EGU General Assembly 2024  

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 (U_EF and Mo_EF) 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 (Cd_EF and Zn_EF) 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 (δ¹³C_org and δ¹³C_carb) records and palynostratigraphy. Notably, a long-term positive δ¹³C trend is identified, which is interrupted by pronounced 4–5‰ N-CIEs in δ¹³C_org and δ¹³C_carb 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.

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 2^nd 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.

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.

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.

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.

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 δ¹³C_TOC 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 δ¹³C_TOC shift 1a; III) positive rebound 1a; IV) negative δ¹³C_TOC 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.

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.

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 δ¹³C_orgshow 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.

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.

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.

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.

The total Hg (Hg_T) 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 Hg_T data. Most studies, therefore, employ a degree of normalization to a Hg “host” (Hg_T/TOC, Hg_T/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.

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.

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 (δ¹³C_org) 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.

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.

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.

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/¹⁸⁸Os_i) 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.

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.

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.

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.

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.

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.

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.

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 PO₄^3-). 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.

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 (REY_SN) patterns that are typical of (modern) hydrogenetic FeMn deep-sea nodules and crusts, suggesting a seawater-derived origin. Typical REY_SN features include strong positive Ce_SN anomalies due to the oxidation of Ce³⁺ to Ce⁴⁺ on (hydr)oxide surfaces and a negative Y_SN 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 δ^98/95Mo (-0.97 to -0.56 ‰) and δ^238/235U (-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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

      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.

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.

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.

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 evolution^1-5. Carbonate mineral compositions reflect the environmental conditions under which they were formed^4,5 .

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 abiotically^1-4. 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.

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.

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.

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.

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.

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.

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.

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.

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 δ³⁴S_SO4 range between 20.76‰ to 23.42‰ and δ¹⁸O_SO4 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.

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, U^K₃₇’, 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 U^K₃₇’ 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.

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.

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.

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.

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.

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.

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.

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.

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 U^K´₃₇ biomarker-based proxies, with cross validation at distinct levels. To further constrain the SSS changes, we combined the TEX₈₆ and U^K´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 , δ¹⁸O_{O. 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-δ¹⁸O_{O. universa} values, we observe the dominance of the C_37:4 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.

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.

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.

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.

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.

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.

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.

Global warming poses a major challenge that humanity will face during the 21^st 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 12^th globally in CO₂ emissions (and 1^st 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.

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.

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.

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=R^a+bt_I*exp(cT_m), 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.

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.

          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.

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.

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.

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.

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.

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.

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.

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.

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 ear