of the HTCs with stratigraphic heights define four polarity zones, which, together with results of previous detrital zircon U-Pb ages and biostratigraphic zones, allow to constrain the chronology of the Padana Fm to 83.6 Ma-69.2 Ma. With the significantly refined chronology, the paleomagnetic data of the Padana Fm can be used to constrain the tectonic evolution of the Xigaze forearc basin in the Late Cretaceous. Tentative interpretations of the coeval paleogeography of the southern Asian margin prior to the India-Asia collision will be discussed.

How to cite: Xu, S., Li, Y.-X., Liu, X., Li, B., and Li, X.: Paleomagnetism of the Late Cretaceous Padana Fm in Xigaze forearc basin and its paleogeographic constraints on the southern margin of Asia prior to the India-Asia Collision, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17916, https://doi.org/10.5194/egusphere-egu24-17916, 2024.

EGU24-18588 | Posters on site | EMRP3.2

Devonian paleomagnetism in the West Qinling mountains of China and its tectonic significance 

Yongfa Chen, Shuang Dai, Mark Dekkers, and Qiang Fu

The Qinling Orogenic Belt (QOB) traverses east-west across the central part of continental China. Being the suturing of the North China Block and the South China Block, it represents a distinctive and typical composite continental orogenic belt that holds a prominent position in the formation and evolution of continental China. As an integral segment of the QOB, the West Qinling was originally formed by the collision of the North China block and the South China block during the Paleozoic and Triassic. It was superimposed by the Mesozoic and Cenozoic intracontinental orogeny. Thus it has undergone a prolonged history of formation and evolution. Devonian strata are central to our understanding of the QOB geology. However, their paleolatitude is currently poorly constrained. Therefore, we conducted a paleomagnetic study on Devonian limestone samples (32 sites, 352 samples) from the West Qinling (34.2°N, 103.1°E). For optimal results, a combination of thermal demagnetization and alternating field demagnetization was employed. In addition, rock magnetic experiments will be executed on a subset of representative samples, including M-T curves, hysteresis loops, and FORCs. About 55% of the samples yield characteristic remanent magnetization (ChRM) directions. The demagnetization curves show two-component characteristics, with the medium and high temperature components tending to the origin (200~500℃), while the remainder unveiled inconsistent ChRM directions. This study aims to reconstruct the paleolatitude of the West Qinling during the Devonian, and to provide new insights into the tectonic evolution of the QOB.

How to cite: Chen, Y., Dai, S., Dekkers, M., and Fu, Q.: Devonian paleomagnetism in the West Qinling mountains of China and its tectonic significance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18588, https://doi.org/10.5194/egusphere-egu24-18588, 2024.

EGU24-21961 | Posters on site | EMRP3.2

DeformAMS: A simple toolbox for modelling magnetic fabric evolution during rock deformation  

Martin Chadima and Frantisek Hrouda

The magnetic fabric, studied mainly by means of anisotropy of magnetic susceptibility (AMS), has become one of the well-established, fast, and reliable rock fabric proxies applied in many branches of Earth sciences. The magnetic fabric of rocks reflects the crystallographic or shape preferred orientation of all rock-constituent mineral grains; each mineral grain contributes to the overall fabric according to its single-grain anisotropic properties and its orientation.

Because magnetic fabric is very sensitive to strain, a simple tool box is presented to model its evolution as a results of rock deformation. The toolbox works with a set of uniformly distributed model particles deformed following the so-called line/plane model which assumes that the particles behave as if they formed lines or planes in the deforming rock matrix; their shapes do not change in response to the imposed deformation but their orientation does. The pre-deformational and deformational magnetic fabrics are considered, both having originated through combined pure shear and simple shear acting in the pre-defined directions.

The resultant magnetic fabric tensor is calculated by integrating the combined contribution of the entire set of modelled particles. The results are presented in terms of the principal AMS directions, degree of anisotropy, and shape of anisotropy ellipsoid. The presented toolbox is an integral part of Anisoft6 software which enables the instant visualization of how magnetic fabric gradually changes as a function of progressive deformation.

The research was in partially conducted within the research plan RVO 67985831 of the Institute of Geology of the Czech Academy of Sciences.

How to cite: Chadima, M. and Hrouda, F.: DeformAMS: A simple toolbox for modelling magnetic fabric evolution during rock deformation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21961, https://doi.org/10.5194/egusphere-egu24-21961, 2024.

EGU24-1949 | Posters on site | ITS5.2/SSP1.13

Plio-Pleistocene Southern Ocean Paleoceanography: Latitudinal drilling in the Southwestern Indian sector of the Southern Ocean 

Minoru Ikehara, Xavier Crosta, Samuel Jaccard, Tim Naish, and Yasuyuki Nakamura

Proposal 918-pre in the Southern Ocean exists in the current science evaluation system of IODP. Site surveys were completed in 2019. We would like to develop an international research project based on this proposal by conducting new drilling/coring in the IODP3. First, we would like to drill by riserless drilling vessel, but if drilling is not feasible, we plan to consider giant piston coring as an option.

 The Southern Ocean (SO) is a key region that profoundly influences climate variability throughout the Cenozoic. Because the SO redistributes heat, fresh water, carbon, and nutrients around the global ocean it plays a key role in the climate system. The growth of ice sheets in the Antarctic continent and changes in sea ice in the surrounding ocean are important variables in Earth’s climate system. Upwelling of deep waters in the Antarctic Circumpolar Current (ACC), in particular, is a key process of the meridional overturning circulation (MOC) as it constitutes the return path for deeply-sequestered carbon and nutrients towards the surface and hence important in the partitioning of carbon between the ocean and the atmosphere. Furthermore, physical and biogeochemical processes modulate nutrient export through SO-sourced intermediate waters that ventilate 75% of the world’s thermocline, thus playing a vital role in influencing low-latitude productivity and ecosystems.

The western Indian sector of the SO, located at the confluence of the SO overturning cells and the MOC return surface flow, is a key region to document the links/teleconnections between the SO, global ocean/atmospheric circulations and hence climate (Fig. 1). It provides a unique opportunity to obtain exceptionally high-resolution sediment records to document and unravel the interaction and feedbacks between atmosphere, ocean and cryosphere from millennial to orbital-timescales during the late Neogene and Quaternary, focus on past 6 Ma (Fig. 2).

Specifically, the proposal aims to constrain further – (A) past changes in the upwelling and latitudinal position of the ACC; (B) the dynamic controls of circum-Antarctic deep ocean ventilation/overturning circulation; (C) their link to the global ocean circulation; (D) past changes in the sea ice coverage and dust inputs; and (E) their implications for the marine biogeochemical cycles of carbon and nutrients. The anticipated results will elucidate the evolution of the SO carbon cycle, identify potentially dominant physical and biogeochemical mechanisms of change, document past oceanic bipolar teleconnections with global MOC dynamics, and provide constraints on its future evolution in response to anthropogenic warming.

Our scientific objectives relate to Strategic Objective 3 (Earth’s climate system), Strategic Objective 4 (Feedbacks in the Earth system), and Flagship Initiative 1 (Ground truthing future climate change) in the 2050 Science Framework.

How to cite: Ikehara, M., Crosta, X., Jaccard, S., Naish, T., and Nakamura, Y.: Plio-Pleistocene Southern Ocean Paleoceanography: Latitudinal drilling in the Southwestern Indian sector of the Southern Ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1949, https://doi.org/10.5194/egusphere-egu24-1949, 2024.

International Ocean Discovery Program (IODP) Expedition 366 recovered cores from three serpentinite mud volcanoes that also contain clasts that originate from the subduction-channel along the Philippine Sea Plate – Pacific Plate boundary. The drilled and sampled mud volcanoes (Yinazao, Fantangisña, and Asùt Tesoru) are located at distances of 55 to 72 km from the Mariana Trench.

In general the recovered cores comprise serpentinite mud with lithic clasts from the underlying forearc lithosphere and from the subducting Pacific plate. This aloows the reconstruction of mass transport processes and geochemical cycling within the forearc, the spatial variability of slab-related fluids within the forearc, and water-rock-reactions in subduction and supra-subduction zone settings, the metamorphic and tectonic history of the subduction channel, and the timing and rates of these processes.

Mafic rock clasts, embedded within a serpentine mud matrix, from the flanks and summits of both Asùt Tesoru and Fantangisña Seamounts were analyzed for reconstruction of their metamorphic and deformational overprint in order to reveal the tectono-metamorphic conditions at the metamorphic peak within the subduction channel and the subsequent low-grade overprint during exhumation.

Several seamounts comprise clasts of lower plate metabasites with different metamorphic overprint (from low-grade greenschist facies to lower blueschist facies). The metabasites are also associated with clasts of fossiliferous carbonates and cherts with different degrees of metamorphic and deformational overprint, that also originated from the Pacific lower Plate. This implies that these rocks were exhumed from different depths within the subduction channel before being regurgated within a serpentinite mud matrix. The blueschist facies metamorphic rocks, being affected by metamorphic pressures in the range of 11 to 13.8 kbar at minimum, were very likely exhumed from greater depth within the subduction channel before being captured by uprising, localized serpentine mud flows, indicating evidence that corner flow is actually taking place along the Mariana convergent margin, and, to our knowledge, this is the first direct evidence of exhumation of high-pressure rocks by corner flow in an active subduction zone. Final exhumation, however, is related to the embedding of the rocks within a serpentinite mud matrix and the buoyant ascent of serpentinite mudflows along forearc fracture zones extending from the plate boundary to the upper plate sea floor.

Biostratigraphic analyses of calcareous nannofossils and planktonic foraminifera from serpentinite mud flows, and intercalated pelagic sediments immediately above the metabasites analysed in this study give an age record of ~ 6.10 Ma (late Miocene, Messinian) to 4.20 Ma (early Pliocene, Zanclean), indicating that the final exhumation of the metabasites occurred during late Miocene times, slightly before 6.10 Ma.

How to cite: Kurz, W., Miladinova, I., Auer, G., and Del Gaudio, A. V.: Exhumation of high-pressure rocks by corner flow and serpentinite mud volcanism – implications from serpentinite mud seamounts along the Mariana convergent margin (IODP Expedition 366), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3044, https://doi.org/10.5194/egusphere-egu24-3044, 2024.

EGU24-3074 | Posters on site | ITS5.2/SSP1.13

A new deep sea reference record for the Paleocene-Eocene Thermal Maximum: IODP Expedition 392 Site U1580 (Agulhas Plateau, Southwest Indian Ocean) 

Thomas Westerhold, Steve Bohaty, Donald Penman, Ashely Burkett, and Edoardo Dallanave and the Expedition 392 Scientists

The abrupt onset of the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago represents one of the largest transient greenhouse gas-driven global warming event in the last 100 million years. Caused by a geologically rapid injection of exogenic carbon into the ocean and atmosphere system, the PETM is associated with large-scale ocean acidification. Related widespread dissolution of marine pelagic carbonate deposits, particularly in the early stages of the event, complicates marine paleoclimatic reconstructions and the establishment of robust age models at many sites. Recently, a new deep-sea sediment record spanning the PETM was recovered from the southern Agulhas Plateau in the Southwest Indian Ocean during International Ocean Discovery Program Expedition 392. The uppermost Paleocene/lowermost Eocene interval at Site U1580 was drilled in two parallel holes at 2560 m water depth, and consists of 75‒95% carbonate across the event, with a reduction to 75‒65% at the PETM onset. X-ray fluorescence-derived core scanning elemental data at 5mm and 10mm resolution and an unprecedented high-resolution bulk carbonate stable carbon and oxygen isotope record define a new marine composite reference record for the PETM at this site. The record is comparable to Ocean Drilling Program Site 690 (2914 m water depth) in the Atlantic sector of the Southern Ocean, where the event was first described and is still a primary reference sequence for paleoclimate reconstructions. Unlike Site 690, however, Site U1580 elemental data shows a clear cyclicity throughout the event that can be utilized for cyclostratigraphy. Additionally, the highly resolved bulk carbonate stable carbon isotope record provides a new reference for global correlation, which establishes a new benchmark for the different phases of the PETM. Here we present this new record and discuss the implications for timing and duration of the event, and set the stage for multi-proxy paleoclimate reconstructions spanning the PETM at IODP Site U1580.

How to cite: Westerhold, T., Bohaty, S., Penman, D., Burkett, A., and Dallanave, E. and the Expedition 392 Scientists: A new deep sea reference record for the Paleocene-Eocene Thermal Maximum: IODP Expedition 392 Site U1580 (Agulhas Plateau, Southwest Indian Ocean), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3074, https://doi.org/10.5194/egusphere-egu24-3074, 2024.

EGU24-3380 | Orals | ITS5.2/SSP1.13

Legacy IODP Cores Data in the Era of Big Data 

Cédric M. John

Core data is pivotal for understanding our planet’s past, present, and future. Despite this richness, extracting meaningful insights from core description poses significant challenges due to the inherent complexity and variability of the data, the amount of existing material, and the subjectivity of the interpreter. IODP (and the preceding programs) offers a rich, well labelled source of core images that can be used in machine learning and deep learning.

Focusing largely (but not exclusively) on carbonate rocks, characterized by their heterogeneity at all observational scales, I will discuss how my research group and I have pioneered the application of deep-learning computer vision to geological core interpretation. This technology transcends the traditional, tedious manual interpretations of cores, offering a rapid, and often more accurate, alternative for delineating depositional environments and sequence stratigraphy. Convolutional neural networks (CNNs) form the backbone of our approach, enabling us to process core data with unprecedented efficiency. I will show that these sophisticated models, when correctly trained and fed with substantial datasets, serve as invaluable tools for geologists, outpacing conventional methods in speed without compromising on precision.

Our early work was centred on transfer learning, an AI approach that adapts pre-existing models to new data. I will show that this remains one of the best way to train classification algorithms for geological dataset. But we also worked on generative algorithms that fill gaps in our sampling of core imagery: for instance, we use Generative Adversarial Networks (GANs) to transform the resistivity images from formation micro scanners into representations mirroring actual core photographs, thus enhancing the interpretability for geologists irrespective of their background in downhole tools.

We tackle the often-limiting factor of dataset size in two ways. First, we recourse to generative AI to oversample our training set. Second, we also explore semi-supervised learning techniques.  I will demonstrate that we successfully train models on core deformation images from IODP with minimal labelled data, achieving accuracy on par with, if not exceeding, that of transfer learning models.

None of our achievements would have been possible without the recourse to IODP data. Hence, this presentation serves as a clear illustration of the value of legacy IODP data for future geoscientists.

How to cite: John, C. M.: Legacy IODP Cores Data in the Era of Big Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3380, https://doi.org/10.5194/egusphere-egu24-3380, 2024.

 The ICDP-DSeis (Drilling into Seismogenic zones of M2.0 – M5.5 earthquakes in deep South African gold mines) project recovered rock samples from a fracture zone that hosted the aftershocks of the 2014 Orkney earthquake (M5.5). The fracture zone was formed in an altered lamprophyre dike (Lamprophyre, hereafter) intruded into the Crown Formation (local name of altered basaltic andesite). One of the DSeis holes intersected another dike (named the Onstott dike) ~300 m east of the Lamprophyre. A fissure containing ancient (1.2 Ga) hypersaline brine rich in DOC (dissolved organic carbon) was found in the Onstott dike. The formation and metamorphism of these dikes are discussed in Ogasawara et al. (EGU24). This study describes the frictional properties of Lamprophyre that motivated us to propose a new drilling project PROTEA.

The southern shallowest section of the fault intersected by the DSeis hole did not slip significantly during the Orkney earthquake mainshock, but hosted high aftershock activity. This implies that the fault intersected by the DSeis hole was stable frictionally and decelerated coseismic slip to halt the dynamic propagation of the mainshock rupture. Thereafter, the fault transitioned to an unstable state and produced aftershocks. The recovered rocks revealed the Lamprophyre did not contain any quartz and was rich in talc, biotite, amphibole, and calcite. Loss of drilling water into the fault zone suggested that the pore pressure in the fault zone was low (<6 MPa, water head pressure in the borehole). Consequently, sliding-rate step tests were conducted under wet (saturated, but without pore pressure) condition using the powdered samples to investigate evolution of the frictional property with increasing sliding distance.

 The friction coefficient of Lamprophyre was ~0.3, much lower than that of the Crown Formation (~0.7). The friction coefficients of both lithologies were almost independent of sliding distances. Lamprophyre showed rate-strengthening behavior irrespective of sliding distance. Acoustic emission (AE) activity, which mimics aftershock activity, in the Lamprophyre gouge became higher with increasing sliding distance. This implies a hierarchical evolution of frictional property of Lamprophyre. These experimental results explain the spatial coincidence of the mainshock rupture termination and high aftershock activity.

The weakness of Lamprophyre may enable the formation of a fault in Lamprophyre. However, its rate-strengthening behavior would prevent the nucleation and spontaneous propagation of the rupture on a fault in Lamprophyre. Frictional properties, the stress state, the pore pressure, and/or lithology around the hypocenter should differ from those in the aftershock zone. Therefore, we propose a new drilling project PROTEA (Probing the heart of an earthquake and life in the deep subsurface) to drill a hole targeting the hypocenter and the strong motion source of the Orkney earthquake. It will explore the frictional properties, stress state, pore pressure, and lithology that enabled the nucleation and the initiation of the dynamic rupture, as well as the radiation mechanism of strong motions. PROTEA will drill multiple holes intersecting the Onstott dike, not only to elucidate locality and universality of ecosystems that exist in the fissure brine, but also to investigate the interaction between seismicity and microbial activity.

How to cite: Yabe, Y., Ogasawara, H., and Durrheim, R.: Frictional properties of the fault hosting aftershocks of the 2014 Orkney earthquake (M5.5), South Africa, and proposal of a new drilling project PROTEA to probe the heart of the earthquake, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3723, https://doi.org/10.5194/egusphere-egu24-3723, 2024.

EGU24-4956 | ECS | Posters on site | ITS5.2/SSP1.13

Pretraining Foundation Models: Unleashing the Power of Forgotten Spectra for Advanced Geological Applications 

An-Sheng Lee, Hsuan-Tien Lin, and Sofia Ya Hsuan Liou

X-ray fluorescence (XRF) core scanning, renowned for its high-resolution, non-destructive, and user-friendly operation, is pivotal in geological research for analyzing chemical, physical, and biological signals. Despite the extensive applications of XRF data for various research purposes, the quantification of this data into specific geological proxies remains challenging due to the inherent non-linearity caused by simple sample pretreatment during core scanning. Leveraging advancements in deep learning, computing power and large-scale scientific drilling programs, our study aims to address this non-linearity by harnessing the often-overlooked raw XRF spectra stored in laboratory databases. We introduce an approach involving self-supervised pretraining on 54,643 spectra from marine sediments in the high-latitude sectors of the Pacific Ocean (cruises SO178, SO264, PS97, PS75, LV29). Our model, underpinned by a deep bidirectional image transformer (ViT-base), is trained to reconstruct heavily masked spectra (75%) with an R2 accuracy of 0.996, demonstrating its proficiency in feature extraction from limited data portions. This foundational model is anticipated to serve as a versatile tool for various downstream geological applications after finetuning with specific labeled data, such as quantifying high-resolution calcium carbonate (CaCO3) and detecting machinery anomalies. Future work includes expanding the spectrum database with diverse materials and machine settings to enhance the model's generalizability, ultimately broadening its applicability beyond core scanning for geological applications to encompass all XRF measurement techniques.

How to cite: Lee, A.-S., Lin, H.-T., and Liou, S. Y. H.: Pretraining Foundation Models: Unleashing the Power of Forgotten Spectra for Advanced Geological Applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4956, https://doi.org/10.5194/egusphere-egu24-4956, 2024.

EGU24-5974 | Posters on site | ITS5.2/SSP1.13 | Highlight

Scientific core drilling of the Lower Palaeozoic succession in the Swedish sector of the Baltic Sea – investigation of the CO2 storage potential 

Mikael Erlström, Jan-Erik Rosberg, Peter Dahlqvist, Carl-Erik Hjerne, and Henning Lorenz

With an aggregated thickness of c.100 m, a porosity of up to 15 % and a permeability above hundred millidarcy, previous studies have assessed the three widely distributed Cambrian sandstone members in the Swedish sector of the Baltic Sea as the most potential CO2-storage candidates in Sweden. Existing models indicate an effective storage capacity between 450–1500 Mt CO2. However, these rough numbers are uncertain as they are related to vintage and partly inadequate data sets, especially regarding physical property values needed for a more certain evaluation of the storage capacity. Hence, as part of a larger screening and evaluation programme, launched by the Swedish government to identify and quantify potential storage sites in Sweden, two scientific core drillings were completed in 2023 on the southernmost part of the island of Gotland in the Baltic Sea. The primary aim was to collect complementary and missing data on the Lower Palaeozoic succession including both caprocks and reservoirs. The scientific evaluations and results of the core drillings on south Gotland will together with geophysical logging of the boreholes, new seismic data and 3D models constitute an essential part in improving the models of the effective storage capacity of the Cambrian reservoirs in the Swedish sector of the Baltic Sea. The coring, monitoring and investigations were managed by the Geological Survey of Sweden and the Swedish national research infrastructure for scientific drilling, “Riksriggen”, operated by the department of Engineering Geology at Lund university. H-dimension triple tube coring (96/61 mm hole/core diameter) was successfully performed with an Atlas Copco CT20C rig. The two wells, Nore-1 and Nore-2, penetrate 470 m of Silurian marlstone and claystone, 85 m of Ordovician argillaceous limestone and 225 m of Cambrian sandstone, siltstone and shale before finishing in the Precambrian crystalline basement of potassium porphyritic granite at 791.5 m and 787.7 m, respectively. The operation managed to reach the set goals despite challenges of over pressured formations and up to metre-thick bentonites. Initial results show a thick, tight, and homogenous caprock and that the Faludden Sandstone, one of the three Cambrian sandstone members, have hydraulic properties that qualifies it as a possible storage reservoir. The preliminary results from the two wells are here presented together with evaluations of drilling performance, monitoring programme, logging and test operations. 

How to cite: Erlström, M., Rosberg, J.-E., Dahlqvist, P., Hjerne, C.-E., and Lorenz, H.: Scientific core drilling of the Lower Palaeozoic succession in the Swedish sector of the Baltic Sea – investigation of the CO2 storage potential, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5974, https://doi.org/10.5194/egusphere-egu24-5974, 2024.

We have detected an event of pore pressure changes (hereafter, we refer it to “pore pressure event”) from borehole stations in real time in March 2020 and March 2023, owing to the network developed by connecting three borehole stations to the Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) observatories near the Nankai Trough. Slow earthquake is thought to have longer duration time with smaller stress drop than regular earthquake under the same magnitude. This means that the slow earthquake is more sensitive to external stress perturbation and useful to monitor the processes of stress accumulation and release. However, the pore pressure is also affected by tidal and oceanic fluctuations. To overcome this problem, we use the seafloor pressure gauges of DONET stations nearby boreholes instead of the reference by introducing time lag between them. The obtained results demonstrate the detectability of volumetric strain change for nano-scale. We also investigate the impact of seafloor pressure due to ocean fluctuation on the basis of ocean modelling, which suggests that the decrease of effective normal stress from the onset to the termination of the SSE is explained by Kuroshio meander and may promote updip slip migration, and that the increase of effective normal stress for the short-term ocean fluctuation may terminate the SSE as observed in the Hikurangi subduction zone. The evaluation of the ocean impact is to be applied to a fiber-optic submarine cable, and 50 km-long distributed acoustic sensing (DAS) recordings, where the DAS measurement can be sensitive for hydroacoustic signals in a frequency range from 0.1 to a few tens of Hz.

How to cite: Ariyoshi, K. and Matsumoto, H.: Precise monitoring of subduction plate coupling status on the basis of DONET and borehole data analyses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7109, https://doi.org/10.5194/egusphere-egu24-7109, 2024.

EGU24-7120 | Posters on site | ITS5.2/SSP1.13

Chemical-Based Event-Stratigraphic Correlation along the Japan Trench by XRF-CS Chemical Fingerprint and Multivariate Statistics 

Jun-Ting Lin, Jyh-Jaan Huang, Ken Ikehara, Michael Strasser, Ta-Wei Hsu, Chih-Chieh Su, Yu-Hsun Shao, Yen-Hsi Wu, and Astuko Amano

Megathrust earthquakes in subduction zones, such as the AD 2011 Tohoku-oki earthquake, are known to generate turbidity currents that transport sediment into deep marine trenches, creating distinctive event deposits. These deposits are pivotal in submarine paleoseismology, which seeks to extend earthquake records and assess disaster potentials by meticulously analyzing the spatiotemporal distribution of these deposits through precise distinction and correlation. In our research, over 800 meters of sediment cores from 15 sites along the Japan Trench were collected during the International Ocean Discovery Program (IODP) Expedition 386, focusing on these event deposits to trace earthquake history. Utilizing X-ray Fluorescence Core Scanning (XRF-CS), we performed efficient and non-destructive high-resolution analysis of the chemical characteristics of these deposits. Our methodology integrates XRF-CS data with multivariate statistical techniques, such as Principal Component Analysis (PCA) and Cluster Analysis (CA). This integration enables us to objectively differentiate and correlate event deposits based on their unique chemical properties. Significant discoveries were made at Site M0083, where we detected variations in background sediments and event deposits associated with major historical earthquakes, including the AD 1454 Kyotoku and AD 869 Jogan events. These unique chemical fingerprints were also traced to adjacent trench-fill basins at sites M0089 and M0090, revealing consistent event-stratigraphic sequences across the basins and affirming the efficacy of our chemical-based correlation technique. In our ongoing analysis, we aim to explore the diverse chemical fingerprints of background sediments, turbidite bases, and turbidite tails. This investigation seeks to uncover potential spatial and stratigraphic provenance changes, and includes examining mineral and biogenic compositions, such as clay minerals and smear slides, to elucidate the reasons behind variations in chemical signals. Our findings underscore the effectiveness of combining chemical analysis with statistical methods for event-stratigraphic correlation. This novel approach not only sheds light on provenance changes but also helps establish a detailed spatiotemporal distribution framework for event deposits along the Japan Trench. Moreover, this integrated methodology could inform subsequent sampling strategies by objectively selecting sampling locations based on the chemostratigraphy framework. It also has the potential to be adapted to other research areas that require event-stratigraphic correlation and comprehensive spatiotemporal analysis.

How to cite: Lin, J.-T., Huang, J.-J., Ikehara, K., Strasser, M., Hsu, T.-W., Su, C.-C., Shao, Y.-H., Wu, Y.-H., and Amano, A.: Chemical-Based Event-Stratigraphic Correlation along the Japan Trench by XRF-CS Chemical Fingerprint and Multivariate Statistics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7120, https://doi.org/10.5194/egusphere-egu24-7120, 2024.

EGU24-8374 | ECS | Posters on site | ITS5.2/SSP1.13

Advantages of DTW windowing function in automated correlation of stratigraphic time series 

Rohit Samant, Toni Giorgino, Emilia Jarochowska, and David De Vleeschouwer

The Dynamical Time Warping (DTW) technique has been originally developed for speech recognition in the late 1960s and early 1970s and has more recently been applied in geoscientific studies. One of the key objectives of dtw is to stretch or compress two complementary series locally in order for one series to resemble the other as much as possible. In our project, we aim to correlate industrial and scientific downhole wireline logs from offshore Australia, with the ultimate goal to obtain a regional paleoclimate reconstruction at high spatial resolution (“All around Australia”). Here, we propose a novel way to constrain the alignment of two sedimentary sequences based on a-priori stratigraphic information. Therewith, we provide a means to make dtw calculations less computationally expensive, while still evaluating all possible stratigraphic correlations, even for long time-series.

The “All around Australia” project focuses on the automated correlation of thousands of scientific and industrial time-series. Hence, it is important to speed up the calculations and reduce the computational costs. The global constraint on dtw, also known as the window function, speeds up the calculations by limiting the 2-dimensional space of possible alignments between two time-series. As a case study, IODP Site U1463 (Northwest Shelf of Australia) serves as the reference to which two industrial sites (Finucane-1 and Angel-2) are correlated. Biostratigraphic datums of Site U1463 have few meters of depth uncertainty. Their corresponding depths at the industrial sites are manually determined, albeit with a depth uncertainty that is one order of magnitude higher (so-called “slack”).  These manually determined correlation points are then utilized to create custom-made windows, reflecting a priori knowledge of the large-scale stratigraphy of the studied basin. In this case, the comparison of the computational time and the goodness-of-fit for ‘no-window’ and ‘windowed’ dtw calculations reveals that the quality of the correlation improves and computational time is reduced by 15-20%. Hence, the novel window function is primarily useful for stratigraphers to guide the dtw algorithm in creating warping paths that are stratigraphically more plausible. 

How to cite: Samant, R., Giorgino, T., Jarochowska, E., and De Vleeschouwer, D.: Advantages of DTW windowing function in automated correlation of stratigraphic time series, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8374, https://doi.org/10.5194/egusphere-egu24-8374, 2024.

EGU24-11720 | ECS | Orals | ITS5.2/SSP1.13

IODP Expedition 398 Reveals a Major Normal Fault along the Kolumbo Volcanic Chain 

Jonas Preine, Christian Hübscher, Abigail Metcalfe, Katharina Pank, Adam Woodhouse, Olga Koukousioura, Shun Chiyonobu, Timothy Druitt, Steffen Kutterolf, Paraskevi Nomikou, Thomas Ronge, Sarah Beehte, Miachel Manga, Iona McInsoth, Masako Tominga, Gareth Crutchley, and Jens Karstens and the IODP Expedition 398 Scientists

 

Many hazardous volcanic systems worldwide are located in extensional back-arc systems, where the crust is influenced by pervasive faulting. However, our knowledge about the spatial and temporal relationship between crustal faults and the emplacement of volcanic edifices is immature. Located on the South Aegean Volcanic Arc, the Christiana-Santorini-Kolumbo volcanic field formed in a continental rift zone and represents an ideal natural laboratory to study the structural interaction between volcanism and tectonism. From December 2022 to February 2023, IODP Expedition 398 drilled 12 sites across the volcanic rift system. We will present the results of core-seismic integration of several sites from the rift basins. Two of these drill sites lie on the hanging wall and footwall of the Kolumbo Fault, respectively. This fault strikes parallel to the Kolumbo Volcanic Chain and was previously considered a fault with little vertical offset. However, tephra and biostratigraphic markers identified in recovered cores from IODP Expedition 398 indicate a major vertical offset of >200 m (~260 ms TWT) along this fault. Seismic data reveal that this fault is a major NE-SW-directed normal fault and represents an important structural element of the rift system but subsequent rapid sedimentation of volcanoclastic material buried this fault. The volcanic edifices of the Kolumbo Volcanic Chain formed on the hanging wall of this fault at a distance of approx. 6 km from the surface trace. Adjacent, non-volcanic rift basins show pervasive internal fault zones at a similar distance from the respective basin-bounding faults, indicating that these faults may be the preferred pathway for magma to reach the surface. Our study implies a fundamental tectonic control of the emplacement of volcanoes at the Christiana-Santorini-Kolumbo volcanic field, a process that might be present at other back-arc systems.

How to cite: Preine, J., Hübscher, C., Metcalfe, A., Pank, K., Woodhouse, A., Koukousioura, O., Chiyonobu, S., Druitt, T., Kutterolf, S., Nomikou, P., Ronge, T., Beehte, S., Manga, M., McInsoth, I., Tominga, M., Crutchley, G., and Karstens, J. and the IODP Expedition 398 Scientists: IODP Expedition 398 Reveals a Major Normal Fault along the Kolumbo Volcanic Chain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11720, https://doi.org/10.5194/egusphere-egu24-11720, 2024.

EGU24-12110 | Posters on site | ITS5.2/SSP1.13

A legacy plan and an innovative access framework for the next decades of Italian geoscientists involved in scientific drilling: the role of ECORD/IODP-Italy in the ITINERIS project 

Annalisa Iadanza, Andrea Argnani, Chiara Boschi, Angelo Camerlenghi, Giulia Casalena, Elisabetta Erba, Fabio Florindo, Biagio Giaccio, Hanno Kinkel, Marco Sacchi, Andrea Schleifer, Riccardo Tribuzio, and Paola Vannucchi

In the framework of the Research Infrastructures (RIs), scientific drilling represents a globally ranging, distributed RI that generates a wide variety of subsurface data. The ongoing project “Italian Integrated Environmental Research Infrastructures System (ITINERIS)” aims at building the Italian Hub of RIs in the environmental scientific domain by coordinating a network of national nodes from 22 RIs, including the Italian participation in the European Consortium for Ocean Research Drilling (ECORD) and in the International Continental Scientific Drilling Project (ICDP). The main goal of ITINERIS is to promote cross-disciplinary research in environmental sciences through the use and re-use of existing (or pre-operational) data and services and new observations, and to address scientifically and societally relevant issues.

The impact of ITINERIS on the Italian geoscientists involved in scientific drilling is twofold. First, it will improve the access to both the ECORD and the ICDP infrastructures. This will result in increasing the national participation in terms of proposal writing, drilling expeditions/projects, initiatives to use legacy samples/data, and training activities. Secondly, it will allow to collect and systematize the great amount of data produced by Italian scientists in the past scientific drilling programs (DSDP-ODP-IODP). This will facilitate the data handling and interoperability approach. A thematic digital archive of ECORD/ICDP-related data will be provided within the following thematic areas: micropaleontology, petrology, elemental and isotope geochemistry, paleomagnetism, stratigraphy/lithology, structural geology, borehole geophysics and site survey. This structured and accessible scientific dataset will represent a milestone for further implementation following FAIR data principles and best practices for ongoing and future drilling projects. Further developments of this digital archive might also serve as an additional tool to be integrated within the SPARCs initiative of IODP3.

How to cite: Iadanza, A., Argnani, A., Boschi, C., Camerlenghi, A., Casalena, G., Erba, E., Florindo, F., Giaccio, B., Kinkel, H., Sacchi, M., Schleifer, A., Tribuzio, R., and Vannucchi, P.: A legacy plan and an innovative access framework for the next decades of Italian geoscientists involved in scientific drilling: the role of ECORD/IODP-Italy in the ITINERIS project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12110, https://doi.org/10.5194/egusphere-egu24-12110, 2024.

EGU24-13796 | Orals | ITS5.2/SSP1.13

Using the LIMS with Lithology (LILY) Database to Probe IODP Density, Porosity, and P-Wave Velocity Data 

Gary Acton, Laurel Childress, and Vincent Percuoco

We use the LIMS With LithologY (LILY) database compiled by Childress et al. (https://zenodo.org/records/8408297) to examine relationships between physical properties and the lithology of marine drill cores collected by the International Ocean Discovery Program (IODP) and its precursor program between 2009 and 2019. Within LILY, lithologic information such as the principal lithologic name and the major and minor lithologic modifiers, along with other metadata, have been added to each of the more than 34 million observations from the standard data available in IODP’s LIMS Database, which is accessible through the LIMS Online Reports (LORE) portal (web.iodp.tamu.edu/LORE/). The ability to compare and combine descriptive lithologic information across expeditions and to integrate these descriptions with multisensor track and discrete sample measurements allows for a wealth of scientific investigation not possible under the original data structure. One of the obvious values of LILY is the ability to characterize the basic physical, chemical, and magnetic properties of different lithologies from a very large number of observations. As an example of this, we compute grain densities for all available lithologies using the Moisture and Density (MAD) density data from over 24,000 measurements. Once the grain densities are known, then the bulk densities can be used to determine porosity. This is important because besides the over 24,000 MAD bulk densities, there are 3.7 million gamma ray attenuation (GRA) bulk densities measured by the Whole Round Multi-Sensor Logger (WRMSL). Comparison of MAD and GRA bulk densities permits biases in the GRA density dataset to be corrected. These corrected GRA bulk densities are then used to compute a new high-resolution porosity dataset (https://zenodo.org/records/10001855). We further merge this large bulk density and porosity dataset with the P-wave velocity data from a P-wave Logger that is part of WRMSL, a P-wave Caliper, and P-wave Bayonets to characterize lithologic-dependent relationships between density, porosity, and P-wave velocity.

How to cite: Acton, G., Childress, L., and Percuoco, V.: Using the LIMS with Lithology (LILY) Database to Probe IODP Density, Porosity, and P-Wave Velocity Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13796, https://doi.org/10.5194/egusphere-egu24-13796, 2024.

EGU24-14233 | Posters on site | ITS5.2/SSP1.13

From DSeis to PROTEA - Probing the heart of an earthquake, especially the interaction between metasedimentary rocks and mantle-derived intrusions.  

Hiroshi Ogasawara, Yasuo Yabe, Raymond Durrheim, Musa Manzi, Thomas Kieft, Devan Nisson, Julio Castillo, Alba Gómez-Arias, Bennie Liebenberg, and Team DSeis and PROTEA

The ICDP DSeis project accomplished full-core drilling and borehole-logging of the seismogenic zone of the 2014 M5.5 Orkney earthquake, South Africa. Three NQ-holes (total 1.6 km in length), drilled from 2.9 km depth at the Moab Khotsong gold mine, penetrated mostly intact hard rock, including 2.9 Ga meta-sedimentary and altered andesite (Crown) formations dipping ~20°SE. Subparallel altered gabbroic diorite sills intrude the formations.

After the borehole penetrated the Crown Formation and approached the steeply-dipping planar cluster of earthquake aftershocks, it encountered a potassic lamprophyre dyke several meters thick. The lamprophyre was intact close to the dyke contact, with mineral assemblages of augite, actinolite, and biotite. The talc and calcite content and magnetic susceptibility increased towards the centre of the dyke, while the augite and actinolite content decreased. The lamprophyre rock mass then became brecciated, with a substantial fraction of gouge. The Crown Formation adjacent to the dyke contact was also brecciated. Friction tests made on lamprophyre gouge (which contains about 20 wt% talc) yielded very low friction coefficients, similar to the results of previous wet friction experiments (Yabe et al. EGU 2024).

The DSeis drilling also intersected a non-potassic dyke rich in actinolite and chamosite about 300 m east of the potassic lamprophyre dyke. Whilst this dyke hosted no indications for aftershocks, the extracted brine was more hypersaline and older than any brine previously sampled from deep South African gold mines (Nisson et al., 2023). The hypersaline brine was non-meteoric in composition, with dissolved organic carbon concentrations sufficient to support deep life.

Both dykes show significant spatial variation in composition which we attributed to contamination/assimilation and metamorphism, depending on which formations (~20°SE dip) the dykes cut. We postulate that the localization of aftershocks in ‘streaks’ subparallel to the strata is a result of this compositional heterogeneity.

DSeis has successfully penetrated, sampled, and studied the aftershock sequence on the upper edge of the Orkney earthquake rupture. However, important questions regarding the nucleation and rupture of the earthquake that will only be solved by studying the strong motion source of the mainshock. The proposed PROTEA scientific drilling project aims to probe the Orkney earthquake's strong motion sources (the heart).

The existing DSeis hole, the new PROTEA hole, and the connecting horizontal tunnels at 2.9 km depth will allow us to deploy a 3D distributed acoustic sensing (DAS) network with a vertical span of several hundreds of meters, and a horizontal span of about 1 km. Using both active and passive seismic sources, we expect to image the 3D structure of the reflectors precisely.

Moab Khotsong has offered the team access to borehole cores that have sampled numerous dykes and sills; as well as access to the database of lithology and geological structure mapped on the mining horizons at 2-3 km depth. These data cover a much broader volume than the DSeis and PROTEA projects, and will significantly extend and enhance the interpretation.

Acknowledgements: South African gold mines, related firms, SATREPS, Kakenhi (21224012), ICDP, JSPS Core-to-Core Program, MEXT Kochi Core Center, NSF, DFG, NRF, Ritsumeikan and Kyoto Univs.

How to cite: Ogasawara, H., Yabe, Y., Durrheim, R., Manzi, M., Kieft, T., Nisson, D., Castillo, J., Gómez-Arias, A., Liebenberg, B., and DSeis and PROTEA, T.: From DSeis to PROTEA - Probing the heart of an earthquake, especially the interaction between metasedimentary rocks and mantle-derived intrusions. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14233, https://doi.org/10.5194/egusphere-egu24-14233, 2024.

EGU24-14690 | Posters on site | ITS5.2/SSP1.13 | Highlight

SVALCLIME – Targeting deep-time Arctic climate archives of Svalbard 

Denise K. Kulhanek, Valentin Zuchuat, Morgan Jones, Jiri Barta, William J. Foster, Wolfram H. Geissler, Sten-Andreas Grundvåg, Henning Lorenz, Sverre Planke, Kim Senger, Grace Shepherd, Kasia K. Sliwinska, Aleksandra Smyrak-Sikora, Lidya G. Tarhan, Madeleine Vickers, Maximilian Weber, Weimu Xu, and Daniel Kramer

The Svalbard archipelago, located in the Norwegian High Arctic, preserves more than 650 million years of near-continuous sedimentary rock records spanning from the Neoproterozoic to the Cenozoic. The polar paleogeographic location of Svalbard in the late Mesozoic and the Cenozoic makes sites in Svalbard unique amongst well-studied temporally equivalent successions from lower paleolatitudes, allowing investigation of the polar amplification climatic effect over geological time. The sedimentary record of Svalbard has been largely controlled by northward drift of constituent geological provinces throughout much of the Phanerozoic and evolving tectono-stratigraphic environments including the influence of several Large Igneous Provinces (LIPs) and global climate fluctuations. 

The SVALCLIME initiative aims to systematically drill and core the sedimentary successions in Svalbard. Two sub-projects currently being evaluated by the ICDP materialized from an international workshop held in Longyearbyen in October 2022. The first is a full ICDP proposal focused on hyperthermals from the Permian to Paleogene (SVALCLIME P2P) and an ICDP-IODP Land to Sea preproposal on hothouse to coldhouse transitions in the late Paleozoic and across the Eocene–Oligocene transition (SVALCLIME Hot2Cold).

The SVALCLIME P2P project aims to investigate the high-resolution Arctic paleoclimate record from 255 to 45 Ma onshore Svalbard that encompasses several Mesozoic and Cenozoic hyperthermal events and the near-field impacts of three LIPs (the Siberian Traps, the High Arctic LIP and the North Atlantic Igneous Province). Our focus will also be on the deep biosphere to uncover the relationship between mineral substrates and taxonomic and metabolic diversity of intraterrestrial microbiomes. We propose to core seven boreholes at three locations (Nordenskiöldfjellet, Botneheia and Kropotkinfjellet), with a cumulative total cored length of ~3.4 km. 

The SVALCLIME Hot2Cold project aims to address global transitions from hothouse to icehouse conditions during the late Paleozoic and the Eocene to Oligocene. In the preproposal we identify suitable drill sites both onshore and offshore to characterize these periods. The Forlandsundet Graben in western Spitsbergen offers an opportunity to decipher the evolution of the Fram Strait and its impact on global oceanographic circulation during the Eocene–Oligocene transition. The Upper Carboniferous to Early Permian syn and post-rift deposits of the Billefjorden Trough will be targeted to investigate >130 cyclothems originating from glacioeustatic sea level fluctuations.

In this contribution, we outline the background and motivation of the SVALCLIME initiative and present the scientific objectives and the proposed drill sites.

How to cite: Kulhanek, D. K., Zuchuat, V., Jones, M., Barta, J., Foster, W. J., Geissler, W. H., Grundvåg, S.-A., Lorenz, H., Planke, S., Senger, K., Shepherd, G., Sliwinska, K. K., Smyrak-Sikora, A., Tarhan, L. G., Vickers, M., Weber, M., Xu, W., and Kramer, D.: SVALCLIME – Targeting deep-time Arctic climate archives of Svalbard, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14690, https://doi.org/10.5194/egusphere-egu24-14690, 2024.

EGU24-15118 | ECS | Orals | ITS5.2/SSP1.13

Integrated interpretation of downhole geophysical measurements of the Lower Continental Crust in the Ivrea-Verbano Zone (Western Alps, Italy) at the DIVE DT-1B borehole 

Junjian Li, Eva Caspari, Andrew Greenwood, Simona Pierdominici, Marco Venier, Mattia Pistone, Kim Lemke, György Hetényi, and Luca Ziberna

The Drilling the Ivrea-Verbano zonE (DIVE) project completed its first borehole DT-1B in December 2022, recovering a continuous drill core to 578.5 m depth. The objective of DT-1B is to explore the upper part of the Lower Continental Crust. The 100% core recovery provides an excellent opportunity to integrate downhole geophysical measurements with core observations in rarely drilled lithologies. The primary goal of this integrated study is to characterize the rock mass and constrain the factors that influence seismic velocity variations and the origin of reflectivity in lower crustal rocks. For this purpose, we have collected a comprehensive suite of downhole measurements, comprising of natural gamma ray, magnetic susceptibility, dual laterolog resistivity, single point resistance, mud parameter, full waveform sonic, acoustic and optical televiewer, and vertical seismic profiling data. Complementary bulk density measurements have been performed on 96 core sections with a multi-sensor core logger as well as laboratory ultrasonic velocity and bulk density measurements on 15 selected core samples at ambient conditions. To characterize the rock mass mechanically and structurally, a detailed analysis of the acoustic televiewer data was carried out, which identified several natural and drilling-induced fractures. Natural fractures have two predominant azimuthal orientations: NW to NE and SSE to SE. Their dips range from 10° to 85°, with a higher average dip in the upper section that decreases in the lower section of the borehole. Fractures correlate with an abundance of anomalies in the electrical logs and affect sonic velocities. Due to the impact of fractures on these logs, only natural gamma ray and magnetic susceptibility logs are used for lithological classification of the rock masses, into three distinct clusters by fuzzy c-means clustering. Two of the clusters, 1 and 3, are attributed mainly to felsic metasediments, while cluster 2 is attributed to metamafics identified in the cores. Cluster 1 is characterized by high magnetic susceptibility and natural radiation, while cluster 3 is characterized by low magnetic susceptibility and natural radiation, indicating two distinct groups of metasediments. Concerning the elastic properties, it is expected that the velocities of the metamafics are higher than those of the metasediments. However, a systematic correlation between velocities and lithologies (or clusters) is not observed. To investigate the factors contributing to seismic velocity variations, velocities from core measurements, sonic logging, and vertical seismic profiling are compared. The velocities are consistent across the three scales, with P-wave velocities ranging from 5 to 6 km/s and S-wave velocities around 3 km/s, however, the values are much lower than expected. One reason might be the presence of microcracks, as indicated by the P-wave velocity difference between saturated and dry core samples. Together with the observed impact of fractures on the sonic log data, this suggests that the velocities are governed by brittle deformation at various scales, which explains their low values and overprints the lithological response. Consequently, reflections are expected to be caused by large scale fractures, but lithological reflections may still be observed due to the density contrast between metasediments and metamafics.

How to cite: Li, J., Caspari, E., Greenwood, A., Pierdominici, S., Venier, M., Pistone, M., Lemke, K., Hetényi, G., and Ziberna, L.: Integrated interpretation of downhole geophysical measurements of the Lower Continental Crust in the Ivrea-Verbano Zone (Western Alps, Italy) at the DIVE DT-1B borehole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15118, https://doi.org/10.5194/egusphere-egu24-15118, 2024.

EGU24-16278 | Orals | ITS5.2/SSP1.13

A million years of regional hydroclimate oscillations in West Africa reconstructed from Lake Bosumtwi 

Mathias Vinnepand, Christian Zeeden, Thomas Wonik, William Gosling, Anders Noren, Jochem Kück, Simona Pierdominici, Silke Voigt, Mehrdad Sadar-Abadi, Arne Ulfers, Sylvester Danour, Kweku Afrifa, and Stefanie Kaboth-Bahr

Situated within a 1.07 million-year-old meteorite crater, Lake Bosumtwi in Ghana stands as a pivotal location for comprehending fluctuations in the hydro-climatic situation in sub-Sahara West Africa. The region is highly sensitive to climate oscillations due to the movements of the tropical rain belt driven by atmospheric circulation leading to pronounced dry or wet conditions on seasonal to orbital scales. Considering that climatic changes may trigger severe socio-economic crises in this area due to negative impacts on the agricultural sector- especially the cacao farming, a better understanding on the responses of the regional hydro-climatic situation to global warming tendencies is crucial. Recently a robust age-depth model was developed for the lacustrine sequence of Lake Bosumtwi, the only continental record spanning the last million years in West Africa. This provides the unique opportunity to gain detailed insights into the hydroclimatic situation. Yet, the natural gamma radiation (NGR) signal that we interpret as a proxy for terrestrial sediment input throughout the 300 m thick record, triggered by fluvial in wash from the crater rims, shows quasi-cyclic patterns. Based on this along with evidence from additional proxies, we discuss these patterns at Lake Bosumtwi and their relation to orbital forcing including fluctuations in the hydroclimate.

How to cite: Vinnepand, M., Zeeden, C., Wonik, T., Gosling, W., Noren, A., Kück, J., Pierdominici, S., Voigt, S., Sadar-Abadi, M., Ulfers, A., Danour, S., Afrifa, K., and Kaboth-Bahr, S.: A million years of regional hydroclimate oscillations in West Africa reconstructed from Lake Bosumtwi, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16278, https://doi.org/10.5194/egusphere-egu24-16278, 2024.

EGU24-16452 | Orals | ITS5.2/SSP1.13

ReC23-01 – Initial Results of the first KCC-J-DESC Repository Core Re-Discovery Program (ReCoRD) 

Gerald Auer, Junichiro Kuroda, Yusuke Kubo, Or Mordecai Bialik, Anna Joy Drury, Beth Christensen, Arisa Seki, Theresa Nohl, Jumpei Yoshioka, Xabier Puentes Jorge, Tamara Hechemer, Jing Lyu, An-Sheng Lee, Natsumi Okutsu, David De Vleeschouwer, Werner E Piller, and Minoru Ikehara

In 2023, the ReCoRD program was initiated by a joint venture of the Kochi Core Center (KCC), Kochi University and the Japan Drilling Earth Science Consortium (J-DESC) as a new workshop type, providing access to IODP cores archived at the KCC in Kochi, Japan. The first ReCoRD workshop, ReC23-01, ”Tracing Intermediate Water Current Changes and Sea Ice Expansion in the Indian Ocean”, was held between the 27th of August and the 5th of September 2023 at the KCC in Kochi. The goals of ReC23-01 were to gather new data to test the hypothesis that the expansion of sea ice around Antarctica impacted water circulation in the Indian Ocean through changes in intermediate water formation and the northward expansion of the Antarctic polar front through the Middle to Late Miocene following the Middle Miocene Climatic Transition (< 13.8 Ma).

During ReC23-01, we targeted a latitudinal transect from the high southern latitudes to the tropical Indian Ocean consisting of 1 DSDP and 2 ODP sites. DSDP Site 266 represents the high-latitude target site located just south of the present-day location of the polar front. Data gathered for Site 266 during ReC23-01 is a new tracer location for ice-rafted debris (IRD) accumulation and changes in the Southern Hemisphere frontal system for the Neogene in the Indian Ocean. ODP Site 752 on the Broken Ridge provides a unique record of mid-latitude intermediate water paths, including SAMW and AAIW originating from the high latitudes and the Tasman Leakage. ODP Site 707 represents a critical end member of the south equatorial current and related Indonesian Intermediate Waters in the tropical Indian Ocean.

The ReC23-01 workshop within the ReCoRD program allowed international research collaborators to fully benefit from the legacy of over 50 years of International Ocean Drilling Research from the Deep Sea Drilling Program (DSDP), Ocean Drilling Program (ODP), and International Ocean Discovery Program (IODP). Combining in-tandem sedimentological core descriptions with existing and new core data provides a unique opportunity to re-investigate and evaluate archived (legacy) core material. In particular, the availability of computer tomography (CT) core images provided critical information in assessing sedimentology and drilling disturbance in older DSDP and ODP core material to gather new data from over 50-year-old cores.

ReC23-01 illustrates how ReCoRD-style workshops can offer a new way to explore research questions that could not be easily addressed by single sea-going expeditions. These workshops provide additional and powerful research opportunities based on legacy core material beyond individual sample and data requests, with large-scale community benefits. For instance, ReC23-01 provided an excellent training opportunity for early career researchers in a shipboard-like setting.

How to cite: Auer, G., Kuroda, J., Kubo, Y., Bialik, O. M., Drury, A. J., Christensen, B., Seki, A., Nohl, T., Yoshioka, J., Puentes Jorge, X., Hechemer, T., Lyu, J., Lee, A.-S., Okutsu, N., De Vleeschouwer, D., Piller, W. E., and Ikehara, M.: ReC23-01 – Initial Results of the first KCC-J-DESC Repository Core Re-Discovery Program (ReCoRD), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16452, https://doi.org/10.5194/egusphere-egu24-16452, 2024.

EGU24-16500 | Orals | ITS5.2/SSP1.13

IODP Expeditions 384/395C/395: Reykjanes Mantle Convection and Climate. Preliminary results 

Anne Briais, Ross Parnell-Turner, and Leah LeVay and the Expedition 395 Science Party

International Ocean Discovery Program Expeditions 384, 395C and 395 investigated the interactions between variations in the Iceland hotspot activity, ocean crust formation at the Reykjanes Ridge, ocean circulation, and climate in the North Atlantic, and sediment drift deposition on the flanks of the mid-ocean ridge. Variations in crustal production along the Reykjanes Ridge produced V-shaped ridges and troughs located on the flanks of the mid-ocean ridge, and the role of the Iceland hotspot in their generation is debated. Changes in hotspot activity, and therefore in the associated dynamic topography, likely influenced the depth of the oceanic gateways formed by the Greenland-Scotland Ridge between the North Atlantic and the Norwegian and Arctic Seas. Such variations might thus have controlled the strength of cold, deep water currents, and the accumulation rate of sediment drifts on the flanks of the ridge: Björn and Gardar drifts on the eastern flank and Eirik drift to the west. Expeditions 384 in 2020, 395C in 2021, and 395 in 2023 collected cores from a transect of five drill sites along a plate-spreading flowline spanning seafloor ages from 2.8 to 32 Ma and crossing Björn and Gardar drifts on the eastern ridge flank, as well as a sixth site along the eastern Greenland margin crossing Eirik drift. Combined, over 400 m of oceanic basalt and over 5.8 km of sediment core was recovered, including continuous records through key Pleistocene and Pliocene sequences, and a unique record of progressive basalt alteration. Here we present preliminary results of the expedition, featuring new insights into crustal accretion variations through time, constraints on the onset of sedimentation at Björn, Gardar and Eirik contourite drifts, and new records of climatic cycles on thousand-year timescales. These sites also provide a unique view on how crust interacts with fluids and sediment over millions of years, while in-situ samples obtained from the cores yield insights into chemical exchanges and microbial systems in the ocean, sediment, and crust. The vast amount of sediments, basalts and measurements collected during Expeditions 384, 395C and 395 will provide a major advance in our understanding of mantle dynamics and the linked nature of Earth’s interior, oceans, and climate.

How to cite: Briais, A., Parnell-Turner, R., and LeVay, L. and the Expedition 395 Science Party: IODP Expeditions 384/395C/395: Reykjanes Mantle Convection and Climate. Preliminary results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16500, https://doi.org/10.5194/egusphere-egu24-16500, 2024.

EGU24-17124 | ECS | Posters on site | ITS5.2/SSP1.13

Seismic while drilling with a diamond drill bit in project DIVE DT-1B borehole in the Ivrea-Verbano Zone (Western Alps, Italy) 

Bernd Trabi, Andrew Greenwood, and Florian Bleibinhaus

A unique Seismic While Drilling (SWD) experiment, whereby a diamond coring drill rig as the seismic source has been conducted in the Val d’Ossola, Western Alps, Italy. For the SWD experiment 64 3C-sensors are employed in an array at the surface and the vibrational action of coring the rock acts as an active seismic source within the borehole. The maximum offset of the sensor array is 480 m with non-uniform spacing that increases with distance. The drilling operation took place from early October until mid-December 2022 and reached a depth of approximately 580 m. The seismic sensors recorded at a sampling rate of 1 ms, which is more than sufficient for an expected frequency of up to 200 Hz. The proposed SWD experiment is to evaluate the potential and limitations of the SWD method for diamond core drilling commonly utilized in scientific drilling projects with a focus on fundamental developments of the methodology and data processing techniques. Ideally the drill-bit seismic record should produce a seismic image around the bore hole and ahead of the drill bit. First it is important to determine if a signal can be detected, and to what depth, from a diamond core drill bit. In contrast to percussion or reverse circulation drilling, the diamond core drilling method produces a very weak signal. The seismic data is also heavily contaminated by coherent and random noises generated at the drill site, including rig engines, generators and mud-pumps, vehicles, and the movement of equipment. Separation of theses coherent noises using radon transform has thus far failed and other wavefield separation methods are investigated. Using seismic interferometric methods for unknown source positions, we aim to detect the weak signal at known drill bit positions. This is promising especially at drilling depths where the drill-rig and drill-bit wave-fields are spatial or temporal separated from each other, due to their different origins and velocities. Interferograms are obtained using the cross-coherence method, which is applied to the recorded passive seismic data. These are computed from 30sec time windows of the continuous recordings and then stacked into the final interferogram to increase the signal-to-noise ratio. Instead of migration summation, semblance is measured for the interferometric migration process. For the migration process, a constant velocity model is sufficient in this hard-rock environment. The major noise sources that we image are the vibrations of the drill rig and power generator, which appear to mask the weaker signal from the drill bit. In an ongoing second experiment, we utilize grid power, reducing the noise sources to the mud-pumps, rotating string, and rig.

How to cite: Trabi, B., Greenwood, A., and Bleibinhaus, F.: Seismic while drilling with a diamond drill bit in project DIVE DT-1B borehole in the Ivrea-Verbano Zone (Western Alps, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17124, https://doi.org/10.5194/egusphere-egu24-17124, 2024.

Core-drilling and groundwater well operation in topographic recharge areas have been rarely applied for groundwater quality monitoring or ecosystem exploration, simply due to lacking of productive water bodies in up to >100 m thick aeration zones. The scarcity of observers and data, and neglection in modelling opposes our efforts to unravel the role of thick hillslope aeration zones for services like water provision, water purification and biogeochemical cycling (Lehmann & Totsche, 2020). To fundamentally understand how groundwater quality comes about as a function of inputs and how climate and land use change will affect this quality, we concentrate our investigations on the soil-aeration zone-phreatic zone continuum in topographic highs. From our Hainich Critical Zone Exploratory in central Germany, we present methods and workflows for low-impact scientific drilling and construction of monitoring wells optimized for representative sampling of the total mobile inventory (Lehmann et al. 2021), and results from the analysis of drill cores, borehole geophysical data and multi-year environmental monitoring data. We found that transient (fluid) flow patterns contribute to groundwater quality dynamics, whereby overall aeration zone-phreatic zone-interactions cause quality fluctuations even in deep and isolated habitats. Results from recent drilling campaigns (2023) comprise the detection of narrow oxic zones (fractures, flow paths) also within mudstone-dominated strata (anoxic aquifer-storeys) and weathering-induced hydrofacies differences that indicate further complexity of habitat structures and ecosystem functioning across recharge(-discharge) zones.

 

 

References:

Lehmann, R., Totsche, K. U. (2020). Multi-directional flow dynamics shape groundwater quality in sloping bedrock strata. Journal of Hydrology 580, 124291. https://doi.org/10.1016/j.jhydrol.2019.124291

 

Lehmann, K., Lehmann, R., Totsche, K. U. (2021) Event-driven dynamics of the total mobile inventory in undisturbed soil account for significant fluxes of particulate organic carbon. Sci. Total Environ. 756, 143774. https://doi.org/10.1016/j.scitotenv.2020.143774

How to cite: Lehmann, R., Aehnelt, M., Grelle, T., Lehne, C., and Totsche, K. U.: “Looking deep” into shallow ground: scientific drilling and continuous monitoring in recharge areas as a key to the understanding of groundwater quality dynamics and subsurface ecosystem functioning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18764, https://doi.org/10.5194/egusphere-egu24-18764, 2024.

EGU24-19299 | ECS | Posters on site | ITS5.2/SSP1.13

TriGgeR mechanisms of Antarctic ice sheet INStability across the Plio-pLeistocene trAnsitIoN - GRAINSPLAIN project 

Giulia Matilde Ferrante, Laura De Santis, Sergio Andò, Robert McKay, Denise Kulhanek, Jenny Gales, Matteo Perrotti, Luca Zurli, Satish Singh, Michele Rebesco, Renata Giulia Lucchi, Tina Van Der Flierdt, Tim Van Peer, and Caterina Morigi

Growing evidence suggests that portions of the Antarctic Ice Sheet (AIS) could cross a tipping point over the next decades due to global warming. The Mid-Pliocene Warm Period (mPWP, 3.3-3 Ma, +2°C) is regarded as one possible geologic analog to the climate of the near future, and paleo-sea level during mPWP interglacials indicates that portions of the AIS were lost at that time. However, due to a lack of ice-proximal data, the timing, magnitude and trigger mechanisms of AIS retreats remain unconstrained. Here, we focus on the Ross Sea, where the IODP Exp. 374 Site U1523 recovered the first Antarctic Plio-Pleistocene record from a current-controlled sediment drift in an environment evolving from ice-proximal to open marine over time. U1523 is located where intrusions of warm deep water and outflows of cold water occur today, controlled mainly by the strength and route of the Antarctic Slope Current. To constrain the relative influence of oceanic currents and AIS dynamics on sediment erosion, transport and deposition across the Plio-Pleistocene transition (3.3-2.6 Ma), we integrate grain size, morpho-mineralogical, magnetic fabric analysis and geophysical logs from site U1523 with the multi-channel seismic line IT94-127A. We complement our dataset with a closeby box core (PNRA ODYSSEA exp., box core 08), that can be regarded as a present day analogue. Here, we present our morpho-mineralogical results on the box core and some specific intervals of the mPWP from site U1523. In particular, we perform single mineral Raman spectroscopy which, together with the entire suite of minerals and their relative abundance, highlight the different depositional environments and the source of the detritus, identifying local vs distant and magmatic vs metamorphic sources. Furthermore, we use the geophysical logs to perform rock physics correlation and we tie them to the seismic line, allowing the analysis to be extrapolated along the shelf.

How to cite: Ferrante, G. M., De Santis, L., Andò, S., McKay, R., Kulhanek, D., Gales, J., Perrotti, M., Zurli, L., Singh, S., Rebesco, M., Lucchi, R. G., Van Der Flierdt, T., Van Peer, T., and Morigi, C.: TriGgeR mechanisms of Antarctic ice sheet INStability across the Plio-pLeistocene trAnsitIoN - GRAINSPLAIN project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19299, https://doi.org/10.5194/egusphere-egu24-19299, 2024.

EGU24-22323 | Posters on site | ITS5.2/SSP1.13 | Highlight

Sensivity of the West Antarctic Ice Sheet to 2° Celsius of Warming. The SWAIS2C project. 

Arne Ulfers, Tina van de Flierdt, Richard Levy, Gavin Dunbar, Huw Horgan, Denise Kulhanek, and Molly Patterson and the SWAIS2C Science Team

The West Antarctic Ice Sheet (WAIS) is currently experiencing accelerated mass loss and contains enough ice to raise global sea levels by up to five meters if it were to melt completely. The objective of the international and interdisciplinary SWAIS2C project (Sensivity of the West Antarctic Ice Sheet to 2 Degrees Celsius of Warming) is to understand past and present factors influencing WAIS dynamics and to reconstruct WAIS response to warmer temperatures, including those exceeding the +2°C target outlined in the Paris Climate Agreement. The project will drill two deep boreholes beneath the Ross Ice Shelf to obtain sediment sequences from a site close to the grounding line of the Kamb Ice Stream site (KIS-3) and the Crary Ice Rise (CIR). The geological data will be used to improve model-based projections of future sea level contributions from Antarctica and to answer  the overarching question under what climatic conditions the WAIS collapsed in the past.

Here we present an overview of the SWAIS2C project, its’a aims and current progress. In the first season 2023/24, hot water drilling was successfully completed at KIS-3 to penetrate the ~580 m thick Ross Ice Shelf. Oceanographic measurements were taken in the ~55 m ocean cavity beneath the ice shelf, together with videos of the seafloor and ice shelf, and installation of permanent moorings. Gravity and hammer coring yielded 7.6 m of sediment, which have been subsampled for microbiology and geochemistry, and described using field-based x-ray images. The sediments recovered include the longest sediment core from the Siple Cost, measuring 1.92 m.

The sedimentological and drilling experience gained will be of great value for the 2024/25 season, when a team of drillers and scientists will return to KIS-3 for deep drilling with the Antarctic Intermediate Depth Drill (AIDD). A combination of hydraulic piston coring and rotary coring will be used to retrieve a sediment core of up to 200 m below sea floor. Drilling operations will be complemented by geophysical downhole logging with wireline tools from the Leibniz Institute for Applied Geophysics (LIAG) and a logging while tripping system provided by the German Research Centre for Geosciences (GFZ). The inclusion of different methods will allow downhole logging of several parameters over the entire sediment sequence and minimizes the influence of unstable borehole walls on the measurements.

How to cite: Ulfers, A., van de Flierdt, T., Levy, R., Dunbar, G., Horgan, H., Kulhanek, D., and Patterson, M. and the SWAIS2C Science Team: Sensivity of the West Antarctic Ice Sheet to 2° Celsius of Warming. The SWAIS2C project., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22323, https://doi.org/10.5194/egusphere-egu24-22323, 2024.

SSP2 – Stratigraphy, Earth Systems History and Climate Geology

EGU24-1320 | ECS | Posters on site | SSP2.1

Nonparametric estimation of age-depth relationships from sedimentological and stratigraphic information 

Niklas Hohmann, David De Vleeschouwer, Sietske Batenburg, and Emilia Jarochowska

Age-depth models are fundamental tools used in all disciplines that rely on geohistorical records. They assign ages to stratigraphic positions (e.g., in outcrops or drill cores), which is necessary to estimate rates of past environmental change and establish timing of events in the Earth’s history.

Methods to estimate age-depth models commonly use simplified parametric assumptions on the uncertainties of ages of tie points, e.g., that they follow a normal distribution. The distribution of time between tie points is estimated using simplistic assumptions on the formation of the stratigraphic record, for example that sediment accumulation follows a Poisson process. As a result, these methods cannot incorporate evidence from complex empirical data or expert knowledge (e.g., from sedimentary structures such as erosional surfaces or from basin models) into their estimates, leaving important sources of information un- or underused.

Here, we present two non-parametric methods to estimate age-depth relationships from complex sedimentological and stratigraphic data. The methods are implemented in the admtools package for R Software and allow the user to specify any error model and distribution of uncertainties. As use cases of the package, we

  • construct age-depth models for Devonian strata in the La Thure section, Belgium, using sedimentation rates constrained by cyclostratigraphic methods.
  • use measurements of extra-terrestrial 3He from ODP site 690 (Maud Rise, Weddell Sea) to construct age-depth models for the Paleocene–Eocene thermal maximum.
  • examine how temporally variable 210Pb fluxes in lacustrine environments affect estimates of sedimentation rates and age-depth models.

These examples show how information from a variety of sedimentological and stratigraphic sources can be combined to estimate age-depth relationships that accurately reflect uncertainties of both available data and expert knowledge.

How to cite: Hohmann, N., De Vleeschouwer, D., Batenburg, S., and Jarochowska, E.: Nonparametric estimation of age-depth relationships from sedimentological and stratigraphic information, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1320, https://doi.org/10.5194/egusphere-egu24-1320, 2024.

EGU24-1891 | Posters virtual | SSP2.1

A multiproxies paleoclimatic study of lacustrine sediment from the Castiglione maar drilling (central Italy):  first insight of the AMUSED Project. 

Patrizia Macrì, Gaia Siravo, Alessandra Smedile, Chiara Caricchi, Liliana Minelli, Bernd Wagner, Eleonora Regattieri, Gianfranco Di Vincenzo, Patrizia Ferretti, Ilaria Mazzini, Biagio Giaccio, Bianca Scateni, Antonio Cascella, Ilaria Isola, and Alessio Di Roberto

The AMUSED project (A MUltidisciplinary Study of past global climatE changes from continental and marine archives in the MeDiterranean region, https://progetti.ingv.it/index.php/it/amused) aims at improving knowledge of middle-late Quaternary climate variability by integrating paleoclimate multi-proxy data acquired in different geological settings of the Mediterranean region. In this context, we investigate the Castiglione maar, Colli Albani volcanic district in central Italy, for acquiring a high-resolution and geochronologically well-constrained multi-proxy record of the lacustrine succession. After geophysical exploration, two parallel 116 m- and 126.5 m-long sediment successions were recovered from the central sector of the basin. The sedimentary infilling mainly consists of fine sand, silt and clay, with minor gravel intervals and numerous tephras mostly deriving from explosive eruptions of the Roman Province volcanoes such as Mt. Vulsini, Vico, Mt. Sabatini and Alban Hills. More than fifty visible volcanic layers were identified and used, together with some lithostratigraphic features, for correlating the two parallel cores and build up a composite sediment section of 131.2 m in length. The geochemical fingerprinting of some key tephra layers allowed to establish a preliminary chronological framework for the Castiglione succession spanning the last 365 ka, with a mean sedimentation rate of 0.33 mm/yr. High resolution X-ray Fluorescence scanning was acquired at 2.5 mm intervals on the composite section and will be used, along with preliminary results from total inorganic and organic carbon, δ18O-δ14C and ostracods analyses, for paleoenvironmental reconstructions.

How to cite: Macrì, P., Siravo, G., Smedile, A., Caricchi, C., Minelli, L., Wagner, B., Regattieri, E., Di Vincenzo, G., Ferretti, P., Mazzini, I., Giaccio, B., Scateni, B., Cascella, A., Isola, I., and Di Roberto, A.: A multiproxies paleoclimatic study of lacustrine sediment from the Castiglione maar drilling (central Italy):  first insight of the AMUSED Project., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1891, https://doi.org/10.5194/egusphere-egu24-1891, 2024.

Integrated stratigraphic and sedimentological analysis have been used to reconstruct the paleoclimatic and paleoenvironmental history of the nonmarine siliciclastic deposits of the Injana Formation (Langhian-Serravallian) from the Kurdistan foreland basin (N. Iraq).The transition from marine to nonmarine deposits resulted from the gradual retreat of the Neotethys seaway SE-ward, sea level change, and the rising of the Zagros Fold-Thrust Belt. The last marine foreland deposits (Consist of mixed lagoonal carbonates and evaporites) of the Fatha Formation (Burdigalian) vary from the predominated nonmarine fluvial deposits of the Injana Formation siliciclastic deposits (with predominated sandstone, mudstone, and claystone). Bioevents variations are evident in benthic foraminiferal (Ammonia beccarii, miliolides). The marine mollusca represent by pelecypods and gastropods (i.e.,   Ostrea latimarginata , Ostrea subangulata, Clausinella persica, Clementia sp.,Cardium spp, Acteocina spp, Turbo sp.). The ichnofossil assemblages also shows varation from predominated Planolites, Thalassinoides  to Skolithos   and Scoyenia . The freshwater ostracods (Cytheridella, Penthesilenula) and brackish” water ostracods (i.e., Cyprideis) have been recorded in non -marine sequences while Chrysocythere spp, are predominated in the lagoonal parasequences.  Although Miocene mammals are rarely found in the Kurdistan foreland basin, recently, new terrestrial vertebrate remains were discovered, confirming the transition from marine to nonmarine depositional environments. This transition was associated with climate change from the warmest condition of the middle Miocene climate optimum (MMCO) to a colder condition. In addition, the XRD results indicate that clay mineralogy is changing, as illite-chlorite assemblages are replaced by bentonite-montmorillonite clays. The XRF results indicate the predominance of iron and silica oxides in the nonmarine deposits, whereas calcium, magnesium, sulfur oxides, and alkalis characterize the earlier marine deposits. These new results, in addition to the discovery of terrestrial vertebrate remains and the rise of the Zagros Mountains, show that the middle-late Miocene time was a critical period in shaping the present-day habitat in the NW Zagros belt.

How to cite: Ameen1, F., Koshnaw, R., and Vassilyan, D.: Middle Miocene integrated stratigraphy, paleoclimatic and environmental turnover imprints from the Kurdistan Foreland Basin, N. Iraq., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2570, https://doi.org/10.5194/egusphere-egu24-2570, 2024.

EGU24-2789 | ECS | Posters on site | SSP2.1

Sedimentary Evolution Characteristics of Middle Cambrian Carbonate Platform in Tabei Area 

Jingxuan Wang, Kuanhong Yu, and Aizimaiti Maimaiti

Tabei area is an important area of Cambrian ultra deep exploration in Tarim Basin. Middle Cambrian dolomite reservoirs are developed and the relationship between reservoir and cap rock configuration is complex. Therefore, the study of sedimentary facies types and their distribution characteristics is of great significance for the next exploration plan in the region. This study is based on drilling and seismic data within the work area, and comprehensively analyzes the sedimentary evolution process of the Middle Cambrian platform in the Tabei area through petrology, seismic facies, and well connected sedimentary facies. The research results indicate that the Middle Cambrian in the study area is a typical bordered platform, which is influenced by ancient terrain and develops (evaporates) tidal flats, reef shoals, platform edge reef shoals, slopes, and basins from west to east. The overall trend of the facies belt shows an eastward migration. The Taiwan region mainly develops tidal flat, evaporative tidal flat, and granular beach, further divided into six microfacies such as argillaceous dolomite and micritic dolomite. Six stages of reef shoals are developed at the edge of the platform, stacked in an aggradation progradation manner. Based on comprehensive analysis, it is believed that in addition to the platform edge reef beach body, the dolomite behind the reef beach is another favorable facies zone with good exploration potential.

How to cite: Wang, J., Yu, K., and Maimaiti, A.: Sedimentary Evolution Characteristics of Middle Cambrian Carbonate Platform in Tabei Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2789, https://doi.org/10.5194/egusphere-egu24-2789, 2024.

EGU24-4007 | Posters on site | SSP2.1

A new extended record of Lower to lower Upper Aptian deposits in Northern Germany – new insights in the Boreal Oceanic Anoxic Event 1a 

André Bornemann, Martin Blumenberg, Jochen Erbacher, Rüdiger Koch, and Robert Lippmann

A recently cored 49-m-thick succession of Early to early Late Aptian age from Garbsen, a small city 6 km northwest of Hannover, has been studied with respect to sedimentology, bulk organic geochemistry and biostratigraphy.

The basal 14 m cover an alternating paper shale-mudstone sequence (topmost Hoheneggelsen Formation) with a 2.3-m-thick “Fischschiefer” bed at the top. It is overlain by partly reddish-colored hemipelagic marlstones representing lithostratigraphically the Sarstedt Member, formerly also named Hedbergella Marls. The “Fischschiefer” is considered to represent the local expression of the global Oceanic Anoxic Event 1a in the Lower Saxony Basin. During Early Cretaceous times the Hannover area represented paleogeographically the eastern-central part and, thus, the depocenter of the Lower Saxony Basin.

In addition to detailed lithological data, we present high-resolution δ13Corg, CaCO3 and TOC data as well as a calcareous nannofossil biostratigraphy for this Boreal Aptian succession. This new core complements other records in the western part of the basin (Alstätte, Bottini et al., 2012) as well as southeast of Hannover (Hoheneggelsen KB9, Heldt et al., 2012) and, due to its completeness, provides new insights in the transition from the “Fischschiefer” deposit to the hemipelagic marlstone sedimentation.

 

References:

Bottini, C., Mutterlose, J., 2012. Integrated stratigraphy of Early Aptian black shales in the Boreal Realm: calcareous nannofossil and stable isotope evidence for global and regional processes. Newsl Stratigr 45, 115–137. doi:10.1127/0078-0421/2012/0017

Heldt, M., Mutterlose, J., Berner, U., Erbacher, J., 2012. First high-resolution δ13C-records across black shales of the Early Aptian Oceanic Anoxic Event 1a within the mid-latitudes of northwest Europe (Germany, Lower Saxony Basin). Newsl Stratigr 45, 151–169. doi:10.1127/0078-0421/2012/0019

How to cite: Bornemann, A., Blumenberg, M., Erbacher, J., Koch, R., and Lippmann, R.: A new extended record of Lower to lower Upper Aptian deposits in Northern Germany – new insights in the Boreal Oceanic Anoxic Event 1a, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4007, https://doi.org/10.5194/egusphere-egu24-4007, 2024.

EGU24-4078 | Orals | SSP2.1

Late Holocene calcium carbonate accumulation in a cold-water coral mound in the northern Bay of Biscay. 

Evan Edinger, Jean-François Bourillet, and Lenaick Menot

Cold-water coral reefs and communities can be locally important calcium carbonate factories in continental shelf and slope environments.  Cold-water coral mounds dominated by Desmophyllum pertusum (=Lophelia pertusa) occur within Bay of Biscay submarine canyons.  Here we present a late Holocene record of coral carbonate accumulation through a colonial scleractinian coral mound in the 750-850 m depth range in Guilvinec Canyon, northern Bay of Biscay.  Guilvinec Canyon, like most submarine canyons of the Bay of Biscay, is a dominantly siliciclastic sandy environment, with occasional coral gardens.  Maximum live coral cover in the area surveyed in Guilvinec Canyon was about 9%, measured close to the site of the sediment core analyzed.

A 2011 sediment core through the mound recovered 1.18 m of sediment, consisting of mostly siliciclastic silty sand and coral gravel, strongly dominated by Lophelia pertusa fragments.   In addition to standard geophysical, grain size, and mineralogical analyses, the core was analyzed by CT-scan.  The number of coral calices visible per cm3 was counted, and the core was subsampled for coral calice abundance and mass in 5 mm increments, calculating the number of calices and mass of coral carbonate skeletons per cm3 subsample.  An age model from previous 14C and U/Th ages of coral fragments in the core yielded a long-term average coral carbonate accretion rate of 78 g CaCO3 m-2 y-1 over the past ~2150 y, divided into two phases: 40.8 g CaCO3 m-2 y-1 (from core-bottom to -59 cm, approximately 685 ybp), and 156.2 g CaCO3 m-2 y-1 in the upper half of the core. Coarse coral-dominated gravel in the core-catcher contained coral fragments approximately 7 ka in age, indicating a long hiatus before the renewal of coral growth at this site.  Aragonite % in the fine sediment was not correlated with coral abundance in the core.  A second core recovered nearby was composed of siliciclastic silty sand, but contained almost no coral fragments.  The large variation between the two cores indicates high levels of local heterogeneity in sediment accumulation patterns, apparently much greater than the variation in live coral cover at the surface.

Coral carbonate accumulation rates in Guilvinec Canyon were 1-2 orders of magnitude lower than coral carbonate accumulation estimates from Lophelia pertusa reefs on the Norwegian Margin. Nonetheless, coral carbonate accumulation rates in the core were an order of magnitude higher than Recent coral carbonate production rates based on ROV-video estimates of coral biomass and published growth rates.  This difference may be attributable to time-averaging, local heterogeneity, changes in sedimentation or current regime, or to late-20th century decline in coral abundance resulting from a variety of anthropogenic pressures.  Recent threats to Bay of Biscay cold-water coral reefs include increased sediment mobilization from bottom trawling near the heads of submarine canyons, rising seawater temperatures, and declining aragonite saturation.  New field and lab experiments on coral growth rates and skeletal degradation may help to disentangle anthropogenic pressures and project the fate of Bay of Biscay cold-water coral reefs in the face of climate change and ocean acidification.

How to cite: Edinger, E., Bourillet, J.-F., and Menot, L.: Late Holocene calcium carbonate accumulation in a cold-water coral mound in the northern Bay of Biscay., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4078, https://doi.org/10.5194/egusphere-egu24-4078, 2024.

EGU24-4621 | ECS | Orals | SSP2.1

Microbially-catalyzed mineral formation – Enhanced carbonate precipitation rates determined by U/Th dating and calcium isotopes 

Daniel Smrzka, Yiting Tseng, Jennifer Zwicker, Thomas Pape, Andrea Schröder-Ritzrau, Norbert Frank, Anne-Désirée Schmitt, Daniel Birgel, Jörn Peckmann, Saulwood Lin, and Gerhard Bohrmann

Carbon is removed from Earth’s surface and may be stored within carbonate minerals over long periods of time. The formation of authigenic carbonate in marine sediments accounts for much of this sequestered carbon, whereby the rate of sequestration depends on mineral precipitation rates. Among the catalyzing agents of carbonate precipitation are biofilms and microbial mats, which are ubiquitous in Earth surface environments. Microbial carbonates are abundant at methane seeps where they form by the sulfate-driven anaerobic oxidation of methane (SD-AOM), mediated by anaerobic archaea and sulfate-reducing bacteria. We investigated a 5 m long core composed almost entirely of two microbially-derived carbonate cements from an active methane seep in the South China Sea, offshore Taiwan. Phase-specific U/Th dating, lipid biomarker analyses, and calcium isotope data suggest that one of these phases is a direct product of biofilm mineralization, typified by high precipitation rates. This study is the first to estimate the accretion rate of individual carbonate phases in microbial limestones, and provides first-order constraints on the catalytic effect of microbial activity on carbonate precipitation. This has implications on the rate of global carbon burial, which may be significantly increased by the influence of biofilms and microbial mats on carbonate precipitation.

How to cite: Smrzka, D., Tseng, Y., Zwicker, J., Pape, T., Schröder-Ritzrau, A., Frank, N., Schmitt, A.-D., Birgel, D., Peckmann, J., Lin, S., and Bohrmann, G.: Microbially-catalyzed mineral formation – Enhanced carbonate precipitation rates determined by U/Th dating and calcium isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4621, https://doi.org/10.5194/egusphere-egu24-4621, 2024.

EGU24-4630 | Posters on site | SSP2.1

Global to regional Holocene climate changes and events recorded in a near-slope deep sea brine-pool sediments of the NE Red Sea 

Alexander Petrovic, Prabodah Lakrani, and Volker Vahrenkamp

Marine climate archives in Red Sea sediments have the great potential to improve our understanding of mankind’s dispersal out of Africa. However, cores from deep sea sediments are often greatly disturbed by bioturbation reducing the resolution of recorded climate events. We report geochemical and geophysical data from a 244 cm long sediment core collected from a recently discovered deep sea brine pool near the Arabian slope and the Al Wajh carbonate platform. The analysis of the high-resolution climate archive preserved in the undisturbed sediments of the brine pool provide excellent correlations to numerous known historical events in the last 6.5 ka, and indicate the great potential of brine pool sediments to provide further insights into climate changes and human civilization development within the African-Arabian dessert belt.

The recovered marine sediment core from a brine pool was therefore investigated to test its reliability for in-depth Holocene climate studies. The brine-filled depression (>190 PSU; 25 m thick) is located 25 km south of the Al Wajh carbonate platform in 640 m water depths. It is bounded by a salt extrusion in the northwest and a steep shallow water reef in the east. The undisturbed dark-olive coloured sediment succession are carbonate-dominated, devoid of bioturbation, and rich in TOC indicating an anoxic environment. The established stratigraphy via five radiocarbon dates of (planktic foraminifera. T.sacculifer and O. universa) resulted in high sedimentation rates ranging from 30.22 to 50.6 cm/ka. The integration of geochemical (e.g., isotope data, XRF) and geophysical data (e.g., magnetic susceptibility, spectrophotometer reflectance) revealed the recording of dozens of prominent climate periods (e.g., Roman Climate Optimum, Little Ice Age), changes (e.g., Mid-Holocene Highstand), and historical events (e.g., collapse of Late Uruk and Akkadian Empire) since the Mid-Holocene. In addition, the data analyses suggest that even periods of increased ENSO activity are recorded within the brine pool sediments of the Red Sea.

The outcome of this study highlights the potential of anoxic brine pool sediments as a unique and important high-resolution climate archive and the urgent need to further in-depth studies.

How to cite: Petrovic, A., Lakrani, P., and Vahrenkamp, V.: Global to regional Holocene climate changes and events recorded in a near-slope deep sea brine-pool sediments of the NE Red Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4630, https://doi.org/10.5194/egusphere-egu24-4630, 2024.

EGU24-4748 | ECS | Posters on site | SSP2.1

Physical and chemical controls on ikaite (calcium carbonate hexahydrate) precipitation in seawater 

Madeleine Vickers and David Evans

Ikaite, CaCO3•6H2O, is a metastable polymorph of calcium carbonate which is the parent mineral to glendonites (stellate calcite pseudomorphs found throughout the geological record). In the modern ocean, ikaite may be found below the sediment-water interface, or in tufa columns, at temperatures of<7 °C (Buchardt et al., 2001; Zhou et al., 2015; Vickers et al., 2022), yet the presence of glendonites in marine sediments believed to have been deposited under much warmer conditions (i.e. > 10 °C) suggests that this ikaite could have formed under warmer conditions than it does today, or that short-duration cooling interrupted hyperthermal episodes of the early Cenozoic (Vickers et al., 2024). As much uncertainty surrounds the timing, and physical and chemical conditions of the formation, and transformation, of the precursor ikaite, the usefulness of glendonite for (semi-)quantitatively reconstructing temperature and environmental conditions is uncertain, and the explanation for the early Cenozoic glendonites remains obscure. This study examines the physical and chemical controls on ikaite nucleation, growth and transformation in seawater, with a view to understanding trace element and isotope partitioning into ikaite and ikaite transformation products, and if and how certain elemental and isotopic environmental proxies may be applied to glendonite calcite phases.

References

Buchardt, B., Israelson, C., Seaman, P. and Stockmann, G., 2001. Ikaite tufa towers in Ikka Fjord, southwest Greenland: their formation by mixing of seawater and alkaline spring water. Journal of Sedimentary Research, 71(1), 176-189.

Zhou, X., Lu, Z., Rickaby, R.E., Domack, E.W., Wellner, J.S. and Kennedy, H.A., 2015. Ikaite abundance controlled by porewater phosphorus level: Potential links to dust and productivity. The Journal of Geology, 123(3), 269-281.

Vickers, M.L., Vickers, M., Rickaby, R.E., Wu, H., Bernasconi, S.M., Ullmann, C.V., Bohrmann, G., Spielhagen, R.F., Kassens, H., Schultz, B.P. and Alwmark, C., 2022. The ikaite to calcite transformation: Implications for palaeoclimate studies. Geochimica et Cosmochimica Acta, 334, 201-216.

Vickers, M.L., Jones, M.T., Longman, J., Evans, D., Ullmann, C.V., Wulfsberg Stokke, E., Vickers, M., Frieling, J., Harper, D.T., Clementi, V.J. and Expedition, I.O.D.P., 2024. Paleocene–Eocene age glendonites from the Mid-Norwegian Margin–indicators of cold snaps in the hothouse?. Climate of the Past, 20(1), 1-23.

How to cite: Vickers, M. and Evans, D.: Physical and chemical controls on ikaite (calcium carbonate hexahydrate) precipitation in seawater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4748, https://doi.org/10.5194/egusphere-egu24-4748, 2024.

EGU24-5591 | ECS | Posters on site | SSP2.1

Triassic Stratigraphy of the North Sea: A New Cross-border Chronostratigraphic Framework using Age Equivalent Units from the Tampen Spur Area, Norwegian North Sea 

Spyridon Saltapidas, Adrian Hartley, John Howell, Nicholas Schofield, Rachel Brackenridge, and Douglas Watson

The Triassic interval of the northern North Sea contains important hydrocarbon reservoirs and potential targets for CO2 sequestration. However, understanding of the age and distribution of sedimentary facies within the Triassic succession is hampered by the absence of a robust chronostratigraphic framework. Although recent studies for the UK Central North Sea (UK CNS) have defined a robust Triassic chronostratigraphic framework, significant stratigraphic nomenclature differences coupled with lack of dateable palynomorphs within the Triassic continental Hegre Group of the Norwegian Northern North Sea have led to non-biostratigraphic cross-border correlations.

Preliminary results from palynology and heavy mineral studies from the Norwegian Northern North Sea within a newly refined tectonostratigraphic framework have prompted a re-examination of the chronostratigraphic correlations between the Central and Northern North Sea. In the greater Tampen Spur area, a lack of active fault movement during sedimentation suggests that deposition of up to 2 km of Triassic Hegre Group sediments is largely climatically controlled and potentially regionally correlatable. Herein we aim to extend the well-established Triassic chronostratigraphic framework of the UK CNS to the Norwegian Northern North Sea area using distinct and age-equivalent Triassic mudstone units.

Well data from the Tampen Spur area reveal a regionally correlatable Norian mudstone which represents the Alke formation of the Hegre Group and an additional unassigned Ladinian mudstone package. These mudstone units were deposited on the distal fringes of a major distributive fluvial system sourced from the Norwegian margin. The Alke Formation seals the progradational motif of the Norian Lunde Formation and the Ladinian mudstone seals the Norian-Ladinian sandstone of the Lomvi Formation. The sandstones record the progradation and mudstones the retrogradation of the distributive fluvial system.

Given the age and similar petrophysical properties, we propose that the Alke Formation is equivalent to the Jonathan Mudstone Member and the Ladinian Mudstone is equivalent to the Julius Mudstone Member of the Skagerrak Formation in the UK CNS. Thus, the Lunde formation is Josephine equivalent and the Lomvi formation represents the Joanne Member. This layer-cake reservoir configuration is completed with a sandier and locally truncated Raude Formation which is equivalent to the Rhaetian Joshua Mudstone Member of the UK CNS.

This preliminary cross-border chronostratigraphic framework unifies the Triassic stratigraphy of the North Sea within a newly refined tectonostratigraphic framework. Regional chronostratigraphic correlations allow a comprehensive paleogeographic reconstruction between the Central and Northern North Sea enlightening all major climatic alternations from Olenekian to Rhaetian.

How to cite: Saltapidas, S., Hartley, A., Howell, J., Schofield, N., Brackenridge, R., and Watson, D.: Triassic Stratigraphy of the North Sea: A New Cross-border Chronostratigraphic Framework using Age Equivalent Units from the Tampen Spur Area, Norwegian North Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5591, https://doi.org/10.5194/egusphere-egu24-5591, 2024.

EGU24-8094 | Posters on site | SSP2.1

Re-evaluation of the astronomically calibrated FC sanidine age 

Frederik Hilgen, Klaudia Kuiper, Dan Condon, Diana Sahy, Francisco Javier Sierro, Zoe Toorenburgh, Jörn-Frederik Wotzlaw, and Christian Zeeden

The Fish Canyon tuff sanidine (FCs) is the most widely used standard in 40Ar/39Ar geo­chronology. Its age is determined either through intercalibration with astronomical or U/Pb dating, as intrinsic uncertainties in the K-Ar dating method are too large to provide a “primary”  FCs age. Hence, this age is not only critical for 40Ar/39Ar dating, but its determination also guarantees the intercalibration of the 3 main dating methods used to construct our standard geological time scale so that they produce the same age for the same event.In 2008, Kuiper and others published an astronomically calibrated age of 28.201 ± 0.046 Ma that apparently settled the debate as demonstrated by its subsequent incorporation in GTS2012. Yet, this age has been challenged by later studies that used various approaches, leading again to a ~1.5% age scattering. This ongoing uncertainty hampers the construction of a uniform and coherent time scale that is key to modern high-resolution, multi-disciplinary studies in Earth history.

Here we combine 1) a re-examination of the astronomical tuning on which the FCs age of 28.201 Ma is based, 2) a statistical analysis of this tuning using a quantitative record and 3) new single crystal U/Pb zircon ages of the FCT and K/Pg boundary with 4) an in-depth literature review. The re-examination and statistical analysis show that the original tuning is correct and that alternative tunings consistent with different FCs ages are less plausible. Our new U/Pb ages are also in agreement with this FCs age. Finally, this outcome is consistent with studies that use single crystal 40Ar/39Ar sanidine and/or U/Pb zircon dating of usually astro­nomically dated volcanic beds and magnetic reversals of Cretaceous to Quaternary age.

Alternative astronomical calibrations that are substantially younger may have suffered from less reliable radio-isotopic ages and/or uncertainties in the astronomical solution and the tuning to this solution. Recent progress in astronomical dating of the K/Pg boundary further suggest a ~100-kyr younger age, but boundary ages based on the 3 main dating methods remain inconsistent. An older FCs age based on statistical optimization may result from the inclusion of 40Ar/39Ar-U/Pb data pairs that do not follow Earthtime protocols, but is in itself an elegant approach to tackle both decay constants and standard issues.

In summary the fundamental issue of the FCs age has still not been solved but consensus is being reached on an age close to 28.2 Ma. We therefore recommend the continued use of the astronomically calibrated age of 28.201 ± 0.046 Ma; this recommendation is in line with the recent decision to adopt this age again in GTS2020. However, we endorse further investigation in a community-based effort, where new data and improved methodologies may lead to better insight into fundamental properties and a slightly different age of the standard. This effort will also reveal whether lternative approaches, such as statistical optimization or direct U/Pb FCT zircon dating, may provide an even more accurate and precise FCs age.

How to cite: Hilgen, F., Kuiper, K., Condon, D., Sahy, D., Sierro, F. J., Toorenburgh, Z., Wotzlaw, J.-F., and Zeeden, C.: Re-evaluation of the astronomically calibrated FC sanidine age, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8094, https://doi.org/10.5194/egusphere-egu24-8094, 2024.

EGU24-8260 | Posters on site | SSP2.1

Sedimentary facies and depositional environments of the Upper Triassic carbonate-evaporite succession in the Honaz Mountain Range (SW Anatolia, Turkey)  

Hülya Alçiçek, Amalia Spina, Simonetta Cirilli, İsmail Ömer Yılmaz, Enrico Capezzuoli, Andrea Brogi, Domenico Liotta, and Mehmet Cihat Alçiçek

The Upper Triassic carbonate-evaporite-bearing succession in the Honaz Mountain Range (HMR) in SW Anatolia (Turkey), exists as a tectonic slice within the carbonate and ophiolithic units of allochthonous Lycian Nappe stacks. It comprises interbedded layers of sulphates (gypsum) and limestones or dolostones. Sedimentological and palynofacies analyses suggest that the Honaz succession was deposited in the more protected areas of the peritidal zone of a shallow inner ramp under a tropical/arid climate. Three main subenvironments are identified based on facies and microfacies associations: (i) Sabkha, exhibiting two distinct microfacies-gypsum and peloidal packstone/grainstone, (ii) Tidal flat, consisting of six microfacies-cryptalgal boundstone, fenestral bindstone, laminated peloidal mudstone, laminated algal/microbial boundstone, pisolite rudstone, and carbonate breccias, (iii) Lagoon, featuring five microfacies-laminated peloidal packstone/grainstone, crinoidal wackestone/packstone, mudstone, bioclastic packstone, and ostracodal/peloidal packstone to grainstone. The succession is characterized by meter/submeter-scale cyclic facies alternations, similar to Lofer cycles, Dolomia Principale/Hauptdolomit Formation, and Dachstein Formation of European basins.

Facies and petrographic analyses, along with Sr isotope ratios of dolomites, indicate early dolomitization from evaporated seawater in this environment (shallow seepage reflux or evaporative-drawdown). However, the depletion in δ18O (-11.53 to -5.46 ‰, mean -8.29 ‰), and slightly radiogenic Sr isotope values of dolomites are attributed to a recrystallization process, occurring at high temperatures during burial diagenesis. The relatively high δ13C values (+0.76 to +3.60 ‰, mean +2.42 ‰) suggest dolomite alteration in a relatively closed system. The microfacies of the Honaz succession are comparable to those in other Upper Triassic successions (e.g., western Carpathians, Italian Apennines, Spain, northern Calcareous and southern Alps, external Dinarides and Hellenides, southwestern Germanic Basin, Morocco, Israel, Albany) deposited under similar environmental conditions. Comparing facies with those from other coeval sequences allows us to delineate such carbonate-evaporite shallow water platforms on the northern margin of the Neotethys Ocean. This study was supported by the Pamukkale University BAP Research Project (2022ÜBBİD001).

How to cite: Alçiçek, H., Spina, A., Cirilli, S., Yılmaz, İ. Ö., Capezzuoli, E., Brogi, A., Liotta, D., and Alçiçek, M. C.: Sedimentary facies and depositional environments of the Upper Triassic carbonate-evaporite succession in the Honaz Mountain Range (SW Anatolia, Turkey) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8260, https://doi.org/10.5194/egusphere-egu24-8260, 2024.

EGU24-8906 | Posters on site | SSP2.1

CarboKitten.jl, an Open Source simulator for Carbonate Platform formation in Julia 

Johan Hidding, Xianyi Liu, Peter Burgess, and Emilia Jarochowska

Carbonate Platforms form an important source of information on the past evolution of species as well as the climate conditions they lived in. However, stratigraphic records are often considered unreliable tracers of evolution, since they contain many gaps.

These gaps are often on a time scale too short to measure, but may significantly affect further studies of biodiversity and climate change. This is why we use forward modelling to estimate the statistics of gap distributions under a wide variety of environmental parameters. Forward modelling can be used to test hypotheses at time scales that are not available for experimentation. The dominant driver for generating different stratigraphic architectures is the input sea-level curve, balancing periodic (Milankovich), stochastic and subsidence only effects. Added to that are varying degrees self-organisation, sediment transport and subarial erosion.

The basis of our model is sediment production following the model by Bosscher and Schlager (1992), with biological self-organisation modeled after the cellular automaton approach (CarboCAT) by Burgess (2013) and a sediment transport model inspired on Warrlich (2000).

CarboKitten is fully Open Source, written in Julia, aiming for performance, modularity and ease of use. We will show preliminary results produced by CarboKitten and also explain how they are generated.

How to cite: Hidding, J., Liu, X., Burgess, P., and Jarochowska, E.: CarboKitten.jl, an Open Source simulator for Carbonate Platform formation in Julia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8906, https://doi.org/10.5194/egusphere-egu24-8906, 2024.

EGU24-11332 | ECS | Orals | SSP2.1

Sedimentary record and sequence stratigraphy of the Middle Triassic carbonate ramp in Sardinia (Italy) 

Lorenzo Stori, Javier Martín Chivelet, José López-Gómez, and Luigi Ausonio Ronchi

The Triassic succession of Sardinia (Italy) displays the typical “Germanic-like” facies tripartition (Buntsandstein-Muschelkalk-Keuper), which enables regional and interregional correlations with the Central Europe and the western Mediterranean sectors. This work explores the Middle Triassic (Muschelkalk) sedimentary record of this island, which has long been studied and recognized as a key-stratigraphic point for reconstructing the palaeogeographical evolution of the Western Tethys Sea during that time. 
We conducted a stratigraphic survey fieldwork on 12 sections representing the different formations, and integrated the new obtained palaeontological, geochemical, sedimentological and stratigraphical data with a comprehensive literature review. Moreover, a detailed facies analysis has been performed through field observation and petrographic analysis, following previous approaches to the regional sedimentology. As result, it has been possible to observe that the Sardinian Muschelkalk, interpreted as a carbonate ramp, comprises five main broad sedimentary environments: sabkha, carbonate tidal flat, shallow lagoon, shallow  calcarenitic shoals, and storm-dominated mid-ramp. 
The obtained data made possible to carry out a sequence stratigraphic analysis, which revealed a major transgressive-regressive cycle of about 5-6 million years (late Illyrian to latest Longobardian), comparable to a 2nd order cycle in the sense of Vail et al. (1991). This sequence is well developed and continuous in the north of the island (Nurra Region) and has its interregional equivalent in different basins of the Mediterranean and Levantine-Balearic domains of neighbouring Iberia (Mega-Depositional Sequence-II of Escudero-Mozo et al., 2015). However, we also noted the absence of outer ramp systems in Sardinia, unlike in other areas of the western Mediterranean.
The result of our study helps to better understand the paleogeography of the westernmost transgression of the Tethys Sea during the Middle Triassic, as well as the corridors available for the migration and distribution of the Alpine and Sephardic faunas during the time of the recovery after the Permian-Triassic transition crisis.
 
References:
Escudero-Mozo, M.J., Márquez-Aliaga, A., Goy, A., Martín-Chivelet, J., López-Gómez, J., Márquez, L., Arche, A., Plasencia, P., Pla, C., Marzo, M., Sánchez-Fernández, D., 2015. Middle Triassic carbonate platforms in eastern Iberia: Evolution of their fauna and palaeogeographic significance in the western Tethys, palaeogeography, Palaeoclimatology, Palaeoecology 417, 236–260.
Vail, P.R., Audemard, F., Bowman, S.A., Eisner, P.N., Perez-Cruz, C., 1991. The stratigraphic signatures of tectonics, eustasy and sedimentology–an overview. En: Einsele, G., Ricken, W., Seilacher, A. (Eds.), Cycles and Events in Stratigraphy. Berlin, Springer-Verlag, 617–659

How to cite: Stori, L., Martín Chivelet, J., López-Gómez, J., and Ronchi, L. A.: Sedimentary record and sequence stratigraphy of the Middle Triassic carbonate ramp in Sardinia (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11332, https://doi.org/10.5194/egusphere-egu24-11332, 2024.

EGU24-11593 | ECS | Posters on site | SSP2.1

Cyclostratigraphy of the Ediacaran Nama Group in Namibia based on photogrammetry 

Bianca Spiering, Maarten Zwarts, Ajani Bissick, Andrea Boscaini, Joshua Davies, Galen Halverson, Brandt Gibson, Marc Laflamme, and Frederik Hilgen

The middle Nama Group, deposited during the late Ediacaran in southern Namibia, is a 1 km-thick mixed carbonate-siliciclastic shallow-marine succession that displays observable regularity in its weathering profile. However, the possible role of astronomical climate forcing in this succession remains poorly understood. As a first step to understand the origin of the regularity, an initial cyclostratigraphic framework was developed using Google Earth satellite images and published U-Pb zircon ages of volcanic ash beds. Although the estimated average periodicity of 120-180 k.y. for the dominant scale of variation falls within the frequency band of astronomical forcing, it is not yet possible to discriminate between an origin related to short (~100 k.y.) eccentricity or 173 k.y. obliquity amplitude modulation. In order to refine the framework, we generated high-resolution quantitative records of the weathering profile based on drone photogrammetry. Spectral analysis on the depth series of slope steepness reveals significant spectral power related to the dominant variation at a scale of tens of meters. Additionally, it captures spectral power related to smaller-scale variations at less than 10 m. For age control, the depth series are linked to published U-Pb ages as well as to newly collected volcanic ash samples more closely tied to the analyzed sections. New high-precision dates will be crucial to determine the astronomical origin of these cycles.

How to cite: Spiering, B., Zwarts, M., Bissick, A., Boscaini, A., Davies, J., Halverson, G., Gibson, B., Laflamme, M., and Hilgen, F.: Cyclostratigraphy of the Ediacaran Nama Group in Namibia based on photogrammetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11593, https://doi.org/10.5194/egusphere-egu24-11593, 2024.

EGU24-11631 | ECS | Posters on site | SSP2.1

Towards dating marine sediments using 26Al 

Marleen Lausecker, Alexander Wieser, Oscar Marchhart, Dominik Koll, Johannes Lachner, Silke Merchel, and Florian Adolphi

Radiometric dating methods are indispensable tools for providing a common and precise timescale for different paleo-environmental archives and their climate records. The cosmogenic radionuclides 26Al and 10Be decay with half-lives of 0.7 Ma (26Al) and 1.4 Ma (10Be), respectively, allowing radiometric dating of climate archives far beyond the range of 14C (t1/2=5730 a) and 230Th (t1/2=75 ka).
While 10Be has become a common tool in marine geology, 26Al has been studied significantly less. Low atmospheric 26Al production rates and high stable 27Al concentrations result in very low 26Al/27Al ratios, often near the detection limit of accelerator mass spectrometry (AMS). However, with its half-life of 0.7 Ma 26Al would be perfectly suited to bridge a gap of the currently available radiometric dating methods and may allow for constructing better age models in the 1-3 Ma range. Recently, new developments in the field of AMS enable measurements of low 26Al/27Al ratios by isobar suppression using selective photodetachment via ion laser interaction (ILIAMS at University of Vienna). We use these advances to study 26Al/27Al of globally distributed core-top marine sediments. In combination with the corresponding 10Be/9Be we can now assess the spatial variability of authigenic 26Al/27Al and 26Al/10Be in core-top marine sediments as an important premise for the use of 26Al as a dating tool. Based on these measurements we are able to identify suitable locations for further studies on the behaviour of 26Al/27Al and 26Al/10Be during deposition in the sediment.

 

Ackn.: Parts of the measurements were supported by the RADIATE project from the EU Research and Innovation programme HORIZON 2020 under grant agreement No 824096. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association.

How to cite: Lausecker, M., Wieser, A., Marchhart, O., Koll, D., Lachner, J., Merchel, S., and Adolphi, F.: Towards dating marine sediments using 26Al, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11631, https://doi.org/10.5194/egusphere-egu24-11631, 2024.

EGU24-12376 | Orals | SSP2.1

Orbital forcing over 3.5 billion years - Implications for cyclostratigraphy 

Richard Zeebe and Margriet Lantink

Orbital (or Milankovic) forcing of the Earth system is key to understanding rhythmic climate change and its expression in stratigraphic sequences on time scales >10 kyr. Stratigraphic applications concerned with past orbital forcing rely on astronomical solutions, which represent the backbone of cyclostratigraphy and astrochronology. Here we present new deep-time astronomical solutions from state-of-the-art solar system integrations for orbital eccentricity, inclination, obliquity, and precession over the past 3.5 Gyr. We performed long-term ensemble integrations to explore the possible solution/phase space of the system. Our study provides multiple astronomical solutions and characteristic long-term features of Milankovic forcing. Importantly, we integrate the equations of motion for Earth's spin axis over 3.5 Gyr, yielding full solutions for Earth's obliquity and climatic precession. We found startling results regarding the primary astronomical cycle (405 kyr in the recent past) utilized in deep-time paleoclimate analyses and for constructing age models, aka the long eccentricity cycle. The widely accepted and long-held view is that the long eccentricity cycle was practically stable in the past and may hence be used as a "metronome" to reconstruct accurate chronologies. However, we found that the LONG ECCENTRICITY CYCLE CAN BECOME UNSTABLE over long time scales, rendering Earth's orbital eccentricity and climate-forcing spectrum unrecognizable compared to the recent past. Furthermore, our computations show that Earth's obliquity was lower and its amplitude (variation around the mean) significantly reduced in the past. We therefore predict weaker climate forcing at obliquity frequencies in deep time and a trend toward reduced obliquity power with age in stratigraphic records. Our findings have multiple, fundamental implications for cyclostratigraphy, astrochronology, and paleoclimatology, which will be discussed in this presentation.

How to cite: Zeebe, R. and Lantink, M.: Orbital forcing over 3.5 billion years - Implications for cyclostratigraphy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12376, https://doi.org/10.5194/egusphere-egu24-12376, 2024.

EGU24-13252 | Posters on site | SSP2.1

Sequence stratigraphy based on high-resolution seismic profiles in the late Pleistocene-Holocene deposits of the eastern Yellow Sea 

Dong-Geun Yoo, Seok-Hwi Hong, Gwang-Soo Lee, Gil-Young Kim, and Yunsoo Choi

The late Quaternary stratigraphy and depositional history at the eastern Yellow Sea shelf was studied using a dense network of high-resolution, single-channel seismic reflection profiles and sediment data. The shelf deposits in this area consists of six seismic units formed since the LGM. During the LGM, the study area was completely exposed, resulting in subaerial erosion associated with paleo-channel incision by the Huanghe and Korean Rivers. As the shelf was flooded, the incised channels were backfilled fluvial or coastal sediments, forming incised channel-fill deposits (SU1). The paleo-river may have supplied abundant terrigenous sediments to the study area around the paleo-river mouth and adjacent area. These sediments were trapped within the paleo-estuary and formed SU2, regarded as an estuarine deposit. Two types of serial sand ridges (SU3 and SU5) which correspond to transgressive deposits developed. SU3 on the southern part (80~110 m deep) is regarded as a moribund-type mainly formed during the early to middle stage of transgression. These are thought to have ceased growing and remobilizing. In contrast, SU5 (occurring 30~50 m deep off the Korean Peninsula) is generally regarded as active sand ridges deposited during the late stage of transgression and is partly modified by modern tidal currents. As the transgression continued, the near-surface sediments were reworked and redistributed by shelf erosion, resulting in a thin veneer of transgressive sands (SU4). The uppermost unit (SU6) formed the Heuksan Mud Belt (HMB), which is one of the most prominent mud deposits in the Yellow Sea. The lower part of the HMD corresponds to shelf-mud deposited during the late stage of transgression, whereas the upper part consists of a recent shelf-delta developed after the highstand sea level at about 7 ka BP. 

How to cite: Yoo, D.-G., Hong, S.-H., Lee, G.-S., Kim, G.-Y., and Choi, Y.: Sequence stratigraphy based on high-resolution seismic profiles in the late Pleistocene-Holocene deposits of the eastern Yellow Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13252, https://doi.org/10.5194/egusphere-egu24-13252, 2024.

EGU24-13499 | Posters on site | SSP2.1

Reconstruction of bayhead delta in response to the Holocene sea-level changes in confined morphology, the Nakdong valley fill, southeastern Korea 

Seok-Hwi Hong, Woo Hun Ryang, Dong-Geun Yoo, and Jin Cheul Kimg

Bayhead delta is one of the links between fluvial and estuarine system where terrestrial sediments are prograding into the estuary. Despite the critical position of the bayhead delta, the Holocene reconstructions of coastal linkage area are poorly documented based on bayhead delta data from direct cores. This study provides sedimentary characteristics, stratigraphic interpretations, and also a new concept of a full-filled bayhead delta. Five cores are acquired in the Nakdong valley fills consisting of late Pleistocene to Holocene deposits. Sixteen facies are defined and grouped into eight facies association; alluvial plain, fluvial channel and floodplain, oxidized fluvial channel, tidal flat, tidal bar, central basin and bayhead prodelta, bayhead delta front, and bayhead delta plain. The associations are compiled up three depositional units in the Nakdong valley fills: Unit 1, 2, and 3. Unit I consists of alluvial plain and fluvial channel in the lowermost part of cores. Unit II contains tidal flats, tidal bars, and central basin in an estuarine environment adjacent to Unit I. The topmost Unit III is bayhead delta deposits consisting of bayhead delta plain, bayhead delta front, and bayhead prodelta after the depositions of Unit II. Age data for the Nakdong valley fills, suggest that these depositional environments developed in depositional stages (before about 12 ka, 12 and 9 ka, 9 and 7 ka, 7 and 5 ka, 5 and 3, and after 3 ka). The sequence stratigraphy of the Nakdong valley fills can be divided into three systems tract; a lowstand systems tract (LST), a transgressive systems tract (TST), and highstand systems tract (HST). The uppermost deposits of the Nakdong valley show a bayhead deltaic succession string imprint of fluvial processes in an embayed environment. Most bayhead deltas are limitedly developed within the head of the estuarine systems, whereas the Nakdong deltaic deposits fully filled in the estuary system. This full-filled type is interpreted to represent that the relative rate of fluvial sediment input exceeds the rate of local accommodation creation. 

How to cite: Hong, S.-H., Ryang, W. H., Yoo, D.-G., and Kimg, J. C.: Reconstruction of bayhead delta in response to the Holocene sea-level changes in confined morphology, the Nakdong valley fill, southeastern Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13499, https://doi.org/10.5194/egusphere-egu24-13499, 2024.

EGU24-13802 | Posters virtual | SSP2.1

Discussion and Supplement of Limestone Classification Schemes 

Xiangqian Ma, Longwei Qiu, Yelei Wang, and Yongqiang Yang

In the more than 120 years since Amadeus William Grabau (1870-1964) first proposed the classification of carbonate rocks in 1904, geologists have conducted in-depth research on this issue and made multiple modifications, forming the currently relatively comprehensive and systematic limestone classification scheme. Among them, Folk (1959, 1962) and Dunham (1962) classified limestones based on the perspective of structural maturity, which has become the most widely used classification scheme to this day. It is worth noting that Mei Mingxiang supplemented Wright VP’s (1992) classification scheme in 2001 by adding types of limestones formed by event sedimentation that cannot be explained by the perspective of structural maturity, such as seismolithic limestone, turbidite limestone, etc.

However, there are also problems with previous classification schemes. First, limestone types similar in structure to clastic rocks formed by terrigenous carbonate particles under abnormal depositional processes are not included in the carbonate rock classification system; Second, travertine precipitated carbonate rocks are not included in the carbonate rock classification system. Based on studies of carbonate rudite in the Bengbu depression, conglomerate deposits of the Guanzhuang Formation in the Pingyi Basin, and travertine, as well as years of field work experience, the author has further modified the limestone classification system by adding a terrigenous limestone class formed under abnormal depositional conditions and a purely chemical limestone class.

In view of the well-developed characteristics of terrestrial carbonate rocks in China, a terrigenous clastic limestone subclass was added under the abnormal deposition subclass, and a purely chemical limestone class with mud crystal components was added under the diagenetic class. The following changes have been made to the cause-structure classification table of limestones in this study: (1) The classification method of dividing limestones into depositional, biological and diagenetic classes remains unchanged, but the skeletal components are used as the basis for further subdivision. Compared with the previous scheme, more terrigenous clastic and mud crystal classes have been added to the skeletal components. (2) For limestones formed by terrigenous carbonate particles under abnormal depositional conditions, they are subdivided into rudite limestone, arenite limestone, mudstone limestone and their transitional types according to the particle size of the skeletal grains. (3) In the diagenetic class, the added purely chemical limestone refers specifically to travertine or travertine cemented collapse limestone (cave limestone), with mud crystal as its skeletal component.

How to cite: Ma, X., Qiu, L., Wang, Y., and Yang, Y.: Discussion and Supplement of Limestone Classification Schemes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13802, https://doi.org/10.5194/egusphere-egu24-13802, 2024.

EGU24-14075 | ECS | Posters on site | SSP2.1

Stratigraphy and sedimentology of the Pleistocene Maobitou Limestone in the Western Hengchun Tableland, southern Taiwan 

Q. Chelsea Wong, J. Bruce H. Shyu, Shih-Wei Wang, and Kai-Shuan Shea

The Hengchun Peninsula is the southernmost part of Taiwan Island, and marks the youngest portion of this active orogenic belt. At the southwestern corner of the peninsula, the Western Hengchun Tableland is underlain by the Pleistocene Hengchun Limestone, one of the youngest stratigraphic units of the Hengchun Peninsula. The Maobitou Limestone, which only crops out at the southern tip of the tableland, is a distinctive part within the Hengchun Limestone. Its ubiquitous large-scale cross beds have sparked controversy in its sedimentary environments. The location of this unit makes it a crucial stratigraphic marker for further understanding the growth processes of the peninsula, and even the orogen itself. However, the Maobitou Limestone has not been studied as much as the other parts of the Hengchun Limestone. Therefore, we investigated 15 outcrops of the Maobitou Limestone along the coastline for their detailed sedimentological and stratigraphical characteristics. We interpreted the limestone as a deposit under storm-influenced environment, due to the observations of (i) amalgamated beds with hummocky cross-stratification (HCS); (ii) graded grains observed within polished slabs; (iii) shelly beds rich in broken barnacles; (iv) various taphonomic conditions of fossils; (v) micrite found in grainstones; and (vi) slightly bioturbated or burrowed beds at bottom of units. Three lithofacies groups were established from these observations: (a) bioclastic packstone facies; (b) bioclastic packstone-grainstone facies, and (c) bioclastic grainstone facies. Variations within these groups were also identified through further subdivision with sedimentary structures and abundance of lithoclasts. We can further correlate these facies between stratigraphic columns using an irregular scouring surface at a similar horizon, and with a 70-m long borehole core. Based on biostratigraphy, the depositional age of the Maobitou Limestone likely ranges between 0.61 and 1.70 Ma, and appears to be different from the other parts of Hengchun Limestone. The source of winnowed skeletal materials may be a topographic high that is likely a coral reef area, supporting our interpretation that the Maobitou Limestone is deposited from high energy storm waves, above the storm wave base off the ramp. As the orogen grows, the depositional setting evolved from a storm-influenced middle ramp and shallowed upward into the inner ramp. 

How to cite: Wong, Q. C., Shyu, J. B. H., Wang, S.-W., and Shea, K.-S.: Stratigraphy and sedimentology of the Pleistocene Maobitou Limestone in the Western Hengchun Tableland, southern Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14075, https://doi.org/10.5194/egusphere-egu24-14075, 2024.

EGU24-14116 | Posters on site | SSP2.1

Physical property characterization of sand ridge sediments in the continental shelf of the South Sea, Korea 

Gil Young Kim, Kiju Park, Seok-Hwi Hong, Eun Je Jeong, Gwang Soo Lee, Dong Geun Yoo, Gee Soo Kong, and Shin Yu

Sand ridges are more developed around the continental shelfs with the strong tide current. Various sand ridges are distributed in the continental shelf of the South Sea, Korea. The deep core samples from the sand ridges of South Sea were collected and analyzed to characterize physical property with sedimentary depth. Laboratory analysis (compressional velocity, physical properties, and grain size) was conducted on core samples. Wet bulk densities are mostly ranges from 1.75 to 2.15 g/cm3. Grain densities are dominant between 2.55 g/cm3 and 2.65 g/cm3. Velocities are distributed between 1650 m/s and 1850 m/s. Whereas, porosities are low less than 50% (mostly 40%) compared to muddy sediments. The sand ridge sediments are mostly composed of sandy materials (less than 4Ø in mean grain size). Shell fragments and are intermittently included in the sediments. Muddy sediments are also frequently observed. The lithology of deep core samples with sedimentary depth are various, reflecting changes of sedimentary environments during deposition. The physical property data were readily classified in good agreement with the lithological units alternating sand and muddy sand with sedimentary depth. The sand ridge sediments in study area were largely originated and redistributed from paleo-Seomjin River, caused by sea-level changes during the Quaternary. These results suggest that the physical properties of these sediments are mainly controlled by depositional processes in the vicinity of the paleo-Seomjin River, and that sea-level change specifically was a dominant sedimentary process in the study area during the Quaternary.

How to cite: Kim, G. Y., Park, K., Hong, S.-H., Jeong, E. J., Lee, G. S., Yoo, D. G., Kong, G. S., and Yu, S.: Physical property characterization of sand ridge sediments in the continental shelf of the South Sea, Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14116, https://doi.org/10.5194/egusphere-egu24-14116, 2024.

EGU24-16720 | Posters on site | SSP2.1

Chemo- and sequence stratigraphy of Toarcian to Aalenian sedimentary successions from southern Germany 

Erbacher Jochen, Mann Thomas, Bornemann André, Blumenberg Martin, and Kneuker Tilo

Toarcian to Aalenian sedimentary deposits in southern Germany have been accumulated in a shallow-marine, epicontinental shelf environment. The according successions are dominated by marlstones, thick claystones and argillaceous siltstones, with increasing percentages of sandstones towards the top of the Aalenian. While the Toarcian, including the TOC-rich paper shales of the Toarcian Oceanic Anoxic Event (T-OAE), is characterized by distinct lithologies, resulting in a number of hiatuses, Aalenian sedi­ments are likely to represent a relatively complete stratigraphic record. Although the investigated sequences are located in a region that has been known for its famous Jurassic sequences for more than 150 years, the sedimentary evolution and paleoclimatic significance of these successions, remain largely unexplored on a basin-wide scale. Here we present a suite of high-resolution x-ray fluorescence (XRF) core scanning, stable organic carbon isotope and biostratigraphy data to identify Transgressive-Regressive cycles during the Late Toarcian to Aalenian. Results are based on four scientific drill cores of 200 - 250 m length, taken on a profile over a distance of about 300 km. Resulting trends in elemental Si/Al ratios, which are indicative for subtle grain-size variations, combined with sedimentological observations on ichnofacies and bedform development were used to reconstruct shoreline trajectories and establish a sequence stratigraphic framework. Our study mainly focus the thick and largely homogenous lower Aalenian Opalinuston Formation.

How to cite: Jochen, E., Thomas, M., André, B., Martin, B., and Tilo, K.: Chemo- and sequence stratigraphy of Toarcian to Aalenian sedimentary successions from southern Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16720, https://doi.org/10.5194/egusphere-egu24-16720, 2024.

EGU24-17026 | ECS | Orals | SSP2.1

Trends in Aragonite Dissolution through the Phanerozoic 

Theresa Nohl, Adam Kocsis, and Uwe Balthasar

Different calcium carbonate polymorphs, such as aragonite and calcite, participate differentially in early marine diagenesis due to their different thermodynamic stability. The microbial decay of organic matter causes distinct redox zones during the early stages of burial. In these conditions aragonite is unstable and dissolves, while the dissolved calcium carbonate can then reprecipitate as calcite cement. This results in areas or layers of calcium carbonate export (i.e., marl) and areas or layers of calcium carbonate import (i.e., limestone). The implications for the interpretation of carbonate rock sequences are highly debated, and the potential influences of this redistribution of carbon and other elements on global geochemical cycles remains underexplored. The intensity of this early diagenetic carbon redistribution is largely driven by availability of aragonite in the original sediment. As the seawater Mg/Ca ratio and temperature strongly impact inorganic calcium carbonate mineralogy and skeletal mineralogy (at least before the Jurassic), we expect that the intensity of the redistribution varies throughout the Phanerozoic with seawater Mg/Ca and temperature, i.e. aragonite-calcite sea conditions. In this study we evaluate the intensity of early diagenetic overprint and aragonite dissolution through the Phanerozoic by comparing diagenetically inert Al/Ti ratios of limestone-marl alternations from published datasets in the context of available shelf area and palaeotemperature. We identify time intervals with higher or lower diagenetic overprint and discuss the implications for stratigraphy, palaeoenvironmental reconstructions and carbon cycling.

How to cite: Nohl, T., Kocsis, A., and Balthasar, U.: Trends in Aragonite Dissolution through the Phanerozoic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17026, https://doi.org/10.5194/egusphere-egu24-17026, 2024.

EGU24-17478 | Orals | SSP2.1

Geological significance of early cements: insight from laboratory simulated diagenesis 

Julien Douçot, Jean-Baptiste Regnet, Philippe Robion, Jérôme Fortin, Franck Bourdelle, Jérôme Corvisier, Christian David, François Passelègue, and Sylvain Richoz

Little is known about the evolution of petrophysical properties (porosity, permeability, mechanical resistance) associated with the growth of microstructures produced during the early stages of diagenesis. To gain a better understanding of these processes, we set out to recreate the microstructures resulting from early carbonate diagenesis in the laboratory. We reproduce a meteoric phreatic environment by heating a sorted aragonitic ooid sand saturated with distilled water. During an initial phase of mineralogical stabilization, we rapidly observe internal dissolution of the ooids and the formation of a calcitic rim at the periphery of the grains. Dissolution occurs along the laminated structures of the ooids. The outer calcite crystals are regular in shape and size. This is followed by a second phase, in which the internal structure of the oolite disappears. Large, sparitic calcite crystals appear in place of the internal laminations. These two phases can be explained in terms of the evolution of CaCO3 saturation in the fluid, and by a competition between nucleation and crystal growth. In the geological record, those structures are often interpreted as the beginning of burial diagenesis. We show that those features can appear very early in the system and are likely to be the cause of the chemical and thermodynamic isolation of the ooids from the fluid in the pore space. We can also conclude from these observations that the creation of internal porosity inside grains is very early, and can appear in a stationary fluid, at shallow depth.

How to cite: Douçot, J., Regnet, J.-B., Robion, P., Fortin, J., Bourdelle, F., Corvisier, J., David, C., Passelègue, F., and Richoz, S.: Geological significance of early cements: insight from laboratory simulated diagenesis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17478, https://doi.org/10.5194/egusphere-egu24-17478, 2024.

The Cambro-Ordovician Cow Head Group is an allochthonous sedimentary succession situated in the Humber zone of Western Newfoundland, the westernmost outer domain of the Appalachian orogenic belt in North America. It records submarine carbonate and rare siliciclastic deposits on a fault-bounded basin Laurentian margin shelf. It is characterized by interstratified carbonate conglomerate, mudstone, grainstone, packstone, wackestone, and lime mudstone. Mega-conglomerate along the Cambro-Ordovician boundary with anomalously coarse clasts are attributed to slope failure of the adjacent carbonate platform. While most authors agree that the transport and deposition of mega-conglomerate was related to seismicity and slope failure, their sedimentation have also commonly been linked to eustatic regression.

To try and better understand the tectonic vs. eustatic forces driving the stratal evolution of the Cow Head Group, detrital zircon U-Pb ages were obtained from the Furongian Tuckers Cove and coeval Martin Point members of the Cow Head Group, and used to better constrain the tectonic, eustatic, and stratal evolution of the Laurentian passive margin. The Tuckers Cove Member is particularly significant due to its record of quartz sand influx into an otherwise carbonate- and mud-dominated basin, and because it underlies megaconglomerate sedimentation linked to terminal Cambrian faulting. Moreover, its sedimentation was coeval with the Furongian Steptoean positive carbon isotope excursion (SPICE), and with shelf regression and the delivery of quartz sand documented in otherwise carbonate-dominated intracratonic basins throughout Laurentia, including in central Iowa, Utah, and coeval shelf carbonates in Western Newfoundland. Such a correlation is supported by preliminary detrital zircon U-Pb results from the Tuckers Cove and Martin Point members, revealing a mixture of typical Laurentian cratonic populations including Archean (ca. 2.73 Ga), Paleoproterozoic (ca. 1.9 Ga), Mesoproterozoic (ca. 1.1 Ga), and Neoproterozoic (ca. 593 Ma) detrital zircons. This implies continental-scale erosion and sediment flux, with sediment sourced from a widespread Laurentian cratonic catchment during the Furongian, including Archean and Proterozoic sources like the Superior, Makkoviak and Grenville provinces, and Ediacaran rift-related strata from the western Newfoundland - Quebec Appalachians. At present these zircon data do not resolve tectonic versus eustatic controls on Cow Head Group sedimentation. Nevertheless, they validate the concept of continental-scale weathering, drainage, and clastic sedimentation across Laurentia during the Furongonian. More work is needed to understand the relationship between such punctuated and widespread sediment generation and Late Cambrian plate tectonics, eustasy, and SPICE.

How to cite: Iturralde, J. and Lowe, D.: New U-Pb detrital zircon ages from the Upper Cambrian – Lower Ordovician Cow Head Group in the Humber Arm allochthon, Western Newfoundland: continental-scale drainage, local deformation, and global stratigraphy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17985, https://doi.org/10.5194/egusphere-egu24-17985, 2024.

EGU24-19152 | Orals | SSP2.1

What drives the structure of the stratigraphic record? A registered report study using forward modelling 

Emilia Jarochowska, Johan Hidding, Peter Burgess, Xianyi Liu, Niklas Hohmann, Hanno Spreeuw, and David De Vleeschouwer

The structure of the sedimentary record comprises the information which parts of the geological history are preserved and what physical record represents this history. Different depositional environments and sedimentary basins have different types of time completeness and resolution, which affects what environmental and evolutionary information can be gleaned from them. How time is preserved in rocks is reconstructed under different paradigms, which can yield different – sometimes radically – results for the same geological sections. Two widely contrasted paradigms around the formation of stratigraphic patterns are:

  • external forcing through changes in the orientation and tilt of the Earth’s axis and shape of the Earth’s orbit around the Sun (Milanković cycles), which – through the insolation of Earth’s surface – affect production and erosion of sediments;
  • autocyclicity, which can arise through the alternation of environments forming a mosaic, which is particularly prominent in carbonate settings, where it is reinforced by the dispersal and competition between sediment-producing biota.

We use carbonate forward models to create virtual stratigraphic architectures representing these two possibilities or their mixtures. As a “null model” we use architectures driven by a stochastic sea-level change, in this case an Ornstein-Uhlenbeck process, to account for the possibility that neither of these two paradigms allows us to obtain realistic stratigraphic patterns or that their stratigraphic expression is not implemented realistically.

Our study consists of two parts:

  • a registered report which describes how the stratigraphic architectures are produced, processed using the admtools package for the R software and then classified without supervision with respect to their driving mechanism,
  • an implementation using a newly developed Open Source model of carbonate platform growth, CarboKitten.jl, inspired by previous models, CarboCAT and CARBONATE 3D.

Such design allows reproducing the study using other forward models, such as SedFlux, either representing different depositional environments or using different algorithms to construct the same environment. It does not exhaust possible drivers of time-preservation in rocks. For example, it does not yet allow to account for diagenetic self-organization, i.e. stratigraphic patterns emerging post-deposition, nor lags of the climate system associated with processes such as ice dynamics. However, it allows to explore how time-completeness and distribution of gaps affects reconstructions of environmental and evolutionary processes. The forward modelling approach allows for testing hypotheses on the mechanisms of the formation of stratigraphic record in a reproducible way.

How to cite: Jarochowska, E., Hidding, J., Burgess, P., Liu, X., Hohmann, N., Spreeuw, H., and De Vleeschouwer, D.: What drives the structure of the stratigraphic record? A registered report study using forward modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19152, https://doi.org/10.5194/egusphere-egu24-19152, 2024.

EGU24-19418 | ECS | Posters on site | SSP2.1

How does subaerial erosion of carbonate platform distort the sedimentary record? 

Xianyi Liu, Johan Hidding, Niklas Hohmann, Peter Burgess, David De Vleeschouwer, and Emilia Jarochowska

Carbonate platform strata have been extensively utilized to decipher geological history. However, due to the fluctuating ambient environment and the complex growth pattern of carbonate factories, preserved records are generally incomplete. For example, given the platforms are located in shallow water environment, they are prone to subaerial denudation when the sea level falls. Numerical modelling is a popular approach to examine spatial and temporal heterogeneities of carbonate platform architectures. While growth and submarine transportations that have been extensively considered, surprisingly, substantially less efforts have been invested to subaerial denudation and its effects on 3-dimentional carbonate platform architecture (e.g., the denudation rates are simplified to constant dissolution rates regardless of the varying ambient environment and local geomorphology).

Herein, we implemented a model with chemical dissolution and physical erosion, calibrated with 35Cl (a geochemical proxy used to estimate kyr-scale denudation) karst regions into CarboKitten.jl (https://mindthegap-erc.github.io/CarboKitten.jl/), a new open-source carbonate platform model. We compared the outputs of models with and without the denudation by using mathematical tool (LBP method) and assessed how the presence of denudation distorts the age-depth relationships. We find that the inclusion of denudation could increase both temporal and spatial heterogeneities, which may decrease the estimation biases on age-depth model. Our results emphasize the importance of considering subaerial denudation in reconstructing geological histories. This study provides a comprehensive framework for refining interpretations and enhancing the accuracy of paleoenvironmental reconstructions based on carbonate platform sediments.

How to cite: Liu, X., Hidding, J., Hohmann, N., Burgess, P., De Vleeschouwer, D., and Jarochowska, E.: How does subaerial erosion of carbonate platform distort the sedimentary record?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19418, https://doi.org/10.5194/egusphere-egu24-19418, 2024.

EGU24-20030 | Orals | SSP2.1

Beyond Look-Up Tables: Unveiling the Potential of Bayesian Theory in Strontium Isotope Stratigraphy for Dating Early Angiosperm Appearance in Portugal 

Francois-Nicolas Krencker, Julia Gravendyck, Rute Coimbra, and Ulrich Heimhofer

Strontium isotope stratigraphy (SIS) relies on comparing the 87Sr/86Sr isotopic ratios of well-preserved samples to a reference curve that depicts the relationship between the 87Sr/86Sr isotopic ratios and geological age. The prevalent approach among stratigraphers utilizing SIS involves employing Look-up tables to compare their measurements with available reference curves. This approach is interesting because it is straightforward, easy to use, and widely accepted within the scientific community. However, Look-up tables exhibit limitations in incorporating geological knowledge, such as biostratigraphy, from the studied horizon. Also, they provide only discrete age ranges, neglecting the full probability distributions describing the age of the samples.

In this study, we present a distinctive method based on Bayesian theory to compare measured isotopic ratios and reference isotopic ratios, aiming to address these shortcomings. We subsequently applied this approach to twelve diagenetically screened bivalve shell samples using petrographic thin sections, cathodoluminescence, micro-X-ray fluorescence, and trace elemental analyses. The samples were collected from three sections located in pre-Aptian coastal marine strata from the Lusitanian Basin of Portugal. These sections are of particular significance due to their richness of unique fossil assemblages and excellent preservation of early angiosperm pollen, the timing of whose origin is still controversial. Our study offers an alternative approach for conducting SIS analyses and suggests an Early Barremian age (124.63–126.24 Ma, GTS2020) for pollen showing unequivocal eudicot angiosperm features collected in Portugal.

How to cite: Krencker, F.-N., Gravendyck, J., Coimbra, R., and Heimhofer, U.: Beyond Look-Up Tables: Unveiling the Potential of Bayesian Theory in Strontium Isotope Stratigraphy for Dating Early Angiosperm Appearance in Portugal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20030, https://doi.org/10.5194/egusphere-egu24-20030, 2024.

EGU24-21298 | Posters on site | SSP2.1

UPPER CRETACEOUS SCAGLIA TYPE LIMESTONE FROM KLEPA Mts. (NORTH MACEDONIA) – SEDIMENTOLOGY AND BIOSTRATIGRAPHY 

Violeta Gajić, Milena Dunčić, Ana Mladenović, and Dejan Prelević

The research area is located in the central part of North Macedonia, in the area of the Klepa Mts. Based on sedimentological, micropaleontological and biostratigraphical investigations of samples from both the east and west side of the Klepa Mts., sedimentary rocks of the Upper Creaceous age are determined. During the latest Cretaceous, this area was dominated by the sedimentation of dominantly carbonate rocks with variable amounts of clastic components.
From the tectonic point of view, investigated area belongs to the contact zone between the Adriatic microplate (on the west) and the Eurasian margin (on the east). This contact zone is represented by a relatively wide area, that evolved in the form of tectonically active sedimentary basins due to a convergence between the aforementioned tectonic plates. However, the nature of this contact zone, also known as the Sava-Vardar zone, which extends along the central part of the Balkan Peninsula, is still a matter of debate. The traditional view explains the Sava – Vardar zone as the remnant of the Late Cretaceous oceanic domain, which subducted under the Eurasian plate and initiated the formation of the Banat-Timok-Srednjegornje volcanic arc. Nevertheless, based on the study of several Upper Cretaceous basaltic occurrences within the Sava-Vardar zone, it is concluded that they are of an intraplate origin. Following that, if we assume that this traditional point of view for the contact zone is true, these basalts should be interpreted as being formed in the forearc region. Alternatively, if these basaltic occurrences are of intracontinental origin, they can be interpreted as being formed in the area of a diffuse tectonic zone between the Adriatic microplate and the Eurasian plate, that was suitable for the formation of pull-apart basins.
Investigated carbonate rocks are represented by reddish, locally pinkish, or grey, light-gray hemipelagic and pelagic biomicrites with very rich planktonic and benthic foraminiferal associations and other diverse micro- and macrofossil assemblages (calcareous nannoplankton, calcified radiolarians, palynomorphs, inoceramids, as well as reef-fossil detritus, transported to deeper parts of the basin). According to biostratigraphical analysis, defined units of scaglia type limestones of the Klepa Mts. implied that basin formation began during late Santonian.
A study of lithological and stratigraphical characteristics on the field, as well as the determination of a very rich association of the Upper Cretaceous fossils, indicate constant sedimentation from the late Santonian to early Maastrichtian time in the area of the Klepa Mts. Palaeoecological characteristics of the determined association of planktonic foraminifers indicate relatively deep sedimentation (~300 m) of the studied limestones, with periodical changes in bathymetry.

Acknowledgement: This research was financed by the Science Fund of the Republic of Serbia through project RECON TETHYS (7744807).

How to cite: Gajić, V., Dunčić, M., Mladenović, A., and Prelević, D.: UPPER CRETACEOUS SCAGLIA TYPE LIMESTONE FROM KLEPA Mts. (NORTH MACEDONIA) – SEDIMENTOLOGY AND BIOSTRATIGRAPHY, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21298, https://doi.org/10.5194/egusphere-egu24-21298, 2024.


The Corinth Gulf is a young, active rift with high rates of tectonic activity, high sediment fluxes, and a closed drainage system. The Gulf is currently connected to the Ionian Sea and the Mediterranean Sea by the Rion Sill and Acheloos-Cape Pappas Sill in the west (currently at 60 m and 55 m below sea level, respectively), and the Corinth Canal (completed in 1893) in the east. During glacial lowstands, the sea level dropped below the sill height and separated the Gulf from the Mediterranean The International Ocean Discovery Program (IODP) Expedition 381 focused on sampling sediments in the Corinth Basin to better understand past environmental changes, especially during glacial to interglacial transitions. Ostracode assemblages have been studied from the sediment core M0078, drilled in the center of the basin to a depth of 610 mbsf. This study relies on benthic ostracodes, which are persistent in the core and inform large changes in chemical-physical parameters and water depth within the basin We find ostracode fauna are particularly sensitive to environmental conditions driven by global sea level oscillations, which cause the Gulf of Corinth to be connected or isolated from the Mediterranean and therefore global oceans. In core M0078, ecosystem shifts are documented by coeval changes in the ostracode assemblages, reflecting variations in water depth (deep-shallow marine environments) degree of confinement-salinity (marine-lacustrine environments).
Two different types of assemblages have been identified from the ostracode assemblages: Mediterranean marine (Cytheropteron spp.; Henryhowella spp.; Aurila spp.; Cytherois spp.) and brackish with Black Sea influences (Amnicythere spp.; Tuberoloxoconcha spp.; Candonidae). Thirteen environmental-ecological stages followed one another crossing six tipping points that mark changes in relative sea level (RSL), climate and/or fluvial regime. Such faunal turnovers identify glacials (brackish assemblage, low sea level) and interglacials (marine assemblage, high sea level) and indicate a complex history of sea level changes that changed the drainage and depth of the Corinth Gulf during the Quaternary. 

How to cite: Parisi, R., Mazzini, I., and Cronin, T. M.: Glacial-interglacial faunal shifts in rift ecosystems during the Quaternary: dynamics and drivers of change from the Corinth Gulf record (Greece)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21621, https://doi.org/10.5194/egusphere-egu24-21621, 2024.

EGU24-637 | ECS | Orals | SSP2.2

Grooves in the heart of glacial reconstructions: how to distinguish ice stream beds and iceberg keel ploughmarks in Earth's ancient glacial record 

Sharman Jones, Marie Busfield, Daniel Le Heron, Tom Holt, and Neil Glasser

We investigate the origin of an exceptionally well-preserved Late Palaeozoic soft-sediment glacial pavement at Oorlogskloof, South Africa and make a palaeoenvironmental reconstruction of deglaciation at this time. Elongate bedforms exposed at the base of the Dwyka Group have previously been interpreted as subglacial flutes and used as evidence of a fast-flowing soft-bedded ice stream. However, analysis of near-identical bedforms of a similar age in Brazil have revealed formation through iceberg ploughing in a shallow glaciomarine environment, warranting re-examination at Oorlogskloof. Fine-resolution orthomosaics and digital terrain models generated from aerial and ground-based structure-from-motion, coupled with field observations, were used to undertake detailed geomorphological mapping of landforms at the site. Elongate bedforms (oriented ESE-WNW) include V-shaped grooves and striations, tapered flutes, and sharp crested asymmetrical ridges with centimetre-scale sediment gravity flow lobes on their slopes. These are accompanied by arcuate push ridges with elongate limbs which parallel the adjacent bedforms. We propose the elongate features were streamlined by a grounded iceberg keel in a shallow marine environment, where the convex core of the arcuate push ridges indicates scouring towards the WNW. Asymmetrical ridges are interpreted as lateral berms since the preservation of sediment gravity flow lobes on their gently dipping slopes necessitates an unconfined substrate at the margins of the grounded iceberg keels. These features further testify to the soft sediment condition of the pavement at the time of bedform formation. Our analysis reveals a pavement formed by iceberg ploughing near a dynamic, retreating ice sheet margin and contests the evidence for an LPIA ice stream positioned over this site, with key implications for locating the position of the palaeo-ice margin over this region of Gondwana. We contend that the site also serves as a valuable sedimentary analogue for contemporary and Pleistocene deglacial landsystems that remain largely inaccessible on today's seafloor.

How to cite: Jones, S., Busfield, M., Le Heron, D., Holt, T., and Glasser, N.: Grooves in the heart of glacial reconstructions: how to distinguish ice stream beds and iceberg keel ploughmarks in Earth's ancient glacial record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-637, https://doi.org/10.5194/egusphere-egu24-637, 2024.

Marine black shale in the Lower Cambrian Qiongzhusi (QZS) Formation in the southwestern Yangtze Plate, SW China, is the primary focus for shale gas development. The formation of organic-rich shale is significantly influenced by the paleoenvironment. Through the analysis of major, trace and rare earth elements (REE), the authors examined the element composition, paleoweathering and provenance of Qiongzhusi black shale (QZS shale). The results revealed that the main components of the Qiongzhusi Formation sample are SiO2, Al2O3 and total Fe2O3 (TFe2O3), with the average values of 64.08 wt%, 15.00 wt% and 5.39 wt%, respectively. Redox-sensitive elements, such as V, Cr, Ni, Zn and U, are richer in QZS shale contrasted with the upper continental crust (UCC). The total concentration of REE (∑REE) of QZS shale is 174.58 ppm on average, which is higher than that of UCC (average 146.37 ppm) and the North American Shale Composite (NASC) (average 173.21 ppm). The ratios of w(SiO2)/w(Al2O3) and w(Al2O3)/w(TiO2), the Zr-TiO2 diagram, the Th/Sc vs Zr/Sc plot, the discriminant function of F1 vs F2 and F3 vs F4, as well as the discrimination diagram of ∑REE vs La/Yb indicated that the main provenances of QZS shale are sedimentary and felsic igneous rocks. The values of a chemical weathering index, the chemical index of alteration (CIA), of the Lower QZS Formation (Stage 1) range from 51.84 to 64.33, indicating a low degree of chemical weathering and a cold and dry climate. The CIA values of the Upper QZS Formation (Stage 2) range from 66.58 to 82.42, suggesting a medium degree of chemical weathering, lilely in a humid climate.

How to cite: Fang, Z. and Guo, L.: Geochemistry of marine black shale of Cambrian Qiongzhusi formation, Yangtze plate, southwestern China: implications for provenance and paleoweathering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1923, https://doi.org/10.5194/egusphere-egu24-1923, 2024.

Biogeochemical models, such as COPSE and cGENIE, have been used to predict the carbon cycle response to emissions into the atmosphere under various forcing scenarios. However, there is still significant uncertainty over model predictions of the magnitude of organic carbon burial into ocean sediments. This limits our understanding of C cycle feedbacks during periods considered to be potentially analogous to current anthropogenic induced climate change.

Stable cadmium isotopes (ẟ114Cd) have potential as a palaeoproxy for organic carbon burial in marine settings, due to the fractionation of Cd during burial in association with organic carbon. Therefore, the generation and evaluation of ẟ114Cd records in organic-rich shale sections encompassing periods of climatic and/or environmental change in the geological past is likely to be a useful tool in tracking and quantifying organic carbon burial trends during such events.

Here we present stable cadmium isotope records from four sections of organic-rich shales covering the Palaeocene-Eocene Thermal Maximum (PETM) occurring around 55.9 Ma, which is both the most recent and most analogous interval of rapid climate fluctuations in the geological record to modern-day climate change. We evaluate these records in terms of their organic carbon burial signals (and so carbon removal from the Earth system) during the lead-up to, onset, peak and recovery of the PETM event, as an initial assessment of the ability of stable cadmium isotopes to trace this process. Better quantification of organic carbon burial will enable the responses of the Earth System to rapid climate change to be better understood. 

How to cite: Elms, H. and Dickson, A.: A stable cadmium isotope perspective on organic carbon burial trends during the Palaeocene-Eocene Thermal Maximum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3530, https://doi.org/10.5194/egusphere-egu24-3530, 2024.

The sedimentary successions provide direct evidence of climate and environment, which offer clues to the cause of the great transition from marine to terrestrial in the Early Carboniferous-Late Permian in the Ordos Basin. The eastern Ordos Basin's early Carboniferous-late Permian strata are sequentially stratified in ascending order as the Benxi Formation of the early Carboniferous, the Taiyuan Formation of the late Permian, and the Shanxi Formation of the late Permian. The Benxi Formation is composed of mudstone with a large number of siderite concretions, carbonaceous mudstone, rhythmic layers of siltstone and mudstone, and coal. The rhythmic layers indicate depositional products of lagoon and tidal flat. The Taiyuan Formation comprises carbonate and clastic sedimentary record, which lithology is mainly biological detrital limestone, limestone with chert nodules, mudstone, coal, and locally sandstone, indicating a shallow-sea shelf depositional environment. The lower part of the Shanxi Formation is a lithological combination of black mudstone, and purple-red sandy mudstone rhythmic layers interbedded with sandstone and coal seams. The black shale contains both marine biological detrital and terrestrial plant fragments. The sandy mudstone rhythmic layers have developed a large number of tidal beddings (such as flaser bedding, wave bedding, and lenticular bedding). The upper part of the Shanxi Formation is mainly depositional in the delta front-plain system. The lithology is mainly fine-coarse grained sandstone, sandy mudstone interbedded with carbonaceous mudstone containing plant fossils and coal seams. Overall, the palaeoenviroment changes from humid-semihumid to arid-semiarid are recorded by the transition from shallow-sea shelf to tidal flat-lagoon to delta deposition records. This study has established the sedimentary facies sequence of the late Carboniferous-early Permian by investigating five typical outcrops on the eastern margin of the Ordos Basin, and analyzed the paleoenvironmental characteristics of the Benxi Formation-Shanxi Formation based on geochemical methods. In addition, we believes that the Shanxi Formation has not completely transformed into terrestrial deposits in the southeastern part of the basin, and it is still in a transitional marine-terrestrial depositional environment.

How to cite: Peng, S. and Feng, C.: The transition from marine to terrestrial in the Early Permian : Evidence from the Early Carboniferous-Late Permian sedimentary records of the eastern margin of the Ordos Basin, North China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4221, https://doi.org/10.5194/egusphere-egu24-4221, 2024.

At present, the geothermal resources developed and utilized in the Guanzhong Basin are mainly Cenozoic sandstone and glutenite pore -fissure geothermal resources, and the development and utilization horizons are mainly Neogene thermal reservoirs. The occurrence characteristics of geothermal resources, the amount of geothermal resources, and the distribution of favorable areas for geothermal resources development are closely related to the provenance and paleo-sedimentary environment. Identifying the characteristics of Neogene mudstone provenance and paleo-sedimentary environment is helpful to indicate the characteristics of sandstone provenance and paleo-sedimentary environment in the same sedimentary period, which is of great influence for the investigation and development and utilization of geothermal resources in the Guanzhong Basin. The geochemical characteristics of elements in sedimentary rocks record important information of provenance and sedimentary environment. Based on the characteristics of major elements, trace elements and rare earth elements of Neogene mudstone core samples in Guanzhong Basin, the provenance and sedimentary environment were comprehensively studied. The results show that the tectonic setting of the source area of the Neogene mudstone in the Guanzhong Basin is mainly the active continental margin, and the source rocks are mainly the Taibai syenogranite and the Huashan biotite monzonitic granite in the northern of the basin, which contain some intermediate-basic igneous rocks. The chemical alteration index (CIA) is between 61.34 and 76.78, with an average of 70.78, reflecting that Neogene mudstone has undergone moderate weathering, indicating that the climate of Gaoling Group and Lantian-Bahe Formation is in a warm and humid climate environment during the sedimentary period, and the climate of Zhangjiapo Formation sedimentary period is transformed from warm and humid climate to cold and dry climate. Geochemical indicators comprehensively reflect that the Neogene mudstone deposition period is mainly in the reducing environment, and the paleosalinity of the water body is generally in a freshwater and brackish water environment. Finding out the provenance and paleo-sedimentary environment features has practical guiding significance for the calculation of resource quantity, the division of geothermal resources sweet spot area and the determination of key strata for development and utilization in Guanzhong Basin.

How to cite: Lan, H.: Geochemical characteristics of Neogene mudstone in Guanzhong Basin,recovery of provenance and paleo-sedimentary environment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4276, https://doi.org/10.5194/egusphere-egu24-4276, 2024.

The Upper Paleozoic in Gubei area of Jiyang Depression has a good combination of source, reservoir and cap, and has a good exploration prospect. The basic research on sedimentology and geochemistry of Upper Paleozoic restricts the oil and gas exploration of target strata. Moreover, the application of element characteristics is rarely applied, and there is almost no research on the longitudinal sedimentary environment evolution characteristics, and the research on paleo-environment and paleoclimate is not systematic enough. The core of the Upper Paleoozoic core bank in Gubei area was taken as the sample. The NITONXL 2·GOLDD handheld X-ray ore element analyzer of Thermo Scientific was used to test the element content of the sample, and the longitudinal variation rule of trace elements was analyzed. The enrichment degree and ratio of trace elements corresponding to different lithologies indicate the characteristics of paleoenvironment and paleoclimatology. Combined with the analysis of the geochemical characteristics of trace elements and rare earth elements, the core of three Wells (Gubeigu 1, Gubeigu 2 and Yi 136) was systematically measured and the content and ratio of elements were studied. The paleo-salinity, paleo-climate, paleo-water depth and REDOX degree of Upper Paleozoic sedimentary period in Gubei area are systematically discussed, which provides reliable evidence for the recovery of sedimentary environment evolution in this area. Among them, Gubei Gu1 well, Gubei Gu2 well and Yi 136 well are all fresh water deposits of continental facies, indicating arid climate, oxidation environment and shallow water depth.

Keywords: Gubei area; Upper Paleozoic; trace element; paleoclimate; paleoenvironment

How to cite: Zhang, Z.: Analysis of Upper Paleozoic trace element characteristics and paleoenvironmental significance in the Gubei area of Jiyang depression, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4295, https://doi.org/10.5194/egusphere-egu24-4295, 2024.

Volcanic activity is generally accompanied by the widespread deposition of organic matter (OM)-rich sedimentary rocks throughout Earth’s history. However, the inherent connection between OM accumulation in deposits and volcanism remains controversial. In this study, we presented high-resolution organic and inorganic geochemical data of the lower Aptian shales in southern Tibet of eastern Tethys to reveal how volcanic activity affected OM accumulation. Enrichment factors of Mo and U as well as Th/U ratio indicated that the studied shales were deposited under oxic-to-suboxic bottom water conditions. Bioproductivity-related Ba/Al reflected a high biotic productivity during deposition. Multiple geochemical proxies revealed that volcanic material occurred within the lower Aptian deposits and volcanism was prevalent in this time. A significant positive correlation between OM content and bioproductivity proxy, combined with the weak or moderate negative correlations among OM content and redox, sedimentation rate and detrital input indicators, demonstrated that OM accumulation was primarily governed by the surficial bioproductivity level. Significantly, the good coupling of volcanic proxies with OM content and biotic productivity suggested that volcanic activity released abundant nutrient elements (e.g., N and P) into the ocean to stimulate the improvement of bioproductivity in surficial water column and then controlled OM accumulation during sedimentary period. This study underscores that volcanic activity plays a constructive function in OM accumulation by enhancing the bioproductivity during the lower Aptian shale deposition.

How to cite: Nie, Y. and Fu, X.: Effect of volcanic activity on organic matter accumulation: Insights from the lower Aptian shales in the eastern Tethys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4593, https://doi.org/10.5194/egusphere-egu24-4593, 2024.

EGU24-5457 | Posters on site | SSP2.2

Impact of basaltic intrusion on organic-rich clays: organic geochemistry and rock magnetic perspective 

Leszek Marynowski, Dorota Staneczek, and Rafał Szaniawski

We studied the impact of the basaltic intrusion on the Miocene organic-rich clay level found in the Grabiszyce quarry, Lower Silesia, Poland. The clays were deposited under terrestrial conditions, and fragments of fossil wood and small plant debris are often present within them. The total organic carbon (TOC) values range from 4 to 12% depending on the distance from the intrusion and the organic debris content. The vitrinite reflectance values increase gradually from 0.15% to 1.4% close to the intrusion. Gas chromatography–mass spectrometry (GC-MS) results show significant changes with distance from the intrusion. Carbon preference index (CPI) values change from c.a. 1 for samples near the basalt to > 2 for samples about 0.5 m and more from the intrusion. As the distance from the basalt decreases, some biomarker groups disappear, including tricyclic and tetracyclic diterpanes, des-lupanes and des-oleananes, hopenes, ββ-hopanes, oleanenes and sterenes. Moreover, such polar compounds as sitosterol, stigmastanol, α- and β-amirin and fridelan-3-one are only present in samples far from the basalt. In contrast, there is an increase in the content of unsubstituted and methyl derivatives of PAHs as well as stable derivatives of hopanes and steranes near the intrusion. Notable differences caused by the intrusion are documented also by rock magnetic methods. Both in-phase and out-of-phase magnetic susceptibility decreases with the distance from the basalt and with the measured vitrinite reflectance. In addition, magnetic susceptibility values correspond very well with the second applied maturity parameter based on the benzo[e]pyrene/(benzo[e]pyrene +perylene) ratio. Moreover, the elevated temperatures resulted in the formation of fine-grained superparamagnetic magnetite, which is documented by frequency-dependent susceptibility, hysteresis curves and their parameters. The thermal impact of the intrusion on the magnetic mineralogy diminishes at around 20 cm distance from the basalt.

How to cite: Marynowski, L., Staneczek, D., and Szaniawski, R.: Impact of basaltic intrusion on organic-rich clays: organic geochemistry and rock magnetic perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5457, https://doi.org/10.5194/egusphere-egu24-5457, 2024.

EGU24-5501 | ECS | Posters on site | SSP2.2

Tracing the path of ice in northern Namibia: mapping the remnants of long-gone glaciers with photogrammetry in unprecedented resolution 

Ricarda Wohlschlägl, Christoph Kettler, Daniel Le Heron, Paulina Mejías Osorio, and Andreas Nduutepo

The glacial features of the Late Palaeozoic Ice Age (LPIA) in northern Namibia have been disproportionately understudied compared to the southern part of the country. Although some initial insights were gained from mid-20th century expeditions, there has been a significant lack of detailed scientific investigations in the area since then (e.g. Martin & Schalk, 1959). Recent studies have begun to address this gap and aim to reinvigorate research in the region (Dietrich et al., 2021; Fedorchuk et al., 2023, Rosa et al., 2023). 

By utilizing large-scale aerial and close-range photogrammetry, we have been able to meticulously map the beds of vanished glaciers at an unprecedented resolution. Quantitative analyses of macroscale ice flow features, including over 16 000 measurements of striae and crescentic fractures in a single area, enable us to determine the directions of ice movement and allow us to correlate them with the suggested local flow direction of a large-scale paleo-fjord network (Dietrich et al., 2021). Analysing selected areas of potential subglacial bedrock failure on high-resolution outcrop photos and detailed 3D models allows us to determine the influence of meltwater and the overlying glacier on erosional features such as crescentic fractures and joint-bounded scars.

Our findings raise important questions regarding the conditions beneath the glacier, including the phases of glaciation evident in the exposed bedrock, subglacial bedrock failure, and the extent and influence of meltwater activity.

Recent efforts to focus scientific attention on the relatively underexplored northern regions of Namibia present a promising opportunity to enhance the existing understanding of glaciations during the LPIA on Gondwana and to utilize these findings to gain better insights into the development of subsequent glaciations.

How to cite: Wohlschlägl, R., Kettler, C., Le Heron, D., Mejías Osorio, P., and Nduutepo, A.: Tracing the path of ice in northern Namibia: mapping the remnants of long-gone glaciers with photogrammetry in unprecedented resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5501, https://doi.org/10.5194/egusphere-egu24-5501, 2024.

EGU24-6620 | ECS | Posters on site | SSP2.2

Variations in oxygenation, primary productivity, and sea level: Investigating the Faraoni Oceanic Anoxic Event in the Lower Cretaceous 

Stephanie Leone, Martino Giorgioni, Jairo Savian, and Luigi Jovane

The Faraoni Event is considered one of the oldest oceanic anoxic events of the Cretaceous, occurring in the Upper Hauterivian. This event, of short duration (200 to 300 ka) and not globally recognized, exhibits atypical characteristics when compared to larger anoxic events like the OAE 1a. Due to these peculiarities, an in-depth study of this event is of great importance, as it suggests the possibility of the existence of other relevant dysoxic to anoxic events, yet to be recognized and adequately investigated. This study focuses on the Faraoni Event in the Western Tethys, from the Puez section located in the Dolomites Mountains, Northern Italy. It is noteworthy that the studied samples were not black shales, as generally expected in anoxic events, but rather . The research included analyses of elements, elemental ratios, rare earth element analyses, grain size, mineralogy, and magnetic mineralogy of discrete samples.

From the conducted analyses, it was possible to comprehend the Faraoni Event in more detail, with a focus on variations in redox conditions and primary productivity. These analyses highlighted distinctive features of predominantly dysoxic conditions during the event, as well as anoxic and euxinic conditions, occurring punctually. A significant perturbation was observed at the beginning of the event, possibly associated with a rapid sea-level rise, triggering a substantial nutrient input, causing a disturbance of considerable magnitude in the environment, and culminating in euxinic conditions. This nutrient input does not appear to be related to increased chemical weathering or volcanic activity, as proposed by some authors in the literature.

Euxinic conditions occurred only for a short period. Through self-regulation of the system, primarily, and the decrease and/or stabilization of sea-level rise, there is no further evidence of euxinic conditions, but rather . There is evidence that the self-regulation of the ecosystem is crucial for returning to oxic conditions in the face of external variations. High productivity conditions would increase oxygen consumption through the decomposition of organic matter, leading to reducing conditions. This, combined with lower quantities of limiting nutrients such as phosphorus, would, in turn, decrease productivity. This would result in improved oxygenated conditions until the system reached equilibrium, maintaining oxygenation levels as observed before the initial disturbance. This system variation has been termed the "string vibration" and is clearly recognized in this context.

Peculiar deposition conditions of a dysoxic event with euxinic and anoxic moments in limestones, the possible initial trigger of the Faraoni Event, and the importance of the self-regulation of the system are highlighted conclusions in this study.

Key words: Faraoni Event, Lower Cretaceous, OAE

 

How to cite: Leone, S., Giorgioni, M., Savian, J., and Jovane, L.: Variations in oxygenation, primary productivity, and sea level: Investigating the Faraoni Oceanic Anoxic Event in the Lower Cretaceous, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6620, https://doi.org/10.5194/egusphere-egu24-6620, 2024.

EGU24-6919 | ECS | Posters on site | SSP2.2

Ediacaran proximal glaciomarine sedimentation in the Bonavista Peninsula, Avalon Zone (Newfoundland)  

Nicolas Gomez, David Lowe, Andrea Mills, Noah Slaney, and Bill Arnott

Four ice ages characterize the Neoproterozoic icehouse Earth period. The two youngest, Gaskiers and Mortensnes glaciations, correspond to relatively short duration (i.e., <1 Myr) localized glaciations limited to >30° paleo-latitude, but significantly were followed by rapid Ediacaran biota evolution. However, the recognition of their glaciogenic origin is confounded by the coeval intensification of Late Neoproterozoic rifting and breakup of Rodinia that conceivably produced coarse-grained strata with characteristics similar to glacial diamictites. The Gaskiers glaciation (ca. 580 Ma) is best characterized in sedimentary successions exposed on the Avalon Peninsula of southeast Newfoundland, where the Gaskiers Formation records deepwater glaciomarine sedimentation over- and underlain by deep-marine turbidites. However, these deep glaciomarine strata do not provide a direct record of terrestrial glaciation, nor sea level changes that would have coincided with glacial advances and retreats, and thus, their glacial origin has been questioned.

Here, we present a sedimentological and stratigraphic analysis of the correlative shallow glaciomarine Trinity diamictite in the Bonavista Peninsula and associated shallow marine strata of the Rocky Harbour Formation. The Monk Bay Member underlies the Trinity diamictite and consists of stacked 6-to-10 m-thick upward-coarsening, shallow-marine clastic parasequences with rare dropstones, each capped by a gravel transgressive lag. The overlying Trinity diamictite consists of a massive clast-rich diamictite with abundant faceted, flat-iron, stoss-and-lee, or bullet-shaped clasts and rare striated clasts and an overlain by a clast-poor laminated diamictite with dropstones, dump and grounding structures. The overlying King’s Cove North Member comprises a distinctively pistachio-color silicified tuff, >50m thick mudstone succession, and uppermost stratal unit of thick-bedded turbidites.

Parasequences of the Monk Bay and Trinity diamictite units are interpreted as deposits of glacial advance and retreat cycles controlled by glacio-eustatic and glacio-isostatic forces. The gravel-rich transgressive lag capping each parasequence records wave reworking of ice-rafted material. These cycles culminated in the deposition of the Trinity diamictite, marked initially by a continuous rainout, followed by finer-grained fall-out of ice-rafted debris, and finally, glacial grounding. Overlying this, the Kings Cove North facies records glacio-eustatic flooding of the shelf, driven by a glacial retreat that marks the end of the Gaskiers glaciation on the Bonavista Peninsula and coincident glacio-eustatic sea-level rise, which evidently outpaced glacial-isostatic rebound.

How to cite: Gomez, N., Lowe, D., Mills, A., Slaney, N., and Arnott, B.: Ediacaran proximal glaciomarine sedimentation in the Bonavista Peninsula, Avalon Zone (Newfoundland) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6919, https://doi.org/10.5194/egusphere-egu24-6919, 2024.

EGU24-7139 | ECS | Posters on site | SSP2.2

Post-glacial paleoenvironmental changes of sedimentary processes recorded in the contourite drifts of Hupo Basin in the eastern margin of Korean Peninsula, East Sea 

Hyesung Kim, Jangjun Bahk, Junho Jang, Soojin Kim, Gyutae Sim, Jiwon Jeong, and Kyung-Eun Lee

The Hupo Basin is a slope-perched half-graben bounded on the east by the Hupo Bank in the eastern margin of Korean Peninsula. In the western slope of the Hupo Bank, moats, formed by bottom current activity, occur along the base of slope at water depths ranging from 208 to 238 m. Associated drift deposits with the moats which fills the Hupo Basin, thin out as they extend from the moat toward the coast. This study aims to understand post-glacial changes of sedimentary processes in the Hupo Basin, influenced both by transgression and variations in the along-slope bottom current activity based on the sedimentary characteristics of three piston cores acquired along an east-west transect from the drift deposit. 

The core sediments consist of bioturbated mud, bioturbated sandy mud, or muddy sand, which show abrupt upward fining trends after the Last glacial Maximum to about 8 ka, indicating progressively deepening offshore environments during the post-glacial sea-level rise. The overall mean grain sizes of the core sediments exhibit a fining trend towards the Hupo Bank decreasing from 51 μm at the shallowest (161 m) western-most site (P02), to 7 μm at the deepest (182 m) eastern-most site (P01), while the sedimentation rates since ca. 8 ka drastically increase towards the Hupo Bank, ranging from 38 to 104 cm/kyr. Moreover, the mean grain size of the P01 site slightly coarsens since ca. 2.3 ka, exhibiting significant cyclic fluctuations with ca. 100 – 200 yr periods and around 4 μm amplitude.

The spatial temporal variations of grain sizes and sedimentation rates demonstrate how the sedimentary characteristics of shallow water contourites, such as the moat-drift system in the Hupo Basin, can be influenced by an interplay between variations in offshore-directed hydrodynamic conditions and associated along-slope bottom current activity due to sea-level changes. The sedimentary records of the contourite drifts of the Hupo Basin indicate initiation of vigorous bottom current activity in the western slope of the Hupo Bank by the East Korean Warm Current, a branch of Tsushima Warm Current flowing northward along the eastern margin of the Korean Peninsula since ca. 8 ka, with increased variability since ca. 2.3 ka.

How to cite: Kim, H., Bahk, J., Jang, J., Kim, S., Sim, G., Jeong, J., and Lee, K.-E.: Post-glacial paleoenvironmental changes of sedimentary processes recorded in the contourite drifts of Hupo Basin in the eastern margin of Korean Peninsula, East Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7139, https://doi.org/10.5194/egusphere-egu24-7139, 2024.

EGU24-7408 | ECS | Orals | SSP2.2

Change of the locus of organic carbon burial in the aftermath of the Toarcian hyperthermal event: Patterns and drivers 

Alicia Fantasia, Nicolas Thibault, Thierry Adatte, Emanuela Mattioli, Jorge E. Spangenberg, Marcel Regelous, and Stéphane Bodin

Carbon cycle-climate dynamics were nonlinear through Earth’s history, driven by changes in internal and external forcing processes acting on various geological timescales. This study focuses on determining the relationship between volcanism, orbital parameters, and organic carbon burial during the Aalenian (Middle Jurassic) - a pivotal time at the dawn of the Mesozoic Marine Revolution, marked by a disruption of the carbon cycle and major climate shifts. Here, new high-resolution magnetic susceptibility and trace elements data are combined with previously published organic carbon isotopes and total organic carbon data from two sites in France and Chile. Our dataset shows for the first time a temporal coincidence between the major carbon cycle perturbation during the middle–late Aalenian and the onset of enhanced volcanic activity, suggesting a causality link. We propose that volcanic activity triggered a transient warming episode within the long-term Middle Jurassic coldhouse and played a key role in shifting organic carbon burial from the ocean to terrestrial settings. This period therefore contrasts with other Mesozoic carbon cycle perturbations, which generally record enhanced marine organic matter burial in oxygen-depleted environments during volcanism-triggered warming events.

How to cite: Fantasia, A., Thibault, N., Adatte, T., Mattioli, E., Spangenberg, J. E., Regelous, M., and Bodin, S.: Change of the locus of organic carbon burial in the aftermath of the Toarcian hyperthermal event: Patterns and drivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7408, https://doi.org/10.5194/egusphere-egu24-7408, 2024.

EGU24-7567 | ECS | Orals | SSP2.2 | Highlight

Early Cretaceous lignites as archive for continental climates of paleo-Asia 

Fritz-Lukas Stoepke, Ralf Littke, Linda Burnaz, Laura Zieger, Hitoshi Hasegawa, Niiden Ichinnorov, and Ulrich Heimhofer

The late Early Cretaceous interval (121.4 to 100.5 Ma) was characterized by a gradual warming trend superimposed on an already warm greenhouse climate. Whereas the evolution of ocean temperatures during this time interval is relatively well constrained, information on the response of continental interiors to such climatic extremes is limited. Here we report new data from two continental sections (Shivee Ovoo (SVO) and Tevshin Gobi (TSG); Choir-Nyalga Basin) from central Mongolia, which contain thick, lignite-rich successions (Khukhteeg Fm.) bearing an exceptionally well-preserved fossil flora of various pine and redwood species as well as representatives of extinct seed plant lineages. In order to reconstruct the palaeoenvironmental conditions, a combined approach including brGDGT-based palaeothermometry, coal petrology and palynology is applied, complemented by geochemical measurements (TOC, TS, δ13Corg). The investigated lignites show significant differences in maceral compositions with the TSG samples being rich in mineral detritus and mainly composed of huminite. In contrast, samples from SVO show higher fusinite and liptinite content with generally low mineral detrital contribution. The paleotemperature estimates represent the oldest brGDGT analyses obtained from continental strata so far. The new data indicate that the climatic conditions in mid-latitudes of paleo-Asia during the late Early Cretaceous were characterised by mean annual air temperatures of about 12 ± 5°C. Our brGDGT data show lower continental temperatures for mid-latitude paleo-Asia than previously suggested based on modelling. 

How to cite: Stoepke, F.-L., Littke, R., Burnaz, L., Zieger, L., Hasegawa, H., Ichinnorov, N., and Heimhofer, U.: Early Cretaceous lignites as archive for continental climates of paleo-Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7567, https://doi.org/10.5194/egusphere-egu24-7567, 2024.

EGU24-7572 | Orals | SSP2.2

Orbital-scale competition of biogenic carbonate and opal production at the Del Caño Rise in the Indian sector of the Southern Ocean during the late Pleistocene  

Hyuk Choi, Matthieu Civel-Mazens, Xavier Crosta, Isabelle Billy, Tomohisa Irino, Hiroyuki Takata, Sangbeom Ha, and Boo-keun Khim

The Southern Ocean is characterized by various ocean fronts that separate surface waters with different hydrographic properties. Ocean fronts’ position changed over glacial-interglacial cycles, which, consequently, affected surface water properties and productivity through time at any given location. The present study reconstructs changes in biogenic carbonate and opal burial at Del Caño Rise (DCR), Indian Ocean sector of the Southern Ocean, over the last three climate cycles. Based on Accelerator Mass Spectrometry radiocarbon dating of planktonic foraminifera as well as comparison of oxygen isotopes of planktonic foraminifera with LR04 stack, the studied core MD19-3575CQ, located today in the Subantarctic Zone, covers the last ~250,000 years. Biogenic carbonate content shows consistent low values during all glacial periods (average 32.4%) and high values during all interglacial periods (average 61.5%). In contrast, biogenic opal content increased during all glacial periods (average 12.8%), compared to interglacial periods (average 8.5%). TOC exhibited a similar pattern to the biogenic opal content, with higher values during glacial periods (average 0.38%) and lower values during interglacial periods (average 0.17%). The increased biogenic opal content during glacial periods is attributed to enhanced silica supply to surface waters due to northward migration of the Subantarctic Front, possibly shifting north of DCR during these periods. However, the relatively low biogenic opal content in the study area compared to other regions of the Polar Frontal Zone (average 55.6%) suggests insufficient silica supply to support high diatom production. The reduction in biogenic carbonate content during glacial periods is related to the decrease in coccolithophore productivity due to low ocean temperatures (~2ºC) and the competition for nutrients and light with diatoms. Despite the shallow water depth (~2400 m) at the core location, the weakened Atlantic Meridional Overturning Circulation and thickening of the corrosive Southern Ocean bottom waters during glacial times may have increased carbonate dissolution. Our study emphasizes that changes in surface water properties by ocean front’s migration impact on regional productivity, which may influence global biogeochemical  cycles.

How to cite: Choi, H., Civel-Mazens, M., Crosta, X., Billy, I., Irino, T., Takata, H., Ha, S., and Khim, B.: Orbital-scale competition of biogenic carbonate and opal production at the Del Caño Rise in the Indian sector of the Southern Ocean during the late Pleistocene , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7572, https://doi.org/10.5194/egusphere-egu24-7572, 2024.

EGU24-8380 | Posters on site | SSP2.2

Biomarker record in the Korea Gap (Ulleung Basin) of the southwestern East Sea since the last glacial period  

Yu-Hyeon Park, Jang-Jun Bahk, Jun-Ho Jang, and Boo-Keun Khim

The East Sea, located on the northwest continental margin of the Pacific Ocean, acts an important marine environment sensitive to the global/regional climate change including the East Asian monsoon. GDGT (glycerol dialkyl glycerol tetraether), one of the membrane lipids originated from archaea or bacteria, has been broadly used as a ubiquitous biomarker for the paleoceanogprahic reconstruction. Although the numerous paleoceanographic results in the East Sea have been reported, the GDGT records and its application to the East Sea paleoceanography are still limited. Here we carried out a study of GDGT, testing the applicability of GDGT-derived proxies as a paleoenvironmental indicator and reconstructing the paleoenvironment using a sediment core from the Korea Gap (Ulleung Basin) in the southwestern East Sea. Downcore profiles of GDGT-derived proxies are clearly distinguished in terms of lithology and age, particularly before and after deglaciation. Concerning the seawater temperature reconstruction, the GDGT-derived temperature (TEX86L-temp) change (5~17°C) is larger than alkenone-derived temperature (UK'37-temp) change (11~21°C). Such a different variation between two temperature proxies potentially indicates that they represent the seawater temperature of different water depths. Especially, the TEX86L-temp during the last glacial period was clearly different from the UK'37-temp. The rapid change of TEX86L-temp before and after deglaciation, similar to GDGT[2]/[3], raises the possibility that, in addition to seawater temperature, other factors related to the sea level change may affect TEX86L-temp. Our results suggest that GDGT biomarker record in the Ulleung Basin (southwestern East Sea) is linked to the regional and global change, providing the possible application to reconstruct the paleoenvironmental changes in the East Sea, although care should be taken when interpreting the seawater temperature signal.

How to cite: Park, Y.-H., Bahk, J.-J., Jang, J.-H., and Khim, B.-K.: Biomarker record in the Korea Gap (Ulleung Basin) of the southwestern East Sea since the last glacial period , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8380, https://doi.org/10.5194/egusphere-egu24-8380, 2024.

EGU24-8716 | ECS | Posters on site | SSP2.2

Clay mineralogy and organic matter of Upper Miocene to Pliocene mudstones of the Kampungbaru Formation, Lower Kutai Basin, Indonesia 

Jamaluddin Jamaluddin, Michael Wagreich, and Susanne Gier

The Kampungbaru Formation is considered a potential source rock for petroleum in the Lower Kutai Basin, Indonesia. An integrated approach of organic petrography, total organic carbon (TOC), Rock-Eval pyrolysis, XRD analysis, and clay mineralogy of fifteen outcrop samples obtained from the Upper Miocene – Pliocene Kampungbaru Formation was conducted. The sediment is characterized by heterolithic, laminated mudstone and interbedded sandstone. Sandstones form thin layers and lenses with predominant lenticular to flaser bedding. The mudstone samples of the Kampungbaru Formation generally have total organic carbon (TOC) content between 0.06 to 8.76 wt.%.  The organic matter consists mainly of vitrinite (71 - 79.6 vol.%; avg. 75.3 vol.%), liptinite (16.90 - 27.4 vol.%; avg. 22.15 vol.%), and inertinite (1.5 – 3.50 vol.%; avg. 2.55 vol.%). Tmax values of these Upper Miocene – Pliocene mudstones are below 435 °C and vitrinite reflectance ranges from 0.27 ± 0.05 %Rr to 0.33 ± 0.05%Rr, indicating an immature stage in the diagenesis of kerogen. The pyrolysis data (HI vs. Tmax) show that type III kerogen dominates organic matter with HI values of < 200 mg HC/g TOC and would be expected to generate gas.  All of the organic matter in the samples is inferred to derive from terrestrial plants. Semi-quantitative XRD results of the mudstone samples in the studied section include varying proportions of clay and non-clay minerals. The bulk mudstone samples in the section are dominated by clay minerals (33.4%–63.0%, avg. = 47%), quartz (23.8%–60.5-%, avg. = 37%), and pyrite (6.0%–32.4%, avg. = 16%). The < 2 μm clay fraction consists of kaolinite, illite, mixed layer illite/smectite (I/S), and chlorite. Kaolinite is the most abundant clay mineral encountered in the studied Kampungbaru Formation. Kaolinite content is influenced by the sedimentary lithology setting. Most sediment deposited in the Mahakam Delta likely originates from erosion by the antecedent part of the Mahakam River.

How to cite: Jamaluddin, J., Wagreich, M., and Gier, S.: Clay mineralogy and organic matter of Upper Miocene to Pliocene mudstones of the Kampungbaru Formation, Lower Kutai Basin, Indonesia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8716, https://doi.org/10.5194/egusphere-egu24-8716, 2024.

EGU24-9118 | ECS | Orals | SSP2.2

Alkenone-based sea surface salinity and temperature reconstructions across late Pliocene sapropels from the Eastern Mediterranean Sea 

Isabel van der Hoeven, Katrin Hättig, Eduard Mol, Marcel van der Meer, Rick Hennekam, and Gert-Jan Reichart

The Eastern Mediterranean sapropels were deposited during periods of increased monsoonal runoff, enhanced export productivity, salinity stratification and deep-sea anoxia since the Miocene. The most pronounced sapropels, with total organic carbon (TOC) contents up to 30%, formed during the late Pliocene (3.16-2.94 Ma). It remains enigmatic which environmental conditions caused the deposition of these high-TOC sapropels.

Here, we aim to record spatiotemporal changes in sea surface salinity (SSS) and sea surface temperature (SST) associated with sapropel formation. We use compound-specific hydrogen isotope analysis of C37:2 alkenones (δ²Halkenone) as a proxy for SSS. This proxy is, in contrast to δ18Oforam, independent of temperature and can be applied to organic-rich samples that lack foraminifera. In addition, we use alkenone-based Uk'37 to estimate SSTs. We compare the δ²Halkenone signatures across the strongest late Pliocene sapropels from ODP sites 967 and 969 to that of a slightly younger, lower-TOC sapropel.

The δ²Halkenone value in marls is comparable to modern-day Mediterranean δ²Halkenone values and across the strongest sapropels, the δ²Halkenone shift of 15-35‰ is comparable to that recorded in sapropel S5. This suggests that freshwater forcing was not exceptionally strong during the deposition of the late Pliocene sapropels. However, in the marls prior to the high-TOC sapropel at 2.95 Ma, δ²Halkenone is ~20‰ more depleted and reconstructed SSTs are higher.

We discuss the salinity forcing on sapropel development and investigate if and how initial warmer and fresher surface waters could have affected the formation of this particularly high-TOC sapropel.

How to cite: van der Hoeven, I., Hättig, K., Mol, E., van der Meer, M., Hennekam, R., and Reichart, G.-J.: Alkenone-based sea surface salinity and temperature reconstructions across late Pliocene sapropels from the Eastern Mediterranean Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9118, https://doi.org/10.5194/egusphere-egu24-9118, 2024.

Abstract

The lower Cambrian shale, a significant source rock, has been witness to substantial tectonic and environmental shifts on Earth. However, the correlation between early Cambrian tectonic history and organic matter enrichment (OME) remains elusive. The Sichuan Basin in the northwestern Yangtze Block hosts the largest Precambrian-Cambrian gas field in China. The primary source rocks contributing to this reservoir are mainly the lower Cambrian shales. The organic matter enrichment of the lower Cambrian shale is commonly ascribed to paleoproductivity, redox conditions, localized hydrothermal activity, upwelling currents, and terrigenous inputs. However, organic matter enrichment varies across the Yangtze Block due to different influencing factors. Particularly, little information has been employed to elucidate the tectonic impact on OME in the lower Cambrian shales within the Sichuan Basin. This study presents detrital zircon U-Pb ages and geochemical data obtained from late lower Cambrian shales in the Sichuan Basin, SW China. The black shales exhibited similar chondrite-normalized REE patterns. They display a slightly right-dipping trend in LREE, a gentle slope in HREE, and a significant Eu anomaly in some samples. Additionally, trace elements generally exhibited a slightly right-leaning pattern, with distinct depletions observed in Nb, Ta, Sr, and Ti. These suggest a complex provenance and origin of the Cambrian shales. The maximum deposition ages of YB-10, NHX-22, and O1H-4 samples were 541Ma, 580Ma, and 523Ma, respectively. These samples were analyzed in cumulative scale maps (crystallization and deposition ages), and it was found that the samples all fell into the collision environment. The detrital zircon U-Pb ages signify a novel magmatic activity in a continental arc setting from the Ediacaran to the early Cambrian, acting as a major sedimentary provenance. It suggests that a weakening retreating subduction-related weak extensional basin rather than a passive marginal or foreland basin of the early Cambrian Sichuan Basin, which had led to diminished extensional and broad trough-platform shales. The compiled geochemical data indicate that OME during the early Cambrian was strongly linked to high primary productivity, redox conditions, and detrital input. However, the influence of these factors on organic matter enrichment varied spatiotemporally, likely due to the unstable and variable tectonic-sedimentary environment associated with the retreating subduction event. This case study illuminates the effects of retreating subduction on the differential organic matter enrichment in the platform shales.

Keywords: Cambrian; shale; retreating subduction; organic matter enrichment; tectonic effect; Sichuan Basin

How to cite: Tang, J., Wang, J., and Wu, G.: Tectonic setting and its effect on organic matter enrichment of the lower Cambrian shales in the Sichuan Basin (SW China), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9566, https://doi.org/10.5194/egusphere-egu24-9566, 2024.

EGU24-9655 | Posters on site | SSP2.2

Tracking Palaeotemperatures in Coniacian–Maastrichtian Seas 

Gregory Price and Bryan Low

In this study the stable isotopes of belemnites, are presented from the Coniacian–Maastrichtian interval (~76–66 Ma) derived from the chalks of Yorkshire and Norfolk, UK deposited on the western North Atlantic shelf.  Cathodoluminescence of the belemnite revealed some diagenetic alteration occurring around the margins, central apical canal and prominent fractures, although large portions of the rostra were well preserved. Our oxygen isotope record reveals that during the Coniacian (at ~43 °N) the climate was relatively warm, with maximum mean temperatures of ~26 °C, followed by cooling to <~21 °C during the Campanian and Maastrichtian. This overall stratigraphic trend is similar to other records, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by global mechanisms – likely declining atmospheric CO2 levels. Within our belemnite data, we also observe a decline in δ13C at the Campanian- Maastrichtian boundary, again consistent with other records. This trend has been interpreted as a result of an increased ratio of organic to inorganic carbon was introduced into the oceans driven by increased weathering and reworking of organic-rich sediments exposed on continental shelves during a sea-level fall. The latter related to a build-up of polar ice. Although our oxygen isotope data point to a cooling it does not necessarily point to polar ice formation.  

How to cite: Price, G. and Low, B.: Tracking Palaeotemperatures in Coniacian–Maastrichtian Seas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9655, https://doi.org/10.5194/egusphere-egu24-9655, 2024.

During the Early Cambrian epoch, a sequence of global marine transgressions culminated in the extensive deposition of organic-rich shales across the planet. This phenomenon was especially pronounced over the Tarim Block, where these organic-rich sediments accumulated significantly during this period. However, the paleomarine environment of it is still poorly constrained due to deep burial and the rare samples. We conducted an integrated study of iron speciation, redox-sensitive trace elements(RSTE), and Molybdenum(Mo) isotopes for samples from the Luntan 1 borehole, located in the Lunnan depression. Yuertusi Formation mainly includes mudstone in the lower member (LM) and limestone in the upper member (UM). Iron speciation data (FeHR/FeT, Fepy/FeT) suggest euxinic in the LM and Anoxic-ferruginous conditions in the UM. Whereas the trace-element and Mo isotopic data show more pronounced variation in redox conditions. The LM shows higher trace element concentrations and lower and more variable Mo isotopic composition relative to the UM. Ratios of redox-sensitive trace element(RSTE) concentrations to total organic carbon(TOC) are significantly more variable and higher on average in the LM relative to the UM. The stable and high Mo isotopic composition (about 1.7‰) in the UM may exist Fe-Mn shuttle, varial and lower Mo isotopic composition (about 0.9‰) in the LM reflect to [H2S]aqueous fluctuate with H2S<11μM. The consistency with RSTE/TOC and Mo isotopic composition in the LM implies frequent transient oxygenation during the early Cambrian. Additionally, the Compilation of Mo isotope data from the early Cambrian and earlier times further indicates relatively oxygenated seawater, especially the deep-marine areas during the early Cambrian before reaching a state like modern seawater.

How to cite: Liu, P., Wang, Q., and Tian, J.: Geochemistry and molybdenum isotopes of the Lower Cambrian Yuertusi Formation in Tarim Basin(China): Implications for ocean-redox conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9767, https://doi.org/10.5194/egusphere-egu24-9767, 2024.

EGU24-10012 | ECS | Orals | SSP2.2

Stratigraphic framework and continental weathering evolution of syn-glaciation, inter-glaciation, and post-glaciation during middle-late Neoproterozoic time in the southwestern Tarim Craton 

Haiyan Hu, Qian Liu, Guochun Zhao, Lihui Lu, Dong Shao, Xuyang Cao, Jiahao Jing, and Jingyuan Liu

Two low-latitude glacial events (i.e. the Sturtian and Marinoan glaciations) occurred in the Cryogenian, both of which were known as the “Snowball Earth”. The sedimentary environment and continental chemical weathering recorded in the syn-glacial, inter-glacial, and post-glacial strata are of great significance to investigate the global glaciations and to establish the Earth’s environment evolution in the Neoproterozoic. Well-preserved middle-late Neoproterozoic sedimentary sequences (including the Yalaguzi, Bolong, Kelixi, Yutang, Kuerkake, and Kezisuhumu Formations from bottom to top) have been identified at the southwestern margin of the Tarim Craton. Nevertheless, there was ongoing debate regarding the evolution of sedimentary environments and their comparison to global glaciers. Furthermore, the sedimentary processes of glacial strata and continental chemical weathering remained obscure. This study conducted detailed field investigation, detrital zircon geochronology, and whole-rock major-element composition analysis. The sedimentary environment evolved from a continental to marine environment. The purplish red conglomerate of the Yalaguzi Formation represents alluvial fan facies, and the combination of diamictites and ice-raft debris depositions in the Bolong and Yutang Formations indicates glacial facies. After the deglaciation of the Bolong glaciation, the Kelixi Formation experienced the transition from neritic-littoral to fan delta-littoral. Afterwards, the sedimentary environment changed to the glacial facies of the Yutang Formation and evolved from a littoral-neritic to shore environment of the Kuerkake Formation. By using the mean age of the youngest two or more grains that overlap in age at 1σ (YC1σ (2+)), the maximum deposition age of the Kelixi Formation has been determined to be 662 Ma, which means that the Bolong and Yutang glaciations correspond to the Sturtian and Marinoan glaciations, respectively. The presence of relatively high corrected chemical index of alteration (CIAcorr) values in otherwise low CIA values documented in the Bolong Formation implies the existence of warm-humid intervals during the overall cold climate. The low CIAcorr values recorded in the Yutang Formation are consistent with a cold event in the Marinoan glaciation. The large variety of the CIAcorr values within the Kelixi Formation suggests that continental weathering during the interglacial period exhibited a tendency of (weakly)-strong-moderately-weakly-strong evolution. Notably, the dramatic fluctuation (from weak to strong continental weathering) recorded in the upper member of the Kelixi Formation implies the arrival of the Marinoan glaciation. A sharp CIAcorr increase is observed during the transition periods between the Bolong and Kelixi Formations, as well as the Yutang and Kuerkake Formations, indicating a huge increase in the chemical weathering intensity in the aftermath of the Sturtian and Marinoan glaciations. This suggests that the Sturtian and Marinoan deglaciation might have been associated with intense continental chemical weathering. This work was financially supported by the National Natural Science Foundation of China (grants 42272249 and 41972237) and the Hong Kong Research Grants Council General Research Fund (17307918).

How to cite: Hu, H., Liu, Q., Zhao, G., Lu, L., Shao, D., Cao, X., Jing, J., and Liu, J.: Stratigraphic framework and continental weathering evolution of syn-glaciation, inter-glaciation, and post-glaciation during middle-late Neoproterozoic time in the southwestern Tarim Craton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10012, https://doi.org/10.5194/egusphere-egu24-10012, 2024.

EGU24-10430 | Posters on site | SSP2.2

High precision stable isotope analysis of carbonate and water samples for paleoclimate applications using the Elementar iso DUAL INLET 

Calum Preece, Sam Barker, Mike Seed, Will Price, and Rob Berstan

Paleoclimate research is important for understanding past, current and future climate, providing the data needed to model and predict current and future climate change scenarios. Stable isotope analysis provides an essential tool for gathering past climate information from natural archives such as waters including ice-cores, ground waters, and biological waters; and carbonate materials such as foraminifera and other fossilized carbonates. Due to the often limited and small sample sizes available for stable isotope analysis it is vital that highly precise and accurate analysis can be carried out on the smallest of sample sizes.

Dual inlet technology remains the most precise, accurate and sensitive technique for pure gas, carbonate and water analysis. The Elementar iso DUAL INLET is a valuable tool for paleoclimate applications, enabling the analysis of pure gas samples within an incredibly compact footprint via our powerful lyticOS software suite. The 14-ultra low dead volume valves with bodies machined from a single block of high purity stainless steel and dedicated turbomolecular pump for the changeover valve guarantees zero residual memory effects between reference and sample gas.

The iso DUAL inlet can be optionally enhanced for the automated analysis of carbonate and water samples. With the iso AQUA PREP enhancement, up to 180 water samples can be analysed achieving δ18O precision better than 0.05‰ (1σ, n=10) and δD precision better than 1‰ (1σ, n=10), for any environmental water sample. The iso CARB PREP enhancement enables automated analysis of up to 180 micro-fossil samples for 13C and 18O down to 20μg sample size. For the highest productivity, both carbonate and water analysis can be performed with the iso MULTI PREP enhancement with switching between modes needing simply a change of needle. The IRMS collector configuration can also be upgraded for “clumped isotope analysis” of carbonate materials.

We will highlight the performance of the iso DUAL INLET with carbonate and water functionality across a range of sample types for paleoclimate applications, supporting researchers building a detailed understanding of the past to better inform policy makers for the future.

How to cite: Preece, C., Barker, S., Seed, M., Price, W., and Berstan, R.: High precision stable isotope analysis of carbonate and water samples for paleoclimate applications using the Elementar iso DUAL INLET, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10430, https://doi.org/10.5194/egusphere-egu24-10430, 2024.

The Carnian Pluvial Episode (CPE; ca. 234–232 million years ago) is an interval with increase in humidity and siliciclastic input, which is linked to global warming, enhanced hydrological cycle, water mass hypoxia caused by the eruption of the Wrangellia Large Igneous Province (Wrangellia LIP). Interestingly, preceding the CPE, there were discernible shifts in paleoenvironmental conditions, manifested through fluctuations in detrital, freshwater, and terrigenous higher plant inputs during that period. This investigation employed various methodologies, including organic geochemistry, elemental geochemistry, and mineralogy analysis of the Bagong and Boli La Formation in the Qiangtang Basin (Tibetan Plateau), to study paleoenvironmental evolution preceding the CPE. The aim was to investigate how these conditions influenced the accumulation of organic matter during this timeframe. Oraganic and elemental geochemical proxies indicated a gradual increase in detrital input prior to the CPE. Combined with decreased paleosalinity indicators, we proposed that enhanced continental inputs prior to the CPE could be associated with an intensified hydrological cycle. Framboidal pyrite morphology and size along with redox sensitive trace element content and ratio indicated anoxic to euxinic bottom water conditions during deposition. Persistently low P/Ti and Ni/Al ratios supported a low biotic productivity, which is adverse for organic matter production. The weak relationship between TOC and redox and productivity proxies indicated that organic matter accumulation was not mainly controlled by reducing condition and low primary productivity. We proposed that three-stage (Intervals A, B, and C) paleoenvironmental evolution before the CPE controlled the accumulation of organic matter in the Bagong Formation. This study provides new insights to paleoenvironmental evolution prior to the CPE, which is of paramount interest for a comprehensive understanding of the CPE.

How to cite: Lin, F. and Wang, J.: Paleoenvironment evolution prior to the Carnian Pluvial Episode: Implications for organic matter enrichment in the Qiangtang Basin (Tibetan Plateau), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11795, https://doi.org/10.5194/egusphere-egu24-11795, 2024.

EGU24-12967 | Orals | SSP2.2

Predicting deglacial stratigraphy following Snowball Earth with 3D forward modelling 

Adam Nordsvan, Ross Mitchell, Kohen Bauer, Cody Colleps, and Ryan McKenzie

Rapid eustatic rise during deglaciations should cause sedimentary condensation and depositional hiatuses on marine shelves. Determining the duration of these hiatuses is challenging, especially in sequences that cannot be reliably dated. Recently, it was suggested that a global prolonged hiatus could have ensued following the Neoproterozoic Snowball Earth events. However, the duration and stratigraphic characteristics of these events are uncertain. Here, we utilize 3D stratigraphic forward modelling software DionisosFlow to 1) estimate its duration following a Snowball Earth when considering 800 m glacioeustatic rise over 40 kyr, and 2) explain the stratigraphic fingerprint of such an event. We tested several margin configurations and different sediment flux scenarios; our findings indicate that the duration of the hiatus, as predicted, will increase with accommodation, and decrease with sediment supply. Simulating an average (modern) glaciated margin with an average sediment flux results in prolonged sediment starvation on the outer shelf, lasting over 6 Myr. More complex models show how topography, sediment type, and sediment volume during and after the deglaciation affect the stratigraphic record. We compare the predicted model outputs with observed Snowball Earth stratigraphy from the Kimbereley region of NW Australia to reconstruct the paleoenvironmental conditions. This work demonstrates how 3D stratigraphic modeling can help clarify deglacial stratigraphy.

How to cite: Nordsvan, A., Mitchell, R., Bauer, K., Colleps, C., and McKenzie, R.: Predicting deglacial stratigraphy following Snowball Earth with 3D forward modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12967, https://doi.org/10.5194/egusphere-egu24-12967, 2024.

EGU24-13999 | Posters virtual | SSP2.2

Sedimentary environment of lacustrine mud shale and its control over lithofacies development: A case study of Boxing Sag, Jiyang Depression, Bohai Bay Basin, China 

chuanxin Liu, longwei Qiu, yali Sun, xin Li, yelei Wang, and yongqiang Yang

The sedimentary environment and organic matter enrichment patterns of organic-rich shale are of great significance for the exploration and development of shale oil and gas resources. By using thin section identification, X-ray diffraction, argon ion polishing, scanning electron microscopy, and major and trace element geochemistry experiments, the mineralogy, geochemistry, and paleoenvironmental evolution characteristics of shale rocks in the lower of the third member and upper of the fourth member of the Shahejie Formation of the Boxing Depression were studied. The influence of sedimentary environments such as paleoclimate, paleosalinity, redox conditions, and paleowater depth on lithofacies was discussed.

The research results indicate that:① The shale in the study area is mainly composed of calcite, quartz, and clay minerals, accompanied by dolomite, feldspar, and pyrite. According to the three end element division scheme, the lithofacies of the study area can be divided into six types: rich organic layered calcareous mudstone, rich organic layered calcareous mudstone, containing organic layered calcareous mudstone, containing organic block calcareous mudstone, rich organic layered mudstone, and containing organic layered mudstone② The paleosalinity and paleoclimate determine the macro environment during the sedimentary period, while paleoproductivity and redox conditions control the generation and preservation of organic matter. By using XRF to test the vertical variation of characteristic element content ratio, it can be concluded that the vertical evolution of shale in Boxing Depression has obvious stages in terms of ancient climate, ancient salinity, ancient water depth, water redox properties, and terrestrial input degree. The upper of the forth member of the Shahejie Formation shows that the water body first deepens and then shallows, the climate changes from drought to humidity, salinity gradually decreases, and the terrestrial supply first increases and then decreases; The lower of the third member of the Shahejie Formation is that the water body deepens, the salinity decreases, and the climate becomes humid.③ The type of lithofacies is closely related to the sedimentary environment: the entire stratum  in the upper of the fourth member of the Shahejie Formation of the Boxing Depression experienced lake basin expansion and contraction, which led to the evolution of lithofacies towards a direction where the calcite content first increased, then decreased, and then increased again. The terrestrial detrital minerals first increased and then decreased, and the organic matter content first increased and then decreased, but the overall direction was lower; The lower third member of the Shahejie Formation has experienced rapid subsidence, and the climate and water depth have undergone multiple stages of changes, leading to a trend of increasing terrestrial detrital minerals, decreasing carbonate minerals, and slightly increasing clay minerals in the evolution of lithofacies. This indicates that environmental changes control the evolution of lithofacies.Therefore, paying attention to the evolution of shale sedimentary environment and exploring the response relationship between rock and sedimentary environment can provide new ideas for unconventional oil and gas exploration.

Keywords: lacustrine mud shale; Organic geochemistry; Elemental geochemistry; Paleoenvironmental characteristics; Boxing Depression

How to cite: Liu, C., Qiu, L., Sun, Y., Li, X., Wang, Y., and Yang, Y.: Sedimentary environment of lacustrine mud shale and its control over lithofacies development: A case study of Boxing Sag, Jiyang Depression, Bohai Bay Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13999, https://doi.org/10.5194/egusphere-egu24-13999, 2024.

EGU24-14361 | ECS | Posters on site | SSP2.2

Tracking the Mesoproterozoic Ocean anoxia: Inferences from Mo isotopic study of black shales from Cuddapah Basin, India  

Achyuth Venugopal, Gyana Ranjan Tripathy, Vineet Goswami, and Tavheed Khan

We report new chemical (trace elements and Fe-speciation) and Mo isotopic (δ98Mo) data for a Mesoproterozoic black shale sequence from the Cumbum Formation, Cuddapah Supergroup, India. These datasets have been used to reconstruct the ocean redox state and its areal extent. This reconstruction has significance in addressing the existing diverging views on the linkage between limited eukaryotic diversification and ocean oxygenation during this time period. The shales are comprised of higher organic carbon (1.1 ± 0.2 %) and sulfur (1.0 ± 0.3 %) concentrations, compared to the average upper continental crust (UCC) compositions. Most of the major elements have near-UCC values, except the lower values observed for Na, Fe and Ca. Among the trace elements, high enrichment factors for selected redox-sensitive elements (Mo, U and V) have been observed. Average Mo/TOC values (~6.3 ppm/wt%) of these shales fall close to the Proterozoic mean (~6.4 ppm/wt%). The δ98Mo values of these samples range from 0.43‰ to 1.02‰ with an average of ~0.68‰ which matches well with the Mesoproterozoic average of ~0.67‰. The Fe-speciation data indicates that the iron in these shales is mostly associated with sulfide-rich phases, with minor contribution from other phases. Average FeHR/FeT (0.61 ± 0.18) and Fepy/FeHR (0.72 ± 0.14) values indicate a fluctuating (euxinic to ferruginous) bottom water redox state in the basin. Our preliminary mass balance modelling using the Mo isotopic composition of selected (those deposited in euxinic conditions) shale samples shows that most of the oceanic Mo sink during this time were scavenged through anoxic pathways, with very little removal via oxic phases. An expanded sulfidic environment with rapid removal of bio-essential elements (hence, their reduced availability in the oceans) might have hindered the oceanic productivity and biological expansion.

How to cite: Venugopal, A., Tripathy, G. R., Goswami, V., and Khan, T.: Tracking the Mesoproterozoic Ocean anoxia: Inferences from Mo isotopic study of black shales from Cuddapah Basin, India , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14361, https://doi.org/10.5194/egusphere-egu24-14361, 2024.

EGU24-15256 | Posters on site | SSP2.2

Anatomy of a subglacial “deforming bed” beneath a Late Palaeozoic glacier in Namibia 

Daniel Le Heron, Ricarda Wohlschlägl, Paulina Mejías-Osorio, Christoph Kettler, and Andreas Nduutepo

Namibia is remarkable in terms of its network of 300-million-year-old fjords, cut by Gondwanan glaciers at high palaeolatitudes during the Late Palaeozoic Ice Age. A classic suite of structures is preserved on Proterozoic bedrock, including striations, roches moutonnées and other subglacial features within many of these palaeovalleys. Some palaeovalleys are plastered with comparatively thin diamictites (a few metres) of presumed subglacial origin, in turn capped by paraglacial to postglacial delta successions (tens of metres). Close examination of deposits in the Otjihaa valley reveals an architecture that shows departure from this trend. There, boulder-bearing diamictites pass laterally into highly contorted heterolithic successions comprising folded and faulted sandstones, siltstones and shales. Aerial imagery from UAVs in tandem with traditional field observations permits mapping of (i) highly asymmetric fold structures (tens of metre-scale), (ii) ball and pillow structures, (iii) the orientation of the long-axis of boulders together with (iv) striation orientations, (v) pervasive lineations and (vi) shear bands in sandstone. Collectively, this assemblage of structures points towards subglacial deformation, and hence an origin as a “deforming bed” beneath a glacier. In this paper, we present a synoptic profile along the palaeo-fjord axis charting the architecture of these deposits. The lateral and vertical distribution of different deformation products, together with their orientations, is argued to allow subglacial stresses to be reconstructed, and hence ice flow dynamics to be better understood. In studies of deep time glaciations, the discovery of a significant “deforming bed” cradled within a bedrock palaeovalley is a new development, interrupting the classic deglaciation-transgression sequence established by previous work. 

How to cite: Le Heron, D., Wohlschlägl, R., Mejías-Osorio, P., Kettler, C., and Nduutepo, A.: Anatomy of a subglacial “deforming bed” beneath a Late Palaeozoic glacier in Namibia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15256, https://doi.org/10.5194/egusphere-egu24-15256, 2024.

EGU24-17805 | ECS | Orals | SSP2.2 | Highlight

Taking your breath away with Early Cretaceous Boreal seawater oxygenation 

Carlette N. Blok, Rasmus Andreasen, Emma Sheldon, Mads E. Jelby, Jon Ineson, Kresten Anderskouv, and Stéphane Bodin

Mesozoic Oceanic Anoxic Events (OAEs) were linked to the accumulation of organic-rich sediments in response to global climatic and environmental changes, resulting in transient episodes of oceanic deoxygenation. To better understand the evolution of seawater oxygenation in the Boreal Realm during the Early Cretaceous (late Hauterivian – early Aptian), this study presents high-resolution datasets of Rare Earth Element plus Yttrium (REE + Y; REY) patterns and redox-sensitive trace elemental (RSTE) concentrations in the Danish Central Graben (DCG). Oxygenation in the seawater column can be derived from the Cerium (Ce) anomaly (Ce/Ce*), which is based on the premise that Ce acts differently in well-oxygenated environments compared to the other REYs. At the seafloor, anoxia is indicated by the enrichment of RSTEs Vanadium (V) and Uranium (U). A decline in Ce anomaly values and low RSTE concentrations from the late Hauterivian to late Barremian indicates a shift from an oxygen-depleted to a more oxygenated seawater column and seafloor conditions in the Boreal Realm. A similar trend is observed in the Tethyan Realm, suggesting the existence of a global long-term driver of seawater oxygenation level. In the DCG, this long-term trend is interrupted by a brief drop in relative sea level, leading to partial isolation of the basin, reduced ventilation, stratification of the water column and consequently short-term anoxic conditions at the sediment–water interface. This resulted in the deposition and preservation of an organic-rich layer (Munk Marl Bed) during the early Barremian. During the early Aptian, an organic-rich layer (Fischschiefer Member) of regional extent, linked to the global OAE-1a, was deposited. Significantly elevated Ce anomaly values along with increased concentrations of U and V signify anoxic conditions within this Boreal basin, whereas the seawater column in the Tethyan Realm exhibited dysoxic conditions. Variations in anoxia and the fact that some OAEs are only observed locally, leads to the conclusion that short-term regional or local factors can overprint global changes.

How to cite: Blok, C. N., Andreasen, R., Sheldon, E., Jelby, M. E., Ineson, J., Anderskouv, K., and Bodin, S.: Taking your breath away with Early Cretaceous Boreal seawater oxygenation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17805, https://doi.org/10.5194/egusphere-egu24-17805, 2024.

The Southeast Atlantic Ocean plays a crucial role in the overall circulation of the world's oceans facilitating the transfer of heat and salt into the Atlantic and hosting the productive Benguela Upwelling System. Heat and salt are introduced to the South Atlantic via the Agulhas leakage and thus this leakage is considered important in controlling the strength of the Atlantic meridional overturning circulation (AMOC). In this study we reconstruct sea surface temperatures and salinities using coupled Mg/Ca and δ18Ο of Globigerina bulloides shells from site GeoB 1710-3 offshore Namibia. Our goal is to investigate the paleoceanography and surface ocean circulation patterns in this area during the late Pleistocene (0-250 ka). Furthermore, the chemical investigation is complemented by X-ray μCT measurements of the foraminifera specimens for dissolution assessment, aiding in the interpretation of a perplexing pattern in the G. bulloides shell weight record during the penultimate glaciation. 

How to cite: Zarkogiannis, S., Frankel, J., and Rickaby, R.: Examining surface water conditions over the past 250,000 years off the coast of Namibia: exploring the diverse impacts of Agulhas Leakage and Benguela Upwelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20060, https://doi.org/10.5194/egusphere-egu24-20060, 2024.

EGU24-20349 | ECS | Orals | SSP2.2

Climatic and environmental impacts on source-to-sink processes in SW Taiwan since the last deglaciation 

Christophe Colin, Joffrey Bertaz, Zhifei Liu, Arnaud Dapoigny, Andrew Tien-Shun Lin, Yanli Li, and Zhimin Jian

In recent decades, many scientific studies have been conducted to constrain present and past source-to-sink processes and their controlling factors. The role of typhoon and monsoon summer rainfall on chemical weathering and soils erosion in east Asia is still not well established. Clay minerals and major elements, combined with Nd and Sr isotopic compositions were analyzed on sediments from Core MD18-3569 located close to the Penghu Canyon on the Taiwan margin (northeastern South China Sea) in order to establish climatic and environmental controls on source-to-sink processes and weathering history of small river basins of southwest Taiwan since the last glacial period. The 87Sr/86Sr ratios and ɛNd values of the detrital and clay fractions combined with the high content of illite and chlorite suggest that the mountainous rivers of southwest Taiwan are the main sources of sediments to the Taiwan margin since the last deglaciation. Such results permit to evaluate past intensity of chemical weathering in the rivers of southwest Taiwan from major elements composition and clay mineral assemblages. The long-term changes of chemical weathering intensity in Taiwan are driven by the variations of east Asian summer monsoon rainfall. During the deglaciation, the progressive strengthening of rainfall enhanced the chemical weathering intensity which peaked in the early Holocene. The Holocene is characterized by a decrease of the chemical weathering degree of sediments derived from Taiwan. This coincides with the weakening of summer monsoon rainfall, an increase in typhoon activity, and changes in vegetation cover in southwest Taiwan. These processes caused soil destabilization and erosion, regressive pedogenesis, and weaker chemical weathering intensity. This was due to the shorter residence time of sediments in the soils of southwest Taiwan. Our multi-proxy study highlights the strong link between summer monsoon and typhoon rainfalls, environmental changes, and chemical weathering history in Taiwan.

How to cite: Colin, C., Bertaz, J., Liu, Z., Dapoigny, A., Tien-Shun Lin, A., Li, Y., and Jian, Z.: Climatic and environmental impacts on source-to-sink processes in SW Taiwan since the last deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20349, https://doi.org/10.5194/egusphere-egu24-20349, 2024.

EGU24-20350 | ECS | Orals | SSP2.2

Assessing redox-related biotic changes during the Sinemurian–Pliensbachian transition in the Lusitanian Basin, Portugal 

Marisa Storm, Luís V. Duarte, Peter Kraal, Rick Hennekam, Yuta Isaji, Nanako O. Ogawa, Naohiko Ohkouchi, Stefan Schouten, and Marcel T.J. van der Meer

The geochemical record of the Early Jurassic Sinemurian–Pliensbachian transition (S–P transition; ~193 Ma) is marked by a prominent negative carbon-isotope excursion and a short-lived increase in pCO2. The paleoenvironmental responses to this carbon-cycle disturbance within the Eastern European Seaway are limited to a widespread, but minor increase in organic matter burial when compared to, e.g., the Toarcian oceanic anoxic event. In contrast, coeval deposits from the Água de Madeiros and Vale das Fontes formations, Lusitanian Basin (Portugal), located in the north-western fringes of the Tethys, comprise highly organic-rich black shales. Here, we reconstruct the paleoenvironmental and redox changes in the Lusitanian Basin across the S–P transition (oxynotum to raricostatum Zone), which are transitioning from euxinic to anoxic to oxygenated conditions. We combine major- and trace-element concentrations, biomarker analysis, and compound-specific carbon- and nitrogen isotope data including those of geoporphyrins. We assess the impact of redox changes and associated shifts in nitrogen cycling and bioavailability (e.g. denitrification) on the abundance and species composition of the marine microflora, the compound-specific carbon-isotope record and phytane-based pCO2 reconstructions. The exceptionally well preserved, thermally immature and highly organic-rich succession allows new insights into the characteristics and the local processes governing the development of low oxygen conditions outside the temporal realm of large-scale global warming and widespread ocean anoxia.

How to cite: Storm, M., Duarte, L. V., Kraal, P., Hennekam, R., Isaji, Y., Ogawa, N. O., Ohkouchi, N., Schouten, S., and van der Meer, M. T. J.: Assessing redox-related biotic changes during the Sinemurian–Pliensbachian transition in the Lusitanian Basin, Portugal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20350, https://doi.org/10.5194/egusphere-egu24-20350, 2024.

EGU24-21347 | ECS | Orals | SSP2.2 | Highlight

A plant-wax δD record of palaeohydrology over the Cretaceous–Paleogene boundary 

Lauren O'Connor, Rhodri Jerrett, Appy Sluijs, Gregory Price, Bart van Dongen, Sabine Lengger, and Francien Peterse

Alongside the mass extinction, the Cretaceous–Paleogene (K–Pg) boundary interval experienced major climate perturbations due to the Chicxulub meteorite impact and Deccan Trap volcanism. The volcanism and release of climate modifying gases likely had a drastic effect on global climate, though hypotheses of this change remain largely untested.

Recent work applied the lipid biomarker palaeotemperature proxy MBT'5me to two highly chronologically constrained lignites from the Western Interior, USA (palaeolatitudes 45–51°N). This reconstruction showed that mean annual air temperatures increased by 3°C during the last ~100 ka of the Cretaceous, likely driven by Deccan volcanism and long-term release of organic carbon into the atmosphere. A transient cooling event of up to 5°C is superimposed on to the longer-term warming trend, beginning ~35 ka before the K–Pg boundary. This cooling coincided with the second (Poladpur) eruptive phase of Deccan volcanism, which correlates with the modelled climatic cooling predicted by the release of associated aerosolised SO2 emissions.

To gain a more holistic understanding of the end-Cretaceous climate system, here we use the hydrogen-isotope composition of plant-wax from the same lignites to reconstruct palaeohydrology. Determining the link between volcanism-induced temperature change and hydrology prior to the Chicxulub impact will provide a framework for understanding post-impact hydrological changes.

This work presents the first opportunity to evaluate palaeohydrology at a millennial scale in the Cretaceous, alongside temperature and carbon-cycling. Further, the excellent chronological constraints allow a unique insight into the relative timing of different climatic processes and major climate perturbations in the lead-up to and across the K–Pg boundary.

How to cite: O'Connor, L., Jerrett, R., Sluijs, A., Price, G., van Dongen, B., Lengger, S., and Peterse, F.: A plant-wax δD record of palaeohydrology over the Cretaceous–Paleogene boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21347, https://doi.org/10.5194/egusphere-egu24-21347, 2024.

EGU24-21645 | Orals | SSP2.2

The early Middle Devonian Choteč Event in northern Spain: a brief anoxic pulse driven by enhanced weathering and eutrophication 

David Bond, Silvia Blanco-Ferrera, Stephen Grasby, Sarah Greene, Jason Hilton, Gilda Lopes, Jing Lu, John Marshall, Javier Sanz-López, Charles Wellman, and Lusheng Yin

The (Basal) Choteč Event, first recognised in the 1980s in Czechia, is a globally widespread anoxic pulse associated with transgression and eutrophication just above the Emsian-Eifelian (Early-Middle Devonian) boundary (cycle 1c of the Johnson et al. [1985] Devonian eustatic sea-level curve). Despite being one of several anoxia-driven faunal turnovers during the Devonian, the Choteč Event remains poorly understood. The global reach, intensity, and duration of anoxia is not constrained and nor is it clear whether eutrophication had its “roots” in contemporary floral developments on land (as suggested for younger Devonian anoxic events).

We present a geochemical (carbon isotopes; trace metals as proxies for redox and productivity; and major elements for the Chemical Index of Alteration [CIA] as a weathering proxy) and palynological study of the Cabonera section (León, Spain). This succession is part of an extensive Devonian sequence developed around isolated islands in the Armorican Terrane Assemblage that was located between the supercontinents Laurussia and Gondwana. Here, limestones of the Emsian-Eifelian Santa Lucia Formation are abruptly overlain by siltstones and shales belonging to the Eifelian Huergas Formation. This conodont- and brachiopod-constrained manifestation of the Choteč Event sees the onset of a gradual 4‰ negative δ13Ccarb excursion (CIE) consistent with records in other regions. The lower part of the Huergas Formation (Cabornera Bed) records a brief interval of anoxia (low Th/U, elevated V/Al and U/Al) at the same level that sees the onset of the negative CIE. This appears to have been accompanied by, or was perhaps driven by, greatly enhanced primary productivity, with enrichment factors (EFs) of Ba, and particularly Ni, Zn and P, all >>1. This brief burst of productivity and anoxia soon ended, with EFs falling <<1 through the remainder of the Huergas Formation (which are also well below the values recorded in the Santa Lucia Formation). The CIA values are high throughout the succession, suggesting the prevalence of strong weathering under a warm, humid climate during the Eifelian. The highest CIA values are seen immediately above the level of high productivity and oxygen restriction, suggesting that weathering enhanced further still at that time. A less commonly employed weathering proxy, Rb/Sr, also suggests the onset of enhanced weathering in the Choteč Event beds, where the ratio increases by two orders of magnitude although we cannot rule out the role of facies changes in this.

Acritarch, chitinozoan and spore assemblages are somewhat impoverished and have a moderate-high degree of endemism, which is unsurprising considering their isolated location. More broadly, the Eifelian saw significant diversification in several plant groups. It is possible that these changes on land drove the Choteč Event through enhanced pedogenesis and runoff, but there is a mismatch between the temporal scale of land plant evolution and the brevity of the eutrophic anoxic pulse recorded at Cabornera. Instead, we suggest that the Choteč Event in the Armorican Terrane saw a brief phase of extreme productivity – driven by rapidly enhanced weathering of unknown origins – that resulted in anoxia and the shutdown of the carbonate factory.

How to cite: Bond, D., Blanco-Ferrera, S., Grasby, S., Greene, S., Hilton, J., Lopes, G., Lu, J., Marshall, J., Sanz-López, J., Wellman, C., and Yin, L.: The early Middle Devonian Choteč Event in northern Spain: a brief anoxic pulse driven by enhanced weathering and eutrophication, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21645, https://doi.org/10.5194/egusphere-egu24-21645, 2024.

EGU24-21751 | Orals | SSP2.2 | Highlight

Sulfur and fluorine degassing from Deccan Traps lavas inferred from pyroxene chemistry: potential for end-Cretaceous volcanic winters 

Sara Callegaro, Don R. Baker, Paul R. Renne, Leone Melluso, Kalotina Geraki, Martin J. Whitehouse, Angelo De Min, and Andrea Marzoli

The Cretaceous-Paleogene (K-Pg) mass extinction was a pivotal event in Earth's history and is attributed to the interplay of two major events—the Deccan Traps volcanism and the Chicxulub asteroid impact. We contribute to refine of our understanding of the volcanic stressor for this extinction by investigating the sulfur and fluorine budgets of Deccan lavas from the Western Ghats (India), spanning the K-Pg boundary [1].

Sulfur and fluorine concentrations were analyzed in clinopyroxene phenocrysts from Deccan Traps lavas, by Synchrotron-light X-ray fluorescence (beamline I18, Diamond Light Source, U.K.), and ion probe (CAMECA IMS 1280 at Nordsim Laboratory, Swedish Museum of Natural History, Stockholm, SE), respectively. The results were divided by experimentally determined partition coefficients to calculate melt concentrations.

Our analyses reveal variable magmatic volcanic fluorine concentrations ranging from 400 to 3000 parts per million, suggesting the potential for regional environmental impact. The highest sulfur concentrations, reaching up to 1800 parts per million, are observed in Deccan lavas emplaced just prior to the extinction interval, within a timeframe of 0.1 million years. In contrast, later basalts generally exhibit lower sulfur concentrations, only up to 750 parts per million.

Independent evidence [2] supports that eruption of the Deccan flood basalts occurred in multiple voluminous eruptive pulses each lasting on the order of centuries, as typical of continental flood basalts. Our findings propose that the volcanic sulfur degassing associated with such activity may have led to repeated, short-lived global temperature drops, too short to be recorded by global paleotemperature record, albeit coupled with a global cooling trend. Sulfur-induced cold snaps likely imposed stress on ecosystems long before the decisive impact of the Chicxulub bolide at the end of the Cretaceous.

 

[1] Sara Callegaro, et al., (2023) Recurring volcanic winters during the latest Cretaceous: Sulfur and fluorine budgets of Deccan Traps lavas. Sci. Adv. 9, eadg8284 doi:10.1126/sciadv.adg8284.

 

[2] I. M. Fendley, et al., 2019. Constraints on the volume and rate of Deccan Traps flood basalt eruptions using a combination of high-resolution terrestrial mercury records and geochemical box models. Earth Planet Sci Lett. (524) 115721. 

 

How to cite: Callegaro, S., Baker, D. R., Renne, P. R., Melluso, L., Geraki, K., Whitehouse, M. J., De Min, A., and Marzoli, A.: Sulfur and fluorine degassing from Deccan Traps lavas inferred from pyroxene chemistry: potential for end-Cretaceous volcanic winters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21751, https://doi.org/10.5194/egusphere-egu24-21751, 2024.

EGU24-5046 | Posters virtual | SSP2.7

Combining orbital tuning and direct dating approaches to age-depth model development for Chew Bahir, Ethiopia 

Martin H. Trauth, Markus L. Fischer, Verena Foerster, Norbert Marwan, Helen M. Roberts, and Frank Schaebitz

The directly dated RRMarch2021 age model (Roberts et al., Quaternary Science Reviews, 2021) for the ~290 m long composite core from Chew Bahir, southern Ethiopia, has provided a valuable chronology for long-term climate changes in northeastern Africa. However, the age model has limitations on shorter time scales (less than 1–2 precession cycles), especially in the time range <20 kyr BP and between ~155–428 kyr BP. To address those constraints we developed a partially orbitally tuned age model. A comparison with the ODP Site 967 record of the wetness index from the eastern Mediterranean, 3,200 km away but connected to the Ethiopian plateau via the River Nile, suggests that the partially orbitally tuned age model offers some advantages compared to the exclusively directly dated age model, with the limitation of the reduced significance of (cross)spectral analysis results of tuned age models in cause-effect studies. The availability of this more detailed age model is a prerequisite for further detailed spatiotemporal correlations of climate variability and its potential impact on the exchange of different populations of Homo sapiens in the region.

How to cite: Trauth, M. H., Fischer, M. L., Foerster, V., Marwan, N., Roberts, H. M., and Schaebitz, F.: Combining orbital tuning and direct dating approaches to age-depth model development for Chew Bahir, Ethiopia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5046, https://doi.org/10.5194/egusphere-egu24-5046, 2024.

EGU24-5407 | Posters on site | SSP2.7

Geotectonic Influences on the Lake Elementeita Ecosystem (Central Kenya Rift): Insights from Field and Space-Based Observations 

Simon Kübler, Carolina Rosca, Annett Junginger, Veronica Muiruri, and Mugabo Wilson Dusingizimana

In the backdrop of the global freshwater crisis exacerbated by human activities and climate change, our study addresses the need to understand the forces shaping lacustrine ecosystems in Eastern Africa, particularly within the East African Rift System (EARS). The Lake Elmenteita basin in the Central Kenya Rift represents the intricate interplay between intense geotectonic forces and escalating human activities. This study aims to unravel the complex interactions shaping this critical ecosystem, with a particular emphasis on the geotectonic aspects that underpin the lake's environmental dynamics. Lake Elmenteita is ecologically vital, supporting a diverse habitat including numerous bird species and serving as a primary food source for up to half a million flamingos.

Our research employs a multidisciplinary approach, integrating tectonic geomorphology, geological remote sensing, geochemistry, soil science, and micropaleontology. This approach is designed to differentiate the lake's natural geological influences from anthropogenic impacts.

Field investigations have demonstrated that tectonic activity controls mobilization of soils and sediments, primarily through processes of uplift and exhumation. Additionally, fault zones are correlated with hydrothermal activity influencing element mobilization and distribution. This is particularly evident through fault-controlled thermal springs along the lake shore and within its catchment, notably in areas like the Kinangop Plateau. Here, intensive agriculture amidst complex faulting has heightened vulnerability to soil erosion. The geological diversity, marked by erodable trachytic tuffs and more resistant basaltic sources, dictates distinct erosion patterns, further compounded by deforestation. This deforestation is visible in Landsat time series data from 1984 to 2023, and particularly severe in the basaltic regions of the Aberdare Range, and trachytic regions of the Kingangop plateau indicating a correlation with increased agricultural activity.

Remote sensing analysis, using multispectral (Aster, Landsat, Sentinel) and topographic  (TanDEM-X, Copernicus DEM) data, has been instrumental in mapping the lake's geological diversity and intricate fault network. The analysis highlights active fault zones, such as those along the NW sector of the Sattima fault and the Gilgil segment of the Kijabe fault. These faults are crucial in shaping the drainage patterns of the Kinangop plateau and influencing the hydrology of the lake.

The preliminary findings of this study place a spotlight on the dominant role of geotectonic processes in the environmental makeup of Lake Elmenteita, while also acknowledging the significant, albeit secondary, impact of human activities. By closely examining these combined forces, the research aims to contribute substantially to the understanding and management of this sensitive ecosystem. This insight is vital not only for Lake Elmenteita but also for other lacustrine systems within rift environments.

How to cite: Kübler, S., Rosca, C., Junginger, A., Muiruri, V., and Dusingizimana, M. W.: Geotectonic Influences on the Lake Elementeita Ecosystem (Central Kenya Rift): Insights from Field and Space-Based Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5407, https://doi.org/10.5194/egusphere-egu24-5407, 2024.

EGU24-6186 | ECS | Posters on site | SSP2.7

Hominin Technology Flourished amid Pliocene Environmental Variance in the Turkana Basin 

Dan V. Palcu, David R. Braun, Eldert Advokaat, Will S. Archer, René Bobe, Susana Carvalho, Frances Forrest, Ashley S. Hammond, Rahab Kinyanjui, Ana Martini, Paul Mason, David B. Patterson, Mark Sier, Priyeshu Srivastava, Kevin Uno, Amelia Villaseñor, Jonathan Wynn, Luigi Jovane, and John W. K. Harris and the Koobi Fora Research & Training Program (KFRTP)

This study explores the emergence of Oldowan technology in the northeastern part of the Koobi Fora Formation, focusing on a poorly understood spatial and temporal context. It highlights the dynamic interplay between hominins, landscapes, and climate during the late Pliocene. The archaeological findings present a comprehensive analysis of stone artifacts from the FwJj52 locality that spans the terminal Pliocene- earliest Pleistocene. The technological patterns at the archeological site FwJj52 align with early Oldowan sites, emphasizing an astute understanding of raw material properties by hominins in the region.

Chrono-stratigraphic investigations reveal that the FwJj52 represents a unique locality, corresponding to the Tulu-Bor and Burgi Members of the Koobi Fora Formation, the latter member containing a stratigraphic interval largely absent in the geologic record of East Turkana due to a widespread unconformity. Multi-proxy geochronology (paleomagnetism, tephrostratigraphy) establishes a robust late Pliocene age estimate for the artifact-bearing horizons from FwJj52. Paleoenvironmental proxies (e.g., phytoliths, microcharcoals, plant biomarkers, pedogenic carbonates, soil geochemistry) indicate the area around FwJj52 experienced significant environmental changes. This includes shifts from humid floodplains to semi-arid plains alternating with paleoriver systems, probably triggered by the retreat of paleo-lake shorelines. 

This Interdisciplinary approach, combining archaeology, chrono-stratigraphy, and paleoenvironmental reconstructions, unveils a complex paleoecological narrative, indicating changes in vegetation, water availability, and climate, coinciding with the emergence of Oldowan stone tool technology in East Turkana. The landscape and climatic shifts we document in the northeastern Turkana Basin, Kenya mirror broader trends in eastern Africa during the late Pliocene, influenced by orbitally- forced climate change, tectonics, and reorganizations of paleogeography. These changes had cascading effects on ecosystems, including the expansion of grasslands and alterations in plant and animal species composition in the late Pliocene.

Paleogeographical and paleoecological shifts in the late Pliocene in eastern Africa likely imposed selective pressures on early hominins that could have influenced their behavior. This study emphasizes the reciprocal relationship between landscapes and tool-making endeavors, suggesting that the environments associated with ancient river systems acted as both witnesses to, and catalysts for, the evolution of stone tool technology.

How to cite: Palcu, D. V., Braun, D. R., Advokaat, E., Archer, W. S., Bobe, R., Carvalho, S., Forrest, F., Hammond, A. S., Kinyanjui, R., Martini, A., Mason, P., Patterson, D. B., Sier, M., Srivastava, P., Uno, K., Villaseñor, A., Wynn, J., Jovane, L., and Harris, J. W. K. and the Koobi Fora Research & Training Program (KFRTP): Hominin Technology Flourished amid Pliocene Environmental Variance in the Turkana Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6186, https://doi.org/10.5194/egusphere-egu24-6186, 2024.

EGU24-10665 | ECS | Posters on site | SSP2.7

Resolving volcanic from anthropogenic metal input to modern lake Elmenteita, Kenya 

Carolina Rosca, Simon Kübler, Veronica Muiruri, and Annett Junginger

Lake Elmenteita located in the central Kenyan Rift System is a shallow (ca. 1 m deep on average), hyper-saline and alkaline playa lake of international bio-ecological importance, as emphasized by its classification as RAMSAR site (2005) and UNESCO world heritage site of “outstanding universal value” (2011). Unusually high rainfall and anthropogenic influence (deforestation, agriculture, sewage loading) are current drivers of changes in water level, composition and quality as well as the dramatic decline in riparian habitats. Identifying individual sources of both, elemental nutrients (P, N, Mg, Si, Zn) and potentially toxic elements (heavy metals, e.g., Cs, Mo, Pb, Sb, Cu) to the lake is imperative for ecosystem monitorization and development of biodiversity conservation strategies.

Here, we present dissolved element concentrations in water samples collected in July 2022 from the 1) central, 2) northern (discharge of rivers Kariandusi and Mereroni), and 3) southern (dominated by tectonically modulated volcanic hot-springs) part of the lake, as well as from 4) river Mereroni and 5) an additional hot-spring in the eastern part of the catchment. Data was acquired in the field and at the laboratories of the Isotope Geochemistry Group, Tübingen University. Results show compositional differences between hot springs and riverine influx (e.g., Cs: 0.03 ng/g Mereroni river vs. 3.3 ng/g S-hot springs), and also between Mereroni river water and northern shore waters (e.g., Sb: 0.063 ng/g Mereroni river vs. 0.92 ng/g N-shore; Cu: 0.925 ng/g Mereroni river vs. 27.3 ng/g N-Shore). Accompanied by observed compositional heterogeneities within the lake itself, our findings suggest that several sources and processes govern the elemental influx and distribution. Using geochemical indices, we will propose elemental dispersion vectors, main sources, and in-lake processes with the aim to unfolding the impact of recent anthropogenic signals from volcano-tectonic elemental origins to the lake.

How to cite: Rosca, C., Kübler, S., Muiruri, V., and Junginger, A.: Resolving volcanic from anthropogenic metal input to modern lake Elmenteita, Kenya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10665, https://doi.org/10.5194/egusphere-egu24-10665, 2024.

EGU24-11537 | ECS | Posters on site | SSP2.7

Indian ocean sea surface temperature control on the 50,000-year strontium isotope Chew Bahir lake record, Eastern Africa 

Charlotte Zachow, Hubert Vonhof, Stephen J. G. Galer, Verena Foerster, Monika Markowska, and Annett Junginger

The role that climate played in human evolution has been controversially discussed among scientists for decades. Inspired by these discussions, the Hominin Sites Paleolakes Drilling Project (HSPDP) conducted five deep drilling campaigns adjacent to key hominin fossil sites in eastern Africa, including the Chew Bahir Basin in southern Ethiopia. Analysis of the Chew Bahir lacustrine sedimentary record revealed that over the past 620,000 years, phases of environmental stability and instability occurred contemporaneously with milestones in human history, including pulsed dispersal events out of Africa coinciding with potential humid periods. Although proxies from Chew Bahir sediments have provided important qualitative information about relative changes in environmental conditions, we still lack quantitative information on water availability and an understanding of the dominant climatic forcings controlling water balance. Here we present the first radiogenic strontium isotope (87Sr/86Sr) record covering the past 50,000 years from four Chew Bahir sediment short cores (CB01, CB03, CB05, CB06) and one long core HSPDP-CHB-1A in a resolution of 100 to 1000 years measured on fish bones, endogenic calcites, and ostracods. We interpret the Sr isotope proxy to reflect water provenance changes, particularly controlled by the varying contribution of water overflowing from a series of lakes further north in Ethiopia. Our new Sr-isotope record shows a remarkable correlation with global sea level variability and does not show a pattern of precession paced cycles. Superimposed on this pattern, we see concurrent excursions in the Sr-isotope record of centennial- to millennial scale events such as Heinrich Event 1 (H1) or the Younger Dryas (YD). As Chew Bahir dominantly receives Indian Ocean moisture, the most likely driver of moisture availability in this part of eastern Africa is the temperature of western Indian Ocean surface water that varies in pace with glacial-interglacial climate change. Also on shorter time scales, reduced Indian Ocean surface temperatures correspond to reduced moisture in the tropical rainbelt resulting in dry conditions around H1 and the YD. Where other paleohydrological proxy data from lake fossils can be comparatively noisy because of the high spatial and seasonal variability in such tropical systems, the relatively conservative hydrochemistry of the Sr isotope signal in lakes like Chew Bahir makes this proxy relatively insensitive to seasonal variability while it faithfully captures decadal to longer time scale signals.

 

 

How to cite: Zachow, C., Vonhof, H., Galer, S. J. G., Foerster, V., Markowska, M., and Junginger, A.: Indian ocean sea surface temperature control on the 50,000-year strontium isotope Chew Bahir lake record, Eastern Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11537, https://doi.org/10.5194/egusphere-egu24-11537, 2024.

EGU24-15595 | ECS | Posters on site | SSP2.7

Exploring past primary production and its linkage with hydroclimate changes in Lake Victoria 

Giulia Wienhues, Andrea Lami, Stefano Bernasconi, Hendrik Vogel, Andrew Cohen, and Martin Grosjean

Lake Victoria, Africa’s largest lake, is located between the eastern and western branches of the East African Rift System, and its immense size but relatively shallow depth distinguish it from other lakes in eastern Africa. The Lake Victoria ecosystem serves as a stark example of the devastating impact human activities and anthropogenic eutrophication can have on freshwater biodiversity. However, despite its global significance as a case study of human-induced biodiversity loss, our understanding of the long-term ecological dynamics of the Lake Victoria ecosystem has remained surprisingly limited. Lake sediments provide valuable insights into the long-term ecological dynamics of Lake Victoria and the complex interplay between hydroclimatic variability, nutrient cycles, and biotic communities, which is crucial for deciphering the trajectories of the lake’s ecosystem evolution under multiple abiotic and biotic stressors in the past and future.

We present in a comprehensive paleolimnological study a detailed reconstruction of the changes in aquatic primary production and phytoplankton communities in Lake Victoria over the past 17 ka, based on novel bio-geochemical analyses of four well-dated sediment cores along a depth transect. Sedimentary pigments and biogenic silica were analyzed to infer aquatic productivity. Changes in sediment composition are supported by X-ray Fluorescence (XRF)-derived element geochemistry, 13C and 15N, and sedimentary phosphorus fraction analyses. In this study, we make use of this exceptionally extensive multivariate dataset to gain a more accurate view on environmental changes in LV from the latest Pleistocene to Holocene times.

Our comprehensive study of Lake Victoria's primary production patterns reveals a profound influence of regional hydroclimate changes on the lake's mixing and nutrient regime, ultimately driving the dynamics of primary producer communities. From its initial wetland phase (16.7 – 14.5 ka), Lake Victoria transitioned to an exorheic, productive system during the wetter Holocene with increased monsoonal activity. This period is marked by two distinct phases of elevated diatom production (11 – 9 ka and 7 – 4 ka). In the late Holocene, drier conditions with reduced water column mixing prevailed, leading to the emergence of a cyanobacteria-dominated phytoplankton community. Overall, these shifts in primary producer dominance underscore the lake's ecosystem sensitivity to hydroclimate variability. Our findings provide invaluable insights into the magnitude and direction of changes in Lake Victoria over time, highlighting the profound impact of natural and anthropogenic factors on the lake's aquatic ecosystem.

How to cite: Wienhues, G., Lami, A., Bernasconi, S., Vogel, H., Cohen, A., and Grosjean, M.: Exploring past primary production and its linkage with hydroclimate changes in Lake Victoria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15595, https://doi.org/10.5194/egusphere-egu24-15595, 2024.

EGU24-837 | ECS | Orals | EMRP3.4

Identifying probable signatures of hydrothermal activity from the Carlsberg ridge sediments using rock magnetic properties 

Sambhabana Lenka, Pratima Kessarkar, Lina Fernandes, and Concy Gomes

The Carlsberg Ridge (CR) is a slow-spreading ridge occurs along divergent plate boundary, with the reports of three active and one extinct hydrothermal vent sites. For the present study eight spade cores (SCs) were collected from the CR, of which three are in the vicinity of Tianxiu hydrothermal field and one on the ridge flank. The hydrothermal sites are known to be associated with metalliferous sediments with Fe being the one of the dominant element. We measured rock magnetic properties of sediments that depend on iron bearing minerals, along with X-ray diffractometry (XRD), and microscopic observations to distinguish metalliferous sediments, that may be associated with the active/extinct hydrothermal activity at the CR. Magnetic susceptibility (χlf) of sediments ranges between 1.3 and 37.1 x10-8 m3kg-1. Low χlf signatures suggesting low metalliferous sediments are observed on flank and two cores from the ridge valley indicating, the absence of hydrothermal activity. Whereas sediments closer to the Tianxiu hydrothermal vent field are associated with high χlf, signifying higher metalliferous sediments and are also having high satuaration isothermal remanent magnetization (SIRM), hard isothermal remanent magnetization (HIRM), and low anhysteretic remanent magnetic susceptibility (χARM)/SIRM, coarse stable single domain (SSD)  and fine SSD & mixture grains characteristics. Two more spade cores ~ 250 km south of the Tianxiu vent field also showed similar signatures indicating new active/relict site/sites in the vicinity. Identifying/locating metalliferous hydrothermal sediment/sites along extensive Mid Ocean Ridge (MOR) is expensive and time-consuming; rock magnetic could be a non-destructive method to shortlist the areas for detailed studies.

How to cite: Lenka, S., Kessarkar, P., Fernandes, L., and Gomes, C.: Identifying probable signatures of hydrothermal activity from the Carlsberg ridge sediments using rock magnetic properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-837, https://doi.org/10.5194/egusphere-egu24-837, 2024.

A correlation between Earth’s magnetic field and climate change has been debated for over forty years, despite significant ~100- and ~41-kyr periods in both the stacked relative paleointensity and inclination records. In this paper, we construct a master relative intensity curve (SPIS-150) over the past ~150 kyr by stacking the data from one new core (PC27) with published intensity curves for the northern South China Sea. Additionally, we calculate the Dole effect from the sea surface temperature (SST) and d18O of planktonic foraminifera based on two cores, PC83 and PC27, and use it as a precipitation proxy. The results of this study show that geomagnetic field intensity lows are related to rich rainfall. During the ~23 kyr period, the relative intensity shows in-phase variations with simulating 0-30°N terrestrial precipitation, which shows that the superimposed effect of insolation and geomagnetic fields influences low-latitude precipitation. The strong summer monsoon predominated by insolation carries rich water vapor, which forms low cloud cover under one cloud-formation physical process where the geomagnetic field modulates galactic cosmic rays (GCRs) and leads to aerosol-related cloud condensation nuclei (CCN) formation. Deeper cloud cover produces strong rainfall in low-latitude regions.

How to cite: Yang, X.: Are there any links between geomagnetic field variations and hydrological cycles in the South China Sea since the Late Pleistocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2855, https://doi.org/10.5194/egusphere-egu24-2855, 2024.

EGU24-3158 | ECS | Posters on site | EMRP3.4

Paleomagnetism and calcite U-Pb geochronology from the Penglaitan GSSP section, South China 

Min Zhang, Huafeng Qin, Chenglong Deng, Shu-zhong Shen, and Yongxin Pan

The Guadalupian-Lopingian boundary (GLB) interval is characterized by the Pangea breakup, dramatic sea-level change, Emeishan Basalt volcanism, and biotic turnover. We conducted magnetostratigraphic, mineralogical, and calcite U-Pb geochronological studies at the Penglaitan Global Stratotype Section and Point section in South China. Rock-magnetic results indicate that magnetite and rare hematite are the dominant remanence carriers. After removing the viscous remanent magnetization, three components were isolated from the limestone at the Penglaitan section. The high-temperature remanence components were isolated from the tuffaceous limestone and yielded a mean direction of Ds/Is = 195.3°/+5.6° (α95s = 5.3°, ks = 22.8, n = 34) after tilt correction. It defined a reversed magnetozone from the top of conodont Jinogondolella granti Zone to the lower part of the Clarkina. dukouensis Zone, straddling the GLB. Additionally, intermediate-temperature components represent the Jurassic and Triassic remagnetization, also supported by the in-situ calcite U-Pb dating (~133-166 Ma and ~213-224 Ma), pyrite-to-magnetite alteration, or magnetite oxidization to maghemite and hematite. The new paleomagnetic results and calcite U-Pb dating provide new insights into Mesozoic multi-remagnetization in the South China Block and refine the GLB positioned in a reversed magnetozone.

How to cite: Zhang, M., Qin, H., Deng, C., Shen, S., and Pan, Y.: Paleomagnetism and calcite U-Pb geochronology from the Penglaitan GSSP section, South China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3158, https://doi.org/10.5194/egusphere-egu24-3158, 2024.

Situated along the Adriatic coast of southern Apulia (Italy), Grotta Romanelli (40.02o N, 18.43o E) is a natural coastal cave considered as a key site for understanding the Middle Pleistocene-Holocene geomorphological, palaeoenvironmental and stratigraphic evolution of the Mediterranean area. Its sedimentary fillings, extremely rich in archaeological and palaeontological findings have been long investigated for their stratigraphical and palaeontological aspects while efforts, mainly based on radiocarbon and pollen analyses, have been focused on better understanding their chronological framework. In this study, we propose a new age model based on the palaeomagnetic record of the uppermost Stratigraphical Unit IUS5 of Grotta Romanelli, also known as Terre Brune. Stepwise alternating field demagnetization provided well-defined directions, which were compared with the reference geomagnetic field curves calculated from the SHA.DIF.14k global geomagnetic field model directly at the cave’s geographic coordinates. A continuous age model was determined taking into consideration the principle of stratigraphic superposition. A selection of reliable, previously published, radiocarbon ages from animal teeth, bones and charcoal was also used for comparison. The proposed age-depth model covers the 14ka-8ka BP period, offering new insights on the chronology of the sedimentation and frequentation of the cave before its complete infilling. This chronological frame enables new considerations on the palaeoenvironmental evolution and climate changes that took place during the transition from the Late Pleistocene to the Holocene, and offers new insights on the dating of the Grotta Romanelli fossil remains, human rests and archaeological artifacts, including lithic tools and rock art.

How to cite: Tema, E., Lanci, L., Pieruccini, P., Mazzini, I., and Sardella, R.: Palaeomagnetic dating of the Grotta Romanelli (Apuglia, Italy) upper sedimentary filling: Insights on the Late Pleistocene-Holocene palaeoenvironment and human settings in the Mediterranean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4536, https://doi.org/10.5194/egusphere-egu24-4536, 2024.

EGU24-5396 | Orals | EMRP3.4

Rock magnetic record of environmental changes over the last 40.000 years in the Westermost Mediterranean: the Alboran Sea sedimentary record 

Victor Villasante Marcos, Silvia Beltrán de Heredia García-Nieto, Francisca Martínez Ruiz, Santiago Casanova Arenillas, and Francisco Javier Rodríguez Tovar

We present here a high-resolution rock magnetic study of deep-sea marine sediments from the Alboran Sea (Westernmost Mediterranean). The analyzed sediment  record, core GP03, 889 cm in length, covers the last 40.000 years from upper Pleistocene glacial times through the Last Glacial Maximum, subsequent deglaciation, Younger Dryas cooling reversal and the whole Holocene up to the current Industrial Period. The sediment core was sampled at high resolution, and 379 samples were measured for their bulk magnetic susceptibility, frequency-dependent susceptibility, hysteresis cycles and Isothermal Remanent Magnetization (IRM) direct and reverse acquisition curves. A subset of 125 samples were subjected to thermomagnetic experiments up to 700º C in order to reveal Curie and thermal transformation temperatures and to support the identification of the precise magnetic mineralogy. The variations in the magnetic mineralogy along the analyzed record, together with previously published geochemical data, have allowed to track the main paleoenvironmental and paleoclimatic changes in the studied region over the last 38 ka, as well as documenting a very strong reductive dissolution horizon affecting magnetic phases in the Younger Dryas sediments, which points to a significant deoxygenation event. A strong correlation of magnetic parameters and stadial-interstadial fluctuations during the last glaciation, especially between 25 and 38 ka, is observed, pointing to variations in riverine vs. aeolian terrigenous input. In modern sediments (approximately the last 200 years), a sharp increase in magnetite abundance in the sediments has been recognized, coinciding with the timespan of the Industrial Period. We conducted magnetic extraction to concentrate the ferromagnetic fraction of these sediments, followed by Scanning Electron Microscopy and EDS analysis, and identified strongly ferromagnetic microspherules with textures typical of rapid crystallization from high temperature melts. These microspherules, rich in magnetite, are indistinguishable from typical fly ash magnetic microspherules of industrial origin, which support they are the magnetic fingerprint of anthropogenic industrial ferromagnetic phases in this marine setting that superimposed on the natural paleoenvironmental changes during the uppermost Pleistocene and Holocene.

How to cite: Villasante Marcos, V., Beltrán de Heredia García-Nieto, S., Martínez Ruiz, F., Casanova Arenillas, S., and Rodríguez Tovar, F. J.: Rock magnetic record of environmental changes over the last 40.000 years in the Westermost Mediterranean: the Alboran Sea sedimentary record, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5396, https://doi.org/10.5194/egusphere-egu24-5396, 2024.

EGU24-5451 | ECS | Posters on site | EMRP3.4

Time-series analysis of rock magnetic data from sediments spanning the last 40.000 years in the Western Mediterranean: strong paleoenvironmental cyclicities during the last glaciation 

Silvia Beltrán de Heredia García-Nieto, Víctor Villasante Marcos, Francisca Martínez Ruiz, Santiago Casanova Arenillas, and Francisco Javier Rodríguez Tovar

Time-series analysis of high-resolution rock magnetic data from deep-sea marine sediments (piston core GP03, Alboran Sea, Westernmost Mediterranean), spanning the last 40.000 years, has been performed to reveal paleoenvironmental cyclicities and climate variability in this region during the uppermost Pleistocene and Holocene. We have applied both the classical Fast Fourier Transform (FFT), after regularizing our data by linear interpolation, and the Lomb-Scargle periodogram, which is well suited to analyze non-regular time series, as is the case. In addition to the usual Lomb-Scargle periodogram, we have also tested a modification of the periodogram that takes into account the experimental errors of the analyzed parameters. Also, in addition to the power spectrum and its peak spectral frequencies/periods, we have computed the Achieved Confidence Level (or false positive rate) of the different spectral peaks by a Monte Carlo evaluation of the permutation test, restricting our further analysis to those spectral peaks with Achieved Confidence Levels greater than 95%. The obtained results through these different approaches show a high degree of coherency, proving the reliability not only of the methods, but also of the modifications introduced and of the obtained results. Our results highlight the presence of characteristic cyclicities with periods in the range of 1600-4500 years during the last glaciation, especially between 25 and 38 ka. The most intense spectral peak has a period around 2 ka, which is consistent with the characteristic periods of Dansgaard-Oeschger (D-O) climate fluctuations. This strong 2 ka signal is clearly arising from the observed match between high magnetic susceptibility and saturation remanent magnetization values with D-O warm phases (interstadials). These relative maxima in magnetic mineral abundance are correlated with high S-ratio values, pointing to an increase in magnetite vs. hematite abundance in the sediments. Conversely, cold D-O phases (stadials) seem to be related to low susceptibility, low saturation remanence and lower S-ratio, indicating a decrease in the contribution of low coercivity phases (like magnetite) and an increase in the relative importance of high coercivity phases like hematite. We suggest this is connected with variations in the relative importance of riverine vs. aeolian terrigenous input. In contrast, Holocene rock magnetic data do not show this 2 ka peak, but instead cyclicities with periods around 2800, 3800 and 5500 years are recognized. To our knowledge, this is the first report of such a remarkable relationship between marine sedimentary rock magnetic data and paleoclimatic cyclicities in the frequency range of the Dansgaard-Oeschger or stadial-interstadial events in the Western Mediterranean over the last glaciation, pointing to the interest of further rock magnetic studies.

How to cite: Beltrán de Heredia García-Nieto, S., Villasante Marcos, V., Martínez Ruiz, F., Casanova Arenillas, S., and Rodríguez Tovar, F. J.: Time-series analysis of rock magnetic data from sediments spanning the last 40.000 years in the Western Mediterranean: strong paleoenvironmental cyclicities during the last glaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5451, https://doi.org/10.5194/egusphere-egu24-5451, 2024.

The hidden link between the geomagnetic field and climate is gradually being noted for its unexpected consistency. However, the unclear linking mechanisms and questions regarding whether geomagnetic reconstructions entirely exclude climatic influences have sparked controversy surrounding this relationship. Here, we analyze a high-resolution geomagnetic paleosecular variation record since 30 ka in the northern South China Sea and find a good correlation between its climate-independent inclination record with the regional temperature and precipitation.

The studied core, SCS-5, was obtained from the northern South China Sea (21.21°N, 118.04°E) at a water depth of 1600 m, twenty AMS 14C ages were used to establish the age framework since ~30 ka, with an overall sedimentation rate exceeding 30cm/kyr. Detailed rock magnetic and environmental magnetic analysis determined that the sedimentary environment of the core is stable and homogeneous. Reliable characteristic remanent magnetization directions are established, with all the maximum angular deviations less than 3. The inclination has fluctuated considerably over the last 30 ka period, but is more moderate during 20-10 ka. Reconstructed paleointensity shows an overall upward trend except for a slight decrease during 15-12 ka, with several significant shallowing of the inclination corresponding to the low values of the field intensity, which may be related to the role of geomagnetic reverse flux patches.

Comparing the local precipitation δ18Osw local record of the core and the paleotemperature record from South China, we observe that as the geomagnetic field strength decreases with shallower inclination, regional precipitation increases significantly, while the land temperature decreases. We hypothesize that the decline in geomagnetic strength may have regulated the regional hydroclimate through the mediation of cosmic rays, aerosols, and cloud cover. The weakening field could have induced increased cloudiness, leading to a parasol effect and greater precipitation. Additionally, the correlation between rainfall and the geomagnetic field is evident throughout the Late Pleistocene-Holocene, whereas the relationship between temperature and the geomagnetic field is more pronounced in the Holocene. It suggests that the forcing mechanism of the geomagnetic field on climate change is complex and nonlinear, which may differ in glacial and interglacial periods due to low-latitude processes or other forcing mechanisms.

How to cite: Wu, S. and Yang, X.: Unveiling the Covert Linkage Between Geomagnetic Dynamics and Climate in the Northern South China Sea Over the Last 30 ka, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5734, https://doi.org/10.5194/egusphere-egu24-5734, 2024.

EGU24-5780 | Posters on site | EMRP3.4

Rock magnetic anomaly caused by the pyritization linking to the gas hydrate dissociation off SW Taiwan 

Yin-Sheng Huang, Chorng-Shern Horng, Chih-Chieh Su, Shu-Kun Hsu, Wen-Bin Doo, and Jing-Yi Lin

      In the study, we present the rock magnetic property from three sediment cores collected by the R/V Marion Dufresne (MD) during the cruise MD214 off SW Taiwan, and two of these cores, MD18-3542 and MS18-3543, have collected shallow hydrate samples. Core site MD18-3542 is on the South Yuan-An East Ridge, where an unconformity covered by fine-silt sediments lies at ~5.5 m below the seafloor, and the core site MD18-3543 is close to the Good-Weather Ridge with a gas-related pockmark and authigenic carbonates near shallow strata. The other core MD18-3548 was obtained at a basin with relatively stable deposition settings to get the background information. Rock magnetic measurements, including magnetic susceptibility (MS) and hysteresis parameters, are used to describe the downcore variations of the magnetic features, while the Day Plot and XRD analysis are applied to classify and identify the dominance of core magnetic components. Both cores MD18-3542 and MD18-3543 show the attractive anomaly with dramatic value-drop in the records of MS and hysteresis parameters, and the feature looks absent in the core MD18-3548. Such signature may link to the pyritization caused by the gas hydrate dissociation. The dissociated methane with hydrogen sulfide trapped under the structures (an unconformity at site MD18-3542 and authigenic carbonates at site MD18-3543) would form an anoxic setting and activate the pyritization at shallow layers. Detrital magnetite would be gradually turned into authigenic iron sulfides, and thus could cause the attractive anomaly in the MS and hysteresis records.

How to cite: Huang, Y.-S., Horng, C.-S., Su, C.-C., Hsu, S.-K., Doo, W.-B., and Lin, J.-Y.: Rock magnetic anomaly caused by the pyritization linking to the gas hydrate dissociation off SW Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5780, https://doi.org/10.5194/egusphere-egu24-5780, 2024.

EGU24-7855 | ECS | Orals | EMRP3.4

A new protocol for fingerprinting cultural ochre sources using mineral magnetism 

Maddison Crombie, Agathe Lise-Pronovost, Marcus Giansiracusa, Colette Boskovic, Amy Roberts, n/a River Murray and Mallee Aboriginal Corporation, and Rachel Popelka-Filcoff

Provenance studies in ochre research are used to characterise the “fingerprint” of different ochre sources, providing the opportunity to trace the cultural movement of ochre in the archaeological past. Ochre pigment composition, and therefore the “fingerprint”, often varies between sites leading to source discrimination, but in many cases the composition can also vary within a site, and therefore presents an analytical challenge to develop methods that can differentiate this “fingerprint”. This work presents a novel protocol for the analysis of iron-based archaeological ochres from known sources within Australia and Kenya using geological mineral magnetism methods to disentangle complex mineral assemblages1. Magnetic properties have been largely unexplored as a tool for ochre provenance. However, the use of measurements such as room temperature – saturation isothermal remnant magnetisation (RT-SIRM), Hysteresis loops and zero field cooled, field cooled (ZFC-FC) allow for the identification of different magnetic minerals in the ochre samples, which can, in turn, be used to fingerprint ochre sources. This approach works towards understanding (1) the variation within and between sites and how this may differ based on source geologies and (2) the larger goal of tracing the movement of ochre from their sources to archaeological contexts and related ochre cultural exchange.

(1) Lagroix, F.; Guyodo, Y. A new tool for separating the magnetic mineralogy of complex mineral assemblages from low temperature magnetic behavior. Frontiers in Earth Science 2017, 5, 61.

How to cite: Crombie, M., Lise-Pronovost, A., Giansiracusa, M., Boskovic, C., Roberts, A., River Murray and Mallee Aboriginal Corporation, N., and Popelka-Filcoff, R.: A new protocol for fingerprinting cultural ochre sources using mineral magnetism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7855, https://doi.org/10.5194/egusphere-egu24-7855, 2024.

EGU24-10469 | ECS | Orals | EMRP3.4

Magnetobiochronology of the Izaga section (South Pyrenean foreland basin) and its chronological implications: searching for a potential candidate for the Bartonian GSSP 

Pablo Sierra-Campos, Pablo Calvín, Gilen Bernaola, Manuel Montes, Aránzazu Luzón, José Ignacio Pérez-Landazábal, Cristina Gómez-Polo, Aitor Payros, Maria Pilar Mata, Eva Bellido, Emilio L. Pueyo, and Juan C. Larrasoaña

Here we introduce a new magnetobiostratigraphic section in the Jaca-Pamplona Basin, the Izaga section, which was studied in order to shed light on the chronology of the Lutetian/Bartonian boundary and the possibility of proposing it to host the Bartonian Global Stratotype Section and Point (GSSP). The Izaga section is located in the northern limb of the eastern termination of the Izaga syncline (South Pyrenean foreland basin) and is composed by a total of 1116 m of marine sediments that include the uppermost 450 m of the Jaca Turbidites and ~660 m of the prodeltaic marls of the Larrés (500 m), Urroz (110 m) and Pamplona (56 m) Formations. The uppermost Jaca Turbidites include the youngest South Pyrenean Eocene Carbonate Megabreccia (SPECM) identified in the basin to date, and the uppermost part of the Larrés Formation hosts ferroan dolomitic nodules whose formation can be linked to early diagenetic methanogenesis. Previously published biostratigraphic data based on planktic foraminifers broadly place the Lutetian/Bartonian boundary within the middle part of the Larrés Formation. A total of 173 magnetostratigraphic sites were sampled throughout the succession with an average 6.5 m spacing. Thermal demagnetization reveals the presence of two stable components: 1) a low temperature component that is identified <250ºC and is interpreted as present-day field overprint; and 2) a high-temperature component, that unblocks from 250-300ºC up to 425ºC and is identified as the ChRM. Paleo- and rock-magnetic data point to the dominant contribution of magnetite to the ChRM, although an additional drop in NRM intensity between 300-350ºC suggests the additional contribution by magnetic iron sulphides. To avoid problems with a likely diagenetic origin of magnetic iron sulphides, we established the polarity sequence of the Izaga section by using only ChRM directions associated to magnetite. The local polarity sequence comprises a normal (N1) magnetozone in the uppermost 286 m of the section and a reverse (R1) one spanning its remaining middle and lower parts. The analysis of calcareous nannofossil aseemblages allow the identification of zones CNE14 and CNE15 in the lower/middle and upper part of the succession, respectively. Overall, these new results enable the correlation of R1 and N1 with chrons C18r and C18n.2n, respectively. We have found no evidence for the presence of chron C19n, the proposed marker for the Lutetian/Bartonian boundary, within R1, which indicates that the whole studied section was deposited during the Bartonian and, therefore, has no bearings on the definition of the Bartonian GSSP. Our results also indicate: 1) that sedimentation rates (of >80 cm/kyr) in the South Pyrenean foreland basin increased towards the west; 2) that the SPECM found within the Jaca Turbidites extend the processes of SPECM formation well into the Bartonian; and 3) that the ferroan dolomitic nodules found in the uppermost part of the Larrés Formation can be considered as the sedimentological expression of the Middle Eocene Climate Optimum (MECO) in the basin.

How to cite: Sierra-Campos, P., Calvín, P., Bernaola, G., Montes, M., Luzón, A., Pérez-Landazábal, J. I., Gómez-Polo, C., Payros, A., Mata, M. P., Bellido, E., Pueyo, E. L., and Larrasoaña, J. C.: Magnetobiochronology of the Izaga section (South Pyrenean foreland basin) and its chronological implications: searching for a potential candidate for the Bartonian GSSP, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10469, https://doi.org/10.5194/egusphere-egu24-10469, 2024.

EGU24-13888 | ECS | Posters on site | EMRP3.4

Rock Magnetic and Mineralogical Analysis of IODP Expeditions 390 and 393 Basement Cores and their Implications for Fluid-Rock Interaction along the Mid-Atlantic Ridge Flank   

Gilbert Hong and Sang-Mook Lee and the The South Atlantic Transect IODP Expedition 390 & 393 Scientists

During the International Ocean Drilling Program (IODP) expeditions 390 and 393 - also referred to as the South Atlantic Transect (SAT), basement cores have been drilled from a total of 6 holes which penetrates around 150 – 300 meters of the uppermost South Atlantic seafloor. The cores mainly consist of basalts of varying age (~7 to 61 Ma) and alteration states. Some intervals of sedimentary breccia were found in older cores as well. Analyzing how these rocks have been altered and characterizing it based on age and depth are crucial to understanding how the oceanic crust along the South Atlantic has evolved throughout spreading and how fluid-rock interaction has influenced the process. Magnetic minerals can be a useful proxy of such alteration as its effects can be observed in both rock magnetism and mineralogy.   

In this study, we observed the composition and microstructure of magnetic minerals within basaltic samples of varying alteration degrees using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). These observations were then compared with shipboard rock magnetic data to determine which property shows correlation with the mineralogical characteristics. Magnetic minerals within the SAT basalt samples are mostly titanomaghemites with Fe content of 20 – 36 at% and Ti content of 5 – 13 at%. Ti content is generally lower in more altered samples, with some highly oxidized samples showing very low percentage (< 3 at%). In addition, heavily altered samples show smaller (< 3 μm) and elongated magnetic mineral grains. Such mineralogical properties show correlation with key rock magnetic properties such as magnetic susceptibility and coercivity of remanence (Bcr). It is also notable that samples with high alteration degree also show reversals in remanence directions caused by strong secondary magnetization that persists after 20 mT demagnetization. This finding implies that production of secondary magnetic minerals may have occurred along with the oxidation of existing grains during the alteration of basalts.

How to cite: Hong, G. and Lee, S.-M. and the The South Atlantic Transect IODP Expedition 390 & 393 Scientists: Rock Magnetic and Mineralogical Analysis of IODP Expeditions 390 and 393 Basement Cores and their Implications for Fluid-Rock Interaction along the Mid-Atlantic Ridge Flank  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13888, https://doi.org/10.5194/egusphere-egu24-13888, 2024.

Loess paleosol sequences carry valuable information on global climate change during the Quaternary. The main geochemical paleoenvironmental proxies rely on the well established sequence of mineral weathering and its products under earth surface conditions. On the other hand, mineral magnetic signal of the loess – paleosol sequences represent easily measurable and sensitive tool for identification and semi-quantification of the degree of secondary alterations of the initial loess substrate. We have analyzed geochemical and magnetic properties of a collection of loess – paleosol sediments from North Bulgaria from 8 profiles, spanning the time interval of the last 800 kyrs. Weathering indices calculated from the bulk geochemical data on major oxides indicate that loess samples are characterized by wide range of Chemical Index of Alteration (CIA) values – from 57.8 to 83.5 with the highest values typically obtained in the oldest deposits, formed during marine oxygen isotope stages (MIS) 16 and 18.  On the other hand, CIA values for paleosols are restricted in the range 73.4 – 82, indicating an intermediate weathering degree. Classic ternary A-CN-K diagram implies dominant role of plagioclase weathering. Magnetic signature of the studied collection shows typical widely observed magnetic enhancement in paleosols as compared to weakly magnetic non weathered loess material. The content of ultra fine grained superparamagnetic magnetite/maghemite give rise to the percent frequency dependent magnetic susceptibility, which shows linear relationship with CIA values, proving the genetic linkage between weathering and pedogenic magnetic fraction. On the other hand, calculated background magnetic susceptibilities χbg for the loess-paleosol couplets included in the study show reverse linear relationship with CIA values for the loess samples. Searching for possible effect of changing dust source areas, we observe decreasing χbg for sites located progressively eastward (longitudes varying from 23oE to 29oE) along with linear increase of χbg with increasing Cr/V ratio, indicative for increasing contribution of mafic component. At the same time, samples from loess horizons with the lowest χbg are characterized by the highest Al2O3/SiO2 values, e.g clay content. Thus, decreasing χbg along W – E transect probably reflects combined effects of dust source change and grain size fining during aeolian dust transportation. The relationships between CIA, χbg and pedogenic magnetic signatures suggest that aeolian dust material was already weathered before its deposition. As a result, the following periods of paleosol formation during interglacial epochs occurred under supply – limited weathering regimes.

This contribution is supported by project No KP-06-H34/2 of the Bulgarian National Science Fund

How to cite: Jordanova, D. and Jordanova, N.: Effects of dust source change, weathering and pedogenesis on loess sediments revealed by combined magnetic and geochemical studies – opportunities and challenges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14612, https://doi.org/10.5194/egusphere-egu24-14612, 2024.

EGU24-15097 | ECS | Posters on site | EMRP3.4

Rock Magnetic Studies of The Early Jurassic Middle Eocene Volcanic and Sedimentary Rocks of the Eastern Pontides 

Bahadırhan Sefa Algur, Sercan Kayın, Abdurrahman Dokuz, Z. Mümtaz Hisarlı, and Turgay İşseven

In this research, we revealed the findings from rock magnetic analyses, including Isothermal Remanent Magnetization (IRM) and High-Temperature Susceptibility (HTS), conducted on various volcanic and sedimentary rocks from the Early Jurassic – Middle Eocene located in the Eastern Pontides. These magnetic studies offer valuable insights into the minerals causing magnetization, as well as the composition and changes in magnetic minerals within these rocks. The experiments were carried out at the Doç.Dr. Yılmaz İspir Paleomagnetism Laboratory, Istanbul University-Cerrahpaşa.

For the Isothermal Remanent Magnetization (IRM) studies, samples were collected from 57 sites in the Eastern Pontides, ensuring representation of each rock type. The analysis revealed that “Hematite”, “Magnetite”, and a combination of “Hematite + Magnetite” are the minerals responsible for magnetization in the selected samples. Moreover, it was discovered that in 41 out of the 57 sites, the samples reached saturation magnetization, indicating that "Magnetite" is the predominant mineral responsible for magnetization. The magnetic susceptibility of the rocks was examined during the heating and cooling stages in these high-temperature susceptibility measurements. High-temperature susceptibility measurements were used to assess whether the minerals responsible for magnetization in the rocks underwent any changes due to temperature, to determine the Curie temperatures, and to understand the domain structure. For this aspect of the study, 23 sites representing various ages and types of rocks were chosen for high-temperature susceptibility studies. It can be said that some rocks are rich in "Ti-Magnetite". It is observed that mineral phase transformation occurs in some rocks as a result of heating phases.

This study was supported by the project of the Scientific Research Projects Commission of Gümüşhane University with Project Number: 21.B0126.01.01.

How to cite: Algur, B. S., Kayın, S., Dokuz, A., Hisarlı, Z. M., and İşseven, T.: Rock Magnetic Studies of The Early Jurassic Middle Eocene Volcanic and Sedimentary Rocks of the Eastern Pontides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15097, https://doi.org/10.5194/egusphere-egu24-15097, 2024.

The East Asian Winter Monsoon (EAWM) is driven by the dry and cold north-westerly winds blowing from central Asia towards the Western Pacific Ocean as atmospheric high-pressure cell develops over Siberia and Mongolia due to low continental temperatures during boreal winter. Today, the EAWM surface winds together with the prevailing mid-latitude upper troposphere westerly jet (WJ) winds transport hundreds of millions of tons of dust every year across East Asia and/or to the North Pacific and further. Various records of past EAWM and/or WJ variability are available but well-resolved records with (sub)orbital resolution to investigate the dynamics of and relationships between EAWM and WJ are rare. The Japan Sea, as the largest marginal sea located in mid-latitude East Asia, is significantly under the influence of the EAWM and WJ. Previous studies suggest that the composition, concentration, and size of magnetic particles in sediments are sensitive to changes in aeolian dust input. Here, we study the magnetic mineralogy and reconstruct high-resolution continuous environmental magnetic records spanning the last 500 kyrs using sediments cored during Integrated Ocean Drilling Program (IODP) Expedition 346 (Asian Monsoon) at Site U1424 in the Japan Sea. Our results suggest that magnetite is the dominant magnetic phase at Site U1424 and there is a significantly increased contribution of high-coercivity magnetic phase, presumably hematite transported through aeolian dust, in samples from glacial periods. Magnetic grain size proxy (kARM/k) of Site U1424 sediments appears to covary with the population of coarse particles (> ~14 μm) that are dominated by aeolian dust, and shows a striking similarity to published EAWM records, especially during the interglacials and glacial inceptions. During the glacial maxima, largely enhanced EAWM indicated by published records are, however, not shown in the Site U1424 kARM/k record. We suggest that Site U1424 kARM/k is a proxy for dust transportation to the Japan Sea modulated by EAWM intensity as well as interactions between EAWM and the WJ. During the interglacials and glacial inceptions when the main axis of WJ frequently reaches Northern China close to the dust source region of the EAWM, interactions between the EAWM and WJ during winter/spring at mid-level troposphere enable long-distance transportation of coarse dust particles (mainly modulated by EAWM) to the Japan Sea. During the glacial maxima, when the WJ main axis no longer frequently reaches the EAWM source regions, reduced interaction between WJ and EAWM prevented long-distance transportation of coarse dust particles. A conceptual model is also presented to summarise the consequences of changes in EAWM and WJ and their interactions over glacial and interglacial cycles at different locations along the Asian dust transportation pathway.

How to cite: Wang, J., Xuan, C., and Wilson, P.: East Asian winter monsoon variability during the last 500 thousand years recorded by environmental magnetism of sediments in the Japan Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19484, https://doi.org/10.5194/egusphere-egu24-19484, 2024.

EGU24-19599 | ECS | Posters on site | EMRP3.4

Preliminary results of paleomagnetism, rock magnetism and AMS in a soot-layered speleothem from Cueva Mayor (Atapuerca, Spain) 

Elisa María Sánchez-Moreno, Eneko Iriarte, Manuel Calvo-Rathert, Eric Font, Maria-Felicidad Bógalo, and Ángel Carrancho

Speleothem are excellent recorders of the Earth’s magnetic field and climate variation. The nature and origin of the magnetic minerals trapped into the calcite laminae are controlled by climate and environmental processes acting on the surface soils and inside the cave.

In this work, we analysed samples from a stalagmite from Cueva Mayor in the archaeological site of Atapuerca (Burgos, Spain). Cueva Mayor site hosts a very important record of Pleistocene human occupation. Finding speleothems that record signs of human activity is unusual. However, in the karst system of the Sierra de Atapuerca, different works on speleothems revealed a significant human fossil record. The stalagmite studied has a small size, the sampled section measures 10 cm from base to top and is not oriented. It shows a calcite laminae alternation with darker micritic and/or ash-rich laminae, composed of aggregates of soot/smoke in the last 2.7 cm to the top. These black soot laminae are interpreted as derived from anthropogenic fires. The remaining part the stalagmite is a sequence of whitish and brownish laminae. A high detrital fraction is inferred from the brown layers. Available U-Th age data on a nearby stalagmite indicate that they grew during the last 14 kyr approximately.

In order to characterize the magnetic properties in a stalagmite of special interest considering its record of human activity, we have carried out experiments on paleomagnetism, rock magnetism, and anisotropy of magnetic susceptibility. We obtained paleomagnetic directions for most samples of calcite laminae with high detrital content and laminae with soot by alternating field demagnetization. Isothermal remanent magnetization acquisition curves of and hysteresis cycles show the presence of low coercivity ferromagnetic minerals in the soot-bearing samples, while the magnetization intensity in the rest of the samples is too weak to show clear results. The thermomagnetic curves reveal magnetite in both brownish-white and soot-containing samples. Other very low Curie temperature magnetic phases also appear in the soot samples. Finally, AMS shows a triaxial magnetic fabric with magnetic foliation pseudo-parallel to the calcite lamellae and horizontal lineation.

Acknowledgments: This work was funded by the Agencia Estatal de Investigación (España) (PID2019-105796GB-100), the postdoctoral program María Zambrano 2021 (España), the Junta de Castilla y León (España) (project BU037P23) and the Fundação para a Ciência e a Tecnologia (Portugal) (PTDC/CTA-GEO/0125/2021).

How to cite: Sánchez-Moreno, E. M., Iriarte, E., Calvo-Rathert, M., Font, E., Bógalo, M.-F., and Carrancho, Á.: Preliminary results of paleomagnetism, rock magnetism and AMS in a soot-layered speleothem from Cueva Mayor (Atapuerca, Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19599, https://doi.org/10.5194/egusphere-egu24-19599, 2024.

EGU24-20050 | ECS | Posters on site | EMRP3.4

Magnetic response of marine sediments to climate variations over the last 40 ka in the western equatorial Pacific. 

Louise Dauchy-Tric, Julie Carlut, Franck Bassinot, Laure Meynadier, and Jean-Pierre Valet

Magnetic properties from marine sediment cores, combined with other proxies, make it possible to study climatic variations. The type, concentration and grain size of magnetic minerals can be used as proxies of precipitation and deep oceanic circulation changes.  

In this study, we focus on core MD01-2385 retrieved on the northwest margin of Papua-New Guinea, in the western equatorial Pacific Ocean. This area is located in the Indo-Pacific Warm Pool (IPWP), which is a major source of heat and moisture to the atmosphere and plays an important role on global climate. The western Indo-Pacific climate is complex, being affected by the El Nino-Southern Oscillation (ENSO) and the Australian-Indonesian monsoon.

 

Core MD01-2385 was dated using 14C. The studied interval covers the last 40 ka with an average sedimentation rate of 30 cm/ka. We took samples every 2 cm (time resolution ~ 70 years). Magnetic granulometry proxies (ARM/SIRM and Karm/K) show a gradual decrease in grain size from the last glacial-interglacial transition (~17 ka) before a stabilization with fine grains from 8 ka. The records show variations associated with Heinrich events and the Younger Dryas. In the ~40 to 13 ka interval, the ARM/SIRM ratio is correlated with the d18O curve from EPICA-EDML ice cores (Antartica), whereas over the last 13 ka the ARM/SIRM ratio appears correlated to d18O curve of the NGRIP ice cores (Greenland).This observation suggests a stronger climatic influence of the Southern Hemisphere than the Northern Hemisphere in this region from 40 to 13 ka, followed since 13 ka by a period in which remote climatic influences originate from northern high latitudes.

Our magnetic results were combined with geochemical analyses carried out by Yu et al. (2023) on the same core (Rb/Sr ratio, chemical index of alteration (CIA), and the smectite/(illite + chlorite) ratio). These data indicate that heinrichs events (HS) are associated, in this region, with lower precipitation (Yu et al., 2023) and also correspond to lower magnetic concentrations, suggesting a dominant physical weathering in northwest Papua-New Guinea.

An interval with coarse magnetic grains and glass shards was dated at ~ 25 ka, suggesting the recording of a volcanic eruption during HS2. It could be the Oruanui supereruption from Taupo volcano, in New Zealand, dated at ~25.5 ka.

How to cite: Dauchy-Tric, L., Carlut, J., Bassinot, F., Meynadier, L., and Valet, J.-P.: Magnetic response of marine sediments to climate variations over the last 40 ka in the western equatorial Pacific., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20050, https://doi.org/10.5194/egusphere-egu24-20050, 2024.

EGU24-20274 | Posters on site | EMRP3.4

Selective transport and deposition of magnetic particles during speleothem growth 

Eric Font, Ana Raquel Brás, Joshua Feinberg, Ramon Egli, Ana Sofia Reboleira, Rui Melo, and Paulo Fonseca

During the last decades, advances in the field of speleothem’s magnetism opened a new door to investigate high-resolution and short-lived features of the Earth’s magnetic field. Due to the rapid precipitation of calcite/aragonite, the lock-in time of the detrital remanent magnetization resulting from the physical alignment of the magnetic minerals parallel to the Earth’s magnetic field is acquired almost instantaneously. The magnetic particles trapped into the speleothem usually originate from the soils capping the cave and are transported into the cave by dripwaters. Authigenic magnetic particles may also precipitate under conditions likely to prevail during speleothem growth. Here we investigate the magnetic mineralogy of a stalagmite from the Gruta da Ceramica of Central Portugal. We also analyzed the host carbonate, the cave sediments and the soils capping the cave. We measured concentration- and grainsize-dependent magnetic proxies, including natural remanent magnetization, anhysteretic remanent magnetization, isothermal remanent magnetization, mass specific magnetic susceptibility, FORC and hysteresis curves.  Results show that magnetic and hematite are the main magnetic carriers in all samples. A gradual enrichment of hematite relative to magnetite is observed following the transportation path from the soils to the cave sediments up to the stalagmite. The higher contribution of hematite relative to magnetite in the speleothem may reflect precipitation of authentic hematite during speleothem growth or the selective transport of finer particles from the soil to the cave.  

 

Acknowledgments: This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (refs. PTDC/CTA-GEO/0125/2021), (PIDDAC) – UIDB/50019/2020, UIDP/50019/2020 and LA/P/0068/2020

How to cite: Font, E., Brás, A. R., Feinberg, J., Egli, R., Reboleira, A. S., Melo, R., and Fonseca, P.: Selective transport and deposition of magnetic particles during speleothem growth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20274, https://doi.org/10.5194/egusphere-egu24-20274, 2024.

EGU24-624 | ECS | Posters on site | CL1.1.2

Hydrodynamic changes in the Gulf of Cadiz during the Early-Middle Pleistocene Transition revealed by benthic foraminifera and radiogenic isotope data 

Giulia Molina, Leopoldo D. Pena, Ester Garcia-Solsona, Eduardo Paredes, Aline Mega, and Antje Voelker

The Early-Middle Pleistocene Transition (EMPT), a global climate event that occurred between 700-1250 thousand years (kyr) ago, was characterized by a drastic change in the deep thermohaline circulation, resulting in more intense and longer-lasting interglacial periods. High-resolution records documenting environmental changes on the ocean seafloor associated with the EMPT in the North Atlantic are still limited. This knowledge is crucial for evaluating and modeling climate variability in the near future. The Gulf of Cadiz (Iberian Margin) is a key region as a gateway between the Mediterranean Sea and the North Atlantic Ocean, being affected at intermediate depths by the Mediterranean Outflow Water (MOW). The MOW plays an important role in modulating the North Atlantic salt budget. Therefore, past climate variability in the Mediterranean region may have affected the MOW intensity and global thermohaline circulation. Thus, the present study aims to understand the environmental parameters influencing the distribution of benthic foraminifera species and their significance in regional oceanographic dynamics. 

Benthic foraminifera inhabit diverse (sub)seafloor environments and respond to factors such as oxygen levels, as well as the quantity and quality of food. Although other factors might influence the assemblage, strong bottom current regimes favor abundances of a group known as the “elevated epifauna”. Previous studies in the Gulf of Cadiz have found that elevated epifauna abundance correlates with MOW intensity in the modern ocean, suggesting it as a potential indicator of MOW intensity in the past.

Here we present results from a high-resolution study of benthic foraminifera assemblage of the period from Marine Isotope Stages (MIS) 26 to 19 at IODP Site U1387 (559 m water depth), drilled into the Faro drift on the southern Portuguese margin. Our study identifies two distinct phases: the first phase (MISs 25 to 22, 959–866 kyr) experienced persistent and intensified MOW flow, as evidenced by an increase in the abundance of elevated epifauna. This phase also exhibits an increase in the abundance such as Globobulimina spp., species that live under oxygen and trophic conditions prevailing at the boundary between dysoxic and anoxic environments, suggesting stronger influence of relatively low oxygen Mediterranean waters. As soon as the MOW intensity declines in the second phase (MIS 21 to MIS 19, 866 – 761 kyr), there is a decrease in the Globobulimina spp. abundance, and an increase in oxygenated-preferred species abundance. We hypothesize that phase I is highly influenced by Mediterranean-sourced waters, whereas phase II improved oxygen conditions indicate potential dominance of Atlantic-sourced waters due to a lesser Mediterranean water contribution. To validate these results, Neodymium isotope analyses (εNd) are being conducted to help distinguishing between the prevailing water masses. Following our hypothesis, we are expecting more positive values during phase I, indicating stronger MOW influence, and more negative values for phase II, suggesting weaker MOW influence and dominantly Atlantic-sourced waters. These findings will further contribute to our understanding of the interplay between climate change and oceanographic dynamics in the Gulf of Cadiz during the EMPT.

How to cite: Molina, G., D. Pena, L., Garcia-Solsona, E., Paredes, E., Mega, A., and Voelker, A.: Hydrodynamic changes in the Gulf of Cadiz during the Early-Middle Pleistocene Transition revealed by benthic foraminifera and radiogenic isotope data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-624, https://doi.org/10.5194/egusphere-egu24-624, 2024.

EGU24-722 | ECS | Posters on site | CL1.1.2

 pH variations during the last and current interglacial stages at the western Iberian margin 

Aline Mega, Eva Calvo, Leopoldo D. Pena, Emília Salgueiro, Andreia Rebotim, Antje Voelker, Joana Cruz, and Fátima Abrantes

The intricate interplay among atmospheric CO2 concentrations, surface ocean pH dynamics, and their profound impact on marine ecosystems is of paramount importance in the context of contemporary climate change. Pre-industrial atmospheric CO2 concentrations oscillated in phase with glacial-interglacial cycles, showcasing low levels during glacial periods and elevated concentrations during interglacial periods. Nevertheless, this natural variability has been significantly disrupted due to the surge in anthropogenic CO2 emissions over recent decades. According to the Intergovernmental Panel on Climate Change, if global atmospheric CO2 concentrations persist in rising at the current rate, it is anticipated that the average ocean pH will decrease by 0.3 pH units in surface waters by the conclusion of this century. This scenario could exacerbate the impacts already observed in marine calcifying organisms, including in marine calcifying organisms such as planktonic foraminifera, affecting their diversity, abundance, and calcification. The main objective of this study is to understand the surface ocean pH evolution in a seasonal upwelling region, during two distinct interglacial periods in Earth's history: the Marine Isotopic Stage 5e (MIS 5e), the last interglacial without anthropogenic influence; and the Holocene, the present interglacial but subjected to anthropogenic influence. In upwelling regions, the upwelling of aged and CO2-rich subsurface waters together with high rates of primary production and respiration, is expected to regionally amplify ocean acidification. This study concentrates on the reconstruction of surface ocean pH using boron isotopes in a surface planktonic foraminifera species, Globogerinoides bulloides. This species is typically found in upwelling regions and was preserved in the marine sediment corer MD03-2699 (39°02.20′N, 10°39.63′W). Our preliminary findings indicate a pH difference between MIS 5e and the Holocene, with lower pH values during the Holocene.  It is argued that during the Holocene, a potential increase in wind intensity may have triggered a strong and persistent upwelling increasing productivity and respiration, consequently leading to lower pH. Additionally, the increase of atmospheric CO2, reconstructed from Antarctic ice cores during this period could also contribute to the ocean pH reduction. These variations in upwelling and/or atmospheric CO2 could be a pivotal factor influencing the observed pH differences, contributing to our comprehension of natural pH variations on the western Iberian margin through advanced pH reconstruction techniques and other multi-proxy environmental data integration for both periods in the region.

How to cite: Mega, A., Calvo, E., D. Pena, L., Salgueiro, E., Rebotim, A., Voelker, A., Cruz, J., and Abrantes, F.:  pH variations during the last and current interglacial stages at the western Iberian margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-722, https://doi.org/10.5194/egusphere-egu24-722, 2024.

The pacing of the global climate system by orbital variations is clearly demonstrated in the timing of e.g. glacial-interglacial cycles. However, due to the complexity and internal nonlinearity of the Earth’s climate system, the mechanisms that translate this forcing into geoarchives and climate changes continue to be debated. A 609-m-thick, continuous lacustrine mudstone and sandstone succession in Chezhen Sag (eastern China) provides an ideal middle Eocene sedimentary record for establishing a high-resolution stratigraphic chronology framework. Based on spectrum analysis and sliding window spectrum analysis of the natural gamma (GR) logging data of well Che 271 (C271) in Chezhen Sag, the periods of 405 kyr and 40.1 kyr were filtered by a Gaussian bandpass filter, and a “floating”astrochronological time scale (ATS) was established. The total number of 405 kyr eccentricity cycles were 13.6 and 40.1 kyr obliquity cycles were 138 which recorded from the upper member 4 (Es4U) to the member 3 (Es3) of the Eocene Shahejie Formation, and the depositional duration was 5.53 Myr. Correlation Coefficient (COCO) analysis and evolutionary Correlation Coefficient (eCoCo) analysis found that the optimal sedimentary rate of different strata. Sedimentary noise simulation revealed the history of paleolake water changes in the Middle Eocene in the Chezhen Sag, according to which four sequences are divided. The study show that the lake level change of Chezhen Sag in the middle Eocene shows prominent 1.2 Myr cycles and an antiphase well-coupled relationship with obliquity modulation. Finally, we propose a model to explain the relationship between orbital cycle and lake level change in continental lake basin. When the obliquity of the earth increases, the middle and high latitudes of the earth will be closer to the sun, the direct sunlight will be higher, and the meridional sunshine will increase, thus accelerating the evaporation process of lake basin water. When the seasonal changes are obvious (Maximum period of 1.2 Myr ultra-long obliquity), this effect is more significant. Our results strengthen knowledge of the connection of Myr-scale lake-level variations to astronomically induced climate change during the middle Eocene under obliquity forcing.

How to cite: Luan, X. and Zhang, J.: Astronomical forcing and sedimentary noise modeling of lake-level changes in the Middle Eocene Chezhen Sag, Bohai Bay Basin, eastern China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2995, https://doi.org/10.5194/egusphere-egu24-2995, 2024.

Water vapor is the essential substance for precipitation and a crucial component of the global hydrological cycle. Quantifying the contributions of terrestrial and oceanic moisture sources is crucial for comprehending regional precipitation and hydroclimate changes. Previous studies have extensively investigated the East Asian summer monsoon and its precipitation changes using geological climate records, but it remains unclear how water vapor from different source regions affects the orbital-scale precipitation change in East Asia. In this study, a long-term transient simulation using a water vapor tracking climate model was conducted for the past 300 kyr to investigate the contributions of terrestrial and oceanic moisture sources to precipitation changes in the northern East Asian monsoon region (NEA, 35-45°N, 105-120°E). The results showed that for the climatologically annual NEA precipitation, the global land source was the primary moisture source, accounting for approximately 57.6% of the total precipitation, followed by Pacific Ocean source contributing 20.9%, while other sources had a minor contribution. The orbital-scale changes of annual NEA precipitation, dominated by the precipitation of the rainy season from May to September, were mainly characterized by a significant 23-kyr cycle and a weak 100-kyr cycle. Analyses of water vapor sources found that the significant 23-kyr cycle in NEA precipitation was caused by the superposition of the synchronous 23-kyr cycles of precipitations from the land and Pacific Ocean sources, while the nonsynchronous 100-kyr cyclic changes of precipitations from the land and Pacific Ocean sources led to the weak 100-kyr cycle of NEA total precipitation. The dominant 23-kyr cycle of NEA precipitation reflects the effect of precession forcing, while the weak 100-kyr cycle implies the impact of the high-latitude ice sheet forcing, which triggers the antiphase change in the moisture contribution rates of the land and Pacific sources in the glacial-interglacial cycle. This study highlights the importance of terrestrial and oceanic moisture sources associated with external forcings in understanding the orbital-scale East Asian monsoon precipitation changes. As a preliminary attempt to track the orbital-scale variations of the terrestrial and oceanic moisture sources of East Asian monsoon precipitation by conducting a water vapor tracking transient simulation, this study provides new insights into the temporal-frequency characteristics and physical mechanisms of orbital-scale East Asian monsoon precipitation variations from the perspective of water vapor sources.

How to cite: Xie, X. and Liu, X.: Deciphering orbital-scale precipitation changes in the northern East Asian monsoon region: insights into the roles of terrestrial and oceanic moisture sources, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2999, https://doi.org/10.5194/egusphere-egu24-2999, 2024.

EGU24-3705 | ECS | Orals | CL1.1.2

Detection of orbital signals in the sedimentary record through stochastic statistical modeling 

Meng Wang, Mingsong Li, Elizabeth A. Hajek, David B. Kemp, Yujing Wu, Hanyu Zhu, and Zhijun Jin

The preservation of orbital signals in sedimentary records, a crucial aspect for the reliability of astronomical time scales, has been insufficiently explored, presenting challenges in interpretation. In this study, we focus on the effect of inconsistent sedimentation rates on the preservation of these orbital signals from a modeling perspective. We delve into how inconsistent sedimentation rates influence the retention of these orbital signals. Employing stochastic statistical models, our research simulates diverse sedimentary environments, we show that 405-kyr eccentricity tuning is the most reliable approach for constructing ATS among different tuning strategies, particularly in environments characterized by high energy conditions and unsteady sedimentation such as fluvial or deltaic settings. This discovery holds substantial importance in refining geological time scales. We introduce an innovative approach to evaluate sedimentation rates within these records. Our study demonstrates the robustness of the cyclostratigraphic method and deepens our understanding of the preservation of sedimentary records, thereby enriching our grasp of Earth's intricate geological past.

How to cite: Wang, M., Li, M., Hajek, E. A., Kemp, D. B., Wu, Y., Zhu, H., and Jin, Z.: Detection of orbital signals in the sedimentary record through stochastic statistical modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3705, https://doi.org/10.5194/egusphere-egu24-3705, 2024.

The Qiangtang Basin, situated on the Tibetan Plateau, is a basin that contains hydrocarbons and has significant potential for hydrocarbon exploration. However, reconstructing sea-level changes and understanding the sedimentary evolution of the Qiangtang Basin has been hindered by the lack of robust high-resolution geochronology. Meanwhile, the Late Triassic stratigraphy of the Qiangtang Basin has also reported the Carnian pluvial episode, the driving mechanism of which is controversial. In this study, the cyclostratigraphy of the Late Triassic Boli La and Bagong Formations in the Qiangtang Basin was analyzed using high-resolution gamma-ray data. Time series analysis shows that there are 405 kyr eccentricity cycles in the gamma-ray data series. The gamma-ray series was tuned to 405 kyr. Then, we establish a floating astronomical timescale with a length of 17.04 Myr. This astronomical time scale establishes an anchored astronomical time scale using the age of the volcanic rocks found in the top of the Bagong Formation in the drill core as an anchor point. Using the anchored astronomical chronology, we reconstructed the Late Triassic sea level change in the Qiangtang Basin using a recently developed sediment noise model. The reconstructed sea level change is generally consistent with the global sea level curve. The antiphase relationship between the filtered long-term obliquity cycles and the sea-level curves reconstructed from the sedimentary noise model suggests that the long-term obliquity cycles may have been the main driver of the Late Triassic greenhouse sea-level change. Meanwhile, the modulation maxima of the long-term obliquity-modulated cycles correlate well with high sea level, episodic negative carbon isotope excursions, global warming, and marine biotic crises, suggesting that obliquity forcing may have played a prominent role during the Carnian Pluvial Episode. Our results suggest that orbital forcing enhanced the hydrological cycle during the Carnian Pluvial Episode. Our study provides a precise, high-resolution time scale for studying the sedimentary evolution of the Qiangtang Basin, as well as a broader perspective on the relationship between the Carnian Pluvial Episode and astronomical forcing.

How to cite: Zhang, Q., Fu, X., and Wang, J.: The cyclostratigraphy of the Late Triassic Qiangtang Basin in Tibet and the orbital forcing for the Carnian Pluvial Episode, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4352, https://doi.org/10.5194/egusphere-egu24-4352, 2024.

EGU24-5931 | ECS | Orals | CL1.1.2 | Highlight

The Precession Cycles in East Asian Stalagmite Records Before the MPT Constrained by Carbonate U-Pb Dating  

Le Kang, Cheng Hai, Jian Wang, Xiaowen Niu, Haiwei Zhang, Jiaoyang Ruan, Youfeng Ning, Jingyao Zhao, and Youwei Li

The U-Pb geochronology of carbonates holds significant application value and potential in the field of geoscience. The Isotope Laboratory at Xi'an Jiaotong University has pioneered the development of Carbonate Laser Ablation and Dilution (LA&ID-MC-ICPMS) U-Pb dating techniques, based on research into Quaternary cave secondary carbonate geochronology. By combining the high spatial resolution and rapid analysis speed of the laser method with the controllable sample volume and high testing accuracy of the dilution method, a comprehensive system for Carbonate U-Pb geochronology testing has been established.

 

Moreover, with advancements in in-situ laser and isotopic dilution techniques for Carbonate U-Pb dating, we conducted tests using the laser method on various carbonate standards, both domestic and international, achieving U-Pb age results consistent with standard values within the error range. This laboratory also reported, for the first time in China, high-precision laser U-Pb dating results for Quaternary cave secondary carbonates, in alignment with ages obtained via dilution methods in foreign laboratories. Furthermore, our laboratory's entire Pb background is currently at a world-class level (~10 pg), and the testing results for cave secondary carbonates are consistent within the error range with dilution methods abroad and the laser method in our laboratory, validating its accuracy.

 

The laboratory has developed robust, high-precision laser and isotopic dilution techniques for Carbonate U-Pb dating, surpassing the limitations of U-Th dating. Through U-Pb dating and oxygen isotope analysis of stalagmite SB20 obtained from Sanbao Cave in Shennongjia, Hubei, our investigation reveals that SB20's growth period spans from 1.25 to 1.50 million years ago, depicting roughly 10 orbital cycles in δ18O. Consequently, we have established East Asia's inaugural δ18O record within the monsoon region, preceding the Mid-Pleistocene Transition (MPT). This novel stalagmite record affirms the predominant influence of low-latitude monsoons, driven by solar radiation forcing, on the East Asian region, showcasing discernible precession cycles. The current emphasis on global climate change research is substantial. By amalgamating prior scientific accomplishments, the interplay between the thermodynamic circulation system governed by ice volume in higher latitudes and the dynamic circulation system regulated by low-latitude monsoons shapes a multifaceted Earth scientific framework. This study furnishes pivotal evidence for the comprehensive exploration of a "high-low latitude" climate circulation theory in the context of climate orbital dynamics.

 

Keywords: Carbonate U-Pb geochronology; MPT; Stalagmite records; precession cycles

How to cite: Kang, L., Hai, C., Wang, J., Niu, X., Zhang, H., Ruan, J., Ning, Y., Zhao, J., and Li, Y.: The Precession Cycles in East Asian Stalagmite Records Before the MPT Constrained by Carbonate U-Pb Dating , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5931, https://doi.org/10.5194/egusphere-egu24-5931, 2024.

EGU24-6679 | ECS | Posters virtual | CL1.1.2 | Highlight

Investigating North Atlantic Deep-Water Ventilation Changes: Preliminary Results from IODP Expedition 397 Hole U1586A 

Lauren Haygood, Natascha Riedinger, David Hodell, Fatima Abrantes, and Carlos Alvarez Zarikian and the Expedition 397 Scientific Party

Although valuable information of North Atlantic circulation paleo-reconstructions by the measurement of oxygen isotopes of benthic and planktonic foraminifera exists, it is still not well-understood how deep-water currents changed over the last ~800,000 years. Moreover, recent studies have shown that some species of microfossils can adapt to low oxygen concentrations, which consequently can impact the reliability of the paleo-reconstructions that are based on these fossils. Marine sediments off the Portuguese Margin have been shown to play a pivotal role in paleoclimate research, and studies have suggested that climate shifts at Mediterranean latitudes are interconnected to changes in deep-water circulation patterns. Changes in bottom-water oxygenation (ventilation) can provide information about changes in deep-water circulation patterns, which can be measured by the enrichment versus depletion of redox-sensitive trace metals. Here we provide the results of a low-resolution geochemical analysis of redox-sensitive trace metals (for example, molybdenum (Mo), vanadium (V), and uranium (U)) to investigate deep-water ventilation changes in the North Atlantic over the last ~800,000 years at Hole U1586A drilled during IODP Expedition 397. Sediment samples underwent a multi-acid digestion technique and were analyzed via an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for redox-sensitive trace metals. Additionally, sequential iron (Fe) extractions were carried out to differentiate between labile versus mineral Fe phases. Preliminary results suggest minor changes in deep-water ventilation that correspond to glacial-interglacial cycles since the mid-Pleistocene. Future work will involve high-resolution geochemical analyses to better understand the interconnection of deep-water circulation and climate change.

How to cite: Haygood, L., Riedinger, N., Hodell, D., Abrantes, F., and Alvarez Zarikian, C. and the Expedition 397 Scientific Party: Investigating North Atlantic Deep-Water Ventilation Changes: Preliminary Results from IODP Expedition 397 Hole U1586A, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6679, https://doi.org/10.5194/egusphere-egu24-6679, 2024.

EGU24-6745 | Posters on site | CL1.1.2

Using lipid biomarker signatures to reconstruct marine primary production in the Iberian Margin over the last millennium 

Lívia Gebara M.S. Cordeiro, Renato S. Carreira, Fernanda Ferreira, Teresa A. Rodrigues, and Fátima F. Abrantes

Despite efforts to understand the response of marine ecosystems to the impact of climate variability in the Iberian Margin [1-6], the effects of warming on phytoplankton community composition and total primary production remain an open question. Here, we present a high-resolution record of sediment-preserved lipids from the Iberian Margin (IM) over the last millennium, with special attention to the modern rise in atmospheric CO2. To address the temporal variation of marine primary production and terrestrial organic matter input, we studied GC-MS/FID-determined lipid compounds from cores PO287-06-2G (off the Douro River in the northern IM), PO287-26-3G (off the Tagus River in the central IM) and POPEI-VC2B (on the Algarve continental shelf in the southern IM). Lipids of typical marine origin (C27, C28, and C30 sterols, phytol, and C37 and C38 alkenones) and of typical terrestrial origin (odd long-chain n-alkanes nC21-nC35 and even long-chain n-alcohols C22OH-C32OH) were evaluated. As proxies for specific phytoplankton groups, we used the signatures of 4α-23,24-trimethyl-5α-cholest-22(E)-en-3β-ol (30d22 sterol) for dinoflagellates, 24-methylcholesta-5,22-dien-3β-ol (28d5,22 sterol) for diatoms and heptatriaconta-15E,22E-diene-2-one (C37:2 alkenone) for coccolithophores. The results showed a significant difference between the northern, central, and southern sites of the Iberian Margin, caused by the different regional environmental factors in each area. Higher concentrations of lipids are observed off Douro River, there is a higher relative contribution of cholesterol off Tagus River, suggesting the importance of zooplanktonic production in the central area, and there is a higher contribution of coccolithophores lipid signatures in the Algarve continental shelf. In terms of temporal variability, there is an alternation between coccolithophores and dinoflagellates lipid signatures over the millennium, with significant diatom sterol signatures at specific ages of the Industrial Era (since 1850 CE) and in the early MCA (900-1100 CE) for all sites. The temporal variability is most likely driven by changes in local and hemispheric ocean circulation and coastal upwelling conditions in the Iberian Margin.

References: [1] Abrantes et al., 2017; [2] Abrantes et al., 2011; [3] Salgueiro et al, 2008; [4] Ribeiro and Amorim 2008; [5] Abrantes 2000; [6] Rodrigues et al., 2009

How to cite: Gebara M.S. Cordeiro, L., S. Carreira, R., Ferreira, F., A. Rodrigues, T., and F. Abrantes, F.: Using lipid biomarker signatures to reconstruct marine primary production in the Iberian Margin over the last millennium, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6745, https://doi.org/10.5194/egusphere-egu24-6745, 2024.

The last glacial cycle provides the opportunity to investigate large changes in the Atlantic Meridional Overturning Circulation (AMOC) beyond the small fluctuations evidenced from modern measurements. Paleotemperature records from Greenland and the North Atlantic, including the Iberian Margin, show an abrupt variability, called Dansgaard–Oeschger (DO) events, which is associated with abrupt changes of the AMOC. These DO events also have Southern Hemisphere counterparts via the thermal bipolar seesaw, a concept describing the meridional heat transport leading to asynchronous temperature changes between both hemispheres. However, temperature records from the North Atlantic, notably the Iberian Margin, show more pronounced DO cooling events during massive releases of icebergs known as Heinrich (H) events, contrary to ice-core–based temperature records from Greenland.

We present high-resolution temperature records over the last 160 kyr using several independent organic proxies (e.g., RI-OH′, TEX86, and UK′37) from three deep-sea sediment cores located in a north-south transect along the Iberian Margin (cores MD99-2331, MD95-2040, and MD95-2042). Over the 160–45 ka BP period, the recent RI-OH′ proxy yields faithful temperature records along the Iberian Margin in comparison with established paleotemperature proxies (e.g., TEX86 and UK′37; Davtian et al., 2021 Paleoceano. Paleoclim. https://doi.org/10.1029/2020PA004077). In the southern Iberian Margin (core MD95-2042), the RI-OH′ and UK′37 proxies faithfully reflect the contrasting DO cooling amplitudes with and without H events over the last glacial cycle (Davtian et al., 2021; Davtian and Bard, 2023 PNAS https://doi.org/10.1073/pnas.2209558120).

We also revisit the thermal bipolar seesaw model using two independent temperature records (RI-OH′ and UK′37) from the southern Iberian Margin (core MD95-2042; Davtian and Bard, 2023). We show that temperature records from the southern Iberian Margin better support the classical thermal bipolar seesaw model than do ice-core–based temperature records from Greenland. We also introduce an extended thermal bipolar seesaw model that considers the contrasting DO cooling amplitudes with and without H events in the southern Iberian Margin, and a Bipolar Seesaw Index to distinguish DO cooling events with and without H events. Our data-model comparison emphasizes the role of the thermal bipolar seesaw in the abrupt temperature variability of both hemispheres with a clear enhancement during DO cooling events with H events, implying a relationship that is more complex than a simple flip-flop between two climate states linked to a tipping point threshold.

How to cite: Davtian, N. and Bard, E.: The value of Iberian Margin paleotemperature records with a novel organic proxy to revisit the bipolar seesaw model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6757, https://doi.org/10.5194/egusphere-egu24-6757, 2024.

EGU24-8238 | ECS | Orals | CL1.1.2 | Highlight

Astronomical pacing and abrupt changes in North Atlantic biogenic sedimentation during the latest Miocene and Early Pliocene: the IODP Site U1562 case study 

Boris Theofanis Karatsolis, Matthias Sinnesael, and Expedition 395/395C scientists

The latest Miocene and Early Pliocene (7-3.6 Ma) include key paleoclimatic and paleoceanographic events such as the Messinian Salinity Crisis (MSC), the late Miocene to Pliocene biogenic bloom (hereafter referred as “biogenic bloom”) and its potential termination, as well as the warm early Pliocene, a commonly used analogue for future global warming. Limited information exists regarding how these events impacted North Atlantic ocean circulation and carbonate sedimentation, mainly due to the lack of continuous, high-resolution records in high latitudes. During the summers of 2021 and 2023, the International Ocean Discovery Program (IODP) Expeditions 395C and 395 drilled a transect of five sites in the North Atlantic (at ~60°N). Preliminary results indicate that IODP Site U1562 has continuous sediment recovery, significant variations in carbonate content, as well as good preservation of calcareous fossils across the latest Miocene to Pliocene, making it a suitable candidate for high-resolution paleoclimatic reconstructions. Here, we estimate carbonate sedimentation and paleoproductivity for this site using high-resolution X-Ray fluorescence (XRF) records, derived from elemental intensities measured in core half-sections. Ratios between biogenically derived and detrital elements reveal the orbitally controlled pacing of carbonate production/deposition, as well as a stepwise, sustained decrease in biogenic sedimentation that occurred during the early Pliocene. The latter shift could have been linked to ocean current reorganizations related to the termination of the MSC or the “biogenic bloom”. Finally, we use a cyclostratigraphic approach to explore the possibility of building an astronomically tuned age model for this site using the XRF records.

How to cite: Karatsolis, B. T., Sinnesael, M., and 395/395C scientists, E.: Astronomical pacing and abrupt changes in North Atlantic biogenic sedimentation during the latest Miocene and Early Pliocene: the IODP Site U1562 case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8238, https://doi.org/10.5194/egusphere-egu24-8238, 2024.

EGU24-9579 | ECS | Orals | CL1.1.2

High-Resolution Sea and Lake Level Reconstructions of the Late Cretaceous: Evidence for a 'Seesaw' Ocean-Land Water Circulation Model 

Kaixuan Ji, Mingsong Li, Fanhao Gong, Haotian Zhang, Shuai Yuan, and Dejun Zhang

The investigation into water circulation mechanisms within greenhouse environments, particularly their link to orbital forcing and consequent impacts on organism-environment coevolution, is garnering increased attention. A key uncertainty is the nature of variations in continental and oceanic water reservoirs on an ice-free Earth and the primary factors driving sea level changes. Traditional approaches like sequence stratigraphy and sedimentology have provided rough and limited insights, hindering a detailed and comprehensive understanding of water circulation in deep time. Therefore, high-resolution inversion of sea and lake level changes is vital for studying global hydrological cycle. Employing advanced sedimentary noise models (DYNOT and ρ1), based on astrochronology and time-series analysis, this research reconstructs detailed water-level variations in key regions: the continental Songliao Basin of Northeast China, the marine Basque-Cantabric Basin in Spain, and the marine Espírito Santo Basin in the western South Atlantic, covering the entire Maastrichtian Stage to the Cretaceous-Paleogene (K-Pg) boundary. These reconstructions, corroborated by sedimentary facies analysis and paleosol studies, reveal 1.2 Myr and 2.4 Myr periodic variations in sea and lake levels, exhibiting a 'seesaw' pattern of opposite trends. This indicates that sea level fluctuations might be influenced by changes in continental water reservoir content, providing new insights into the complex interplay between terrestrial and marine hydrological systems.

How to cite: Ji, K., Li, M., Gong, F., Zhang, H., Yuan, S., and Zhang, D.: High-Resolution Sea and Lake Level Reconstructions of the Late Cretaceous: Evidence for a 'Seesaw' Ocean-Land Water Circulation Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9579, https://doi.org/10.5194/egusphere-egu24-9579, 2024.

EGU24-12155 | ECS | Posters on site | CL1.1.2

Linear and non-linear Time Series Analysis of pan-African Hydroclimate spanning the past 1,200 kyr 

Markus L. Fischer, Norbert Marwan, Verena Foerster, Frank Schaebitz, Eleanor M.L. Scerri, Wolfgang Schwanghart, Stefanie Kaboth-Bahr, and Martin H. Trauth

The time between 1,200 kyr BP and today includes the Mid-Pleistocene Transition, the Mid-Bruhnes Event, and the late Pleistocene. The Early-Mid Pleistocene Transition (~920 kyrs BP) is one of the most dramatic shifts in high-latitude climate and marked by the onset of the strong 100 kyr glacial-interglacial cycles. The Mid-Bruhnes Event marks a significant increase in the amplitude of the glacial-interglacial cycles. It has been identified mostly in marine sediments and Antarctic ice cores, but it is currently discussed whether it was a globally synchronous phenomenon, including the African continent. Marine records suggest a shift towards increased aridity in parts of Africa, and terrestrial records from eastern Africa indicate a generally wet climate, possibly with a transition from stable to unstable, as suggested by the Olorgesailie record. 
At this time, robust Australopithecines went extinct, and only the genus Homo survived as H. ergaster, which ultimately led to the emergence of our own species, H. sapiens. The time vector also includes the second major expansion wave of H. ergaster out of Africa (1.39–0.9 Ma, after the first wave at ~1.9–1.4 Ma), possibly through the Sinai land bridge, but expansions through the Gibraltar strait and via the Bab el- Mandeb strait and into the southern Arabian Peninsula are also subject to lively discussed.
Here, we present the first insights into a comprehensive linear and non-linear analysis of five prominent records, which are (1) the dust record from ODP site 659 from western Africa, (2) the dust record from the Arabian Sea from ODP site 721/722, (3) the river runoff record from MD96-2048, (4) the combined dust and river runoff wetness index from ODP site 967, and (5) the south-western European ICDP record from Lake Ohrid. We use correlation metrics, such as the windowed Spearman correlation coefficient, to test for spatiotemporal synchronicity, asynchronicity, and possible interferences with the hominin fossil record. Furthermore, we use non-linear analysis, such as recurrence plots and recurrence quantification analysis, to test whether prominent climate transitions or spatiotemporal shifts in the fossil record are in temporal alignment with recurrence-based insights.

How to cite: Fischer, M. L., Marwan, N., Foerster, V., Schaebitz, F., Scerri, E. M. L., Schwanghart, W., Kaboth-Bahr, S., and Trauth, M. H.: Linear and non-linear Time Series Analysis of pan-African Hydroclimate spanning the past 1,200 kyr, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12155, https://doi.org/10.5194/egusphere-egu24-12155, 2024.

The climate variations in the past are strongly connected with the cycles of orbital forcing. The orbital forcing redistributes incoming solar energy on the Earth surface, especially over different latitudes. These cycles affect significantly seasons on millennial time scales. The most important influence on climate is provided by the variations of orbit eccentricity, obliquity and precession of Earth axis of rotation. The so-called Milankovitch cycles of eccentricity and obliquity are connected with the processes of glaciations during the last 3 Ma. Actually, all orbital cycles affect paleoclimate, where the effects of eccentricity dominate. The influence of orbital forcing on paleoclimate variations is investigated by two long time series of eccentricity from Laskar’s solution and sea level variations, reconstructed for the last 65 Ma. Common cycles of eccentricity and sea level in 18 different frequency bands are extracted by the Method of Partial Fourier Approximation. The short-periodical cycles, whose periods are below 400 kyr, have relatively good agreement for the last 3 to 7 Ma. The long-term oscillations of sea level and orbit eccentricity with periodicities between 0.8 Myr and 10.8 Myr have excellent agreement in 4 frequency bands, whose duration is 65 Myr. In other 5 frequency bands a good correlation exists for the last 35 – 40 Ma. The estimated amplitudes of sea level cycles are between 2 and 5 m with accuracy of about 0.4 m. The jumps inside of sea level time series are determined by a high-sensitive Method of Jump Detection, based on numerical integration of the time series. The detected jumps determine various data segments, whose duration is below 2.8 Myr and the rate of their linear trends is between 0.3 cm/kyr and 3 cm/kyr. The remarkable result is that all detected jumps occur during the extrema of eccentricity, while the jumps of sea level during glacial cycles in the last 3 Ma occur only in eccentricity minima. These results can help better understanding of climate response to orbital forcing. 

How to cite: Chapanov, Y.: Climate Variations Connected with Earth Orbit Eccentricity , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12267, https://doi.org/10.5194/egusphere-egu24-12267, 2024.

EGU24-13153 | ECS | Posters on site | CL1.1.2 | Highlight

Late Pliocene onset of millennial climate variability during the intensification of Northern Hemisphere Glaciation 

Mengyao Du, Simon Crowhurst, Maryline Mleneck-Vautravers, David Hodell, Fatima Abrantes, Carlos Alvarez Zarikian, and Expedition 397 Scientific Party

The retrieval of sediment cores from Site U1385 during Expedition IODP 397 off the Iberian Margin has yielded a high-fidelity record extending back to the base of Pliocene. This record provides an unprecedented opportunity to investigate the onset of millennial climate variability associated with the intensification of Northern Hemisphere Glaciation (iNHG) during the late Pliocene. Elemental ratios, specifically Ca/Ti and Zr/Sr, measured by core scanning X-ray fluorescence (XRF) have uncovered four distinct millennial climate events in Marine Isotope Stages (MIS) G6, G4, G2 and 104. These single ‘precursor events’ precede the onset of pronounced millennial climate variability marked by multiple events beginning with MIS 100 (2.54 Ma).

The planktic δ18O record of Globigerina bulloides exhibits an increase associated with the peak in Zr/Sr and minimum in Ca/Ti, indicating colder temperatures during the stadial event in MIS G4 (2.69 Ma). A comparison with the δ18O record of mixed benthic foraminifera (Cibicidoides wuellerstorfi and Uvigerina peregrina) indicates that the identified cold stadial in MIS G4 coincided with the end of MIS G4 just before the deglaciation to MIS G3. We therefore suggest it represents a terminal stadial event, which is common during the latest part of glacial stages during the Quaternary. Moreover, the precursor stadial events of MIS G6, G4, G2 and 104 at Site U1385 can be correlated 1:1 to peaks in ice-rafted debris (IRD) in the high-latitude North Atlantic, indicating a connection to iceberg calving and freshwater forcing. Our results indicate that ice sheets had grown large enough during the glacial stages of the latest Pliocene to induce a significant response to freshwater forcing upon deglaciation.

How to cite: Du, M., Crowhurst, S., Mleneck-Vautravers, M., Hodell, D., Abrantes, F., Alvarez Zarikian, C., and 397 Scientific Party, E.: Late Pliocene onset of millennial climate variability during the intensification of Northern Hemisphere Glaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13153, https://doi.org/10.5194/egusphere-egu24-13153, 2024.

EGU24-13215 | Orals | CL1.1.2

Decoding major Climate Mysteries over the last 1.5 million years: Sea Surface Temperature Reconstruction at IODP Site U1385, Iberian Margin. 

Teresa Rodrigues, Joan O. Grimalt, Marta Casado, Yolanda Gonzalez, Simon J. Crowhurst, Fátima Abrantes, and David Hodell

The Iberian Margin provides a remarkably accurate record of millennial-scale climate variability, making it an invaluable site for deciphering historical changes in climate and oceanography. This region’s exceptional sensitivity to high latitude processes, such as meltwater discharges into the Northeast Atlantic, significantly influence ocean dynamics, nutrient supply, and climate change impacts. These processes play a pivotal role in understanding the complex interplay between the ocean, ice, and climate systems. IODP 339 Site U1385, also known as the “Shackleton site”, drilled at a water depth of 2582 mbsl, reaching a total depth of 155.9 m below the seafloor. The oxygen isotope and carbon isotope records confirm that Site U1385 contains a continuous hemipelagic sedimentation from the Holocene to 1.45 million years (MIS 47), providing a reference record of millennial-scale climate variability. Here, we present a high-resolution Sea Surface Temperature (SST) record that unveils the climate variability over the last 1.45 million years.  This record provides a comprehensive interpretation of the millennial climate variability of major climatic disruptions, namely the Mid Brunhes Event and Mid Pleistocene Transition (MPT). SST data reveals a clear change on the orbital-driven forcing on the MPT time interval 1200 to 800 ka, thereby contributing to our understanding the underlying mechanisms on glacial/interglacial and centennial to millennial scales. Furthermore the SST record shows extreme cold events occurred not only after the MPT but also during and after this enigmatic period. The highest temperatures were recorded during Interglacial periods, overall the record and coincident with maximum insolation (precession minimum), suggesting an orbital dependence of the Sea Surface Temperature (SST) over the past 1.45 million years. This SST record significantly contribute to documenting the major climate shifts and their relation to global climate change. This becomes particularly crucial as the IODP Expedition 397 enables the extension of this exceptional sediment record into the Pliocene.

How to cite: Rodrigues, T., O. Grimalt, J., Casado, M., Gonzalez, Y., J. Crowhurst, S., Abrantes, F., and Hodell, D.: Decoding major Climate Mysteries over the last 1.5 million years: Sea Surface Temperature Reconstruction at IODP Site U1385, Iberian Margin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13215, https://doi.org/10.5194/egusphere-egu24-13215, 2024.

EGU24-13997 | ECS | Posters on site | CL1.1.2

Body size variability of North Atlantic benthic fauna driven by bottom-water temperature and oxygen during late Quaternary glacial-interglacial cycles 

Huai-Hsuan May Huang, Curtis Deutsch, Thomas Cronin, Carlos Alvarez Zarikian, Fatima Guedes Abrantes, and David Hodell and the Expedition 397 Scientists

Organism body size is a critical aspect of marine ecosystems and is influenced by climate change on seasonal to geologic time scales. Recent integration of mechanistic models of metabolism, laboratory experiments, and fossil records has opened a new avenue for understanding the roles of thermal sensitivity and hypoxia tolerance in body-size evolution. Here we explore climatic factors driving intraspecific body size variability of benthic ostracods in the central and eastern North Atlantic Ocean. We analyzed over 300 adult shell sizes of multiple ostracod species in the genus Krithe at Sites Chain 84-24-4PC (42°N, 33°W, 3427 m water depth) for the past ~50,000 years and IODP U1588 (37°N, 9°W, 1139 m water depth) for the past ~700,000 years. Chain 84-24-4PC and U1588 are predominantly influenced by North Atlantic Deep Water (NADW) and Mediterranean Outflow Water (MOW) today, respectively. Results show that size reduction corresponded to up to 5 °C deglacial warming during the interval 22-14 ka (MIS 2-1) at the Chain 84-24-4PC core site. Even more striking, size varies 60-70% during major glacial-interglacial transitions (MIS6-5, MIS12-11, and MIS16-15) at Site U1588. The differences observed in the magnitude of size reduction between the two sites are likely influenced by the varying ranges of temperature and, potentially, oxygen variability at their respective water depths. We discuss the potential of using body size changes to reconstruct variability in temperature and oxygen across glacial-interglacial cycles.

How to cite: Huang, H.-H. M., Deutsch, C., Cronin, T., Alvarez Zarikian, C., Guedes Abrantes, F., and Hodell, D. and the Expedition 397 Scientists: Body size variability of North Atlantic benthic fauna driven by bottom-water temperature and oxygen during late Quaternary glacial-interglacial cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13997, https://doi.org/10.5194/egusphere-egu24-13997, 2024.

EGU24-15130 | ECS | Posters on site | CL1.1.2 | Highlight

On the impact of astronomical forcing on ocean anoxia 

Justin Gérard, Jarno Huygh, Loïc Sablon, Michel Crucifix, and Anne-Christine Da Silva

The Devonian is a warmer-than-present geological period spanning from 419 to 359 million years ago (Ma) characterized by 29 identified ocean anoxic/hypoxic events. Despite decades of extensive investigation, no consensus regarding the mechanisms responsible for ocean anoxia has been achieved. Our study contributes to this general research effort, focuses on the astronomical pacing of anoxia throughout the Devonian and is substantiated by growing geologic records suggesting a link between astronomical forcing and anoxic events during this period. To investigate the role of the astronomical forcing we used the Earth system Model of Intermediate Complexity (EMIC) cGENIE, which has proven to be a reliable choice to simulate ocean oxygen spatial patterns and values. In this project, we first tested the impact of continental configuration and ocean biogeochemistry (pCO$_2$, PO$_4$ and pO$_2$) on the equilibrium of the system and the related dissolved ocean oxygen concentration. Then, we produced an in-depth analysis of the astronomical forcing contribution to ocean anoxia for well-chosen continental reconstruction and biogeochemical quantities values. Our results indicate that variations in continental configuration, even small, can exert a strong impact on ocean anoxia, underscoring the influence of paleoreconstructions uncertainties on the biogeochemical tracers of cGENIE. The astronomical forcing reveals to be able to modify the nature of the equilibrium of the system, going from a single-state value solution to an oscillatory behaviour. Our findings also offer insights into potential ocean lockdown mechanisms, providing plausible explanations for the prolonged persistence of certain anoxic events over several hundred thousand years.

How to cite: Gérard, J., Huygh, J., Sablon, L., Crucifix, M., and Da Silva, A.-C.: On the impact of astronomical forcing on ocean anoxia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15130, https://doi.org/10.5194/egusphere-egu24-15130, 2024.

EGU24-15648 | Orals | CL1.1.2

Paleoproductivity and surface water dynamics evolution during the MIS 31 in the Shackleton Site as revealed Coccolithophores 

Jose-Abel Flores, Barbara Balestra, William Clark, Francisco José Jiménez-Espejo, Junichiro Kuroda, Emilia Salgueiro, Joan Grimalt, Timothy Herbert, Maria Angeles Bárcena, Fatima Abrantes, David Hodell, Carlos Alvarez Zarikian, and Expedition 397 Scientific Party

Marine Isotope 31 Stage (MIS-31) records one of the highest high-latitude precession-paced insolation values of the last 5 million years (Laskar et al., 2004). According to this configuration, some studies (e.g. Raymo et al., 2006) predicts a +20 m eustatic sea-level rise for this time interval, reflecting significant retreat of some combination of the West Antarctic Ice Sheet, marginal East Antarctic ice, and the Greenland Ice Sheet, and consequently significant variations in the ocean and climate dynamics at global scale.

In this study we show data of variability in the coccolithophore assemblage from IODP Site 1385 (Shackleton Site, IODP 339 and IODP 397) in the interval ca. 1 Ma (close to the Jaramillo event). These sediments are sensitive recorders of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) oscillations, which makes this site a significant location to test the interhemispheric connection hypotheses.

Peaks in abundance of Gephyrocapsa (<3mm), as well as in other Noelarhaddaceae such as Reticulofenestra asanoi and other morphotypes (equivalent with minimum differences at total coccoliths recorded), were interpreted as a signal of paleoproductivity, revealing strong changes during MIS 31. Alternatively, cold water indicators (Coccolithus pelagicus ) or the census of Helicosphaera carteri l(inked to stratification processes) are considered, showing an alternative pattern along the studied interval. After the refinement of the age-model, these data should be compared with other records in close or remote areas (e.g. Flores and Sierro, 2007, Maiorano et al., 2009), to understand the relevance of this interval, particularly sensible in the Antarctic environment, where a potential relevant melting peak was suggested (Scherer et al., 2009).

Preliminary results (Jiménez Espejo et al., 2013) reveal a distinct turnover during MIS 31 and different evolution of surface and bottom-waters that could be linked with enhanced circulation of NADW during warm periods. This scenario is consistent with stratification pulses interpreted at the top of MIS 32, where cold and stratified water pulses are influenced by and increase in reworked material coming from proximal regions as a result of eustatic sea-level drops.

 

Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M., & Levrard, B. Astrophys. 428, 261-285 (2004).

Raymo, M., Lisiecki, L., Nisancioglu, K. Science. 313, 492-495 (2006).

Maiorano, P., Marino, M., Flores, J.A. Mar. Micropaleontol. 71, 166–175 (2009).

Flores, J.A., Sierro, F.J. Deep-Sea Res. II 54 (21–22), 2432–2442. (2007)

Scherer, R. P., Bohaty, S., Dunbar, R., Esper, O., Flores, J., Gersonde, R., Harwood, D., Roberts, A., and Taviani, M. Geophysical Research Letters. 35, (2009)

Jiménez Espejo et al., 11th INTERNATIONAL CONFERENCE ON PALEOCEANOGRAPHY

1-6 September, 2013. Sitges - Barcelona (2013)

 

How to cite: Flores, J.-A., Balestra, B., Clark, W., Jiménez-Espejo, F. J., Kuroda, J., Salgueiro, E., Grimalt, J., Herbert, T., Bárcena, M. A., Abrantes, F., Hodell, D., Alvarez Zarikian, C., and 397 Scientific Party, E.: Paleoproductivity and surface water dynamics evolution during the MIS 31 in the Shackleton Site as revealed Coccolithophores, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15648, https://doi.org/10.5194/egusphere-egu24-15648, 2024.

The lower Carboniferous is marked by the onset of the Late Paleozoic Ice Age (LPIA), one of the most severe and longest in Earth history, with a duration of nearly 100 million years [1]. The onset of the glaciation is associated with bursts of anoxia of different magnitudes through the Tournaisian and Visean stages (in the lower Carboniferous). These anoxic events are the Lower Alum Shale (LASE [2]) at the base of the middle Tournaisian, The Tournaisian Carbon Isotope Excursion (TICE, also called KOBE [3]) in the middle Tournaisian, and the Visean Carbon Isotope Excursion (VICE [4]). The particularity of these anoxic events is their development during a relatively cold period and their longer durations (5-10 Myr) compared to most other anoxic events. Clues have been accumulated pointing to the possibility that anoxia and glaciation may have been paced by changes in Earth’s orbit parameters ([5], [6], [7], [8]). These changes are the astronomical (Milankovitch) cycles (Eccentricity, Obliquity, and Precession) with specific durations. They impact the incoming solar radiation and seasonal contrasts, hence global climate. Cyclostratigraphy (The identification of astronomical cycles in the geological record) is the tool to establish a chronological framework (ATS) of the lower Carboniferous in order to reach precise estimates for the duration of these anoxic events. This precise timing is essential to get a better understanding of the climate response to astronomical forcing in the early Carboniferous. We also intend to delve into Milankovitch forcing related to ice age evolution and to understand the connection of anoxic events with climate dynamics and orbital forcing. In addition, precession and obliquity cycles are directly related to the Earth-Moon distance (and the length of the day). Through our study, we will provide a duration of precession and obliquity cycles which would allow to provide the Earth-Moon distance and length of the day for this period. Therefore, five geologic sections have been selected in the Namur-Dinant basin in Belgium and one section in Germany. Sections will undergo a high-resolution sampling then multiple analyses will be applied (major and trace elements, total organic carbon (TOC), and stable carbon isotopes(δ13C)). Different cyclostratigraphic techniques will be applied (e.g., MTM, ASM, TimeOpt, COCO, EHA) on specific paleoclimate proxies to build the chronostratigraphic framework. In fine, precession and obliquity cycles are directly related to the Earth-Moon distance (and the paleo-length of the day). Through our study we will provide a duration of precession and obliquity cycles which would allow us to provide the Earth-Moon distance and length of the day for this period, marked by a period of resonance of oceanic dissipation [9]. The study aims to deepen our understanding of the carboniferous ice age, its triggers, and Earth’s intricate climatic mechanisms.

[1]Crowley & Baum 1991. [2] Rakociński et al., 2021. [3] Yao et al., 2015. [4] Liu et al., 2019.  [5] Batenburg et al., 2019. [6] Batenburg et al., 2023. [7] Christine et al., 2020. [8] De Vleeschouwer et al., 2017. [9] Farhat et al., 2022.

How to cite: Boukhalfa, D. and Da Silva, A.-C.: Transition to glacial state through the lower Carboniferous and impact of orbital forcing on sedimentary records and anoxia expansion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16072, https://doi.org/10.5194/egusphere-egu24-16072, 2024.

EGU24-16409 | ECS | Posters on site | CL1.1.2

Paleoceanographic and paleoclimatic analyses throughout the MIS 5 interval: preliminary results from calcareous nannoplankton 

Carmen Argenio, José-Abel Flores, Barbara Balestra, Filomena Ornella Amore, David Hodell, Fatima Abrantes, Carlos Alvarez Zarikian, and Expedition Scientific Party

New insights about the Marine Isotope Stage (MIS) 5 over the North Atlantic area are presented in this study. The MIS 5 interval covers a timeframe from  ̴130 ka to 70 ka and it has been the last major interglacial interval occurred on Earth. In particular, the MIS 5e sub-interval, is a key period to study the possible evolution for human induced climate changes. It also represents an opportunity to interpret the natural climate evolution beyond the anthropic impact being interested by global temperatures assumed to be warmer than the pre-anthropogenic ones (e.g. Kopp et al., 2009). Likewise, the North Atlantic region is interesting for climatic studies being involved in the modulation of the global climate and in particular the Iberian margin is a well-known source of rapidly accumulating sediment offering a high-fidelity record of millennial climate variability.

With this contribution we show preliminary results concerning changes in hydrography and coccolithophores productivity from two sites recovered on the Promontorio dos Principes de Avis, SW Iberian Margin: U1385 (37°34.285’N; 10°7.562’W – 2585 meters below sea level), drilled during the Integrated Ocean Drilling Program Expedition 339, and U1586 (37º37.283’N; 10º42.628’W - 4691 meters below sea level), drilled during the International Ocean Discovery Program Expedition 397.

The phytoplankton group of coccolithophores has proved to be a high-quality environmental proxy since their geographic distribution and abundance is strongly influenced by parameters such as sea-surface temperature, salinity, sunlight and nutrient availability. Accordingly, coccolithophores are here used to describe paleoproductivity fluctuations in surface waters and upwelling strength as well as paleoceanographic changes linked to global climate evolution.

 

References

Kopp, R.E., Simons, F.J., Mitrovica, J.X., Maloof, A.C. & Oppenheimer, M. (2009). Probabilistic assessment of sea level during the last interglacial stage. Nature, 462 (863-867)

How to cite: Argenio, C., Flores, J.-A., Balestra, B., Amore, F. O., Hodell, D., Abrantes, F., Alvarez Zarikian, C., and Scientific Party, E.: Paleoceanographic and paleoclimatic analyses throughout the MIS 5 interval: preliminary results from calcareous nannoplankton, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16409, https://doi.org/10.5194/egusphere-egu24-16409, 2024.

EGU24-16488 | ECS | Orals | CL1.1.2

Understanding Astronomically Forced Carbon Cycle Feedbacks Through the Lens of an Earth System Model  

Pam Vervoort, Sandra Kirtland Turner, Dominik Hulse, Sarah Greene, and Andy Ridgwell

Milankovitch cycles recorded in marine sediments demonstrate the influence of astronomical forcing on Earth’s climate-carbon dynamics. Proxies suggest that during greenhouse climates, isotopically light carbon is released during episodic warm intervals (at eccentricity maxima) and re-sequestered during the following cooling (at eccentricity minima). However, the dominant carbon sources and sinks at play on orbital timescales remain unclear-- particularly when large dynamic ice sheets are absent as during the early Cenozoic. Methods: In an Earth system model (ESM), we apply 4-Myr-long transient astronomical forcing to examine how various climate-sensitive physical and (bio)geochemical processes respond and how this forcing is recorded in key oceanographic variables (temperature, pCO2, δ13C of DIC, and wt% CaCO3). Among others, we assess the impact of marine productivity, CaCO3 compensation, terrestrial weathering, organic matter burial, and phosphorus cycling. Results: Most processes are driven by changes in local conditions -controlled by obliquity and precession, but these high-frequency changes are converted to low-frequency eccentricity cycles expressed in pCO2, benthic δ13C, and wt% CaCO3 as a result of the lowpass filtering effect of the ocean reservoir. While the magnitude of early Cenozoic δ13C variability can be explained by astronomically forced input and burial fluxes of marine organic carbon alone, the dominant frequency and relative phasing of proxies highly depend on the geographic distribution of landmasses that control organic carbon fluxes. For example, only short eccentricity cycles of 100 kyr periodicity (as opposed to long 400 kyr cycles) are simulated in benthic δ13C under favorable paleogeographic configurations. In our model, the pCO2 and temperature response to orbital forcing is minimal, and eccentricity maxima coincide with enhanced preservation of CaCO3. In contrast, early Cenozoic proxies suggest a stronger temperature response and reduced CaCO3 preservation during warm intervals. Implication: Our results support the hypothesis that additional feedbacks that are not yet included here (e.g., terrestrial carbon or methane) were likely important controls during orbital-scale climate variability in greenhouse climates.

How to cite: Vervoort, P., Kirtland Turner, S., Hulse, D., Greene, S., and Ridgwell, A.: Understanding Astronomically Forced Carbon Cycle Feedbacks Through the Lens of an Earth System Model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16488, https://doi.org/10.5194/egusphere-egu24-16488, 2024.

EGU24-16683 | ECS | Orals | CL1.1.2

Intensification of the Indonesian Throughflow in a Coupled GCM During the Last Interglacial 

Sihua Wei, Weipeng Zheng, Jinlong Du, Yongqiang Yu, and Jun Tian

       The Indonesian Throughflow (ITF) plays a pivotal role in large-scale ocean-atmosphere interactions in the tropics, regulating the heat and freshwater budget between the Pacific and Indian Oceans. In the context of global warming in the 21st century, The Indonesian Throughflow are projected to be weaken (medium confidence) by CMIP6 simulations. As an analog of possible future warming, the Last Interglacial (LIG, Marine Isotope Stage 5e or Eemian), with global surface temperature reached about 2 °C above present, serves as an outstanding period to explore the climate response to the external forcing and the mechanisms behind it.

       We use the model outputs from a set of Last Interglacial snapshot simulations carried out by CAS-FGOALS (the Chinese Academy of Sciences Flexible Global Ocean–Atmosphere–Land System model) under the protocol of PMIP for four time periods at 130, 128, 125, and 115 ka. Compared to the piControl simulations (the annual mean ITF flux is 18.46Sv), an annual mean ITF flux increase of about 30.6% - 35.9% was found in the LIG snapshot simulations (24.11 - 25.08Sv). During the LIG, the tropical western Pacific Ocean thermocline was deepened while the tropical eastern Indian Ocean thermocline was relatively shallowed, which was closely tied to the strengthening of the surface easterlies above the tropical western Pacific. Correspondingly, the gradient of the sea surface height between the tropical western Pacific and the tropical eastern Indian Ocean increased, causing pressure contrast between the two basins and probably contribute to the ITF strengthening. We also find that the thermocline gradient between the tropical western Pacific and tropical eastern Pacific was increased, suggesting a La Niña-like state during the LIG. Comparisons of models and proxies further support our conclusions. An examination of the changes in the thermocline water temperature (TWT) record from the eastern Indian Ocean found an enhancement of ITF during MIS 5. Besides, the Maritime Continent was supposed to be more humid by pollen records from west Java and sediment composition from Halmahera Sea.

       Further analysis suggested that the strengthened ITF during the LIG is inconsistent with the weakened one in the 21st century. While the future global warming is primarily driven by increased CO2 levels, the climate changes during the LIG were principally caused by changes in orbital parameters.

How to cite: Wei, S., Zheng, W., Du, J., Yu, Y., and Tian, J.: Intensification of the Indonesian Throughflow in a Coupled GCM During the Last Interglacial, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16683, https://doi.org/10.5194/egusphere-egu24-16683, 2024.

EGU24-17195 | Orals | CL1.1.2 | Highlight

Pre-Cenozoic cyclostratigraphy and paleoclimate responses to astronomical forcing 

David De Vleeschouwer, Lawrence M.E. Percival, Nina M.A. Wichern, and Sietske J. Batenburg

Astronomical insolation forcing is well established as the underlying metronome of Quaternary ice ages and Cenozoic climate changes. Yet its effects on earlier eras (Mesozoic, Palaeozoic and pre-Cambrian) are less understood. In this Review, we explore how cyclostratigraphy can help to distinguish climate modes over the pre-Cenozoic era and aid our understanding of climate responses to astronomical forcing over geological time. The growing uncertainties with geologic age mean that pre-Cenozoic astronomical solutions cannot be used as tuning targets. However, they can be used as metronomes to identify the pacing of distinct climate states. Throughout the pre-Cenozoic, global average temperature differences between climate states were even more extreme (5–32 °C) than in the Cenozoic (14–27 °C), and these, combined with an evolving biosphere and changing plate tectonics, led to distinct Earth-system responses to astronomical forcing. The late Palaeozoic icehouse, for example, is characterized by a pronounced response to eccentricity, caused by nonlinear cryosphere and carbon-cycle behaviour. By contrast, the Devonian warmhouse and the Late Cretaceous hothouse featured recurrent episodes of marine anoxia that may have been paced by astronomical forcing. Formally defining 405,000-year eccentricity cycles as chronostratigraphic units (astrochronozones) throughout the Phanerozoic eon will enable a more comprehensive understanding of how astronomical forcing has shaped Earth’s climate over geologic time.

How to cite: De Vleeschouwer, D., Percival, L. M. E., Wichern, N. M. A., and Batenburg, S. J.: Pre-Cenozoic cyclostratigraphy and paleoclimate responses to astronomical forcing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17195, https://doi.org/10.5194/egusphere-egu24-17195, 2024.

EGU24-17892 | Posters on site | CL1.1.2

Testing the deep water source variations in the Atlantic Iberian margin over the last deglaciation 

Susana M. Lebreiro, Laura Antón, Silvia Nave, Claire Waelbroeck, Edouard Bard, Luke Skinner, Isabel Reguera, Elisabeth Michel, Natalia Bravo, Jordi F. Lopez, Belen Martrat, Teresa Rodrigues, Eva Bellido, and Francisco Sierro

The reservoir age of waters and carbon sequestration increased in the deep Atlantic Ocean during the last glacial period. The glacial northern deep water (GNADW) formation reached shallower depths than during the ensuing interglacial, and the underlying southern-sourced bottom water (GAABW) was filling the basin, generally poorly ventilated. The mechanisms within the deep ocean that facilitate the flip from glacial-to-interglacial modes are as yet to be understood.  

Here we present analysis performed on foraminifera (benthic δ13C, abundance of oxygen-tolerant benthic species and 14C age difference between benthic and planktonic species), together with the n-hexacosan-1-ol index (biomarker of the oxygenation of the deep-sea floor) in three deep cores at the Atlantic Iberian margin (ca. -5,000 m depth; 40°N). The locations selected follow the pathway of the Northeast Atlantic Deep Water (NEADW): MD03-2698 (Tagus Iberian margin), D219 (Rincão da Pomba) and MD13-3473 (Tore inner basin). Additionally, results of polar northern and southern sites (U1308 and TN057-21 respectively) are discussed as a reference for evaluating long-distance connections. 

The hypothesis to be tested is whether the deep waters off Iberia were northern- or southern-sourced during the deglaciation within the Tore seamount, a crater-shaped geological structure, 300 km off the Iberian continental shelf. It includes an inner basin down to -5,500 m, isolated from the oceanic basin by a summit rim at -2,200 m. The external connection with the Atlantic is by two narrow NW and NE gateways down to –4,300 m. This makes the area a singular spot to decipher the NEADW-end member of the Atlantic deep circulation. 

We find benthic (Cibicidoides wuellerstorfi) δ13C values around 0 ‰ in the interior of the Tore before 18 ky, slightly heavier than those known from shallower Iberian sites (ca. -3,500 m). This points to isolation of the Tore basin from the influence of GAABW. This contrasts with the other sites MD03-2698 and D219 which record δ13C around -0.6 ‰, similarly to TN057-21 values. Inside the Tore, benthic foraminifera species grouped according to their oxygen tolerance are oligotrophic during the glacial (oxygen-rich, more ventilated conditions) and mesotrophic over the Holocene (intermediate ventilation).

The carbon residence time measured in MD03-2698 and D219, as estimated from the 14C age difference between benthic and planktonic foraminifera, confirms previous reservoir ages in the deep Iberian margin (MD99-2334K; JC89-SHAK03-6K, JC89-SHAK05-3K). In the inner basin (MD13-3473), the estimation is not valid, probably due to increased bioturbation, lower sedimentation rates and mixing turbiditic flow. 

The hexacosanol index marks the lowest ventilation pattern culminating around 16 ky (MD03-2698, D219), an apparent inflection point from when the ventilation shifts from southern to northern sourced deep waters, the former not registered in the inner Tore (MD13-3473). This occurs in line with a large reduction in the Atlantic meridional overturning circulation (AMOC) and maximum extent of ice sheets. Taken together, interactions between atmospheric, marine, cryosphere and terrestrial climate elements, as recorded by different proxies during the stadial multi-step structure associated within Heinrich event 1 (H1.1) are giving clues to the processes bringing about deglaciation.

How to cite: Lebreiro, S. M., Antón, L., Nave, S., Waelbroeck, C., Bard, E., Skinner, L., Reguera, I., Michel, E., Bravo, N., Lopez, J. F., Martrat, B., Rodrigues, T., Bellido, E., and Sierro, F.: Testing the deep water source variations in the Atlantic Iberian margin over the last deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17892, https://doi.org/10.5194/egusphere-egu24-17892, 2024.

EGU24-18468 | ECS | Orals | CL1.1.2

Changes in the response of the carbon cycle to astronomical forcing during the Silurian Ireviken biogeochemical event 

Michiel Arts, Brad Cramer, Mikael Calner, Christian M. Ø Rasmussen, and Anne-Christine Da silva

The Silurian Ireviken Event is a biogeochemical event characterised by extinctions among several marine groups and a major perturbation to the global carbon cycle. In the Altajme core from Gotland, Sweden, the associated Ireviken Carbon Isotope Excursion (ICIE) reaches peak values of ~6‰. Within the ICIE, the main peak of -6‰ (δ13Ccarb) is superimposed by multiple short-term and small amplitude positive peaks (+1.00 ‰ δ13Ccarb), while the tail of the main peak is superimposed by multiple small amplitude negative peaks (-1.55 ‰ δ13Ccarb). To understand the processes behind these recurrent small amplitude peaks, the high-resolution XRF scanning data of the Altajme core were used to identify astronomical cycles to put astrochronological constraints on the δ13Ccarb curve. Based on the XRF data and its resulting astrochronology, the small amplitude positive and negative δ13Ccarb peaks occur during insolation minima in intervals enriched in carbonate relative to the surrounding lithology. The XRF proxy data indicates that during times when elevated carbonate content coincides with elevated δ13Ccarb values, insolation minima induced an arid environmental state in the basin. This led to decreasing runoff and a strong anti-estuarine circulation, which in turn lowered pelagic productivity and increased photozoan carbonate production, resulting in the deposition of carbonates with elevated δ13Ccarb values. This contrasts to the concomitant insolation maximum, which induced a semi-arid state in the basin, resulting in some runoff, a (sluggish) anti-estuarine circulation in the basin, some pelagic productivity and carbonates being primarily produced by heterozoans, resulting in the deposition of marly carbonates with low δ13Ccarb values. The XRF proxy data indicates that during times when carbonate-rich intervals coincide with more negative δ13Ccarb values, insolation minima induce a semi-arid state in the basin, resulting in some runoff, a (sluggish) estuarine circulation in the basin, some pelagic productivity and carbonates being primarily produced by heterozoans resulting in the deposition of marly carbonates with low δ13Ccarb values. This contrasts with the concomitant insolation maximum which induced humid conditions in the basin, resulting in increased runoff, a (strong) estuarine circulation and high primary productivity, leading to the deposition of marly shales with higher δ13Ccarb values. The shifting baseline climatic conditions during the Ireviken Event are inferred to have changed the response of the depositional environments to astronomical forcing, in changing (carbonate) productivity and circulation, which in terms modulated the carbon cycle, resulting in an imprint of astronomical cycles in the ICIE.

How to cite: Arts, M., Cramer, B., Calner, M., Rasmussen, C. M. Ø., and Da silva, A.-C.: Changes in the response of the carbon cycle to astronomical forcing during the Silurian Ireviken biogeochemical event, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18468, https://doi.org/10.5194/egusphere-egu24-18468, 2024.

EGU24-18823 | Posters on site | CL1.1.2

Exploring the Plio/Pleistocene stratigraphy of the Upper Rhine Graben from a core taken at a Riedstadt/Hesse 

Christian Zeeden, Mohammad Paknia, Stephanie Scheidt, Stefanie Kaboth-Bahr, Mathias Vinnepand, and Christian Hoselmann

The past subsidence episodes of the northern Upper Rhine Graben allowed the accumulation of thick sedimentary sequences that can function as excellent data source for paleoclimate reconstructions. A 323 m long sediment core drilled in 2020-2021 near Riedstadt-Erfelden (~14 km WSW of Darmstadt) is therefore likely a high-resolution geoarchive documenting climate dynamics during the Plio-Pleistocene epochs. So far, the chronostratigraphic framework is based only on lithostratigraphic assignments. This study presents inclination values and magnetic susceptibility obtained from whole-core measurements and discusses initial stratigraphic ideas based on the resulting preliminary magnetic polarity stratigraphy and cyclostratigraphic assessments of the ‘Riedstadt-Erfelden’ core.

Here, we highlight on the quasi-cyclic components of the core, and provide an interpretation in the light of paleomagnetic dating.

How to cite: Zeeden, C., Paknia, M., Scheidt, S., Kaboth-Bahr, S., Vinnepand, M., and Hoselmann, C.: Exploring the Plio/Pleistocene stratigraphy of the Upper Rhine Graben from a core taken at a Riedstadt/Hesse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18823, https://doi.org/10.5194/egusphere-egu24-18823, 2024.

EGU24-19442 | Orals | CL1.1.2

Strength variability of the Mediterranean Outflow Water during late Quaternary: Preliminary results from IODP Site U1588 

Jiawang Wu, Xinyang Chen, Zongxian He, Qin Deng, Lifeng Zhong, Xiaolei Pang, David Hodell, Fatima Abrantes, and Carlos Alvarez Zarikian and the Expedition 397 Scientific Party

The Mediterranean Sea is thought to play a role in changing past ocean circulation and North Atlantic climate, through the outflow of warm, saline intermediate waters (Mediterranean Outflow Water; MOW) into the North Atlantic. Previous studies mostly focused on the Gulf of Cádiz, immediately after the MOW existing the Mediterranean, but how the MOW varied along the northward transport is still unclear. Fine grain-size parameters have been widely employed to infer paleo-flow speeds of near-bottom currents in the deep sea, in particular the terrigenous non-cohesive “sortable silt” (denoted as SS) controlled by selective deposition. Here we present terrigenous sediment grain size results on IODP Site U1588 (37°57.61′N, 9°30.99′W, 1339 m water depth), which was retrieved from the Iberian Margin during the IODP Expedition 397. Our aim is to reconstruct strength variations in the lower branch of the MOW over the past ~250,000 years. After removing organic matter (leached with 10% H2O2 at 85 ℃) and marine carbonates (leached with 0.5 M HCl), the terrigenous detrital component of about 100 samples were measured on a Malvern Mastersizer 3000 instrument. Our grain-size results show a bimodal distribution, with a small peak near 1 μm and the main mode between 5–8 μm. The correlation between the percentage and mean of the sortable silt fraction (10–63 μm) is significant (R2=0.43, P<0.01), permitting the use of SS-mean as a reliable indicator of the deep-sea current strength. The calculated SS-mean is from ~14.2 to 18.2 μm, corresponding to the flow speed of ~3.3 to 10.2 cm/s. Based on the shipboard age model, our results show a persistent low-latitude forcing of MOW flow speed over the past 250,000 years, with strong precessional and glacial cycles.

How to cite: Wu, J., Chen, X., He, Z., Deng, Q., Zhong, L., Pang, X., Hodell, D., Abrantes, F., and Zarikian, C. A. and the Expedition 397 Scientific Party: Strength variability of the Mediterranean Outflow Water during late Quaternary: Preliminary results from IODP Site U1588, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19442, https://doi.org/10.5194/egusphere-egu24-19442, 2024.

EGU24-19840 | Orals | CL1.1.2 | Highlight

Precessional Climate Cyclicity on the Iberian margin: Miocene-recent 

Timothy Herbert, Fatima Abrantes, Hannah Brooks, Jose-Abel Flores, David Hodell, Jerry McManus, Bryce Mitsunaga, Celeste Palone, Xioalei Pang, Jiawang Wu, Jimin Yu, and Carlos Zarikian and the Expeditiion 397 Scientific Party

IODP Expedition 397 recovered a continuous record of precessionally-paced lithological cycles to the base of the recovered section (~9.55 Ma) at Site U1587.  On board ship, three intervals were selected for multi-disciplinary dissection of the cycles in time windows comprising three precessional cycles each ((early Pleistocene 2.284-2.345 Ma, late Pliocene 3.427-3.496 Ma, and late Miocene 5.638-5.5707 Ma).  These three intervals are grounded in continuous XRF scanning that allows for a reliable astrochronology based largely on precessional variability. Carbonate cyclicity follows northern hemisphere precession throughout high carbonate content associated with high northern hemisphere summer insolation.  The cycles cannot be explained solely by changes in carbonate production or preservation, as the clay-rich phases of the cycles are often expanded relative to the carbonate-rich phases.  Sea surface temperature (SST) recorded by alkenone biomarkers shows fluctuations in tandem with the carbonate cycles.  For the Pliocene and Pleistocene, higher carbonate correlates to warmer SST and interglacial conditions as inferred from stable isotope measurements.  The pattern flips in the Messinian test interval, with high carbonate associated with colder and more glacial climate.  Clay mineralogy shows cyclic fluctuations associated with changes in riverine and eolian inputs.  High illite (high dust?) corresponds to high carbonate content in the Miocene and Pleistocene test intervals, while the opposite is observed for the Pliocene.   An abrupt change in cycle spacing near the terminal Messinian likely records a tectonic event that perhaps influenced transport and deposition of the detrital components.

How to cite: Herbert, T., Abrantes, F., Brooks, H., Flores, J.-A., Hodell, D., McManus, J., Mitsunaga, B., Palone, C., Pang, X., Wu, J., Yu, J., and Zarikian, C. and the Expeditiion 397 Scientific Party: Precessional Climate Cyclicity on the Iberian margin: Miocene-recent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19840, https://doi.org/10.5194/egusphere-egu24-19840, 2024.

EGU24-21881 | Orals | CL1.1.2

Combined high-and low-latitude forcing of orbital East Asian hydroclimate 

Hongbin Zhang, Michael L. Griffiths, Hai Cheng, Gaowen Dai, Jiaoyang Ruan, Yunping Sun, Ling Lu, Wei Guo, Junhua Huang, and Shucheng Xie

Speleothem oxygen isotope records from China have provided the most detailed insights into the past Asian summer monsoon variability of any paleoclimate archive (“proxy”) to date in the past 640 ka, showing the dominance of the orbital precession rhythm. However, fundamental disagreement exists on what the oxygen isotope records represent in terms of the hydroclimate changes, in particular on the orbital scale. Based on the oxygen isotope records and other hydroclimate proxies from 15 speleothems at Haozhu Cave in central-eastern China, as well as the model simulations for the periods of Marine Isotope Stages 6 and 11, we show the orbital-scale ‘dipole’ hydroclimate in monsoonal eastern China, with wetter (drier) conditions in the central but drier (wet) conditions in the north when summer insolation was low (high) and East Asian summer monsoon was weak (strong). Of significance is the finding that the hydroclimate contrast in East China was greatly enhanced during glacial-interglacial transitions, with the wettest hydroclimate in the north but widespread drought in the central, when the heat content of both the global ocean and the Indo-Pacific Warm Pool upper ocean reached the maximum. We propose that the orbital-scale westerly jet transition affects the East Asian summer rainband position and thus the orbital hydroclimate pattern in eastern China, and the low latitude tropical Indo-Pacific ocean moisture transport amplifies the hydroclimate contrast during glacial-interglacial transitions

How to cite: Zhang, H., Griffiths, M. L., Cheng, H., Dai, G., Ruan, J., Sun, Y., Lu, L., Guo, W., Huang, J., and Xie, S.: Combined high-and low-latitude forcing of orbital East Asian hydroclimate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21881, https://doi.org/10.5194/egusphere-egu24-21881, 2024.

EGU24-521 | ECS | Posters on site | CL1.2.10

Geochemical signals from biogenic varves reflect hydroclimate and lake oxygen conditions in central Finland 

Mohib Billah, Saija Saarni, Rik Tjallingii, Birgit Schröder, Sylvia Pinkerneil, Timo Saarinen, and Achim Brauer

Annually laminated (varved) lacustrine sediments are sensitive recorders of climatic-induced variability in the catchment. In a Boreal setting, climatic information is usually extracted from clastic-biogenic varves, although the potential of biogenic varves remains almost unexplored. The organic-rich sublayers of Boreal biogenic varves usually include thicker growing season lamina enriched with amorphous organic matter and thinner winter lamina reinforced with fine-grained organic matter settled under ice cover during the winter season. This study explores the properties and controls of varve formation in Lake Kallio-Kourujärvi and their implications in understanding past hydroclimate and lake oxygen conditions using micro-XRF combined with stable carbon and nitrogen isotope analysis. Lake Kallio-Kourujärvi is located in central Finland and has organic-rich varves. The thickness of these varves is controlled by the accumulation of biogenic matter that originates from terrestrial sources and autochthonous production. The varve counting provides an age estimate for the 1,8 m long varved sediment sequence of approximately 3700 years before the present (BP). The results from major elemental data reveal that changes in iron and sulfur are consistent with the varve thickness data previously shown to be sensitive for precipitation, as well as decadal changes in North Atlantic Oscillations (NAO) forced winter precipitation. Precipitation likely increases the transport of soluble Iron(II) from the catchment, which settles into sediment as particulate Iron(III) after being oxidised in the water column. Strong changes of redox conditions by the elements iron, manganese, and sulphur are indicated between around 1600 BP and 3700 BP. The variation of redox-sensitive elements suggests that changes in hydroclimatic conditions and past water mixing conditions can be reconstructed from the biogenic varve records.

How to cite: Billah, M., Saarni, S., Tjallingii, R., Schröder, B., Pinkerneil, S., Saarinen, T., and Brauer, A.: Geochemical signals from biogenic varves reflect hydroclimate and lake oxygen conditions in central Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-521, https://doi.org/10.5194/egusphere-egu24-521, 2024.

EGU24-3414 | Orals | CL1.2.10

A Punctuated Equilibrium Analysis of the Climate Evolution of Cenozoic exhibits a Hierarchy of Abrupt Transitions 

Denis-Didier Rousseau, Witold Bagniewski, and Valerio Lucarini

The Earth’s climate has experienced numerous critical transitions during its history, which have often been accompanied by massive and rapid changes in the biosphere. Such transitions are evidenced in various proxy records covering different timescales. The goal is then to identify, date, characterize, and rank past critical transitions in terms of importance, thus possibly yielding a more thorough perspective on climatic history. To illustrate such an approach, which is inspired by the punctuated equilibrium perspective on the theory of evolution, we have analyzed 2 key high-resolution datasets: the CENOGRID marine compilation (past 66 Myr), and North Atlantic U1308 record (past 3.3 Myr). By combining recurrence analysis of the individual time series with a multivariate representation of the system based on the theory of the quasi-potential, we identify the key abrupt transitions associated with major regime changes that separate various clusters of climate variability. This allows interpreting the time-evolution of the system as a trajectory taking place in a dynamical landscape, whose multiscale features describe a hierarchy of metastable states and associated tipping points.

The analysis reveals that two major events out of the ten dominated the evolution of the Earth's climate system over the last 66 million years. The first event was the Chicxulub meteor impact in Mexico, which killed off the large dinosaurs approximately 65,5 million years ago. This catastrophe marked the beginning of a very warm period with high levels of CO2. For the following 30 million years this regime dictated which climatic changes were possible and kept it within the regime of hot and warm climates.

The second crucial event was the tipping point associated with the glaciation of the Southern hemisphere 34 million years ago when the Antarctic continent was isolated at the South Pole due to plate tectonics. The forming of the large ice sheet led to the glaciation of the North as well and marked the beginning of a considerably colder type of climate on Earth, again dictating the scope of future climate changes.

The analysis additionally suggests that our current global climate system still belongs to the latter climate regime and still depends on the existence of the gigantic ice bodies built within the Coolhouse/Icehouse era. In the event that the ice sheets should not withstand anthropogenic global warming, the deglaciation will therefore represent a landmark tipping point similar to the two that have dominated Earth's history leading to a new unknown climate landscape.

Rousseau, DD., Bagniewski, W. & Lucarini, V. A punctuated equilibrium analysis of the climate evolution of cenozoic exhibits a hierarchy of abrupt transitions. Sci Rep 13, 11290 (2023). doi: 10.1038/s41598-023-38454-6

How to cite: Rousseau, D.-D., Bagniewski, W., and Lucarini, V.: A Punctuated Equilibrium Analysis of the Climate Evolution of Cenozoic exhibits a Hierarchy of Abrupt Transitions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3414, https://doi.org/10.5194/egusphere-egu24-3414, 2024.

The study of centennial-scale events remains underdeveloped, with little knowledge of events timing, their inter-regional phasing, and the role played by the Atlantic Meridional Overturning Circulation (AMOC) during these events (1, 2). Here we present four high-precision speleothem δ18O records from Asian summer monsoon (ASM) and South American summer monsoon (SASM) domains, spanning a centennial-scale 55 ka event. These speleothem records are comparable to those previously published from Europe, indicates that the 55 ka event occurred simultaneously in the European and ASM domains. The synchronous timing during the centennial-sale events is consistent with what has previously been observed during millennial events (1). It is therefore likely that abrupt climate change teleconnections between North Atlantic and ASM hydroclimates would have pervasively persisted during the last glacial period. Additionally, the speleothem records were compared with the bipolar ice-core and marine sediment records of INTIMATE. The “monsoon seesaw” pattern between the ASM and SASM records over 55 ka event is consistent with a northward shift of the Intertropical Convergence Zone (ITCZ). Our study suggests that the 55 ka event was caused by AMOC reinvigoration.

 

Ref.

(1) Corrick, E C. et al. Synchronous timing of abrupt climate changes during the last glacial period. Science 369,963-969 (2020).

(2) Lynch-Stieglitz, J. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change. Annual Review of Marine Science 9, 83-104 (2017).

 

How to cite: Dong, X.: Timing and climate dynamics of centennial-scale abrupt climate change during early Marine Isotope Stage 3 inferred from the INTIMATE network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4983, https://doi.org/10.5194/egusphere-egu24-4983, 2024.

EGU24-5356 | ECS | Orals | CL1.2.10 | Highlight

Climatic and environmental impacts of the ~74 ka Youngest Toba Tuff volcanic eruption in Indonesia as evidenced from the sediment record of Lake Chala (Tanzania/Kenya) 

Jinheum Park, Christian Wolff, Dirk Verschuren, Melanie J. Leng, Jack H. Lacey, Maarten Van Daele, Christine S. Lane, Catherine Martin-Jones, Céline M. Vidal, Clive Oppenheimer, and Philip A. Barker

The ~74 ka Youngest Toba Tuff (YTT) eruption of Mount Toba in Indonesia is considered to be the largest volcanic eruption during the last 2.6 Ma. Its impact on global climate regimes and ecosystems, especially in tropical regions, is important due to possible consequences for the evolution and dispersal of early modern humans. In this study, we utilise the high-quality lake-sediment record from Lake Chala (Tanzania/Kenya), recovered by the ICDP DeepCHALLA project, to reconstruct the climatic and environmental impacts of the YTT in eastern equatorial Africa. Previous work identified a cryptotephra layer that was geochemically correlated to the YTT. In this study, focusing on the section of finely laminated sediments lying directly below and above the YTT layer, we compile high-resolution data from thin-section optical microscopy, geochemistry and fossil diatom assemblages in order to trace changes in climatic, local lake-system and wider environmental conditions immediately before and after the YTT event. Most proxy analyses were conducted at annual or higher temporal resolution, which is rare for late-Pleistocene palaeo-records. Our results reveal changes in regional hydroclimate following the YTT eruption, possibly coupled with volcanically induced changes in the El Niño–Southern Oscillation dynamics. Further, the precise location of the YTT layer within varved Lake Chala sediments provides new information on the season of the YTT eruption.

How to cite: Park, J., Wolff, C., Verschuren, D., Leng, M. J., Lacey, J. H., Van Daele, M., Lane, C. S., Martin-Jones, C., Vidal, C. M., Oppenheimer, C., and Barker, P. A.: Climatic and environmental impacts of the ~74 ka Youngest Toba Tuff volcanic eruption in Indonesia as evidenced from the sediment record of Lake Chala (Tanzania/Kenya), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5356, https://doi.org/10.5194/egusphere-egu24-5356, 2024.

EGU24-5613 | ECS | Orals | CL1.2.10

Abrupt onset and termination of the Holocene Humid Period across Asia 

Yonaton Goldsmith, Hai Xu, Narantsetseg Ts, Adi Torfstein1, Mordechai Stein, and Yehouda Enzel

The termination of the Holocene Humid Period between 6-5 kyrs ago is relatively well-documented in Africa. By contrast, outside of Africa the spatial extent of this termination, the rate of change (gradual vs. abrupt) and the timing of this termination remain obscure. To assess whether such a termination occurred in Asia and to characterize the spatial and temporal evolution of this termination, we constructed lake-level histories of five closed-basin lakes, four of which are located along a north-south transect in East Asia (Lakes Khukh, Dali, Daihai and Chenghai from 50N to 25N) and the fifth is the Dead Sea in western Asia (33N). A closed-basin lake has no outlet, and therefore its size varies as a function of precipitation and evaporation. Distinct shoreline deposits form at the lake’s margin and are physical relict imprints of past lake-levels. These lake-level histories provide a powerful, first order, quantitative record of past water availability. For each lake, we developed a detailed lake-area history based on numerous radiocarbon, Optical Stimulated Luminescence and U/Th disequilibrium ages.

All five lakes show that substantial changes in lake-level (up to 60 m) and surface area (of up to six times that of modern area) occurred throughout the Holocene. The results indicate that in East Asia wet conditions were initiated during the Bølling-Allerød and weakened and dried during the Younger-Dryas. The onset of the Holocene Humid Period, at 11.5 kyrs, was rapid, with the lakes rising to their high-stands within a half millennium. In western Asia, the lake-level rise most likely occurred later, at ~10 kyrs. During the Holocene Humid Period the lakes were significantly larger than the modern lakes. The wet conditions in northeast Asia and western Asia prevailed until 6 kyrs, when the lakes dried out abruptly, within a few decades, and have not been restored to their pre-6 kyrs sizes since. In South China, the rapid drying occurred earlier, at ca. 8 kyrs. All five lakes show a substantial dry period between 6 – 4 kyrs. In northeast Asia the dry conditions prevail until today. However, in both South China and western Asia the lakes rose at 3 kyrs and remained mostly high until recently.

Our findings from the five Asian closed-basin lakes show that during the early Holocene, Asia was scattered with lakes that were much larger than today and that an abrupt onset and abrupt termination of the Holocene humid period occurred across Asia. We use the lake-level histories to quantify regional water availability, to discuss the migration of rain-belts in Asia, speleothem oxygen isotopes and pollen records, and the ability of transient climate models to capture the magnitude, extent and rapidness of these wet conditions and hydroclimatic transitions.

How to cite: Goldsmith, Y., Xu, H., Ts, N., Torfstein1, A., Stein, M., and Enzel, Y.: Abrupt onset and termination of the Holocene Humid Period across Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5613, https://doi.org/10.5194/egusphere-egu24-5613, 2024.

EGU24-7498 | ECS | Orals | CL1.2.10

Towards the construction of regional marine radiocarbon calibration curves: an unsupervised machine learning approach 

Ana-Cristina Mârza, Laurie Menviel, and Luke Skinner

Radiocarbon may serve as a powerful dating tool in palaeoceanography, but its accuracy is severely limited by the need to calibrate radiocarbon dates to calendar ages. A key problem is that marine radiocarbon dates must be corrected for past offsets from either the contemporary atmosphere (i.e. ‘reservoir age’ offsets) or a modelled estimate of the global average surface ocean (i.e. delta-R offsets). This presents a challenge because the spatial distribution of reservoir ages and delta-R offsets can vary significantly, particularly over periods of major marine hydrographic and/or carbon cycle change such as the last deglaciation. Modern reservoir age/delta-R estimates therefore have limited applicability.  The construction of regional marine calibration curves could provide a solution to this challenge, if coherent regions could be defined. Here, we use unsupervised machine learning techniques to define distinct regions of the surface ocean that exhibit coherent behaviour in terms of their radiocarbon age offsets from the contemporary atmosphere (R-ages). We investigate the performance of different clustering algorithms applied to outputs from different numerical models. Comparisons between the cluster assignments across model runs confirm some robust regional patterns that likely arise from constraints imposed by large-scale ocean and atmospheric physics. At the coarsest scale, regions of coherent R-age variability are associated with the major ocean basins. By further dividing basin-scale shape-based clusters into amplitude-based subclusters, we recover regional associations that cohere with known modern oceanographic processes, such as increased high latitude R-ages, or the propagation of R-age anomalies from the Southern Ocean to the Eastern Equatorial Pacific. We show that the medoids for these regional sub-clusters provide significantly better approximations of simulated local R-age variability than constant offsets from the global surface average. The proposed clusters are also found to be broadly consistent with existing reservoir age reconstructions that span the last ~30 ka. We therefore propose that machine learning provides a promising approach to the problem of defining regions for which marine radiocarbon calibration curves may eventually be generated.

How to cite: Mârza, A.-C., Menviel, L., and Skinner, L.: Towards the construction of regional marine radiocarbon calibration curves: an unsupervised machine learning approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7498, https://doi.org/10.5194/egusphere-egu24-7498, 2024.

EGU24-8105 | Posters on site | CL1.2.10

Rigorous Identification of Variations and Changepoints in the Observed Rates of Radiocarbon Samples Over Time  

Timothy J Heaton, Sara Al-assam, and Edouard Bard

A commonly-used approach to estimate changes in the frequency of past events or the size of populations looks at variations in the rate of archaeological and environmental samples (e.g., charcoal from fires, human/animal bones, or other evidence of occupation) found at a site over time. Time periods with large numbers of samples suggest increased activity, while those with few samples indicate a reduced level of activity. Variations and abrupt changes in the rate of observed samples might suggest the influence of important external environmental factors. This paradigm is known as “dates-as-data”.

The reliability of such a “dates-as-data” approach is highly dependent upon our ability to estimate the calendar ages of the discoveries. Most archaeological/environmental dates are obtained using radiocarbon (14C). All 14C determinations need to be calibrated in order that they can be understood on the calendar scale. This introduces considerable uncertainties in the resultant calendar ages and complicates the identification of changepoints in the calendar year rates at which samples occur.

In this talk, we provide a statistically rigorous approach to overcome these challenges. We model the occurrence of events (each assumed to leave a 14C sample in the archaeological/environmental record) as an inhomogeneous Poisson process, estimating the varying rate of samples using reversible-jump Markov Chain Monte Carlo. Given a set of radiocarbon samples, we aim to reconstruct how their occurrence rate varies over calendar time and identify if there are statistically significant changepoints in the rate at which the samples arise (i.e., specific times at which the rate of events abruptly changes).

We will demonstrate our approach on data exploring the expansion of humans, and the parallel disappearance of megafauna, in the Yukon and Alaska in the late Pleistocene and early Holocene: investigating both the timings of such migrations in comparison with the climatic changes known to have occurred during this period, and the potential interactions between humans and the various species in the region.

How to cite: Heaton, T. J., Al-assam, S., and Bard, E.: Rigorous Identification of Variations and Changepoints in the Observed Rates of Radiocarbon Samples Over Time , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8105, https://doi.org/10.5194/egusphere-egu24-8105, 2024.

EGU24-8147 | ECS | Orals | CL1.2.10

A unique preservation window capturing coastal-marine landscape evolution across the MIS5-4 cooling event (Late Pleistocene, North Sea Basin) 

Irene Waajen, Timme Donders, Freek Busschers, Frank Wesselingh, Friederieke Wagner-Cremer, Francien Peterse, Sytze van Heteren, and Ruth Plets

The Late Pleistocene MIS5 - MIS4 transition (ca. 80-70 ka) is globally known to correspond to a major cooling event accompanied by a large decline in eustatic sea level. This transition must have radically changed coastal landscapes worldwide, affecting basin shape, salinity regimes, river courses, as well as biota. Most existing records are from either local lacustrine, ice core or distal oceanic records, while dated and continuous records from coastal environments are lacking. Within the southern North Sea Basin a unique record of coupled terrestrial-marine signals exists in the deposits of the Brown Bank Formation, covering the MIS5-MIS4 transition. Here, we target the Brown Bank Formation to produce a new integrated palaeoenvironment and -climate framework for the MIS5-4 transition and show biotic and abiotic environmental response to rapid cooling in a coastal area.

Multi-proxy records of lipid biomarkers, pollen, mollusk and diatom assemblages for the MIS5-4 transition in the center of the southern North Sea are combined with seismic facies determinations. The Brown Bank Formation consists of multiple facies representing multiple depositional phases around the MIS5-4 transition, and provides insights into the cooling of the terrestrial and shallow marine environments. On land, the vegetation changed from boreal forests to more open, grassland vegetation, combined with an increase in soil erosion. At the same time the shallow marine environment of the southern North Sea experienced subarctic to arctic marine conditions with a high input of soil material. These continued cool marine conditions have not been described earlier for this region and show that sea level remained high and lagged local cooling, as inferred from lipid-biomarker palaeothermometry. Assuming that this lag between sea-level and temperature change is common during cooling events, it is a potential mechanism creating sediment preservation windows during the onset of glacial intervals in shallow marine environments. Preserved records like the one presented here are valuable because they capture both the unique changes in cold marine environments, as well as informative terrestrial signals that are rarely preserved onshore.

How to cite: Waajen, I., Donders, T., Busschers, F., Wesselingh, F., Wagner-Cremer, F., Peterse, F., van Heteren, S., and Plets, R.: A unique preservation window capturing coastal-marine landscape evolution across the MIS5-4 cooling event (Late Pleistocene, North Sea Basin), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8147, https://doi.org/10.5194/egusphere-egu24-8147, 2024.

EGU24-9635 | ECS | Posters on site | CL1.2.10

Is climate warming causing eutrophication and anoxia? Lessons learned from Late-Glacial sediments of Lakes Amsoldingen and Soppen, Switzerland.  

Stan J. Schouten, Petra Zahajská, Noé R.M.M. Schmidhauser, Andrea Lami, Paul D. Zander, Rik Tjallingii, Petra Boltshauser-Kaltenrieder, Jacqueline van Leeuwen, Luyao Tu, Hendrik Vogel, and Martin Grosjean

Many lakes nowadays experience eutrophication, which poses significant threats to ecosystem stability and people who depend on lakes for freshwater. Lake hypoxia is a state with low dissolved oxygen and often associated with external nutrient additions to the lake. Hypoxia typically deteriorates lake water quality by 1) changing the chemistry of the lake water, and 2) challenging heterotrophic organisms but promoting growth of bacterial autotrophs that are adapted to anoxia and may produce harmful toxins. Little is known about how external factors (e.g., nutrients, climate) and algal/bacterial community dynamics compounded into the chemical deterioration of lake water and shaped lake ecology. We hypothesize that, at times without human disturbance, trophicity and hypoxia may have been driven by rapid climatic shifts (e.g., Dansgaard-Oeschger Events, DOE) with a rate and extend comparable to or faster than current global warming.

To gain insights into the driving processes of natural eutrophication and recovery phases, we studied the sedimentary records of two comparable Swiss lakes (Soppensee and Amsoldingersee) focussing on their (bio-)geochemistry during the Last Glacial Maximum and Late Glacial (17.0-11.6 cal. kyr. BP). The chronology of the cores was obtained using the Laacher See Tephra, a set of C-14 dated macrofossils, and bio-stratigraphic markers. We combined sequentially extracted data on phosphorous (P), iron (Fe), and manganese (Mn) to elaborate on redox-induced changes within the P, Mn, and Fe cycles. We reconstructed the changes in past primary producer communities using coloured biomarkers – chloro-pigments and carotenoids inferred by HPLC – as proxies. Using hyperspectral imaging, we assessed bulk pigment groups for leads and lags between primary producer groups on a sub-millimetre resolution.

Both lakes experienced similar large-scale forcings and have similar catchment properties. According to our results, the lakes both record algal blooms and anoxia in the Late Glacial, yet there are, surprisingly, significant differences in the timing of these eutrophication phases and anoxia events between the lakes. The Soppensee pigment record responded to the initial Bølling warming (14.6 cal. kyr. BP) by developing eutrophic conditions in a stratified lake with hypolimnetic anoxia and redissolution of redox sensitive phosphorous, iron and manganese. In Amsoldingersee, pigment data shows clear anoxic events that pre-date the Bølling warming and relate consistently to the colder phases within the Late-Glacial (GS-2/Heinrich Event 1, GI-d, GI-c3, and GS-1). In contrast to Soppensee, total chlorophyll, and carotenoids peaked when the climate was cool and dry, advocating for substantial aquatic production during cold periods. However, the rate of compositional change (RoC) was highest during the three major climatic transitions (DOE-1, Onset Younger Dryas, Onset Holocene), and not during the anoxic phases. From ordination experiments, we further infer that algal/bacterial communities indeed recovered from their anoxic states. In addition, we noticed a surprisingly high pigment diversity throughout the Oldest Dryas (GS-2). Our data add to the view of a dynamic landscape evolution during the Oldest Dryas (Heinrich Event 1) which was previously assumed to be a stable cold phase in the peri-alpine area.

How to cite: Schouten, S. J., Zahajská, P., Schmidhauser, N. R. M. M., Lami, A., Zander, P. D., Tjallingii, R., Boltshauser-Kaltenrieder, P., van Leeuwen, J., Tu, L., Vogel, H., and Grosjean, M.: Is climate warming causing eutrophication and anoxia? Lessons learned from Late-Glacial sediments of Lakes Amsoldingen and Soppen, Switzerland. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9635, https://doi.org/10.5194/egusphere-egu24-9635, 2024.

EGU24-10704 | ECS | Posters on site | CL1.2.10

Millennial-scale changes in hydroclimate during the last glacial period in central Europe reconstructed from leaf wax δD 

Paul Zander, Frank Sirocko, Xiaojing Du, Chijun Sun, Florian Rubach, Sarah Britzius, Gerald Haug, and Alfredo Martínez-García

Millennial-scale climate events during the last glacial period, such as Dansgaard-Oeschger cycles and Heinrich events, are well-documented in ice cores and marine sediments. During Dansgaard-Oeschger cycles of the last glacial period, repeated rapid warming events of a similar magnitude to modern-day warming occurred over the North Atlantic region. However, the impacts of these fluctuations on hydroclimate in Europe remain poorly constrained, mainly due to a lack of high-resolution, well-dated paleoclimate records. Here, we use D/H ratios (δD) measured on n-alkanes derived from leaf waxes preserved in lacustrine sediments from Eifel maar crater basins to reconstruct changes in hydroclimate. Our record spans the past 60,000 years and is tied to the Greenland NGRIP ice core chronology using a high-resolution index of lake productivity. Initial results show that δDwax was more depleted during interstadial phases of the last glacial period. Multiple factors may influence δDwax; however, if an isotope “temperature effect” played a dominant role, the warmer interstadials would have been associated with more positive δDwax values, in contrast to the observations here.  Thus, we interpret low δD during interstadials as a signal of wetter, more humid conditions, possibly related to a shift towards more winter precipitation due to changes in the position of the westerlies. We compare our proxy measurements with an isotope-enabled transient climate simulation of the last deglaciation (iTRACE) to constrain the dynamical factors associated with changes in precipitation δD over stadial/interstadial changes. These results provide important constraints on past millennial-scale hydrological changes in Europe in response to changes in North Atlantic circulation.

How to cite: Zander, P., Sirocko, F., Du, X., Sun, C., Rubach, F., Britzius, S., Haug, G., and Martínez-García, A.: Millennial-scale changes in hydroclimate during the last glacial period in central Europe reconstructed from leaf wax δD, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10704, https://doi.org/10.5194/egusphere-egu24-10704, 2024.

EGU24-10736 | Posters on site | CL1.2.10

Marine radiocarbon reservoir age simulations for the past 50000 years revisited 

Martin Butzin and Gerrit Lohmann

Prior to about 14 ka BP, the most recent radiocarbon (14C) calibration curve IntCal20 is based on a combination of terrestrial and marine 14C archives. To gain insight into the spatio-temporal evolution of the involved marine 14C records and their systematic 14C concentration differences from the atmosphere, IntCal20 has considered marine reservoir age (MRA) simulations of the LSG ocean general circulation model. The LSG model was not fully coupled to the atmosphere and did not include a prognostic sea ice component. Instead, it applied various stadial and interstadial climate boundary conditions to assess upper and lower bounds of past climate variations and the associated effects on past MRAs. Here, we present results of new long-term MRA simulations which overcome this limitation. We apply the Earth system model of intermediate complexity CLIMBER-X which we have equipped with ∆14C and noble gas tracers. CLIMBER-X is forced with insolation, greenhouse gas concentrations, and continental ice sheets. Radiocarbon is prescribed in the atmosphere according to IntCal20. While the new simulations confirm some of the LSG model results at the global scale, there are considerable regional differences. For example, we find weaker inhibition of marine 14CO2 uptake in the presence of sea ice and hence lower polar MRAs than the LSG model. Moreover, we find that continental ice sheet forcing affects MRAs at the ocean-basin scale. This is particularly the case during the last deglaciation for which some meltwater discharge reconstructions could be questioned according to our results.

How to cite: Butzin, M. and Lohmann, G.: Marine radiocarbon reservoir age simulations for the past 50000 years revisited, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10736, https://doi.org/10.5194/egusphere-egu24-10736, 2024.

EGU24-11033 | ECS | Posters on site | CL1.2.10

Variations of the authigenic 10Be/9Be-ratio in marine sediments during the Laschamps event and their use for dating of marine sediments 

Julia Loftfield, Thomas Frederichs, Johannes Lachner, Lester Lembke-Jene, Jiabo Liu, Norbert Nowaczyk, Georg Rugel, Konstanze Stübner, and Florian Adolphi

The atmospheric production rate changes of cosmogenic 10Be are caused by variations of the Earth’s and Sun’s magnetic fields and are recorded worldwide in different climate archives (e.g. ice cores, marine/lacustrine sediments, speleothems). This makes 10Be a useful tool to synchronize them, thereby overcoming the limitations in precision and accuracy of their individual age models.

Here we present new 10Be/9Be data from a suite of marine sediment cores from the Scotia Sea, Drake Passage and South Pacific covering the Laschamps geomagnetic dipole minimum (~ 41 kaBP). Due to the reduction of the Earth’s magnetic shielding at this time, the 10Be-production rates roughly doubled, providing an ideal time marker for synchronization. We analyzed the cosmogenic 10Be and stable 9Be in the authigenic fraction of the sediments, which represents the 10Be/9Be signature of the surrounding water. Analyzing the 10Be/9Be ratio reduces the effect of variable particle scavenging rates on 10Be delivery to the sea floor. We compare our data to existing 10Be records from other marine sediment cores and ice cores, and to paleomagnetic field reconstructions. We discuss the potential and limitations of using 10Be/9Be ratios for dating marine sediments, and test whether using authigenic 10Be/9Be for synchronization is consistent with the traditional approach of matching climate records to reference sites.

How to cite: Loftfield, J., Frederichs, T., Lachner, J., Lembke-Jene, L., Liu, J., Nowaczyk, N., Rugel, G., Stübner, K., and Adolphi, F.: Variations of the authigenic 10Be/9Be-ratio in marine sediments during the Laschamps event and their use for dating of marine sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11033, https://doi.org/10.5194/egusphere-egu24-11033, 2024.

EGU24-12137 | Orals | CL1.2.10

14,700 years of climate and environmental change recorded in 17.8 meters of lake and peat deposits in the Nieuwe Veen pingo remnant, NE Netherlands 

Wim Hoek, Timme Donders, Stan Schouten, Vincent van Doorn, Jacqueline van Leeuwen, and Arjan van Eijk

Pingo remnants are the deep lakes that formed by melting of ice lenses during permafrost degradation at the end of the Last Glacial, and they are particularly abundant in the northern Netherlands. Most of these isolated circular depressions have a diameter of 100-200 meters and are filled with a 5-10 meters thick sequence of lake and peat deposits, making them valuable archives of climate and environmental change. These natural sediment- and pollen-traps record not only the rapid changes during the Last Glacial-Interglacial Transition but also reveal the Holocene forest development as well as traces of human impact in the surrounding landscape.

In this study, we report on the study of a continuous organic fill of nearly 18 meters in Nieuwe Veen, which may be the deepest pingo remnant in NW Europe. The pingo remnant fill is composed of a sequence of partly sand laminated lake and peat deposits containing fine and coarse detrital gyttjas, calcium- and iron-carbonate gyttjas and wood, sedge and moss peats with abundant macrofossils. A series of radiocarbon dates on selected terrestrial macrofossils provides a solid age model for the complete sequence starting 14,700 calendar years ago, coinciding with the first warming of the Late-Glacial Interstadial, corresponding to the onset of Greenland Interstadial 1 (GI-1). The results from 5-10 cm resolution palynological analyses reveal a complete picture of vegetation development while loss on ignition measurements at cm-resolution show the openness of the vegetation cover associated to colder periods as well as phases of human forest clearance.

A phase of particular interest is the cold Younger Dryas stadial corresponding to Greenland Stadial 1 (GS-1), which is represented by a more than 10 meters thick layer of sandy gyttjas. This allows for a reconstruction of environmental change in unprecedented detail with a resolution of potentially 1 cm/yr. The onset of the Younger Dryas stadial is abrupt and clearly visible in the core, as well as in the botanical and lithological proxies. There appear to be at least three distinct phases during the Younger Dryas stadial interval, especially reflected in the aquatic flora and lithological proxies, indicating shifting conditions in (hydro-)climate.

At the onset of the Holocene, also clearly visible, sand influx in the basin decreased rapidly due to an increasing vegetation cover in the surrounding landscape indicated by the botanical proxies. The lake system eventually changes into a fen and bog. In the Early Holocene, carbonate rich lake deposits indicate the influence of groundwater seepage. During the infilling, the source of the water changes towards atmospheric water, as evidenced by more oligotrophic species in the palynological record. Phases of forest opening related to human impact appear remarkably late in the record at about 5500 calendar years ago, with clear indications of agriculture only after 3000 calendar years ago. Final cultivation of the peatbog in the beginning of the 20th century caused the record younger than Medieval times to be destroyed.

How to cite: Hoek, W., Donders, T., Schouten, S., van Doorn, V., van Leeuwen, J., and van Eijk, A.: 14,700 years of climate and environmental change recorded in 17.8 meters of lake and peat deposits in the Nieuwe Veen pingo remnant, NE Netherlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12137, https://doi.org/10.5194/egusphere-egu24-12137, 2024.

EGU24-12386 | ECS | Orals | CL1.2.10 | Highlight

Speleothem sulfur spike confines timing and impact of late Glacial Laacher See eruption 

Sophie F Warken, Axel K Schmitt, Denis Scholz, Andreas Hertwig, Michael Weber, Regina Mertz-Kraus, Frederick Reinig, Jan Esper, and Michael Sigl

The Laacher See eruption (LSE) deposited a key tephra layer that synchronizes Late Glacial paleoclimate records across Europe, and thus provides the temporal framework to investigate the onset of the Younger Dryas cooling in the North Atlantic region. The absolute timing and climatic consequences of this event remain, however, still debated. Here, we present evidence from a high-resolution speleothem record from Herbstlabyrinth Cave, Central Germany, demonstrating distinct spikes in sulfur, fluorescent organic matter, and ash-leached trace elements assigned to the LSE and dating the event c. 13,047 BP1950, with an uncertainty of about 30–40 years. This age supports the recently published radiocarbon wiggle matching date of 13,006 ± 9 BP1950 (Reinig et al., 2021) and contradicts speculations about potential biases arising from volcanic CO2 emissions. The near-annually resolved speleothem calcite δ18O data further allows to assess the timing of the LSE and its impact on the regional climatology. Our findings exclude the LSE as a possible trigger of the Younger Dryas and indicate a regional climatic and environmental impact restricted to c. 20 years after the eruption. This unprecedented combination of stable isotopes, trace elements, annually resolved fluorescence, and radiometric dates for a single record provides independent evidence for the Late Glacial synchroneity of Atlantic-European climate relationships and opens new pathways toward a precise, absolutely dated time marker between European terrestrial and Greenland ice core records prior to the Holocene.

References

Reinig F, Wacker L, Jöris O, et al. (2021) Precise date for the Laacher See eruption synchronizes the Younger Dryas. Nature 595(7865): 66-69.

 

How to cite: Warken, S. F., Schmitt, A. K., Scholz, D., Hertwig, A., Weber, M., Mertz-Kraus, R., Reinig, F., Esper, J., and Sigl, M.: Speleothem sulfur spike confines timing and impact of late Glacial Laacher See eruption, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12386, https://doi.org/10.5194/egusphere-egu24-12386, 2024.

EGU24-12639 | Orals | CL1.2.10 | Highlight

Nordic Sea convection led abrupt North Atlantic warm events during Dansgaard-Oeschger cycles 

Margit Simon, Francesco Muschitiello, Henrik Sadatzki, Sarah Berben, Tobias Friedrich, Dag-Inge Blindheim, Lukas Wacker, Eystein Jansen, and Trond Dokken

During the last glacial period changes in the strength of ocean convection in the high-northern latitudes contributed to abrupt global climate changes known as Dansgaard–Oeschger (DO) cycles. However, the lack of high-resolution empirical evidence has yet precluded inferring the physical coupling between ocean and atmosphere. We examined Nordic Sea (NS) circulation changes by reconstructing radiocarbon ventilation ages across four DO cycles in a marine sediment core hinging on a precise multi-tephra-based synchronization to Greenland ice cores. Our results show that open ocean convection in the NS resumed ahead of the abrupt air-temperature increases recorded in ice cores by ∼400 years (95% range: 50-660 years). Thus, implying an active role of ocean dynamics where abrupt warming transitions are likely a nonlinear response to more gradual resumption of NS convection.

 

How to cite: Simon, M., Muschitiello, F., Sadatzki, H., Berben, S., Friedrich, T., Blindheim, D.-I., Wacker, L., Jansen, E., and Dokken, T.: Nordic Sea convection led abrupt North Atlantic warm events during Dansgaard-Oeschger cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12639, https://doi.org/10.5194/egusphere-egu24-12639, 2024.

EGU24-12672 | Orals | CL1.2.10

Human impacts on the environment in the preindustrial forest landscapes in Central Europe - an overview 

Michał Słowiński, Krzysztof Szewczyk, Jerzy Jonczak, Agnieszka Halaś, Agnieszka Mroczkowska, Dominika Łuców, Sandra Słowińska, Sebastian Tyszkowski, Anna Kowalska, Ewa Kołaczkowska, Paweł Swoboda, Aleksandra Chojnacka, Barbara Gumińska-Nowak, Mateusz Kramkowski, Cezary Kardasz, Vincenzo Barbarino, Agnieszka M. Noryśkiewicz, Bogusława Kruczkowska, Dariusz Brykała, and Tomasz Związek

Over the past few millennia, human activity has been one of the most unpredictable factors influencing environmental transformations. Human activities related to agriculture and land use are the primary forces driving the creation of new landscapes. Conversely, the influence of other factors on landscape transformation remains incompletely understood. In particular, forests have been exploited not only for timber but also for various wood-related products, including charcoal, potash, and tar. We consider that charcoal production, besides food production, which increased linearly with population growth, was a kind of turning point in human pressure on the forest environment. Particularly in the Middle Ages, when the demand for products such as glass, iron, and potash grew very rapidly, the production of these products required a higher temperature than that obtained by burning wood. However, the extent and impact of these activities on a spatial scale has not been fully recognized. Charcoal held significant economic and energy value in the pre-industrial era, evidenced by mapping over 600,000 remnants of charcoal hearths in Central Europe. Over time, the demand for energy escalated, leading to the widespread use of coal in the late 18th and early 19th centuries. Our aim is to provide a comprehensive understanding of the functioning of charcoal hearths and their role in shaping landscapes. To achieve this, we have combined research methods from biogeography, remote sensing, dendroecology, paleoecology, soil science, botany, onomastics, and art history. This interdisciplinary approach aims to capture not only the natural outcomes but also the social and economic consequences of charcoal production. Our paleoecological findings reveal an intermediate disturbance linked to the operation of charcoal hearths, influencing both short-term and long-term changes in ecosystems with a cascading effect. The production of charcoal has far-reaching consequences, exerting a substantial impact on vegetation composition, soil properties, microclimate, the water cycle, and ultimately leading to erosion, thereby affecting adjoining ecosystems. This research addresses the growing interest in the legacy of charcoal hearths in historical human activities and their pivotal role in shaping landscape transformations during the pre-industrial era.

The study is the result of research project No. 2018/31/B/ST10/02498 funded by the Polish National Science Centre.

How to cite: Słowiński, M., Szewczyk, K., Jonczak, J., Halaś, A., Mroczkowska, A., Łuców, D., Słowińska, S., Tyszkowski, S., Kowalska, A., Kołaczkowska, E., Swoboda, P., Chojnacka, A., Gumińska-Nowak, B., Kramkowski, M., Kardasz, C., Barbarino, V., Noryśkiewicz, A. M., Kruczkowska, B., Brykała, D., and Związek, T.: Human impacts on the environment in the preindustrial forest landscapes in Central Europe - an overview, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12672, https://doi.org/10.5194/egusphere-egu24-12672, 2024.

SSP3 – Sedimentology: processes, products, diagenesis

Assessing the hazard of extraordinary strong earthquakes in slowly deforming intraplate regions such as the European Alps is difficult, due to a lack of information on their occurrence. They are characterized by long recurrence intervals and identifying the source faults is difficult. However, on-fault evidence of a surface rupturing earthquake in the eastern Southern Alps was indicated by an archeoseismological study of Galadini and Galli (1999) in Egna (South Tyrol, Italy), which is in an area of low recent seismic activity. Displaced walls of a Roman Age building and paleoseismic trenches revealed the rupture of a NNE-SSW striking fault, which is dated to the 3rd century CE. To test the hypothesis, this lacustrine paleoseismology study aims to find evidence of ground shaking in the sediments of Kleiner Montiggler See, a lake located only 10 km from the archeological site. Multiproxy analysis of sediment cores reveals an event layer at a depth between 64 and 69 cm below the lake floor. It is characterized by a sharp base, high density, grainsize oscillations within a normal grading trend, a high amount of detrital material and a decrease in organic matter, compared to the background sediment. After evaluating and finally excluding many possible processes that could have induced the deposit, it can be concluded that a seismic seiche caused bottom currents, resuspending sediment and eroding material from the shore that finally got deposited as an outstanding event deposit in the deeper parts of the basin. According to our 14C based age-depth model, the event layer occurred between 8 and 450 years CE (95% probability range; mean age 222 CE), therefore supporting the hypothesis of the Roman Age surface rupture at the Egna site. This is the only event of this type recorded in the lake sediments of Kleiner Montiggler See in the last ~5000 years.  A minimum macroseismic intensity (EMS-98) of VII at the lake was estimated for the ground motion caused by the Egna fault rupture. This was done by investigating the sedimentological characteristics of the event layer, as well as considering negative evidence for other large, historical earthquakes and possible long-term catchment response recorded in the sediments. By applying an intensity prediction equation, a minimum estimated magnitude (Mi) of 6.2 ± 0.5 was derived. Due to negative evidence in Lake Ledro (63 km SW of Egna) at this timing, a maximum magnitude of 6.0 ± 0.5 was estimated. Therefore, we conclude that the magnitude of this event was most likely between 5.7 and 6.5. This study indicates that extraordinary strong and thus hazardous earthquakes can occur in areas of low recent seismic activity. It therefore provides important information for improving seismic hazard assessment and the estimation of the maximum credible earthquake in South Tyrol.

How to cite: Niederstätter, M., Strasser, M., Ramisch, A., and Moernaut, J.: Limnogeological investigations of the Montiggler Seen (South Tyrol, Italy) reveal paleoshaking evidence caused by surface rupturing earthquake in the Southern European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-81, https://doi.org/10.5194/egusphere-egu24-81, 2024.

EGU24-281 | Posters on site | SSP3.2 | Highlight

Coastal lake records of past tsunamis in South-Central Chile 

Jasper Moernaut, Evelien Boes, Valentina Moreno Allende, Philipp Kempf, Maarten Van Daele, Katleen Wils, Ariana Molenaar, Daniel Melnick, Mario Pino, Roberto Urrutia, and Marc De Batist

Overlying the subducting Nazca Plate, Chile’s coastline is notoriously prone to megathrust earthquakes and associated tsunamis, as illustrated by the 2010 Maule (Mw 8.8) and 1960 Valdivia (Mw 9.5) events. Despite numerous geophysical and paleoseismic studies, many questions remain about the timing, location and rupture extent of great tsunamigenic earthquakes. To study past tsunami inundation, coastal lakes may form complementary sedimentary archives to classical coastal plain studies as they have more accommodation space and a better preservation potential for tsunami deposits. Moreover, tsunami inundation may lead to prolonged changes in the lake system that are reflected in its sedimentary record. Here we present an overview of published and ongoing research on four coastal lake systems in Chile, i.e. Lake Gemelas West, Lake Huelde, Lake Cucao and Lake Huillinco. Due to their different basin and barrier morphologies, distance to the ocean and temporally-changing ocean connectivity, we expect significant differences in how tsunami inundation is recorded in their sediments. We used the 1960 tsunami deposit in these systems as a reference for which we constrain its sedimentological characteristics and spatial distribution within the lakes. Geochemistry of the pre- and post-1960 sediments is compared based on XRF scans, carbon isotopes and microfacies analysis. This comparison shows that lakes close to the Pacific (i.e. Lake Cucao, Huelde and Gemelas West) contain typical tsunami sands sometimes with mud-rip up clasts, whereas the inland Lake Huillinco exhibits a drastic change in inorganic geochemistry (e.g. a sudden increase in S) that persists until present. We propose that a large amount of salt water propagated in Lake Huillinco, leading to a permanent stratified water body, anoxic bottom water conditions and the preservation of varves. Similar long-lived impacts are also inferred for prehistoric tsunami events in Lake Huelde, where post-tsunami sediments often show varves during a few decades, whereas pre-tsunami sediments are typically homogenous. This study shows that besides tsunami sands, tsunami inundation can also produce long-lived changes in coastal lake systems that are recorded in their sedimentary archive and can be used to infer past tsunami occurrence.

How to cite: Moernaut, J., Boes, E., Moreno Allende, V., Kempf, P., Van Daele, M., Wils, K., Molenaar, A., Melnick, D., Pino, M., Urrutia, R., and De Batist, M.: Coastal lake records of past tsunamis in South-Central Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-281, https://doi.org/10.5194/egusphere-egu24-281, 2024.

EGU24-321 | Orals | SSP3.2

Mid-to-Late Holocene history of mass movement deposits at maar Lake Issarlès (Ardèche, France): a paleosismological record ? 

Guillaume Jouve, Emmanuel Chapron, Léo Chassiot, Anthony Foucher, Jean-Paul Raynal, and Emmanuelle Defive

Located in Massif Central (Ardèche, Auvergne-Rhône-Alpes, France), Lake Issarlès experienced since 1954 decametric lake level changes due to EDF water management. It has been hypothesized in several endoreic and maar lakes that lake level fluctuations can increase the recurrence of mass movement deposits (MMDs) because of their steep slopes (Kliem et al., 2013). The deep basin of the maar Lake Issarlès is filled by several meters of MMDs clearly visible in seismic reflection surveys and sediment cores. Here, we present results from a multiproxy study (geophysics, radiography, XRF, radionuclides & radiocarbon dating) that investigates the potential of Lake Issarlès as a paleo-seismological recorder (Defive et al., 2023).

Derived from a geophysical survey using a 4 kHz from Knudsen in June 2019 (five months before Le Teil earthquake; see details below) a coring campaign was conducted in 2020 from an anchored platform in the central deep basin, together with a new seismic reflection survey using high-resolution sub-bottom profiler Echoes 10 000. Acoustic sub-bottom data highlight several MMDs in the central basin and at the bottom of slopes, and a recent thin reflector close to the water-sediment interface. At about 7 meters in sediments, a metric sized MMD prevents deeper acoustic penetration. The 7 m-long composite sequence, documented by radiography, geochemistry, radiocarbon, radionuclides and “varves” counting, consists of laminated sediment interrupted by rapidly deposited layers such as clayey layers, MMDs, slumps and turbidites. The first event could be linked to the recent damaging Mw 4.9 (MLv 5.4) earthquake that occurred on November 11th, 2019 in Le Teil village, 60 km east from Lake Issarlès. Another event is contemporaneous with the installation of underground pipes between 1947 and 1953 by EDF, and two events are synchronous with regional historical earthquakes occurred at Tricastin in 1934 & 1873 (MLv ~7) (20 km south of Le Teil).

The whole sequence reaches back to 6000 years (radiocarbon dating) and delivers at least ten main events. Four main sedimentary units are derived from (1) the recurrence of MMDs visible in the sediment cores & the seismic profiles, (2) the dynamic of the main driver PC1 of the Principal Component Analyses of XRF data as well as the inc/coh ratio fluctuations, which is a proxy of organic matter content (Jouve et al., 2013; Guyard et al, 2007). Changes in sedimentation rates and sedimentary dynamics extracted from this multiproxy study suggests the lake sensitivity to record paleoearthquakes may have fluctuate through time and that the magnitude of past events cannot be extrapolated from the size or volume of the MMDs.

 

Kliem et al. (2013b) Quaternary Science Reviews 71, 131–146.

Defive et al. (2023) Quaternaire 34(2), 93-122

Jouve et al. (2013) Quaternary Science Reviews 71, 191-204

Guyard et al. (2007) Quaternary Science Reviews 26, 2644-2660

Chapron et al. (2022) Quaternary International 636, 134-153

How to cite: Jouve, G., Chapron, E., Chassiot, L., Foucher, A., Raynal, J.-P., and Defive, E.: Mid-to-Late Holocene history of mass movement deposits at maar Lake Issarlès (Ardèche, France): a paleosismological record ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-321, https://doi.org/10.5194/egusphere-egu24-321, 2024.

EGU24-458 | ECS | Posters on site | SSP3.2

Quantitative calibration of the lacustrine seismograph using sedimentary imprints of recent megathrust earthquakes in south-central Chile 

Katleen Wils, Gonzalo Montalva, Jasper Moernaut, Maarten Van Daele, and Marc De Batist

Accurate seismic hazard assessment strongly relies on paleoseismic research, providing long timescales of past seismic shaking, hereby potentially also revealing earthquakes that were larger than the highest-magnitude earthquakes known from historical or instrumental records. In this respect, lakes often provide long and highly sensitive shaking records, and lacustrine paleoseismology has evolved into an invaluable methodology for reliable reconstructions of earthquake recurrence intervals around the world. A thorough understanding of the relation between the component(s) of strong ground motion (e.g., PGA, PGV, duration) and the resulting sedimentary signature is, however, still missing. As a result, characterization of the source parameters of paleo-earthquakes, such as magnitude and location, up to now relies solely on qualitative or semi-quantitative considerations.

Previous studies have aimed at calibrating the lacustrine seismograph by attributing the occurrence or absence of coseismic imprints (e.g., turbidites) to intensities of seismic shaking. These intensity values are usually expressed on the macroseismic scale, as such information is more readily available compared to instrumental data for recent as well as historical earthquakes. These are, however, relatively subjective ground motion measures, unable to capture the various aspects of strong ground motion. In this study, we determine the relationship between quantitative ground motion measures on the bottom of a lake and the sedimentary shaking imprints identified therein. To achieve this, we focus on the sedimentary signature of instrumentally recorded megathrust earthquakes in south-central Chile. This includes the 1960 Mw 9.5 Valdivia earthquake and the 2010 Mw 8.8 Maule earthquake. A compilation of existing sedimentological data shows that coseismic deposits related to either of these events are identified in over 20 lakes. By linking the imprint characteristics for both earthquakes to the local ground motions, we bridge the gap between sedimentology and seismology, opening perspectives towards quantitative characterization of paleo-earthquakes.

How to cite: Wils, K., Montalva, G., Moernaut, J., Van Daele, M., and De Batist, M.: Quantitative calibration of the lacustrine seismograph using sedimentary imprints of recent megathrust earthquakes in south-central Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-458, https://doi.org/10.5194/egusphere-egu24-458, 2024.

Lacustrine settings constitute a unique environment that preserves detailed expressions of allocyclic signals such as those of climate and tectonics. Possible decryption of these signatures may stem from careful scrutiny of the sedimentation dynamics (temporary base-level variations), lake-level fluctuations (accommodation), and resulting strata bounding surfaces that are used to build a conventional sequence stratigraphic framework. The present work deals with this challenge and provides insights from a case study where lacustrine sedimentation occurs onto a tectonically active reverse drag associated with normal faulting within a key climate region (Lake Ifrah, Northwest Africa). Moreover, we investigated soft-sediment deformation structures (SSDSs) within Lake Ifrah sediments, which can be good proxies for neotectonic and paleoseismic activities. We analyzed both brittle and liquidization-induced SSDSs, including load structures, water-escape structures, shrinkage cracks, subsidiary grabens, and bed-parallel slips. Up to five facies models (accounting for lithological domination, wind-driven energy, and lake-level state) and three lowest rank T-R sequences, deposited since the Marine Isotope Stage-3 (MIS-3), have been identified. Periods with sustained high lake levels appear to be mainly precession-paced (as during MIS-3 and the Early Holocene). Furthermore, sedimentation dynamics are shown to probably respond to millennial timescale climate variability associated with North Atlantic cooling events (Dansgaard-Oeschger stadials, Heinrich events) and, interestingly, to enhanced Saharan winds during the deglacial period. On the other hand, tectonism had a rather instantaneous effect on lake level and sedimentation. Two tectonic pulses marking instantaneous differential hanging-wall subsidence have triggered a sharp drop in relative lake level, hence conditioning a forced regression. Facies analysis and deformation-trigger assessment helped to discern endogenic from exogenic triggers, with seismic activity inferred as a primary cause for liquidization-induced deformations.

How to cite: Azennoud, K., Baali, A., and Ait Brahim, Y.: Imprints of climate and neotectonic activity in lake sediments developed upon a reverse drag (Lake Ifrah, NW Africa): Integration of detailed sedimentological and sequence stratigraphic approaches., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-695, https://doi.org/10.5194/egusphere-egu24-695, 2024.

The South Caspian Basin, subject to intense sedimentation due to its location in the Arabian-Eurasian collision zone, is known worldwide for its rich oil and gas deposits. It is also the region with the densest concentration of mud volcanoes in the world. On the western flank of the basin (East Azerbaijan), numerous surface oil-bearing occurrences and more than 100 oil shale outcrops are recorded. The results of studies carried out to date indicate the role of predominantly Upper Maikop (Lower Miocene) sediments in the formation of rich oil fields. However, the extraction of industrially important oil from Eocene deposits in the western part of the country makes one think positively about their prospects in East Azerbaijan.

For the first time, we study the mineralogical and geochemical characteristics of oil shale rocks in the rock-ejecta of mud volcanoes as well as surface outcrops of Eastern Azerbaijan and compare the formation characteristics, and oil and gas potential of the Eocene and Upper Maikop sediments at the Paleogene-Miocene units.

The results of our research revealed for the first time the high oil-generation potential of the Middle Eocene oil shale sedimentary complex containing type II kerogen, characterized by a thickness of 200-300 m. We believe that a major contribution to the formation of gas fields in the South Caspian basin is made by the Upper Maikop oil shales, which are formed under conditions of more intense input of terrigenous materials and preserve kerogens of types II-III and III. Compared to the Maikop oil shales, the richness of organic matter in the Eocene oil shales is due to the closer connection of the paleobasin with the sea, and the influence of volcanic ash and higher primary paleobioproductivity on sedimentation.

How to cite: Abbasov, O. R., Aliyev, A. A., and Baloglanov, E. E.: A Comparative mineralogical and geochemical studies of Eocene and Maikop oil shales in Eastern Azerbaijan: Stratigraphic controls on formation of oil and gas hydrocarbons in the South Caspian basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-925, https://doi.org/10.5194/egusphere-egu24-925, 2024.

EGU24-1672 | ECS | Orals | SSP3.2

A drastic Late-Holocene lake level rise of Lago Llanquihue, Chile´s second largest lake  

Stephanie Benischke, Simon Thomaser, Katleen Wils, Ariana Molenaar, Valentina Moreno Allende, Jean Nicolas Haas, Daniel Melnick, Marc De Batist, Michael Strasser, Jürgen Konzett, Roberto Urrutia, and Jasper Moernaut

South-Central Chile is a geodynamically very active area that experiences great subduction megathrust earthquakes, mass-wasting processes and frequent volcanic eruptions. These processes can induce sudden landscape changes that leave long-lasting geomorphological and sedimentary traces. They can also lead to significant lake level rise, but evidence for this is exclusively found under water and hardly investigated. Lago Llanquihue (41.156°S; 72.816°W) is a large and deep (40 x 40 km; 317 m deep) piedmont lake at the western foot of the Andes, and forms an important touristic hotspot. Its current outflow is at the western edge and its small catchment is dominated by two active volcanoes: Osorno and Calbuco. Based on previous geomorphological studies in the 1960-70s, it was hypothesized that the lake level of Lago Llanquihue was much lower during most of the Holocene and rose to its present level only in the Late Holocene. According to the hypothesis, lahars and/or lava flows in the late Holocene dammed the outflow in the eastern part of the lake system leading to lake level rise and subsequent drainage towards the west through the frontal moraine belts.

In this study, we aim to test and constrain this hypothesis by investigating the submerged geomorphological features and sedimentation patterns in Lago Llanquihue. We complement this data by a sedimentary study of Laguna La Poza, a small lake (1.7 x 0.2 km; 6 m deep) in a fluvial valley that is believed to have been inundated by the Late-Holocene lake level rise. Seismic-stratigraphic analysis of Lago Llanquihue reveals submerged lake level terraces (ca. 35-55 m water depth) of which individual levels can be traced in different parts of the lake. These terraces are constituted of erosional unconformities and delta topset geometries, and are covered only by a thin (0.5-3 m) drape of lacustrine sediments. Short sediment cores show different lithologies below these unconformities: fine-grained grey laminated sediments with dropstones, or coarse sand with shell fragments. These are interpreted as glaciolacustrine sediments from Late Glacial times and as sandy beach environments, respectively. Additionally, Laguna La Poza shows a significant change in sedimentation at about 1 m depth, where a laterally-variable fining-upwards medium sand to gravel unit with pronounced cross-stratification is covered by horizontally-stratified fine-grained organic-rich lake sediments. We interpret this sequence as evidence for a sudden inundation of a fluvial valley by a rising Lago Llanquihue. Given the rather thin drape of lake sediments over the unconformity (Llanquihue) and fluvial sediments (La Poza), a Late Holocene timing of lake level rise is plausible. Current investigations aim at correlating both lacustrine sedimentary records by geochemical analysis of tephra marker layers and use 14C dating to constrain the timing of the sudden lake level rise.

How to cite: Benischke, S., Thomaser, S., Wils, K., Molenaar, A., Moreno Allende, V., Haas, J. N., Melnick, D., De Batist, M., Strasser, M., Konzett, J., Urrutia, R., and Moernaut, J.: A drastic Late-Holocene lake level rise of Lago Llanquihue, Chile´s second largest lake , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1672, https://doi.org/10.5194/egusphere-egu24-1672, 2024.

Annually varved lake sediments are great environmental archives giving unique insights in past environmental and climate settings and changes. They can also be used as an archive of past status and changes in erosion dynamics of the lake’s catchment.

In an earlier publication, Lavrieux et al. (2019), we used the compound-specific stable carbon isotopes of long-chain fatty acids (LC-FAs) to track back changes in the erosion dynamics and associated land-use at the catchment scale at Lake Baldegg catchment, Central Switzerland. In the 130-years old varved lake sediment core from Lake Baldegg we discriminated grassland, arable land and forest soils using the d13C composition of LC-FAs C26:0 and C28:0, but for the sediments older than 1940 we were not able to explain the isotopic signal by today’s terrestrial sources. The isotopic signal of the LC-FAs C24:0 and C26:0 in the lake sediment was significantly depleted compared to the terrestrial input signal. To explain the latter, we checked hypothetical additional sources of the assumed terrestrial long-chain fatty acids like (1) the influence of historical peatlands, (2) former reed grass areas around the lake, and (3) in-situ LC-FA production by aquatic organisms.

Consistent with our results, van Bree et al. (2018) and Volkman et al. (1988, 1998) already showed alternative production of long chain fatty acids by aquatic organisms, but in rather extreme environments, like polar or equatorial regions.

While we could not find historical peatlands or former reed grass areas as a likely source to our sediments,  algal biomass from Lake baldegg shows C24:0 FA, in small quantities, but depleted compared to the terrestrial catchment sources. With these results we can create a potential scenario which would explain the different isotopic deviations of the LC-FAs in the lake sediments before 1940.

This indicates at least the potential source of depleted LC-FAs 90 years ago, when the lake status was severely eutrophic.

The proof of significant aquatic contribution of LC-FAs to lacustrine sediments in Swiss lakes would be an important finding also regarding the common use of assumed terrestrial biomarkers in lake sediments for climate reconstruction.

 

References:

Lavrieux, M., Birkholz, A., Meusburger, K., Wiesenberg, G. L. B., Gilli, A., Stamm, C., and Alewell, C.: Plants or bacteria? 130 years of mixed imprints in Lake Baldegg sediments (Switzerland), as revealed by compound-specific isotope analysis (CSIA) and biomarker analysis, Biogeosciences, 16, 2131–2146, https://doi.org/10.5194/bg-16-2131-2019, 2019.

van Bree, L. G. J., Peterse, F., van der Meer, M. T. J., Middelburg, J.J., Negash, A. M. D., De Crop, W., Cocquyt, C., Wieringa, J.J., Verschuren, D., Sinninghe Damsté, J.S., Seasonal variability in the abundance and stable carbon-isotopic composition of lipid biomarkers in suspended particulate matter from a stratified equatorial lake (Lake Chala, Kenya/Tanzania): Implications for the sedimentary record, Quat. Sc. Rev., 192. 208-224, 2018.

Volkman, J.K., Burton, H.R., Everitt, D.A. and Allen, D.I.: Pigment and lipid compositions of algal and bacterial communities in Ace Lake, Vestfold Hills, Antarctica, Hydrobiologia, 165, 41-57, 1988.

Volkman, J.K., Barrett, S.M., Blackburn, S.I., Mansour, M.P., Sikes, E.L. and Gelin, F.: Microalgal biomarkers: A review of recent research developments, Org. Geochem., 29, 1163-1179, 1998.

How to cite: Birkholz, A. and Alewell, C.: Aquatic microorganisms are a (potential) provider of long-chain fatty acids to lake sediments in the temperate climate zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1960, https://doi.org/10.5194/egusphere-egu24-1960, 2024.

The carbon dynamics of lacustrine deposits play an important role in controlling the atmospheric carbon cycle. However, the influences of various sedimentary factors on carbon accumulation in lacustrine deposits are rarely known. In this study, the petrological and geochemistry analyses of organic-rich (average total organic content = 24.22 wt.%) lacustrine deposits and organic-poor (average total organic content = 2.48 wt.%) lacustrine deposits buried under a peatland (the Zhibian peatland) in Northeast Asia are used to explore the above issues. Results suggest that the concentrations of major oxides, trace elements and rare earth elements in the organic-poor lacustrine deposits are higher than those in the organic-rich lacustrine deposits. Furthermore, these lacustrine deposits were sourced from felsic rocks. The tectonic background was continental island arc and active continental margin. Additionally, the sedimentary models of lacustrine deposits buried under peat sequence were also concluded. Organic-poor lacustrine deposits were developed in a deep-water area, that was freshwater and oxygenic condition. This type of lacustrine deposit was influenced by the frequent input of coarse-grained terrigenous debris and low productivity. In contrast, the organic-rich lacustrine deposits were developed in a shallow-water area, that was saline and anaerobic condition. This type of lacustrine deposit was influenced by a rare input of fine-grained terrigenous debris and high productivity. These findings should assist future studies on the carbon dynamics of buried lacustrine deposits. This study would provide a representative example of carbon accumulation processes and mechanisms in buried paleolake system in Northeast China.

How to cite: Zhang, M.: The influences of sedimentary environments on carbon accumulation in lacustrine deposits: Evidences from elemental geochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3687, https://doi.org/10.5194/egusphere-egu24-3687, 2024.

EGU24-3739 | ECS | Orals | SSP3.2

A 1000-year extreme flooding record from NE Asia reveals the roles of climatic and anthropogenic changes in driving basin erosion and sedimentation 

Shuang Sun, Xianliang Dong, Yunfeng Nie, Yang Li, Liya Zhu, Xianyong Cao, Hongwei Ma, Yan Li, Hong Wang, Ke Hu, and Yin Lu

Short-term hydrological monitoring has limited our understanding of how climate and human activities affect flood erosion and deposition. Here, we reconstruct a 1000-year-long extreme flooding record by analyzing drill cores from the Daling River estuary (NE China), NE Asia, based on the observation that instrumental floods normally cause coarse particle enrichment in the estuary. Our data reveal that (1) centennial-scale climate aridification coupled with vegetation coverage reduction has enhanced flood erosion and estuarine sedimentation; (2) accelerated reservoir construction and reforestation and grass planting since 1960 have consistently reduced sediment flux and coarse particles reaching the estuary. Our findings promote our understanding of basinal erosion and estuarine sedimentation under climate aridification and human pressure.

How to cite: Sun, S., Dong, X., Nie, Y., Li, Y., Zhu, L., Cao, X., Ma, H., Li, Y., Wang, H., Hu, K., and Lu, Y.: A 1000-year extreme flooding record from NE Asia reveals the roles of climatic and anthropogenic changes in driving basin erosion and sedimentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3739, https://doi.org/10.5194/egusphere-egu24-3739, 2024.

Abstract: In order to clarify the sedimentary characteristics and spatial evolution of the deep-water gravity flow deposits of the third segment of the Dongying Formation in the eastern slope belt of the Chengbei Low Uplift, under the guidance of sedimentology and sequence stratigraphy, the sedimentary characteristics, sand body distribution, sedimentary facies distribution characteristics, and evolution rules of the study area were analyzed in depth by analyzing the seismic response characteristics of the seismic profile, the combination morphology of logging curves, and the core debris. The results show that the eastern slope belt of the Chengbei Low Uplift is divided into nearshore subaqueous fans (nearshore turbidite fans) and lakebed fans (farshore turbidite fans) under the control of material sources and paleogeography. The distribution of sedimentary facies belts, fan body distribution area, sand body extension direction, and distribution pattern on the plane are controlled by the lake level, material source supply, and paleogeomorphological changes. The steep slope zone (fault zone) controls the sedimentary body with a continuous thickness of thick sand bodies that extend forward in the direction of the source and have a band-like distribution, which is a nearshore subaqueous fan. The gentle slope zone (slope zone) gradually develops into a lakebed fan with a larger scale and thinner sand distribution. It is concluded that during the sedimentary period of the third segment of the Dongying Formation in the study area, the lake level changes control the size of the gravity flow sedimentary distribution; the size of the material source supply controls the degree of development of the deep-water gravity flow sedimentation; the orientation of the material source supply controls the deep-lake-deep water gravity flow turbidite fan sedimentation mode in the distribution area of the gravity flow sedimentation, providing a geological basis for the study of the sand body development law within the fan body and oil and gas exploration and development in the study area.

Keywords: Chengbei Low Uplift; Dongying Formation; gravity flow; sedimentary system; sand body distribution.

How to cite: Zhou, L. and Zhang, L.: Study on the gravity flow depositional system of three sections of the Dongying Formation in the eastern slope zone of the Chengbei Low Bulge in the Bohai Bay Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4284, https://doi.org/10.5194/egusphere-egu24-4284, 2024.

EGU24-4368 | ECS | Orals | SSP3.2

Cryptotephra quantification in lake sediments: Two workflows developed for sites with distant Laacher See tephra fallout 

Verena Meier, Tomáš Hrstka, Joachim Ohser, Bianca Brandstätter, Gunther Kletetschka, and Daniel Vondrák

Cryptotephra research has emerged as a major tool for determination of the age of sediments and unraveling the relationship between past volcanic events and their environmental impacts. Lacustrine deposits are particularly important for continental tephra research. Lakes provide relatively stable environments conducive to the long-term preservation of (crypto)tephra layers, forming valuable continental cryptotephra archives. While studies on fingerprinting of marine tephras and peat samples are more common, the identification and quantification of cryptotephra within lacustrine records remains an underexplored area.    
In this study, we introduce innovative workflows for the quantification of cryptotephra, particularly in lake sediments with distant Laacher See tephra fallout, which represents the most important stratigraphic marker in late-glacial deposits in Central Europe. Our approach initiates with the identification of potential cryptotephra positions and thickness of the deposits, accomplished through the integration of magnetic susceptibility (MS), X-ray fluorescence (XRF), and computer tomography (medical- and micro-CT) to precisely delineate the extent of the cryptotephra layer within the sediments. The subsequent step evaluates presence and identifies the source of the present cryptotephra layer. This is accomplished using scanning electron microscopy (SEM) and polarizing microscopy to visually confirm the presence of cryptotephra and investigate its geochemical fingerprint, enabling linkage to a specific volcanic eruption.    
The key element of our study are methods for quantifying cryptotephra glass shards within sedimentary records. Shard extraction using stepwise flotation with heavy liquids and quantification using standardized markers and a polarizing microscope provides a robust, straightforward laboratory-based technique. Additionally, we offer an innovative, software-based alternative that combines TIMA analysis on thin sections with customized image analysis to study the area fraction of the glass phase, its depth-dependent variation, particle density with a focus on clustering behavior, depth-dependent particle count, total particle count, and particle size distribution within the glass phase.    
The significance of both methods lies in the efficiency and precision of cryptotephra quantification, enabling a deeper understanding of shard concentration, depth-dependent shard distribution, as well as multi-site comparison of shard influx within continental cryptotephra deposits.

How to cite: Meier, V., Hrstka, T., Ohser, J., Brandstätter, B., Kletetschka, G., and Vondrák, D.: Cryptotephra quantification in lake sediments: Two workflows developed for sites with distant Laacher See tephra fallout, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4368, https://doi.org/10.5194/egusphere-egu24-4368, 2024.

EGU24-5699 | Posters on site | SSP3.2

Application of micro-CT to resolve textural properties and assess primary sedimentary structures of deep-marine sandstones 

Gerald Degenhart, Pauline Cornard, Peter Tropper, Jasper Moernaut, and Michael Strasser

Over the past decade, there has been growing interest in the sedimentological community to use micro X-ray computed tomography to analyse microfacies in sediments and bedforms. However, little attention has been paid to the application of micro-computed tomography in lithified deposits, even though this can allow their texture to be characterised in three dimensions, providing key information about sedimentary and bedform micro structures. A novel application of micro-computed tomography in lithified sediment-gravity flow deposits is presented with the objective of characterising their internal 3D sedimentary structures. This technique is applied to three deep-marine sandstones showing different compositional properties: Cretaceous Gosau Group (Austria), Eocene Hecho Group (Spain) and the Oligocene Annot Formation (France). From micro-computed tomography data, the size of particles and their distribution throughout the sample is reconstructed in 3D, permitting a better visualisation of sedimentary textures. Particle distributions computed from micro-computed tomography are similar to those computed from thin section image analysis, corroborating the reliability of the micro-computed tomography to evaluate grain-size trends. Micro-computed tomography is complemented with micro-X-ray fluorescence and thin section petrographic analyses. In cases where mineral composition or grain size are homogeneous or matrix and grains have similar mineral composition, sedimentary structures do not appear visible from micro-X-ray fluorescence or thin section analyses. By separating particles based on their computed tomography density, it is possible to isolate the coarsest fraction, highlighting the sedimentary structures. This study demonstrates (i) the potential of micro-computed tomography in analyses of sedimentary structures from outcrop data and (ii) the importance of the mineralogical composition and degree of grain sorting in assessing the origin of structureless deposits and bedforms. Considering the importance of visualising sedimentary structures when interpreting depositional processes, micro-computed tomography is a new and reliable tool to assess the physical properties of sandstones and to analyse their internal 3D sedimentary structures.

How to cite: Degenhart, G., Cornard, P., Tropper, P., Moernaut, J., and Strasser, M.: Application of micro-CT to resolve textural properties and assess primary sedimentary structures of deep-marine sandstones, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5699, https://doi.org/10.5194/egusphere-egu24-5699, 2024.

EGU24-5762 | ECS | Orals | SSP3.2

A lacustrine sediment perspective on the seismic cycle in Southeast Tibet 

François lemot, Pierre Sabatier, Marie-Luce Chevalier, Christian Crouzet, Patrick Rioual, Anne-Lise Develle, Ziqi Fang, and Anne Replumaz

The Tibetan Plateau formation, resulting from the collision between India and Eurasia, is accompanied by significant seismic activity. Along its SE margin, the sinistral Xianshuihe fault is one of the most active faults in China. To understand the seismic cycle and estimate subsequent hazards, long-term records extending beyond historical archives are required. In Kangding's restraining bend, fault partitioning leads to seismic activity being distributed across four branches, exposing significant population and critical infrastructures to seismic hazards. To document the long-term patterns of fault activity, we identified seismically-triggered event deposits in three mountain lakes near the fault, using a multiproxy approach, including CT scanning, grain-size analysis, and XRF core scanning, associated with chronology based on palaeomagnetism, short-lived radionuclides, and radiocarbon ages. Our investigation across three sites (Yari Acuo, Yalatuo, Mugecuo) distributed over 30 km of the fault, revealed varying sensitivities to seismic events over the past ~300 years. Based on these different sensitivities to record earthquakes, this multi-site approach allowed us to relocate historical earthquakes based on sediment core evidence. However, the high frequency of events and the uncertainties in age models limit our ability to unambiguously attribute the oldest deposits to specific events. The recently retrieved 3.6 m-long core from Lake Yalatuo, on which we will apply similar analyses, appears more promising to reconstruct the long-term regional palaeoseismological record and discuss the Xianshuihe fault seismic cycle.

How to cite: lemot, F., Sabatier, P., Chevalier, M.-L., Crouzet, C., Rioual, P., Develle, A.-L., Fang, Z., and Replumaz, A.: A lacustrine sediment perspective on the seismic cycle in Southeast Tibet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5762, https://doi.org/10.5194/egusphere-egu24-5762, 2024.

EGU24-5860 | ECS | Orals | SSP3.2

brGDGT paleothermometer MBT’5ME as a novel diagnostic tool to detect thermal stratification in lakes 

Fatemeh Ajallooeian, Sarah Nemiah Ladd, Nathalie Dubois, Mark Alexander Lever, Carsten Johnny Schubert, and Cindy De Jonge

The brGDGT-based ratio MBT’5ME has been widely used in soil (1) and lake (2) systems globally to estimate changes in mean annual temperature over time. Despite the development of numerous lake-specific calibrations (3, 4), a substantial residual error (2.0-2.7 ℃) remains in temperature calibrations, suggesting the potential influence of confounding factors other than temperature on the paleothermometer MBT’5ME. Investigating changes in brGDGT distribution over both shorter (seasonal water column) and longer (last 14 ka) time scales within a single lake system has provided significant novel insights for the application of MBT’5ME in lacustrine systems.

Analyzing a dataset of lake sediment samples (n= 95) spanning three distinct climate periods: the Glacial interstadial, Younger Dryas, and Holocene, variations in brGDGTs with time within a prealpine lake sediment core offered valuable insights into the lake's environmental history and the interdependencies of brGDGTs. Within the Holocene,  the higher fractional abundance of brGDGT Ia is interpreted as driven by stronger thermal water column stratification, especially in the early Holocene (11.7-7.4 cal. ka BP) . Furthermore, the provenance and environmental drivers of the sedimentary brGDGTs were identified by comparing sediment samples to the lake's seasonal particulate matter (SPM) samples (n= 20). Although hypolimnion brGDGT isomer ratio (IR) was characterized as a function of dissolved oxygen in the lake’s SPM, only a muted influence from seasonal or permanent lake water anoxia was observed on the sedimentary brGDGTs isomer ratio (IR), and the IR is instead proposed as a secondary proxy for temperature.

While Lake Rot’s epilimnion showed a dependency between MBT’5ME and temperature (and lack of hypolimnion’s MBT’5ME dependency on temperature), the concentration changes and interdependencies of brGDGTs during the oligotrophic phase of the lake mimicked the epilimnion conditions. This suggests that coring at the oxic depth of (seasonally) anoxic lakes can prove successful for using MBT’5ME as a lake surface paleothermometer. The presence of brGDGT Ia, commonly associated with thermally stratified surface summer water, reinforced this observation, and suggests that the temperature proxy is primarily linked to thermal stratification rather than single influence of mean annual temperature. These findings have substantial implications for paleoclimate studies. It is evident that the development of seasonal stratification plays a crucial role in influencing MBT'5ME values. Consequently, MBT’5ME mainly reflects summer warmings in Lake Rot during early Holocene and colder summer temperatures for late Holocene. Finally, with minimum impact from lake’s XRF-based anoxia history, brGDGTs isomer ratio (IR), shows a strong potential to be employed as a mean annual temperature proxy.

1: Crampton-Flood et al., (2020). Geochimica et Cosmochimica Acta, 268, 142-159

2: Stefanescu et al., (2021). Organic Geochemistry, 152, 104174

3: Martínez-Sosa et al., (2021). Geochimica et Cosmochimica Acta, 305, 87-105

4: Raberg et al., (2021). Biogeosciences, 18(12), 3579-3603

How to cite: Ajallooeian, F., Ladd, S. N., Dubois, N., Lever, M. A., Schubert, C. J., and De Jonge, C.: brGDGT paleothermometer MBT’5ME as a novel diagnostic tool to detect thermal stratification in lakes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5860, https://doi.org/10.5194/egusphere-egu24-5860, 2024.

EGU24-6315 | Posters on site | SSP3.2

Thorium normalization for identification of organic carbon anomalies during the Lower Cretaceous paleolakes in the Southern Hemisphere. 

Ana Luiza Albuquerque, Victor Carreira, Gabriel Barberes, Raphaela Mattos, Igor Venancio, Pedro Abreu Affonso, Igor Viegas, and Andre Spigolon

Lagoons are suitable paleoclimatic registers. They carry information about cyclic sedimentary deposits in a paralic and closed environment. The proposed study uses gamma radiation spectrometry to calculate the normalization of thorium in a Brazilian pre-salt well located in the Campos Sedimentary basin during the rift sequence (Cabiunas and Lagoa Feia formations), especially during the deposition of the Buracica and Jiquiá shales. Thorium normalization allows a reduction in risk during exploration, in addition to increasing the potential for success in organic content determination. The radioisotopes of interest in this work are the radioactive nucleotides 40K, 238U, and 232Th, commonly found in underground formations and as constituents of rocks with high total organic TOC (Fertl, 1979). The method proposed by Saunders et al. (1993) was able to correlate airborne gamma radiation anomalies with hydrocarbon occurrences in structural and stratigraphic traps through calibration of 40K and 238U values using 232Th. The model determined the "ideal" 40K and "ideal" 238U as Ki=(Kav/Thav)Ths and Ui=(Uav/Thav)Ths. Where "s" is the measured or sampled value, "i" is the ideal value, and "av" is given as the average value. After this, it is necessary to calculate the measured and idealized values (Saunders et al., 1987) by defining KD%=(Ks-Ki)/Ks and UD%=(Us-Ui)/Us. Where KD decreases, and UD generally increases when hydrocarbons are present. A new DRAD calculation combines the two previous equations with positive DRAD values, indicating the top of hydrocarbon anomalies by calculating DRAD=UD%-KD% and DRAD=((Us/Uav)-(Ks/Kav))/(Ths/Thav). The 40K anomaly typically occurs above rock horizons with high organic content. This work presents the results of the study of thorium normalization for the location and identification of high hydrocarbon content during a continental lagunar paleoenvironment phase in the southern hemisphere.

How to cite: Albuquerque, A. L., Carreira, V., Barberes, G., Mattos, R., Venancio, I., Affonso, P. A., Viegas, I., and Spigolon, A.: Thorium normalization for identification of organic carbon anomalies during the Lower Cretaceous paleolakes in the Southern Hemisphere., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6315, https://doi.org/10.5194/egusphere-egu24-6315, 2024.

EGU24-7121 | Posters on site | SSP3.2

Advanced Lithofacies Analysis by Using X-Ray Computed Tomography 

Yen-Hsi Wu, Jyh-Jaan Huang, Neng-Ti Yu, Jiun-Yee Yen, Shyh-Jeng Chyi, and Jia-Hong Chen

Lithofacies, defined as distinctive assemblages of sedimentary characteristics, necessitate a comprehensive understanding of their past depositional environments to facilitate paleoenvironmental reconstructions, resource explorations, and effective hazard assessments. To unravel the complexities of texture variety and other sedimentary features, along with physicochemical properties, conventional methods such as core description, grain size analysis, and well logging have been widely utilized. However, these approaches have limitations due to observer-dependence, time-consuming processes, discrete sampling, and the restriction to subsurface observations, which may impede the accurate distinction of lithofacies. X-ray Computed Tomography (X-ray CT), a rapid, non-destructive, and high-resolution technique, offers an unbiased and continuous approach. It provides three-dimensional visualization of samples and allows for qualitatively and quantitatively statistical analysis in stratigraphy, addressing the limitations of conventional methods. In this study, X-ray CT was employed to examine five sediment cores containing diverse sedimentary features and distinctive materials near Dapeng Bay in southwestern Taiwan. The research aimed to evaluate the feasibility of X-ray CT in characterizing different lithofacies within this region through a structured three-step workflow, involving systematic X-ray CT scanning, extraction of CT-derived intensity and statistical data, and analogy of lithofacies of cores with modern samples of known depositional conditions. The comparative analysis of CT-derived parameters within the cores was used to distinguish the features of different lithofacies. Furthermore, organic and biological substances such as charcoals and shells were observed and defined by given radio-density, characterizing other unique lithofacies with their presence combination. The classified lithofacies in CT-derived parameters may also correspond to specific depositional processes or events. By demonstrating how the application of X-ray CT quantitatively aids in characterizing and distinguishing various lithofacies, this research may ultimately contribute to providing an analogical foundation for subsequent lithofacies analysis within comparable sedimentary settings and extended time spans in future research.

How to cite: Wu, Y.-H., Huang, J.-J., Yu, N.-T., Yen, J.-Y., Chyi, S.-J., and Chen, J.-H.: Advanced Lithofacies Analysis by Using X-Ray Computed Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7121, https://doi.org/10.5194/egusphere-egu24-7121, 2024.

EGU24-7760 | ECS | Orals | SSP3.2

Lake archives from tropical Africa: Reconstructing the paleoclimate leading to the African Rainforest Crisis 3000 years ago 

Michelle Engelhardt, Antoine De Clippele, Alfred Ludjwera, Negar Haghipour, Johan Six, Travis Drake, Lissie De Groot, Kristof Van Oost, and Jordon Hemingway

The second largest rainforest biome on Earth lies in the Congo Basin of central Africa. Due to increasing pressure associated with slash-and-burn farming practices as well as climate change, the rainforest may loose its ability to absorb atmospheric carbon. Interestingly, former studies have found evidence for a similar so-called “African Rainforest Crisis” that took place in the late Holocene, around 3000 years ago (Brncic et al. 2009; Garcin et al. 2018). There are some indications that this crisis was caused by the expansion of the Bantu people, who are believed to have migrated to this area to pursue extensive farming at this time. Pollen records, to the contrary, suggest a shift towards a drier climate as the primary mechanism inducing the crisis. Since data from this area are scarce, more information is needed to resolve the exact causes of the African Rainforest Crisis, especially since it is a likely analog for ongoing and future rainforest contraction.

To provide such information, we collected a total of about 30 m of core from 13 lakes along the rainforest-savannah boundary in the Kasaï Basin, Democratic Republic of Congo, which constitutes the southwest portion of the Congo Basin. We developed preliminary age models of the sediment records using bulk radiocarbon measurements to compare the estimated sedimentation rates. Two periods of reduced sedimentation rates around 700 and 3500 years before present have been identified. These can indicate the timing and spatial extent of erosive events usually linked to drying and a shift in vegetation. In parallel, we analyse the catchment’s vegetation through time using stable-carbon istopes to distinguish between the abundance of C3 and C4 plants. Additionally, bulk XRF and XRD data offers insights into the underlying mineralogy. First results suggest kaolinitic and quartz-rich sediments, indicating high wethering intensity. By using mineralogy as an indicator of weathering intensity, we expect to draw conclusions on the hydrology and temperature throughout the late Holocene. To further constrain the paleoclimate reconstructions, triple-oxygen isotope analysis on the clay-size fraction and pollen and charcoal analyses are planned. A holistic interpretation will aim to reveal the role of climate vs. land-use change as a trigger of the African Rainforest Crisis, which serves as an analog to better predict how the Congo rainforest will respond to today’s land use- and climate-triggered challenges.

 

REFERENCES

Brncic, T. M. et al. (2009) Holocene 19, 79–89.

Garcin, Y. et al. (2018) PNAS 115, 3261–3266.

How to cite: Engelhardt, M., De Clippele, A., Ludjwera, A., Haghipour, N., Six, J., Drake, T., De Groot, L., Van Oost, K., and Hemingway, J.: Lake archives from tropical Africa: Reconstructing the paleoclimate leading to the African Rainforest Crisis 3000 years ago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7760, https://doi.org/10.5194/egusphere-egu24-7760, 2024.

Mixed rocks refer to the rocks formed by the mixture of terrigenous clasts and carbonate sediments. In recent years, the development characteristics and sedimentary patterns of mixed rocks in saline lake basin in Upper Shahejie Formation (4th Member) of Luojia area in Zhanhua depression Bohai Bay Basin have yet to be solved, which brings certain limitation to the exploration of oil and gas in this area and some other places with the same environment. This study used detailed core description, sequence stratigraphy analysis, sedimentary analysis, and thin section observation to study the mixed rocks characteristics and sedimentary patterns of Upper Shahejie Formation (4th Member) in Luojia area, systematically. The research shows that the 4th Member of Upper Shahejie Formation in Luojia area is divided into a whole three-level sequence, including lowstand systems tract (LST), transgressive system tracts (TST), highstand systems tract (HST). Mixed rocks mainly develop in highstand systems tract, with a small amount developing in lacustrine transgressive system tracts. The lacustrine transgressive system tract has strong provenance supply, resulting in water dilution and a narrowly mixed phase zone. At highstand systems tract, the water in the lacustrine basin shrinks, and water salinization occurs. The decrease of water leads to the increase of terrigenous clast supply, forming mixed rocks and mixed strata with carbonate rocks.

During the highstand systems tract, mixed rocks and mixed strata mainly distribute in the front of fan delta and the near-fan shallow lake area. The mixed rocks in the front of fan delta are mainly affected by provenance supply. The migration of fan delta lobes caused the enhancement or weakening of provenance supply, mainly forming mixed rocks composed of rich terrigenous clasts. Lacustrine wave transformation carried the terrigenous debris from the fan delta into the shallow lake area far away from the fan delta. Frequent lake level fluctuations control the occurrence of mixing, resulting in the superposition of multiple mixing tidal flats, mainly forming mixed rocks with terrigenous clasts and carbonate rocks.

How to cite: Ma, Y., Qiu, L., Yang, Y., and Tong, Z.: The sedimentary environment and models of mixed rocks in saline lake basins: a case study on Upper Shahejie Formation ( 4th Member) of Luojia area in Zhanhua depression, Bohai Bay Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7947, https://doi.org/10.5194/egusphere-egu24-7947, 2024.

EGU24-9331 | ECS | Orals | SSP3.2

Linking marine silicate alteration signatures in pore water to dynamics of Western Antarctic Ice sheet since late Miocene 

Sarath Pullyottum Kavil, Wei-Li Hong, Tzu-Hao Huang, Ji-Hoon Kim, and Kuo-Fang Huang

Western Antarctic Ice Sheet (WAIS) grounded below sea level is experiencing rapid basal melting and is known to have undergone complete ice sheet collapse in the past. We investigate Si and Sr isotopic signatures of marine porewater and sediment from an 800-meter-long sediment core (U1532) dating back to late-Miocene (5.7 Ma) from Amundsen Sea, retrieved as a part of IODP Expedition 379. The present work explores porewater and sediment geochemical and isotopic signatures to understand marine silicate alterations and to link sedimentary signatures to glacial-interglacial dynamics of WAIS.

The sediment lithology is dominated by silty clay, dispersed with biogenic silica and ice rafted debris (IRD). The depositional environment receives high supply of terrigenous sediments during glacial times, transported by advancing WAIS towards shelf edge, evident from high sedimentation rates (upto 61 cm/kyr) and occurrence of terrestrially derived kaolinite clays. The bulk 87Sr/86Sr of sediments shows an overall increasing trend with depth, ranging from 0.7095 to 0.7225. Interestingly, porewater shows a steady increase in Sr concentration with depth (from 90 to 320 μM), except the deepest strata between 660 to 760 meter bsf, where we observe a slight decrease. The pore water 87Sr/86Sr signatures fluctuate between 0.7084 to 0.7101, with two phases of low 87Sr/86Sr ratio and three phases of higher 87Sr/86Sr ratio than contemporaneous seawater. The interaction of fluids with more radiogenic Sr rich glacigenic detrital phases can explain observed increasing phases of pore water 87Sr/86Sr signatures. The more radiogenic 87Sr/86Sr source can be traced to subglacial erosion and weathering of lower Paleozoic/Mesozoic terranes of Western Antarctica, possibly transported through (paleo)ice stream systems into the Amundsen Sea. The sediments at distinct phases of low pore water 87Sr/86Sr coincides with Miocene-Pliocene transition and late Pliocene, likely resulting from basaltic alterations, associated with subglacial volcanic provinces of West Antarctic rift system.

The pore water dissolved silicon (DSi) and δ30Si signatures results from a dynamic balance between dissolution of biogenic and reactive lithogenic phases, and formation of authigenic aluminosilicates. The DSi profile of pore water varies between 60 and 900 μM, exhibits three distinct phases of enriched DSi, associated with sediment intervals of abundant biosiliceous deposits (diatoms and radiolarians). Occurrence of IRD in these intervals points to a pelagic and hemipelagic sedimentation, associated with ice sheet retreat during warm interglacial periods. In order to distinguish possible sources of DSi to pore water, we employ a sequential leaching technique to separate major Si bearing phases from marine sediments. The biogenic silica associated with the Na2CO3 leach exhibits a higher Si/Al ratio (6 to 365) and a δ30Si between 0.6 to 1.5‰, consistent with documented range of diatoms and radiolarians globally. The metal oxy-hydroxides and clay fractions represents lightest Si pool in marine sediments, with δ30Si varying between -0.7 to -3.1‰, while lithogenic silica exhibits δ30Si between -0.5 to 0.2‰. Through careful evaluation of pore water Si isotopic signatures, we will be able to link sediment supply of Si phases to past ice sheet dynamics of Western Antarctica.

How to cite: Pullyottum Kavil, S., Hong, W.-L., Huang, T.-H., Kim, J.-H., and Huang, K.-F.: Linking marine silicate alteration signatures in pore water to dynamics of Western Antarctic Ice sheet since late Miocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9331, https://doi.org/10.5194/egusphere-egu24-9331, 2024.

EGU24-10699 | ECS | Orals | SSP3.2

An 8000 yr lacustrine paleoseismic record (Lake Iznik, NW Türkiye): Implications for the seismic cycle of the Middle Strand of the North Anatolian Fault 

Edward Duarte, Pierre Sabatier, Julia De Sigoyer, Renaldo Gastineau, Flavio S. Anselmetti, William Rapuc, Stefano C. Fabbri, Jarod Domenge, Mustafa Şahin, and Serkan Gündüz

Lacustrine sediment sequences can provide long and complete records of earthquake recurrence patterns due to their continuous nature of subaqueous sedimentation. This gives this “natural seismograph” a high sensitivity for registration of seismic shaking and accurate age-depth control, these characteristics are important parameters for high-quality seismic hazard assessments. As the middle strand of the North Anatolian Fault (MNAF) is a slow slipping fault (5 mm/yr), a long-term earthquake chronicle is required to study its behavior. Here, we report on findings from three long sediment cores (from 8.5 to 15 m), retrieved in Lake Iznik (northwest Türkiye), crossing the Iznik underwater fault, that provide insight into the local and regional earthquake cycle and thus improve the paleoseismic history for the NAF system over the last 8000 years. We used radiocarbon-based age-depth models combined with sedimentological observations, X-ray fluorescence elemental data, and seismic reflection data to reconstruct the spatiotemporal rupture variability. Recurring millimetric, coarse-grained laminae identified as event deposits were deposited synchronously at the three coring sites. Over the last 2000 years, the ages of the event deposits recorded in Lake Iznik correspond to the historical evidence of seismic activity reported along the North Anatolian Fault (NAF) system, allowing us to recognize regional earthquake-triggering mechanisms and assess seismic intervals. The event deposits are inferred to be earthquake-triggered, and the sensitivity to earthquake shaking in Lake Iznik is proportional to the sedimentation rate. Our record demonstrates that Lake Iznik has been repeatedly exposed to significant seismic shaking over the past 8000 years. Our data suggest that large earthquakes with moment magnitudes Mw >7 occur on the Iznik fault segment part of the MNAF with a mean recurrence interval of ~1000 years. At the regional scale period of seismic activity alternates with several hundred years of quiescence. This study allows us to investigate the timing of large paleoearthquakes over the last 8000 years, providing important input for seismic hazard assessment and increasing societal awareness and preparedness in the case of future catastrophic events along the MNAF.

How to cite: Duarte, E., Sabatier, P., De Sigoyer, J., Gastineau, R., Anselmetti, F. S., Rapuc, W., Fabbri, S. C., Domenge, J., Şahin, M., and Gündüz, S.: An 8000 yr lacustrine paleoseismic record (Lake Iznik, NW Türkiye): Implications for the seismic cycle of the Middle Strand of the North Anatolian Fault, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10699, https://doi.org/10.5194/egusphere-egu24-10699, 2024.

EGU24-11700 | Orals | SSP3.2

A new > 400 ka paleoenvironmental and paleoclimate record from Tenerife Island (Canary Archipelago) 

Margarita Jambrina-Enríquez, Ildefonso Armenteros-Armenteros, M. Candelaria Martín-Luis, Ramón Casillas-Ruiz, and Blas L. Valero-Garcés

Detailed reconstructions of Quaternary paleoclimate and paleoenviromental evolution of the Canary Islands have been hampered by the scarcity of long terrestrial records.  In this study, we present the results of a multiproxy approach based on sedimentological, geochemical, and magnetic susceptibility measurements in a > 40 m long new sediment cores retrieved from a paleolake located within the Vega Lagunera valley on La Laguna, Tenerife Island (Canary Archipelago). Vega Lagunera is a NE-SW oriented valley formed by fluvial erosion of the Miocene basalts of the Anaga massif and blocked by Late Pliocene and Pleistocene lavas emitted from the NE Dorsal Ridge. The 40 m long sequence represents the longest Quaternary terrestrial record in the Canary Islands. Preliminary sedimentation rates based on OSL dates in previous cores suggest a basal date of > 400 ka and a 9 m long Holocene record. The geochemical and magnetic susceptibility signatures identified a shallow lake with clastic alluvial influences during the Pleistocene, a rapid Holocene onset and dominant shallow lacustrine sedimentation since mid Holocene till drainage of the remnant lake in mid 19th century. The interplay of alluvial and lacustrine facies throughout the Holocene period and the geochemical evolution characterized the sedimentological processes linking lake and catchment dynamics, organic productivity, nutrient supply, and runoff. Age models are in progress to identify the glacial / interglacial evolution of these oceanic islands and the relative role of subtropical and mid latitude atmospheric and oceanic patterns.
This research is conducted as a part of the CCR-CAN project (TED2021-129695A-I00) supported by MCIN/AEI /10.13039/501100011033 and NextGenerationEU/ PRTR.

How to cite: Jambrina-Enríquez, M., Armenteros-Armenteros, I., Martín-Luis, M. C., Casillas-Ruiz, R., and Valero-Garcés, B. L.: A new > 400 ka paleoenvironmental and paleoclimate record from Tenerife Island (Canary Archipelago), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11700, https://doi.org/10.5194/egusphere-egu24-11700, 2024.

As a typical modern low-angle carbonate ramp sedimentary system, the shallow-marine mangrove marsh and tidal channel environments adjacent to Abu Dhabi Island contain a wide variety of allochems and diverse early-diagenetic processes. Integrating data from cores, thin sections, cathodoluminescence (CL), and scanning electron microscopy (SEM) allows for quantifying the abundance of components and providing new insights into various diagenetic events. The sediments show various skeletal and non-skeletal carbonate components, as well as a minor amount of terrigenous siliciclastic minerals (quartz and feldspar) and organic matter. The low energy within protected intertidal systems accounts for the greater abundance of carbonate mud (average 76%) in marshes, compared to tidal channels (average 3%). The high energy of tidal currents resulted in more abundant peloids and bioclasts (including bivalves, gastropods, foraminifera, algae, corals, and bryozoans) in the tidal channels. In addition, siliciclastic grains are more abundant in marshes near dredged channels. The anthropogenic activities, such as channel excavation, may increase the input of Pleistocene aeolian deposits into the modern carbonate sediments around dredged channels. Aragonite and high-Mg calcite cements with diverse crystal morphologies are slightly more common in tidal channels than in marshes. This is attributed to relatively strong hydrodynamic conditions and permeable sandy sediments, which cause higher rates of marine porewater flow. The intensity and extent of micritization and microboring of the allochems are greater in tidal channels than in marshes. The micrite envelopes of aragonite-dominated fragments are non-luminescent, whereas the micrite envelopes of bioclasts dominated by high-Mg calcite exhibit dull orange luminescence. There are no discernible differences in the elemental composition between host bioclasts and their micrite envelopes. Dolomite cement in modern sediments, which is rarely found in previous studies, mainly occurs as scattered single rhombic crystals or aggregates in the deposits from tidal channels. Energy dispersive X-ray spectrometer (EDS) data shows that patchy dolomite cements are surrounded by high-Mg microcrystalline cements. Extracellular polymeric substances (EPS) and metabolic processes of organisms may facilitate dolomite precipitation. Besides, the relatively high evaporation rate leads to an increase in the Mg/Ca ratio in pore water, thereby promoting the formation of dolomite.

How to cite: Cao, T., Alsuwaidi, M., and Morad, S.: Comparison of the sedimentary characteristics and diagenesis of modern carbonate deposits between tidal channels and mangrove marshes, Abu Dhabi, United Arab Emirates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12987, https://doi.org/10.5194/egusphere-egu24-12987, 2024.

EGU24-13240 | Posters on site | SSP3.2

Evolution of paleohydrological pathways at Nettilling Lake, Baffin Island (Nunavut, Canada) since deglaciation 

Reinhard Pienitz, Rachel Labrie, Biljana Narancic, Emilie Saulnier-Talbot, and Hanno Meyer

Paleohydrological connections and pathways within Nettilling Lake, the largest lake in the Canadian Arctic Archipelago (Baffin Island, Canada), remain poorly known. This knowledge gap hinders our ability to reliably infer past environmental changes that could provide clues to the future evolution of this region with rapid environmental change at high latitudes. The lake is currently fed by freshwaters from its catchment and drains westward into the Foxe Basin via the Koukdjuaq River. However, its early hydrological connections following the last deglaciation are thought to have been complex, when marine waters from the postglacial Tyrell Sea initially invaded the Nettilling basin from the west, followed by a brief reversal when Atlantic waters fed the basin from the east via the Cumberland Sound and Nettilling Fjord. To test this hypothesis, we investigated the lithology, sedimentology and geochemistry of various sediment archives from the easternmost sector of the lake. The multi-proxy data revealed three successive phases: an initial glaciomarine phase (8300 - 7300 cal. BP), a brackish phase (7300 - 6000 cal. BP) and a lacustrine freshwater phase (6000 - present). Our results support the hypothesis formulated by Blake (1966) of temporary hydrological connectivity between the Foxe Basin in the west, followed by a link with the Atlantic Ocean in the east via the Cumberland Sound before marine waters retreated due to differential glacio-isostatic uplift that forced the basin to be progressively occupied by the fresh waters of the present-day Nettilling Lake.

How to cite: Pienitz, R., Labrie, R., Narancic, B., Saulnier-Talbot, E., and Meyer, H.: Evolution of paleohydrological pathways at Nettilling Lake, Baffin Island (Nunavut, Canada) since deglaciation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13240, https://doi.org/10.5194/egusphere-egu24-13240, 2024.

EGU24-14931 | Orals | SSP3.2

Distribution of clay minerals offshore eastern Taiwan: New evidence of volcanic material sources and transportation processes 

Chih-Chieh Su, Jheng-Kuan Lin, Ta-Wei Hsu, Yu-Huang Chen, and Sheng-Ting Hsu

Huatung Basin, Gagua Ridge, Yaeyama Ridge, and Ryukyu Forearc Area are the main terrain characteristics offshore eastern Taiwan. Several submarine canyons are distributed in the basins and play an important role in sediment transportation. In terms of geographical location, Taiwan and Ryukyu Islands are the main sources of terrestrial materials, while Luzon Island, upstream of Kuroshio, is also one of the potential sources. Tectonic, typhoon, and monsoon activities intensively affect the flux of terrestrial materials into the ocean, which leads to the variation of sedimentation rates from 0.35 cm/a in the nearshore area of Taiwan to 0.06 cm/a in the Huatung Basin. All are much higher than the West Philippine Basin (5-7 mm/ka). Based on the differences in terrestrial material composition among Taiwan, Ryukyu, and Luzon, the study of clay mineral composition has become a potential tracer for identifying the source of sediments offshore eastern Taiwan. The controversy lies in the high content of smectite in the Huatung Basin. It was speculated that the main provenances of smectite may from eastern Taiwan (Chimei Igneous Complex) and the Ryukyu Island Arc, and the canyon systems developed off the eastern Taiwan transport terrestrial sediments over 150 km and deposited in deep Huatung Basin through turbidity currents or debris flows (Lin, 2021); or the Kuroshio transport the Luzon Arc materials into this area (Nayak et al., 2021). However, both interpretations are challenged by new comprehensive data. During the NOR1-0038A cruise in 2022, fist-sized pumice (~6 cm) was collected from the surface of the box core at the HT01 site in the Huatung Basin. Based on the mineral composition of the pumice, it is speculated that it was the product of the eruption of the submarine volcano "Fukutoku-Okanoba" in August 2020, and was brought here by currents and winds. This incident also had an impact on Taiwan's coast, with large amounts of pumice deposited in Taiwan's ports and beaches. The discovery of the "Fukutoku-Okanoba" pumice in the deep sea is of great significance to the source of volcanic ash or volcanic glass in sediments off eastern Taiwan. In addition, during the "Hakuho Maru" expedition from Dec. 13 to 23, 2023, large amounts of granite samples were first time collected by bottom dredge on the northern part of the Gagua Ridge, which may also be an important source of smectite. With the development of marine geological surveys in deep waters off ​​eastern Taiwan, our understanding of various sedimentary processes and sediment source-to-sink processes offshore eastern Taiwan continued to expand.

How to cite: Su, C.-C., Lin, J.-K., Hsu, T.-W., Chen, Y.-H., and Hsu, S.-T.: Distribution of clay minerals offshore eastern Taiwan: New evidence of volcanic material sources and transportation processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14931, https://doi.org/10.5194/egusphere-egu24-14931, 2024.

EGU24-15977 | Orals | SSP3.2 | Highlight

So Far... The Best Of Lake Van 

Ola Kwiecien, Jeremy McCormack, Nadine Pickarski, Tomaso R. R. Bontogniali, Andre Baldermann, Jiaojiao Yue, and Thomas Litt

Lake Van in Eastern Anatolia (Turkey) is the world's largest alkaline lake and the fourth largest terminal lake. A long, almost continuous, and partly annually laminated sedimentary profile, recovered during the ICDP PALEOVAN campaign in 2010 provided valuable information about the climatic, vegetation, tectonic, and volcanic history of the region over the last ca. 600 ka (Litt & Anselmetti 2014 and references therein). Individual proxy records suggest that Lake Van and its vicinity experienced significant hydroclimatic changes in concert with glacial/interglacial cycles and Dansgaard/Oeschger oscillations. The results of the original PALEOVAN project constituted an excellent framework and motivated further problem-oriented research. The last 10 years have seen a number of inspiring publications testing strengths and limitations of carbonate-based proxies in lakes and deepening our understanding of forcing mechanisms and rates of ecological changes.

Here we summarise the highlights of Lake Van research to date and offer a perspective on exciting ongoing work. Systematic analyses of the sedimentary carbonate inventory of Lake Van put the mineralogy of lacustrine carbonates in the limelight and revealed caveats of geochemical analyses on bulk samples (McCormack et al., 2018, 2019). Moreover, these studies stretched the envelope of dolomite-forming environments and early diagenetic products (McCormack & Kwiecien, 2021; McCormack et al., 2023). The established climatic context (Pickarski et al., 2015a, 2015b) and annually laminated nature of Lake Van sediments enabled the quantitative estimation of the time vegetation takes to recover after volcanic eruptions and elucidated the effect tephra deposition has on in-lake productivity (Pickarski et al., 2023).  Lake Van sediments keep on giving, with ongoing projects targeting the timing and mechanism of the lake closure and high-resolution comparisons of the impact of interglacial warming on (pan)regional hydroclimate. So perhaps 'The Best Of' is yet to come!

References

Litt & Anselmetti 2014. Lake Van deep drilling project PALEOVAN. Quaternary Science Reviews

McCormack & Kwiecien, 2021. Coeval primary and diagenetic carbonates in lacustrine sediments challenge palaeoclimate interpretations. Scientific Reports

McCormack, et al., 2019. Refining the interpretation of lacustrine carbonate isotope records: Implications of the mineralogy-specific Lake Van case study. Chemical Geology

McCormack et al., 2018. Controls on cyclic formation of Quaternary early diagenetic dolomite. Geophysical Research Letters

McCormack, et al., 2023. Hydrochemical mixingzones trigger dolomite formation in an alkaline lake. Sedimentology.

Pickarski et al., 2023. Volcanic impact on terrestrial and aquatic ecosystems in the Eastern          Mediterranean, Communications Earth & Environment

Pickarski et al., 2015b. Vegetation and environmental changes during the last interglacial in eastern Anatolia (Turkey): a new high-resolution pollen record from Lake Van. Palaeogeography, Palaeoclimatology, Palaeoecology

Pickarski et al., 2015a. Abrupt climate variability of eastern Anatolia vegetation during the last glacial. Climate of the Past

How to cite: Kwiecien, O., McCormack, J., Pickarski, N., Bontogniali, T. R. R., Baldermann, A., Yue, J., and Litt, T.: So Far... The Best Of Lake Van, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15977, https://doi.org/10.5194/egusphere-egu24-15977, 2024.

EGU24-16100 | ECS | Orals | SSP3.2

Canadian lakes are changing in response to anthropogenic disturbances: a Pan-Canadian geochemical study using micro-X-ray fluorescence sediment core-scanning. 

David R. Zilkey, Jean-Philippe Jenny, Alexandre Baud, Pierre Francus, Dermot Antoniades, and Irene Gregory-Eaves

Understanding how lake ecosystems respond to anthropogenic disturbances including mining, agriculture, deforestation, and more is often best answered with historical time series. Unfortunately, a lack of long-term monitoring data can make this difficult; paleolimnology offers an alternative, allowing for the reconstruction of past conditions using proxies from sediment records. As part of the nationally funded Canadian Lake Pulse Network, we analyzed sediment cores from 116 lakes across Canada using micro-X-ray fluorescence core-scanning (µXRF). µXRF served to generate abundance profiles for several elements (e.g., Ca, Sr, Ti, Pb, Cu, Zn), allowing for the assessment of spatiotemporal geochemical changes in Canadian lakes dating back to ~1850 AD. We calibrated µXRF core-scanning with conventional geochemical methods in a 48-lake subset and found strong correlations for numerous elements between conventional wet chemistry and µXRF-measured concentrations (Zilkey et al., accepted, Environmental Advances). We then assessed the temporal variability in sediment cores using constrained hierarchical cluster analysis and generalized additive models. Our preliminary results indicate that geochemical change demonstrates significant regional structure. On balance, lakes in eastern Canada predominantly demonstrated a temporal enrichment in metallic elements (e.g., Pb and Zn), while lakes in central and western Canada had a temporal enrichment of elements commonly associated with catchment erosion (e.g., Ti, Sr, K). Our results highlight the heterogeneity in responses across a vast landscape with diverse geological characteristics and land uses, and in the relative importance of anthropogenic disturbances shaping lake sediment geochemistry over time. Key next steps include the investigation of lakes that are distinct relative to their regional trends and the local environmental factors that might explain their contrasting response.

How to cite: Zilkey, D. R., Jenny, J.-P., Baud, A., Francus, P., Antoniades, D., and Gregory-Eaves, I.: Canadian lakes are changing in response to anthropogenic disturbances: a Pan-Canadian geochemical study using micro-X-ray fluorescence sediment core-scanning., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16100, https://doi.org/10.5194/egusphere-egu24-16100, 2024.

EGU24-16107 | ECS | Orals | SSP3.2

Multidecadal characterization of biogenic compounds and nutrients in Antarctic ice-free coastal lake sediments 

Elena Argiriadis, Luca Sorarù, Noemi Colozza, Benedetta Giannelli Moneta, Fabiana Arduini, Chiara Cavaliere, and Marco Vecchiato

Although about 98% of the Antarctic continent is covered by an ice sheet, seasonal lakes and small streams resulting from ice and snow melting are formed during the Austral summer. These ice-free areas, mainly located in coastal sites, provide a fertile environment for the development of microbial life. Isolation and extreme conditions in terms of light, temperature and nutrient availability generate peculiar ecosystems in the lake waters, characterized mainly by the presence of planktonic and/or benthonic microorganisms, especially cyanobacteria and microalgae. The water budget of coastal lakes is regulated only by melting and evaporation/sublimation, so that the organic matter from the catchment and the lake biomass is buried in sediments, which therefore represent a precious archive for the study of seasonal and interannual changes in the hydrology and primary productivity of the lakes. The high sensitivity of these environments to local climatic shifts is key to understanding how deglaciated areas may respond to larger scale changes. The lakes considered in this proposal are all located close to Terra Nova Bay, in the vicinity of the Italian research station Mario Zucchelli. Sediment samples from the same lakes were collected repeatedly in the period from 1990 to 2014 in the framework of the Italian National Antarctic Research Program (PNRA). So far, no study was ever performed on the temporal evolution of the lakes. The sediment samples analyzed here make up a 25-year long series that would encompass medium-term changes in the ecologic conditions of such sensitive environments. Samples were made available by the Antarctic Environmental Specimen Bank (BCAA, University of Genoa), associated to the Italian Antarctic National Museum.

Macroscopic changes were observed in coastal lakes in Northern Victoria Land over the last few years, regarding their extension that exhibited an overall decreasing trend that found no explanation yet. Organic markers buried in sediments could help identifying the factors that are driving the observed transformations and evaluating the sensitivity of these ecosystems to future change. Here, we investigate changes in the lipid composition through untargeted and targeted analysis of apolar and polar lipids using GC-MS and UHPLC-HR-MS/MS.

In order to complete the information gathered through the characterization of lipids, the study of nutrient availability, here performed through the detection of e.g. zinc ions in the range of 0.1-2 ppm using a paper-based printed electrochemical sensor and a miniaturized 3D printed extraction system for soil analysis, to understand if a correlation exists between the variation of nutrient content and lipid biomarkers and small to large-scale changes.

How to cite: Argiriadis, E., Sorarù, L., Colozza, N., Giannelli Moneta, B., Arduini, F., Cavaliere, C., and Vecchiato, M.: Multidecadal characterization of biogenic compounds and nutrients in Antarctic ice-free coastal lake sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16107, https://doi.org/10.5194/egusphere-egu24-16107, 2024.

EGU24-17677 | Posters on site | SSP3.2

Evolution of palaeoenvironmental and palaeoclimatic conditions recorded in Jura lakes since the Late Glacial Period 

Brahimsamba Bomou, Damien Zappa, Anne-Marie Rachoud-Schneider, Jean-Nicolas Haas, Marina Gärtner, Jorge E. Spangenberg, Vincent Bichet, and Thierry Adatte

Since the retreat of the Würm ice sheet, numerous glacial paleolakes have formed in the French and Swiss Jura. This project investigates two sites: the Amburnex Valley site (Switzerland) and the Lake Val (France). During the Late Glacial period, both sites were glacial lakes with significant accumulation of lacustrine sediments, providing a complete record of paleoclimatic and paleoenvironmental evolution.

The aim of this study is to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediment deposits over the last 15’000 years. The Amburnex core displays a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core exhibits the same lithological succession. A multiproxy approach based on palynological, mineralogical and geochemical analyses was used to characterise hydrological and climatic fluctuations, trophic levels, and the origin of organic matter. This approach was employed to reconstruct the paleoenvironmental and paleoclimatic evolution of this area. The analyses included total organic carbon (TOC), nitrogen, phosphorus and mercury contents, major and trace elements, and organic carbon isotopes.

The Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognised in the Amburnex site, by palynological analyses and carbon 14 dating. The Oldest Dryas was characterised by oligotrophic conditions, as evidenced by the very low concentrations of nitrogen and organic matter. During the warmer Bølling period, there was an enrichment in TOC, indicating the development of eutrophic conditions. Later, during the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. In the interval corresponding to the colder Younger Dryas period, new organic matter enrichments were observed. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at a regional scale.

No evidence of a tephra layer or significant mercury anomalies were found at the Amburnex site. However, significant increases in magnetic susceptibility were observed during the Allerød and Younger Dryas periods at the Amburnex site. These increases are well correlated with those recorded in other Jura lakes containing tephra layers, corresponding to the Laacher See Tephra and the Vedde Ash, respectively. A significant peak in Ptot is observed at the same level as the magnetic susceptibility peak during the Allerød period.

This peak appears to be independent of nitrogen and TOC and is related to apatite present in tephra glass in the volcanic ash deposits of the Laacher See Tephra.

How to cite: Bomou, B., Zappa, D., Rachoud-Schneider, A.-M., Haas, J.-N., Gärtner, M., Spangenberg, J. E., Bichet, V., and Adatte, T.: Evolution of palaeoenvironmental and palaeoclimatic conditions recorded in Jura lakes since the Late Glacial Period, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17677, https://doi.org/10.5194/egusphere-egu24-17677, 2024.

EGU24-19071 | ECS | Orals | SSP3.2

Brevetoxin Preservation in Marine Sediments from Amber Jack Blue Hole 

Angie Ruiz, Joanne Muller, Puspa Adhikari, Adam Catasus, Jeffrey Donnelly, and Peter J. van Hengstum

In Southwest Florida (SWFL) red tide (Karenia brevis) is a natural hazard and produces potent toxins, to both human and marine life, known as brevetoxins. Red tide, a microscopic alga species, is responsible for environmental, economic, and human health problems in this region. However, our understanding of natural and anthropogenic drivers of red tide are still poorly understood. This study endeavors to reconstruct brevtoxins records in marine sediments with the purpose to better understand present day blooms compared to historic red tide blooms in SWFL. This may be best achieved by looking at sediment cores from blue holes along the West Florida shelf. Blue Holes are natural geologic formations originating on land, as sink holes, which filled over time as global sea level rose. Generally, anoxic conditions found in blue holes provide excellent preservation of long geologic records and provide a unique opportunity to study brevetoxin as biomarkers in sediment cores. In 2023, sediment cores were collected from the Amber Jack Blue Hole off the coast of SWFL. The sediment cores were sliced at 1 cm intervals, and solvent extracted for the analysis of brevetoxins using a LC-MS/MS. The sediments were also analyzed for grain size analysis and scanned using x-ray. This study examines the vertical preservation depth of Karenia brevis and analyzes historic red tide events preserved within the Amber Jack blue hole sediments. This research provides the first opportunity to study red tide chemical biomarkers in high resolution blue hole sediment cores.

How to cite: Ruiz, A., Muller, J., Adhikari, P., Catasus, A., Donnelly, J., and Hengstum, P. J. V.: Brevetoxin Preservation in Marine Sediments from Amber Jack Blue Hole, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19071, https://doi.org/10.5194/egusphere-egu24-19071, 2024.

The Gosau Group is a terrestrial to deep-water succession formed on the northern margin of the Austroalpine microplate during the early stages of Alpine orogenesis. The sedimentary characteristics of the Gosau Group reflect the paleoenvironment of the Northern Calcareous Alps from the Late Cretaceous to the Eocene. It has been divided into the Upper Gosau Subgroup and the Lower Gosau Subgroup based on the sedimentary facies. The Lower Gosau Subgroup indicates a transitional environment from terrestrial to shallow water. It has been subdivided into the Lower Gosau Subgroup, composed of fluvial, lacustrine to shallow marine sediments during the Turonian to Santonian-Campanian, and the Upper Gosau Subgroup, characterized by deep-water succession up to Eocene in age. The shallow to deep environmental transition was derived from the subsidence of the continental margin, associated with the subduction of the South Penninic Ocean. However, details of the Late Cretaceous environmental variations have not been understood enough for reconstructing the formation of the Gosau Group. This study investigates environmental signals by analyzing coal-bearing deposits in the Lower Gosau Subgroup. We selected seven outcrop sites including coal seams ranging from the Turonian to Campanian in Austria, which showed fluvial and/or lacustrine depositional settings, and collected fourteen coal samples. Based on the industrial analysis and vitrinite reflectance, the samples were evaluated as low to medium ranks. Our results indicate a wide range of variations in silicon oxides, organic matters, and clay contents that are related to changes in depositional environment and water energy. These correspond to occasional occurrences of pyrite and carbonates, which could have been caused by interaction with seawater. Changes in the marcel contents also could be influenced by varying water level. Our study suggests that the coal-bearing sediments of the Lower Gosau Subgroup in Austria were deposited in unsteady environments and occasionally affected by seawater, which might correspond to the short-term sea-level fluctuations.

How to cite: Xiang, X., Lee, E. Y., and Wagreich, M.: Paleoenvironmental variations in the coal-bearing deposits of the Lower Gosau Subgroup (Turonian to Campanian) in the Northern Calcareous Alps, Austria., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19509, https://doi.org/10.5194/egusphere-egu24-19509, 2024.

EGU24-19766 | ECS | Posters virtual | SSP3.2

The reasons for dark patches on sediments related to decay at still water, burrow canals, and vertical carrier flows 

Dursun Acar, Furkan Hoşer, Nurettin Yakupoğlu, İpek Olsun, Dila Doğa Dokgöz, and Demet Biltekin

At the sediment surfaces, the detection of dark patch-type color changes is very easy which are mostly related to Carbon, Hydrogen Sulfur, and Iron-Sulfur conversion diffusions. After the decay of settled animal and Plant remains interact with its sitting clay during sedimentation at still waters. Some of decomposing remnant particules move away  such as mostly  chitin (long fragmentation time and ligthweigth ) with drifter currents time by time available. Dark patches are visible as horizontal centimeter scale to a vertical depth of a few mm. Dispersion of the dark color is limited with result of diffused materials as nutrient and consumed oxygen from clastics or oxides by microorganism populations (increse and decrease of population) . Second type  dark patch generations are possible around bioturbation traces at sediments such as a burrow or canal-type gaps by living worms or burrowed larvas (water - clay tank experiment). Daily physical frictional movements of larvae helped to anoxic suspension displacements at depth of housing gaps to the sediment surface (at the water - clay experiment and its sediment layer setup sequence is oxic layer on top and anoxic clay layer at the bottom).

Regional anoxia of  bacteries as remnant of host is possible after larval displacement from the vertical canal.   In the low oxygen water sediment tank experiment we observed first and second type dark patch generations. In our oil covered oxygen isolated high anoxia experiment with flies and ants, the first type of dark patches in anoxia conditions was generated and as result especially insects provided well dark patches without any insitu remnants because chitin parts slowly drifted. (chitin solubility or fragmentation time very long with complex biological processes at salty water and oil  and fast with acetic acid). The observation was experienced with randomly natural falls of flies and wingy ants into the experiment fluids. Type 3, texture type dark patch dispersions at sediment cores associated to microorganism life in sediment clay. The initial stages of dark color patches at the clay layer were more visible after increasing  temperature and decreasing pressure of the environment around growing pressure gap of hydrogen sulfur gas after the stop of diffused oxygen support with pore water displacement. Developing stages of the third type; tubular form micro mud volcano type dark patch structures occurred at the water-sediment tank experiment. All type  patch is very important for micro XRF measurements because actual element readings change by carbon and other enriched contents, especially non-oxidized carbon's high energy X-ray beam suppression. For high precise measurements such as providing micro XRF elemental data or climate , paleo-environment interpretation, you need to choose parallel measurement way without dark patches because inorganic sediment material-based information gets the wrong clues.

How to cite: Acar, D., Hoşer, F., Yakupoğlu, N., Olsun, İ., Dokgöz, D. D., and Biltekin, D.: The reasons for dark patches on sediments related to decay at still water, burrow canals, and vertical carrier flows, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19766, https://doi.org/10.5194/egusphere-egu24-19766, 2024.

EGU24-20515 | Orals | SSP3.2 | Highlight

Unraveling Temporal Complexities in Lake Science through Sediment Records and Process-Based Models  

Jean-Philippe Jenny, Laura M. V. Soares, Theo Mazure, and Olivia Desgué-Itier

The expected alterations in nutrient levels and climate conditions are projected to significantly reduce oxygen concentrations in numerous stratified lakes globally. Nevertheless, the exact duration, timing, and consequences on lake oxygen over decadal to centennial scales remain uncertain due to the limited availability of long-term monitoring data. In this study, we introduce an innovative model-data assimilation approach that integrates 150 years of limnological and paleolimnological data to assess the human-induced impact and future outlook of dissolved oxygen (DO) conditions in the renowned Lake Geneva under various climate scenarios. Pluri-decadal series of limnological data monthly collected by the French Observatoire des LAcs (OLA database) were used to calibrate and validate the model. In addition, model outputs were further validated with published paleolimnological records for the past 170 years. Results of the calibration procedure show that the GLM-AED2 model accurately predicts the magnitude and seasonal dynamics of the state variables with goodness-of-fit metrics under the literature range (e.g. RMSE = 0.96 mg L–1 and RRMSE = 25% for dissolved oxygen; RMSE = 6.53 ug L–1 and RRMSE = 37% for chlorophyll-a, both in the epilimnion). Our analysis reveals that over centennial timescales, it was eutrophication combined with reduced winter mixing that initiated prolonged and severe bottom-water hypoxia. Conversely, examining the recent years and projecting forward to 2100, climate change is poised to be the primary driver of hypoxia in Lake Geneva and analogous lakes, even with decreased phosphorus concentrations. Our results strongly advocate for the necessity of reducing local phosphorus inputs in stratified lakes to avert deoxygenation. However, it is essential to acknowledge that doing so may also limit lake productivity due to nutrient availability.

How to cite: Jenny, J.-P., Soares, L. M. V., Mazure, T., and Desgué-Itier, O.: Unraveling Temporal Complexities in Lake Science through Sediment Records and Process-Based Models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20515, https://doi.org/10.5194/egusphere-egu24-20515, 2024.

EGU24-22570 | ECS | Orals | SSP3.2

Fossil Fluvio-Lacustrine System of the Southern Grande Terre of New Caledonia : Paleo-environmental Archives and Dynamics of Trace METALlic Elements (TME) 

Jean-Baptiste Parmentier, France Pattier, Maximilien Mathian, Virginie Gaullier, Peggy Gunkel-Grillon, Pierre Maurizot, Nicolas Tribovillard, Cyril Marchand, Olivier Cohen, Emmanuel Blaise, Alain Zanella, and Nell Devillers

Located in the south-west Pacific, New Caledonia is an archipelago with a complex geodynamic history. Grande Terre, the main island, is covered by more than 25% of regolith developed on ultramafic rocks. These peridotites, naturally enriched in metallic elements (Fe, Al, Ni, Co, Cr), constitute most of the southern part of New Caledonia. Since approximately 27 Ma, these rocks have undergone weathering (under a humid tropical climate) and erosion. This combination has led to the formation of the fluvio-lacustrine system, by accumulation of sediments eroded from local summits in depressions and valleys.

The distribution of the fossil fluvio-lacustrine system in New Caledonia has been mapped by Folcher N. (2016). The sedimentary filling of this system is essentially of fluvial origin, with rare lacustrine occurrences. Its structure is complex and some sedimentary levels show abnormally high accumulations of Trace Metallic Elements (Ni, Co, Cr). Thus, the METAL FLAP thesis project aims to understand how the geodynamic history, paleoenvironmental evolution, and diagenetic processes within the fluvio lacustrine formation influence the dynamics of metallic elements and their potential transfer to the modern fluviatile system?

In one of the sub-basins of the system (the basin of the pirogue river), the relationships between geochemistry and structures have been studied at the edges of two types of objects: horizontal indurated beds and vertical ferruginous partitions. The first results suggest that these two types of structures, which have different formation origins, strongly impact the distribution of elements in sediments (enrichment in Cr, depletion in Fe, etc.). The vertical partitions are thought to be related to fluid circulation in basin fractures, while the formation of horizontal indurated layers is believed to originate from fluctuations in groundwater levels. The quantification of the contribution of each phenomenon to the dynamics of elements is still poorly defined but constitutes one of the major focuses of this study.

Furthermore, a detailed analysis of the system’s architecture and a thorough sediment characterization, coupled with the study of the few fossils present in the formation, shed light on the paleoenvironmental history of the region during deposition. This also provides assistance in understanding the geological processes affecting the formation of the fluvio-lacustrine system, as well as the dynamics of metallic elements in the land-sea continuum. This fossil continental system in the southern region is one of the least studied formations in the area, despite the wealth of information it holds about the geodynamic history of New Caledonia during the last post-obduction cycle.

How to cite: Parmentier, J.-B., Pattier, F., Mathian, M., Gaullier, V., Gunkel-Grillon, P., Maurizot, P., Tribovillard, N., Marchand, C., Cohen, O., Blaise, E., Zanella, A., and Devillers, N.: Fossil Fluvio-Lacustrine System of the Southern Grande Terre of New Caledonia : Paleo-environmental Archives and Dynamics of Trace METALlic Elements (TME), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22570, https://doi.org/10.5194/egusphere-egu24-22570, 2024.

Large submarine landslides are a global concern as they can trigger tsunamis with no clear precursors. While geological characterization of submarine landslides remains a challenge to many areas worldwide, the availability of global bathymetric datasets and spatial analysis tools has led to progress in mapping these submarine geomorphological features. Morphological and statistical analyses of submarine landslides and their attributes enable the identification of regions susceptible to large submarine failures and covariates that are good predictors of submarine landslide volume. This study identifies significant clusters of large submarine landslides mapped (n=1214) in the Negros–Sulu Trench System by testing the spatial dependence of volume using global Moran’s I and Getis-Ord (Gi*) statistic. This study further explores a spatial model that best elucidates the distribution of submarine landslide volume. Global Moran’s I suggests significant positive spatial autocorrelation, while Gi* statistic reveals local clustering of large-volume submarine landslides, where the densest clustering occurs offshore of southern Panay Island. Among the 18 spatial regression models, the (1) univariate spatial Durbin, (2) nested, and (3) spatial Durbin error with the maximum slope as the predictor have the lowest Akaike information criterion (AIC) of 2056.1, 2057.0, and 2057.8, respectively. The spatial regression models also revealed that mean depth is a poor predictor of submarine landslide volume. Log likelihood-ratio test suggests a simpler option of the nested model. The spatial Durbin error model better represents the underlying local heterogeneities such as sediment flux and subduction processes in triggering submarine landslides than the global spillover effects of the spatial Durbin model. Furthermore, this study highlights the dominant role of slope and tectonic processes that induce oversteepening, triggering large submarine landslides that may induce damaging tsunamis. The identified offshore areas with significant clustering of large submarine landslides are valuable information for offshore geophysical surveys and tsunami hazard assessment in the region.

How to cite: Nawanao, L. and Ramos, N.: Spatial Regression Modeling and Distribution of Submarine Landslides in the Negros–Sulu Trench System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22, https://doi.org/10.5194/egusphere-egu24-22, 2024.

The Ordovician karst fracture-cave reservoir in Tahe oilfield has strong heterogeneity, and palaeogeomorphology, fault and fracture play important roles in the development of the complexity of the fracture-cave reservoir. Based on rich geological and geophysical data, the influence of faults on the karst reservoir development in carbonatite under different palaeogeomorphic conditions are analyzed through the interpretation of faults and the activity of internal faults in carbonate rocks in different periods, combined with palaeokarst environment and karst products. 
The results show that there are not only strike-slip faults but also an NNE-thrust fault in the sixth and seventh districts of Tahe Oilfield, which control the direction of long-axis anticline in the center of the study area. The anticline becomes an important watershed and most of the surface gullies develop along suitable faults from the top of the anticline to lower areas. According to the karst geomorphology, water system and fracture-cave distribution, landforms are divided into three types: hoodoo-upland, karst depression and karst basin. In the hoodoo-upland, the fracture networks around the faults are dissolved and small and medium-sized fractures develop, and the reservoirs have low filling degree and good performance. In the karst depression, the landforms are transformed by strong water erosion and karst dissolution. The underground rivers and the palaeogeomorphic gullies controlled by high-angle strike-slip faults are relatively straight, while the others controlled by low-angle faults are tortuous. Unfilled caves and intergranular pores in cave fillings are the main reservoir spaces. In karst basin, the Ordovician soluble limestone is covered by stucco deposits, which greatly weakens the karstification. The fractures and caves can develop only along the faults and fractures at a very deep depth. The spatial structure, connectivity, porosity and permeability are complicated. The main reservoir types are fractures, fracture-cave and isolated caves. The filling types are fault karst breccia, giant crystal chemical filling or no filling. Therefore, faults affect the development of reservoir types and fillings under different geomorphology and karst water conditions, which has important guiding significance for the accurate exploration and development of carbonate fracture-cave reservoirs. 

How to cite: Zhang, X. and Jin, Q.: The influence of faults on the development of canbonate karst reservoir in main area of tahe oilfield and its significance in petroleum geology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-67, https://doi.org/10.5194/egusphere-egu24-67, 2024.

EGU24-648 | ECS | Orals | GM9.6 | Highlight

Unveiling the Multifaceted Hazard Risks of Volcanic Eruptions: The case of Kolumbo submarine volcano 

Anna Katsigera, Paraskevi Nomikou, Kosmas Pavlopoulos, Paraskevi Polymenakou, Konstantinos Karantzalos, Aggelos Mallios, Sergio Simone Scire Scapuzzo, Andrea Luca Rizzo, Gianluca Lazaro, Manfredi Longo, Walter D'Alessandro, Fausto Grassa, Lars-Eric Heimbürger-Boavida, Valsamis Ntouskos, Christos Antoniou, and Sotiris Spanos

Volcanic eruptions stand as formidable threats to adjacent communities, unleashing a spectrum of hazards such as earthquakes, tsunamis, pyroclastic flows, and toxic gases. The imperative for proactive management of volcanic risks cannot be overstated, particularly in densely populated areas where the potential for widespread devastation looms large. Kolumbo, an active submerged volcano located approximately 7 kilometers northeast of Santorini Island in Greece at 500m depth, serves a pertinent case. Its historical record is marred by an eruption in 1650 AD which triggered a relentless tsunami. The aftermath witnessed havoc on neighboring islands, coupled with casualties stemming from noxious gases in Santorini. Eyewitness accounts mention maximum water run-up heights of 20m on the southern coast of Ios, a staggering 240m inundation on Sikinos, and a disconcerting flooding of up to 2km² of land on the eastern coast of Santorini.

Recent studies suggest that a potential future explosive eruption of Kolumbo poses a substantial hazard to the northern and eastern coasts of Santorini. Unfortunately, the absence of a concrete management protocol, leaves these areas vulnerable to an impending threat that demands immediate attention. Therefore, it is recommended that a comprehensive approach be adopted, involving scientific research (active monitoring, hazard maps), community engagement, preparedness planning with government agencies, and the development of timely response strategies to reduce the associated risks, prevent casualties, and mitigate the consequences on the region's economy and infrastructure. Our team has multidisciplinary data from past oceanographic expeditions that will help us to understand Kolumbo’s behavior. These include a) High-resolution multibeam bathymetry data and optical data., b) a dense network of sub-seafloor seismic reflection profiles, c) a series of the seafloor and sub-seafloor samples of microbial mat and sediments, d) CTD data, e) several polymetallic (Au, Ag, As, Sb, Pb, Hg, Mo, Zn, Cu, Tl) CO2 diffuser chimney samples and f) tephra in marine sediment cores. Despite the current knowledge that we managed to obtain, monitoring is needed to efficiently assess potential hazards and create early warning systems and management protocols for an imminent eruption from Kolumbo. In the current context, advanced sensors have been deployed to monitor Kolumbo's active hydrothermal field as part of the SANTORY project. The SANTORY project aims to create innovative communication tools and establish interregional monitoring protocols, providing the scientific community, policymakers, and stakeholders with the means to assess hazard warning codes effectively.

How to cite: Katsigera, A., Nomikou, P., Pavlopoulos, K., Polymenakou, P., Karantzalos, K., Mallios, A., Scire Scapuzzo, S. S., Rizzo, A. L., Lazaro, G., Longo, M., D'Alessandro, W., Grassa, F., Heimbürger-Boavida, L.-E., Ntouskos, V., Antoniou, C., and Spanos, S.: Unveiling the Multifaceted Hazard Risks of Volcanic Eruptions: The case of Kolumbo submarine volcano, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-648, https://doi.org/10.5194/egusphere-egu24-648, 2024.

Lake Sapanca is located in the Eastern Marmara region of Turkiye and formed as a tectonic lake by the right-lateral strike slip North Anatolian Fault (NAF). Located 33 m above sea level, this tectonic lake has a length of 16 km in the east-west direction and 5 km in the north-south direction. The area in which the lake is located is on the Izmit-Sapanca Corridor, which is bordered by the segments of the northern branch of the NAF, between the Samanlı Mountains to the south and the Kocaeli Peneplain to the north. Multibeam bathymetry and high-resolution seismic data were acquired in the lake as a part of a TUBITAK project (Project No: 117Y130) in August 2018 to determine the structural and stratigraphic elements of the lake. Many pockmark structures, as well as lineaments related to the NAF, were observed on multibeam maps giving cm-scale resolution on the lake bottom. Thus, the effects of NAF in the lake can be better determined depending on the geometrical properties of the pockmarks, more than 300 in number, which are formed due to gas or fluid outflows from the lake-bottom, and their distribution in certain parts of the lake. In order to determine these features of pockmarks, semi-automatic approaches of QGIS and ARCGIS software programs were used and it was observed that the pockmark distribution increased along the lineament direction of the NAF and in the northeast of the lake. Moreover, we conclude that, the consistent orientation of the individual pockmarks may indicate that all pockmarks were formed in a relatively short period of time or that the bottom current regime in the lake has been effective for a long time. 

How to cite: Sönmez, E. and Kurt, H.: An Example of Determining Fault Properties from Morphological Analysis of Pockmarks is Sapanca Lake, Located on the North Anatolian Fault, Turkiye, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-997, https://doi.org/10.5194/egusphere-egu24-997, 2024.

EGU24-1121 | ECS | Orals | GM9.6

Dynamic changes in depositional patterns and glaciotectonic deformations revealed by high-resolution 3D seismic data in the Northern North Sea. 

Bartosz Kurjanski, Nick Lee, Allan MacKay, Bill Powell, and Julien Oukili

During the Last Glacial Maximum (LGM), the British-Irish ice sheet is known to have been coalescent with the Fennoscandian ice sheet. Some models indicate that this might have been rather short-lived, whereas other reconstructions indicate an early and long-lasting coalescence of the ice sheets which, together reached the Northern North Sea continental shelf edge around 27,000 years ago. To date, the lack of empirical data, in the form of boreholes or high and ultra-high resolution seismic data has hindered efforts to validate the reconstructions and identify ice flow directions, drainage patterns, and chronology. Little is also known about the nature of the deglaciation and unzipping of the two ice sheets  which would  have likely comprised  multiple ice re-advances, stillstands, and retreats as well as an unknown duration of ice grounding which, based on experience, will result in complex and heterogeneous stratigraphy, vertically and horizontally

In this study, a unique 3D seismic dataset with bin spacing of 3.125m x 3.125m and a frequency range of ~10-160Hz will be used to reconstruct the depositional history and sequence of events in the shallow subsurface(~ 200m below sea bed) including but not limited to processes responsible for tunnel valley formation and infill, large scale glaciotectonic deformation or postglacial deposition. This will be juxtaposed against known paraglacial reconstructions to propose preliminary timing of events. Implications for offshore infrastructure projects will be subsequently discussed in the context of ground conditions identified over the site.

How to cite: Kurjanski, B., Lee, N., MacKay, A., Powell, B., and Oukili, J.: Dynamic changes in depositional patterns and glaciotectonic deformations revealed by high-resolution 3D seismic data in the Northern North Sea., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1121, https://doi.org/10.5194/egusphere-egu24-1121, 2024.

EGU24-2937 | ECS | Posters on site | GM9.6

Fine-scale seafloor bedform morphology along a slope-confined submarine canyon in the Northern South China Sea 

Yue Sun, Dawei Wang, Miquel Canals, Tiago M Alves, and Fanchang Zeng

Bedforms are widely distributed within deep-water submarine canyons, which are usually documented by vessel-mounted sensors. Yet, fine-scale geomorphology and shallow structures of bedforms in deep-water submarine canyons remain poorly documented, and understood, because of the insufficient resolution of vessel-based data. This study utilizes high-resolution autonomous underwater vehicle (AUV) dataset combined with intermediate seismic reflection profile and sediment cores to analyze bedform sets along a slope-confined submarine canyon (canyon C14) from the northern South China Sea. A train of crescent-shaped to inverted U-shaped axial steps in plan view are aligned downstream along the canyon thalweg from upper course to lower course. Based on comprehensive analysis of morphologic features, subsurface structures, flow estimates, and potential origins, these steps are likely to be cyclic steps created by supercritical turbidity currents. Sediment cores mainly comprised by silt with minor sand contents further suggesting the shallow canyon sediments probably deposited by diluted turbidity currents. Axial steps (S1-S4) with lower asymmetry and wavelengths in the upper course show an erosional truncation and horizontal to sub-horizontal reflectors draping on the lee side and stoss side, respectively, illustrating the erosional-depositional cyclic steps formed by more confined flow with higher erosion capability due to the narrow canyon (average width of 3.5 km) and steep slope gradient (average of 2.36°). Leaving transition segment, the less confined flow passing through lower course can be subject to wider canyon (average width of 5.5 km) and gently slope gradient (average of 1.2°) that increases the asymmetry and wavelengths of axial steps (S5-S7) and leave backset bed deposits on the stoss sides, probably pointing to the depositional cyclic steps with higher aggradation. Sediment filling, almost padding each cyclic step-associated scour, indicate that the previous-formed bedforms can be reworked by subsequent gravity flows deposits which mainly consist of slope failures-associated mass-transport deposits and turbidity currents deposits. Near the lower end of the canyon, reduction in flow velocity caused by further decrease of slope gradient (average of 1.05°) as the key factor leading to the shift from cyclic steps to furrows, but always under supercritical flow conditions. In this context, a sector of axial channel probably promotes the re-convergence of turbidity currents, resulting in the erosion of fine-grained cohesive deposits on the canyon floor, to form linear furrows within the axial channel. This work provides a good opportunity to investigate the fine-scale morphological features and shallow structures of bedforms in deep-water submarine canyon, and understand their evolution under the influence of canyon topography.

How to cite: Sun, Y., Wang, D., Canals, M., Alves, T. M., and Zeng, F.: Fine-scale seafloor bedform morphology along a slope-confined submarine canyon in the Northern South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2937, https://doi.org/10.5194/egusphere-egu24-2937, 2024.

EGU24-5688 | ECS | Orals | GM9.6

Turbulence intermittency effects on initiation threshold of sediment motion in natural waters  

Renzhi Li, Yaping Wang, and Shu Gao

The initiation threshold of sediment motion, a key component in quantifying sediment transport, has potential link to intermittent turbulence bursts. Here, we elaborated in situ experiments on coastal sea bottom covered with cohesive sediments, to extract intermittency parameters. For the first time, waiting time between turbulence bursts was utilized to capture the occurrence of sediment initiation events. A relationship found between waiting time and shear stress reveals the different intermittency feature of sediment flux time series before and after reaching the threshold, which can be used to determine the initiation threshold of sediment motion. Multi-site results demonstrate the limitations of traditional empirical formulae for fine-grained sediments, where cohesiveness becomes more pronounced as grain size decreases and the deviation can reach 600%. The empirical formula was modified using grain size, and the modified calculations were in good agreement with observed values, which will greatly assist in sediment transport and geomorphology model predictions.

How to cite: Li, R., Wang, Y., and Gao, S.: Turbulence intermittency effects on initiation threshold of sediment motion in natural waters , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5688, https://doi.org/10.5194/egusphere-egu24-5688, 2024.

EGU24-5760 | Posters on site | GM9.6

Automatic pockmark detection in the Norwegian Channel  

Dag Ottesen and Markus Diesing

Pockmarks are widely distributed in areas with fine-grained layered sediments. We utilised a large multibeam bathymetric dataset covering an area of c. 15,000 km2 of the Norwegian Channel (NC), the western slope and adjacent shelf outside western Norway. Pockmarks were extracted from the bathymetry data with two approaches: by identifying local minima in the bathymetry and by mapping landform types based on geomorphons. While the former approach yielded a point dataset indicating local minimum depths, the latter approach allowed to outline potential pockmarks as polygons based on the landform types of pits and valleys. To increase the reliability of the classification, only pockmark polygons that contained at least one local minimum were subsequently retained. This mainly removed artefacts at the edges of the classified area. Likewise, only those local minima that fell inside a pockmark polygon were retained. Finally, a limited number (<1%) of polygons incorrectly mapped as pockmarks was manually removed. 

Approximately 65,000 pockmarks were automatically detected inside the study area. The highest pockmark densities were located in the western slope of the NC. Here, an extensive pattern of elongated pockmarks was found, indicating strong bottom currents over the area.  

The study area is located in the Viking Graben area with the Øygarden Fault zone to the east. The stratigraphy comprises dipping Mesozoic and Cenozoic clastic sediments over a Paleozoic or crystalline basement. On top of these layers an Upper Regional Unconformity (URU) appears. Above the URU, which forms the base of the NC, flat lying units of glacial (till) and marine sediments are found. Above these layers of late-glacial and Holocene sediments up to a few tens of metres appear.   

The gigantic Troll hydrocarbon field is located in the northern part of the study area, and several studies have documented that there is no active fluid seepage today, so the pockmarks are thought to have been formed by gas hydrate dissociation under/after the last deglaciation. 

How to cite: Ottesen, D. and Diesing, M.: Automatic pockmark detection in the Norwegian Channel , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5760, https://doi.org/10.5194/egusphere-egu24-5760, 2024.

Diamantina Trench in the southeast Indian Ocean is one of the less unexplored hadal trenches (> 6000 m) of our planet, which develops the second deepest point (Dordrecht Deep, ca. 7019 m depth) in the Indian Ocean. Humans did not visit its ocean floor until the Chinese submersible Fendouzhe reached its deepest point in January 2023. This expedition collected high-resolution multibeam sonar bathymetry data covering about 3000 nautical miles and conducted 28 scientific dives with high-resolution videos and push core sediments of the upper seafloor (max. 40 cm) at a wide range of submarine geomorphology. This study combines these materials to fully assess the morphological variability of the trench and the causative factors and processes determining such characteristics.

Bathymetry data indicate a rugged and complex landscape with various seamounts and debris deposits in the Diamantina Trench which could be classified into three sections. Bounded by the Broken Ridge to the north, the western section contains a series of basins and gorges, as well as parallel intruded ridges (WNW striking). The eastern section shows deeper and steeper slopes compared to the western section. The transitional area of the two sections (the Dordrecht Deep area, 270 km2) is the deepest part of the trench.

Four push core sediment profiles were analyzed from the most west and east locations, the Dordrecht Deep area, and the western trend with foraminifera oozes. Layers of foraminifera and calcareous nannofossil oozes occur at the western section, whereas brownish pelagic sediments with occasionally coarse-grained Fe-Mn nodules develop at the eastern section. The preliminary results of total carbon (TC) and total nitrogen (TN) suggest distinct differences among and within profiles. TC values reach 12% in foraminifera oozes and less than 1.2% in the pelagic sediments. TC values decrease rapidly at the upper 10 cm and remain low (0.1–0.2%) at the lower part in the profiles from the eastern section and Dordrecht Deep area. An analogous trend applies to the TN graphs. The sediment profile from the western section, however, shows decreasing TC and TN values within depth.

This research provides the first knowledge of the highly spatial heterogeneity of submarine geomorphological characteristics and sediment dynamics in the Diamantina Trench. The ongoing measurements of organic matter content, carbon isotope, and grain size from different topographic locations with the potential of dating methods (e.g., 14C and paleontological data) will further aid in reconstructing the spatial variations of paleoenvironmental changes and organic cycling process, as well as in understanding the relationship with tectonic activities and catastrophic events in hadal zones.

How to cite: Yang, X., Huang, X., Zhou, P., and Peng, X.: Submarine geomorphology of the Diamantina Trench (SE Indian Ocean) based on high-resolution multibeam sonar bathymetry and push core sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5882, https://doi.org/10.5194/egusphere-egu24-5882, 2024.

Submarine braided channels, driven by turbidity currents, have been revealed on several deep-sea fans, displaying similar morphological features to fluvial braided rivers. Past experimental studies on submarine braided channels have shown that active braiding intensity (BIA) is proportional to fixed confinement width, dimensionless stream power (ω*) and dimensionless sediment-stream power (ω**). However, the field-scale submarine braided channels may not restrict to a fixed confinement width (B); instead, the confinement shape often exhibits gradual widening or narrowing. In this study, we use physical experiments to investigate the influence of confinement shapes and inflow-to-sediment discharge ratios (Qin/Qs) on the evolution of submarine braided channels. In the experiments, three confinement shapes were simulated: diamond, hourglass, and reversed trapezoid. The experimental results show that the BIA is strongly proportional to the varying confinement width, i.e., increasing confinement width facilitates the degree of braiding; decreasing confinement width suppresses the degree of braiding. The measured BIA is proportional to both the ω* and ω**. Additionally, increasing Qin/Qs causes a slightly decrease of BIA. The measured active width (Wa) is proportional to the bulk change (Vbulk). These relations all agree with the published trends of both fluvial and submarine braided channels. For the geometric properties of sandbars, the measured sandbar aspect ratio and sandbar compactness ratio remain constant regardless the change of confinement shape or Qin/Qs. Finally, the experimental results may aid our understanding to the morphological evolution of submarine braided channels and provide insights to the stacking patterns of hydrocarbon reservoirs.

 

Keywords: submarine braided channels, turbidity current, physical experiment, confinement shape, active braiding intensity

How to cite: Tsai, Y.-T. and Lai, S. Y. J.: Submarine braided channels in response to channel confinement shapes and inflow-to-sediment discharge ratios: Insights from physical experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6154, https://doi.org/10.5194/egusphere-egu24-6154, 2024.

EGU24-7144 | Posters on site | GM9.6

Submerged aeolian dunes on the flat-topped Dokdo seamount in the East (Japan) Sea, Korea 

Jang-Jun Bahk, Soo-Jin Kim, Chang Hwan Kim, Young Kwan Sohn, and Chan Hong Park

This study examines subaqueous dunes located on the southern periphery of the flat top of Dokdo Seamount at water depths from 120 to 170 meters, where the present ocean currents are incapable of generating such large bedforms. To determine their origin, we conducted a comprehensive analysis of the geomorphic characteristics using high-resolution multi-beam bathymetry and the grain-size characteristics of seafloor sediments. The analysis of the dune spacing in relation to height, as well as their migration and growth pattern, indicates that the Dokdo subaqueous dunes (DSDs) originally formed as aeolian dunes. These were shaped by northerly winter winds that carried sands from the wave erosion surfaces on the northern part of the flat top. The DSDs are believed to have transitioned to their current submerged state without experiencing significant erosion or reactivation. Considering the variations in the Plio-Pleistocene global mean sea level, we estimate the possible subsidence rate of the flat top to be approximately 130 m/myrs, aligning with the conditions required for the formation of DSDs. This study highlights how relict features such as submerged aeolian dunes on seamount summits can be utilized to precisely estimate the subsidence rate of oceanic volcanoes.

How to cite: Bahk, J.-J., Kim, S.-J., Kim, C. H., Sohn, Y. K., and Park, C. H.: Submerged aeolian dunes on the flat-topped Dokdo seamount in the East (Japan) Sea, Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7144, https://doi.org/10.5194/egusphere-egu24-7144, 2024.

 This study presents a detailed analysis of grain-size distributions of closely spaced surface sediment samples from the eastern continental margin of the Korean Peninsula off Gangneung and Donghae. This region is characterized by a wave-dominated beach, narrow shelf less than 10 km wide, and slopes with varying gradients ranging from 0.7 to 6.3 degrees. Spatial variations in dominant sediment transport modes were identified using end-member analysis (EMA) of the grain-size distributions.

 The EMA revealed five distinct end-member distributions (EMD) with mean grain sizes of 221.2 μm (EMD1), 89.2 μm (EMD2), 52.4 μm (EMD3), 22.0 μm (EMD4), and 4.5 μm (EMD5), respectively. EMD1, is significant only at two shallow sample sites near the coast, adjacent to the exposed rocky seafloor, indicating an origin from a relict sand during the post-glacial transgression. EMD2 predominates on the shelf and upper slope (40 to 150 m water depths) along the margin, particularly near a local river mouth, suggesting bedload transport of riverine sand by longshore drifts or episodic storm surges. EMD3, potentially representing coarser suspended load, dominates the upper middle slope (200 to 400 m water depths) where the slope gradient is relatively constant, and the isobaths generally run parallel to the shoreline about 15 km apart. EMD4, potentially representing finer suspended load, prevails in the deeper middle slope (400 to 800 m water depths) characterized by varying morphology: narrower and relatively steeper in the northern part, and wider and gentler in the southern part of the margin. The higher proportions of EMD4 extend far offshore in the wider and gentler southern part more than about 35 km, whereas they are limited to within 30 km from the shoreline at the base of the steeper and narrower slope in the northern part. The morphologically controlled EMD4 distributions suggest that a density current was responsible for the offshore fine-grained sediment transport in this margin, rather than diffusion or advection by ocean currents. Finally, the finest EMD5, predominates in the deepest part of the study area, showing no significant further offshore variations, and is interpreted to represent aeolian dust from the Asian inland.

How to cite: Sim, G., Bahk, J.-J., Jang, J., Kim, H., Jeong, J., and Um, I.-K.: Distinguishing sediment transport modes in the eastern continental margin of the Korean Peninsula through end-member analysis of surface sediment grain-size distributions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7149, https://doi.org/10.5194/egusphere-egu24-7149, 2024.

EGU24-7453 | Orals | GM9.6

Integrated 3D Seismic Analysis of Pleistocene Tunnel Valleys and their infills in the German North Sea sector  

Sonja Breuer, Anke Bebiolka, Axel Ehrhardt, Vera Noack, and Jörg Lang

Our research project is dedicated to the development of a comprehensive model for analysing the distribution, dimensions, and evolution of Pleistocene tunnel valleys and their deposits in northern Germany and adjacent areas. The primary objective is to leverage these findings to assess the likelihood of future tunnel-valley formation, with potential implications for the long-term (over the next 1 million years) safety of a radioactive waste repository.

To achieve our goal, we are relying on a 3D seismic dataset. Previously, the mapping of tunnel valleys on land is primarily based on 2D seismic and boreholes, which unfortunately do not provide the required accuracy. Therefore, we have opted to utilize a marine seismic dataset. This 3D seismic dataset 'GeoBasis3D' was acquired by the BGR in 2021.

The 3D seismic dataset is situated within the German Exclusive Economic Zone (EEZ) in the 'Entenschnabel' area. In this region, two intersecting tunnel valleys exist, with one located above the 'Belinda' salt dome. The interpretation of the tunnel-valley base based on the seismic data, and we will observe the influence of the crestal faults above the salt dome on the genesis and filling of the tunnel valley. The filling of the tunnel valleys will be described in terms of seismic facies. Different sedimentary processes can be interpreted from the seismic data. The deepest parts of the tunnel valley are directly filled, and the valley widens above. Some slumping can be detected along the steep slopes of the tunnel valley. Different phases of sedimentation can be observed within the tunnel valley, including both glacifluvial and glacilacustrine phases with parallel and homogenous reflectors. Since there are no available geological cores for the Quaternary in the area of the seismic surveys, we will have to rely on cores from Danish North Sea for the lithostratigraphic description of the sediments and for their chronological classification.

Our aim is to analyse sediment facies to draw conclusions about the backfilling process and repeated erosion phases. This will enable us to compare the findings with the development of onshore tunnel valleys in the next step. The tunnel valleys are a type of glacial erosion that can reach depths of up to 600 meters above sea level in northern Germany. They can have an impact on the long-term safety of a repository, which is required by law to be located at a minimum depth of 300 meters below ground level.

How to cite: Breuer, S., Bebiolka, A., Ehrhardt, A., Noack, V., and Lang, J.: Integrated 3D Seismic Analysis of Pleistocene Tunnel Valleys and their infills in the German North Sea sector , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7453, https://doi.org/10.5194/egusphere-egu24-7453, 2024.

Taiwan has excellent natural conditions for marine energy development. However, due to the active marine environment and geological processes, submarine geohazards must be carefully assessed before engineering development offshore southeastern Taiwan. Tectonically, it is situated in the oblique collision between the Eurasian Plate and the Philippine Sea Plate with fast exhumation and eroding transportation of sediments. Previous studies suggest that the Southern Longitudinal Trough (SLT) is characterized by a series of backthrusts and slumpings. Considering the rapid erosion and deposition led by extreme events, including typhoons and active tectonics, offshore SE Taiwan is an excellent site to study submarine geomorphology and seafloor instabilities.

After detailed structural and morphological analyses from seismic and bathymetry data, some geological features, faultings, gullies, and submarine canyon systems are recognized, moreover, several sliding scars and slumpings are interpreted from repeated and sequence surveys. It gives us insights into the potential mechanisms of sediment transportation and geological hazards by discussing the structure connections and distribution.

Since the study area has high ocean energy potential, appropriate site selection and development planning based on geological analysis should be carried out before marine industry projects. Whether in marine scientific research, site selection, engineering design, or social and economic development, studying geological processes and seabed stability offshore SE of Taiwan is urgent. Our results could provide a basis for subsequent seabed monitoring and engineering development.

How to cite: Chen, L. and Han, W.-C.: Submarine Geomorphology and Seafloor Instabilities Revealed from Geophysical Data Offshore Southeastern Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7466, https://doi.org/10.5194/egusphere-egu24-7466, 2024.

EGU24-8455 | ECS | Orals | GM9.6

Seismic and core-based glacial sequence stratigraphy of an overdeepened valley fill in northern Switzerland  

Sebastian Schaller, Bennet Schuster, Sarah Beraus, Marius W. Buechi, Hermann Buness, and Flavio S. Anselmetti

In the context of the DOVE (Drilling Overdeepened Alpine Valleys) project, supported by the International Continental Scientific Drilling Program (ICDP), a series of boreholes were drilled into buried overdeepened glacial troughs situated in the northern forelands of the Central and Eastern Alps. The sediments infilled into these troughs provide relatively complete sedimentary records of the Mid- and Late Pleistocene and help to better understand past glaciations, paleoclimate, and landscape evolution. As part of this project, an over 250 meters thick succession of unconsolidated Quaternary lacustrine and glacio-to-glaciofluvial sediments was successfully cored from the Basadingen Trough (ICDP 5068_2, NE Switzerland). This overdeepend trough is located in the NE sector of the former Rhine glacier's foreland lobe and is associated with an SSE-NNW valley system that connects the present-day Thur Valley with the Rhine Valley. This association, absent in the current surface morphology, is believed to have been active solely during the Middle Pleistocene.

The correlation of the core with two lines of high-resolution 2D seismic data (acquired during a pre-drill site survey) directly links seismic facies, the petrophysical data of the core (obtained from MSCL- and wireline-logging), and sedimentological properties. This link allowed us to develop a glacial sequence stratigraphy, based on which the overdeepend valley fill could be grouped into three glacial sequences (S1 – S3), enabling a more detailed reconstruction of the glacial advance and retreat history.

Furthermore, integration of the 2D seismic lines with the local geological information (e.g., drill cores, bedrock map, topography, model of the Quaternary sediment cover) has facilitated the establishment of a three-dimensional model of a segment of the Basadingen Trough. This model visualizes the shape of the initial bedrock incision, the multiphase trough-infill architecture, and the emplacement of fluvial channels overlaying the overdeepend basin. This three-dimensional approach overcomes inherent limitations in two-dimensional representations, providing a more accurate mapping of actual geometries. This study thus contributes to the development of a local glaciation model for the Basadingen Trough and a model of subglacial erosion of overdeepened basins in the northern Alpine foreland.

How to cite: Schaller, S., Schuster, B., Beraus, S., Buechi, M. W., Buness, H., and Anselmetti, F. S.: Seismic and core-based glacial sequence stratigraphy of an overdeepened valley fill in northern Switzerland , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8455, https://doi.org/10.5194/egusphere-egu24-8455, 2024.

EGU24-8468 | Orals | GM9.6

Examining sedimentological processes in a sublacustrine delta: from underflows to geomorphic changes (Lake Brienz, Switzerland) 

Gaétan Sauter, Damien Bouffard, Koen Blanckaert, Stefano C. Fabbri, Flavio Anselmetti, and Katrina Kremer

Slope failures within subaquatic deltas have the potential to induce underwater mass movements that can be tsunamigenic. Historical cases of subaquatic delta failures have been documented in marine contexts (Anthony & Julian, 1997; Bailey et al., 2021) and lacustrine settings (Girardclos et al., 2007; Hilbe & Anselmetti, 2015). However, the traces and failure planes of these mass movements are rapidly buried due to the high sedimentation rates caused by incoming rivers so that detailed process studies of such failures are challenging.

Given the rise in population near shorelines, there is a need to gain a deeper understanding of this hazard. By monitoring present-day sedimentation processes, we can gain insights into the dynamics of erosion, deposition, and potential slope failures. As lakes are more accessible than marine settings yet share similar sedimentation processes, lacustrine deltas can serve as natural laboratories for any deltaic system.

Our study employs a multi-method approach to monitor sedimentation processes within the Aare Delta of Lake Brienz, situated in a Swiss perialpine lake known for historical delta failures (Girardclos et al., 2007). This approach comprises (i) analyzing bottom currents derived from an Acoustic Doppler Current Profilers (ADCPs) campaign conducted from June to September 2022. These data are compared with river parameters (discharge, temperature, turbidity; from Federal Office of Environment) and meteorological data (rainfall, wind speed, directions; from Federal Office of Meteorology) to evaluate the governing processes of underflows, and (ii) examination of high-resolution bathymetric difference maps derived from two surveys conducted in 2018 and 2023. This assessment seeks to understand geomorphic changes over time and establish connections between these changes and the observed bottom currents.

We show the results of these campaigns that offer valuable insights into sedimentation processes within lacustrine deltas. Repetitive bathymetric surveys highlight substantial geomorphic changes in submerged channels, while ADCPs moored in those areas reveal the presence of underflow currents. Yet, the exact triggers behind these events remain unclear, challenging our understanding of sediment-transport mechanisms within the Aare Delta.

References:

Anthony, E. J., & Julian, M. (1997). The 1979 Var Delta Landslide on the French Riviera: A Retrospective Analysis. Journal of Coastal Research, 13(1), 27-35. http://www.jstor.org/stable/4298587

Bailey, L. P., Clare, M. A., Rosenberger, K. J., Cartigny, M. J. B., Talling, P. J., Paull, C. K., Gwiazda, R., Parsons, D. R., Simmons, S. M., Xu, J., Haigh, I. D., Maier, K. L., McGann, M., & Lundsten, E. (2021). Preconditioning by sediment accumulation can produce powerful turbidity currents without major external triggers. Earth and Planetary Science Letters, 562, 116845. https://doi.org/10.1016/j.epsl.2021.116845

Girardclos, S., Schmidt, O. T., Sturm, M., Ariztegui, D., Pugin, A., & Anselmetti, F. S. (2007). The 1996 AD delta collapse and large turbidite in Lake Brienz. Marine Geology, 241(1), 137‑154. https://doi.org/10.1016/j.margeo.2007.03.011

Hilbe, M., & Anselmetti, F. S. (2015). Mass movement-induced tsunami hazard on perialpine Lake Lucerne (Switzerland): Scenarios and numerical experiments. Pure and Applied Geophysics, 545-568. https://doi.org/10.1007/s00024-014-0907-7

How to cite: Sauter, G., Bouffard, D., Blanckaert, K., Fabbri, S. C., Anselmetti, F., and Kremer, K.: Examining sedimentological processes in a sublacustrine delta: from underflows to geomorphic changes (Lake Brienz, Switzerland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8468, https://doi.org/10.5194/egusphere-egu24-8468, 2024.

EGU24-8508 | ECS | Orals | GM9.6

A new fully erosive end-member to the strait depositional model: the importance of strong internal tides and shallow water settings, case of the Rion-Antirion Strait (Greece)  

Basile Caterina, Romain Rubi, Elias Fakiris, Dimitris Christodolou, Xenophon Dimas, Maria Geraga, George Papatheodorou, and Aurélia Ferrari

Straits are crucial in terms of oceanic circulation between basins. Many modern straits are dominated by tidal currents that flow differently than in the connected basins. These tidal currents are shaping the seafloor into complex geometries, alongside sediment sources, tectonic activities and inherited lowstand features. The proposed common tidal strait depositional model comprises a strait centre zone in erosion bounded on both sides by depositional areas with 2D and 3D tidal dunes (known as dune-bedded strait zones). This model does not consider another type of hydrodynamic forcing that can be generated in strait, internal tidal waves. The aim of this study is to evidence the combined effect of tidal currents and internal tides on the morphosedimentary features of the strait seafloor.

We focused here on the Rion-Antirion strait in Greece, connecting the Corinth Gulf with the Ionian Sea. Despite its location in the microtidal Mediterranean context, this 2 km wide and 70 m deep strait is strongly experiencing strong tidal currents. We utilized high-resolution multibeam bathymetry (MBES) covering a 21 km² area to reveal seafloor morphological structures. Swath bathymetric profiles were coupled with chirp sub-bottom and sparker reflection profiles imaging the internal sedimentary structures and with currents data from two ADCP campaigns. To comprehensively assess all the oceanographic parameters, we also incorporated satellite data and ROMS modelling. Consequently, we establish connections between oceanographic circulation, sea bottom dynamics within the strait and Gulf, and the observed sedimentary features.

Typically, in tidal settings, sand deposition occurs when the tidal current velocity drops, usually before the currents change direction, and the existing strait tidal model shows sand dunes. The complex bathymetry features observed in the Rion tidal strait lack dunes but features erosional characteristics such as deep pools and crest morphology, with limited depositional features. In our settings, the numerical model demonstrates that the strait experience strong tidal currents alongside currents associated with the internal tide, which are predominantly out of phase, generating significant turbulences. As a result, there are no periods during which sand can settle. These factors underline the absence of deposition in this case and the need to revise the strait depositional model to incorporate this new end-member.

How to cite: Caterina, B., Rubi, R., Fakiris, E., Christodolou, D., Dimas, X., Geraga, M., Papatheodorou, G., and Ferrari, A.: A new fully erosive end-member to the strait depositional model: the importance of strong internal tides and shallow water settings, case of the Rion-Antirion Strait (Greece) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8508, https://doi.org/10.5194/egusphere-egu24-8508, 2024.

EGU24-8780 | Posters on site | GM9.6

Assessing the influence of climate on Antarctic submarine gully evolution   

Jenny Gales, Robert McKay, Laura De Santis, Michele Rebesco, Jan Sverre Laberg, Denise Kulhanek, Molly patterson, Maxine King, and Sookwan Kim

Antarctica’s continental slopes hold invaluable insights for understanding past climate, ice-sheet dynamics, ocean circulation, erosional and depositional processes, and submarine geohazards over millennial timescales. We present a multidisciplinary dataset from the Ross Sea continental margin, Antarctica from the EUROFLEETS-funded ANTSSS expedition and International Ocean Discovery Program Expedition 374, including core records spanning ~3 Ma, multibeam echosounder and single-channel seismic data and legacy seismic data available through the Antarctic Seismic Data Library System. Here, gully and channel systems occur at the head of the Hillary Canyon, with palaeo-gullies evident in seismic data. New sediment core-seismic correlations show that palaeo-gullies evolved on the Ross Sea continental margin over multiple glacial cycles, filling and reforming associated with glacial advances, cold dense water cascading and other processes. We show multidisciplinary datasets that constrain the signature of down and along-slope processes and examine factors driving their timing, frequency, and impact on gully evolution. We discuss the implications of these findings in relation to Neogene and Quaternary West Antarctic Ice Sheet expansions to the shelf edge.

How to cite: Gales, J., McKay, R., De Santis, L., Rebesco, M., Laberg, J. S., Kulhanek, D., patterson, M., King, M., and Kim, S.: Assessing the influence of climate on Antarctic submarine gully evolution  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8780, https://doi.org/10.5194/egusphere-egu24-8780, 2024.

Area-wide hydroacoustic mapping in coastal environments is a time-consuming and cumbersome task due to the limited swath width of most devices, especially in shallow waters. At the same time, these environments hold important functions for coastal ecosystems, are subject to intensive anthropogenic use, and are characterized by dynamic and complex geomorphological interactions of waves, currents, and tides. We presently investigate the seafloor geomorphology of a marine protected area in the eastern North Sea based on a combination of own archived hydroacoustic data, hydrographic single-beam survey data, and fishing vessel position data. The research area is located within 12-nautical miles from the coast, covers approx. 1,200km2, and is characterized by water depths between 12 and 18 m. The topography of the seafloor is relatively flat and dominated by mobile sands although gravel and hard substrate (boulder reef) environments commonly occur throughout the area and are protected under the EU Habitats Directive. The properties and spatial distribution of these habitats remain currently unknown, despite the fact that the area hosts intensive fisheries with bottom-contact gears and one of Europe’s largest marine sand extraction sites. Our results show that the integration of different data sources allows an effective assessment of essential habitat parameters, natural seafloor processes, and anthropogenic stressors. Against this background, a strategy to more closely survey and/or monitor specific areas can be devised in order to better protect seafloor habitats and to mitigate human impacts on coastal ecosystems.  

How to cite: Sander, L., Yapa, T., Hoffmann, J., and Saathoff, M.: Ship-based mapping of protected seafloor habitats and anthropogenic stressors in a very shallow coastal environment: Spatial data integration in a marine protected area offshore Sylt (North Sea), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9300, https://doi.org/10.5194/egusphere-egu24-9300, 2024.

Late Quaternary paleoceanography and hydrography of the Sea of Marmara (SoM) have been extensively investigated because of its key location between the Black Sea and the Mediterranean Sea. Although the hydrography and paleoceanography of the SoM are reasonably known for the MIS 1-MIS 6, our knowledge of the stages is revealing and based on discontinuous seismic records from shelf cores. Integrated three-dimensional paleomorphologic and sedimentary modeling was used to predict the basin architecture and depositional pattern of sedimentary units in SoM.

By unraveling the structure and decompressing the stratigraphy of the targeted stratigraphic unit, we successfully modeled the ancient bathymetry during the MIS1-2 and MIS4-5 transition periods. Over 700 gridded 3.5 kHz high-resolution seismic profiles were processed, revealing distinct reflectors and stratigraphic units separated by reflectors that signify regional unconformities across 12 sediment piston cores, totaling approximately 25 meters in length. Accurate depth-scaling of chronostratigraphic units within cores is crucial for precise sedimentation rate calculations. Aligning seismic profiles with cores involved cross-referencing Multi-Sensor Core-Logger (MSCL) data with seismic reflection coefficients and amplitudes across various stratigraphic layers. Using data from the MSCL, we produced different synthetic seismograms to identify and correct depth-scale inconsistencies caused by mismatches in the upper sedimentary layers in seismic profiles. This technique is centered on synchronizing synthetic seismograms, derived from high-quality physical property logs, with corresponding CHIRP profiles to rectify these discrepancies. Mapping sequence boundaries, delineated by distinct reflection coefficients and amplitude values across the entire gulf area using pseudo-3D seismic data, allowed for comprehensive representation. To model basin evolution, isopach and isochron maps were constructed using a 2-D cubic B-spline interpolation method.

This study transferring the boundaries determined in marine isotopic periods, MIS5-MIS4, from cores to the acoustic environment for the creation of paleo-depth maps has been completed. Sample comparison models have been prepared on profiles taken from Çınarcık Basin towards Tekirdağ Basin for the application of grid interpolation modeling for different basins, using amplitude values from produced synthetic seismograms.

The robust age models derived from these cores, paired with reflectors corresponding to known levels in existing literature, positioned the marine-lacustrine transition at 13.7 k years before present (ka BP) at a water level of -85 meters and at 97.4 ka BP, the transition from marine to terrestrial environment. Using this timeline, we generated multiple maps illustrating paleo-bathymetry, sediment thickness, and mass-flow charts in the different basins, allowing us to simulate the environmental conditions in the SoM during the transitions.

Keywords: Sea of Marmara, Seismic Stratigraphy, Synthetic Seismogram, Age-Depth Modeling, Paleobathymetry Modelling

How to cite: Sabuncu, A., Eriş, K. K., Demirbağ, E., and Vardar, D.: Pre-Holocene Morphobathymetry of Sea of Marmara (SoM) Sedimentary Basins: A Case Study With Precise Correlations Developed by Sediment Cores and HR Seismic Profiles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9763, https://doi.org/10.5194/egusphere-egu24-9763, 2024.

EGU24-9993 | ECS | Posters on site | GM9.6

Understanding the paleogeographic evolution of the North Axial Channel, Southern North Sea  

Morgan Vervoort, Despina Kyriakoudi, Ruth Plets, Thomas Mestdagh, Tine Missiaen, and Marc De Batist

During the last 500 000 years, ice sheets occupied parts of the North Sea during three major glaciations. The existence of these ice sheets was accompanied by a large fall in sea level, causing the Southern North Sea to emerge and become isolated from the Atlantic. In this area a complex drainage system was created by river water of the West-European rivers (e.g., Thames, Rhine, Meuse and Scheldt) and glacial meltwater. Furthermore, most offshore studies support the idea of the formation of large proglacial lakes in front of these ice sheets, which may have caused high-magnitude outburst floods at the end of each glacial period. The existence of such a proglacial lake is used in the argument that glacial outburst floods during the Elsterian (500-450 ka) created erosional features still preserved nowadays in the Dover Strait.

A remnant of this large, complex fluvial and glacial drainage system is the (North) Axial Channel, a prominent geomorphological feature seen on the present-day sea floor of the Southern North Sea. Its formation and evolution, however, are still uncertain. Previous studies state that the Axial Channel forms the northern extension of the Lobourg Channel, located in the Strait of Dover, which was formed during Middle Miocene times. Further erosion is assumed to have occurred during the Pliocene and Pleistocene, as sediments within the Murray Pit (located in the Axial Channel, about 100 km northeast of the Lobourg Channel) are assumed to be Early Pliocene, and no Quaternary infilled sediments have been identified. A series of NE-SW oriented scarps are identifiable from bathymetric and seismic reflection data and have been attributed to different Pleistocene incisional events. However, currently only a relative chronology of potential events has been established, with large uncertainties. Understanding the paleogeographic changes that affected the region also increases the knowledge on how early humans may have settled in and/or migrated through the region. 

In the framework of the WALDO project (“Where are All the (proglacial) Lake seDiments in the NOrth Sea Basin?”), a survey has been conducted in October 2023 during which high-resolution geophysical data (multibeam bathymetry and backscatter, acoustic and seismic data) combined with ground-truth data (vibrocores) have been acquired. One of the reflection-seismic grids was conducted ~40 km east of the East of England coast, over the western edge of the North Axial Channel, where also four sediment cores were taken. Here, we present the first interpretation of these new data, which allow us to evaluate, update and improve the relative chronology of the formation of the (North) Axial Channel.  

How to cite: Vervoort, M., Kyriakoudi, D., Plets, R., Mestdagh, T., Missiaen, T., and De Batist, M.: Understanding the paleogeographic evolution of the North Axial Channel, Southern North Sea , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9993, https://doi.org/10.5194/egusphere-egu24-9993, 2024.

EGU24-10335 | ECS | Posters on site | GM9.6

Exploring the Outline of the Pre-Odra River System Through Seismic Reflection Imaging Offshore Rügen Island 

Maryse C. Schmidt, Christian Hübscher, Elisabeth Seidel, Jonas Preine, and Benedikt Haimerl

Understanding the course and dynamics of ancient river systems, such as the pre-Odra, is crucial for unravelling the geological history of regions like the southern Baltic Sea, providing valuable insights into the post-glacial evolution of landscapes and riverine processes. We will present marine reflection seismic and acoustic data from three research cruises on the research vessel ALKOR that allow us to investigate the pre-Odra river system in the southern Baltic Sea. Our analysis focuses on the region off the east coast of the island Rügen. This region corresponds to the suspected location of the pre-Odra river system, which was situated during the post-glacial phase approximately 9,000 - 14,500 years BP off Rügen. The seismic reflection data indicate that the sediment infill of the pre-Odra is charged by shallow gas of presumably biogenic origin. Since the seismic gas indicators correspond with the pre-Odra where its location has been determined by previous geological studies, we use gas lineaments as a proxy for the braided paleo-river bed. This study refines and extends the known fluvial extent of the Odra river system by 60 km, tracing it north towards the Tromper Wiek, indicating its terminus in the Baltic Sea close to eastern to Rügen.

How to cite: Schmidt, M. C., Hübscher, C., Seidel, E., Preine, J., and Haimerl, B.: Exploring the Outline of the Pre-Odra River System Through Seismic Reflection Imaging Offshore Rügen Island, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10335, https://doi.org/10.5194/egusphere-egu24-10335, 2024.

EGU24-10619 | ECS | Posters on site | GM9.6

Josephine Submarine Seamount: New Insights from multibeam data and seabed sampling for environmental conditions in the Early Quaternary 

Vasco Carvalho, Pedro Terrinha, Marta Neres, Antje Voelker, Luís Batista, and Marcos Rosa

The Josephine submarine seamount is located in the NE Atlantic Ocean around 470 km west of the coast of mainland Portugal and 500 km northeast of Madeira Island on the vicinity of the Africa-Eurasia plate boundary. With 47 km in length and 10 km in width, it rises 2500 meters above the adjacent abyssal plains, with its top standing at a depth of 170 m. It is a basaltic submarine seamount that yielded ages of 16.3 ± 0.9Ma to 11.7±0.7Ma (Geldmacher et al. 2006).

Multibeam and backscatter data were acquired to increase our knowledge about the seamount. The backscatter data shows the presence of fine sediment on the eroded top of the seamount, not present in the northern part. The top of the seamount dips gently (~1º) to the northwest allowing the deposition of fine grained sediment down to ~500 m where the seafloor is irregular with slopes dipping between 10⁰ and 15⁰ and the igneous rocks crop out.

Morphologic analysis suggests that the very flat and smooth surface of the southernmost portion of Josephine Seamount has been above sea level and subjected to near coastal erosive processes of areas lying at ~420 m depth. Since the sea level of the last 15 Ma has not been lower than 160 m of the present-day levels (Miller et al. 2020), tectonic and/or erosional processes must have lowered the seamount’s height by at least 260 meters.

Sedimentary rocks were dredged from depths from 480 to 347 m, on the southeastern part of the Josephine seamount and were analyzed for their shape, composition and sedimentary facies. The dredged samples are calciclastic limestone blocks that have a half horn torus shape (donut). Most of the specimens are trespassed by a 3 to 5 cm long conical cavity that developed from the base to the top of each sample.

The rocks consist of 96.6% of foraminifera tests (82.4% planktic and 17.6% benthic), with a very low mineral content. The grains are diagenetically cemented by a calcite matrix (confirmed by EDS analysis). The presence of the planktonic foraminifera species Globorotalia truncatulinoides, whose first occurrence dates of 1.93 Ma (Wade et al., 2011), provides a maximum age of formation, making these sedimentary rocks at least 10 Ma younger than the volcanic rocks that constitute the Josephine Seamount basement. The presence of the benthic foraminifera Lobatula lobatula and Discanomalina semipunctata indicate strong currents that could have contributed to the erosion of the seamount’s top.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds through the project LISA (https://doi.org/10.54499/PTDC/CTA-GEF/1666/2020).

How to cite: Carvalho, V., Terrinha, P., Neres, M., Voelker, A., Batista, L., and Rosa, M.: Josephine Submarine Seamount: New Insights from multibeam data and seabed sampling for environmental conditions in the Early Quaternary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10619, https://doi.org/10.5194/egusphere-egu24-10619, 2024.

EGU24-10732 | ECS | Posters on site | GM9.6

Imaging the Plio-Quaternary submarine geomorphological evolution of the Gulf of Cagliari 

Maria Cristina Caradonna, Anna Del Ben, Riccardo Geletti, Gian Andrea Pini, Veronica Frisicchio, Gemma Ercilla, and Ferran Estrada

Based on the morpho–bathymetric data coming from the MaGIC project (Marine Geohazards along the Italian Coast) and the high-resolution seismic reflection profiles acquired in 2010 by OGS-Explora, we depict the complex geomorphology of the Gulf of Cagliari and the evolution of the most striking morphosedimentary features developed during the PQ. The seafloor is shaped by the canyon system, the Sarroch and S. Elia-Foxy canyons. The obtained results point that their onset and location do not coincide with paleoincisions formed by the Messinian erosion. The main pathway changes of the Sarroch canyon are conditioned by extensional tectonics of the Campidano Graben and are controlled by the Banghittu High. Cut-and-fill features and infill deposits indicate that retrogressive erosive processes affect the canyon heads and produce landslides. transport deposits in the basin. In fact, four large MTD's have been recognized and analysed within the PQ sequence. They show different seismic facies, from transparent to chaotic, and are locally affected by internal deformational structures which allow us to distinguish the translational and compressional domains. The interplay between the morphosedimentary evolution of the systems canyons and the MTDs are useful to understanding the role played by the downslope channelized and non-channelized sedimentary processes over time and to explore the factors, local and/or global, controlling their occurrence and/or predominance. This analysis of the submarine canyon morphologies and occurrence of MTDs can help evaluate the potential geo-hazard implications of the region.

How to cite: Caradonna, M. C., Del Ben, A., Geletti, R., Pini, G. A., Frisicchio, V., Ercilla, G., and Estrada, F.: Imaging the Plio-Quaternary submarine geomorphological evolution of the Gulf of Cagliari, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10732, https://doi.org/10.5194/egusphere-egu24-10732, 2024.

EGU24-10857 | Posters on site | GM9.6

Assessing the dynamics of turbiditic terminal lobes: a geometrical approach 

Jean-Louis Grimaud, Louison Mercier, Fabien Ors, and Damien Huyghe

Terminal lobes constitute the endmembers of siliciclastic systems. They are of great interest to marine geologists and constitute high-quality reservoirs actively sought out and exploited by the oil and gas industry. The sizes and shapes of lobes vary depending on the type of sedimentary system and the nature of associated gravity flows. Sea bottom topography -induced either by preexisting lobes or mass transport deposition or tectonic deformation- is another important factor controlling lobe morphology. Previous studies carried out on recent systems (based on multibeam bathymetry and 2D/3D seismic data) show different shapes, classically characterized as lobate, but also radial or elongated. Currently, much remains to be known on the relative influences of autocyclic and allocyclic forcings on the internal architecture of lobes.

This study focuses on a better definition of lobe shapes in natural systems to build a ruled -based model of lobes that will later be incorporated into the FLUMY© software. To this end, a database is built based on cases from the literature in various systems (e.g., the Congo, Amazon, Indonesia and East Corsica). We use the classical shape ratios defined by Prélat et al. (2010) as well as a new metric, called the progradation factor (PF), defined as the length ratio between the upstream and downstream segments of lobes (i.e., with respect to their centroids).

Measures of PF were applied at different scales from the bed element to the lobe complex. Independently of the sedimentary system type, three different shapes of lobate bodies were identified: (i) a “classical” lobate shape -wider downstream- when PF > 1.15, (ii) lobes that are wider upstream when PF < 0.85 and, (iii) an elliptical shape when 0.85 ≤ PF ≤1.15. The classical lobate shape is interpreted as marking the absence of topographic confinement. Elliptical lobes occur mainly during maximum and minimum of progradation/retrogradation cycles. Lobes that are wider upstream result from topographic confinement and are mainly deposited at the end of retrogradation cycles. Finally, plotting thickness vs area allows identifying semi-confined lobes as a third category located between confined and unconfined lobes. This category follows a linear trend and exhibits a minimum thickness of 20 m.

How to cite: Grimaud, J.-L., Mercier, L., Ors, F., and Huyghe, D.: Assessing the dynamics of turbiditic terminal lobes: a geometrical approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10857, https://doi.org/10.5194/egusphere-egu24-10857, 2024.

EGU24-10932 | ECS | Posters on site | GM9.6

Glacial seismic geomorphology offshore northwest Europe 

Andrew Newton, Alexandr Montelli, Christine Batchelor, Benjamin Bellwald, Rachel Harding, Mads Huuse, Julian Dowdeswell, Dag Ottesen, Ståle Johansen, and Sverre Planke

Plio-Pleistocene records of ice-rafted detritus suggest that northwest European ice sheets regularly advanced across palaeo-coastlines. However, while these records are important, they provide only a limited insight on the frequency, extent, and dynamics of the ice sheets that were delivering the detritus. Three-dimensional reflection seismic data of the northwest European glaciated margin have previously documented buried glacial landforms that inform us on these uncertainties. This work combines existing landform records with new seismic geomorphological observations to catalogue landform occurrence along the European glaciated margin and considers how these features relate to ice sheet history. The compilation shows that Early Pleistocene ice sheets regularly advanced onto and across the continental shelves. This is important because Early Pleistocene sea level reconstructions show lower magnitude fluctuations between glacial-interglacial cycles than when compared to the Middle-Late Pleistocene. The potential for more extensive and more frequent Early Pleistocene glaciation provides a possible mismatch with these sea level reconstructions. This evidence is considered with global records of glaciation to contemplate the possible impacts on our wider understanding of Plio-Pleistocene climate changes, in particular how well Early Pleistocene sea level records capture ice sheet volume changes and how quickly large ice sheets waxed and waned. Resolving such issues relies on how well landforms are dated, whether they can be correlated with other proxy datasets of environmental change, and how accurately these proxies reconstruct the magnitudes of past climatic changes. The results leave many more questions about Pleistocene glaciation in Europe unresolved, with significant impacts on our global understanding of how sea level evolved through the Pleistocene and its association with ice sheet development.

How to cite: Newton, A., Montelli, A., Batchelor, C., Bellwald, B., Harding, R., Huuse, M., Dowdeswell, J., Ottesen, D., Johansen, S., and Planke, S.: Glacial seismic geomorphology offshore northwest Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10932, https://doi.org/10.5194/egusphere-egu24-10932, 2024.

EGU24-11305 | ECS | Posters on site | GM9.6

Plio-Quaternary geological events in the Western Mediterranean Sea: focus on the West Sardinian margin and adjacent oceanic basin 

Veronica Frisicchio, Anna Del Ben, Riccardo Geletti, Maria Cristina Caradonna, Michele Rebesco, and Massimo Bellucci

The Plio-Quaternary sedimentary deposition in the Western Mediterranean Sea was strongly influenced by the Messinian Salinity Crisis (MSC) and by the consequences of the oceanic opening that produced regional fault systems and the following thermal subsidence, still largely active during the Plio-Quaternary (PQ). We analyse the PQ events that occurred in the West Sardinian margin and in the adjacent deep basin by integrating vintage and more recently acquired seismic data, obtaining the currently most complete regional seismic grid in the study area. The base of the PQ (“Ms” reflector) represents the top of the Messinian evaporites in the lower slope and deep basin and the Messinian erosional truncation in the continental upper slope and shelf. Two units have been recognized within the PQ sequence: the low amplitude lower Plio-Quaternary unit (l-PQ) and the high amplitude upper Plio-Quaternary unit (u-PQ), separated by the “A0” reflector, for which we assume an age of 2.6 My (near Quaternary base), through the correlation with the published ECORS profile.

The thermal subsidence, related to the Oligo-Miocene (OM) oceanic opening, produced the increased inclination of the slope and, coupled with the halokinetics of Messinian evaporites, triggered most of the geological processes in the study area. In the lower continental slope, rollover structures are produced by salt sliding, which is related to the increased deepening of the slope, while in the deep basin typical sub-vertical faults developed above the salt diapirs: these processes, that continued throughout the entire PQ slowing down in the Quaternary, influence the thickness and distribution of the PQ sequence. Faults usually act as a preferential path for magma upwelling and gas rising: fault systems developed during the OM produced some large volcanoes at the boundary between slope and deep basin, while on the continental shelf and upper slope the main volcanic buildings are ascribed to the later Pliocene magmatic phase and are related to fault reactivation caused by the PQ thermal subsidence. On the tilted continental outer shelf, OM faults reactivation led to gas rising phenomena and related pockmarks, generated from the Early Pliocene until Present. During the Quaternary, the accentuated tilting of the continental slope triggered erosional processes that led to the formation of three new canyon systems, not inherited by the Messinian erosion as often hypothesized; at the same time, erosion of the onshore area led to a high sediment supply, responsible for the widening of the clinoforms on the inner shelf. In this study we analyse the evolution of the different PQ process that affected the West Sardinian margin and their relationships with previous regional events occurred in all the West Mediterranean Sea: the objective is to create basic information to subsequently compare with other passive margins of the sea.

How to cite: Frisicchio, V., Del Ben, A., Geletti, R., Caradonna, M. C., Rebesco, M., and Bellucci, M.: Plio-Quaternary geological events in the Western Mediterranean Sea: focus on the West Sardinian margin and adjacent oceanic basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11305, https://doi.org/10.5194/egusphere-egu24-11305, 2024.

EGU24-12684 | ECS | Posters on site | GM9.6

Deciphering the origin of sediment waves along the Northwest African margin through multidisciplinary analysis 

Rebecca Englert, Christoph Boettner, Peter Brandt, Matthieu Cartigny, Hao Huang, Gerd Krahmann, Pere Puig, Mischa Schoenke, Christopher Stevenson, Peter Talling, and Sebastian Krastel

Sediment waves are widely observed on the seafloor in a variety of marine environments (e.g., open slope, submarine channels, levees). They are important for understanding marine hazards because they can influence slope stability and be indicators of currents capable of damaging seafloor infrastructure (e.g., telecommunication cables). However, sediment wave dynamics may vary in different settings and several mechanisms have been invoked to explain their formation including gravity-driven (sediment failure, turbidity currents) and oceanographic (bottom currents, internal tides) processes. In this study, we investigate the generation of large unconfined sediment wave fields along the continental slope of the Northwest African margin using an integrated dataset acquired on the R/V Maria S. Merian cruise MSM113. Data collection included direct monitoring of ocean currents and water column properties over sediment wave fields by CTD casts, acoustic water column profiling, and deployment of short-term moorings equipped with velocity (ADCPs), temperature, salinity, and turbidity sensors. Additional datasets such as shallow and multichannel 2D seismic profiles, multibeam bathymetry, gravity cores, and box cores capture the geomorphic, subsurface, and sedimentary characteristics of the seafloor features. Sediment wave fields occur on the mid-lower slope between 600 – 1900 m water depths and are intersected by straight channels up to 2 km wide and 300 m deep. Individual waves have slope-parallel crests, wavelengths between 400 – 2000 m, and wave heights between 6 – 56 m. In subsurface seismic profiles, sediment waves are composed of upslope-stacking reflectors that indicate preferential deposition on their stoss slopes and upslope crest migration. Sediment cores from sediment waves are predominantly composed of bioturbated gradational sequences of mud, sandy mud, muddy sand, and sand that vary depending on location, suggesting a progressive process of differential sedimentation. Intermittent chaotic muddy deposits and sharp-based sand layers represent occasional punctuated flow events. Time series from moored instruments are dominated by strong semidiurnal tidal fluctuations with current velocities up to 0.3 m/s. Water column measurements and acoustic images reveal a stratified water column with wavy interfaces and small-scale fluctuations caused by the passage of internal waves. Collectively, these findings suggest that downslope gravity flows, along-slope currents, and internal tides contribute to sediment transport along the Northwest African margin; although, tide-topographic interactions are the most likely candidate for maintaining sediment waves. Our integrated analysis provides insight into oceanographic processes, which shape the seafloor and transport sediment along ocean margins.

How to cite: Englert, R., Boettner, C., Brandt, P., Cartigny, M., Huang, H., Krahmann, G., Puig, P., Schoenke, M., Stevenson, C., Talling, P., and Krastel, S.: Deciphering the origin of sediment waves along the Northwest African margin through multidisciplinary analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12684, https://doi.org/10.5194/egusphere-egu24-12684, 2024.

EGU24-13887 | ECS | Orals | GM9.6

Forward seismic modelling, a tool for the prediction of offshore sedimentary architectures. Application to the Roussillon Basin's Pliocene land-see prism (Gulf of Lion, France). 

Teddy Widemann, Eric Lasseur, Johanna Lofi, Benoît Issautier, Carine Grélaud, Serge Berné, Philippe A. Pezard, and Yvan Caballero

The prediction of offshore sedimentary architectures is a first plan approach to the geological study of continental margins. While such work is commonly led using seismic surveys tied to well-logs, we are interested in land-sea objects for which there is no direct tie between seismic signal and lithology. More precisely, we look at shoreline clinoforms and more continental deposits of which size is below used seismic resolution, and their integration at the shelf-scale. The Roussillon Basin’s Pliocene infill satisfies these criteria. It belongs to a progradational land-sea prism about 100km-long, displaying essentially clinothems and defining the Gulf of Lion modern shelf. It is described with high quality conventional seismic profiles offshore, while outcrops and drill-cores are available onshore. However, there is no data at the transition between the two domains.

In order to predict the offshore sedimentary architecture, we establish classical equivalence hypotheses between seismic facies and expected associated sedimentary facies. This work is based on the seismic facies interpretation and on the lithologies known from outcrops and onshore drillings.

Nonetheless, without directly tied-in seismic such hypotheses rely essentially on interpretation. This, together with seismic data vertical resolution (~15m in thickness) and the upscaling from direct observations onshore, introduce uncertainties.

In order to produce more reliable sedimentary predictions, we test our hypotheses through forward seismic modelling using SeisRoX pro by NORSAR. We create small scale geological/impedance models based on onshore sedimentary observations coupled with well-logs petrophysical data (P-wave velocities). Then we simulate acoustic waves propagation through them and obtain theoretical seismic profiles that are subsequently compared to the seismic data.

This method, including a geophysical control, allows for the testing of various geological hypothesis at the outcrop-scale, and for a more objective subsurface description.

Among the results, we show that vertical velocity variations at a meter scale eventually get a specific seismic signature in terms of both geometry and amplitude on conventional seismic profiles. More generally, we illustrate different lithological models and their results, which allow for a high-resolution reconstruction of most parts of the Roussillon Basin’s Pliocene offshore prism.

How to cite: Widemann, T., Lasseur, E., Lofi, J., Issautier, B., Grélaud, C., Berné, S., Pezard, P. A., and Caballero, Y.: Forward seismic modelling, a tool for the prediction of offshore sedimentary architectures. Application to the Roussillon Basin's Pliocene land-see prism (Gulf of Lion, France)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13887, https://doi.org/10.5194/egusphere-egu24-13887, 2024.

Offshore wind projects benefit immensely from a good understanding of the seafloor. Together with the sub-bottom geology and geotechnical properties as well as geohazards and physical hazards, the seafloor conditions can be integrated in ground models and hazard maps as part of a holistic offshore wind site characterization, that enables successful wind farm development and reliable power production.

A full understanding of the seafloor requires “seafloor reading skills”: appropriate data mining, utilization, and interpretation. The seafloor is full of geological, environmental, and anthropogenic features which may affect a wind farm during its lifecycle, such as boulders, mobile sediment, escarpments/faults, wrecks, UXO, cables, seabed habitats and much more. However, when understood properly, we can comprehend the seabed conditions and processes and handle the different challenges at the seabed from installation to production, affecting e.g., foundation feasibility and HSE.

Sørlige Nordsjø II is an envisaged offshore wind site in the southern Norwegian North Sea. Following a multi-method approach, we utilized different geological and geophysical data, such as MBES bathymetry and backscatter, side scan sonar data, boreholes and vibrocores, sub-bottom profiler data, and 2DUHR seismic.

Key results that were achieved include:

  • Detailed seafloor lithology map: Differentiation between different sand facies and glacial lag deposits.
  • Understanding of sediment mobility: Sand waves and megaripples mapped; bedforms, grain size variations and anthropogenic features linked to zones of erosion, transport, and deposition.
  • Determination of boulder locations: Boulder fields and individual boulders mapped; size of boulders determined to mostly up to 3 m.
  • Update of cable and wreck positions, by utilizing backscatter and side scan sonar images, and magnetic anomalies.

We were able to pull out deep knowledge from the available data, to bring it in a coherent order and provide a holistic understanding of the site’s seafloor. This is a major step towards the aim of making informed cost-saving decisions throughout the offshore wind lifecycle.

How to cite: Gehrmann, A. and Lekens, W.: How to read the seafloor and the importance to offshore wind projects. Examples from Sørlige Nordsjø II, Norwegian North Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15545, https://doi.org/10.5194/egusphere-egu24-15545, 2024.

EGU24-15710 | ECS | Orals | GM9.6

New insight into the Evolution of the Jasmund Glacitectonic Complex from Seismic Mapping of Glacial Erosion Unconformity East of Rügen (SW Baltic Sea) 

Benedikt Haimerl, Elisabeth Seidel, Anna Gehrmann, Jonas Preine, Maryse C. Schmidt, and Christian Hübscher

The Jasmund Glacitectonic Complex (JGC) on the island of Rügen (NE Germany) is a key area where the interplay between glaciation, erosion and tectonics can be studied. Previous reconstructions are based on land-based and outcrop studies. Here, we use 148 high-resolution multi-channel seismic reflection profiles from several cruises of the University of Hamburg with RV ALKOR as well as adjacent borehole data to decipher the offshore extent of the JGC. The seismic data image erosional channels and depressions as well as moraines, which delineate the mainly southwestward directed Weichselian glacier movement. The depth of the erosional surface at around 100 m correlates with the previously modelled décollement depth. Furthermore, these results suggest a continuation of the observed glacial features onshore, highlighting the connection between the marine and terrestrial features of the JGC. Our investigations suggest that the complex evolution of the JGC is not due to three distinct ice streams, as proposed by previous studies. Instead, our data suggest that a single southwestward ice flow, which splits northeast of Jasmund, is responsible for the three-phase evolution. During the formation of the northern and eastern subcomplexes, the Cretaceous sediments were overthrusted almost perpendicular to the ice movement. In the southern subcomplex, however, the overthrusting was caused by the lateral pressure of the ice flow passing south of Jasmund. This study provides a methodological blueprint for the study of similar glacitectonic complexes elsewhere.

How to cite: Haimerl, B., Seidel, E., Gehrmann, A., Preine, J., Schmidt, M. C., and Hübscher, C.: New insight into the Evolution of the Jasmund Glacitectonic Complex from Seismic Mapping of Glacial Erosion Unconformity East of Rügen (SW Baltic Sea), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15710, https://doi.org/10.5194/egusphere-egu24-15710, 2024.

EGU24-16357 | ECS | Posters on site | GM9.6

Present-day current activity in an inactive canyon-channel system: the Gollum Channel System offshore southwest Ireland. 

Lotte Verweirder, David Van Rooij, Fred Fourie, Kobus Langedock, Martin White, and Aggeliki Georgiopoulou

The Gollum Channel System is a land-detached large-scale canyon-channel system situated offshore southwest Ireland on the Northeast Atlantic margin. The system is considered to have been inactive since the Last Glacial Maximum (LGM), but newly acquired geophysical seafloor and shallow subsurface data do suggest recent activity. To test the hypothesis of present-day (in)activity, high-resolution side-scan sonar, photography and bathymetry data were collected using an AUV in the upper slope (350-1000 m water depth) section of two of the channels. These data are presented alongside current meter data from a mooring station in one of the channels, which were used for quantification and validation of the AUV results. The presence of current ripples on the channel floor indicates that bottom currents acting here are capable of the (re)distribution of sediments. Additionally, some features in the AUV data are interpreted as patches of cold-water corals that depend on nutrient influx as well as a hard enough substrate to grow on, both of which may be promoted by bottom current activity. The current meter data show bottom currents had an average velocity of 15.1 cm/s and reached a maximum of 53.7 cm/s during the measurement period. Therefore, collectively, these datasets allow interpretation of the channel floor features visible within the AUV data with respect to the current regimes they represent, and vice versa. At present, bottom current activity seems prevalent in the channels, while activity from gravity flows has not been observed.

How to cite: Verweirder, L., Van Rooij, D., Fourie, F., Langedock, K., White, M., and Georgiopoulou, A.: Present-day current activity in an inactive canyon-channel system: the Gollum Channel System offshore southwest Ireland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16357, https://doi.org/10.5194/egusphere-egu24-16357, 2024.

EGU24-16490 | Orals | GM9.6 | Highlight

A decade of multibeam bathymetric mapping: Implications and lessons learned from (peri-)Alpine lakes in Switzerland 

Katrina Kremer, Stefano Fabbri, Michael Hilbe, and Flavio S. Anselmetti

Studying the morphology of the landscape is crucial for understanding the processes that shape the Earth’s surface. In subaqueous environments, where direct observations are challenging, bathymetry-derived terrain models are the fundamental form of geomorphological data. Over a century ago, Switzerland initiated systematic bathymetric surveys under the federal "Siegfried Map" project, marking an effort to explore the subaquatic morphology of perialpine lakes. These early studies laid the groundwork for subsequent research on the subaqueous landscape in Switzerland. The early bathymetric surveys in Switzerland focused on documenting the general shape of deep basins and discovering features on lake floors such as channel levee complexes and sublacustrine moraine ridges. These observations formed the basis for early theories on the age of the last glaciation and the existence of turbidity currents in lakes.

Recent advances in multibeam swath bathymetry systems combined with differential GNSS location services dramatically improved survey efficiency as well as spatial and vertical resolution by several magnitudes, generating new findings with every surveyed lake. Apart from the reconnaissance of the overall basin shape, the detailed geomorphologic mapping led to the discovery of various subaquatic features, such as landslides and rockfalls, glacial features, pockmarks, channel and canyon systems, fault structures, and prehistoric and historic human impact. These findings had significant implications for evaluating natural hazards caused by earthquakes, floods, and tsunamis. Detailed glacial imprints became suddenly visible in high-alpine proglacial lakes, revealing the recessional behavior of glaciers. Mapping the source area of mass movements on the lake’s slopes represents the base for understanding lacustrine tsunamis and their modeling. Subaquatic canyons of deltaic systems often extend further into deeper waters than anticipated, promoting accelerated transport of coarse-grained sediments into the deepest parts, typical target areas for major drilling campaigns. Submerged traces of prehistoric settlements revealed unexpected chapters of human activities. Therefore, no drilling effort should be planned without a detailed lake floor map.

In this contribution, we will outline lessons learned from these surveys of 22 lake systems across Switzerland since 2007, summarize key findings, and review the implications of the technology on the limnogeological community. We will also glimpse the future and explore what to expect from ongoing 4D-bathymetric mapping campaigns.

How to cite: Kremer, K., Fabbri, S., Hilbe, M., and Anselmetti, F. S.: A decade of multibeam bathymetric mapping: Implications and lessons learned from (peri-)Alpine lakes in Switzerland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16490, https://doi.org/10.5194/egusphere-egu24-16490, 2024.

EGU24-17529 | Posters on site | GM9.6

A glimpse below the wine-dark sea: Multi-beam bathymetric survey around Despotiko and Strongylo islands (Cyclades, Greece) 

Erwin Heine, Erich Draganits, Dimitris Sakellariou, and Ioannis Morfis

Our understanding and knowledge about Earth´s surface and processes benefitted greatly from the increasing availability of open accessible, large-scale remote sensing topographic data, including GTOPO30 (c. 1 km, 1996), ASTER (c. 30 m, 2009), SRTM 3.0 (c. 30 m, 2014) and TanDEM-X (c. 12 m, 2014). In comparison, the documentation of the sea floor at higher resolutions and/or its accessibility is scarce (e.g. https://emodnet.ec.europa.eu/en/bathymetry, https://www.ngdc.noaa.gov/mgg/bathymetry/lidar.html, Otero & Mytilineou 2022) and vast submarine areas are still a terra incognita. We have carried out a preliminary multi-beam bathymetric survey during 29-31 May 2023 with the 13.4 m research vessel “Alkyon” of the Hellenic Centre for Marine Research, funded by the Cheops Privatstiftung Wien and the Walter Munk Foundation for the Oceans (https://www.waltermunkfoundation.org). The Alkyon was equipped with a hull-mount Teledyne Reson T-50R multibeam echosounder. In total, an area of 26.8 km2 was surveyed west, south and east of Strongylo Island, south of Despotiko Island up to Cape Petalida at the southern tip of Antiparos and especially the Bay of Despotiko, between Despotiko and Antiparos islands with measured depth ranging between -6.7m to -105.7 m below sea-level. The survey aims include the (i) high-resolution documentation of this previously unknown sea-floor, (ii) information concerning local sea-level rise (see Lykousis 2009, Kolaiti & Mourtzas 2020, 2023), (iii) the possible continuation of tectonic features as well as coastal mass-movements investigated above sea-level. Processing and thorough geomorphological analysis of the high resolution bathymetric data provide valuable information on the extend of posidonia meadows on the seafloor  (e.g. Despotiko Bay), evidence for possible palaeo-sealevel indicators (palaeo-coastlines, wave-cut terraces) at various depths, palaeo-valleys and other geomorphological features belonging to the terrestrial landscape that was drowned during the post-glacial sea-level rise, as well as several deposits associated with the mass movements mapped on the adjacent rocky slopes of Strongylo, Despotiko and South Antiparos islands. Marine geological-geophysical research will be continued and complimented with high resolution sub-bottom profiling data and visual observation to unravel the recent geomorphological evolution of the survey area.

Kolaiti, E. & Mourtzas, N. 2020. New insights on the relative sea level changes during the Late Holocene along the coast of Paros Island and the northern Cyclades (Greece). Annals of Geophysics, 63(6), https://doi.org/10.4401/ag-8504

Kolaiti, E. & Mourtzas, N. 2023. Late Holocene relative sea-level changes and coastal landscape readings in the island group of Mykonos, Delos, and Rheneia (Cyclades, Greece). Mediterranean Geoscience Reviews, 5, 99-128. https://doi.org/10.1007/s42990-023-00104-4

Lykousis, V. 2009. Sea-level changes and shelf break prograding sequences during the last 400 ka in the Aegean margins: Subsidence rates and palaeogeographic implications. Continental Shelf Research, 29(16), 2037-2044.

Otero, M. & Mytilineou, C. (eds.) 2022. Deep-sea Atlas of the Eastern Mediterranean Sea: Current knowledge. IUCN-HCMR DeepEastMed Project. IUCN Gland, Málaga, 371 p. https://uicnmed.org/docs/deep-sea-eastern-med/DEEP-SEA-EASTERN-MEDITERRANEAN.pdf

How to cite: Heine, E., Draganits, E., Sakellariou, D., and Morfis, I.: A glimpse below the wine-dark sea: Multi-beam bathymetric survey around Despotiko and Strongylo islands (Cyclades, Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17529, https://doi.org/10.5194/egusphere-egu24-17529, 2024.

EGU24-18223 | ECS | Orals | GM9.6

Investigation of sedimentary structures associated with the Deep Western Boundary Current in French Guiana (Demerara Plateau) 

Paul Blin, Lies Loncke, Xavier Durrieu de Madron, Pauline Dupont, Ivane Pairaud, Sébastien Zaragosi, Kelly Fauquembergue, Christophe Basile, and Scientific team Diadem

The Demerara Plateau in the Equatorial Atlantic is a transform marginal plateau (TMP) where the Deep Western Boundary Current (DWBC) transports North Atlantic Deep Water (NADW) to the South Atlantic. This current, circulating in the depth between 1300 and 3500 m, represents the deep part of the thermohaline circulation. It also forms hundreds of sedimentary structures along its path, looking like giant flute-casts and called 'comets’. Those comets can reach 3 km in length and theses field of 'comets' more than ten kilometers large. Nautile dives, AUV acquisitions (equipped with Multibeam Sounder SMF, Doppler current meter ADCP, Sediment Sounder) and a mooring, implemented during the DIADEM campaign (N/O Pourquoi Pas?, January-February 2023, DOI : 10.17600/18000672), first allow to document the dynamics of the current DWBC in this equatorial domain, its spatial and temporal variability. Furthermore, investigated the numerous associated sedimentary systems associated with this current, as the "comets" forming giant erosion structures. Two AUV bathymetric surveys and four Nautile dives have helped to better understand the location of these hydrodynamic structures. They are located along outcrops of intensely tilted and fractured carbonated rock, probably associated with an ancient sliding mass. Nautile data coupled with photogrammetry are also used to reconstruct the outcrops of these carbonate blocks and to characterize their deformation. AUV ADCP data (hydrodynamics) acquired in parallel highlight the difference in current intensity between the comet head, where the current has a much greater magnitude than in the comet tail, which appears more sedimented. Measurements of currents and turbidity recorded at the mooring deployed upstream of the comet over 17 days of recordings clearly demonstrate the effect of the semidiurnal tide in the high-frequency variability of currents and sediment resuspension. Taken together, these geomorphological, oceanographic and sedimentary parameters provide a clearer picture of those complex seafloor sedimentary structures that seem to result from the interaction of the DWBC with remobilized carbonated outcrops. Our observations also suggest that those comets initially formed under higher hydrodynamic conditions than those recorded today.

How to cite: Blin, P., Loncke, L., Durrieu de Madron, X., Dupont, P., Pairaud, I., Zaragosi, S., Fauquembergue, K., Basile, C., and Diadem, S. T.: Investigation of sedimentary structures associated with the Deep Western Boundary Current in French Guiana (Demerara Plateau), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18223, https://doi.org/10.5194/egusphere-egu24-18223, 2024.

EGU24-19123 | Orals | GM9.6

Results of high-resolution acoustic studies in Eastern Gulf of Finland 

Leonid Budanov, Alexander Sergeev, Alexander Chekulaev, Igor Neevin, Vladimir Zhamoida, and Daria Ryabchuk

Studies were carried out in three key areas in the eastern Gulf of Finland during joint cruises of the A.P. Karpinsky Russian Geological Research Institute and the Shirshov Institute of Oceanology of the Russian Academy of Sciences in 2023. Multibeam echosounding, sub-bottom profiling, and various sediment sampling techniques were performed, and a significant amount of new geological and geophysical data was collected. Analyses of seismic sections, supported by sediment sampling data and a digital elevation model (DEM) of the sea floor, allowed for the revelation of six acoustic unions (AU) which are divided by reflecting interfaces and have unique acoustic waveforms. The sediments of the AUs were developed in different stages of deglaciation and in the postglacial period of the Late Pleistocene - Holocene. A complex analysis of collected and archived data allowed for the construction of DEMs of buried paleo-relief surfaces. Both the sea floor and paleo-relief DEMs allowed for the mapping and discovery of geomorphological features of landforms specific to the study area, such as submerged end moraine, drumlins, eskers, De Geer, etc. The studies provide new data on the Gulf of Finland basin deglaciation and establish sedimentological processes, features, and the impact of exogenous processes on the geological environment.

How to cite: Budanov, L., Sergeev, A., Chekulaev, A., Neevin, I., Zhamoida, V., and Ryabchuk, D.: Results of high-resolution acoustic studies in Eastern Gulf of Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19123, https://doi.org/10.5194/egusphere-egu24-19123, 2024.

EGU24-19617 | ECS | Orals | GM9.6

The Zabargad Fracture Zone and Mabahiss Deep, Northern Red Sea: new insights from new high-resolution bathymetric mapping 

Margherita Fittipaldi, Adrien Moulin, Daniele Trippanera, Nico Augustin, Froukje van der Zwan, Laura Parisi, and Sigurjon Jonsson

The Red Sea axis hosts an oceanic ultra-slow spreading ridge which is generally arranged into right-stepping segments. The largest apparent ridge offset runs at the transition between the northern and central Red Sea, amounts to ~ 100 km along a N-S trend, and is referred as to the Zabargad Fracture Zone (ZFZ). The ZFZ separates ridge segments characterized by exposed oceanic crust (the Mabahiss “Deep” in the north and the central Red Sea further south), but its nature and precise geometry are debated owing to the extensive Miocene evaporites that cover the basement structures. The ZFZ is the location of the most intensive seismic activity in the northern Red Sea, with a reported historical magnitude 6.5 earthquake. Due to its proximity with coastal communities, the ZFZ thus potentially poses a significant hazard. In order to better characterize the seismic potential of the ZFZ, we collected new high-resolution bathymetric data of the Mabahiss Deep and ZFZ, and use them to map the tectonic structures over both exposed-basement and salt-covered areas.Our findings reveal typical slow spreading-ridge features in the Mabahiss area, such as an axial MORB volcano with a summit caldera located in the middle of a 9 x15 km axial valley bounded by up to ~300-m-high normal fault escarpments. In addition, our results highlight a highly deformed salt cover in the ZFZ area and several salt diapirs outcropping near its eastern edge. The orientation of salt-deformation fabrics records a clear rotation from rift-parallel to rift-normal in the vicinity of the ZFZ, suggesting a potential control by underlying basement structures. Overall, the deformed area indicates that the ZFZ is a 70 km long and 15 km wide fracture zone, oriented roughly N-S, and potentially consisting of several NE-SW rift-perpendicular faults. These new data provide the first step to characterize the geometry and seismic potential of the ZFZ and to constrain the segmentation of the ridge axis in the northern Red Sea, emphasizing the importance of continued research to improve our understanding of this complex region and its potential impact on coastal communities.

How to cite: Fittipaldi, M., Moulin, A., Trippanera, D., Augustin, N., van der Zwan, F., Parisi, L., and Jonsson, S.: The Zabargad Fracture Zone and Mabahiss Deep, Northern Red Sea: new insights from new high-resolution bathymetric mapping, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19617, https://doi.org/10.5194/egusphere-egu24-19617, 2024.

EGU24-20450 | Orals | GM9.6

Extensive exposure of the Chukchi Shelf since the last deglacial 

Yanguang Liu, Song Zhao, and Jiang Dong

Ice sheets and ice shelves play an important role in Earth’s climate system during the late Quaternary. The cyclic growth and decay of continental ice sheets can be reconstructed from the history of global sea level. However, sea level estimates for the period of ice-sheet retreat after the Last Glacial Maximum (LGM) are full of uncertainties, especially in the Arctic Ocean. For example, the Bering Strait was a land bridge during the LGM, when sea level was ~130 m lower than today. Based on records from multiple sites, we suggest that the Chukchi shelf may not have been widely submerged during the late and/or post-Last deglacial.

The initial evidence comes from the less sea ice coverage and abnormal sediment accumulation rates during the early Holocene, and abnormally sedimentation rates have been observed in many records. Some cores have a very high sedimentation rate, on the contrary, there are hiatus in some records, even if a considerable number of differences due to chronological drift have been evaluated.

There were unusual sand layers before 8.2 ka, which can be associated with a rapid input of IRD in our proposed R11 core, accompanied by a fierce change in organic matter content. The coarse particle size indicates that it may be dominated by ice transition at this time.

The organic carbon record on the Chukchi sea-continental shelf/margin suggests that this model is attributed to ICD (Ice Complex Deposit), which results from the large-scale degradation and thawing of permafrost due to sea-level rise after the ice age. The early Holocene low sea source organic matter and low sea ice cover recorded in R09 indicate that the sea level rise is a long process, and the εNd, which represents the Pacific inflow also has a long-term lifting, during which part of the continental shelf may still be exposed to the surface or even covered by ice caps.

This situation continued until the last discharge of the Laurentide ice sheet during the 8.2 ka period, and the global sea level stabilized. After that, the maximum flux of PW inflow occurs between 6.0~ 5.0 ka. However, this situation may only be applicable in narrow and shallow continental shelves because we found new sedimentary records on the Chukchi borderland that show significantly different sedimentation rates compared to the cores raised from adjacent shelf. In that area, the sedimentation rate starts to rapidly decrease even though the water depth only increased by over hundreds of meters. Besides non-linear ages, the sedimentary records of the Chukchi borderland typically contain hiatus, and also include high IRD content and strong environmental changes. Furthermore, our neighboring region's records show significantly different carbonate content storage conditions compared to those from the Chukchi margin, which is similar to the micro fossil barren observed in the sedimentary record of the Chukchi plateau. Therefore, we need to be more cautious and consider the global perspective when studying the sedimentological environment of the Chukchi Sea and its continental margin.

How to cite: Liu, Y., Zhao, S., and Dong, J.: Extensive exposure of the Chukchi Shelf since the last deglacial, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20450, https://doi.org/10.5194/egusphere-egu24-20450, 2024.

EGU24-20562 | ECS | Orals | GM9.6

From Ice to Deep Water Fans: Seismic Geomorphology Reveals the Story of a Glacigenic Basin Floor Fan offshore West of Shetland 

Simona Caruso, Vittorio Maselli, Brice Rea, and Matteo Spagnolo

This study uses 3D seismic reflection data to conduct a detailed seismic geomorphology analysis of a portion of a glacigenic basin fan system located offshore West of Shetland in water depths greater than 1000 m.

These deposits lie downslope from a gully system linked to the Foula wedge trough mouth fan, with both systems remarkably preserved at the present-day seafloor. While the seafloor morphology has received extensive attention in existing literature, the basin fan system subsurface structure, particularly its 3D geometry and distribution, remains less understood. This study lifts the veil, unveiling its basal surface and internal architecture in unprecedented detail. The 3D seismic characterisation reveals a complex basin channel network with linear, diverging erosional features and distinctive terminal lobes. These lobes exhibit stacked and backstepping patterns. The seismic geomorphology showcases features indicative of both debris flows and turbidites. This intricate interplay suggests a complex shelf-to-basin sediment transport and deposition mechanism.

The integration of this newfound evidence with existing regional bathymetry, helped pinpoint the source of the main basin distributary channels to two of the downslope gullies.  This suggests that, initially, high energy flows remained somewhat confined within the basin area allowing erosion. These local-scale insights shed light on different sediment delivery processes and their impact on basin fans development. Ultimately, these findings contribute to a more comprehensive understanding of the Foula wedge large-scale dynamics, particularly the influence of meltwater pulses driven by paleo-morphology, substrate characteristics, and unique ice-sheet behaviour during the Pleistocene glaciations.

How to cite: Caruso, S., Maselli, V., Rea, B., and Spagnolo, M.: From Ice to Deep Water Fans: Seismic Geomorphology Reveals the Story of a Glacigenic Basin Floor Fan offshore West of Shetland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20562, https://doi.org/10.5194/egusphere-egu24-20562, 2024.

EGU24-22150 | ECS | Posters on site | GM9.6

Feather-like submarine channels: a unique imprint of overbank flows imaged by 3D seismic data 

Aurora Machado Garcia, Benjamin Bellwald, Sverre Planke, Ingrid Anell, Reiden Myklebust, and Ivar Midtkandal

We document for the first time the extensive occurrence of “feather-like channels” in the 19000-year-old glacigenic submarine strata in the North Sea Fan (NSF). We describe these features in the uppermost deposits of the NSF, predominantly on the surface that marks the end of the period of shelf-edge glaciation, using over 14000 km2 of high-resolution 3D seismic reflection data (vertical resolution of 2m and bin size of 6.25 x 18.75m). 

These channels are a few 10’s of meters wide and depths on the limit of seismic resolution (~2 m). They lack clear cross sections, mostly presenting as disruptions in the otherwise readily traceable reflections, which make them easier to identify in amplitude maps rather than structure maps and seismic profiles. These “feather” channels occur exclusively in association with larger, deeper channels. The “feathers” diverge from the margins of the main channel, forming an obtuse angle with the flow direction of the main channel, becoming progressively sub-parallel further downstream, similar to a bird’s feather, with the divergence from the main channel axis in the downstream direction. They run for varied distances, as short as a few 100’s of meters and up to 7 kilometers. It’s also important to highlight that they occur extensively throughout the surface, with a small spacing of 10’s of meters between each other.

Similar features have been described by others as lineations formed at the base of debris flows. This was credited to circular depressions found at the end of such lineations and the fan shape that those features would create at the end of a main channel body. This description is clearly different from what we have described in this study, where both circular depressions and fan-shaped terminations were absent. Here, we interpret them as the record of overbank flows from the main channel, due to their geometry and dimensions, representing the large pulses meltwater coming from the shelf.

Our investigation into the “feather-like channels’’ reveals a unique seismic geomorphology, in a well understood palaeogeographical setting. The exclusive association of these channels with larger, deeper counterparts, their small spacing, and varied distances emphasize their pervasive nature. This research not only refines our understanding of submarine sedimentary dynamics, but also highlights the indispensable role of high-resolution 3D seismic data in understating the subsurface.

How to cite: Machado Garcia, A., Bellwald, B., Planke, S., Anell, I., Myklebust, R., and Midtkandal, I.: Feather-like submarine channels: a unique imprint of overbank flows imaged by 3D seismic data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22150, https://doi.org/10.5194/egusphere-egu24-22150, 2024.

The submarine channel, also known as submarine canyon, is a narrow and long negative terrain 
that cuts to the shelf or slope and widely developed on the global continental margins. There are 
numerous factors in forming channels, including climate change, topography, sediment sources and 
grain size, and sea level change. However, for high latitudes, especially in the Antarctic region, the 
controlling factors of the formation and evolution of the channel are still poorly understood. In this 
study, we conduct a systematic analysis of the channels in various regions of the Antarctic 
continental margin with the aim of identifying the differences of the channels between the East and 
West Antarctic continental margins and associated controlling factors. We identified 2126 channels 
on the Antarctic continental margin based on IBCSO V2 data (International Bathymetric Chart of 
the Southern Ocean Version 2). The submarine channels and their possible factors in six regions 
(Weddell Sea, Amundsen Sea, Ross Sea, Wilkes Land, Prydz Bay and Dronning Maud Land) are 
statistically analyzed. Quantitative analysis shows that there are obvious differences in the 
geomorphology of submarine channels between the East and West Antarctic continental margin. 
First, consider the differences in the landscape. The shelf is narrower on the east and wider on the 
west. There are prominent troughs running across the broad shelf. West Antarctica has a gentler 
slope gradient than the East Antarctic continental margin, and the ice velocity is much faster. Second, 
submarine channels on the West Antarctica continental margin are longer and wider in cross section, 
with most large-scale channels extending beyond the slope foot, whereas submarine channels on the 
East Antarctica continental margin are deeper but shorter, with fewer channels. We consider that 
shelf width, slope gradient, trough and ice velocity can control sediment transportation and thus 
affect the size of channels. Channels are longer and wider on the margin with wide shelf, prominent 
trough and fast ice velocity, while they are shorter and deeper on the margin with steep slope.

How to cite: Huang, H. and Huang, X.: Quantitative analysis of Antarctic channel distribution and the role played by continental geomorphology in channel evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22420, https://doi.org/10.5194/egusphere-egu24-22420, 2024.

EGU24-140 | ECS | Orals | GM6.3

Controls on hydrological connectivity in the Lower Oder river and its floodplain  

Hanwu Zheng, Doerthe Tetzlaff, Jonas Freymueller, Jana Chmieleski, Akpona Okujeni, and Chris Soulsby

Hydrological connectivity affects many ecological services (e.g., water storage, nutrients deposition, habitat provision) of landscape systems, especially in river-floodplain systems which generally show great variations at different spatial-temporal scales. Here, we present insights from the Oder river-floodplain system in Germany. Multiple potential contributions to flood plain inundation (i.e., from the river, rainfall, and groundwater) make this system complex and understanding the dynamics of connectivity and its controlling factors is still limited which has implication for floodplain management. We used a remote sensing data cube of harmonized Landsat and Sentinel-2 imagery to derive a temporally dense, 8-year NDWI times series to infer patterns of floodplain inundation and river-floodplain connectivity in two contrasting polders in the Lower Oder Valley National Park. Continuous wavelet transformation was used to investigate which timescale the hydrological variables present the pronounced variations. Wavelet coherency was employed to capture the factors contributing the hydrological connectivity. The upstream Polder A (14.4 km2) was extensively flooded for prolonged periods most winters and its strong seasonality was primarily driven by winter water levels in the river Oder (through 2 floodgates). Inundation of the downstream Polder 10 (17.7km2) was lower and had less marked seasonality, which reflected the impact of flood attenuation by storage in Polder A upstream, but also the greater connectivity (via 10 flood gates) to the Oder and a functional network of channels which facilitated rapid drainage. In Polder A, secondary periods of transient inundation could also occur in response to local intense summer rainfall, this was less evident in Polder 10. Groundwater recharge in and around Polder A is primarily induced by floodwater, whilst Polder 10 also reflects the influence of local rainfall-driven recharge. The hydrological connectivity regimes of the two polders showed marked inter-annual variation, largely dependent on flows from the upper Oder catchment. Understanding the hydrological connectivity in this system is important for sustaining and managing valuable wetland habitats within the National Park. Given projected climate change for this region and possible management alterations to the flow regime of the Oder, potential implications for these habitats needs urgent attention.

How to cite: Zheng, H., Tetzlaff, D., Freymueller, J., Chmieleski, J., Okujeni, A., and Soulsby, C.: Controls on hydrological connectivity in the Lower Oder river and its floodplain , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-140, https://doi.org/10.5194/egusphere-egu24-140, 2024.

Sand transport and its deposition in deep marine basins is controlled by diverse climatic, tectonic, physiographic and oceanographic processes. Disentangling the impact of each of these drivers on the sedimentary record is a fundamental challenge in the study of source to sink systems. In this study, we investigate seismic and boreholes data using statistical and spectral analysis approaches to identify the factors controlling sand deposition in the deep Levant Basin (Eastern Mediterranean) during the Pliocene-Quaternary (PQ). We interpret the sand content in boreholes from Gamma Ray (GR) logs and identify two major trends in sand/shale ratio. On a million-year scale, we demonstrate that since the Early Pliocene (5.3 Ma) sand content gradually increased until it formed a ~100 m thick widespread sand sheet at the top of the section. On a shorter time-scale, we identify oscillations in sand content depicting statistically significant power of periodic components at the 350-450, 90-150, and 10s ka bands. The long-term increase in sand content reaching the deep Levant Basin is interpreted as a result of the Nile Delta propagation, which had continuously shortened the distance between the Nile delta edge that became the source of sand, and the deep Levant Basin. The superimposed short-term oscillations are interpreted as Milinković cycles that produced hydrologic oscillations of water and sediment discharge into the Eastern Mediterranean Sea by the Nile River. This demonstrates the hydroclimatic control on sand deposition in the deep Levant Basin. Our observations are consistent with the development of a submarine channel system along with the accretion of the Nile delta, which may have served as a pathway for sand delivery via high energy turbidite currents that reached the Levant Basin.    

How to cite: Sirota, I., Ben Dor, Y., and Gvirtzman, Z.: Short-term climatic oscillations versus long-term delta propagation: what controls sand transport into the deep Levant Basin since the Pliocene? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1886, https://doi.org/10.5194/egusphere-egu24-1886, 2024.

EGU24-3050 | Posters on site | GM6.3

Alluvial fan river incision during climatic change: new clue from an experimental erosion device 

Valeria Zavala, Stéphane Bonnet, and Sebastien Carretier

At the foot of a mountain range, rivers sometimes cut several hundred meters into alluvial fans. This incision reflects a transition from aggradation to erosion, possibly as a result from a major change in external conditions. The incision of rivers into alluvial fans has often been interpreted as the result of a deficit in sediment supply during the transition from glacial to interglacial periods, associated with an increase in water discharge. However, such incision is not observed along all mountain fronts, nor at the mouth of all the catchment areas along a same mountain range. The conditions that lead to incision of alluvial fan are still poorly  quantified.

We tackle this question by means of a laboratory-scale device in which a 40x60cm block is uplifted at a constant rate under artificial precipitation, forming a mountainous landscape. Additionally, the products of its erosion are deposited on a plateau surrounding the block, forming alluvial fans and a piedmont. We carried out 8 experiments (700 to 900 min-long) in which the rate of precipitation was either constant or alternated between periods of low precipitation P1 and high precipitation P2, of variable duration from 10 to 40 minutes. The topography of experiments was monitored over time by using a high-resolution laser sheet. Sediment and water fluxes Qs and Qw at catchments’ outlet were computed over time from topographic and rainfall data.

We observe a variability in the relationships between Qs and Qw between catchments, due to some spatial heterogeneities in precipitation rate and migration of ridgelines. Qs and Qw vary in phase with precipitation cycles, but with different amplitudes between catchments. When the system reaches a state of dynamic equilibrium, the piedmont is a bypass for the sediments. Its average slope is inversely proportional to the average rainfall rate.

Only 8 deep incision events occurred at the outlet of certain catchments in the piedmont in all our experiments. We show that these incisions only occur for a certain slope threshold during dynamic equilibrium, and for a certain percentage decrease in sediment concentration d(Qs/Qw). These incisions never occurred in the two constant precipitation experiments and only initiated during P2 precipitation periods.

On the basis of the slope of the alluvial fans S at dynamic equilibrium, we calibrated a sediment transport law for the piedmont in the form of an excess shear stress power law. Using this law, we used a Monte Carlo approach to simulate many pairs (S , d(Qs/Qw)), for which we calculated the ratio between sediment transport capacity and flux, and the Froude number. We show that the incisions occurring in our experiments correspond to a transition towards an excess of transport capacity, for Froude numbers approaching 1. It has recently been shown that a river bed becomes unstable for such values, driving incision and knickpoints. Our experiments and theoretical analysis are consistent with this interpretation, which explains why incision occurs rarely in our experiments. These results offer new perspectives for quantitatively interpreting the incisions observed in nature in terms of paleo-fluxes Qs and Qw.

How to cite: Zavala, V., Bonnet, S., and Carretier, S.: Alluvial fan river incision during climatic change: new clue from an experimental erosion device, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3050, https://doi.org/10.5194/egusphere-egu24-3050, 2024.

Sediment plays a key role in modulating bedrock channel response to tectonics and climate. By armoring the channel bed, sediment cover can dampen the topographic expressions of these perturbations in the channel profile. A variety of models have been developed to capture the influence of sediment cover on bedrock channel evolution, including the Stream Power with Alluvium Conservation and Entrainment (SPACE) model (Shobe et al., 2017), which builds on the standard stream power model by conserving the mass eroded from the channel bed and allowing it to be transported downstream or deposited in an alluvial layer. The model assumes that channel width scales with discharge rather than allowing for a dynamically evolving channel width. However, sediment may play an important role in the channel’s evolution by abrading the sidewalls and widening the channel in order to accommodate increased sediment flux, which may in turn reduce vertical incision rates. Here we present a modified version of the SPACE model that explicitly calculates channel width in order to test how sediment cover influences channel widening and steepening in response to climate and tectonic perturbations in 2D and at the landscape scale. Like the original SPACE model, our model is implemented using the Landlab toolkit, a python library for modeling earth surface processes. We use our model to explore how feedbacks between sediment production, sediment cover, and channel widening or narrowing may influence patterns and rates of incision during transient responses to changes in uplift and climate. We specifically test how sensitive vertical and lateral incision rates are to pulses of uplift under varying sediment regimes. We also explore the influence of climate by varying precipitation rate. Our model offers an efficient method for modeling dynamic channel width and sediment dynamics that can be coupled with existing Landlab components to address a wide range of geomorphic problems in two dimensions.

How to cite: Guryan, G., Tucker, G., and Johnson, J.: Exploring the influence of sediment cover on bedrock channel slope and width responses to climate and tectonic perturbations , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4205, https://doi.org/10.5194/egusphere-egu24-4205, 2024.

EGU24-4447 | ECS | Orals | GM6.3

Linking connectivity to spatiotemporal variability in sediment dynamics and yield in glacierized, mountainous watersheds 

Mike Turley, Marwan Hassan, Andre Zimmermann, Maria Schaarschmidt, Olav Lian, and Pierre Friele

An understanding of catchment-scale processes and sediment dynamics is crucial for the informed and sustainable development of mountain communities. Given the steep topography, glacier retreat, and intensifying weather patterns due to climate change, many mountain towns face heightened vulnerability to geohazards. Studies show that as glaciers retreat, paraglacial processes typically lead to elevated sediment yields, exacerbating existing hazards. However, postglacial landscapes are dynamic, complex, and heterogeneous systems shaped by a variety of processes, and no two systems are the same. The efficiency in which glacial sediments are reworked and transported to and through river systems (connectivity) varies over time and space. In this study, we investigate the link between landscape history, sediment (dis)connectivity, and postglacial sediment dynamics in a glacierized, mountainous catchment in Southern British Columbia. We begin by mapping the geomorphology, identifying sediment sources, storage landforms and transfer processes. Subsequently we employ morphometric analysis and landform mapping paired with age estimates, to quantify sediment yield. These results are compared to historical channel changes and estimates of structural connectivity to better understand the variation in postglacial sediment dynamics. By integrating diverse datasets and methodologies, we are able to estimate the variability in sediment yield and changing relative contributions of sediment sources at a range of spatial and temporal scales. Preliminary results of this work shed light on and underscore the need for additional studies that investigate long-term (e.g., postglacial) changes in sediment connectivity. Such research can inform decision-making in landscapes that are rapidly changing and experiencing deglaciation.

How to cite: Turley, M., Hassan, M., Zimmermann, A., Schaarschmidt, M., Lian, O., and Friele, P.: Linking connectivity to spatiotemporal variability in sediment dynamics and yield in glacierized, mountainous watersheds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4447, https://doi.org/10.5194/egusphere-egu24-4447, 2024.

EGU24-4449 | Posters virtual | GM6.3

Fluvial fans as stratigraphic recorders of suborbital climate cyclicity: an example from the Lima fluvial fan in Peru 

Willem Viveen, Jorge Sanjurjo-Sanchez, Gustavo Bravo-Lembcke, and Rodrigo Uribe-Ventura

Fluvial fans, as opposed to alluvial fans, have only been recognised over the past two decades as important end members in the classification of alluvial-fluvial landforms. There is still a lack of knowledge regarding the factors driving their formation, their geomorphology, stratigraphic build-up and significance as quantitative recorders of terrestrial (sub)orbital climate change. Here, we present a stratigraphical and grain-size analysis of ~5,000 gravel clasts of the Lima fluvial fan in Peru. An age-depth, and derived sedimentation rate, model was constructed by means of Monte Carlo Markov Chain iterations of thirteen, new luminescence ages of the fluvial fan. Our data showed near-continuous sedimentation from 121.7 ± 4 ka at the base of the exposed stratigraphic section at 10 m above sea level (asl) until 6.3 ± 1.6 ka at the top (62.5 m asl). Stratigraphical unconformities, both erosional and non-erosional, systematically coincided with the initiation of coarsening upward sequences as shown by increases in the D50 grain size. The unconformities and coarsening-upward sequences, in turn, coincided with both orbital and suborbital pluvial periods, as known from Peruvian lake and speleothem records. The precession cycle was the primary driver for increased precipitation, runoff and modelled sedimentation rates during the lower half of the last glacial period, coinciding with the Ouki and Salinas pluvial periods. Imprinted on the precession cycle, one-to-five-ka long suborbital pluvial periods constituted a secondary driver, coinciding with the stratigraphical unconformities and increases in D50 grain size. Throughout the Salinas wet phase, the amplitude of the precession cycle diminished and, at the end of it, the precession cycle ceased altogether to be a driver for fluvial sedimentation. From 50 ka onwards, stratigraphical unconformities, coarsening upward cycles and an increase in sedimentation rate systematically coincided with the onset of the Atlantic Heinrich events, which have been recognised as three-to-five-ka long pluvial events in the aforementioned lake and speleothem records. Most fluvial sedimentation events have been recognised in fragmentary records of other fluvial systems in Peru, but the Lima fan constitutes the most complete fluvial record to date. As such, the Lima stratigraphical record shows the value of fluvial fans as quantitative recorders of fluvial landscape change due to last glacial climate cyclicity.              

How to cite: Viveen, W., Sanjurjo-Sanchez, J., Bravo-Lembcke, G., and Uribe-Ventura, R.: Fluvial fans as stratigraphic recorders of suborbital climate cyclicity: an example from the Lima fluvial fan in Peru, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4449, https://doi.org/10.5194/egusphere-egu24-4449, 2024.

Since the early 2000s, the development of the Source-to-Sink (S2S) approach improved the understanding of variations in the sedimentary signal and its controlling factors within coupled catchment-sedimentary system. However, S2S study remains difficult, as the data and time scales of the distinct compartments of the system may be incompatible, poorly resolved or even lacking. The combined quantification of sediment budget in both the catchment’ and sedimentary basin’s parts of the system is a way to address this problematic.

The aim of this study is (i) to jointly measure erosion and sediment deposition across an entire S2S system, and subsequently (ii) discuss the influencing factors and the mode of signal propagation. The study focuses on the system of Sithas (Corinth rift, Greece), where numerous geomorphologic markers (e.g., marine terraces) provide constrains to quantify eroded volumes, and a large offshore dataset is available to establish well-constrained sedimentary budget.

To achieve this, we updated an age model for the last 800 ka. We then restored the volumes of sediment eroded in the catchment and quantified the volumes of sediment deposited offshore to estimate fluxes of sediments from the source and the sink during the last 800 ka Quaternary climatic cycles. We also compared these results with a multi-regression empirical model estimating suspended sediment loads (BQART).

Erosion (source) and sediment (sink) fluxes have shown a gradual increase since 800 ka: from 3km3/Ma for the source and from 1. to 75. km3/Ma in the deep-sea fan (sink). This overall increasing trend is superimposed by cyclic variations, in both erosion and deposition signals. Significant increases in fluxes are observed over periods of around 12 ka every 120 ka (at circa 10, 120, 230 and 340 ka), which are followed by a progressive decrease. They coincide respectively with high sea levels according to the global eustatic curve (odd Marine Isotopic Stages). Surprisingly, the peaks of fluxes in deposition (sink) are preserved prior to the peaks of fluxes in erosion (source) with a time lag of around 30 ka. The comparison with BQART fluxes also shows the significant influence of the catchment size and the climatic factors such as temperature and precipitations in modulating the signal propagation.

These observations suggest that even for small, coupled catchment-deep sea fan system, the signal propagation is not straightforward, and thus deserves much more attention in future works.

How to cite: Deiss, N., Rohais, S., and Regard, V.: Source-to-Sink signal propagation in a coupled catchment-deep-sea fan system: the Sithas example from the Corinth Rift (Pleistocene, Greece), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5232, https://doi.org/10.5194/egusphere-egu24-5232, 2024.

EGU24-7410 | Posters on site | GM6.3

Testing the predictive capability of the Index of Connectivity (IC) on a 2022 debris-flow event considering the spatial variability of the forcing 

Toni Himmelstoss, Jakob Rom, Diana-Eileen Kara, Sarah Betz, Moritz Altmann, Florian Haas, Michael Becht, and Tobias Heckmann

Sediment connectivity is an important property of geomorphic systems reflecting the potential to route material through themselves and hence modulating the propagation of geomorphic changes. While the relevance of the concept is clear, connectivity cannot be measured directly and the discussion on the best methods to quantify connectivity is still ongoing. Probably the most frequently used approach is based on the index of connectivity (IC) as it was developed by Borselli et al. (2008) and later adapted by Cavalli et al. (2013) for alpine catchments. This index aims at quantifying the structural connectivity that is governed by the spatial configuration and properties of system components. Nevertheless, the predictive capabilities of this index for functional connectivity, i.e. the actual transfer of sediment between the system components, have not been conclusively validated with field data. Most importantly, previous studies have, to our knowledg