Conventional neo-Darwinian theory views organisms as responsive to their environments on neontological timescales, and able to readily change size or shape due to selection pressures (as exemplified by the famous case of Galápagos finches). But since 1863, it has been well established that Pleistocene animals and plants show limited morphologic change in response to the glacial-interglacial cycles. Rancho La Brea tar pits in Los Angeles, California, preserves a large and diverse fauna from many well-dated deposits, spanning 37,000 years. Pollen evidence shows that climate changed from oak-chaparral about 37 ka to snowy piñon-juniper-ponderosa pine forests during the peak glacial about 18 ka, then returned to the modern chaparral since the glacial-interglacial transition. We have studied all the sufficiently abundant mammals (dire wolves, saber-toothed cats, giant lions, Harlan’s ground sloths, camels, bison, and horses) and all the common birds (28 species, ranging from eagles, hawks, vultures, condors, owls, to yellow-billed magpies, ravens, and Western meadowlarks). We found complete stasis in size and robustness as measured by the major limb bones in all 28 species. There was no significant response even at 20 ka to 18 ka, during the peak glacial period, when climate and vegetation were very different at La Brea. The larger species might be so wide-ranging and versatile that they would not respond to environmental changes, but this is inadequate to explain stasis in even the smallest birds, such as meadowlarks and burrowing owls. While the Galápagos finch model suggests rapid morphological change in response to environmental change, the fossil record shows that such small-scale changes are transient and do not accumulate to result in speciation.

How to cite: Prothero, D. R.: Patterns of Evolution in late Pleistocene Mammals and Birds from La Brea Tar Pits, California, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21959, https://doi.org/10.5194/egusphere-egu25-21959, 2025.

This research investigates the alongshore variability of shoreline and dune line responses to storm events and long-term changes on Culatra Island, located in the Algarve region of Portugal utilizing a combination of LiDAR data, satellite imagery, and numerical models (ShorelineS and SnapWave). Using a dune model based on Larson et al. (2016), integrated within the ShorelineS framework, to analyze the dynamic interactions between dune erosion, overwash by waves, and dune growth driven by aeolian (wind) transport. These interactions are critical in understanding the long-term and storm-induced changes in shoreline positions.

The calibrated ShorelineS model, supported by SnapWave's wave data, reveals that longshore transport gradients are the predominant drivers of shoreline change, significantly influenced by southeast prevailing waves, shallow active heights at the ebb delta, and the presence of the western breakwater.

By simplifying these processes into a 1D sand balance equation, where dune interactions are treated as source and sink terms, the model effectively captures several key dynamics of coastal morphology. However, certain idealizations, such as the assumed dune vegetation lines and simplified coastal profiles, result in some processes, like overwash, not being fully represented.

To ensure the accuracy and reliability of the model outputs, extensive sensitivity analyses were conducted with parameters such as impact coefficient Cs, median grain size d50, wave output points distances, and sediment transport factor (qscal). Validation of the ShorelineS model against 2011 DEM data and satellite trends reveals varying degrees of accuracy. For shoreline positions, the model demonstrates a strong positive correlation with DEM data (R² = 0.78) and even better alignment with satellite trends (R² = 0.85). However, the model's predictions for dune positions exhibit higher variability and weaker correlations with DEM data (R² = 0.47), indicating significant discrepancies. Interestingly, the model shows a stronger positive correlation with satellite trends for dunes (slope = 0.96).

The research identifies several key factors contributing to alongshore variability in dune and shoreline responses during storm events, including initial berm width, storm duration, wave height, and cumulative sediment transport due to dune erosion. Notably, dune responses exhibit higher sensitivity to these coastal parameters compared to shoreline responses, with cumulative sediment transport being a significant driver of dune change (Corr: -0.86).

Overall, this study highlights the critical need for integrating comprehensive modeling approaches with empirical data to inform coastal management practices. It offers a robust framework for future research aimed at enhancing the sustainability and resilience of coastal environments.

How to cite: Dabu, R., Roelvink, D., van Dongeren, A., and Garzon, J.: Alongshore Varying Dune Retreat at a Barrier Island, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-770, https://doi.org/10.5194/egusphere-egu25-770, 2025.

As decision support methods (including as Artificial Intelligence supported decision making) progress, new ways and frameworks are emerging to enhance our understanding of sediment transport processes (via improved monitoring), but also better modeling those phenomena. This study offers a preliminary view of how deep learning models can link with real-time data from instrumented sediment particles, to predict the risk of bed surface destabilization in channels and rivers, which can lead to infrastructure scour. 
Specifically, three deep learning models are analyzed, herein: a) Long Short-Term Memory (LSTM), b) Gated Recurrent Units (GRU), and c) Transformers. These models were compared according to their accuracy, computational efficiency, and suitability for real-time applications.This study integrates data from specifically designed sediment stability monitoring sensors [1-3], with three deep learning models to predict the possibility that sediment is transported along the bed surface of the river [4], in real time. This is important for a series of applications, such as flood risk management, assessment of hazards to hydraulic infrastructure and water resource management, helping achieve resilient and sustainable development under a changing climate change. Future studies can explore further improving the efficiency of sensor enabled novel hydroinformatics approaches.

References
[1] Al-Obaidi, K., Xu, Y., & Valyrakis, M. (2020). The design and calibration of instrumented particles for assessing water infrastructure hazards. Journal of Sensor and Actuator Networks, 9(3), 36.
[2] AlObaidi, K., & Valyrakis, M. (2021). Linking the explicit probability of entrainment of instrumented particles to flow hydrodynamics. Earth Surface Processes and Landforms, 46(12), 2448-2465.
[3] Al-Obaidi, K., & Valyrakis, M. (2021). A sensory instrumented particle for environmental monitoring applications: Development and calibration. IEEE Sensors Journal, 21(8), 10153-10166.
[4] Valyrakis, M., Diplas, P., & Dancey, C. L. (2011). Prediction of coarse particle movement with adaptive neuro‐fuzzy inference systems. Hydrological Processes, 25(22), 3513-3524.

How to cite: Mavris, I. and Valyrakis, M.: Towards Enhancing River Bed Stability Assessment: A Comparative Study of LSTM, GRU, and Transformer Predictive Models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2032, https://doi.org/10.5194/egusphere-egu25-2032, 2025.

The increasing frequency and magnitude of extreme weather events across the Earth's surface results in increasing pressure for living organisms and their habitats, including those in aquatic ecosystems. The main focus of this study is on the resilience of Mediterranean mussels (Mytilus galloprovincialis) against pronounced hydrodynamic stresses that may be experienced more frequently compared to the past. These mussels can be typically found in Mediterranean coasts and estuaries (such as in Greece, Spain, Italy, and Portugal), and they are also extensively farmed in the open sea using aquaculture practices. As such, they are of particular interest given their economic significance for Mediterranean countries, as well as their ecological role (offering significant ecosystem services as "ecosystem engineers", such as coastal protection).
The hydrodynamic stress of Mediterranean mussels is herein assessed indirectly using appropriately designed wave-flume experiments and analyzing video observations of the effects of wave motions of different characteristics on the Mediterranean mussels. For these experiments we embed specialised sensors to these mussels so they can record even minute displacements and changes in their orientation [1, 2]. Specifically, small, medium, and large mussels are exposed to two different configurations (similar to earlier studies [3]) on the surface of an artificial seabed, over which different wave fields are traversing. The movement of individual mussels was visually evaluated under varying wave intensities, transitioning from high to low energy and vice versa. These observations aim to determine the conditions and orientations under which these organisms drift relative to the wave flow direction or remain practically undisturbed. In the context of climate change and its impact on marine environments, this study may provide valuable insights into efforts to protect endangered marine species and enhance strategies for safeguarding aquaculture crops against damage caused by storms or significant wave fields.

References
[1] AlObaidi, K., & Valyrakis, M. (2021). Linking the explicit probability of entrainment of instrumented particles to flow hydrodynamics. Earth Surface Processes and Landforms, 46(12), 2448-2465.
[2] Al-Obaidi, K., & Valyrakis, M. (2021). A sensory instrumented particle for environmental monitoring applications: Development and calibration. IEEE Sensors Journal, 21(8), 10153-10166.
[3] Curley, E.A.M., Valyrakis, M., Thomas, R., Adams, C.E., & Stephen, A. (2021). Smart sensors to predict entrainment of freshwater mussels: A new tool in freshwater habitat assessment. Science of the Total Environment, 787, 147586.

How to cite: Karagianni, E. and Valyrakis, M.: Resilience of Mediterranean Mussels to Hydrodynamic Stresses: Insights for Climate Change Adaptation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2045, https://doi.org/10.5194/egusphere-egu25-2045, 2025.

Gravity flow is a key sedimentary process in deep-lacustrine environments, with transitional flow deposits commonly occurring in both distal and proximal zones of the turbidite systems. These deposits are crucial to understanding the sedimentary dynamics of fine-grained deep-water sediments. The transitional deposits between turbidity currents and mud-rich debris flows are particularly important for advancing our understanding of fine-grained sedimentation processes and have significant implications for unconventional oil and gas exploration.

The aim of this study is to describe transitional-flow facies, interpret their flow evolution and depositional processes, and assess their impact on the differential accumulation of organic matter in a fresh-water syn-rift deep-lacustrine system. Data were collected from the 111.39-m-thick Eocene  lacustrine oil-prone source rock succession, penetrated by the two wells in the Qibei Sub-sag, Bohai Bay Basin, China. Nine sedimentary facies were identified in the studied fine-grained succession, with various internal sedimentary structures (e.g., ripple cross lamination, low-angle cross lamination, wave lamination, parallel lamination, graded structure, deformed structure, and homogeneous structure) reflecting the dynamics of sedimentary processes in a deep-lacustrine depositional lobe distal environment. Millimeter-scale logging defined 5 bed types based on 2383 measured and recorded beds, with inferred transitional flow deposits exhibiting distinctive stacking patterns, from coarser grained turbidites to fine-grained debrites. A wide range of transitional-flow facies are recognized and can be assigned to turbulence-enhanced transitional flow, lower transitional plug flow, upper transitional plug flow and quasi-laminar plug flow. Despite the predominance of finning upward grain size trends, sedimentary structures in these heterolithic deposits may stack in varying orders, reflecting different flow dynamics.

The vertical facies trends of transitional flow deposit provide insights into the longitudinal flow evolution of flows, which were initially turbulent, but became increasingly laminar through deceleration and fine-grain entrainment. The assimilation of the lake-bottom mud into the density flows likely played a key role in modulating flow turbulence, helping to explain the common occurrence of transitional-flow facies indicated by sedimentological features such as sheared flame structures and deformed mud intrusions, which suggest interaction between the flow and the muddy lake floor.

Lacustrine organic matter was delivered to the lake floor by continuous settling, whereas terrestrial organic matter was transported via sediment density flows. The deep-lacustrine background mudstone is dominated by Type II₁ kerogen, whereas the quasi-laminar plug flow mudstone is dominated by Type II₁ and II₂ kerogen, turbulence-enhanced transitional flow and lower transitional plug flow mudstones are dominated by Type II₂ and III kerogen. These observations challenge the view that mud accumulates only from suspension fallout in distal basin-floor environments. This study suggests that composition, texture, and organic matter types of mud-dominated deep-lacustrine mudstones vary predictably in response to changes in depositional processes. The results have broader applicability to other deep-lacustrine sedimentary systems, highlighting the dynamic nature of transitional flows. Detailed microtextural and compositional analysis, combined with rigorous geochemical parameters, is essential for the understanding of the source-rock potential of basinal mudstones and fine-grained organic-rich sediments more general.

How to cite: Wang, J., Zhao, J., You, Z., Pu, X., Liu, K., Zhang, W., Shi, Z., Han, W., and Wang, Z.: Flow transformation processes recorded in the Eocene early syn-rift deep-lacustrine fine grained sedimentary rock in the Qibei Sub-sag, Bohai Bay Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3094, https://doi.org/10.5194/egusphere-egu25-3094, 2025.

This study aims to simulate the sedimentary processes of marine (lake) to terrestrial transitional clastic rocks and quantitatively analyze the impact of geological control factors on stratigraphic integrity. Most sedimentary strata exhibit discontinuities of different scales, represented by both temporal and spatial incompleteness. Defining and quantitatively characterizing "stratigraphic integrity" is of great importance for accurate stratigraphic correlation, reconstructing the depositional history of geological periods, and guiding oil and gas exploration.

2D physical water tank experiments can realistically simulate geological processes such as erosion, transport, deposition, and reworking of clastic materials. These experiments allow for the calculation of stratigraphic integrity at any given location. In this study, a narrow 3D water tank was used to approximate the 2D sedimentary processes, simulating the entire sedimentary sequence of marine (lake) to terrestrial transitional clastic rocks and calculating stratigraphic integrity.

A transparent glass water tank (1.5m×0.5m×0.05m) was chosen as the experimental setup. Based on a thorough review of relevant literature, multiple sedimentary bottom shapes were designed to replicate different real-world geological depositional environments. Specific time steps were set to quantitatively introduce different types of quartz sand, achieving visualization of the experimental results. A water level control curve was designed to change the water level over time, allowing for precise control of water height in the tank and effectively simulating the evolution of stratigraphic sequences. Finally, based on the experimental data, stratigraphic integrity was calculated for various depositional environments, enabling further analysis of the experimental results.

The experimental results clearly reveal the evolution of stratigraphy and depositional sequence features, which closely match actual geological conditions. This indicates that the experiment can realistically simulate the sedimentary processes of marine (lake) to terrestrial transitional clastic rocks. From an overall perspective, erosion near the sediment source is more pronounced and frequent, while at the distal end, the strata remain more complete due to prolonged subaqueous conditions, and erosion is less noticeable. The depositional sequence shows a typical progradation pattern, with thin oblique and wavy bedding structures. Stratigraphic integrity studies show that the integrity increases from the proximal to distal end. A comparison of integrity at the same location shows that horizontal surface fluctuations have a much stronger impact on stratigraphic integrity than changes in the bottom shape, with frequency variations in the water level control curve having a greater effect than changes in amplitude.

This study uses 2D physical water tank experiments to simulate and reconstruct the sedimentary processes of marine (lake) to terrestrial transitional clastic rocks. It also quantifies the influence of geological control factors on stratigraphic integrity. The results demonstrate that both the sedimentary bottom shape and water level change curves affect stratigraphic integrity, with water level changes having a more significant impact. This research is the first to combine 2D water tank simulations with stratigraphic integrity control factors, providing innovative experimental methods and technical tools for sedimentary physical modeling and stratigraphic integrity assessment.

How to cite: Fu, S. and Liu, J.: The Study of Stratigraphic Integrity of Marine (Lake) to Terrestrial Transitional Clastic Rocks Based on 2D Flume Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7676, https://doi.org/10.5194/egusphere-egu25-7676, 2025.

The EcoDaLLi project is an integrative initiative designed to contribute to the European Green Deal’s freshwater objectives by supporting the restoration, protection, and sustainable management of the Danube River Basin and its delta. As part of the broader mission "Restore Our Ocean, Seas & Waters by 2030," the project employs a systemic approach to ecosystem restoration through the implementation of innovative solutions and improved governance frameworks. By focusing on the Danube Basin, one of Europe’s most ecologically significant areas, EcoDaLLi aims to strengthen climate resilience, enhance biodiversity conservation, and promote sustainable water resource management. Additionally, Unitatea Executivă pentru Finanțarea Învățământului Superior, a Cercetării, Dezvoltării și Inovării (UEFISCDI) from Romania has awarded a special funding grant to support the present research.

A core scientific objective of the project is to document and analyze the dynamic behavior of the water surfaces in the Danube Basin. The present research relies on satellite radar imagery from the Sentinel-1 constellation, made available through the Copernicus Program. The radar data’s ability to penetrate cloud cover and record consistent surface reflections makes it highly suitable for long-term multi-temporal monitoring of water bodies, especially in a complex and variable environment such as the Danube Delta.

The initial phase involves the systematic collection of radar imagery, focusing on the VV polarization channel, which offers superior water isolation characteristics compared to other channels. In the second phase, a rigorous preprocessing workflow is applied to the raw imagery, including orbital corrections, radiometric normalization, and noise reduction. These steps are critical for ensuring data consistency and enabling precise extraction of water body extents. The processed data is then subjected to detailed geospatial analysis using advanced GIS tools, enabling the derivation of key hydrological metrics. These metrics include maximum and minimum water extent, presence and recurrence of water bodies, and seasonal variations.

The analysis will employ methodologies such as Continuous Change Detection and Classification (CCDC) to track and quantify spatial and temporal changes across the monitored lakes. Statistical models will further be used to correlate observed hydrological changes with climatic and environmental factors. The resulting datasets will provide a robust foundation for understanding the long-term hydrological dynamics of the Danube Delta’s lakes and their role in regional ecosystem functioning. Moreover, the results will offer guidelines for local and regional stakeholders, supporting evidence-based policy-making and adaptive management strategies.

Acknowledgments

This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CNCS/CCCDI - UEFISCDI, project number PN-IV-P8-8.1-PRE-HE-ORG-2023-0089, within PNCDI IV.

How to cite: Toma, A. and Scrieciu, A.: Assessing Long-Term Water Dynamics in the Danube Delta Lakes using Sentinel-1 Radar Imagery, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8615, https://doi.org/10.5194/egusphere-egu25-8615, 2025.

Due global warming, rock glaciers were increased after the glaciers retreated rapidly. Rock glaciers, as an important indicators of mountain permafrost, play a critical role in mountain hydrology. The Gaizi River Basin, located in Pamir plateau and even has the Muztag-Ata (7,509m) and Gongger (7,719m) massifs. Comprehensive studies on distribution characterizations of rock glaciers in this region are currently in the incipient stages. Using Chinese high spatial resolution GF-2 Satellite images and Google Earth, a total of 56 rock glaciers were identified. Their spatial distribution and relationship with local factors were studied. Following the guidelines of the International Permafrost Association, out of the 56 rock glaciers, 9 are glacier-connected, 16 are glacier-forefield connected, 19 are talus-connected, and 12 are debris-mantled slope-connected. The rock glaciers are situated at slopes of 12゜–37゜ and elevations between 3380 m and 5320 m a.s.l. and predominantly facing north, northwest, or northeast (54.5 %). The average annual precipitation ranges from 26 mm to 350 mm and annual air temperature of the rock glaciers ranges from -13.5 ^。C to 3.9 ^。C. The rock glaciers can be used to quantify water storages and investigate the extent of permafrost and therefore carry significance in study their response to climate change.

How to cite: Liu, Y.: The distribution characteristics of rock glaciers in the Gaizi River Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12331, https://doi.org/10.5194/egusphere-egu25-12331, 2025.

Glaciers have retreated since the maximum extent of the “Little Ice Age” around c. 1850. The barren forefields provide a unique opportunity to study the development of an emerging ecosystem from its early stages to better understand successional mechanisms, community assembly and underlying filtering processes. While previous studies have primarily focused on the Central Alps, there remains a knowledge gap regarding succession for the forefields in the Northern Limestone Alps. The aim of this new monitoring platform is to gain a more comprehensive understanding of vegetation dynamics in the context of ecosystem succession in glacier forefields of this region. To this end, the chronosequence approach is applied across four glacier forefields, namely Hallstätter Glacier, Great Gosau Glacier (both in Dachstein mountains, Austria), Watzmann Glacier and Blaueis (both in Berchtesgaden Alps, Germany). Integrated, interdisciplinary methods are used for long-term monitoring and assessment of succession processes. From Vegetation monitoring which follows GLORIA guidelines, selected trait measurements, analysis of ancient DNA pools in ice lake sediments, abiotic site characterization including temperature recording and substrate sampling, to remote sensing methods we want to provide a whole picture of this dynamic environment. First results shows that species richness, abundance increase with age. However, these trends occur at a much slower rate than observed in the Central Alps. Initial trait analyses based on database entries revealed only a few clear patterns along the age gradient. In-depth analyses using trait field measurements are still underway. Additionally, environmental parameters seem to play a role in shaping succession, indicating that abiotic factors may significantly influence the pace and pattern of ecosystem development in the glacier forefields of the Northern Limestone Alps.

How to cite: Hecht, C.: Monitoring and research on succession in glacier forefields of the Northern Limestone Alps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12335, https://doi.org/10.5194/egusphere-egu25-12335, 2025.

Geological sea-level proxies (e.g., fossil intertidal or foreshore deposits) preserve crucial data that enable the reconstruction of historical sea-level fluctuations. This information is essential for assessing the extension and volume of ice sheets during previous warm periods.

The work aims to present the results of a morpho-stratigraphic field campaign conducted along the southern Brazilian coast, from Osório (Rio Grande do Sul) to Paranaguá (Paraná). A classical geological and geomorphological approach was coupled with a literature review of the geological sea-level proxies related to Marine Isotope Stage (MIS) 5 from the coast of Uruguay to São Paulo. Samples from shallow-water marine sand and aeolian deposits have been analysed using granulometric and micropaleontological methods, in addition to direct dating with the Optically Stimulated Luminescence (OSL) technique. The elevation of each proxy was measured with centimetric precision using a GNSS RTK station and referenced to the local geoid model (MAPGEO2015), with an associated error margin of only a few centimetres.

Preliminary findings indicate that vertical land movements, both associated with glacial isostatic adjustment and sediment isostatic rebound, may have played a key role in the accumulation of Late Pleistocene marine and aeolian deposits, positioning them several meters above sea level at odds with global mean sea level position.

This presentation contributes to the WARMCOASTS project, which received funding from the European Research Council under the European Union's Horizon 2020 research and innovation programme (grant agreement n. 802414).

How to cite: Cerrone, C., Lämmle, L., Perez Filho, A., Scicchitano, G., Jovane, L., Tagliaro, G. T., Mitrovica, J. X., Stocchi, P., and Rovere, A.: Pleistocene morpho-stratigraphy and vertical land motions on the South Brazil-Uruguay coastal plain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12417, https://doi.org/10.5194/egusphere-egu25-12417, 2025.

Accurate assessment of coastal vulnerability is crucial for effective coastal risk management, especially in the context of increasing human pressure. One common approach to evaluating coastal erosion risk involves the use of geomorphological-based indices. These indices typically combine various physical factors such as: shoreline changes with historical and recent trends in coastline movement (erosion or accretion); dune and beach geometry (slope, dune height, and width); presence and type of vegetation, which can stabilize or destabilize the coastline; coastal infrastructure. the presence and type of human-made structures, such as seawalls and groins, which can impact coastal processes. These factors are often assigned weights or ranks to create a vulnerability classification, allowing for the identification of areas at higher risk of erosion. This approach provides a valuable framework for understanding the inherent susceptibility of a coastline to erosion. However, it is important to highlight that this is a simplified representation of complex coastal processes. Geomorphological indices offer a valuable tool for initial assessments of coastal vulnerability. Nevertheless, they should be used in conjunction with other data sources and analyses to gain a more comprehensive understanding of coastal processes. This study investigates coastal vulnerability along a coastline in Basilicata, southern Italy. The region faces significant coastal erosion due to a combination of natural factors and human impacts. To assess vulnerability, the study employs a multi-scale approach based on:  i) Coastal Erosion Susceptibility Index (CESI), this index evaluates the inherent susceptibility of the coastline to erosion based on factors like shoreline changes, dune and beach geometry, and vegetation. The results identified "hotspots" – areas with the highest level of susceptibility of coastal erosion; ii) High-resolution LiDAR Surveys, Unmanned Aerial Vehicles (UAVs) equipped with LiDAR sensors were used to create detailed 3D models of the coastline. By comparing LiDAR data from 2013 and 2023, we quantified the extent of coastal erosion and identified specific areas of significant change. This study demonstrates the effectiveness of integrating spatial data derived by indices with high-resolution LiDAR data for comprehensive coastal vulnerability assessment. This approach provides valuable insights for coastal managers in developing effective adaptation strategies to address the challenges posed by coastal erosion in the context of climate change and sea-level rise.

Founded by: Progetto PE 0000020 CHANGES, - CUP [B53C22003890006], Spoke 7, PNRR Missione 4 Componente 2 Investimento 1.3, finanziato dall’Unione europea – NextGenerationEU

How to cite: Minervino Amodio, A., Corrado, G., Di Paola, G., Rizzo, A., and Gioia, D.: Investigating Coastal Erosion Hotspots: A Multiscale Approach applied along the Basilicata Ionian coast (Southern Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13498, https://doi.org/10.5194/egusphere-egu25-13498, 2025.

Coastal Zone Management Act (CZMA) areas in the United States are critical regions where coastal development and environmental conservation converge. Over 50 years, the CZMA has established a federal framework for state-level coastal management, fostering resilience to dynamic challenges. However, these regions increasingly face compounding risks from hazards such as sea-level rise, storm surges, and extreme precipitation, compounded by socio-economic vulnerabilities and geomorphological dynamics.

This study develops a geospatial framework for multi-hazard risk assessment in CZMA areas, integrating geomorphic and sedimentological characteristics with high-resolution datasets and socio-economic indicators to compute a detailed risk index. High-resolution datasets, including satellite-derived shoreline positions and wave and tidal records, are integrated with advanced geospatial and machine learning models, to enhance spatial and temporal projections. Future climate scenarios (2030, 2050, 2100) from CMIP6 datasets are used to assess long-term impacts of sea-level rise and extreme events, with scenario-based modeling addressing uncertainties across different emissions and socioeconomic pathways.

Preliminary findings reveal significant heterogeneity in risk distribution across CZMA areas, with low-elevation coastal plains, deltas, and lagoons identified as the most vulnerable due to geomorphic sensitivity and several challenges to protect them. Our comprehensive map highlights hotspots where erosion, flooding, and socio-economic disparities converge, enabling tailored adaptation strategies. This research bridges policy and science by integrating CZMA legal frameworks with geospatial and technological innovations, offering a scalable and transferable methodology for assessing and managing coastal multi-hazard risks globally.

How to cite: Poudel, S., Bista, S., and Talchabhadel, R.: Multi-Hazard Risk Assessment in CZMA Areas: A Geospatial Framework Integrating Future Climate Projections, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14644, https://doi.org/10.5194/egusphere-egu25-14644, 2025.

Interplay between environmental drivers and antagonistic biotic interactions shape the niche of species. Understanding the extent to which species retain parameters of their ecological niches amid long-term environmental changes is crucial for numerous palaeoecological inferences applicable to conservation efforts, sequence stratigraphic reconstructions, and macroevolutionary theory. 

The Venus nux association of the Arda and Stirone River sections (Early Pleistocene, western Emilia, northern Italy) has been here analyzed from a systematic and a paleoecological point of view, resulting in the identification of 23 mollusc taxa. As the majority of the retrieved taxa is represented by living species, a comparison between their fossil and present-day environment has been carried out, focusing also on the Venus nux association during the Pliocene of the same region. This research aimed to assess whether the overall bathymetric range and dominance of the bivalve Venus nux have changed over the last 5 million years in the Adriatic basin. Preliminary results indicate a shift in the ecological niche of this common species during a time marked by increasingly pronounced climatic oscillations.

Indeed, currently, V. nux is rarely retrieved in the Adriatic basin, but it is common in the Alboran Sea and the Ibero-Moroccan Gulf (southern Spain), where it thrives in muddy to muddy-sandy substrates at depths between 30 and 350 meters (Salas, 1996), but typically is abundant within 60 and 120 m depth ranges. Conversely, during the Pliocene and Pleistocene geological intervals, V. nux was common in the sedimentary successions of the Adriatic Basin, though it exhibited dominance at different depths and a potentially different bathymetric range. Specimens of V. nux from the Lower Pleistocene Arda and Stirone River sections reveal a shallower bathymetric distribution (20-40 meters of water depth), as evidenced by the co-occurrence in the mollusc association of shallow-water species, like Mytilus edulis and Ostrea edulis. During the warm Pliocene (Zanclean-Piacenzian transition), its bathymetric distribution was slightly deeper than in the cold Early Pleistocene, possibly mirroring current conditions. Although further detailed studies are necessary, it seems that over the past few million years, this species has changed its niche parameters, possibly due to climate shifts.

Salas, C. 1996. Marine bivalves from off the southern Iberian Peninsula collected by the Balgim and Fauna 1 expeditions. Haliotis 25: 33–100.

How to cite: Crippa, G., Chiari, A., Lombardi, M., and Scarponi, D.: The Venus nux association during the Early Pleistocene of the Adriatic Sea: a comparative analysis with its Pliocene and Recent distribution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16446, https://doi.org/10.5194/egusphere-egu25-16446, 2025.

The exploration of seabed topography is of paramount importance for a wide range of scientific and environmental applications. In deep water, sonar or multibeam technology among others are commonly used to map details of the sea floor, but applying these techniques in shallow waters is challenging due to the complex nature of the submerged terrain. Moreover, these techniques are costly and not accessible for small-scale projects. In recent years, underwater photogrammetry emerged as an effective solution for shallow water bathymetric mapping, bridging the gap between land topography and deep-water bathymetric measurements. Photogrammetry also enables a 3D or 4D visual representation of the submerged terrain, habitats, and objects.

Our research proposes a novel approach applying underwater photogrammetry to generate a 3D model of submerged terrain in shallow-waters over rocky coastline. Using underwater photographs and advanced land surveying techniques, we successfully generated a high-resolution, georeferenced 3D model with detailed geospatial maps covering 162 m² at depths ranging from 1 to 5 meters below sea surface of a submerged upper subtidal zone of a rugged, rocky-coast landscape.

The proposed method offers a practical and affordable tool for shallow water bathymetric mapping over subtidal zones in rocky coasts, providing scientists with geospatial maps, measurements and visual representations for applications in marine research, coastal management, habitat monitoring, or underwater archeology.

How to cite: Elias, A. R. and Khalil, A.: 3D Mapping of Submerged Landscapes: A Cost-Effective Approach to Shallow-Water Bathymetry Using Underwater Photogrammetry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17381, https://doi.org/10.5194/egusphere-egu25-17381, 2025.

Quantitative analysis of drainage networks is one of the most used approaches for the investigation of the response of landscape to tectonic forcing and crustal deformation in different geodynamic setting. Recently, river profile inversion has largely been used for the reconstruction of spatial and temporal distribution of uplift in tectonically-active landscapes. The calibration of the erodibility coefficient of the river profile is particularly effective in coastal landscapes, due to the diffuse presence of independent geomorphic markers of the tectonic uplift such as the marine terraces. In this work, we estimated the uplift history of a large sector of the Ionian sector of South-Apennine chain by inverse modelling of river profiles. The landscape is dominated by the presence of several well-preserved orders of marine terraces, which are deeply incised by a trellis-type fluvial net. Several factors such as uniform lithology and well-constrained chronology of several orders of marine terraces provided a favourable setting for the robust application of the modeling of river profiles. The study area includes a large sector of the Ionian coast between Taranto and northern Calabria. southern Italy. From a geological viewpoint, the studied catchments transversally drain the outer zone of the chain to the south and the foredeep-foreland system to the north. Middle Pleistocene deformation in the external sector of the chain has been already demonstrated while the late Quaternary activity of the frontal thrust belt is more debated. Our reconstruction of the spatial and temporal increase of uplift rates to the south can contribute to unravel the recent/active deformation along the buried front of the chain.

How to cite: Gioia, D., Cerrone, C., Corrado, G., De Santis, V., Minervino Amodio, A., and Schiattarella, M.: Uplift history of the Taranto Gulf (southern Italy) from river profile inversion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17790, https://doi.org/10.5194/egusphere-egu25-17790, 2025.

The Portuguese spatial planning legislation includes legal restrictions to land use in order to preserve the ecosystems. These restrictions are framed by the legal structure called National Ecological Reserve (NER), and have associated a cartographic representation. Among the land use protection areas included in the NER are the Areas of High Risk of Soil Hydric Erosion (AHRSHE). Our goal is to improve the models and derived cartography and to use the enhanced maps as a basis to test and apply new and more advanced technologies, data and methods.

Currently, AHRSHE are determined based on USLE. The computation of the LS factor in this equation has been a challenging issue and, since this action is a legal responsibility of the municipalities, we could face a situation where different municipalities use different methodologies and, eventually, the results being not comparable. Thus, efforts have being made in order to produce a common methodology to standardise and enhance the cartographic representation of the LS, namely, by improving its accuracy and precision and by harmonizing and making it compatible with the other USLE factors. For this purpose, several methods of LS computation have been tested to evaluate soil loss risk in different geomorphic contexts. Based on the test results USLE's second revision, RUSLE2 (USDA, 2008), was selected together with imposing a maximum value to unorganised runoff length (L).

The results of using RUSLE2 might be affected by the lack of information on detailed soil properties caused by different geomorphological contexts and the lack of resolution of the Digital Terrain Model (DTM) to accurately identify the AHRSHE. The lack of DTM resolution affects the slope values (S), the shape of the hydrographic network and, above all, the delimitation of the disorganized flow domain, where AHRSHE are mapped.

In order to reach an acceptable solution, tests were made with varying maximum unorganized runoff length (L) and using different formulas to determine S, according hillslope values and rainfall regime. The test results show that the more accurate LS is obtained when L is limited to 305 m and S is calculated according to slope thresholds: below and above 9% (Panagos, et al., 2015) or above 18% (Liu, 1994; 2002), and excluding areas where the USLE is not applicable, like plane surfaces, water, or surfaces with high slopes.

Another conclusion was that small resolution DTM are inappropriate which lead us to use in the tests a 10m pixel DTM. Even so, and in order to prevent unjustified land use restrictions, we suggest the need to validate the results (by sampling), at least in specific geomorphologic contexts. Otherwise, the likelihood to get biased results, with adverse practical effects, will be high.

The shape and accuracy of AHRSHE depend on the methodologies and georeferenced data used. Thus, we intend to use, in the near future, a very-high resolution DTM derived from aerial LiDAR and to work on the identification of differentiated geomorphological contexts in each municipality in order to further improve the AHRSHE mapping, which have substantial impacts in the NER.

How to cite: Silva, A. and Reis, R.: Criteria to Map Areas of High Risk of Soil Hydric Erosion in Portugal using USLE, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20437, https://doi.org/10.5194/egusphere-egu25-20437, 2025.

Anthropogenic global change and environmental degradation lead to not only declines in biodiversity but also the simplification of trophic webs and fundamental changes in biotic interactions as taxa are removed from ecosystems. These changes are currently playing out over time scales of decades and centuries. Still, it would be instructional to understand the relationships between biotic interactions, diversity, and environmental change through deep time. Here, focusing on cephalopods, we quantify the relationships between antagonistic interactions and estimates of diversity, origination rates, and extinction rates. We have compiled a database of antagonistic biotic interactions preserved on fossil cephalopods composed of 279 species occurrences and 148,846 specimens ranging in age from Silurian to Quaternary. Predation occurrences were sparse in the Paleozoic, with peaks in the Jurassic and Cretaceous. We constructed a Generalized Linear Model comparing predation frequency and parasitism prevalence (for samples whose n ≥ 10) to mean standing genus diversity and three-timer origination and extinction rates using data from the Paleobiology Database and the Shareholder Quorum Subsampling methodology available on the FossilWorks website. A significant positive relationship exists between the frequency/prevalence of antagonistic interactions and mean standing diversity. Origination and extinction rates both have significant negative relationships with antagonistic interactions with much higher coefficients than mean standing diversity. We interpret this to mean that the intensity of antagonistic biotic interactions is higher when diversity is elevated but, more importantly, stable. We think this reflects that many of these interactions are obligate and taxon-specific. Ongoing work will include proxy data for temperature and CO2 concentration. As with modern ecosystems, we see evidence for links between diversity loss and the simplification of trophic webs in deep time.

How to cite: Burman, Z., De Baets, K., and Huntley, J. W.: Biodiversity loss and the simplification of trophic webs: Lessons from cephalopods in deep time, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21258, https://doi.org/10.5194/egusphere-egu25-21258, 2025.

How to cite: Gkogkis, K. and Valyrakis, M.: Siphon-Enhanced Micro-Hydroelectric System: Harnessing Elevated Flow Rates for Improved Power Generation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2380, https://doi.org/10.5194/egusphere-egu25-2380, 2025.

This research explores the transport dynamics of floating macro-plastics in riverine environments using drones for monitoring. Controlled flume experiments were conducted to evaluate the roles of vegetation density and release position on the movement and retention of plastic debris. Aerial imagery (captured by a DJI Mini 3 drone) was analyzed to determine transport patterns, revealing that plastics released in central flow zones moved faster with lower retention, while those near densely vegetated riparian areas experienced slower transport and higher trapping rates.
The findings demonstrate drones’ effectiveness in monitoring plastic pollution, providing a practical alternative to traditional methods in areas difficult to access. These insights emphasize the critical role of riparian vegetation in influencing plastic movement and retention, offering opportunities to design interventions that target pollution hotspots [1,2]. The study highlights the promise of drone-based approaches in advancing our understanding of plastic transport processes and informs strategies to mitigate the environmental impacts of plastic waste. Future research could enhance these findings by integrating drone data with other monitoring systems and refining analytical techniques for natural environments.

References
[1] van Emmerik T, Roebroek CTJ, de Wit W, Krooshof E, van Zoelen C, Fujita Y, Bruinsma J, Treilles R, Kieu-Le TC, Elshafie A, Christensen ND, Biermann L, Hees J, Meijer LJJ (2023) Seasonal dynamics of riverine macroplastic pollution, Nature Water, 1, 51-58
 
[2] Valyrakis M, Gilja G, Liu D, Latessa G (2024) Transport of Floating Plastics through the Fluvial Vector: The Impact of Riparian Zones, Water, 16, 1098

How to cite: Kaloudis, G. and Valyrakis, M.: Harnessing Aerial Imaging Techniques to Monitor the Transport of Floating Macro-Plastics in Fluvial Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2558, https://doi.org/10.5194/egusphere-egu25-2558, 2025.

Lacustrine organic-rich Eocene mudstones are well developed and demonstrates significant exploration potential for shale oil in the Qibei Sub-sag, Bohai Bay Basin, China. However, their oil content displays strong heterogeneity, which poses challenges for effective exploration and development. Diagenesis implicates compaction, cementation, dissolution/re-precipitation processes that raises critical questions regarding reservoir quality and oil-bearing heterogeneity.

Integrated high‐resolution petrologic analysis, organic geochemistry, and pore throat structure characterization provide a powerful approach to investigate the diagenesis, reservoir and oil-bearing characteristics. The 50 samples were collected from the 111.39-m-thick Eocene the first Sub-member of the third Member of the Shahejie Formation lacustrine oil-prone source rock succession penetrated by the two wells in the Qibei Sub-sag. Six typical lithofacies were identified: laminated medium-grained calcareous shale, laminated fine-grained mixed shale, thin-bedded fine-grained mixed mudstone, thin-bedded medium-grained mixed mudstone, massive medium-grained mixed mudstone, and thin-bedded coarse-grained felsic mudstone.

The micritic calcite laminae formed during the sedimentary stage underwent recrystallization during the early to middle diagenetic stages, transforming into granular sparry calcite. Potassium feldspar dissolution and clay mineral transformation resulted in the formation of authigenic albite and quartz. These diagenetic processes promoted the development and preservation of intercrystalline/interparticle pores. As a result, the laminated medium-grained calcareous and laminated fine-grained mixed shale reservoirs exhibit superior reservoir properties, primarily characterized by interparticle pores, intercrystalline pores, clay mineral-associated pores, and bedding fractures. With a median pore throat diameter of 11.6 nm and an average porosity of 6.53%, these reservoirs are classified as Type I. The thin-bedded fine-grained mixed shale primarily develops clay mineral-associated pores and interparticle pores, with some bedding fractures. Its median pore throat diameter is 9.2 nm, and the average porosity is 5.56%, classifying it as a Type II reservoir. The thin-bedded medium-grained mixed and massive medium-grained mixed mudstones mainly develop interparticle pores and clay mineral-associated pores. These have a median pore throat diameter of 12.6 nm and an average porosity of 4.3%, classifying them as Type III reservoirs. In felsic mudstone, calcite cementation significantly reduced porosity during the early diagenetic stage. This results in the poorest porosity development in the thin-beded coarse-grained felsic mudstone, which has a median pore throat diameter of 15.9 nm and an average porosity of 3.26%, classifying it as Type IV reservoir.

The laminated medium-grained calcareous shale, laminated fine-grained mixed shale, and thin-bedded fine-grained mixed mudstone exhibit relatively high oil content and OSI values. The average oil content values are 2.48 mg/g, 2.64 mg/g, and 2.30 mg/g, respectively, and the average OSI values are 144 mg HC/g TOC, 163 mg HC/g TOC, and 168 mg HC/g TOC. These lithofacies are favorable for shale oil exploration and development. We suggest that addressing the challenges of mudstone diagenesis will significantly improve understanding and prediction of reservoir quality and oil-bearing heterogeneity in unconventional shale oil plays.

How to cite: Wang, J., Zhao, J., You, Z., Pu, X., Liu, K., Zhang, W., Shi, Z., Han, W., and Wang, Z.: Diagenesis, reservoir-quality, and oil-bearing heterogeneity of the Eocene deep-lacustrine mudstone in the Qibei Sub-sag, Bohai Bay Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2655, https://doi.org/10.5194/egusphere-egu25-2655, 2025.

        Glutenite Fans is one of the most favorable reservoirs for exploration and development in recent years and is widely distributed in the world. In recent years, major breakthroughs have been made in oil and gas exploration of glutenite fans in Luojia area in Luoxie 180 and Luo25 Wells. The Jiyang exploration area is a high mature exploration area in the east, which has entered the exploration stage mainly to search for subtle oil and gas reservoirs, and Glutenite Fans, as an important part of subtle oil and gas reservoirs, has become the most realistic and valuable exploration target at present.

       The Luojia area has a complex structural background, with the development of fault structures in the area, and the development of two sets of glutenite fans bodies of different origin, and the lithology difference is great. The diagenesis is complex and the calcareous intercalation is widely developed, which is of great significance for reservoir reconstruction.

        This paper takes the sand conglomerate of Es3 and Es4 members in Luojia area of Zhanhua Depression as the research object, synthesizes seismic, logging, core, analysis and test data, and carries out the research on the genetic types, sedimentary characteristics and diagenesis of the sand conglomerate controlled by different tectonic activities and provenance.

How to cite: yao, Y. and yang, Y.: Sedimentary Characteristics and Sedimentary Model of Glutenite Fans in Shahejie Formation, Luojia area, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2783, https://doi.org/10.5194/egusphere-egu25-2783, 2025.

The Permian Fengcheng Formation is an important hydrocarbon source rock development sequence and exploration sequence in the Junggar Basin. The Hashan tectonic belt, located on the northwestern margin of the Junggar Basin, is a large-scale thrust nappe superposed structure. Having undergone multiple tectonic movements and tectonic uplift and denudation, it has lost the stratigraphic distribution characteristics of a foreland basin. The Fengcheng Formation developed on multiple thrust tectonic steps, resulting in difficulties in stratigraphic correlation and unclear understanding of the distribution characteristics of the original sedimentary system and the development characteristics of favorable reservoirs. Therefore, clarifying the distribution laws and genesis of diagenesis and establishing a reservoir-forming model for high-quality reservoirs are of great significance for the effective sedimentary reservoir mechanism and the prediction of favorable gas-bearing areas in the study area.

How to cite: Li, Y.: Characteristics of Shale Reservoirs in the Permian Fengcheng Formation, Hashan Region , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3009, https://doi.org/10.5194/egusphere-egu25-3009, 2025.

Shale oil, as one of the most important unconventional oil and gas resources, has become the key target of oil and gas exploration in recent years. The Fengcheng formation in Mahu Sag is the best source rock in the sag, which has great potential for shale oil resources and is the key area for shale oil exploration in Junggar Basin.

Volcanic activity was frequent during the sedimentary period of Fengcheng Formation in the northern part of Mahu Sag. The sediments are mainly composed of tuff material of volcanic activity, evaporation material of caustic lake and a small amount of detrital material. The terrigenous detrital material mainly comes from long-distance transport, while the pyroclastic material is closely related to the proximal volcanic activity. The lithofacies development of shale is characterized by frequent overlapping of various lithologies, diverse combination types and rapid changes. The microfabric of fine-grained sedimentary rocks is characterized, the lithofacies types of fine-grained sedimentary rocks are summarized, and the assemblage relationship and development law of lithofacies in different environments are analyzed. The formation process of lacustrine fine-grained sedimentary rocks is discussed from the perspective of provenance supply and sedimentary dynamics, and the lithofacies development model of fine-grained sedimentary rocks is established. To a certain extent, the theory of lacustrine sedimentology is enriched and perfected, and it can also provide basic geological basis for tight oil exploration in this area.

How to cite: zhuang, Y.: The origin and lithofacies development characteristics of fine particle composition in the shale of the second member of Fengcheng Formation in Mahu Sag, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4626, https://doi.org/10.5194/egusphere-egu25-4626, 2025.

Abstract：Lake deltas are located in the complex zone of lake and river interaction, influenced by the dual effects of material exchange between the two. There are not only climate and water level influences, but also topography and geomorphology and waves and other lake hydrodynamic influences, resulting in a more complex lake delta evolution process. To explore the sedimentary characteristics and the impact of lake dynamics during different stages of delta development under the influence of coast current, the Muhuahe Delta in Daihai Lake is taken as the study object for modern sedimentary investigations. Through the analysis of high-precision satellite photos and the interpretation of profile information collected by UAV oblique photography, the sedimentary evolution of the delta in the study area was analyzed in detail. The results show that delta deposits are developed in the eastern gentle slope zone of Daihai, and the delta front subfacies are widely distributed. The profile shows that the sand bodies are affected by strong hydrodynamics, and a large number of wave-formed structures are developed and lateral migration is obvious on the plane. Satellite remote sensing data suggest the sedimentary sand bodies' development and distribution characteristics, indicating the control of coast current in the development and evolution of the delta. The delta is asymmetric, with well-developed sand dams at the delta front, growing parallel to the shoreline. Although influenced by provenance supply, during this period, the delta is controlled by littoral currents, and its expansion toward the lake basin is suppressed. Generally, coast current plays a significant role in modifying the plane distribution and scale of the delta front sand bodies. Reservoir heterogeneity is often generated due to different dominant hydrodynamic conditions, providing a reference for further exploration into the influence of coast current on reservoir development and distribution.

Keywords: coast current; gentle slope delta; sedimentary evolution

How to cite: Jiang, Y.: Sedimentary Evolution and Morphological Characteristics of Modern Lake Shoreline Delta under the Influence of Coast Current, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4736, https://doi.org/10.5194/egusphere-egu25-4736, 2025.

On the basis of core observation and description, multi-scale microscopic analysis and related reservoir physical property analysis, the petrological characteristics, reservoir characteristics and diagenetic characteristics of the Lower Jurassic Sangonghe Formation in the central area of Junggar Basin are systematically studied, and the diagenetic evolution sequence of the reservoir is further established. The results show that the reservoir in the studied interval has undergone three diagenetic processes: compaction, cementation and dissolution during its development and evolution after burial. The reservoir mainly goes through two stages: early burial compaction and late tectonic compression. There are various types of cementation, including carbonate, siliceous, clay mineral, gypsum and anhydrite. The overall intensity of dissolution in the reservoir is low, and it mainly develops in the interior or edge of easily soluble components such as feldspar and rock cuttings, and also develops in the edge of clay mineral bonding. Diagenetic evolution sequence of the reservoir in the study area is as follows: early calcite cementation - early chlorite cementation - acid dissolution/quartz enlargement/kaolinite cementation - illite cementation - gypsum/anhydrite cementation - late calcite cementation - iron calcite/iron dolomite cementation, mechanical compaction has developed in the whole burial evolution process.

How to cite: Guo, T. and Zhang, L.: Reservoir characteristics and diagenetic evolution of Lower Jurassic Sangonghe Formation in the hinterland of Junggar Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4748, https://doi.org/10.5194/egusphere-egu25-4748, 2025.

Coastal areas and related sedimentary environments are remarkable providers of valuable information about climatic changes and sea level oscillations. Lake Mert was formed as a shallow Black Sea coastal lagoon that contains various mixtures of marine and freshwater sources. This study presents sedimentological, geochemical and paleontological analyses of five sediment cores recovered from the lake which has been severely influenced by sea level change and local climate over the last 6.5 cal. ka BP. The environmental and climatic records obtained by multi-proxy analyses of the cores (µ-XRF, total organic carbon, stable isotope, pollen analysis and foram content) that are confidently correlated with other regional and global climate signals. In addition, Lake Mert also remains a challenge to identify and quantify dynamic changes in time on the coastal plain, thus, it possibly reflects hydrologic changes in the Black Sea since the middle Holocene. Analysis of lithology together with paleontological content of the studied cores reveal three main depositional units, each of them indicates varying areal facies distribution due to highly dynamic depositional settings in lake. Accordingly, the main lithofacies in the cores from bottom to top are defined as a relict lacustrine sediment older than 6.5 cal. ka BP (Unit 3), coastal and deltaic facies deposited between 6.5 to 4.5 cal. ka BP (Unit 2) and the younger lagoon-marine sediment (Unit 1).

Moreover, the correlation of well-dated sedimentological and geochemical proxies with the sea level and sea surface salinity records from the Black Sea allows us differentiate various phases of hydrologic changes due to connections with the Lake Mert during the middle-to-late Holocene. Our preliminary results suggest that the relict Mert Lake was first invaded by the Black Sea waters prior to 6.5 cal. ka BP, and then remained its fully connection until ~5.3 cal. ka BP due to subsequent inflow of the Mediterranean Sea via Bosporus. Furthermore, the decelerated sea level rise between 5.3 and 4.5 cal. ka BP gave rise to return semi-closed lagoon phase, restricting mixture with the Black Sea waters as inferred from stable oxygen isotope record. The later period, particularly after 3.5 cal. ka BP, was associated with more Euryhaline condition in the lake based on the paleontological content of the core sediment. The local climate changes are recorded in Lake Mert as a wet period between 6.5 and 4.5 cal. ka BP, a dry period between 4.5 and 2.9 cal. ka BP and wetter period after 2.9 cal. ka BP, respectively.

How to cite: Yakupoglu, C., Eriş, K. K., Karlıoğlu Kılıç, N., Yılmaz Dağdeviren, R., Nazik, A., Acar, D., Yakupoğlu, N., Sabuncu, A., and Kırkan, E.: Middle-to-Late Holocene Climate Change in Lagoon Lake Mert (NW Black Sea) and Its Hydrological Connection with the Black Sea: evidences from multi-proxy records , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4788, https://doi.org/10.5194/egusphere-egu25-4788, 2025.

Calcareous nannofossils are essential for age dating and studying environmental changes. These microscopic (1–20µm) calcitic cell-wall fossils coverings are abundant in most post-Paleozoic marine sedimentary rocks, providing a continuous stratigraphic record of biotic change. This study aims to document the stratigraphic occurrence of calcareous nannofossils at the wide-spread shallow marine carbonates of related to the Qom Formation in the Nargesan, Band, and Qaleh-Gabri sections, southeast of Kerman province (East of Central Iran Basin). Samples were collected at 50-100cm intervals from the marly parts of the section to basal part of the Upper Red Formation. To preserve the small-sized coccoliths, samples were processed using simple smear slide method. The prepared slides were examined with an Olympus BX53 light microscope using cross-polarized light at a magnification 1500-2000X. Gypsum and Quartz plates were used to identify various species. In this study employed the standard calcareous nannofossil zonation by Martini 1971 for the Oligocene sediments. The studied interval ranges from the Lowest Appearance (LA) of Sphenolithus ciperoensis species to the Highest Appearance (HA) of the Sphenolithus distentus, corresponding to the NP24 zone defined by Martini 1971. The calcareous nannofossil assemblages exhibit moderate diversity and frequency, with moderately to well-preserved nannofossil specimens observed, such as: Sphenolithus ciperoensis, Sphenolithus conicus, Sphenolithus moriformis, Zygrhablithus bijugatus bijugatus, Helicosphaera recta, Helicosphaera euphratis, Reticulofenestra bisecta, Reticulofenestra dictyoda, Reticulofenestra minuta, Cyclicargolithus floridanus, Cyclicargolithus abisectus, Coccolithus pelagicus, Braarudosphaera bigelowii, etc. According to the above-mentioned calcareous nannofossil assemblages, the age of late Rupelian can be assigned for the studied samples from the surface sections. Furthermore, the high-resolution study of calcareous nannofossils indicates a significant decrease in the abundance and diversity of Oligocene nannofossils, mirroring trends observed at other low and middle latitudes sites. This record of calcareous nannofossils and bioevents provides valuable insights into the paleoenvironments of thatperiod. This research marks the first report of nannofossils from shallow-water carbonates (related to the Qom Formation) from Jiroft-Kerman area.

References

Martini, E. (1971) Standard Tertiary and Quaternary Calcareous Nannoplankton Zonation. Proceedings of the 2nd Planktonic Conference, Roma, 1970, 739-785.

How to cite: kiani shahvandi, M., Parandavar, M., and Heinz, P.: Investigation of shallow-water carbonate distributions related to the QomFormation in distant sections of the type area, southeast of Kerman, Iran: insight to calcareous nannofossils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7029, https://doi.org/10.5194/egusphere-egu25-7029, 2025.

Deep marine carbonate rocks in the Tarim Basin, Northwest China, have significant burial depths, ancient ages, and complex diagenetic evolution. Multi-stage tectonic activities and periodic sea-level changes create unconformities that expose carbonate rocks, resulting in interlayer, syn-sedimentary, and epigenetic karst systems. These processes, along with host rock composition and faulting, shape carbonate reservoir distribution and properties. Dissolution is most intense in shallow water grainstones and packstones, where fracturing enhances fluid flow, serving as both reservoirs and migration pathways. Consequently, carbonate reservoir characteristics in the northern Tarim Basin vary systematically from north to south, shaped by variations in unconformity size, diagenetic patterns and fault activity intensity, reflecting the basin’s evolution from deposition to deep burial. In the Yakela area, the northernmost region, significant uplift and erosion have exposed Cambrian, sometimes even Sinian bedrocks beneath Cretaceous layers, forming buried hill dolomite reservoirs. Moving south to the Tahe area, a paleokarstic erosion zone has developed large-scale dissolved fracture-cavity reservoirs due to the combined effects of faulting, surface karstification, and river system development near the base Carboniferous erosion surface. Further south, in the Tahe slope zone, reservoirs are shaped by a combination of dissolution and faulting, with bedding-parallel dissolution pores and enlarged fractures becoming more prominent as proximity to the paleoerosion surface decreases. This reflects a decrease in karstification intensity and an increase in fault-induced fluid pathways. In the Shunbei area where marine carbonates are deeply buried, structural features such as fault slip surfaces and open fractures dominate reservoir formation, with tectonic activity and fluid flow through fractures driving diagenetic alterations. The spatial variations in diagenetic pathways—from initial deposition and uplift in the north to deep burial in the south—highlight the interplay of dissolution, tectonics, and fluid migration across varying depths and time scales, providing insights into the mechanisms that control carbonate reservoir formation and evolution globally.

How to cite: Fan, T.: Orderly variations in the spatial and geological characteristics of carbonate reservoirs in the northern Tarim Basin, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7580, https://doi.org/10.5194/egusphere-egu25-7580, 2025.

    A 39,000-year record of sedimentary environmental changes, based on high-resolution grain size and diatom records from core ZK13-22, in the eastern shore of the Dongzhaigang harbor, Hainan Island, make it possible to study the relationship between environmental changes in the study area and the sea level changes in the South China Sea.

    The results show that during the period from 39.4 to 15.3 ka B.P., the grain size of the core ZK13-22 sediments was relatively coarse, and no diatoms were observed in the corresponding layer, suggesting that the study area was mainly in a terrestrial environment. Between 15.3 to 10.3 ka B.P., the grain size decreased during post-glacial period, the plankton species (Cyclotella striata and Paralica sulcata), which are marine species living in estuarine areas, was above 70% on average. The content of the benthic species Nitzschia cocconeiformis reached as high as 17%, indicating a rise in sea level in the South China Sea, marine waters intruded onto the Dongzhaigang harbor and reached the core site, and during this transgressive interval, the study area changed into an intertidal environment. From 10.3 to 7.6 ka B.P., the sediment particle size reached its lowest value throughout the borehole, while the species diversity and abundance of diatoms peaked, dominated by eurythermal intertidal and coastal planktonic species, the core site generally showed a enhanced marine influence and reduced freshwater input, shallow marine environment developed in situ. Between 8.0 to 7.6 ka B.P., the content of Rhizosolenia bergonii peaked, suggesting that the sea water temperature and salinity were relatively high during this period, possibly related to the intensified warm currents in the region. Since 7.6 ka B.P., the grain size increased significantly, diatoms only appeared at 4.4 ka B.P.. During this period, the relative abundances of Cyclotella striata and Paralica sulcata in the sediments climbed to 29% and 26% respectively. This change indicates enhanced hydrodynamic conditions, increased riverine influence, and sea level fluctuating decreases. Correspondingly, the the core site gradually shifted to an estuarine-intertidal environment. During the period from 4.4 to 3 ka B.P., the sediment grain size increased sharply, the study area transitioned to a terrestrial depositional environment.

How to cite: Yang, X., Wang, C., Jiang, W., and Hu, D.: Environmental changes since 39 ka reflected by diatom in core sediments from Dongzhaigang Harbor, Hainan Island, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11788, https://doi.org/10.5194/egusphere-egu25-11788, 2025.

The built environment (BE) across various sectors faces significant challenges due to increasing deterioration, ageing infrastructure, extreme climatic conditions, rising urban populations, and limited financial resources [1]. Digital transformation offers the potential to revolutionize current practices for managing and sharing key information, improving decision-making processes and enabling more efficient and sustainable BE in the long term. However, despite recent advancements in technology, critical infrastructure systems within the BE continue to rely on traditional management approaches in terms of technology, organizational structure, and institutional frameworks. Consequently, they fail to fully leverage emerging technologies that could enable advanced resource and risk management through real-time data integration and enahnced analytical methods.

Adopting technologies associated with Infrastructure 4.0 (CI4.0) [2] can accelerate the digitalization of BE, with a particular focus on infrastructure systems. This study highlights the foundational elements of a next-generation BE designed to foster an interconnected and collaborative ecosystem focused on cities, infrastructure, and societies. Several case studies are explored, including large residential developments, transportation networks, and buildings, demonstrating the transformative potential of digitalization in delivering real-time information to stakeholders, thereby enhancing decision-making processes.

These efforts rely on the acquisition of real-time data from the environment to predict both current and future conditions of the BE. For instance, advanced microcontrollers are utilized to monitor the declining performance of ageing infrastructure over waterways and to measure flood levels in real-time. Datasets are processed on high-performance cloud-based systems, utilizing deep learning algorithms to forecast infrastructure conditions and climatic risks. In emergency scenarios, such as river overflows, flash floods, or infrastructure failures, the system generates timely alerts. Moreover, predictive models provide early warnings about infrastructure deterioration, enabling critical stakeholders to respond proactively and adapt societal operations accordingly.

References

[1] Michalis, P., Vintzileou, E. (2022). The Growing Infrastructure Crisis: The Challenge of Scour Risk Assessment and the Development of a New Sensing System. Infrastructures, 7(5), 68. https://doi.org/10.3390/infrastructures7050068

[2] Xu, Y., AlObaidi, K., Michalis, P. and Valyrakis, M. (2020). Monitoring the potential for bridge protections destabilization, using instrumented particles. Proceedings of the International Conference on Fluvial Hydraulics River Flow, Delft, The Netherlands, 7–10 July 2020; pp. 1-8. eBook ISBN 9781003110958.

How to cite: Michalis, P., Konstantinidis, F., Katika, T., Michalis, A., and Valyrakis, M.: Leveraging Digital-Physical Integration for Enhanced Infrastructure Management, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16062, https://doi.org/10.5194/egusphere-egu25-16062, 2025.

The Siwalik strata of the Indian subcontinent are renowned for their rich vertebrate fossil assemblages, particularly mammals, spanning approximately 18 to 0.22 million years ago. However, squamate reptiles well known for their diverse morphology and ecological adaptations, remain underexplored in this region, reflecting a significant gap in our knowledge of Miocene herpetofauna. A comprehensive study of Miocene squamate vertebral morphology in India has yet to be undertaken. This research examined the vertebral morphology of squamate fossil remains from Siwalik localities, including the Middle Miocene Ramnagar (Jammu) and Late Miocene Haritalyangar (Himachal Pradesh), for taxonomic identification and ecological insights through comparisons with extant taxa. The collected specimens were analysed using a micro-CT and a Stereozoom microscope (10X). Identification and examination were conducted based on key morphological characteristics, including overall size and shape, cotyle and condyle dimensions, the presence or absence of zygosphene and zygantrum, the number and arrangement of ventral keels, the presence of foramina, the shape of the neural canal, and the occurrence of hypapophyses. The examined samples reveal the presence of various taxa, including Acrochordus, Anguimorpha, Colubridae, Constrictores, Python, and Varanus. Notably, the presence of fully aquatic piscivore Acrochordus from Late Miocene Haritalyangar (10–8.5 Ma), based on a single probably surface-collected specimen, appears to be artifactual and requires further investigation. However, the high diversity of thermophilic lizards and snakes dominated by Python and colubrids during the Miocene period indicates elevated mean annual temperatures. The coexistence of terrestrial and semi-aquatic squamates suggests a seasonally wet, sub-humid to semi-arid climate.

How to cite: Deep, S.: A Comparative Analysis of Vertebral Morphology of Middle to Late Miocene Squamates from the Siwaliks of India: Paleoenvironmental Implications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-261, https://doi.org/10.5194/egusphere-egu25-261, 2025.

During the Miocene (c. 23–10 Ma), climatic and tectonic changes led to the development of a large wetland with shallow lakes and swamps in Western Amazonia (Hoorn et al. 2010). These new aquatic environments of the “Pebas” system were colonized by rapidly evolving endemic invertebrate faunas composed of mollusks and ostracods (Wesselingh, 2006; Purper, 1979; Sheppard & Bate, 1980, among others). The ‘Pebasian’ ostracods hold a highly endemic and diverse fauna, which led to the description of several new genera and species.

The goals of this study are to review the taxonomy of Amazonian Perissocytheridea species, analyze their intraspecific variability and ontogenetic development, and to identify evolutionary pathways.

We studied samples from eight localities in the Iquitos region (Peru) covering the Middle Miocene mollusk biozones MZ4–MZ9 (Wesselingh et al., 2006).

We identified two species: Perissocytheridea sp. 1 and Perissocytheridea sp. 2, both of which appear to be endemic to the Pebas system. Remarkably, the specimens belonging to Perissocytheridea sp. 2 display ‘inverse’ hinges. The two species co-occur in different stratigraphic sections, with Perissocytheridea sp. 2 being less abundant in all samples. Both species exhibit a kind of premature sexual dimorphism from the juvenile stages A-1 to A-3. Additionally, polymorphism was found in specimens of Perissocytheridea sp. 1, manifested in variations in surface ornamentation, in size and shape of the alar and caudal process.

So far, no chronological trend has been established and other features remain to be compared (e.g., inner lamella, pores).

Although there are many references to ‘Pebasian’ ostracods with ‘inverse’ hinges, all of them were documented in the genus Cyprideis (Purper & Pinto, 1983, 1985; Whatley et al. 1998; Gross et al. 2013, 2014). Here, ‘inverse’ Perissocytheridea is reported for the first time. The presence of these ‘inverse’ forms could explain reproductive isolation and therefore, sympatric speciation, as suggested for the ‘Cyprideis species flock’ (Gross et al. 2014). In any case, the trigger for the occurrence of these ‘inverse’ forms in ‘Pebasian’ ostracods is still unknown.

Finally, we prefer not to assign the specimens to already described Perissocytheridea species from the Pebas system, as potential synonyms are still under study.

How to cite: Zamudio, M. B., Gross, M., Salazar Rios, A., and Piller, W.: Perissocytheridea (Ostracoda, Crustacea) from Western Amazonia (Middle Miocene), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1570, https://doi.org/10.5194/egusphere-egu25-1570, 2025.

Fusulinids, the earliest recorded group of larger benthic foraminifera, first appeared in the Early Carboniferous and flourished from the Late Carboniferous to the end of the Middle Permian. Their most notable diversification occurred during the Late Carboniferous to the earliest Permian, coinciding with the peak of the Late Paleozoic Ice Age (LPIA). Understanding in more detail the link between fusulinid diversification and climate changes could provide a unique perspective on evolutionary responses to climatic variability. Here, based on newly established patterns of high-temporal-resolution species richness and factor analysis, we recognize four evolutionary faunas akin Sepkoski’s evolutionary faunas. The four evolutionary faunas are pre-LPIA, early-LPIA, late-LPIA, and post-LPIA. These evolutionary faunas are characterized by long decline patterns (pre-LPIA and early-LPIA faunas), and extinction patterns with sudden eliminations of the whole fauna (late-LPIA and post-LPIA faunas). Further analyses revealed that the magnitude of climatic changes played a key role in shaping different diversity trajectories of fusulinid evolutionary faunas and the succession of faunas. Our findings offer insights into how different levels of climatic changes would influence global biodiversity over geological timescales.

How to cite: Zhang, S., Shi, Y., Shen, S., and Kiessling, W.: Fusulinid Evolutionary Faunas of the late Paleozoic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1925, https://doi.org/10.5194/egusphere-egu25-1925, 2025.

      At present, research on the sedimentary configuration of river facies at sea focuses on the identification and characterization of different levels of interlayers, and there are the following problems: (1) the accuracy of predicting and characterizing the heterogeneity of physical properties within different levels of configuration units in river facies reservoirs is low, and there is a lack of methods and means; (2) The remaining oil distribution pattern controlled by the differences in physical properties of different levels of configuration units in the later stage of ultra-high water content is unclear. After more than 20 years of development, Qinhuangdao 32-6 Oilfield has entered the late stage of ultra-high water cut development, with a comprehensive water cut of 96.8%. After long-term high fold water flooding, the advantageous seepage channels have developed, and the continuous deep tapping of the main sand body faces great challenges.
      In response to the above issues, this article uses sedimentary genesis models as constraints to quantitatively characterize and characterize configuration units at different levels. Based on this, the influence of different levels of configuration units in river facies on the distribution of remaining oil is studied, forming a set of multi-level quantitative characterization methods for the internal structure of reservoirs in different levels of configuration units in river facies. The specific steps are: (1) Summarize the quality difference patterns of different levels of configuration units in river facies, as well as the geological knowledge base including lithofacies and configuration unit types, configuration unit structural styles and parameters, reservoir physical property parameters, etc. (2) Establish two-dimensional and three-dimensional prototype geological models of reservoir quality differences in configuration units, and carry out simulation of fluvial facies sedimentation. (3) Based on the prototype geological model, 3D seismic forward simulation is conducted to study the seismic response characteristics of reservoir configuration unit quality differences, and a feature map is established. The quantitative characterization of reservoir configurations based on different levels of configuration units not only enriches the research content of reservoir configurations, but also provides theoretical support for the characterization of heterogeneity in fluvial reservoirs.

How to cite: li, S.: Quantitative characterization of reservoir quality differences in different levels of configuration units: a case study of typical fluvial sand bodies in Qinhuangdao 32-6 oilfield, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3265, https://doi.org/10.5194/egusphere-egu25-3265, 2025.

The PG2 sandstone volatile oil reservoir, located in the Es1 formation of the Nanpu Depression is a lake-bottom fan sedimentary reservoir with significant internal heterogeneity. This heterogeneity is characterized by the development of interlayers and barrier layers, which result in complex seepage characteristics during the process of converting oil reservoirs into gas storage. The transportation and distribution patterns of the reservoir fluid are not well understood. Therefore, it is crucial to study the sedimentary architectural pattern and the distribution characteristics of architectural units to clarify the heterogeneity of the reservoir and the fluid transportation and distribution rules. This would provide theoretical support for the subsequent construction of the gas storage and help identify the favorable reservoir areas. To address these issues, this paper systematically quantifies and characterizes the architectural interfaces and units in a hierarchical order, guided by the sedimentary genetic model. On this basis, a multi-level architectural method is developed for quantitatively characterizing the internal structure of the reservoir. The specific steps are as follows: (1)After establishing that the seventh order consists of composite genetic units formed by multiple single-phase sandy debris flow events, while the eighth order is a single genetic unit formed by a single-phase sandy debris flow event, the architectural interface between the seventh and eighth orders of the reservoir is quantitatively characterized. As there are no horizontal well in the study area at the target interval, empirical formulas for single watercourses and beds in lake-bottom fans, developed by previous scholars, are applied. The structural unit boundaries in areas without wells are determined through a combination of empirical formulas, inter-well comparisons, and data from the geological knowledge base. This process is used to define the scale of the architecture units, and the relevant parameters are then statistical counted. (2)Based on the identification of architectural interfaces, the study focuses on the classification, recognition, and distribution of the seventh and eighth order architectural units. The distribution characteristics of these different architectural orders are depicted in detail, and a developmental model for the eighth-order architectural units is established. Finally, the results of the reservoir architectural characterization are verified using dynamic production data, which confirms that the method accurately characterizes the internal structure of the reservoir and quantitatively describes its internal heterogeneity and fluid transport and distribution patterns. This provides theoretical support for identifying favorable reservoir areas for converting oil reservoirs into gas storage.

How to cite: Li, X. K. and Zhang, X.: Architecture Characteristics of Lake-Bottom Fan Sedimentary Reservoir: A Case Study of the PG2 Oil Reservoir, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3692, https://doi.org/10.5194/egusphere-egu25-3692, 2025.

Mollusc shells are composite structures built of calcium carbonate crystals (calcite and/or aragonite) and biopolymers (protein, polysaccharides and lipids). These two classes of materials create a great variety of microstructures characterised by complex architectures and unique material properties. The formation of shell microstructures is controlled by environmental and physiological factors and the variety of microstructures is believed to be of phylogenetic and adaptive biomechanical significance. Here, through SEM and XRD analyses, we provide for the first time a detailed characterisation, description and illustration of the shell microstructure and mineralogy of three mollusc species: the bivalves Anadara uropigimelana (Bory de Saint-Vincent, 1827) and Tivela stefaninii (Nardini, 1933), and the gastropod Oliva bulbosa (Röding, 1798). The specimens were collected in the Upper Holocene HAS1 settlement and in a shell midden in the Khor Rori Archaeological Park (Oman). These species frequently occur in archaeological assemblages and show clear growth lines and increments in their shells, making them excellent tools to be used for high resolution palaeoclimatic and palaeoenvironmental studies. However, data on their shell microstructure and mineralogy, that are fundamental for fossil shell preservation analyses, are lacking. Our results show that shells of Anadara uropigimelana are aragonitic with an outer crossed lamellar layer, an inner complex crossed lamellar layer and an irregular simple prismatic pallial myostracum; periodic bands of dendritic nondenticular composite prisms occur in the outer part of the outer layer, reflecting seasonal changes in water temperatures and growth rates. Tivela stefaninii shells are aragonitic and show an outer composite prismatic layer, a middle crossed lamellar layer, and an inner complex crossed lamellar layer. Shells of Oliva bulbosa are composed of an irregular alternation of aragonitic crossed lamellar layers; a transitional layer characterised by the occurrence of tidally controlled growth lines, a crossed lamellar callus and a myostracal layer are also described in Oliva bulbosa specimens. With this analysis, we are able to provide novel microstructural and mineralogical data on three poorly known mollusc species, which are useful for crystallographic, phylogenetic, evolutionary and palaeoenvironmental studies.

How to cite: Chiari, A., Dapiaggi, M., and Crippa, G.: Investigating the shell microstructure and mineralogy of three Upper Holocene mollusc species from the Khor Rori Archaeological Park (Dhofar, Oman), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3699, https://doi.org/10.5194/egusphere-egu25-3699, 2025.

Glauconites are abundant in Paleocene Alaji Formation and Eocene Jaddala Formation.  This study highlights the influence of depositional conditions on mineralogical and chemical composition of Palaeogene glauconites in Iraq. Petrographical, textural, mineralogical, and chemical characterization were done on Paleogene green clays. The green clays were examined in marl and limestone, in proximal (Kirkuk section), medial (B 12/7 and Gharaf sections), and distal (B 15/7 sections) sections of the basin, formed in middle shelf, outer shelf, and upper slope to upper-middle slope conditions, respectively. The green clays are found in an upward fining sequence and condensed sections. The sedimentary aspects indicate a transgressive systems tract and maximum flooding surface condition of formation of the green clays. The green clays appear light to dark green under microscope and are ~30 µm to ~1000 µm long. The green clays occur as pellets, and as infillings in foraminifera, algae, showing radiating cracks. The medium to poor sorting of green clays, showing radiating cracks indicates their authigenic origin. Microstructurally, the green clays show well-developed flaky and rosette structures. The presence of well-developed lamellar texture indicates evolved character of the green clays. The green clays show ~10 Å (001), 4.53 Å (020), 3.32 Å (003) and ~1.511 Å (060) reflections, which are characteristic of glauconite. The distal glauconites show better-developed spectra with narrower and more intense reflections and a 10 Å (001) reflection (FWHM: 0.43 °2θ), compared to the proximal glauconites with a 10.5 Å (001) reflection (FWHM: 1.11 °2θ). Upon glycolation, the distal glauconites show no shift in the d-spacing of (001) reflection (10.02 Å), with hardly any increase in peak width (FWHM: 0.54 °2θ), while the proximal glauconites show some shift in the d-spacing of (001) reflection (10.15 Å) with minor increase in peak width (FWHM: 1.33 °2θ). These mineralogical observations indicate better-ordered crystal structure in the distal glauconites, compared to the proximal glauconites, with lower smectite content in the distal glauconites. Medial and distal glauconites contain > 15% to ~27.5% Fe₂O₃(total), ~6% to ~10% K₂O, ~2.5% to ~12.5% Al₂O₃, and ~4% to ~6% MgO, while the proximal glauconites show < 15% to ~10% Fe₂O₃(total), ~7% to ~8% K₂O, > 12.5% to ~15% Al₂O₃, and ~6% to ~8% MgO. The chemical nature of the medial and distal green clays indicates a glauconite affinity, while the proximal green clays are High-Mg, Al-glauconites. The medial and distal glauconites formed in a deeper setting, where sedimentation rates are low and detrital Fe-rich particles are available. While, the proximal glauconites formed in a shallower setting close to the Zagros ophiolite belt, where sedimentation rates are high and Mg-Al-rich detrital particles are available. Lower sedimentation rates favor higher evolution of glauconites. Thus, the medial and distal glauconites formed on a Fe-rich precursor like Fe-Al smectite, while the proximal glauconites formed on an Mg-Al rich precursor like Mg-Al phyllosilicate, with higher evolution of the medial and distal glauconites. The high abundance of the glauconites is attributed to the Paleocene-Eocene thermal maximum, as warm seas favor higher kinetics of the reaction.

How to cite: Sarin, T., Banerjee, S., Zaki, N., Farouk, S., Al-Kahtany, K., and Mohammed, I. Q.: The influence of depositional conditions on the crystallo-chemical characteristics of Paleogene glauconites of Iraq, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3733, https://doi.org/10.5194/egusphere-egu25-3733, 2025.

Fan deltas are usually constructed through episodic flood event with debris flow transforming to hyper-concentrated flow during sediments proceeding. However, the role of topography in controlling the flow transformation and sediments aggradation has been less studied. This constrains studies of sediment distribution and understanding of graded profile. For lake basin sequences, geomorphological control is much stronger than lake level rise and fall. Under extreme conditions, sediments can still prograde when the lake level rises. Therefore, describing the influence of geomorphology on the flow transformation and stacking pattern of the lobes can provide a deeper understanding of the controlling factors of the lake basin stratigraphy sequence. Xiligou lake (XLG) fan delta from Xisai Basin provides an optimal case for addressing this issue. Three lobes developed on the XLG fan delta with significant differences in their morphologies, architectures, lithofacies, sediment distributions and topographies. Through trenching, drone photography, and satellite data, we analyzed the structure of the sediments and the distribution of sedimentary facies. Based on the analysis of debris flow and hyper-concentrated flow deposits, two transformation models corresponding to different topographies were established. Sediment unloading is caused by a frictional reduction or a sudden momentum loss in the sediments flow's carrying capacity, allowing the debris flow transforms to hyper-concentrated flow and then to stream flow during the movement. The role of topography in controlling sediment flow transformation and sediment distribution is clarified through forces analysis of sediment grain. The topographic gradient of the linear slope is constant, so the direction of fluid movement is consistent with the topographic direction. Therefore, sediment flows move on linear slope without collision with the bed and there is no sudden loss of momentum. The gradual or sudden reduction in topographic gradient of concave slopes forces a constant or sudden change in the direction of fluid movement, which facilitates the unloading of sediments and the transformation of flow. The sudden change of topography forces unloading of viscous component, and the non-viscous component pass over to form hyper-concentrated flow, often accompanied by remobilized large gravels. The graded profile was an equilibrium between the dynamics and resistance of sediment transport. Changes in lake level affect the graded profile by changing the elevation of sediment transport, which is the total gravitational potential energy. The instantaneous graded profile and temporary graded profile are different scales of equilibrium corresponding to hydrodynamic equilibrium and depositional trend respectively. This study reveals the role of geomorphological dynamics in controlling sedimentary body progradation, thus providing a new perspective on the analysis of lake basin stratigraphy sequence.

How to cite: Li, S., Sun, H., and Li, P.: Morpho-dynamics in fan deltas: Effect of topography on flow transformation, facies distribution and graded profile evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4143, https://doi.org/10.5194/egusphere-egu25-4143, 2025.

  Due to the difficulty and high cost of core data, it is very important to use the logging data to continuously identify and divide the longitudinal upper stria structure types of a single well. The conventional logging resolution is mostly decimeter to meter level, while the high-resolution imaging logging resolution can reach 5 mm, and the imaging logging dynamic and static images obtained on the basis of the resistivity scale can clearly reflect the bedding changes of the formation, which is an important means for fine identification and characterization of the streak. However, it takes a lot of work to manually identify the type and thickness of the striae, and the thickness of the striae is difficult to observe intuitively with the naked eye.

  This study presents a machine learning and wavelet transform-based method for extracting and recognizing texture layer characteristics and thickness from imaging well logging images. Grayscale images are obtained from well logging slices, and grayscale curves are extracted at the fourth quartile. An average grayscale curve is constructed, and wavelet transform is applied to remove noise, yielding a transformed curve. Grayscale differences between pre- and post-transformation curves are calculated to form a difference curve. These grayscale values and differences serve as clustering features, classifying texture layers into four types. Texture layer thickness is then statistically analyzed based on these types. The method enables automated texture layer and thickness recognition, enhancing accuracy and efficiency in feature extraction.

How to cite: Li, X.: FMI image lamina features and thickness extraction and recognition method basedon machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4678, https://doi.org/10.5194/egusphere-egu25-4678, 2025.

The determination of sedimentary facies and the fine division of sedimentary microfacies are of great significance for oil and gas exploration, it not only helps to find new blocks of oil and gas potential, but also points out the direction for the fine development of old oilfields. Taking the Shahejie Formation in Huanghua Depression as an example, the sedimentary environment and sedimentary model were studied by comprehensive utilization of core data, logging, seismic and analytical test data, and the following research results were obtained :

(1) Using core data to identify the development of fan delta facies deposits in the study area, and according to the type of lithofacies, the hydrodynamic conditions of the reduction fan deposition period are divided. Eight lithofacies types are identified in the study area, which are massive bedding pebbly sandstone facies, massive bedding sandstone facies, parallel bedding sandstone facies and wavy bedding sandstone facies formed under strong hydrodynamic conditions. Horizontal bedding siltstone facies, lenticular bedding siltstone facies, massive argillaceous siltstone facies and massive mudstone facies formed under weak hydrodynamic conditions ;

(2) Four types of sedimentary microfacies were identified by well-seismic combination method, and the spatial distribution characteristics of sedimentary microfacies were quantitatively characterized. That is, the source direction has the characteristics of contiguous distribution of fan delta sand bodies close to the source and dendritic distribution of sand bodies far from the source ; in the direction of vertical provenance, the lateral migration of fan delta sand bodies leads to the superposition of sand bodies. The cross-well sections along the source and vertical source reveal that the fan delta sand body is retrograded to the source area;

(3) The difference of reservoir quality is characterized by comprehensive utilization of logging and analysis test data. The study shows that there are five reservoir types in the retrograde fan delta facies, and the difference of reservoir quality is closely related to the type of sedimentary microfacies. There are also significant differences in reservoir quality within the same microfacies;

(4) Through comprehensive analysis, the development characteristics of retrograde fan delta facies sand bodies under ' model constraint and well-seismic combination ' are clarified. This kind of sedimentary model is helpful to better describe the reservoir, determine the potential block through the dominant facies, and lay a foundation for tapping the potential of remaining oil.

How to cite: Yang, Y. and Wei, T.: Study on sedimentary evolution characteristics and sand body distribution law of regressive fan delta, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4733, https://doi.org/10.5194/egusphere-egu25-4733, 2025.

Accurate lithofacies identification plays a crucial role in the exploration and development of shale oil reservoirs, while existing methods all have their own shortcomings. In this paper, focusing on the shale oil reservoirs in the Weixinan Sag of the Beibu Gulf Basin, a particle swarm optimized random forest (PSO-RF) algorithm was proposed for lithofacies identification. Firstly, based on the core characteristics in the study area, nine lithofacies were classified with mineral composition, grain size, and sedimentary structure as the main factors. After that, principal component analysis method was used to reduce the dimensionality of the logging data and eliminate redundant information among the logging curves. Finally, particle swarm optimization algorithm was employed to search for the optimal hyperparameters of the random forest model, which is the PSO-RF algorithm. Compared with the results of core observations, the lithofacies identification results of cored wells in the study area demonstrated the effectiveness of the PSO-RF algorithm, achieving an overall accuracy of 90% on the test set. In Addition, the PSO-RF model showed excellent adaptability when applied to non-cored wells, with prediction results that outperform traditional machine learning algorithms. This study provides an effective method for lithofacies identification in the Beibu Gulf Basin and similar shale oil reservoirs.

How to cite: Li, Y., Zhao, M., and Wei, X.: Lithofacies Identification by a Particle Swarm Optimized Random Forest Algorithm in Shale Oil Reservoir, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5450, https://doi.org/10.5194/egusphere-egu25-5450, 2025.

Mesophotic (30–150 m) and deep reef (> 150 m) paleo-communities are significantly less studied in the Central Mediterranean, limiting our understanding of their development across this region. The Terrible and Nameless Banks in the Sicily Channel present a valuable opportunity to investigate these ancient ecosystems, offering insights into the processes that shaped deeper reef communities around these structures.

Here, we examined carbonate rocks collected from mesophotic to deeper settings on the Terrible and Nameless Banks. We aimed to describe the carbonate bioconstruction surrounding these structures and to understand the processes that led to their evolution. Carbonate rocks and fossil samples have been collected using rectangular chain bag dredges during the R/V Meteor expedition M191. A total of 50 carbonate samples, including well-lithified carbonate crusts and dead benthic organisms, have been described, of which 20 have been cut and prepared for thin-section analysis.

Samples recovered from mesophotic depths of both Terrible and Nameless Banks show that paleo-reefs associated with these depths are mainly associated with coralline algae-rich facies. Highly bioeroded coralline boundstone is associated with fragments of corals, bryozoans, and serpulids. The free-living form of coralline algae, rhodoliths, are also significant contributors to mesophotic ecosystems. Rhodoliths are 2 to 5 cm in size, showing spheroidal to ellipsoidal morphologies, with growth forms ranging from encrusting, warty to fruticose, lumpy. Coralline algae typically encrust various lithified rocks, including sedimentary and volcanic rocks, which can serve as nuclei for their growth. These encrusted rocks are often further covered by fenestrate bryozoans and encrusting foraminifers. Coral species at this depth are represented by Corallium rubrum (red coral) and Dendrophyllia sp. In the deeper regions of the banks, down to a depth of 655 meters, the carbonate samples consist primarily of lithified, hard rocks, and no coralline algae have been observed. The paleo-communities are mainly represented by cold-water coral species such as Lophelia pertusa, Desmophyllum dianthus, and Dendrophyllia alternata. Additionally, colonies of deep-water oyster-coral framestone, possibly Neopycnodonte zibrowii-Desmophyllum association, are present.

Our initial results show that the presence of sufficient light in the mesophotic zone is an important factor for the thriving of coralline algae-related facies. The specific topography of the Terrible and Nameless Banks creates moderate to strong currents around these structures, prevents sediment burial, and promotes the rolling and shaping of rhodoliths into rounded forms. These currents also produce local upwelling around banks, bringing cool, nutrient-rich water from deeper depths to the mesophotic zone and enhancing the development of corals and bryozoans. In deeper waters, internal waves can play a significant role in nutrient delivery, sustaining the biogenic communities such as coral and oyster assemblages.

How to cite: Kiani Harchegani, F., Coletti, G., Bialik, O., Micallef, A., and Geldmacher, J.: Paleo-communities across the mesophotic to deep zones of the Terrible and Nameless Banks, The Sicily Channel, Central Mediterranean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6926, https://doi.org/10.5194/egusphere-egu25-6926, 2025.

The Slovenian Basin (the eastern Southern Alps, Slovenia) formed during the Middle Triassic and lasted until the end of the Mesozoic. The oldest succession belongs to the Ladinian volcanic- and clastics-dominated Pseudozilian Formation, followed by the Carnian Amphiclina Formation, composed of shale, sandstone, subordinately conglomerate and bedded limestone. Several sections were documented by Skaberne et al. (2024) in the southern part of the Tolmin Nappe (subunit of the Southern Alps), but only one succession was logged from more northern parts of the Tolmin Nappe (Gale et al., 2017). Consequently, little is known about Carnian paleotopography of the basin. To augment current knowledge on the lateral differences within the Amphiclina Formation, a succession was logged on the Martinj Vrh hill, structurally situated in the middle part of the Tolmin Nappe. The entire succession is 47.3 m long and ends at the transition to the Norian-Rhaetian Bača Dolomite Formation. According to conodont data, this stratigraphic boundary corresponds to the Carnian-Norian boundary. The rocks were analysed using optical microscopy, XRD, and μ-EDRF. The outcrop consists of bedded fine-, medium- and coarse-grained sandstone, marlstone, mud-supported conglomeratic breccia, conglomeratic breccia with carbonate cement, and bedded limestone with occasional occurrences of dolomite. Parallel and cross-lamination, load casts, ball and flame structures, scour structures, slumps and synsedimentary faults are present. Limestone is mudstone-wackestone with radiolaria, filament and bioclastic wackestone, echinoderm-intraclastic packstone, filament-peloidal packstone-grainstone, intraclastic-peloid packstone-grainstone, peloidal grainstone, and rudstone. Position within the basinal area cannot be directly determined, although the sedimentary structures suggest that sedimentation took place on the basin slope. Comparison with previously published logs shows that sedimentation within the basin greatly varied and that no clear distinction can be drawn between different parts of the Tolmin Nappe. This is probably due to complex internal topography of the basin.

Gale et. al. 2017: Characterization of silicified fossil assemblage from upper Carnian "Amphiclina beds" at Crngrob (central Slovenia). Geologija, No. 60/1, pp. 61–75.

Skaberne et. al. 2024: Middle Triassic deeper-marine volcano-sedimentary successions in western Slovenia. Geologija, No. 67/1, pp. 71–103.

How to cite: Pristavec, M., Rožič, B., and Gale, L.: Carnian clastic-carbonate succession from the Slovenian Basin (Southern Alps), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8136, https://doi.org/10.5194/egusphere-egu25-8136, 2025.

The polar oceans are critical in regulating atmospheric CO₂ concentrations (pCO₂) during Pleistocene glacial cycles. However, the role of the subarctic Pacific, despite being the largest reservoir of respired carbon in the modern ocean, remains underexplored due to limited data. This study presents high-resolution export productivity records, normalized using 230Th, from the subarctic northwestern Pacific spanning the last five glacial cycles. These records reveal distinct glacial-interglacial patterns overlaid with variability driven by precession. Warm interglacial climates, coupled with high boreal summer insolation, facilitated the upwelling of nutrient-rich subsurface waters, leading to increased export productivity. Transient model simulations demonstrate that ice sheet dynamics and, to a lesser extent, precession significantly influence the strength and latitudinal shifts of the westerlies. Intensified and poleward-shifting northern westerlies during warmer intervals likely enhanced the upwelling of carbon- and nutrient-rich waters, releasing previously stored CO₂ from the subarctic Pacific into the atmosphere. These findings underscore the substantial influence of the subarctic Pacific in regulating pCO₂ variations during Pleistocene climate cycles, particularly on the precessional timescale (~20 kyr).

How to cite: Yao, Z., Shi, X., and Yin, Q.: Productivity and upwelling changes in the Subarctic Pacific over the past five glacial cycles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8165, https://doi.org/10.5194/egusphere-egu25-8165, 2025.

In the year 2014 the so far oldest Bavarian fossil (a typical archaeocyathid hollow horn formed sponge) with an age of ~520 ma was identified near Schwarzenbach/Wald (north-east Bavaria-Germany).

Recently, the Bavarian Environment Agency started the hunt for a new oldest Bavarian. In 1988 Reitz and Höll described one specimen of Acritarcha with moderately bad preservation of the Prasinit-Phyllit-Series (PPS) of north eastern Bavaria and claimed a pre-Cambrian age for the deposit. Nevertheless, recent studies show that a continuative pre-Cambrian or even Cambrian age of the PPS cannot be provided and therefore the biostratigraphic dating has to be checked intensely.

Therefore, analyses of three different outcrops (Sparneck and Schwarzenbach/Saale outcrop 1 and 2) have been conducted to test and/or verify the pre-Cambrian age.

If a pre-Cambrian age can be confirmed and suitable Acritarcha of the PPS can be found and identified, this will not only be the oldest Bavarian but also the oldest confirmed German (fossil) ever found.

How to cite: Kranner, M.: The hunt for the oldest Bavarian – Acritarcha of the Prasinit-Phyllit-Series (Münchberg Massif), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8210, https://doi.org/10.5194/egusphere-egu25-8210, 2025.

Deep marine gaps are topographical choke-points where constricted bottom currents may interact with down-slope gravitational flows originating from surrounding topographic highs. Such gaps can provide unique insight into processes understudied in abyssal settings: pure contouritic systems and mixed (turbidite-contourite) systems. Here, we present a detailed study of the Theta Gap, a deep marine gap that connects the Biscay Abyssal Plain and the Iberian Abyssal Plain. Previous studies identified significant erosion and deposition of turbidites but only focussed on the area between the Finisterre and A Coruña Seamounts. The processes occurring between the Galicia Bank and the Finisterre Seamount are less defined. Our aim was to compare these two areas within the Theta Gap to determine if the south Theta Gap contributes to the exchange of Lower Deep Water between the abyssal plains and how this affects sediment deposition. To achieve this aim, we used sub-bottom profiles along with a detailed analysis of four sedimentary cores, to study the sedimentary facies across the two areas. Hydrological data was used to assess to what degree Lower Deep Water and associated bottom currents are contributing to sediment distribution in the gap. We found clear differences in turbidite deposition between the north and south Theta Gap. The same event often has thinner and coarser deposits in the north compared to the south. In the south, the turbidite sequences are thicker, more complete and include discontinuous silt laminae and mud/silt couplets. The distribution of iostherms and isopycnals in the Theta Gap suggest that Lower Deep Water flows north-eastwards through the south Theta Gap before recirculating and flowing south-westwards through the north Theta Gap. We hypothesise, the discrepancy in turbidite distribution is greatly controlled by these bottom currents which foster deposition in the south Theta Gap and, at times, prevent deposition in the north Theta Gap. Such bottom current – sediment interactions are understudied in abyssal settings and deep marine gaps, such as the Theta Gap, can provide unique insight into these processes of sediment transport and reworking.

How to cite: Glazkova, T., Llave, E., Maestro, A., Dickson, A. J., Francés, G., and Hernández-Molina, F. J.: Sedimentary Processes in the Theta Gap, NE Atlantic , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9547, https://doi.org/10.5194/egusphere-egu25-9547, 2025.

The Aptian-Albian deposits of the Anglo-Paris Basin consist of terrigenous sediments formed in shallow continental and coastal environments within an extensional intracratonic basin. The Aptian-Albian interval is rarely exposed, except in the Wessex Basin, where subsiding sub-basins developed during the Early Cretaceous and were later exposed due to tectonic inversion (Chadwick, 1993). Outcrops in southern England, Cap de la Hève (Normandy), and Burgundy quarries complement subsurface data from Paris Basin drill cores. Stratigraphic correlations from wireline logs and outcrops at the basin's margins have highlighted nine transgressive/regressive cycles constrained by biostratigraphy, showing subsidence variations between the Paris and Wessex Basins.

The Lower Aptian deposits are affected by the sub-Aptian discordance. In the Paris Basin, many ammonite-bearing zones are absent due to significant erosion, and the Lower Aptian deposits consist of marine shales. This interpretation is supported by signs of reworking, attributed to localized tidal influences, ruling out offshore deposition. In contrast, the Lower Aptian in the Wessex Basin is unaffected by the sub-Aptian unconformity and records thick sand layers resulting from deltaic progradation eastward, with significant subsidence located in the Isle of Wight (Channel Basin).

During the Upper Aptian, southern England and the English Channel are marked by lower subsidence and are characterized by estuarine deposits of the Sandrock Formation. In the Paris Basin, Late Aptian subsidence was also significant and accompanied by major hiatuses in ammonite’s zones, with the Sables Verts deposited in estuarine and tidal-dominated environments overlying an unconformity. The Wessex and Paris basins were separated by the "Hampshire-Dieppe” structural High (Jollivet-Castelot 2018), forming the northern boundary of the Paris Basin.

The onset of the Albian marks a shift in dynamics between the Paris and Wessex Basins. In the Wessex, reduced subsidence led to continental sedimentation (Monk’s Bay Sandstone Formation) over an erosion surface. Meanwhile, increased subsidence in the Paris Basin resulted in the deposition of the Sables des Drillons, indicating a shift from transgressive tidal-dominatedsands to regressive shoreface deposits. Structural highs in the northern basin continued to limit communication between the basins.

The Middle Albian is characterized by diachronous subsidence between the Paris and Wessex Basins. In Wessex, the Gault Clay Formation was deposited due to significant subsidence, while in the Paris Basin, this period corresponds to the deposition of the Sables de Frécambault, indicating littoral sands progradation followed by offshore clay deposits with Gault facies at the top of the Middle Albian. This marks the first communication between sub-basins, forming the Anglo-Paris Basin. The  top of the Middle Albian is marked by a significant regression, with incised valleys filled with fluvio-estuarine deposits, preceding the major Late Albian transgression marked by shale sedimentation with Gault facies, heralding the major Cenomanian transgression.

The Upper Albian is marked by homogeneous subsidence in both basins, strengthening communication with marine domains such as the North Atlantic and North Sea (Amédro and Matrion, 2014). In the Wessex, tidal-dominated shallow marine deposits (Upper Greensand Formation) transition eastward into outer platform deposits (Rawson, 2006), while in the Paris Basin, the Late Albian corresponds to outer platform deposits (Gault Formation).

How to cite: Seguin, F., Deschamps, R., Patrier, P., Lasseur, E., Briais, J., and Souque, C.: Sedimentary dynamics of the Anglo-Paris Basin during the Aptian-Albian period, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9690, https://doi.org/10.5194/egusphere-egu25-9690, 2025.

The Central Anatolian Plateau (CAP) has played a dynamic role in the Africa-Eurasia convergence system since the mid-Mesozoic. It has been influenced by various geological processes, including lithospheric delamination, slab segmentation (specifically the Cyprus and Antalya slabs), tilting, and slab break-off. The southern margin of the CAP, marked by the Central Taurides, is unconformably overlain by Neogene marine sedimentary deposits from the Mut and Antalya basins. To better understand the mechanisms driving the Middle Pleistocene uplift, we present new evidence from a marine succession (Tol-1 section) of the Mut Basin, located at 1171 m a.s.l. Tol-1 section is approximately 71 m thick and consists of marls, clayey marls, and occasional calcarenite layers, indicating a shallowing-upward sequence. The calcareous nannofossil analysis revealed two key bioevents: the Last Occurrence (LO) of Pseudoemiliania lacunosa (0.46 Ma), in the midsection, and the First Occurrence (FO) of Emiliania huxleyi (0.26 Ma), near the top. Although the abundant reworked specimens, these taxa provide reliable chronological markers. The FO of E. huxleyi and the estimated sedimentation rate for the top of the Tol-1 section point to an age of ca. 0.21 Ma (Marine Isotope Stage, MIS 7) for the youngest marine deposits of the Mut Basin. Ostracod taphonomy suggests paleobathymetric conditions ranging from littoral to upper epibathyal environments (depths not exceeding 400 m). Paleomagnetic analysis confirms Brunhes' normal polarity, supporting a late Middle Pleistocene age for the Tol-1 section. So far, this section is identified as the youngest marine deposits reported at this elevation along the southern margin of the CAP. By combining our age constraints, the paleobathymetry of the top section (50 m b.s.l.), and the eustatic sea level during the late Middle Pleistocene (~-18.5 m), we estimate an uplift rate of ~5.9 m/kyr for the southern margin of the CAP. This uplift may be induced by the upwelling of low-density asthenospheric mantle following slab break-off as suggested in previous studies (Faccenna et al., 2006; Keskin, 2003; Cosentino et al., 2012; Schildgen et al., 2014; Öğretmen et al., 2018; Racano et al., 2020; 2021).

How to cite: Sari, S., Cipollari, P., Cosentino, D., Gliozzi, E., Lirer, F., Kanbur, S., Öğretmen, N., Mattei, M., Cifelli, F., and Faranda, C.: The Middle Pleistocene uplift of the Central Anatolian Plateau (CAP) southern margin: New evidence from the Mut Basin (South Turkey)  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10350, https://doi.org/10.5194/egusphere-egu25-10350, 2025.

We present heavy minerals, detrital zircon data and U-Pb tuff ages from the sedimentary units of the Yukon-Koyukuk Basin (YKB) in Alaska, to investigate and understand its evolution within a tectonic framework. Two basins in Southeast Asia, with similar tectonic settings, serve as modern analogues for comparison. The YKB started to form in middle to late Jurassic after the collision between an intraoceanic volcanic arc and the Arctic Alaska margin, which eventually led to the thrusting of the oceanic basement over the passive continental margin. The basin is flanked by the metamorphic rocks of the Seward Peninsula to the west, the Brooks Range to the north and the Ruby Terrane to the east.

Our results are from the whole stratigraphic column of the basin, from the lowermost Kv unit to the uppermost Ks unit:

• Kv unit: basaltic and andesitic lava flows interbedded with volcanogenic sediments. K-Ar ages vary from 134 Ma and 118 Ma. A single U-Pb zircon age from a tuff is about 138 Ma.
• Kvg unit: volcaniclastic greywacke with Albian molluscs are interbedded with tuffaceous layers. Two of these are dated at 112 Ma and 110 Ma (Albian).
• Kmc unit: conglomerate and greywacke with a strong mafic and calcareous imprint. Cretaceous molluscs are widespread.
• Kqc unit: quartz rich deposits with plant fossils of Cretaceous age.
• Ks+Kms units: late Cretaceous fluvial to shallow marine and deep marine sandstone and shale layers.

We use QEMSCAN® (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) for heavy mineral (HM) analysis, which, along with point counting, petrographic description, paleocurrent data and sedimentary features analysis, helps to constrain sediment provenance. Kv is the only unit reflecting a volcanic source, while the others display the progressive unroofing of the deeper and higher-grade metamorphic rocks surrounding the basin. U-Pb SIMS dating of tuffs and detrital zircons provide, for the first time, an absolute chronology for basin evolution.

The combined data indicate the YKB formed in a forearc/backarc setting prior to 138 Ma (deposition of the volcanic-rich Kv unit). With the progressive denudation of the Brooks Range, sedimentation shifted towards greater metamorphic input, leading to the deposition of the Kvg unit at 110 Ma. Ultimately, after the Late Cretaceous uplift of the Ruby Terrane, the main sediment source changed again, and the stratigraphically higher units were deposited from the Cenomanian to at least the Maastrichtian. The Savu Sea and the Taiwan margin in Southeast Asia show similarities in structure, metamorphic grade, sediment composition and tectonic setting, suggesting these are effective modern analogues that can enhance our understanding of both ancient and modern arc-continent collisional systems.

How to cite: Seminara, S., Pease, V., Toro, J., and Omma, J.: Provenance analyses: a tool to constrain tectonic changes. Parallelism between the ancient Yukon-Koyukuk Basin (Alaska) and modern Southeast Asia., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12028, https://doi.org/10.5194/egusphere-egu25-12028, 2025.

The architecture of sedimentary basins is shaped by the interplay between relative sea-level changes and sediment supply combined with sediment transport processes. Relative sea-level changes are controlled by both eustatic sea-level variations and tectonics. While the effects of these factors on stratal stacking patterns have been a focus of extensive research, their distinct contributions remain incompletely understood.

In this study, we interpreted high-resolution seismic profiles together with deep well data from the South Adriatic Foredeep (SAF), focusing on tectonic and sedimentary processes and sea-level fluctuations over the last 5.3 Ma. The SAF is an active basin, bounded by the Dinaric/Albanian thrust front and Apennine thrust/Apulian platform. Furthermore, the sedimentary system was further analysed by the means of 3D stratigraphic numerical modelling with DionisosFlow that accounts for the variability of the sediment and water flux combined with climatic and sea level variations, and sediment compaction. A series of models were conducted testing different subsidence, sediment supply and water discharge values, eustatic curves and sediment compaction parameters on the overall basin morphology.

Based on the joint interpretation of the observational and model data, we propose a new stratigraphic model for the Miocene to Recent sedimentary evolution of the South Adriatic Foredeep. The basin is characterized by the variable length of the shelf around the basin margin with deposits of the deep-water gravity flow and bottom-currents on the slopes. The progradation of the shelf in NW reached up to 55 km, on top of the Apulian platform around 50 km, while at the footwall of the Dinaric thrust belt varies from 15 km to 30 km, with different thicknesses. The rate of the progradation at some places increased three times during Pleistocene, e.g. from 5,5 to 16 m/kry. Calculated subsidence also varies around the basin affecting the lateral change in accommodation space. Finally, the sedimentary architecture on the shelf is overprinted by compaction effects, which are most pronounced over basin confinements, sometimes causing significant deformation and subsequent aggradation.

A key characteristic is the pronounced variability in sediment deposition along basin margins, driven by local tectonic and climatic forcing, as well as variation in autogenic processes. We conclude that the overall progradation was shaped by variable long-term (> 100 kyr) versus short-term (<100 kry) forcing factors. In the long run, i.e. from the beginning of the Pleistocene, repeated glaciations led to greater water fluxes and sediment supply, resulting in higher progradation rates. The tectonic influence on the rates of accommodation space do not show abrupt changes over time. Short-term factors influencing the water flow and sediment discharge in combination with the fall and rise of sea level lead to high-frequency changes in stratigraphy and are responsible for the formation of clinoforms on the basin slopes.

Beicip-Franlab is acknowledged for providing an academic license for DionisosFlow. This study was supported by the Croatian Science Foundation as part of the Outgoing Mobility Program.

How to cite: Rukavina, D. and Balázs, A.: Tectonic and climatic forcing on shelf margin slope progradation in the Adriatic Sea: inferences from seismic and well data and 3D numerical forward modelling , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12577, https://doi.org/10.5194/egusphere-egu25-12577, 2025.

Upper Cretaceous Blackhawk Formation of the Western Interior Seaway of the North America was used to develop the models for shoreface and wave dominated delta in the stratigraphic record. The hundred of meters thick continuous outcrops also served as a model for development of sequence stratigraphy and many geoscientists continue to train using delta deposits in the Book Cliffs area of Utah. However, the existing deltaic facies models do not consider the delta double-clinoform morphology, shoreline and subaqueous-delta components, that is now widely documented in modern delta systems.

River deltas prograding into a basin are reworked by waves and tidal currents and this causes the double clinoforms geometry as observed in modern delts (e.g., Mekong, Huanghe, Yangtze, Amazon, Atchafalaya). The directly river derived sediments form prograding mouth bars and reworked shorelines/interdistributary bays and these form the shoreline or subaerial delta clinoforms. The high energy around wave-dominated shorelines causes especially the large-volume finer grained portion of the sediment budget to bypass further onto the shelf, producing the subaqueous delta with a very gentle rollover from platform to subaqueous foreset in tens of meters water depth.

Fifteen published and 6 new measured sections in outcrops of Book Cliffs north of Green River, together with tens of well logs allow observation of the facies and architecture of the Kenilowrth Mbr. of the Blackhawk Fm. along depositional strike and dip. Kenilworth Mbr. has multiple parasequences tens of meters thick that coarsen and thicken up from cm thick silts to cm to dm thick parallel laminated and ripple cross-strata very fine sandstones within otherwise quite muddy successions. Thin sandstone beds have sharp to erosive bases suggesting emplacement as “event-beds” on the subaqueous-delta clinothems. Bioturbation is overall low to moderate but locally, in the mud intervals between very fine sandstones can be intense. The fine-grained coarsening-up units are capped by a few dm thick beds with ripple cross-lamination, low angle lamination and thin sets of hummocky strata. The total thickness of these deposits varies between 0.5m to 2m and are then overlain by structureless or cm thick laminated silts and very fine sandstones.  Stacking of 2 to 3 coarsening upward parasequences in a subaqueous delta unit can total 90m thick deposits. The overlying 10 to 15 m coarsening upward sandstone dominated unit with dm to m thick rippled and trough or hummocky stratified fine to medium grained sandstone is interpreted as the delta front or shoreline clinothem.

The proposed model of double-delta clinoforms triggered by observations on modern delta systems and numerical models has had a significant impact and allows us the reinterpretation of stratigraphy. A subaqueous platform that is kilometers to tens of kilometers wide allowed the transport of fine and very fine sands further into the basin. The generation of the subaqueous platform changes the conventional architecture of the delta deposits with multiple subaqueous lobes in addition to the “subaerial” delta lobes that define the shoreline. Coeval progradation of the shoreline and subaqueous delta clinoforms produces two coarsening upward successions to the compound delta.

How to cite: Olariu, C. and Steel, R.: Delta double clinoforms facies model for sequences of the Upper Cretaceous Blackhawk Formation in the Western Interior Seaway, Utah, USA, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14638, https://doi.org/10.5194/egusphere-egu25-14638, 2025.

During much of the Mesozoic, deposition on the eastern part of the Adria microplate contrasted between two major paleogeographic domains: the deep-water realm of its subsided margin flanking the Neotethys Ocean and the shallow-water carbonate platform environments of its interior. Since the late Jurassic tectonic processes related to Europe-Adria convergence progressively affected both of these regions. Ophiolite obduction and continued nappe propagation involving Adria basement caused local uplift and subsidence related to lithosphere flexure and migration of foreland basin depocenters. The area of Gacko in Bosnia and Herzegovina offers a well exposed sedimentary record of initial foreland basin encroachment onto the margin of the long standing Adriatic Carbonate Platform.
Along a transect north of the town of Gacko, Lower Cretaceous shallow marine deposits are overlain by massive bioclastic floatstone - rudstone interpreted as deposited in a ramp environment, marking an early stage of foreland basin formation. Upwards the succession changes into a well-bedded Santonian-Campanian sequence of alternating pelagic wackestones, carbonate turbidites, hyperconcentrated density flows, and slumps deposited in a slope environment. Clast composition includes various bioclasts (benthic foraminifera, rudists), intraclasts of pelagic wackestone-packstones hosting Late Cretaceous foraminifera, and extraclasts of Cretaceous limestones. A dominance of pelagic sedimentation suggests continued relative deepening during the Campanian. Further in the succession sedimentation shifts to coarse grained carbonate breccias and calcarenites possibly indicating coeval tectonic influence along the basin flank. In the Maastrichtian and Paleocene, deposits are characterized by an alternation of marls, sandstones, calcarenites, and carbonate breccias. Thick (>10 m) megabeds consist of poorly sorted, clast-supported, angular carbonate clasts (up to 40 cm in size) in their lower segments, topped by several meter thick massive calcarenite upper segments. Their clast composition includes various carbonate lithoclasts, which together with E-NE-directed paleocurrent orientations suggest a dominant derivation of material from the carbonate platform realm to the SW. The siliciclastic component in the sandstones is largely composed of quartz and foliated quartz-mica lithoclasts, while the heavy mineral fraction includes Cr-spinel, zircon, garnet, rutile, and tourmaline, indicating contribution of material from units exposed in the advancing orogenic wedge.

How to cite: Lužar-Oberiter, B., Petrinjak, K., Kukoč, D., Banak, A., Kocjančič, A., Bjelogrlić, M., Šamarija, R., Aščić, Š., Šuica, S., Olić, I., Mezga, A., and Moro, A.: Initial stages of foreland basin formation along the Adriatic carbonate platform margin of the Dinarides (Gacko, Bosnia and Herzegovina), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14856, https://doi.org/10.5194/egusphere-egu25-14856, 2025.

The Belgica Mound Drift, located in the Porcupine Seabight offshore west Ireland, is a small (~30 km²) contourite drift situated between the Irish Shelf to the east and cold-water coral mounds to the west. These contourite deposits are shaped by the dynamic interaction of the Mediterranean Outflow Water and the complex seabed topography. Despite significant advances in marine research, identifying and characterising contourites within the sedimentary record remains poorly understood. The relatively small size of the Belgica Mound Drift presents a unique opportunity to examine spatial and temporal sedimentological variability within a contourite drift. During the 2023-13 RV Belgica campaign, new sediment 3 m long cores were collected from the crest and the flanks of the drift, estimated to cover the last deglaciation. The cores were used for sedimentological and compositional analysis. The results of the medical CT scans and line-scan imaging, reveal that the cores from both locations exhibit similar sedimentary characteristics. Sedimentological analyses, including grain size, and magnetic susceptibility measurements (MS), coupled with compositional analysis via Itrax XRF scanning, suggest that the cores can be subdivided into two primary units. The top layer of unimodal fine sand has a mean grain size of 185 µm and relatively low MS values. The bottom part of the cores consists of bimodal sandy silt to silt with a mean grain size of 15 µm and relatively high MS. Additionally, the lower unit is heavily bioturbated, obscuring many primary sedimentary structures. The two distinct sedimentary layers indicate a clear change in depositional settings and the current regime of the Mediterranean Outflow Water in the Porcupine Seabight during the last deglaciation.

How to cite: Reyniers, P., Vander Cruyssen, P., Vander Haeghen, N., and Van Rooij, D.: Spatiotemporal sediment dynamics within the Belgica Mound Drift during the last deglaciation, offshore Ireland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17160, https://doi.org/10.5194/egusphere-egu25-17160, 2025.

The Tilioideae (Malvacae) contains about 50 extant species assigned to the three genera, Craigia, Mortoniodendron, and Tilia. The pollen morphology and ultrastructure of Tilioideae is characteristic and pollen of this subfamily is relatively easy to recognize during routine light microscopy (LM) investigations. Tilioideae pollen is small to medium sized, circular to convex-triangular in outline, oblate, brevi(3)colporate with thickened nexine surrounding the endopori (costae), and has reticulate ornamentation that can range from perforate to reticulate. To assign fossil Tilioideae type pollen to extant genera, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) has to be employed. Mortoniodendron pollen grains are small (20-33 µm in LM) and with a coarse reticulum in SEM with psilate or crested muri. The lumina are filled with free-standing columellae which form an internal tectum in TEM. Craigia pollen is medium sized (29-37 µm in LM) and has nano- to microreticulate ornamentation with psilate or striate muri and psilate to perforated lumina. In TEM, Craigia pollen has an indistinct internal tectum. Tilia pollen is large (30–52 µm in LM) and has a microreticulate ornamentation and lumina that are irregularly polygonal and funnel shaped. An internal tectum is rare in Tilia. The costae at the apertures in Mortoniodendron and Craigia pollen are of similar thickness and width. The costae in pollen of Mortoniodendron usually form acute angles to the interapertural wall, but the costae in Craigia pollen consistently form right to obtuse angles to the interapertural wall. Tilia has the most massive and widest costae, and in pollen of some Tilia species the sexine bulges outwards, which adds to the thickening of the aperture. The importance of accurately affiliating fossil Tilioideae pollen to extant genera (or to exclude them) lies in their climate preferences. Mortoniodendron occurs in fully humid to monsoonal tropical rainforest climate and biomes. Craigia grows in subtropical winter dry forests with warm to hot summers. Tilia thrives in temperate broadleaf to mixed deciduous and conifer forests in subtropical, warm temperate, and boreal climates, it is cold resistant but prefers abundant humidity. Using combined LM, SEM, and especially TEM, to investigate fossil Tilioideae type pollen makes it possible to correctly identify Craigia, Mortoniodendron, and Tilia pollen, and to exclude similar pollen from extinct taxa of the subfamily as well as other closely related fossil or extant Malvaceae.

How to cite: Geier, C., Bouchal, J. M., Ulrich, S., and Grímsson, F.: Identifying Tilioideae pollen in the fossil record using electron microscopy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17212, https://doi.org/10.5194/egusphere-egu25-17212, 2025.

The Fram Strait, located between Svalbard and Northeast Greenland, is the only deep oceanic passage linking the Arctic and Atlantic Oceans. Water exchange through the strait is crucial for the Atlantic Meridional Overturning Circulation, controlling global climate. Increased water exchange between the Arctic and Atlantic Oceans might have been one of the main factors driving global climate into an icehouse state at the Eocene-Oligocene Transition, around 34 million years ago. However, proxy evidence is scarce due to limited sedimentary archives from the region.

The <20 km-wide Forlandsundet Graben located on the western Svalbard margin is a pull-apart basin formed during the early Paleogene. It may represent a precursor to the Fram Strait, potentially allowing water exchange already during the Paleogene. The thickness and age of the graben fill are poorly constrained, necessitating a better stratigraphic framework to understand the events leading to the seaway’s opening and deep-water connection between the Atlantic to the Arctic Ocean.

Vintage 2D seismic data suggest the sedimentary succession in the graben may exceed 4 km. A petroleum exploration well (7811/5-1) drilled onshore at Sarstangen in 1974 reached metamorphic basement rocks at a depth of 1046 m, penetrating over 1 km of mostly marine mudstones and sandstones, initially dated as possibly Eocene and Oligocene.

To refine the stratigraphy and estimate paleo-environments and maturity of the sedimentary succession, we investigated three cored intervals of the 7811/5-1 well. Combined dinocyst and foraminifera assemblages suggest a middle Eocene age for the lowermost core interval  and an upper Eocene to early Oligocene age for the uppermost core interval. Foraminifera indicate outer neritic to upper bathyal water depths (100-500 m) in the Eocene. Pollen and spores are more common than marine dinocysts, and the uppermost core yields coal fragments. TOC, T_max, and HI suggest inert kerogen of mixed origin, classified as type III/IV.

These findings enhance our understanding of the Forlandsundet Graben's stratigraphy and its role in Arctic-Atlantic water exchange during the Paleogene, providing crucial insights into the geological history and paleo-environments of the region.

How to cite: Sliwinska, K. K., Sheldon, E., Bojesen-Koefoed, J., Grundvåg, S.-A., Jones, M., Knutsen, S.-M., Weber, M., Senger, K., and Laberg, J. S.: Deciphering the geological history of the Forlandsundet Graben and its implications for Arctic-Atlantic connectivity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17246, https://doi.org/10.5194/egusphere-egu25-17246, 2025.

Sedimentology of coastal carbonate sediments and evaporites of Abu Dhabi has been intensively studied. However, information about deeper subtidal deposits and seasonal variations of water properties is more limited. This investigation explores the sediment composition of six cores and water column properties (temperature, salinity, dissolved oxygen, pH) along a 150 km long SSE-NNW transect in offshore eastern Abu Dhabi, with water depths ranging from 11 to 45 meters. Situated in the southeastern Arabian Gulf, the transect includes diverse oceanographic and sedimentological zones, serving as a crucial benchmark for understanding seasonal variability and regional environmental dynamics.

CTD surveys conducted in August 2024 captured temperature, salinity, pH, and dissolved oxygen profiles during the warmest part of the seasonal cycle. Temperature profiles revealed stratification of the distal water body, with surface temperatures reaching 36°C and a thermocline between 10 and 28 meters. The proximal water body showed no temperature stratification and uniform temperatures from 35-36°C from the coast to 80 km offshore and down to 28m water depth. Salinity ranged from 39 PSU offshore to 45 PSU nearshore, with a uniform surface layer and increasing stratification with depth. Dissolved oxygen peaked at 5 ml/l in surface waters, declining to 2 ml/l at the bottom, indicating significant stratification but no hypoxia in the deep-water body. Surface pH values were high (above 8.45), decreasing gradually to 8.2 in bottom waters.

The grain size distribution of the cores reveals a correlation between core penetration depth and sediment characteristics. Coarse-grained sediments yielded shorter cores (10–20 cm), while muddy sediments at the deepest site produced a 50 cm core. Grain size analysis identified a progression of mean grain size from fine and medium sand in shallower cores to coarse sand further offshore and muddy sediments at greater depths (> 40m), illustrating dynamic sedimentary processes

The sediment composition predominantly includes small bivalves, gastropods, benthic foraminifera, echinoid spines, ostracods, and occasional planktonic components such as pteropods. The high abundance of micromollusks (bivalves and gastropods < 2mm) compared to similar carbonate depositional settings highlights their potential role in carbonate production.

Further analyses include the quantification of sediment compositions across grain-size fractions and stable isotope analyses of bioclasts to determine seasonal carbonate production patterns. Analyses of seawater and sediments provide insights into nutrient dynamics, seawater acidification and oxygenation, enhancing the understanding of the response of already extreme marine environment of the Arabian Gulf to climate change.

How to cite: Rojas-Lequerica, S., Aljaberi, A., Alshehhi, A., Abdelmaksoud, A., Aldhanhani , O., Al Suwaidi, A., Sreenivasan, S., Environmental Agency Abu Dhabi, J., and Steuber, T.: Spatial Variability in Sediment Composition and Seawater Properties along a transect in Eastern Offshore Abu Dhabi, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17749, https://doi.org/10.5194/egusphere-egu25-17749, 2025.

The Konzentrat-Lagerstätteof ‘Lo Hueco’ in Central Spain represents an extremely rich and diverse upper Campanian-lower Maastrichtian fossil assemblage comprising more than 10,000 fossil remains: This has made it, in recent years, one of the most relevant European fossil sites for the study of continental vertebrate faunas. The stratigraphic succession in ‘Lo Hueco’ is primarily characterized by six levels separated by transitional boundaries of green (V), grey (G1), red (R1), grey (G2), red (R2) and brown (M) beds of marly mudstones. The sample of microvertebrates remains analysed here was obtained from the screenwashing and sorting of the sediments from the G2 bed, as it corresponds to one of the richest lithosomes in terms of abundance and diversity of vertebrate microfossils from the site. Among these fossil materials, the most prevailing are the fish, especially the conical teeth and ganoid scales from Lepisosteidae. Other fish remain, though less abundant, include lanceolate teeth attributed to Amiidae and two types of molariform teeth. The first type consists of oval and flattened teeth from Pycnodontidae, while the second type correspond to circular dome-shaped teeth similar to those of Paralbulinae. The Lissamphibia material is represented by appendicular elements such as humeri, radioulnae and tibiofibulae assigned to Anura. However, one humerus probably belongs to discoglosids due to some similarities. One small fragment with a pleurodont tooth is attributed to a scincomorph lizard. Crocodiles remain correspond to at least six tooth morphotypes that can be assigned to Allodaposuchidae teeth and Atoposauridae-like teeth. Allodaposuchids are represented by cf. “Agaresuchus” sp. and others. The atoposauridae teeth are considered as to cf. “Theriosuchus” sp. Theropod tooth specimens, despite being among the least abundant fossil remains, constitute an important part of the diversity reported here, pointing out the presence of cf. Dromeosaurinae, cf. Velociraptorinae, cf. Troodontidae and cf. Richardoestesia sp. This vertebrate assemblage is consistent with upper Campanian-lower Maastrichtian coastal shallow flooded muddy plains, which also provides a unique set of fauna that distinguishes it from other Iberian Peninsula localities.

How to cite: Cabrera Hernández, J. S., Ortega, F., and Torices, A.: Microvertebrate assemblage from the Upper Cretaceous site of Lo Hueco (Cuenca, Spain): A preliminary approach., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19127, https://doi.org/10.5194/egusphere-egu25-19127, 2025.

One of the important hydrocarbon reservoir targets in the Midyan Basin, Northwest of Saudi Arabia along the Red Sea is the deep-sea sandstone turbidites of the Miocene Burqan Formation. This study leverages well-exposed outcrops to comprehensively assess the reservoir characteristics of this formation. A multi-faceted approach integrating field observations (sedimentology, stratigraphy, structural geology) with detailed measurements and advanced techniques (photomosaics, LiDAR) was employed to characterize reservoir heterogeneity, quality, and architecture. Fieldwork encompassed vertical and lateral outcrop profiling across a 25 km transect, capturing the spatial distribution and geometry of sandstone bodies. LiDAR facilitated high-resolution documentation of sedimentological, stratigraphic, and structural features, including strata geometry, fault networks, and fracture distributions. Laboratory analyses complemented field observations, examining lithofacies textures, composition, and petrophysical properties. Results demonstrate significant lateral and vertical variability in reservoir characteristics. Sandstone body thicknesses decrease from proximal (1.5-5 m) to distal zones (0.4-1 m), accompanied by an increasing shale-to-sandstone ratio. Sandstone bodies exhibit lateral extents ranging from 80 to over 130 meters. Lithofacies include conglomerates, pebbly sandstones, and coarse- to medium-grained sandstones, interbedded with finer-grained units. Proximal regions display well-developed stacked sand bodies, while distal areas exhibit greater shale and mudstone interbedding, potentially forming baffles. The tectonically active setting, characterized by rifting and faulting, has significantly impacted reservoir architecture, influencing seal relationships, continuity, and the distribution of internal barriers. This outcrop-based study provides a valuable framework for understanding the impact of geological heterogeneities on reservoir quality and architecture within the Burqan Formation. The findings have critical implications for exploration and development activities in the geologically complex Red Sea region and analogous hydrocarbon provinces.

How to cite: Osman, M. and Abdullatif, O.: Characterization of the Miocene Turbidite Sandstone Reservoirs in the Burqan Formation, Red Sea Region: Insights from Outcrop and Structural Analyses, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19835, https://doi.org/10.5194/egusphere-egu25-19835, 2025.

Prograding clinoforms of different scales usually occur in special carbonate sedimentary systems. Since carbonates are mainly generated in situ by biochemical processes within the basin, prograding clinoform sediments are less common than terrigenous clastic sedimentary systems. Carbonate prograding clinoforms have not received much attention in research, resulting in a lack of investigation into their sedimentary process, genetic mechanism and controlling factors. The investigation utilized integrated analysis of cores, thin sections, 3-D seismic and well logging data to explain the sedimentary process, genetic mechanism, controlling factors of carbonate clinoforms and its relationship with the development of favorable reservoirs. The result shows that there are five vertically overlapped clinoforms advancing from WWS to NNE. which occurs as S-shaped lens, with thick middle parts and thin ends. Well logging and seismic characteristics have provided the basis for establishing a sequence-stratigraphic framework. Two regionally third-order sequences (Sq1-Sq2) are developed in the Stage-3 succession, Sq1 incorporates three clinoforms (C1-C3); Sq2 incorporates two clinoforms (C4-C5). In the Sq1, the vertically aggradational thickness of the clinoforms were large, about 70~160 m, and the study area was dominated by the outer middle-ramp deposits. In the Sq2, the vertically aggradational thickness of the clinoforms were small, about 3~40 m, and shallow shoal deposits were developed in the edge of the clinoforms. The clinoforms can be further divided into 21 2^rd-clinoforms. Four main types of clinoform architecture were recognized: falling (progradational pattern), flat (progradational pattern), rising (progradational and aggradational pattern) and backstepping (retrogradational pattern) edge trajectories. The present study revealed that the formation of clinoforms were controlled by the change of eustasy. Due to the broad ramp sedimentary background and sea-level fall, the sedimentary accommodation space continued to decrease, which ultimately lead to the formation of the prograding clinoforms. Reservoirs dominated by high-energy shoal are developed at the edge of the clinoforms.

How to cite: He, Q., Shi, K., Liu, B., Wu, C., Adam, M., and Mountney, N.: Stratigraphic evolution of Stage-3 clinoforms from northern Tarim Basin: Evaluating controlling factors on a distal steepening carbonate ramp growth and shallow-water sedimentation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20201, https://doi.org/10.5194/egusphere-egu25-20201, 2025.

Mixed siliciclastic-carbonate deposits accumulated in the passive continental margin of the Arabian plate are commonly found in the Mesozoic stratigraphic interval in southeastern Iraq. As important hydrocarbon reservoirs in the area, the Cretaceous strata have attracted great interests of researchers to study their sedimentary features, depositional processes and petrophysical properties. However, in-depth studies considering the systematic evolution of a mixed siliciclastic-carbonate succession in the context of sequence stratigraphy and its control on the petrophysical properties of the rocks are still rare. In this study, two representative formations (i.e., the Nahr Umr and the Mishrif formations) that constitute a seismic-scale strata mixing (sensu Chiarella et al., 2017) were fully investigated. An integrated dataset, including core and thin section descriptions, well logs, and results from core experiments (e.g., XRD analysis, grain size distribution, porosity, and permeability measurements), was employed to perform a detailed analysis of sedimentary facies, interpret depositional environments, and evaluate petrophysical properties. The Nahr Umr Formation is dominated by siliciclastic sediments with sedimentary facies interpreted as distributary channel, tidal channel, tidal flat, tide-modified mouth bar, bay, lower shoreface, offshore transition and offshore. The assemblage of sedimentary structures observed in this formation, including cross-bedding, ripple cross-lamination, lenticular bedding, and wavy bedding, indicates a tide-influenced deltaic environment. This interpretation is further supported by the bimodal grain size distribution revealed through analysis, reflecting the combined influences of fluvial and tidal processes. The Mishrif Formation is dominated by carbonate sediments deposited in a carbonate platform environment, with sedimentary facies interpreted as high-energy shoal, low-energy shoal, tidal channel, lagoon, subtidal, swamp and incised valley. Local depositional environments transitioned among open platform, semi-restricted platform, and platform margin settings in response to relative sea-level fluctuations. The petrophysical properties of the studied formations are influenced by both sedimentary and diagenetic processes. High-quality reservoirs are typically associated with sedimentary facies such as distributary channels, tidal channels, and bioclastic shoals. Diagenetic dissolution has played an important role in enhancing reservoir quality.

How to cite: Gao, M., Chiarella, D., Han, H., Ning, C., and Lyu, Z.: Reservoir characterization of a mixed siliciclastic-carbonate succession, Middle Cretaceous, southeastern Iraq, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20438, https://doi.org/10.5194/egusphere-egu25-20438, 2025.

The Herbert Schaffer fossil collection, acquired in 2024 by the Upper Austrian State Cultural Organization (OÖ Landes-Kultur GmbH), represents the most significant private paleontological collection in Austria. By early 2025, the staggering amount of approximately 60 tons of fossil material had been recovered from Würting Castle in Upper Austria. This remarkable collection is unique not only for its size and unusual history but also because nearly all objects remain scientifically unstudied and undescribed. The collection’s breadth and quality offer unparalleled opportunities for paleontological research, making it a treasure of national importance for understanding the geological and biological history of Austria.

Among the most noteworthy objects are the fossils from the site of Traun-Pucking, comprising remains of multiple odontocete individuals. More than 5,000 boxes containing primarily Syngnathidae, Labridae, and other Percomorphaceae from the site of St. Margarethen, Burgenland, were retrieved from the upper floors of Würting Castle in Offenhausen. Also stored in the halls of the castle’s second floor was an unprepared Jurassic crocodile from the clays near Peterborough, UK, as well as a ca. 3.5-meter-long Ichthyosaurus from the world-famous Lagerstätte of Holzmaden, Germany. Furthermore, the Schaffer collection includes fossils from the following localities in vast quantities: Eggenburg, Lower Austria; Nefgraben near Rußbach, Upper Austria; Bad Adelholzen, Germany; Schlaifhausen, Germany; and Weistal near Hallein, Salzburg. A complete list of all fossil sites recorded can be provided by the authors.

Efforts to preserve, catalog, and digitize the collection are currently underway, ensuring its accessibility for scientific study and public engagement. This initiative not only honors Herbert Schaffer’s legacy but also seeks to establish a foundation for interdisciplinary research in paleontology and paleoecology at the Biodiversity Research Center Linz of the OÖLKG. By presenting an overview of the collection and its immense scientific potential, this contribution seeks to highlight its value, raise awareness within the scientific community, and attract researchers to contribute to the study and comprehensive analysis of this extraordinary paleontological treasure.

How to cite: Wöger, J., zucali, K., and reiter, E.:  The Exceptional Fossil Collection of Herbert Schaffer from Würting Castle: Conservation, Digitalization, and Identification of Fossil from Europe and Northern Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21901, https://doi.org/10.5194/egusphere-egu25-21901, 2025.

The Latest Devonian Hangenberg Event (ca.359 Ma) was one of the largest crises of the biosphere. It was directly responsible for the extinction of about 50 % of marine genera mainly from the pelagic realm such as ammonoids, conodonts and placoderm fish. This extinction is linked to worldwide anoxia caused by global climate changes, but its direct cause remains unidentified and still a topic of many scientific studies. Recently discovered mercury spikes, detected at the the D/C boundary in many parts of the world, present convincing evidence of increased volcanic and hydrothermal activity. Newly, tellurium, along Hg anomalies, has been successfully used to confirm Siberian volcanism at the end of the Permian. Today, the global volcanic tellurium flux often shows greater enrichment in Te compared to other volatile elements like mercury, thallium, or bismuth. Therefore tellurium may prove to be a much more promising indicator of volcanism. There is a lot of data on the Hg chemostratigraphy at the crucial intervals during Phanerozoic. In contrast, our knowledge of tellurium cycles during critical intervals of mass extinctions, LIPs emplacements and biotic crises, is entirely lacking. To investigate this issue, we have examined a succession of deep-water, pelagic sedimentary rocks, encompassing the Devonian–Carboniferous boundary interval in the Novchomok section (southern Uzbekistan) using tellurium chemostratigraphy. Previous studies of this section at the Devonian-Carboniferous boundary, had detected the Hg and Hg/TOC anomalies in marly shales, marls, and carbonates, occurring independently of the facies changes, which imply a volcanic origins of those anomalies. Additionally, the presence of negative δ13Corg excursions reflects a massive release of isotopically light carbon from volcanogenic and thermogenic devolatilization. Our preliminary results of Te contents and Te/Th ratios at the Devonian–Carboniferous boundary in the Tian-Shan are promising. Here we report for the first time large anomalous Te spikes (with maximum values reaching 930 ppb) and an increase in Te/Th ratios, which closely correspond with Hg spikes and a negative shift in ẟ13Corg, and indicate that Te could be promising volcanic activity proxy in deep time intervals.

How to cite: Książak, D. and Rakociński, M.: Tellurium anomalies as signs of intensive volcanic activity around the Devonian-Carboniferous boundary in The South Tian-Shan (southern Uzbekistan), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-236, https://doi.org/10.5194/egusphere-egu25-236, 2025.

The end-Permian event (EPE, c. 252.3–251.9 Ma) resulted in the catastrophic collapse of continental ecosystems, including the extinction of peat-forming Glossopteridales in southern Gondwana. The Sydney Basin, positioned at high southern latitudes (c. 70°S), preserves a detailed Early Triassic continental succession, offering unique insights into past ecosystem destabilisation and recovery dynamics in the wake of the EPE. Here, we present a high-resolution, age-controlled analysis of floral and environmental trends in the region, integrating palynology, geochemistry, and sedimentology.

Palynological data, aided by non-metric multidimensional analysis, revealed distinct floral shifts linked to key climatic events, including the late Smithian thermal maximum (LSTM, c. 250.3–249.6 Ma) and the Smithian-Spathian cooling event (SSE, c. 249.6–249.2 Ma). Carbon isotopic compositions of bulk organic matter (δ¹³C_org) were used to correlate these shifts with global carbon cycle perturbations. Visible and infrared spectroscopy (HyLogger), combined with sedimentological analysis, determined sediment composition and provenance, while X-ray fluorescence (XRF) provided weathering proxies such as the chemical index of alteration.

The palynological record reveals the ebb and flow of several distinct floristic communities during the first five million years following the EPE. Initial post-collapse ecosystems were dominated by peltasperm seed ferns for c. 200,000 years. This ecosystem was supplanted by voltzialean conifers, which thrived for c. 1.5 million years until their decline during the hyperthermal LSTM. The LSTM interval is demarcated in the Sydney Basin as occurring near the end of a major global negative δ¹³C_org excursion c. 250.2 Ma. Weathering indices and sedimentology of this interval evidenced drier conditions were at play, likely connected with the co-occurrent global rise in temperature. Furthermore, stress-tolerant isoëtalean lycophytes, such as Pleuromeia, became dominant, reflected by a prolonged acme of associated spores (e.g., Densoisporites nejburgii). Intriguingly, while pleuromeians proliferated at low latitudes soon after the EPE, their dominance in the Sydney Basin is recorded only during the LSTM c. 1.7 million years later, perhaps signalling another phase of gymnosperm ecosystem decline and a delayed upsurge of stress-tolerant floras at south polar latitudes.

The SSE, recognised by a major global positive δ¹³C_org excursion c. 249.4 Ma, saw the expansion of umkomasialean seed ferns dominated by the iconic Triassic Gondwanan plant Dicroidium. However, the landscape also saw the intermittent emergence of other pleuromeian spores (i.e., Aratrisporites), in addition to fluctuating floristic diversity following the SSE for c. 1.5 million years. Sedimentological data from this interval show widespread Fe-rich mudrocks ("red beds"), likely reflecting better-drained floodplains. HyLogger and XRF data suggest humid, seasonal environments punctuated by drought periods. Although gymnosperm pollen gradually became the most abundant plant microfossil—denoting the long-term reestablishment of gymnospermous forests—the Sydney Basin apparently still lacked the necessary environmental conditions required for coal formation until well into the Middle Triassic.

These findings reveal a staggered, non-linear recovery of high-latitude ecosystems, with alternating dominance of gymnosperm and lycophyte floras persisting until the Early–Middle Triassic boundary (c. 247.2 Ma).

How to cite: Amores, M., Frank, T., Fielding, C., Hren, M., and Mays, C.: The late Smithian thermal maximum and the Smithian-Spathian event were the two primary drivers of Early Triassic floristic changes at high southern latitudes  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-488, https://doi.org/10.5194/egusphere-egu25-488, 2025.

The highest trophic niches in Mesozoic oceans were occupied by multiple, loosely related clades of marine reptiles, which evolved a series of craniodental and postcranial morphologies. The Jurassic and Early Cretaceous are characterized by relative stability of higher taxonomic levels, with three main clades dominated trophic chains: ichthyosaurians, plesiosaurians, and thalattosuchian crocodyliformes. This macroevolutionary picture changes drastically during the ‘middle’ Cretaceous: ichthyosaurians, thalattosuchians, and pliosaurid plesiosaurians disappear, whereas mosasaurids and peculiar xenopsarian plesiosaurians diversify, alongside acanthomorph teleosts, neoselachian sharks, marine turtles, and marine birds. This shift created the unique and somewhat short-lived oceanic trophic webs of the Late Cretaceous. Many of these clade turnovers (although not all) are concentrated during the Cenomanian-Turonian interval, a time known for its climatic volatility.

Project SEASCAPE explores the long-term impact of environmental changes on extinct oceanic top predators. To do so, we combine two main datasets and approaches. Firstly, we carry out phylogeny-informed analyses of extinction selectivity, using a new informal supertree sampling 370 marine reptile lineages. Secondly, we compute macroevolutionary functional landscapes before and after the event(s), based on (to our knowledge) the largest sample of 2D and 3D data on marine reptiles ever assembled. We found that lineages’ extinctions are both elevated and selective during the ‘middle Cretaceous’, targeting different clades at each boundary. Our macroevolutionary functional landscapes show that the weak morphological and functional convergence between Early and Late Cretaceous marine reptiles resulted in assemblages that are clearly dissimilar not only in terms of phenotypes, but also exhibiting biomechanical and functional divergences. This highlights the importance of past extinction events in reshaping the highest tiers of marine trophic webs.

How to cite: Fischer, V., Della Giustina, F., Bennion, R., and MacLaren, J.: How mid-Cretaceous events affected marine top predators, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3100, https://doi.org/10.5194/egusphere-egu25-3100, 2025.

The Early Triassic is a key interval to understand biotic and environmental recovery after the major disturbance of the planetary system at the Permo-Triassic Boundary (PTB). The collapse of biodiversity and the dramatic change of the global carbon cycle are thought to be the result of intrusions of mafic melts of the Siberian Large Igneous Province (S-LIP) into sediments rich in organic matter and evaporites. However, the Early Triassic is marked by a long record of global carbon cycle perturbations, suggesting that severe climatic instability and delayed biotic recovery may go beyond S-LIP volcanism.

To further explore this question, we compiled and constructed a continuous stratigraphic record in the platform-slope sequences of the Nanpanjiang Basin, South China, where bio- and chemostratigraphic control is supported by precise geochronology. We present here a U-Pb zircon-based Bayesian age model integrated with δ¹³C isotope data, providing precise temporal calibration of the carbon cycle fluctuations and of lithostratigraphic and biostratigraphic boundaries over 5.5 million years. This record is calibrated to absolute age via the Bayesian age model relying on 20 published and 6 new high-precision ID-TIMS U-Pb ages of volcanic zircon in interbedded ashes.

Our compilation covers six major δ¹³C excursions, three negative (termed N1 to N3) and three positive ones (termed P1 to P3): The initial sharp negative excursion N1 at the PTB (~252.02 Ma) reflects rapid input of volcanogenic CO₂ from the Siberian Large Igneous Province (S-LIP) activity. An early Griesbachian positive peak P1 (~251.88 Ma) is associated with transient recovery of organic carbon burial in microbial-rich environments. A negative δ¹³C shift (N2) in the Dienerian (~251.40 Ma) coincides with ecological stress and enhanced weathering. A sharp positive excursion P2 at the Dienerian-Smithian transition (~250.39 Ma) reflects carbon sequestration in a dynamic climate regime. The largest negative excursion N3 is found during the middle Smithian thermal maximum (~249.56 Ma) and correlates with the climax of global warming and marine anoxia. The Smithian-Spathian boundary positive excursion P3 (~249.33 Ma) marks a cooling phase and coincides with significant biotic turnover, particularly affecting nektonic faunas. The Spathian interval features a stepwise decrease in δ¹³C (N4; ~248.14 Ma), followed by a broad positive excursion near the Spathian-Anisian boundary (P4; ~246.88 Ma), reflecting stabilization of carbon cycling as ecosystems began recovering. The positive excursions P1 to P4 coincide with 100ky-long gaps in the sedimentary record, related to low sea-level and possibly to presence of continental ice.

Published and new U-Pb zircon and baddeleyite dates put the minimum estimate for intrusive as well as extrusive S-LIP activity into the Dienerian (ca. 251.0-250.0 Ma), pointing to a non-volcanic trigger of the P2, P3, P4, N3, N4 isotope excursions. In summary, the robust U-Pb calibrated early Triassic carbon isotope record is interpreted to reflect the interplay of volcanic influence, intrinsic carbon cycle feedback, and other extrinsic factors, which appear to have paced the alternation between extreme warming and transient cooling phases during the Early Triassic post-extinction recovery, and post-recovery period.

How to cite: Schaltegger, U., Leu, M., Paul, A. N., Widmann, P., Vennemann, T., and Bucher, H.: A high-resolution age model for Early Triassic Carbon isotope fluctuations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3121, https://doi.org/10.5194/egusphere-egu25-3121, 2025.

The Mesozoic was punctuated by several Oceanic Anoxic Events (OAE) characterised by widespread black shale deposition and global carbon cycle perturbations. Among them, the OAE2 spanning the Cenomanian-Turonian boundary (~ 94 Ma), has been identified as one of the most severe OAE of the Mesozoic. The OAE2 is characterised by a global > 2‰ positive carbon isotope excursion (CIE) recorded in both inorganic and organic sedimentary material. This CIE is interpreted as a massive burial of ¹³C-depeleted organic carbon driven by a global decrease in seafloor oxygenation. Previous models suggested that volcanism related to Large Igneous Provinces (LIPs) increased atmospheric CO₂ concentrations, thereby increasing, through enhanced continental weathering, oceanic nutrient and primary production in superficial waters, ultimately leading to higher oxygen consumption at depth. However, the role of enhanced weathering and accelerated continental fluxes on marine primary productivity and organic carbon burial during OAE2 remains highly debated, largely due to the difficulty of reconstructing highly resolved changes in terrigenous and organic fluxes from sedimentary records. In this study, we use new extra-terrestrial ³He (³He_ET) measurements from hemipelagic marine samples from Pont d’Issole (Vocontian Basin) and Cuba (Western Interior Basin) sections to reconstruct carbonate, organic carbon and terrigenous sedimentation rates and fluxes across the OAE2.

Our results from Pont d’Issole reveal that over 70 % of the ³He in the analysed samples is extra-terrestrial in origin. Assuming a constant flux of ³He_ET-bearing Interplanetary Dust Particles, we used ³He_ET concentrationsto reconstruct relative changes in sedimentation rates at an unprecedented high resolution (every 15 cm/ 5 ka). Our preliminary results indicate constant terrigenous fluxes (ca 1.6 g/cm²/ka) across different carbonate-rich and carbonate-poor lithologies prior to and across the OAE2 onset. On the contrary, carbonate fluxes plummet (from 26 to 1 g/cm²/ka) prior the CIE. This decrease occurs exactly at the level recording a marked shift towards more radiogenic osmium isotope values, pointing to a possible volcanically triggered collapse of carbonate productivity. Sediments from the Plenus Cold Event (colder and more oxygenated period within the OAE) interval and Cenomanian-Turonian boundary show more modest but significant changes in both terrigenous and carbonate fluxes (from 0.4 to 3 g/cm²/ka and from 0.8 to 11 g/cm²/ka, respectively). Our data also show that organic matter accumulation occurred mostly as short orbitally paced pulses across the entire OAE2 interval with varying responses to changes in terrigenous fluxes. Ongoing ³He_ET analyses from Cuba will provide comparative data from a different setting that will be pivotal to determine whether the reconstructed fluxes have a local or geographically widespread significance. The implication of ³He_ET data from both locations will be discussed in the context of the debated role of increased detrital input on marine primary productivity and organic carbon burial during the OAE2.

How to cite: Godet, B., Blard, P.-H., Suan, G., Suchéras-Marx, B., Riquier, L., Tibari, B., and Martinez, M.: Using extra-terrestrial 3He to reconstruct terrigenous fluxes and their impacts on marine primary productivity and carbon burial during OAE2, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3672, https://doi.org/10.5194/egusphere-egu25-3672, 2025.

The Cretaceous-Paleogene boundary (K-Pg boundary) at 66 million years ago marks one of the most severe mass extinctions through Phanerozoic. A clear peak in abundances of platinum group elements (PGEs) such as iridium (Ir) and osmium (Os) has been observed in clay beds at the K-Pg boundary around the world and is one of the most important pieces of evidence of a massive meteorite impact that could have triggered the mass extinction. A sharp decline in osmium isotope ratio (¹⁸⁷Os/¹⁸⁸Os) can also be used to detect an extraterrestrial impact. Even though the northwest Pacific is considered to have suffered almost no direct tsunami-like damage, a complete K-Pg boundary has not yet been discovered. Therefore, the discovery of the K-Pg boundary in this region is essential for understanding the environmental changes and ecosystems of the time in distal sites from the impact site, the Yucatan Peninsula in the Gulf of Mexico.

We conducted detailed field surveys and sampling in the Shiranuka Hills, Hokkaido, Japan. Our primary study area was a tributary of the Kawaruppu River, where analysis of magnetostratigraphy, biostratigraphy (foraminifera and calcareous nannofossils), zircon U-Pb dating have identified sedimentary layers from the Upper Cretaceous to the lowermost Paleogene (Takashima et al., 2024). In this study, we measured PGE concentrations and ¹⁸⁷Os/¹⁸⁸Os ratios to constrain the stratigraphic position of the K-Pg boundary. The ¹⁸⁷Os/¹⁸⁸Os ratio in the stratigraphic interval of the Upper Cretaceous was approximately 0.6, while that in the interval of the lower Paleogene was approximately 0.4. These values are consistent with those of seawater recorded in pelagic sedimentary rocks (Ravizza and Peucker-Ehrenbrink, 2003; Robinson et al., 2009). Notably, a distinct decrease in the ¹⁸⁷Os/¹⁸⁸Os ratio was observed in the stratigraphic level between the two intervals, reaching approximately 0.235. High Os concentration has also been confirmed at the same level. These results allow us to identify the K-Pg boundary at that level.

This section was deposited in a tectonically active continental margin, resulting in extremely high sedimentation rates. Our magnetostratigraphic and Os isotope stratigraphic data revealed that the sedimentation rate in this section was at least 40 cm/kyr during the Upper Cretaceous and 24 cm/kyr during the lowermost Paleogene. Consequently, it is expected to provide the highest-resolution record in the world of both terrestrial and marine paleoenvironmental changes across the K-Pg boundary.

[References]
Ravizza, G., & Peucker-Ehrenbrink, B., 2003, Chemostratigraphic evidence of Deccan volcanism from the marine osmium isotope record: Science, 302(5649), p. 1392-1395.
Robinson, N., Ravizza, G., Coccioni, R., Peucker-Ehrenbrink, B., and Norris, R., 2009, A high-resolution marine ¹⁸⁷Os/¹⁸⁸Os record for the late Maastrichtian: Distinguishing the chemical fingerprints of Deccan volcanism and the KP impact event: Earth and Planetary Science Letters, v. 281, p. 159-168.
Takashima, R., Ota, H., Kuroda, J., Schmitz, M., Hayashi, K., et al., 2024, Integrated stratigraphy and radiometric ages across the K-Pg boundary in Shiranuka Hill, Hokkaido, Japan: Abstract T16-O-12 presented at 131st Annual Meeting of the Geological Society of Japan, Yamagata University, 8-10 September.

How to cite: Ota, H., Kuroda, J., Hayashi, K., Hoshi, H., Sawada, K., Nishi, H., Ishikawa, A., and Takashima, R.: Discovery of evidence of the Chicxulub impact in East Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5002, https://doi.org/10.5194/egusphere-egu25-5002, 2025.

The Late Triassic “megamonsoon” circulation was profoundly perturbed by large igneous province (LIP) volcanism during the so-called Carnian Pluvial Episode (CPE). C-isotope excursions in sedimentary records indicate large CO₂ emissions into the exogenic reservoirs of the C-cycle during the CPE. The consequent global warming would have strongly intensified the “megamonsoon”, enhancing the hydrological cycle and perturbing global environment for a relatively long time (1.2–2.5 Myr). However, the pattern of the climate change during the rapid (maximum 110 Kyr) initial Negative C-isotope excursion (NCIE1) of the CPE remains poorly understood. Here, we performed high-resolution C-isotope analyses, major (XRF) and trace (ICP-MS) element analyses, clay mineralogy (XRD) and palynology across CIE-1 in a marine succession from the Dolomites (Italy). We show that in the northwestern Tethys the transition to more persistent wet conditions was interrupted by episodic intervals with “megadroughts” linked to discrete rapid emissions of CO₂ in the atmosphere–ocean system. These rapid (<50 Kyr) climate swings severely stressed the floral communities and triggered major changes in silicate chemical weathering, resulted in changes in nutrient delivery and redox conditions in the basin.

How to cite: Alverà, G., Dal Corso, J., Chu, D., Cruciani, G., Roghi, G., Caggiati, M., Song, H., Song, H., Tian, L., Du, Y., Haserbek, T., and Gianolla, P.: Strong climate seasonality at the onset of the Carnian Pluvial Episode in Northwestern Tethys (Late Triassic), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6018, https://doi.org/10.5194/egusphere-egu25-6018, 2025.

The Cretaceous-Paleogene (K/Pg) boundary marks a pivotal moment in Earth's history, defined by one of the five major mass extinction events and significant disruptions in global biogeochemical cycles, including shifts in carbon cycling and ocean chemistry. The Um Sohryngkew River section in Meghalaya, India, represents the most complete K/Pg sequence in the region and is comparable to global shallow marine sites. Its proximity to the Deccan volcanic province makes it a critical location for investigating the environmental stressors associated with Large Igneous Province (LIP) volcanism and their role in mass extinction and biotic recovery.

Late Maastrichtian planktic foraminiferal assemblages at Meghalaya reveal persistent stress, with species richness ranging from 6 to 13 taxa and consistently low absolute abundances (~14 individuals/g). A significant increase in abundance is observed 2.5 meters below the K/Pg boundary, from ~14/g to ~250/g. However, this interval is characterized by a population dominated by opportunistic taxa, particularly Guembelitria spp., which account for over 90% of individuals. While similar patterns are reported at coeval sites like Egypt, the prolonged dominance of Guembelitria spp. at Um Sohryngkew highlights the intense and sustained environmental stress, likely exacerbated by its proximity to the Deccan volcanic province. Assemblages are further characterized by small test sizes (<120 µm), with genera such as Planoheterohelix (8-12k µm²) and Rugoglobigerina (10-20k µm²) being 2–4 times smaller than counterparts at sites like Bidart. Test sizes of Guembelitria, Planoheterohelix, and Rugoglobigerina show further reductions of 10.6%, 10.2%, and 29.2%, respectively, around 60 cm below the K/Pg boundary. This decline aligns with increased test fragmentation, leaching, and elevated mercury levels, strongly indicating intensified volcanic activity and associated calcification stress. The absolute abundance of planktic foraminifera collapses at the K/Pg boundary, marked by a one cm-thick red clay layer enriched in Platinum Group Elements and a pronounced negative carbon isotope excursion. A brief recovery episode occurs ~2.75 meters above the boundary, with a significant increase in species richness and a rise in absolute abundance from ~2 to ~70 individuals/g. However, recovery can be tracked at 13 meters above the boundary, based on greater species richness, higher abundance (~2500 individuals/g), improved test preservation, and larger foraminiferal test sizes. Future studies, including detailed biostratigraphy, chemostratigraphy, and age modeling, will be crucial in refining the timing of extinction triggers, environmental changes, and the pace of recovery.

How to cite: Patra, S., Srivastava, P., Punekar, J., Rawat, S., Martini, A. P. D., Catanzariti, R., Bhadran, A., Girishbai, D., Iangrai, B., and Jovane, L.: Um Sohryngkew River Section, Meghalaya: Re-evaluating stress and recovery in the Cretaceous-Paleogene interval, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10220, https://doi.org/10.5194/egusphere-egu25-10220, 2025.

The Chicxulub impact in Mexico and Deccan volcanism in India are both associated with the end-Cretaceous mass extinction, but the precise timing of the impact, volcanic eruptions, and environmental changes remains debated, hindering a comprehensive understanding of their respective roles. Geochronological data from Malwa Plateau basalts, located on the northern margin of the Deccan Large Igneous Province (LIP), show that the first pulse of Deccan volcanism coincided with a ∼200 kyr warming event in the Late Maastrichtian, recorded globally in contemporaneous stratigraphic sections. This warming, estimated at 2.5–8°C, has been inferred from δ18O studies on benthic foraminifera, pedogenic carbonate, bivalve shells, and leaf morphology. The timing of this excursion corresponds to the early decline in oceanic 187Os/188Os ratios and rising mercury (Hg) concentrations. The first phase of Deccan volcanism erupted through organic-rich Permian sediments in the Narmada-Tapti rift basin. Direct CO2 emissions from basalt are unlikely to account for the scale of warming observed, unless the eruption rates were extremely high, which conflicts with evidence suggesting lower eruption rates and a longer eruption duration. It is likely that thermal contact metamorphism of the sedimentary rocks was a significant source of CO2 that contributed to the Late Maastrichtian warming event. This study aims to investigate the fate of carbon (C), mercury (Hg), tellurium (Te), and sulfur (S) during the contact metamorphism associated with the first pulse of Deccan volcanism and to assess the role of this process in the global cycles of C, Hg, and S.Our data were derived from measurements of contact aureoles around dikes and sills intruding into organic-rich Permian coal deposits in the Narmada-Tapti rift basin. We focused on total organic carbon (TOC), Hg, Te, and S concentrations. While sediments farther from the intrusions show high TOC (>20%) and notable levels of Hg, Te, and S, samples from the aureoles (5-10 m thick) exhibit a near-total loss of these elements. Vitrinite reflectance values >5% indicate temperatures above 300°C in the aureoles. We present strong evidence for thermal alteration of coals and shales due to dike-sediment interactions, leading to the production of CH4 and CO2 gases. Furthermore, all analyzed sections show significant depletion of TOC, with a distinct zone of negligible Hg levels near the contact areas. Scaling these findings with data from Mittal et al. (2021) and Kubo Hutchison et al. (2023), assuming 50% TOC loss in the contact aureoles, a median dike width of 10 m, a median dike length of 1000 m, and a coal density of 1500 kg/m³, we estimate that approximately 900 Gt of carbon may have been emitted—comparable to the total extrusive outgassing from the Deccan Traps. Our preliminary results suggest that large igneous province (LIP)-scale sill and dike emplacement in organic-rich sedimentary rocks can significantly perturb global C, S, Te, and Hg cycles. Deccan volcanism likely contributed to climate instability during the Late Cretaceous and may have amplified the environmental impacts of the Chicxulub impact.

How to cite: Nils, B., Adatte, T., McKeegan, R., Schoene, B., Keller, G., Eddy, M. P., Regelous, M., and Khadri, S.: Thermal Impact of Deccan Volcanism on Organic Sediments: A Key Factor in Late Cretaceous Climate Instability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10654, https://doi.org/10.5194/egusphere-egu25-10654, 2025.

The emplacement of large igneous provinces (LIPs) is known to be a driver of climate change in Earth’s past. However, the balance of climate warming through CO₂ emission and cooling through weathering is poorly understood.

Our study is focussed on the period between 300 and 150 million years ago (Ma), when the supercontinent Pangaea began to rift and break apart, a process which initiated many of the Earth system and evolutionary upheavals that led to the planet’s current configuration. During this time some of the largest LIPs in Earth history were emplaced, sometimes coinciding with mass extinctions. For example, the Siberian Traps (252 Ma), which is the largest continental LIP by volume, and widely thought to be the driver of the End-Permian Mass Extinction7,16–18. Later in the Mesozoic, the Central Atlantic Magmatic Province (CAMP; 201 Ma), the largest continental LIP by area, has been linked to the end-Triassic. Further, the Karoo and Ferrar LIPs (183 Ma) have been implicated in the end-Pliensbachian extinction, and Toarcian anoxic event respectively. To determine if major LIPs could have led to cooling on multimillion year timescales, and to investigate the cumulative impact of numerous LIP emplacements, we use a long-term climate-biogeochemical model (SCION) integrated with the record of LIP emplacement between 300 and 150 Ma. SCION uses a 3D emulated climate, which allows us to move beyond simple consideration of latitude bands to consider intersections of LIPs with local temperature, relief and hydrology, which is essential for estimating weathering—especially considering the prevalence of extensive aridity in Pangaea.

Of the seven LIPs during the breakup phase of Pangea, only the Central Atlantic Magmatic Province (CAMP) drives noticeable long-term cooling in the model, a minor effect (around 1°C) despite emplacement of a very large surface area in the humid tropics. Similarly, only the CAMP imparts a significant change in the long-term Sr isotope record whereas the other LIPs of this period do not. Due to limited areal extents, and emplacement outside tropical weathering zones, we conclude most LIPs have no significant global cooling effect on multimillion year timescales.

How to cite: Longman, J., Mills, B., and Merdith, A.: Flood basalt weathering has a limited role in driving global cooling during the Mesozoic, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10786, https://doi.org/10.5194/egusphere-egu25-10786, 2025.

The impact of the Siberian Traps emplacement led to the extinction of 90% of marine species and 75% of terrestrial species. Due to the 3-5 Mkm³ of magma emitted over about 1Myr as determined by U-Pb dating. The extensive volcanic activity released massive quantities of gases into the atmosphere, particularly carbon dioxide (CO₂) and sulfur dioxide (SO₂). These emissions came from two main sources: magmatic emissions resulting directly from volcanic activity and thermogenic emissions produced by the intrusion of magmas into carbonate-rich, evaporite-rich, or organic matter-rich sediments within the Tunguska basin. The cumulative carbon emissions from the Siberian Traps are estimated to range between 21 000 and 105 600 Gt.

In the present study we considered the amplitude and timing from CO₂ and SO₂ degassing on the temperature, pH, δ¹³C and their implications for environmental perturbations during the Siberian Traps and the end-Permian mass extinction. We tested various scenarios and their consequences exploring the role of the volcanic sequence duration, mean size of lava flows, metamorphism and the biosphere.

We reconstructed the large igneous province (LIP) volcanic sequence in which we account for both magmatic and thermogenic emissions throughout the entire duration of the LIP emplacement. The SILLi 1.0 model (Iyer et al. 2018) was employed for the thermogenic emission. Parameters considered in the reconstructed sequence include, the duration of emplacement, the volume of lava flows and sills, the characteristics and age of the sediments intruded by sills, and the isotopic (δ¹³C) signature of sediments, organic matter and magma.

The environmental consequences of the reconstructed emission sequences were simulated using the biogeochemical model GEOCLIM. This model considers for both the short-term and long-term processes related to volatile emissions allowing for the calculation of changes in ocean temperature and pH, as well as disruptions in the carbon, oxygen, phosphorus, and alkalinity cycles.

We highlight the prevailing role of thermogenic gases to observe any significative changes in pCO₂, temperature, pH and HCO₃^2- δ¹³C these changes are specifically enhanced when coal bearing sediment are intruded. When intruded coal bearing sediment can cause the pCO₂ and HCO₃^2- δ¹³C to peak up to more than 100ppm and 0.4‰ respectively, over the span of a few centuries.

We demonstrate that the size distribution of flows has very limited impact on the long term tendencies but has a visible one on the short term and that the overall duration of the magmatic sequence has a significant effect. We also show that the collapse of primary productivity amplifies the environmental changes (3 Pal in PCO₂, 2°C in temperature and a decrease of more than 1.5‰ in HCO₃^2- δ¹³C) and that the combination of both volcanic processes (magmatic degassing and contact metamorphism degassing) and the biosphere are needed to partly explain the data.

How to cite: Pierron, A., Le Hir, G., Fluteau, F., Ganino, C., Maffre, P., and Goddéris, Y.: Modeling the Consequences of the Siberian Traps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11056, https://doi.org/10.5194/egusphere-egu25-11056, 2025.

The primary source of Cadmium (Cd) to the environment is volcanic emissions, emitted to the atmosphere in a wide range of particle size and chemical compounds that are easily dispersed by wind. Higher temperature emission sources also release elemental gaseous Cd that then cools and becomes bound to ash particles. Atmospheric transport of volcanic Cd emissions is a function of particle size as well as plume height, with transport of thousands of km possible. In the modern, Cd anomalies in Antarctic ice records are shown to be sourced from long-range transport of volcanic emissions, and Cd anomalies found in Greenland ice cores are shown to be generated by the Laki and Hekla eruptions.

When deposited into oceans Cd is highly soluble and has vertical concentration profiles strongly similar to those of nutrients (e.g. P), suggesting that despite its toxicity to higher life Cd acts as a nutrient for phytoplankton by replacing the Zn cofactor in the enzyme carbonic anhydrase under Zn limited conditions. Cd is exported to sediment as organic matter (OM) bound metal and is subsequently buried or fixed as insoluble Cd sulfide.

Studies of Cd in the geologic record are limited and tend to be focused on use of Cd as an indicator of nutrient levels or paleo-environmental conditions. Enhanced Cd concentrations have also been related to increased drawdown during ocean anoxic events (OAEs) related to enhanced OM preservation and the strong affinity of Cd for sulfide as well as an indicator of basin restriction. Examination of use as a proxy for volcanism has been limited.

Records of Cd levels in sediments deposited during Oceanic Anoxic Event 3 in Arctic Canada, show that at low concentrations (< 10 ppm) Cd has a negative correlation with Zn, consistent with Zn replacement. In contrast, at Cd concentrations above 10 ppm there is strong positive correlation with Zn, suggests a common source enriching both metals. Above 10 ppm, Cd concentrations also show a strong correlation with heulandite, a low temperature alteration product of volcanic glass, suggesting a volcanic origin. This is consistent with abundant bentonite beds with geochemical markers consistent with arc volcanism. This may explain the anomalous high Cd concentrations in late Cretaceous mudstones of northern Canada, and suggest that Cd could be another geochemical marker for enhanced volcanism. However, use of Cd may be more nuanced than other geochemical makers, such as Hg or Te, given its nutrient like properties.

These high Cd levels in OAE3 sediments contaminate surface and groundwaters in the modern, with linkage to human health issues, showing long term impact of volcanism on the environment.

How to cite: Grasby, S.: Can cadmium be used as another proxy for volcanism?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11910, https://doi.org/10.5194/egusphere-egu25-11910, 2025.

Ostracods are among the most abundant microfossils recorded across the Permian/Triassic boundary (252 million years ago). Their fossil record provides an opportunity to assess the impact of environmental changes on the ecosystem and to understand the main drivers behind the biggest mass extinction event in Earth's history. Previous studies have suggested that rapid temperature increase, widespread anoxia, and ocean acidification were the environmental changes driving the extinction. This study uses secondary ion mass spectrometry (SIMS) to measure the geochemical signal of Changhsingian (late Permian) ostracods from the Southern Alps in Italy. We measured the oxygen isotope ratio (δ¹⁸O_ostracod) as a proxy for temperature and the carbon isotope ratio (δ¹³C_ostracod) to assess carbon cycle perturbations. We compared isotopic signals from ostracods found in two shallow-water sections with corresponding sediment data (δ¹³C_carb). Our results show that the δ¹⁸O_ostracod and δ¹³C_ostracod values are similar in the two examined species, and these values parallel the δ¹³C_carb recorded in the host sediments. Our findings highlight the value of ostracods as indicators of temperature change, providing insights into the environmental changes preceding the extinction event and its potential drivers. Further analyses of these microfossils will enhance our understanding of the marine ecosystems' response to dramatic climate warming during the Permian-Triassic mass extinction.

How to cite: Gómez Correa, M. A., Frank, A., Wiedenbeck, M., Gliwa, J., Korn, D., Prinoth, H., Kustatscher, E., and Foster, W. J.: Insights into thermal stress during the Permian-Triassic mass extinction using ostracods from the Southern Alps (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13354, https://doi.org/10.5194/egusphere-egu25-13354, 2025.

The Carnian Pluvial Episode (CPE) is marked by major changes in the climate to significantly more wet and humid conditions, followed by a return to an arid state. This episode is recorded in several stratigraphic sections around the world. The climatic shift is thought to have been driven by perturbation of the global carbon cycle, associated with the emplacement of the Wrangellian Terrain Large Igneous Province (WT-LIP) in the Northern Panthalssic ocean (~231-225 Ma). The event is often linked to the rise and diversification of dinosaurs, major biotic shifts on land along with the establishment of modern ecosystems making it a critical event in Earth's history. Detailed studies of the CPE that examine geochemical evidence of the link to the emplacement of Wrangellia are limited. Here, we present new high-resolution geochemical data, combined with lithological description, of the Carnian in the Knocksoghey Formation sampled throughout the Mercia Mudstone from the Carnduff-2 core, Northern Ireland. The Knocksoghey Formation represents continental sediments, marked by an abrupt shift to increased coarse-grained siliciclastics at the presumed onset of the CPE. These sandy sections are followed by an abundance of anhydrite nodules, with reddish brown mudstones displaying green reduction spots.  Multiple proxies, including changes in carbon isotope and elemental compositions, weathering proxies, Hg/TOC variations, and astrochronology, are utilized to assess the temporal link between the emplacement of the WT-LIP and the onset and pulses of the CPE and to determine the potential mechanisms driving the event. The lithological change to increase coarse-grained siliciclastics is preceded by higher Hg concentrations, as well as a negative carbon isotopic excursion in the range of ~3-4 ‰, which points to an increased volcanic activity. This interval, which appears to represent wetter conditions, is followed by sedimentological evidence of more arid conditions marked by increased gypsum followed by a second increase in Hg/TOC. Altogether, further evidence of wetter conditions close to the Carnian–Norian Boundary suggests that volcanism was closely linked to the alternations between an arid and humid climate during the CPE.

How to cite: Mohamed Shahid, M., Al Suwaidi, A., Ossa Ossa, F., and Ruhl, M.: The Carnian Pluvial Episode: Timing and Mechanism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15284, https://doi.org/10.5194/egusphere-egu25-15284, 2025.

Late Triassic Norian records from high-latitude localities and the Paleo-Antarctic circle are extremely limited and relatively understudied. Here, we present new geochemical proxy data measured on samples representing fluvial-lacustrine sediments of the Parmeener Supergroup, Unit 4 from Tasmania, Australia, of Early-Mid Norian age (~216-223 Ma). These records offer a unique opportunity to reconstruct the Norian climate and environmental conditions close to the paleo-South Pole and during an interval of major global climatic and ecological condition transitions following the arid conditions of the Early–Middle Triassic and Carnian Pluvial Episode. The TOC values for these Norian age sediments were found to be generally low (0.1-4%). However, steep increases in the TOC values of up to 30-40% were observed, corresponding to the deposition of several coal seams. XRF and Hylogging data from this part of the core show a rapid increase in kaolinite, smectite, and other clay minerals, suggesting an elevated weathering pattern. Preliminary stable isotope results from this study show δ¹³C_org values varying from -27.5‰ to -23‰ (vs. VPDB). One steep negative δ¹³C_org excursion, with values reaching as low as -27.5‰, was observed in the upper part of the core. This negative excursion also coincides with the occurrence of two volcanic tuff layers, likely from the proto-Pacific convergent margin along the Antarctic Peninsula. Previous studies of cores from nearby localities have dated stratigraphically equivalent tuffs to 217.84±0.19 Ma (Calver et al. 2021; DOI: 10.1080/08120099.2021.1888804). Hg/TOC values also show a relative increase associated with the volcanics. δ¹³C_org data from the core is comparable to other global records (e.g. Sakahogi, Japan;  Pignola-Abriola, Italy; and Kennecott Point, British Columbia), which show similar trends of δ¹³C_org profile, though somewhat lighter values for the Norian.

This multiproxy analysis from Tasmania provides a distinctive and continuous record of climate change in the high-latitude Southern Hemisphere during the Norian, shedding light on the significant climatic and environmental changes that occurred during this time.

How to cite: Al Suwaidi, A., Ghoshal, I., Fox, C., Ohkouchi, N., Ogawa, N., Suga, H., Painkal, M., and Ruhl, M.: The Norian Record of Climatic and Environmental Change in the Paleo-Antarctic , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15797, https://doi.org/10.5194/egusphere-egu25-15797, 2025.

The Permian–Triassic mass extinction led to the loss of 80-90% of marine species making it the most catastrophic extinction of the Phanerozoic. The Permian-Triassic transition is characterized by a major clime warming event, major environmental upheaval and a high magnitude mass extinction event. The associated expansion of oxygen minimum zones, even into shallow waters, is commonly considered as a global driver of this extinction. However, while the intensification of deep-water anoxia has been demonstrated utilising U isotopes at multiple sites globally, recent studies have shown increasing evidence for spatial and temporal variability in shallow marine redox conditions across the Permian–Triassic transition. This highlights the need to constrain local redox conditions for shallow marine basins to determine if they were affected by anoxia and to link local redox changes, if any, back to the timing of the extinction event. Here, we present redox sensitive element (Re, V, U and Mo) and rare earth elements and yttrium (REY) data from three shallow marine basins, located in the western Paleotethys (Dolomites, Italy), Neotethys (Antalya, Türkiye), and the Barents Sea (Svalbard, Norway) to understand the role of oxygen availability as an extinction driver in different environmental and latitudinal settings. At all three sites, redox sensitive metal enrichments were observed before the onset of the extinction, suggesting deoxygenation, potentially creating anoxic conditions. However, these enrichments appear to be lithology- rather than redox-driven in the Svalbard section and are not persistent within the Dolomites sections, suggesting only episodic deoxygenation. Furthermore, the Dolomites and Antalya sections generally display lower metal enrichments starting at the extinction onset, suggesting lower oxygenation before the extinction than during it. Seawater-like REY patterns were not preserved at all sections, however, all three localities included sections characterized by negative Ce anomalies typical for oxic seawater conditions during the extinction. This suggests that anoxia was not a driving extinction factor in these shallow marine ecosystems, indicating other extinction mechanisms should be considered.

How to cite: Frank, A., Grasby, S., Buchwald, S., Gomez Correa, M. A., Karapunar, B., Kustatscher, E., Prinoth, H., and Foster, W.: Assessing the role of anoxia as an extinction driver in shallow marine basins during the Permian–Triassic mass extinction., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16641, https://doi.org/10.5194/egusphere-egu25-16641, 2025.

The Ludfordian (~424 Ma) “Lau Event” was the last of three Silurian mass extinctions. It is characterized by one of the largest carbon isotope excursions of the Phanerozoic with bulk rock δ¹³C increasing to ~8‰ in less than 1.5 million years [1]. Possible explanations include enhanced burial of organic matter driven by marine anoxia, changes to weathering rates, and/or increased nutrient flux to the ocean [2]. However, the underlying driving mechanism remains debated. To better inform on the environmental and climatic conditions during the Lau Event, we investigated the boron, strontium, carbon and oxygen isotopic composition of well-preserved brachiopod specimens recovered from four drill cores in the Baltic Basin of central Lithuania: Vidukle-61, Bebirva-111, Bebirva-108 and Bebirva-110, which define a deeper to shallow shelf transect in the palaeo-tropics of the Rheic Ocean. All cores yielded abundant specimens which were screened by optical microscope inspection to identify pristine clean shell parts for sampling. Trace element analyses confirmed excellent preservation and no clay contamination as evident by Mn/Ca and Al/Ca analyses both <300 µmol/mol for most samples (n=65). Preliminary brachiopod carbon isotope data reveal a δ¹³C increase by approximately 8‰, corroborating the bulk rock pattern, with brachiopod δ¹⁸O values ranging from approximately –7‰ to –2.5‰. Boron isotope analyses are ongoing and will be used to assess changes in seawater pH and atmospheric CO₂ levels. Further constraints on seawater chemistry and the age of the samples will be provided from paired ⁸⁷Sr/⁸⁶Sr analyses. Our multi-proxy records will provide new knowledge to enhance understanding of this enigmatic event and in assessing the effects of climate changes on past ecosystems.

References

[1] Cramer B.D. & Jarvis I. (2020) Chapter 11 – Carbon Isotope Stratigraphy. Geologic Time Scale 2020, 309-343, https://doi.org/10.1016/B978-0-12-824360-2.00011-5.

[2] Zhang, F, Frýda, J., Fakhraee, M., et al. (2022) Marine anoxia as a trigger for the largest Phanerozoic positive carbon isotope excursion: Evidence from carbonate barium isotope record. Earth and Planetary Science Letters, 584, https://doi.org/10.1016/j.epsl.2022.117421.

[3] Jurikova, H., Garbelli, C., Whiteford, R. et al. (2025) Rapid rise in atmospheric CO₂ marked the end of the Late Palaeozoic Ice Age. Nat. Geosci., https://doi.org/10.1038/s41561-024-01610-2.

How to cite: Harbour, B., Jurikova, H., Rae, J., Raddatz, J., Radzevicius, S., Ainsaar, L., Lepland, A., and Prave, T.: New climate reconstruction of the Lau Extinction Event (Late Silurian) from boron isotopes in brachiopods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16711, https://doi.org/10.5194/egusphere-egu25-16711, 2025.

Eruptions of the Central Atlantic Magmatic Province (CAMP) at 201.6 Ma are linked to the end-Triassic extinction (ETE) on land via competing radiative forcings, which caused extreme alternations in warming and cooling and humidity and aridity (climatic whiplash) [c.f., (1)]. Although ETE effects on land-plant diversity are often described as minor, tropical flora exhibit significant changes in plant physiognomy, paralleling pCO₂ and hydrological variations recorded from the same strata.

Most dramatic is the extirpation of the vesicate pollen group exemplified by Patinasporites and Enzonalosporites, known to have low latitudinal preferences. In the Late Triassic Pangean tropics, this likely voltzialian conifer group remained a major component of the palynoflora up to the ETE and the time of the earliest known CAMP lavas, whereas it is progressively rarer or absent in older, more northerly Late Triassic strata, and virtually absent in the paleoarctic. This trend is consistent with the northward drift of central Pangea, but the diachronous last appearances have resulted in some biostratigraphic mischief, if other markers are ignored. Also dramatic is the tropical expansion of the dipteridaceous fern Clathropteris meniscoides. This tough-leaved fern is abundant at mid- to high-latitudes in Late Triassic and Early Jurassic continental units of Pangea but absent from tropical Late Triassic-Early Jurassic assemblages except during the earliest to peak CAMP eruptive interval, where it becomes common or even dominant. In fact, its spores (Granulatisporites and Converrucosisporites) comprise the "fern spike" in the Newark Basin at the ETE (2, 3).

Both of these floral phenomena are inconsistent with warming as an extinction driver during the CAMP episode and instead are consistent with CAMP-driven mega-volcanic winters. A similar pattern is seen among continental tetrapods, where insulated forms (e.g., pterosaurs, dinosaurs, mammals) preferentially survive while all large non-insulated pseudosuchians perish (4).

Cheirolepidaceous conifer leaf and stomatal morphology from deposits show trends related to CAMP events (5). These include short, scale-like leaves with thickened cuticle and sunken stomata that are traditionally interpreted as adaptations to heat and evaporative stress, but are also seen in cold-adapted conifers, suggesting these traits are "poly-tolerance" (6) adaptations. In fact, tropical conifer assemblages directly associated with the ETE have the thickest and shortest leaves of all tropical forms, suggesting adaptations to freezing.

Further, hydrological conditions based on hydrogen isotope data captured in n-alkanes suggest amplified precession and obliquity pacing (7). This observation is consistent with both amplification of the hydrological system during times of CAMP-driven high pCO₂ seen in pedogenic carbonates, molecular proxies from chlorophyll degradation products, and volcanic winters reflected in the floral disruption patterns. From these collective observations, we suggest that "climatic whiplash" at seasonal- and Milankovitch-timescales was a critical driver of the continental ETE and associated floral responses, and that such processes may have panned out elsewhere in Earth history.

References:

1, Swain+ 2025 Nature Rev Earth Env 6:35-50. 2, Olsen+ 2002 Science 296:1305. 3, Fowell+ 1994 GSA Spec Pap 288:197. 4, Olsen+ 2022 Sci Adv 8:eabo6342.  5, Cornet 1977 PhD thesis, PA State. 6, McCulloh+ 2022Tree Phys  43:1-15. 7, Landwehrs+ 2022 PNAS 119:e2203818119.

How to cite: Whiteside, J., Olsen, P., and Schaller, M.: Multiple geochemical and paleobiological parameters define a “climatic whiplash” during CAMP volcanism, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16763, https://doi.org/10.5194/egusphere-egu25-16763, 2025.

Two-hundred-million years ago, the emission of an estimated 100,000 Gt of CO₂ during pulsed eruptions in the Central Atlantic Magmatic Province had dire consequences for the biosphere and resulted in the end-Triassic extinction. The exact causes for the extinction of organisms remain enigmatic, but a complex and drawn-out scenario is emerging that is in line with the pulsed activity in the CAMP. Palynological assemblages obtained from the immediate extinction interval from multiple locations exhibit a remarkable darkening of pollen and spores that is at odds with simple thermal maturation during burial. Here, we investigate this latest Triassic “dark zone”, using the Palynomorph Darkening Index (PDI) obtained from trilete fern spores in the Schandelah-1 core (North Germany) and Classopollis pollen in drill cores from Denmark (Stenlille-4), the United Kingdom (ICDP Prees-2), and Luxemburg (Elvange). Coinciding with a collapse of forest vegetation and the spread of a pioneer fern vegetation, the fern spores’ PDI reaches peak darkness in the uppermost Triletes Beds from Germany and equivalents elsewhere. This darkening event is mimicked in highest PDI values in Classopollis from the upper Lilstock Formation in the Prees-2 core and equivalent beds in the Elvange and Stenlille-4 cores. Controlled heating experiments of Lycopodium spores followed by PDI analyses suggest that latest Triassic darkening of palynomorphs is consistent with frequent surface fires carried in fern savannahs. The ensuing extreme soil erosion during wetter intervals resulted in mass removal of charred organic material in coastal sediments. The impact of continental-scale wildfires during the height of the end-Triassic mass-extinction suggests intense climate change exerting heat stress on vegetation as a major factor in the collapse of terrestrial ecosystems.

How to cite: van de Schootbrugge, B., Hollaar, T., Kent, M., Lomax, B., Meredith, W., Lindström, S., Bos, R., Looy, C., Benca, J., Duijnstee, I., Hesselbo, S., Richoz, S., Vandenbroucke, T., Vermeer, J., Kuhlmann, N., Belcher, C., Waajen, I., Peterse, F., and Nierop, K.: Continental-scale wildfires during end-Triassic greenhouse warming, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17654, https://doi.org/10.5194/egusphere-egu25-17654, 2025.

The relationship between Large Igneous Provinces (LIPs) and major mass extinctions has long been recognized. The K/Pg boundary (KPB) extinction is particularly notable due to the near-simultaneous occurrence of two major catastrophic events: the Deccan volcanism and the Chicxulub impact. To gain a clearer understanding of how volcanic activity drives environmental stress, this study investigates the influence of the Deccan volcanism on ecosystems. Our approach includes detailed species counts alongside isotopic and geochemical analyses of two well-preserved sections from the Mudurnu-Göynük and Haymana basins in Central Anatolia (Turkey).

In the Haymana Basin, δ¹³C measurements from the late Maastrichtian display cyclical fluctuations, reflecting precession-driven climate changes. Each cycle ends with a rapid cooling event, indicated by a positive shift in δ¹⁸O values. Spectral analyses of high-resolution δ¹³C and δ¹⁸O isotopic records from planktonic and benthic foraminifera further confirm the influence of orbital forcing, particularly precession cycles, on Late Cretaceous climate variability. The precession-driven cycles reveal climate variations that influenced primary productivity and ocean stratification. During precessional highs, both planktonic and benthic δ¹³C values increase, accompanied by a decrease in Δ¹³Cplanktonic-benthic values and a shift towards more positive δ¹⁸O values, suggesting enhanced water column mixing. Notably, benthic δ¹³C values are consistently heavier than their planktonic counterparts, which may reflect local upwelling conditions. However, the decreasing trend in productivity marker trace elements such as nickel (Ni) and copper (Cu) raises questions about the persistence and extent of upwelling in the Haymana Basin during this period.

Concurrently, a quantitative analysis of planktic foraminifera reveals a progressive decline in species diversity throughout the late Maastrichtian, with an accelerated decline just before the K/Pg boundary. In the Göynük and Okçular sections, this decline in biodiversity coincides with intervals of low magnetic susceptibility, suggesting a possible link to ocean acidification during the late Maastrichtian. The K/Pg boundary is marked by a distinct reddish oxidized layer, 2-3 mm thick, which signals a sequence of critical events: the abrupt disappearance of large, specialized foraminiferal taxa (e.g., globotruncanids, racemiguembelinids, planoglobulinids), an increase in mercury (Hg) levels, and elevated concentrations of trace elements such as iridium (Ir), tellurium (Te), nickel (Ni), chromium (Cr), and cobalt (Co).

In terms of the faunal response, we observe peaks in Thoracosphaera and Guembelitria cretacea, indicating a collapsed ecosystem following the K/Pg boundary event. In conclusion, our comprehensive analysis of paleontological, isotopic, and geochemical data demonstrates that the detrimental effects of Deccan volcanism began prior to the Chicxulub impact, predisposing marine ecosystems to the K/Pg mass extinction event.

How to cite: Karabeyoglu, U., Adatte, T., Thibault, N., Spangenberg, J., and Regelous, M.: Deccan Volcanism, Precession-Driven Climate Variability, and the Chicxulub Impact, Drivers of Ecosystem Stress and Mass Extinction at the K/Pg Boundary: Insights from the Eastern Tethys Region, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18650, https://doi.org/10.5194/egusphere-egu25-18650, 2025.

Studies on extant spores belonging to the family of clubmosses (e.g., Lycopodium) have shown that micro-FTIR spectroscopic analyses can reveal the quantity of UV-absorbing compounds (UACs) in the organic walls of the spores and thus be used to reconstruct UV-B radiation and the ozone layer degradation rates at the time of formation of the spore. Here, we present new data from Toarcian age sporomorphs from marine organic-rich marls to shales, deposited in the offshore to shoreface environments from a core from the Paris Basin, France, to evaluate the applicability of this method in the geological record. Our results are integrated with existing high-resolution geochemical and geodynamic data from the core to provide a comprehensive understanding of the system. Understanding the fluctuations in UV-B radiation during the Early Toarcian would allow us to understand whether Karoo and Ferrar Large Igneous Province activity resulted in the release of halides that triggered a depletion of the ozone column in the atmosphere, leading to increased UV-B exposure on Earth’s surface, potentially contributing to environmental and ecological perturbations on land and in the oceans. A quantitative palynofacies analysis performed on 32 samples from the core revealed the presence of anoxic conditions during the deposition of the deeper portion of the core, reflected in the abundance of AOM and lack of sporomorphs and marine elements in the palynological record. On the other hand, the palynological record shows a decrease in AOM and an increase in sporomorphs and marine elements at the passage from the Bifrons Zone to the Variabilis Zone, marking a shift to a shallower marine depositional environment characterised by enhanced continental inputs and decreased oxygen depletion. Previous studies of the early Toarcian Carbon Isotope Interval have revealed teratological pollen and spores from localities in the northern hemisphere, linking these mutations to prolonged exposure to enhanced UV-B radiation. Using micro-FTIR, sporomorph morphology analysis (via SEM), palynofacies models and integrating this with existing data we are able to better link changes in vegetation with LIP activity. Understanding the impact of volcanic activity on atmospheric chemistry and ozone thickness, which increases UV-B rays reaching Earth, would help us grasp their effects on life and how UV-B changes influence mutagenesis in organisms and eventually have a role in extinction events.

How to cite: De Luca, R., Al-Suwaidi, A., Ceriani, A., Spina, A., Gasparrini, M., and Lasseur, E.: Impact of elevated UV-B radiation on Toarcian spores and pollen mutagenesis., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18808, https://doi.org/10.5194/egusphere-egu25-18808, 2025.

The Messinian Salinity Crisis was the most extreme paleoenvironmental perturbation that has ever taken place in the Mediterranean. Approximately 7 million years ago, the straits connecting the Mediterranean Sea to the Atlantic Ocean started to restrict, and by 5.5 million years they closed. High-amplitude fluctuations in both temperature and salinity gave place to a hypersaline isolated Mediterranean, where marine organisms struggled to survive. In our recently published studies, we assembled and revised the marine fossil record from before and after the crisis in order to quantify the effect of the crisis on the biodiversity of the Mediterranean. We documented for the first time a clear perturbation of the biota even during the restriction phase, as well as a high degree of reorganisation of the marine ecosystem after the crisis, with most of the change in the taxonomic composition attributed to species turnover. Only a handful of endemic Mediterranean species may have survived the crisis. Furthermore, the present-day NW-to-SE decreasing gradient in species richness first appeared after the Messinian salinity crisis, suggesting that neither the distance from the Atlantic source nor the temperature gradient are the causes of the gradient today. Finally, we propose a model for the disruption in marine functional connectivity patterns, which is associated with the formation of a large evaporitic basin. This model can now be tested against the diverse ecosystem structures of the past that are associated with marginal marine basins formed due to the birth and death of the oceans.

How to cite: Agiadi, K., Hohmann, N., Coll, M., Vasiliev, I., Camerlenghi, A., and Garcia-Castellanos, D. and the expert team: The impact of the Messinian Salinity Crisis on Mediterranean marine biodiversity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1488, https://doi.org/10.5194/egusphere-egu25-1488, 2025.

How to cite: Voelker, A., Duque-Castaño, M., Mega, A., O'Neill, E., Salgueiro, E., and Rodrigues, T.: Neogloboquadrinids in the mid-latitudinal, subtropical NE Atlantic during the Early-to-Middle Pleistocene: evidence for “not (sub)polar” variants and one extinction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2260, https://doi.org/10.5194/egusphere-egu25-2260, 2025.

The termination of the Messinian salinity crisis 5.33 million years ago is often attributed to the Zanclean megaflood, a catastrophic event that rapidly refilled the Mediterranean Sea. This study provides compelling evidence for this megaflood, tracing its impact from an onshore shallow marine corridor in southeastern Sicily to the offshore Noto Canyon. Key indicators include (i) over 300 streamlined, asymmetrical erosional ridges aligned with the flood direction, (ii) a poorly sorted breccia layer situated between the Messinian and Lower Zanclean Trubi Formations, (iii) soft-sediment deformation and clastic injections within the breccia and underlying layers, and (iv) a 20 km-wide erosional channel linking the ridges to Noto Canyon. Numerical modeling reveals how the excavation of the channel and canyon influenced the flow's velocity and direction. These findings confirm that the Messinian salinity crisis ended with a catastrophic flood, highlighting a significant Mediterranean sea-level drop prior to the event.

How to cite: Micallef, A., Barreca, G., Hübscher, C., Camerlenghi, A., Carling, P., Abril Hernandez, J. M., Periáñez, R., Garcia-Castellanos, D., Ford, J., Haimerl, B., Hartge, M., Preine, J., and Caruso, A.: Land-to-sea indicators of the largest megaflood in the geological record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3249, https://doi.org/10.5194/egusphere-egu25-3249, 2025.

Because of its fast growth, gypsum can rapidly entrap biogenic material and biomolecules, allowing for excellent preservation at geological time scale. The characterization of biota having thrived in the gypsum-mother brines can contribute to elucidate the paleoenvironmental conditions in the water column and at the seafloor during the formation of ancient salt giants; such reconstruction is challenged by the absence of modern analogues. A prominent example are the primary gypsum deposits that accumulated in the Mediterranean basin about 6 Ma ago, during the Messinian salinity crisis (MSC), when this basin turned into the youngest salt giant in Earth history following its partial isolation from the Atlantic Ocean. Two main types of gypsum are recognized: a) bottom-grown selenite, consisting of vertically-oriented twinned crystals and b) laminar gypsum cumulate, formed by the accumulation at the seafloor of tiny gypsum crystals nucleated in the water column, mixed with organic-rich material. Biosignatures in both types of gypsum were investigated through optical, electron and confocal laser scanning microscopy, Raman spectroscopy, and lipid biomarker analyses. Bottom grown gypsum is typified by abundant diatom remains that indicate deposition in a marine basin influenced by freshwater input. Other abundant components are filamentous microfossils corresponding to remains of sulfide oxidizing bacteria. These biogenic remains are commonly coated by microbial dolomite microcrystals and authigenic clays, which suggest that organic matter and biogenic silica underwent severe early diagenetic alteration. Planktic diatoms, calcareous nannofossils and early diagenetic dolomite are also recognized in cumulate gypsum deposits. Such composition suggests high primary productivity in the water column, inducing the export of organic matter to the seafloor and the formation of dolomite following bacterial sulfate reduction. The mechanisms promoting gypsum nucleation in the water column are instead still enigmatic. The late Miocene gypsum represents an excellent archive of biosignatures, including bacterial cells. The microbial assemblage indicates that gypsum formed in relatively deep, stratified marine basins with intermittent sulfidic bottom-water conditions, promoting intense microbially-mediated early diagenetic processes at the expenses of organic matter and biogenic silica. Such circumstances imply that the paucity of skeletal remains in the MSC sedimentary record may be the result of a taphonomic bias rather than of inhospitable hypersaline conditions induced by massive evaporation of the Mediterranean water mass.

How to cite: Dela Pierre, F., Nallino, E., Natalicchio, M., Pellegrino, L., Aloisi, G., Birgel, D., Guibourdenche, L., and Peckmann, J.: Gypsum as an archive of biosignatures: what can we learn from the late Miocene Mediterranean salt giant?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4440, https://doi.org/10.5194/egusphere-egu25-4440, 2025.

Timing is important for comprehending Earth's biological and climatic processes shaping evolution, extinction, and recovery. Causes and consequences of changing climate can be unraveled only if geological proxy data from different regions are synchronized in time so that causality arguments can be tested rigorously. Many key climate proxy records of the last 100 million years come from deep ocean sediments, but they are currently not sufficiently synchronized across regions on Milankovitch cycle level. The acquisition of accurate chronological data that allow for synchronization across regions is of paramount importance for meaningful interpretations of proxy records.

Here we make the case to form an international coordination network to synchronize regional climate records of the last 100 million years. This network will contribute to revise and recalibrate the dating tools available to paleoclimatologists - that is, the local and regional information obtained from bio-, magneto-, and chemo-stratigraphy as well as radioisotopic geochronology - with the synchronizing tool of astrochronology. Cross-fertilization of expertise is needed to generate new age models for sediment records from which key climate events have been or can be reconstructed, including micropaleontological studies of scientific ocean drilling legacy material. We invite the scientific community to recognize this shortcoming, to join our efforts, and to help raise funds to make the envisaged Time Integrated Matrix for Earth Sciences (TIMES) program a reality.

How to cite: Westerhold, T., Agnini, C., Anagnostou, E., Hilgen, F., Hönisch, B., Meckler, N., Pälike, H., Wade, B., Sosdian, S., and Kasbohm, J.: Paleoclimate reconstructions need better age models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5060, https://doi.org/10.5194/egusphere-egu25-5060, 2025.

During the Messinian, the Mediterranean Basin became highly sensitive to environmental changes due to the gradual restriction of water exchange with the Atlantic Ocean. This led to the widespread deposition of organic-rich layers known as sapropels, indicating significant disturbances in the carbon and oxygen cycles. These sediments formed under conditions of oxygen depletion, likely due to periodic weakening of the thermohaline circulation. Understanding the causes and extent of this circulation weakening in the past is crucial for predicting present and future deoxygenation trends in the Mediterranean under climate warming.

For this purpose, we investigate a Messinian sapropel-bearing succession cropping out at Monte dei Corvi (Ancona, central Italy) with mineralogical, petrographic, micropaleontological and stable carbon and oxygen isotopic analyses. Our findings reveal that sapropel deposition occurred due to increased sea surface buoyancy, which inhibited thermohaline circulation, consequently reducing bottom-water oxygen content and impacting bioturbating organisms. Within the lithological cycle, the recovery of an efficient thermohaline circulation is recorded by thin packstone layers underlying the marly limestone/marlstone, which record intense bottom currents activity. The accumulation of marly limestone/marlstone during periods of high primary productivity and organic carbon export to the seafloor led to bottom hypoxia but not organic matter preservation. Furthermore, the latter was deposited with surficial seawater density in the range of modern Adriatic, suggesting that primary productivity can promote bottom hypoxia even with similar modern deep oxygen renewal rates. These lithological changes were likely influenced by variations in the Adriatic Deep Water formation system paced by precession-driven climatic and oceanographic changes.

Integration of previously published Sea Surface Temperature (SST) data with our new isotopic data indicates that variations in Sea Surface Salinity (SSS) primarily controlled sapropel deposition, with the SSTs of sapropel deposits aligning closely with projected SST in the Eastern Mediterranean at the end of this century under climate warming. In this future scenario, warming will be coupled with an SSS increase, which likely counteract the density loss provided by temperature, making the bottom deoxygenation in the Eastern Mediterranean abysses unlikely. However, we caution that additional factors such as winter heat waves and eutrophication could exacerbate Mediterranean oxygen depletion and should be considered in model-based projections.

How to cite: Mancini, A. M. and Negri, A.: The climatic and oceanographic setting during the Messinian in Northern Adriatic Sea: what can be learned for present and future deoxygenation dynamics?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6386, https://doi.org/10.5194/egusphere-egu25-6386, 2025.

The European Micropalaeontological Reference Centre (EMRC) was established in 2015 in order to provide a permanent archive for published micropaleontological collections. The centre is housed in the office of Micropress Europe on the second floor in the main building of the AGH University of Krakow, next to the grand staircase. The EMRC originally was set up using the Heron-Allen Library at the Natural History Museum as a model – as a research centre containing collections of archived microslides, microscopes, a library of micropaleontological books and journals, and a large collection of reprints. The centre provides a welcoming atmosphere for visitors who wish to carry out micropalaeontological research or simply view collections.

Since its establishment, a number of Micropalaeontologists have deposited type slides or their entire published collections at the EMRC. The foraminiferal collection now consists of 25 wooden cabinets, each housing on between 1,000 and 2,000 microscope slides. One cabinet is reserved for primary type specimens (holotypes, paratypes and metatypes). The EMRC collection now houses the holotypes of over 60 species of foraminifera, and >250 paratypes and metatypes.

In 2023, we acquired the microslide collection of D.G. Jenkins, which includes the shipboard micropalaeontological samples from DSDP Legs 9 and 29. In the summer of 2024, we archived the first shipment of micropalaeontological samples and slides from the collections of W.A. Berggren, who participated in several of the early DSDP expeditions. These include slides and residues from the JOIDES Expedition cores (the precursor of the Deep Sea Drilling Project expeditions) and the early DSDP expeditions (Legs 1, 2, 3, 4, 12, 13, 14, 15, 22, 72). The Berggren collection at the EMRC includes the shipboard micropalaeontological samples from DSDP Leg 12 as well as a sizable collection of picked faunal slides from DSDP Site 516 used by Berggren to revise the Miocene zonation of planktonic foraminifera, which was published in the DSDP Leg 72 volume. The Kaminski Collection at the EMRC contains the shipboard micropalaeontological slides from ODP Legs 105 and 123, and numerous picked slides from DSDP/ODP Sites 263, 643, 767, 959, from the ACEX Expedition to the Arctic Ocean, and from the Leg 323 sites in the Bering Sea. The Gradstein Collection contains the slides from DSDP Leg 44. The newly acquired Brent Wilson Collection contains slides from DSDP Sites 148 and 926. The EMRC has quickly become a major repository tasked with helping preserve our worldwide DSDP/ODP heritage. A complete list of slide collections housed at the EMRC will be made available on the Micropress Europe website.

Micropaleontologists can arrange to visit the European Micropalaeontological Reference Centre by contacting the Curator, Dr. Justyna Kowal-Kasprzyk, at the AGH University of Krakow [j.kowal.kasprzyk@gmail.com].

How to cite: Kaminski, M. A. and Kowal-Kasprzyk, J.: The DSDP/ODP Microslide Archive at the European Micropalaeontological Reference Centre in Kraków Poland , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6494, https://doi.org/10.5194/egusphere-egu25-6494, 2025.

The Levant Basin is the only deep Mediterranean basin where the entire section representing the Messinian Salinity Crisis (MSC) has been penetrated by wells tied to high-resolution 3D seismic surveys. Based on the new data from the Levant, a series of recent studies challenge the desiccation paradigm dominating the MSC literature for >50 years.

The first study (Gvirtzman et al., 2017) identified the transition from Stage 2 to Stage 3 of the MSC as an Intra-Messinian Truncation Surface (IMTS), separating the nearly 2 km thick salt sequence from the overlying ~100 m thick upper clastic-rich anhydrite unit. The origin of the flat IMTS was interpreted as a result of submarine dissolution in odds with previous interpretations that argued for subaerial erosion.

Two following studies (Manzi et al., 2018, 2021) identified the Stage 1 deposits below the salt as a 10s-of-m thick (below seismic resolution) foraminifera-barren interval (FBI), composed of shales with no evaporites. This unit indicates that during Stage 1, salinity in the deep basin progressively increased and marine organisms gradually disappeared, but still with no salt deposition.

The identification of Stage 1 deposits (shale) below the salt and Stage 3 deposits (sand+shale+anhydrite) above the salt, leads to the conclusion that the entire salt sequence was deposited during Stage 2, i.e., within a short period of 60 kyr. At that time, sedimentation rate jumped by three order of magnitude compared to the pre- and post-MSC deposits, reaching a few cm/yr like the modern Dead Sea and artificial salinas.

Following the suggestion that the top salt was truncated in deep waters by dissolution, Moneron and Gvirtzman (2022) further showed that the Stage 3 unit overlying the truncation surface contains a dense net of channels, characterized by submarine aggradation characteristics (levee height, channel depth, and channel-floodplain coupling). This adds up to the conclusion that evidence previously interpreted as indications for subaerial exposure (erosion and fluvial channels), are better explained by submarine processes (dissolution and turbidite channels).

Finally, based on the reconstruction of the Messinian Nile River, Gvirtzman et al. (2022) estimate the amplitude of the MSC sea-level drop by ~600 m. Accordingly, salt was deposited in a water depth of >1 km in the Levant Basin and probably >2 km in the Herodotus Basin. This limited drawdown of ~600 meters representing geomorphological equilibrium of River Nile, cannot rule out shorter (<10 kyr) and stronger (1.7–2.1 km) event as recently deduced from Chlorine isotopes constrain (Aloisi et al., 2024). Note, however, that even during maximal drawdown, the Ionian and Herodotus basins remained filled with >1 km-deep brine. 

How to cite: Gvirtzman, Z.: Three MSC Stages separated by two major unconformities: Reviewing 10 years of research on the Messinian Section of the Levant Basin , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6854, https://doi.org/10.5194/egusphere-egu25-6854, 2025.

The majority of micropaleontological observations of Cretaceous successions were conducted on deposits in the Atlantic and Tethyan oceans. However, the southern high-latitude Cretaceous formations remains understudied. During expedition Leg 369 of the International Ocean Discovery Program (IODP), 73 cores were collected from Site 1512 in the Australian Bight, targeting deposits of the Turonian to Santonian interval.

Twenty-nine samples were analyzed using plain polarized light microscope. From each sample, approximately 300 foraminifera specimens were extracted and classified into distinct groups based on their morphological characteristics. These groupings enabled further analysis, which involved sorting the specimens according to taxonomic types. To highlight key distinguishing features, selected taxa were examined using scanning electron microscopy (SEM). A total of fifty-nine taxa were identified, forty-two of which were formally defined at the species level. Species identification depended on established taxonomic frameworks.

Several of the southern-latitude taxa exhibit significant variation in morphology compared to the formerly described planktonic, calcareous, and agglutinated foraminifera from the Northern Hemisphere. Seven newly reported species were identified in the current material: Sculptobaculites sp. 1, Bulbobaculites sp. 1, Bulbobaculites sp. 2, Bulbobaculites sp. 3, Gerochammina sp. 1, Rectogerochammina sp. 1, and Praedorothia sp. 1. In addition, two Turonian biozones defined in the Northern Hemisphere were recognized. The first is planktonic Whiteinella brittonensis foraminiferal biozone consisting of Whiteinella brittonensis, Whiteinella aumalensis, Whiteinella baltica, Muricohedbergella delrioensis, and infrequently observed Planohedbergella prairiehillensis. The second is Bulbobaculites problematicus biozone characterized by agglutinated foraminifera, including Bulbobaculites problematicus, Spiroplectammina navarroana, Eobigenerina variabilis, Textulariopsis rioensis, Textulariopsis texhomensis, and Gerochammina lenis.

The establishment of these biozones provides valuable connections to those in the Northern Hemisphere during the Turonian age. Additionally, this research sheds light on the enigmatic 'Austral Province', a previously understudied region of Late Cretaceous foraminifera. By analyzing the faunal composition, we gain insights into key drivers of foraminifera distribution, including ocean circulation patterns (paleoceanography) and climate conditions (paleoclimate). These findings have significant implications for understanding the dynamics of the Tethys and Atlantic oceans.

How to cite: Hilali, I., Wolfgring, E., Waskowska, A., and Kaminski, M.: Insight into the Turonian to Santonian Foraminiferal Biostratigraphy in the Southern Hemisphere , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7790, https://doi.org/10.5194/egusphere-egu25-7790, 2025.

The ANZIC* Continent and Ocean Research & Education (CORE) grant, previously known as the ANZIC-IODP Legacy Analytical Funding (AILAF) scheme, began in 2012 with a visionary initiative: to provide "Special Funding" for innovative analytical research in Australia and New Zealand on existing samples collected throughout the DSDP, ODP, IODP I, and IODP II—many during expeditions undertaken by the JOIDES Resolution. Since its inception, this grant program has been pivotal in advancing scientific research related to ocean drilling and micropaleontology, creating a bridge between archived materials and groundbreaking new discoveries.

In this talk we will highlight three exemplary micropalaeontology projects from the ANZIC community that were supported by the CORE grant scheme, showcasing the enduring value of archived ocean drilling materials:

• Improving Species Identification from Short Sedimentary Ancient DNA (sedaDNA) Sequences. This project develops ‘sedaDNA-at-1.0,’ a new bioinformatics tool for assembling short sedaDNA sequences into longer fragments, enabling more accurate species-level identification. By comparing outputs from traditional and enhanced computational approaches, this tool provides a valuable resource for sedaDNA researchers, with implications for reconstructing past ecosystems.
• Ecosystem Change Through the Neogene in Australia: Documenting the rise of C4 vegetation by using leaf wax isotope ratios from marine sediments collected during DSDP Leg 90 and ODP Leg 122, this project documents the timing of the C3 to C4 plant transition in central and northwestern Australia. The transition occurred at ~3.5 Ma, significantly later than on other continents, highlighting regional variations in vegetation thresholds and offering insights into the future vulnerabilities of Australian ecosystems.
• Extension of Stable Isotope Records at Site U1361 on Wilkes Land Continental Rise, East Antarctica: This project presents a complete ~4-million-year nitrogen and organic carbon isotope record from IODP Site U1361. The results highlight an isotopically light period between ~1.6–0.35 million years, followed by an increase in the last 0.35 Ma. These findings provide new insights into ocean circulation changes in the Indo-Pacific Sector of the Southern Ocean during the Mid-Pleistocene and Mid-Brunhes Transitions.

These three projects represent just a fraction of the outcomes from more than 100 CORE-funded studies, totaling nearly $2 million in grants. Collectively, these initiatives demonstrate the diverse scientific potential of archived materials and reinforce the enduring legacy of the JOIDES Resolution.

The CORE grant is particularly valuable for early-career researchers (ECRs) and students, offering them an opportunity to conduct meaningful research without requiring extensive sea-time. By leveraging the extensive archives of IODP’s sub-seafloor samples, recipients are addressing globally significant questions, advancing our understanding of Earth's processes, and developing critical research skills.

*ANZIC: Australian & New Zealand International Scientific Drilling Consortium

How to cite: Kachovich, S., Lawler, K.-A., and Hackney, R.: DNA to deep time: micropaleontology examples from the ANZIC Continent and Ocean Research & Education (CORE) grant scheme unlocking the secrets of ocean archives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7863, https://doi.org/10.5194/egusphere-egu25-7863, 2025.

Deep-water agglutinated foraminifera (DWAF) are crucial tools for paleoenvironmental analysis and biostratigraphic correlation in deep marine environments below the carbonate compensation depth (CCD). This study investigates the DWAF acmes in the Paleocene–Eocene sediments of IODP Hole U1511B, which was collected from the Tasman Abyssal Plain during Expedition 371. Cosmopolitan taxa, which have been previously documented from regions such as the Carpathians, Boreal North Atlantic, and Western Tethys, dominate the assemblages, which consist of 89 species across 43 genera. The identified acmes—Rzehakina, Spiroplectammina, Reticulophragmium, Trochammina, ammodiscids, and Karrerulina—display remarkable similarities to previously recognized events in the western Tethys and North Atlantic. The stratigraphy of Site U1511B exhibits a coarsening-upward sequence of greenish-gray Paleocene claystones that transition into reddish-brown Eocene sediments. The Paleocene/Eocene boundary is delineated by a hiatus. These acmes are associated with periods of ecological instability, such as the Paleocene–Eocene Thermal Maximum (PETM) and Early Eocene Climatic Optimum (EECO), which are indicative of changes in sedimentary regimes, oxygenation, and trophic conditions. The global extent of these faunal responses to climatic and oceanographic changes is illustrated by the observed DWAF successions, which align closely with acmes from the Western Tethys, Polish Carpathians, and Boreal North Atlantic, despite the semi-isolated position of the Tasman Sea during the Paleogene. The utility of DWAF as biostratigraphic indicators in abyssal environments devoid of calcareous fossils is emphasized by the presence of well-known acmes, including Rzehakina fissistomata and Spiroplectammina spectabilis. This research supports the hypothesis that DWAF acmes are triggered by substantial paleoenvironmental changes, such as global oligotrophy, sediment flux fluctuations, and organic matter redistribution during significant climatic events. The discovery of these acmes at Site U1511B contributes to the refinement of the Paleocene–Eocene stratigraphic framework in the abyssal ocean and the advancement of our understanding of global paleoceanographic events during the Paleogene.

How to cite: Korin, A., Hikmahitar, S., Alegret, L., Waskowska, A., and Kaminski, M.: Paleocene to Eocene Deep-Water Agglutinated Foraminiferal Acmes: A Global Perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8334, https://doi.org/10.5194/egusphere-egu25-8334, 2025.

Hydrological restriction from the Atlantic Ocean transformed the Mediterranean Sea into a giant saline basin during the Messinian Salinity Crisis (5.97 – 5.33 million years ago). It is still unclear if the deposition of nearly one million km³ of evaporite salts during this event was triggered by a major (≥ 1 km) evaporative drawdown, or if it took place in a brine-filled Mediterranean connected to the Atlantic. Here we present evidence for a two-phase accumulation of the Mediterranean salt layer based on the chlorine stable isotope composition of halite. During the first phase, lasting approximately 35 kyr, halite deposition occurred only in the eastern Mediterranean, triggered by the restriction of Mediterranean outflow to the Atlantic, in an otherwise brine-filled Mediterranean basin. During the second phase, halite accumulation occurred across the entire Mediterranean, driven by a rapid (< 10 kyr) evaporative drawdown event during which sea-level dropped 1.7-2.1 km and ~0.85 km in the eastern and western Mediterranean, respectively. During this extreme drawdown event, the eastern Mediterranean basin lost up to 83% of its water volume, and large parts of its margins were desiccated, while its deep Ionian and Herodotus sub-basins remained filled with > 1 km-deep brine.

How to cite: Aloisi, G., Moneron, J., Guibourdenche, L., Camerlenghi, A., Gavrieli, I., Bardoux, G., Agrinier, P., Ebner, R., and Gvirtzman, Z.: Chlorine isotopes constrain a major drawdown of the Mediterranean Sea during the Messinian Salinity Crisis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12427, https://doi.org/10.5194/egusphere-egu25-12427, 2025.

The Messinian Salinity Crisis (MSC) resulted in the generation of the last “Salt Giant” on Earth and was one of the biggest ecological crises in recent geological history. Given the large volume of data collected, and the high-resolution of the astronomically tuned and dated sedimentary successions, the MSC offers a unique opportunity to study the effect of short-term environmental variability and its impact on biological communities, particularly the resilience of microbial communities. The late Miocene Sorbas basin in south-western Spain hosts one of the most complete records of the MSC and has been used as a reference for astronomical tuning. However, in the absence of sedimentological and micropaleontological data from the shaly pre-evaporitic successions, it is hard to understand the impact of the extreme salinities, anoxia, and desiccation on the aquatic biosphere and on water conditions (i.e. temperatures, salinities and stratification). In this study, new constraints have been derived from the analyses of organic debris in shales from both pre- and inter-evaporitic deposits from a new 176,5-m drill core section in the Sorbas basin.

Our results from the analysis of the pre-evaporitic Abad formation and the black shales of the Yesares member, deposited in the inter-evaporitic cycles, reveal differences in biomarker-composition that can be related to changes in water conditions before and after the onset of the MSC. Squalane, framboidal pyrite, and sulphur reducing bacteria in the Abad formation suggest the presence of oxygen-restricted and saline waters before the precipitation of primary gypsum. After the establishment of hypersaline conditions (i.e. gypsum precipitation), a new phase of anoxia developed in the basin with the precipitation of marls and organic-rich laminites in the first inter-evaporitic eventof the Yesares member. Here the presence of isorenieratene-derivatives in the form of aryl isoprenoids can be interpreted as evidence of green sulphur bacteria. These bacteria use sulfur as an electron donor under anoxic conditions and perform photosynthesis underlow-light conditions, meaning that anoxia at this time extended up to the photic zone (<200m). Our data suggest that if a chemocline was present before gypsum precipitation it was weaker and perturbed by seasonal variation, while the chemocline was more stable during the inter-evaporitic stage.

How to cite: Schito, A., Sierra Ramirez, N., Bowden, S., Gibert Beotas, L., and Gomez Rivas, E.: Organic geochemistry as a proxy for unravelling water’s conditions in the Messinian succession of the Sorbas basin (Spain), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12863, https://doi.org/10.5194/egusphere-egu25-12863, 2025.

Maria Bianca Cita has often been called the Lady of the abyss, or the Lady of the Mediterranean. Passionate, determined, self-confident and respected in the world, Maria Bianca was a trailblazer in the disciplines of stratigraphy, micropaleontology and marine geology in Italy and internationally.

She began her research activity with a free teaching position in Geology in 1955 at the University of Milano, and later she approached stratigraphy and micropaleontology when these disciplines where under rapid evolution, in particular studying planktonic foraminifera of Mesozoic and Cenozoic formations.  She became the first in Italy to face the problems of the Cretaceous/Paleogene boundary as early as the mid 1950s. Her studies introduced the applicability of planktonic foraminiferal zonation, established in Trinidad in 1957, to the Italian and Mediterranean area, a premise that led this zonation to become the stratigraphic worldwide "standard" for the Cretaceous - Recent interval.

In the late 1960s, she became involved in scientific ocean drilling aboard the Glomar Challenger for the Deep Sea Drilling Project (DSDP), sensing that this project would revolutionize our knowledge of the history of our planet. If the Italian scientific community has had and has today the privilege to participate in scientific ocean drilling programs, it owes it largely to Maria Bianca Cita, who successfully brought Italy to the Ocean Drilling Program (ODP) in 1986.

In Italy, aboard the CNR oceanographic vessel Bannock, her extraordinary intuition for geology led to a series of scientific discoveries. These include the Eastern Mediterranean anoxic basins, discovered in a 1984 expedition that generated dozens of studies and publications all over the world, the mud volcanoes then studied and drilled for decades, the 'Homogenite' megaturbidite attributed to the Minoan eruption of Santorini (hypothesis later revised, but all observations and deposition models remained hers). An incubator of lines of research that have spread globally.

The greatest scientific challenge for Maria Bianca Cita was the formulation of the theory of the desiccation of the Mediterranean Sea during the long-known Messinian salinity crisis, which according to her and co-authors Bill Ryan and Ken Hsü had involved two extraordinary processes that, although still debated, have been successively supported by a host of multidisciplinary evidence: 1) that the level of the Mediterranean dropped well below the eustatic variations during the evaporitic phase,  and 2) that the end of the salinity crisis occurred due to a mega-flood in Gibraltar. A theory that has left its mark on the scientific community, on future generations of researchers, and on public opinion.

Those who shared research in the laboratory, cruises, participation in scientific meetings, and teaching wish to remember her attitude, made of commitment, curiosity, openness and a staunch dedication to pass these values on to younger generations.

How to cite: Camerlenghi, A., Erba, E., Malinverno, A., Premoli Silva, I., and Aloisi, G.: Maria Bianca Cita, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12903, https://doi.org/10.5194/egusphere-egu25-12903, 2025.

In recent years, there has been an increasing number of studies describing significant disturbances of the global carbon cycle during the latest Cretaceous. One example of these disturbances is the Mid-Maastrichtian Event (MME), which was likely related to changes in deep ocean circulation, particularly in the Atlantic realm.

To track and characterize the influence of the MME in deep-water environments in the equatorial South American margin, we conducted micropaleontological (benthic foraminifers) and geochemical analyses of sediments from Ocean Drilling Program (ODP) Site 1258 (Demerara Rise, offshore Suriname). Both geochemical tracers and benthic foraminiferal assemblages suggest the occurrence of paleoenvironmental reorganizations during the entire Maastrichtian, related to changes of intermediate to deep-water oxygenation and surface productivity. Benthic foraminiferal assemblages, characterized by typical deep-sea taxa (Aragonia, Nuttallides truempyi, Coryphostoma, Strictocostella, among others), indicate suboxic bottom water conditions with some oxygenation pulses, which correlate with changes in elemental ratios of redox-sensitive trace metals (Ni/Al, Cu/Al). Sediment elemental ratios (log(Fe/Ca), Si/Ti, Fe/K) indicate fluctuations in the silica and carbonate export via surface productivity, and a probable hydroclimate disturbance since the early Maastrichtian. During the MME, three phases of environmental evolution occurred: (1) high surface productivity and reduced bottom water oxygenation during subinterval MME1, (2) moderate surface productivity and increased bottom water oxygenation in subinterval MME2, and (3) recovery in surface productivity, suboxic conditions in the deep-sea, and more humid conditions during subinterval MME3. These paleoenvironmental disturbances were probably caused by increased influence of high-latitude deep-waters (North Atlantic source instead of the Southern Ocean) on low latitudes, which likely influenced latitudinal migrations of the Paleo-Intertropical Convergence Zone.  

How to cite: Patarroyo, G., Kochhann, K., Alegret, L., and Fauth, G.: Benthic foraminifera and paleoenvironmental turnover across the mid-Maastrichtian event in the Tropical Atlantic Ocean (ODP Site 1258), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14451, https://doi.org/10.5194/egusphere-egu25-14451, 2025.

Deep-sea hypersaline anoxic basins (DHABs) in the Mediterranean Sea are extreme environments shaped by the interplay of salt tectonics and sedimentary processes over geological time scales. The foundational work of Maria Bianca Cita, who first provided evidence of the Messinian Salinity Crisis and contributed to the discovery of Mediterranean DHABs, has profoundly influenced our understanding of these unique settings. Her research revealed the dramatic environmental shifts that shaped the Mediterranean, laying the groundwork for investigating the relationship between salt tectonics and hypersaline basins.

Currently, eight main DHABs are recognized in the eastern Mediterranean, but a comprehensive geomorphological characterization of these features and their surrounding regions remains lacking. The seafloor in these areas is often described as exhibiting a "cobblestone topography," reflecting the complex terrain generated by salt tectonic deformation. However, high-resolution multibeam surveys from recent studies reveal a significant diversity of landforms that could characterize hundreds of square kilometers in the eastern Mediterranean Basin.

Using data collected during recent European-funded research cruises in the Mediterranean, we conducted a detailed geomorphometric analysis to better characterize the salt-tectonic-associated landforms mapped in the Levantine Basin. Our results confirm spatial patterns reflecting the influence of tectonic forces and sedimentary dynamics in shaping the DHABs, consistent with previous studies, while also unveiling a broader variety of submarine landforms associated with salt tectonics. This study highlights an underestimated ecological and environmental variability in the extreme environments of the deep Mediterranean. By focusing on these underexplored morphologies, we honor the legacy of Maria Bianca Cita and deepen our understanding of the unique ecosystems and geological processes that define the Mediterranean deep sea.

How to cite: Tessarolo, C., Savini, A., De Lange, G., and Corselli, C.: Salt Tectonics and Hypersaline Anoxic Basins: Processes and Forms Shaping Significant Extreme Environments in The Mediterranean Sea, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15434, https://doi.org/10.5194/egusphere-egu25-15434, 2025.

Benthic foraminiferal studies from the Cretaceous of Australia provide critical insights into paleoenvironmental and biostratigraphic correlations across the Southern Hemisphere. This study contextualizes data from International Ocean Discovery Programme (IODP) Sites U1512, U1513, U1514 and U1516 , and significant data from other sources. We present the significance of calcareous and agglutinated benthic foraminiferal data for our understanding of palaeoenvironmental dynamics in the mid- to Upper Cretaceous sediments of the southern hemisphere, relying on complementary data from planktonic foraminifera as well as calcareous nannofossils.
In the Albian, the benthic foraminiferal record at Site U1513 illustrates transitions from neritic to upper bathyal environments, initially marked by the dominance of agglutinated taxa such as Ammodiscus and Haplophragmoides. The shift to calcareous benthic foraminifera, including the markers Gavelinella intermedia and Osangularia schloenbachi, reflects increasing marine influence. These assemblages correlate with records from the Kerguelen Plateau, the Great Artesian Basin, and South America, providing a coherent framework for Southern Hemisphere biostratigraphy during the Albian.
The Cenomanian-Turonian interval captures the impact of Oceanic Anoxic Event 2 (OAE 2). At Sites U1513, U1516, and U1512, a reduced diversity in calcareous benthic foraminifera and the increased dominance of agglutinated taxa highlights the environmental stress linked to dysoxic conditions. These changes are mirrored across the Southern Hemisphere, with parallels in South Africa and Walvis Ridge.
The Coniacian and Santonian successions at Site U1513 document stable bathyal environments dominated by calcareous benthic taxa such as Gavelinella berthelini and Notoplanulina rakauroana. These assemblages exhibit remarkable correlations with other Southern Hemisphere records, including the Falkland Plateau and New Zealand. This synthesis underscores the significance of calcareous and agglutinated benthic foraminifera for correlations through the Southern Hemisphere and helps to improve our understanding of the interplay between local and global paleoenvironmental dynamics, and oceanographic and climatic developments during the Cretaceous. 

How to cite: Wolfgring, E., Amaglio, G., Kaminski, M., Petrizzo, M. R., and Watkins, D.: The significance of Benthic Foraminiferal Deep-Sea Drilling data in the Cretaceous Austral Realm, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15698, https://doi.org/10.5194/egusphere-egu25-15698, 2025.

Understanding abrupt environmental changes, including those caused by the rapidly warming oceans, requires a compilation of paleoenvironmental data obtained from marine sedimentary archives, such as Ocean Drilling Program (ODP) cores. Dinoflagellate cysts serve as sensitive and reliable indicators of past environments, and their application has gained prominence over the last decades, especially for high-resolution studies in the northeastern Pacific Ocean. Dinoflagellates are one of the most diverse and abundant groups of microalgae in coastal environments and are major primary producers. Many dinoflagellates form highly resistant organic-walled resting cysts that accumulate in sediments throughout their life cycle. The records of these microfossils provide valuable information about upper water masses at the time of cyst deposition.

In this presentation, we summarize insights gained from two high-resolution dinoflagellate cyst sedimentary records — one from the California Margin (ODP Hole 1017E) and the other one from the Santa Barbara Basin (SBB; ODP Hole 893A). Census data of cysts from the Holocene and the Last Interglacial (Over and Pospelova, 2022) enable us to identify shifts in ecosystems responding to climate change. These data were used for quantitative and qualitative reconstructions of past sea-surface temperatures, salinity, primary productivity, and potentially significant forest fires during the warm Dansgaard-Oeschger interstadial event 2 (~23,000 years ago).

How to cite: Pospelova, V., Bringué, M., and Mertens, K. N.: Late Quaternary dinoflagellate cysts record abrupt climate changes along the California margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15868, https://doi.org/10.5194/egusphere-egu25-15868, 2025.

Abundances and assemblage composition of benthic foraminiferal, dinoflagellate cysts and pollen were analysed together with sedimentological and geochemical proxies to investigate paleoenvironmental changes recorded in the Gulf of Corinth during MIS 1-5. The Gulf of Corinth is a relatively young (<5 Ma) and active continental rift zone in the eastern Mediterranean Sea, currently connected to the Ionian Sea through a shallow sill (60 m of depth) and to the Aegean Sea via the Corinth Canal (Isthmus; 6 km-wide). The coring sites of the IODP Expedition 381 are located in the central part of the gulf and the Alkyonides Gulf, a shallow semi-enclosed sub-basin within the northeastern part of the Gulf of Corinth. The closed drainage system and the high sedimentation rates make the study area ideal for investigating the complex interactions between sedimentary input, tectonics and climate through the basin’s evolution.

The benthic foraminiferal, dinocyst and pollen records are highly variable during both the Last Interglacial Complex and the Holocene. Mesotrophic to eutrophic marine conditions prevailed, as indicated by the high abundance of infaunal foraminiferal species (Bolivina spp., Melonis affinis, Bulimina spp., Cassidulina carinata, Valvulineria bradyana), with marine dinocysts (Nemaosphaeropsis labyrinthus, Spinifireties ramosus) and montane trees likely occurring during high sea-levels. During glacial and interstadial intervals, benthic foraminifers are mostly absent whereas abundant brackish dinocysts (Pyxidinopsis psilata) indicate a sea-level drop below sill level and the subsequent (semi-)isolation of the basin. Steppic pollen taxa predominate during the same intervals. Inorganic carbon content and elemental values varied following the inferred sea-level fluctuations, as well as the benthic foraminiferal oxygen isotope record which is discontinuous and conditionally limited to the presence of well-preserved benthic foraminifera. The beginning of the Holocene is marked by the re-establishment of marine conditions as the sea-level rose above the sill and the basin re-connected with the Mediterranean Sea.

This study is funded through projects GR 5285/3-1 “Late Quaternary dynamics of marine paleoenvironments and ecosystems in the Gulf of Corinth (eastern Mediterranean)” and PA 2664/8-1 “Linking marine and terrestrial ecosystem responses to climate variability since the Last interglacial in the Eastern Mediterranean” of the Deutsche Forschungsgemeinschaft (DFG).

How to cite: Koukousioura, O., Panagiotopoulos, K., Fatourou, E., Kafetzidou, A., Diz, P., Kouli, K., and Grunert, P.: Paleoenvironmental changes during MIS 1-5 in the Gulf of Corinth (eastern Mediterranean): IODP Expedition 381, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18087, https://doi.org/10.5194/egusphere-egu25-18087, 2025.

Convergence between African and European plates generates compressional strain, primarily concentrated along the northern African margin. This is testified on the Algerian margin by numerous earthquakes (e.g. Bougrine et al., 2019) and by the presence of active folds and thrusts. Multi-channel seismic reflection profiles from the MARADJA I survey reveal north-verging thrusts rooted below the Messinian units, and the geometries of the Messinian salt structures. This study examines the characteristics o+ salt tectonics offshore Algiers and Dellys, focusing on the effect of the positive structural inversion of the former passive margin on geometries, timing, and mechanisms o+ salt deformation. The interpretation of seismic refection and multi-beam bathymetric data of the MARADJA I survey, along with its comparison with analogue models, allowed us to reconstruct the salt tectonics processes on the margin and to identify the predominant role of a plateau uplift on salt deformation. Early and ubiquitous salt deformation by downbuilding was followed by a major phase of plateau uplift (end of Messinian Crisis), leading to westward gravity gliding and a slowdown of the salt deformation above the plateau. Km-tall salt structures were developed and thick minibasins deposited. Salt tectonics is nowadays active only where the relationship between salt and overburden thickness is favorable.

How to cite: Travan, G., Gaullier, V., Déverchère, J., and Vendeville, B.: Interplay of positive structural inversion and salt tectonics: The case study of the central Algerian margin, Western Mediterranean, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20036, https://doi.org/10.5194/egusphere-egu25-20036, 2025.

The Fram Strait gateway connecting the North Atlantic and Arctic Oceans is an area of high importance for understanding relationships between ocean currents and ice sheet dynamics during past climate transitions; such information is valuable for informing predictive models of future global change. IODP Expedition 403 was motivated by the necessity of retrieving continuous, high-resolution depositional sequences containing the record of the paleoceanographic characteristics of the warm, northward flowing West Spitsbergen Current (WSC) and the cryosphere evolution of the paleo-Svalbard Barents Sea Ice Sheet (SBSIS). Over 5.3 km of sediment records were recovered by drilling 7 sites located along the (S to N) pathway of the WSC, and at (E to W) proximal to distal settings relative to the paleo-SBSIS terminus. The initial age models based on paleomagnetic reversals and microfossils indicate the recovery of expanded Pleistocene and Pliocene sequences in the paleo-SBSIS proximal zone, and in the more distal setting, with recovery of 600+ m sequences that extend into to the mid-Pliocene and the early Pliocene/late Miocene. Preliminary comparisons between lithologies and well-established lithofacies from shallow piston cores of the western Svalbard margin, suggest that the Exp403 site records can be used to constrain the history of shelf edge glaciation, paleo-meltwater events, iceberg calving events, and warm periods dominated by persistent bottom water flow. Physical properties data support this tentative conclusion and suggest that orbital patterns and marine isotope stages (MIS) can be depicted in the records from all site locations despite the diagenetic overprint that complicates the identification of primary depositional signals and stratigraphy. We report also about the challenges faced during Exp-403, the last expedition of the RV JOIDES Resolution under the historical ODP/IODP international program.

How to cite: Lucchi, R. G., St John, K. K., and Ronge, T. A. and the IODP Exp-403 Science Party: IODP Expedition 403, Eastern Fram Strait Paleo-Archive: challenges and achievements of the last IODP expedition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-326, https://doi.org/10.5194/egusphere-egu25-326, 2025.

International Ocean Discovery Program (IODP) Expedition 395 recovered near-continuous sedimentary records from several major contourite drift bodies in the North Atlantic Ocean. These drifts deposits are influenced by deep-water currents, and studying their composition can inform us on past changes in ocean circulation. Drift sedimentation is a dynamic process that can lead to spatial variation in deposition and preservation through time. Here, we correlate on a glacial-interglacial timescale new IODP Expedition 395 records with Ocean Drilling Program (ODP) records previously cored nearby to assess the degree of variability between sites on the same drift body. We correlate IODP Site U1554 with ODP Site 984 for Björn Drift, and IODP Site U1564 with ODP Site 983 for Gardar Drift. Variations in magnetic susceptibility measured on sediment cores show striking resemblances between the paired sites. The clearly expressed glacial-interglacial scale variability enables astronomical tuning of the records. Furthermore, we explore the possibility of using multiple volcanic ash layers as additional markers for stratigraphic correlation. This work will contribute to the construction of high-resolution age models for the Expedition 395 records, as well as to a better understanding of the evolution of Björn and Gardar Drifts through space and time.

How to cite: Sinnesael, M., Irwin, R., Magzoub, A., Parnell-Turner, R., Briais, A., and LeVay, L. and the Expedition 395 Scientists: Plio-Pleistocene Glacial-Interglacial Climate Variability as Recorded in the North-Atlantic Björn and Gardar Drift Sediments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2373, https://doi.org/10.5194/egusphere-egu25-2373, 2025.

Located in the heart of the Tibetan Plateau, Nam Co is a closed lake spanning over 2,000 square kilometers and situated at an elevation exceeding 4,700 meters. The sediment thickness within the lake exceeds 700 meters, providing comprehensive insights into the climate and environmental conditions covering several glacial and interglacial cycles. With the support of the International Continental Scientific Drilling Program (ICDP) and China's Second Tibet Integrated Expedition Project (STEP), the Namcore drilling project aims to achieve: (1) Reconstructing the long-term climate change history across multiple glacial-interglacial stages and elucidating its relationship with global atmospheric circulation patterns; (2) Investigating the evolution and resilience of high-altitude terrestrial and lacustrine ecosystems under glacial and interglacial climate conditions; (3) Understanding the metabolic factors influencing lake sediment microbial communities in various glacial-interglacial environments; (4) Providing fundamental observation data on paleomagnetic changes to simulate the paleomagnetic field prior to the Holocene epoch. Depending on a stable and wind-resistant drilling barge manufactured in China, and a skilled drilling team as well as the long-term used drilling equipment provided by ICDP, the field campaign was successfully conducted from June 6 to July 17 of 2024, resulting in the retrieval of a total length of 950 meters of lake core. The deepest depth reached by the drill exceeded 510 meters. Based on seismic survey data, it is anticipated that the age of the lake core surpasses MIS 13 stage (approximately 550,000 yrs BP). Furthermore, the average resolution achieved is as high as 10 yrs cm^-1. A combination of multiple dating methods will be employed in order to establish a robust deposition time series. ¹⁴C will be utilized for sediments less than 50,000 yrs BP while OSL and post-IR IRSL method will be employed to date back approximately 200,000 yrs BP. For more older deposits, amino acid racemization (AAR), uranium/thorium ratio (U/Th), cosmic ray Beryllium isotope (¹⁰Be/⁹Be), as well as geomagnetic polarity analysis, thermochronology assessment and cyclic stratigraphy will be integrated to obtain reliable chronological sequences of cores. Proxies will be utilized to indicate climate and environmental changes, such as geochemical indicators, pollen, biomarkers, sedaDNA, environmental magnetic indicators, etc. for reconstructing paleo-temperature, precipitation, water level, vegetation, aquatic biodiversity and other changes in the lake basin. The relationship between these changes and atmospheric circulation changes and glacial activities in the lake basins will be also discussed.

How to cite: Zhu, L., Haberzettl, T., Wang, J., Vogel, H., Clarke, L., Henderson, A., Spiess, V., Ju, J., and Adolph, M.-L.: An over 500,000 years lacustrine core in the high-altitude lake Nam Co of the Tibet Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4722, https://doi.org/10.5194/egusphere-egu25-4722, 2025.

Orbital forcing may be preserved as cyclical variation in acoustic impedance in marine sediments due to paleoclimate-related changes in grain size, sorting and lithology. If seismic images of such deposits have the relevant bandwidth, this cyclicity may be imaged as distinct peaks in the power spectra of the seismic traces. In principle this could allow the application of cyclostratigraphic techniques to seismic data. It is still unclear, however, if in practice the statistical power is high enough to reliably discriminate orbital cyclicity from seismic data alone, and how the false detection rate compares to directly sampled data such as outcrop, drill core or borehole logs.

In this study we compare the discriminatory power for cyclostratigraphic analyses between seismic data and an equivalent borehole log. We develop a method for spectral background estimation that accounts for some of the amplitude and frequency filtering effects inherent to seismic data. We forward model the seismic response using 1-D visco-acoustic full-wavefield seismic modelling that includes the contribution of multiples and seismic absorption, which we combine with Monte Carlo ensemble modelling using sedimentary noise models to quantify the discriminatory power of both seismic and borehole significance testing approaches.

We demonstrate this on two examples: i) a simplified model with constant background velocity, sedimentation rate and known seismic source wavelet, and ii) a real-world example based on ODP Site 1084 (Cape Basin, ODP Leg 175). We observe in both cases that the sensitivity and specificity (related to the true and false detection rates) for the seismic case are strongly dependent on the spectral frequency, compared to the largely frequency-independent results for the borehole cyclostratigraphy. For the ODP Site 1084 example we observe a seismic spectral peak corresponding to 95 kyr eccentricity with an uncalibrated confidence level of >95%. Our Monte Carlo ensemble modelling, however, shows that the false positive rate at this frequency and confidence level is around 25%, compared to around 5% for the equivalent borehole cyclostratigraphy. We also demonstrate eccentricity modulation and bundling analysis (TimeOpt) applied to the seismic data, which can successfully invert for the sedimentation rate for the simplified seismic synthetic example.

Our results suggest that reliably identifying Milanković cyclicity from seismic data is possible but is strongly dependent on the sedimentation rate, the geophysical properties of the subsurface and the spectral frequency in question. Where the age model is known (i.e., from a co-located borehole) and an orbital signal is well-preserved in the acoustic impedance, for typical airgun seismic bandwidths, sedimentation rates around 20 cm ka^-1 and seismic velocities around 1600 ms^-1 it should be generally possible to identify eccentricity and obliquity cyclicity in seismic data. This opens the door to widespread use of seismic cyclostratigraphy to identify the preservation of cyclicity directly from seismic data, to extrapolate astronomically-tuned age models away from (and below) boreholes and to screen for the preservation of cyclicity prior to drilling. Similar principles could be applied to other methods such as sub-bottom profilers to identify, for example, higher frequency precessional cyclicity.

How to cite: Ford, J., Camerlenghi, A., Rebesco, M., Uenzelmann-Neben, G., and Weigelt, E.: Seismic cyclostratigraphy: hypothesis testing for orbital cyclicity at ODP Site 1084 using seismic reflection data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6556, https://doi.org/10.5194/egusphere-egu25-6556, 2025.

The West Antarctic Ice Sheet (WAIS) is currently experiencing accelerated mass loss. It contains enough ice to raise global sea levels by up to five meters if completely melted. Yet we do not know under which environmental conditions a total collapse will occur.

Here we present an overview of the SWAIS2C (Sensivity of the West Antarctic Ice Sheet to 2 Degrees Celsius of Warming)  project. The project aims to unravel past and present factors influencing WAIS dynamics and to reconstruct WAIS response to warmer temperatures, including those exceeding the +2°C target outlined in the Paris Climate Agreement. SWAIS2C (ICDP project 5072) targets two sites, chosen to obtain geological data close to the centre of the WAIS to improve model-based projections of future sea level contributions from Antarctica. The first site is close to the grounding line of the Kamb Ice Stream site (KIS3) and sensitive to ocean forcing of ice shelf and ice sheet collapse. The second site on the Crary Ice Rise (CIR) demarks a pinning point of the ice shelf and offers a complementary view on processes that can (de)stabilise the WAIS. Data obtained at these sites will enable us to answer the overarching question under which climatic conditions we will lose the WAIS.

 In the first two field seasons of the SWAIS2C project in 2023/24 and 2024/25, equipment was traversed more than 800 km across the Ross Ice Shelf to the remote KIS3 field site. Hot water drilling was successfully completed in both years and penetrated ~580 m of ice to provide access to the 55 m deep ocean cavity and seafloor beneath. Oceanographic measurements were made beneath the ice shelf,  videos of the seafloor and ice shelf were recorded, and a long-term oceanographic mooring was installed. Gravity and hammer coring during both seasons yielded a total of 9.5 m of unconsolidated diamict sediment, including the longest sediment core from the Siple Cost, measuring 1.92 m. All of the cored material was x-rayed in the field. During each drilling season, one or two cores were extruded in a sterile environment and sampled for microbiology, geochemistry, pore water or ancient DNA work.

Deep drilling was attempted in both years using the Antarctic Intermediate Depth Drill (AIDD). In our first season, Glass Reinforced Epoxy (GRE) formed part of our sea riser. It was chosen for its light weight and thermal properties, but deployment proved challenging. In our second season, we replaced the GRE sea riser with HRQ steel pipe. We successfully lowered the sea riser to the sea floor, which marked a major project milestone. After deploying 450 m of NQ drill string inside the riser, we had to call off operations, just a couple of hours short of retrieving our first sediment core. Our next drilling attempt will be at Crary Ice Rise in 2025/26, where we hope to recover 200 m of sediment core, and perform a range of geophysical surveys.

Deep field work in Antarctica is challenging, but the questions we are trying to answer for humanity are worth it.

How to cite: van de Flierdt, T., Levy, R., Dunbar, G., Horgan, H., Kulhanek, D., Patterson, M., and SWAIS2C Science Team, T.: Sensivity of the West Antarctic Ice Sheet to 2° Celsius of Warming. The SWAIS2C project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7417, https://doi.org/10.5194/egusphere-egu25-7417, 2025.

The early Paleogene represents a greenhouse Earth experiencing large-scale global environmental changes after the Cretaceous-Paleogene extinction. Understanding climate and ocean dynamics during this recovery phase is challenging due to the scarcity of continuous, carbonate-rich sedimentary records. The Paleocene interval of International Ocean Discovery Program−International Continental Scientific Drilling Program (IODP-ICDP) Site M0077 from within the Chicxulub crater provides such an archive. Sequence and cyclostratigraphic analyses reveal condensed and rhythmic bedding, transitioning between marl or argillaceous wackestone and foraminiferal packstones. These 5−33-cm-thick cycles document low-amplitude sea-level changes or local environmental shifts in the Chicxulub basin associated with sea level. The cycles exhibit retrogradational, progradational, or aggradational facies stacking patterns, indicative of transgressive, highstand, and shelf margin systems tracts. Progradational packages align with global sea-level events, suggesting a eustatic driver. Cyclostratigraphy on the sediments’ color reflectance reveals 10 cm and 20 cm periodicities, interpreted as 41 k.y. obliquity and 100 k.y. eccentricity signatures. These climate-driven cycles resemble Paleogene hyperthermals, intensifying the hydrologic cycle and erosion of fine-grained siliciclastic sediments in the Chicxulub hinterland. Thereby, hyperthermals correspond to marl or argillaceous wackestone facies. Moreover, sequence boundaries tend to correspond to minima in the 1.2 m.y. obliquity modulation cycle. This longer-term astronomical control on sea level and climate offers insights into potential drivers of eustatic sea-level change in the Paleocene greenhouse world. The phase relationship between sea level and the 1.2 m.y. obliquity cycle indicates increased water storage in continental reservoirs during periods of astronomically suppressed seasonality (i.e., 1.2 m.y. obliquity minima). Thus, the carbonate sedimentological study of the Paleocene Chicxulub sequences provides unique insights into both local and global environmental dynamics.

How to cite: De Vleeschouwer, D., O’Malley, K., Lowery, C. M., Gulick, S. P. S., and Whalen, M. T.: Sequence and cyclostratigraphic analysis of Paleocene carbonate sediments in the Chicxulub impact crater: Implications for sea level change and climate dynamics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7975, https://doi.org/10.5194/egusphere-egu25-7975, 2025.

Based on site-survey work during research expedition M183 (2022), the sea floor drill rig MARUM-MeBo70 was deployed in summer 2023 on the research vessel MARIA S. MERIAN (MSM119) in order to install observatories for the investigation of hydrothermal circulation in young oceanic crust. In-situ heat flow and fluid chemistry had inferred crustal fluid circulation along the ridge flank. The expedition went to the southernmost tip of Reykjanes Ridge – a part of the Mid-Atlantic Ridge. We were able to set two pairs of observatories in 1500 and 1700 m water depth, respectively. At each site two holes with 103 mm diameter were drilled through a 5 to 30 m sediment cover and an additional 5 to 13 m into the underlying ocean crust. The drill string was lifted by one drill pipe before a last prepared rod – the observatory rod - was screwed onto the drill string. The observatory rod sealed the drill pipe from sea water and was equipped with temperature sensors. One type – the injection observatory – also contained a system for releasing a tracer to the base of the borehole where it has contact to the fluid circulation system within the upper ocean crust. The second type – the monitoring observatory – was installed in a distance of a few tens of meters and contained an additional osmo-sampler for sampling the fluids from the upper crustal aquifer the base of the bore hole. The osmo-samplers will be recovered during an upcoming expedition in September 2025 (research expedition M213). This experiment will help to better understand the relevance of hydrothermal circulation in the flanks of ocean ridges for the exchange of elements and heat  between the ocean crust and the oceans. 

How to cite: Freudenthal, T., Achim, K., Markus, B., and Matthias, Z.: Installation of Borehole Observatories at Reykjanes Ridge with the sea floor drill rig MARUM-MeBo70, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8141, https://doi.org/10.5194/egusphere-egu25-8141, 2025.

The Permian witnessed some of the most profound climatic, biotic, and tectonic events in Earth’s history. Global orogeny leading to the assembly of Pangea culminated by middle Permian time, and included multiple orogenic belts in the equatorial Central Pangean Mountains, from the Variscan-Hercynian system in the East to the Ancestral Rocky Mountains in the West. Earth’s penultimate global icehouse peaked in early Permian time, transitioning to full greenhouse conditions by late Permian time, constituting the only example of icehouse collapse on a fully vegetated Earth. The Late Paleozoic Ice Age was the longest and most intense glaciation of the Phanerozoic. Reconstructions of atmospheric composition in the Permian record the lowest CO₂ and highest O₂ levels of the Phanerozoic, with average CO₂ levels comparable to the Quaternary, rapidly warming climate. Fundamental shifts occurred in atmospheric circulation: a global megamonsoon developed, and the tropics became anomalously arid with time. Extreme environments are well documented in the form of voluminous dust deposits, acid-saline lakes and groundwaters, extreme continental temperatures and aridity, and major shifts in biodiversity, ultimately culminating in the largest extinction of Earth history at the Permian-Triassic boundary.

The Deep Dust project seeks to elucidate paleoclimatic conditions and forcings through the Permian at temporal scales ranging from millennia to Milankovitch cycles and beyond by acquiring continuous core in continental lowlands known to harbor stratigraphically complete records dominated by loess and lacustrine strata. Our initial site is in the midcontinental U.S.— the Anadarko Basin (Oklahoma), which harbors a complete continental Permian section from western equatorial Pangaea. We will also address the nature and character of the modern and fossil microbial biosphere, the chemistry of saline lake waters and groundwaters, Mars-analog conditions, and exhumation histories of source regions. Importantly, data from Deep Dust will be integrated with Earth-system modelling. This is crucial for putting the (necessarily local) drill core data into the broader global context and for understanding relevant mechanisms and feedbacks of the Permian Earth system.

How to cite: Feulner, G., Soreghan, G. S., Bedle, H., Benison, K., Bourquin, S., Hamamura, N., Hinnov, L., Moscariello, A., Noren, A., Pfeifer, L., Ramezani, J., Spina, A., and Zeeden, C.: Deep Dust – An ICDP Drilling Project to Probe Continental Climate from the Late-Paleozoic  Icehouse to the end-Permian Hothouse, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8251, https://doi.org/10.5194/egusphere-egu25-8251, 2025.

The International Ocean Drilling Programme (IODP³)

After decades of unified international programmes, from DSDP to the International Ocean Discovery Program that ended on 30 September 2024, post-2024 scientific ocean drilling initiatives will see a transition from a single international programme operated by independent platform providers to independent ocean drilling programmes.

Through a two-year long process of exchange of views and ambitions, ECORD and Japan agreed to build a joint scientific ocean drilling programme: the International Ocean Drilling Programme - IODP³(IODP-cubed).

IODP³ consists of an international scientific collaboration addressing important questions in Earth, Ocean, Environmental and Life sciences described in the ‘2050 Science Framework: Exploring Earth by Scientific Ocean Drilling, based on the study of rock and/or sediment cores, borehole imaging, in-situ observatory data, and related geophysical imaging obtained from the subseafloor.

IODP³ will adopt a transparent, open, flexible, and international modus operandi, programme-wide standard policies and guidelines, sustainable management, and publicly accessible knowledge-based resources.

IODP³ will implement and fund two types of expeditions: offshore expeditions and Scientific Projects using Ocean Drilling ARChives (SPARCs).

Proposals supporting these expeditions will be submitted through a bottom-up process to the IODP³ Science Office by teams of proponents belonging to the international research community. All proposals will be evaluated by the Science Evaluation Panel (SEP) in a fair, open, and transparent manner, in terms of both scientific excellence and completeness and quality of the site characterization data packages. The Safety and Environment Advisory (SEA) Group will provide independent advice regarding potential safety and environmental issues associated with the proposed IODP³ drill sites.

IODP³ offshore expeditions and SPARCs will be scheduled by the MSP Facility Board (MSP-FB), based on their scientific merit and operational constraints within the limits of the available resources.

Offshore expeditions will be implemented by the IODP³ Operators, the ECORD Science Operator (ESO) and/or JAMSTEC-MarE3, following an expanded Mission Specific Platform (MSP) concept by diversifying drilling and coring technologies and applying them to all drilling environments, as determined by scientific priorities, operational efficiency, and better value for money. The duration of IODP³ expeditions will be flexible and be determined by scientific requirements and available funds.

Land-to-Sea Transects (L2S), requiring scientific drilling at both onshore and offshore sites to be implemented jointly with the International Scientific Continental Drilling Program (ICDP) are one of prime objectives for IODP³.

Scientific Projects using Ocean Drilling ARChives (SPARCs) are international and multidisciplinary projects that have objectives originating from or that are based on ocean drilling archives (i.e. cores, samples, and data from current and past scientific ocean drilling programmes) without new drilling or other operations at sea. Each SPARC will have a funded duration of three years and will receive €300,000 for its implementation.

How to cite: Camoin, G. and Eguchi, N.: The International Ocean Drilling Programme (IODP3), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9036, https://doi.org/10.5194/egusphere-egu25-9036, 2025.

To advance the next generation of astronomical solutions, there is a need to establish constraints on the Earth-Moon distance and the related precession and obliquity parameters throughout Earth's history. These constraints can be derived by extracting precise precession and/or obliquity signals from geological records. The recently drilled ICDP BASE cores from the Moodies Group in the Barberton Greenstone Belt (South Africa) provide a unique opportunity to determine an Earth-Moon distance datapoint at 3.2 Ga using cyclostratigraphy. In this study, we present initial cyclostratigraphic results from BASE Site 5A, which represents a relatively deeper and quieter depositional environment with finer-grained sediments compared to other ICDP BASE drill sites. To detect a potential Milanković signal, we performed time-series analyses on a suite of elemental proxies obtained via XRF core scanning, tracing temporal changes in redox conditions and siliciclastic input.

BASE Site 5A reveals superimposed cycles of 4–6 meters and 30–50 meters, visible in both redox-sensitive elements and siliciclastic elemental proxies. However, interpreting this sedimentary cyclicity is challenging due to the absence of radio-isotopic age constraints at this site. Existing U-Pb ages from the Barberton Supergroup suggest extremely high sedimentation rates of approximately 25 to 1000 cm/kyr for the Moodies Group as a whole (Heubeck et al., 2013). Given that Site 5A was selected for its finer-grained sediments, its sedimentation rates may be on the lower end of this range. Additionally, variations in lithology, ranging from sandstones of varying grain sizes to jaspilites and siltstones, complicate sedimentation rate estimates and duration calculations for this interval. Nevertheless, preliminary evolutive time-series analyses (evolutive harmonic analysis, evolutive TimeOpt and eASM) suggest no significant sedimentation rate changes, except near the stratigraphic top of the record. Sedimentation rates estimated by these evolutive analyses range from 35 to 55 cm/kyr, corresponding to a total duration of 820–1300 kyr for the 450-meter-long Site 5A core. Based on these derived sedimentation rates, the 4–6-meter cycles could potentially correspond to precession, while the 30–50-meter cycles may reflect short ~100-kyr eccentricity cycles. However, we emphasize that these interpretations are preliminary and remain inconclusive. At this stage, these results provide only an indication of potential astronomical Milanković forcing, which will require thorough scrutiny against additional sedimentological and statistical analyses before an inference on Earth-Moon distance can be made.

Heubeck, C., Engelhardt, J., Byerly, G. R., Zeh, A., Sell, B., Luber, T., and Lowe, D. R.: Timing of deposition and deformation of the Moodies Group (Barberton Greenstone Belt, South Africa): Very-high-resolution of Archaean surface processes, Precambrian Research, 231, 236–262, https://doi.org/10.1016/j.precamres.2013.03.021, 2013.

How to cite: Wichern, N., Schreiber, D., Gugliotta, M., Heubeck, C., and De Vleeschouwer, D.: Decrypting Milanković-driven sedimentary rhythms in nearshore strata of the Archean Moodies Group, South Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9111, https://doi.org/10.5194/egusphere-egu25-9111, 2025.

With the conclusion of the International Ocean Discovery Program (IODP), the laboratories and instruments of the JOIDES Resolution (JR) are now operational in the newly renovated laboratory space of the Gulf Coast Repository (GCR) at Texas A&M University. The facility is available to academic researchers (U.S. and abroad), as well as commercial customers. This includes individual researchers, small and large research teams, and legacy projects such as Scientific Projects using Ocean Drilling ARChives (SPARCS). The instrumented facility can be used to make new measurements on the over 150 km of core housed at the GCR. Additionally, the facility can process new cores acquired by future scientific ocean drilling coring projects conducted from mission-specific platforms, on cores collected from other coring projects, and on discrete geologic samples. The instrumented GCR maintains an almost identical suite of analytical capabilities as those that were available on the JR. This includes multi-sensor loggers for measuring P-wave velocity, magnetic susceptibility, density, natural gamma ray counts, and color reflectance. Imaging and X-radiography loggers, a superconducting rock magnetometer, microscopes and SEM-EDS, as well as ICP-OES, CHNS, and XRD analysis are also available. The previous GCR instrumentation, including two XRF core scanners and a new hyperspectral scanner remain available. Other peripheral devices, such as a core splitter, allow for the processing of new cores. Workshops, educational and training exercises can also be held at the GCR. To provide long-term viability and equitable access to instrumentation, a user-fee model will support maintenance and repair of instruments and replacement of consumables. Combined with experienced technical and science staff, the instrumented GCR will facilitate new scientific ocean drilling research, training, and outreach opportunities in the onshore environment.

How to cite: Childress, L., Penkrot, M., Crowder, L., and Malone, M.: The Gulf Coast Repository: Instrumented Facility for Analysis of Scientific Ocean Drilling Cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10354, https://doi.org/10.5194/egusphere-egu25-10354, 2025.

The oceanic lithosphere cools as it spreads away from the mid-ocean ridges, and subducts into the mantle at the subduction zones. In the context of Earth’s material cycle, quantitative chemical and thermal state of the oceanic lithosphere is desired to be estimated to elucidate material flux into the mantle. As a step toward reconstructing the chemical and thermal state of oceanic lithosphere, we present geochemical data set of mantle xenoliths from petti-spots in the northwestern Pacific, where no seismic anomaly is imaged. The petit-spot-borne mantle xenoliths provide us unique chemical and thermal information avoiding modifications derived from the mantle plumes.

The petit-spot mantle xenoliths include lherzolites, harzburgites, and dunites collected at petit-spot Sites A and B in the northwestern Pacific, using deep-submergence vehicle Shinkai 6500 during four expeditions of YK05-06, YK20-14S, YK21-07S, and YK24-10S. They are small in size ranging from 1 to 5 cm in diameter, except for a lherzolite with 15 cm-long diameter. The peridotites show variation in terms of the presence of spinel and garnet, and degree of melt depletion. Some of the peridotites include fine-grained mineral aggregates, which are broken-down products after pyrope-rich garnets considering their average bulk chemical compositions. Rare-earth elements (REE) of clinopyroxene are evaluated with a one-dimensional, steady-state, decompressional melting model. The results indicate that fractional melting in the garnet-stable region is required before conventional fractional melting in the spinel-stable region. Geothermobarometric pressure-temperature estimation results indicate that the peridotite xenoliths were derived from ~2.5 GPa where asthenosphere/lithosphere boundary is expected based on the geophysical investigations.

Abyssal peridotites recovered from the mid-ocean ridges are known to undergo melting from the garnet-stable region to the spinel-stable region. Thus, depleted spinel dunite/harzburgite layer is expected to be perched atop fertile spinel/garnet harzburgite-lherzolite layers as a melting column in the mid-ocean ridge. Since the petit-spot peridotite xenoliths cover a long range of the oceanic stratigraphy deep down to the lithosphere/asthenosphere boundary, we present more detailed chemical and thermal state of the whole oceanic lithosphere in the presentation. In addition, we attempt to present a perspective vision for future petit-spot drilling.

How to cite: Akizawa, N., Ishikawa, A., Niwa, Y., Alard, O., Greau, Y., Hirano, N., and Machida, S. and the YK20-14S/YK21-07S/YK24-10S scientific teams: Chemical and thermal state of oceanic lithosphere reconstructed by petit-spot mantle xenoliths from the northwestern Pacific, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10999, https://doi.org/10.5194/egusphere-egu25-10999, 2025.

The consolidation state of sediments provides crucial information about the pore pressure in sediments, as well as the loading and unloading history of sedimentary basins. We performed consolidation tests on mudstones and calcareous oozes just below the thick volcaniclastics in the Hellenic Arc Volcanic Field, Greece. These sediments were sampled from the International Ocean Discovery Program (IODP) Expedition 398 in the Christiana, Santorini, and Kolumbo (CSK) volcanic field.

To understand the in-situ stress and pore pressure, we compared the preconsolidation stress (p_c) from the consolidation test with the in-situ effective overburden stress (σ’_v) calculated from the shipboard bulk density measurement of core samples. The overconsolidation ratio (OCR = p_c/σ’_v) is used to identify the state of underconsolidation (OCR < 1) or overconsolidation (OCR > 1) at each drill site.

In the IODP Sites U1589, U1590 and U1593 in the Anydros Basin, underconsolidation states were identified in the interval 200-600 m below sea floor (OCR = 0.59 to 0.85). A maximum of 40% of the effective in-situ overburden is supported by the excess pore pressure at 200 mbsf. These underconsolidated intervals are overlain by >200 m of volcaniclastics derived from the Santorini and the Kolumbo volcanoes. Therefore, the rapid sediment supply (0.8-1.0 m/ky) from the submarine volcanoes apparently leads to the excess pore pressure, which can make sedimentary basins unstable.

On the other hand, measurements from IODP Sites U1591 and U1598 in the Christiana Basin, and Sites U1592 and U1599 in the Anafi Basin showed normal consolidation (i.e., OCR = 1) and overconsolidation (OCR =1.27-2.52) states. Sediments which showed overconsolidation are mostly composed of dolomitic mudstones. The effect of cementation is identified from their consolidation curves, implying that the intergranular bonding contributes to the overconsolidation of sediments. In the presentation, the maximum amount of erosion is calculated to explain the overconsolidation states in the Cristiana and Anafi basins.

How to cite: Yoshimoto, T., Yamamoto, Y., Manga, M., Beethe, S., McIntosh, I., Woodhouse, A., Chiyonobu, S., Koukousioura, O., Druitt, T., Kutterolf, S., and Ronge, T. and the IODP Exp. 398 Scientists: Consolidation state of sediments in the Hellenic Arc Volcanic Field, Greece: Evidence for excess pore pressure caused by huge eruptions and mass wasting (IODP Expedition 398), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11443, https://doi.org/10.5194/egusphere-egu25-11443, 2025.

IMMAGE is a Land-2-Sea drilling project designed to recover a complete record of Atlantic-Mediterranean exchange from around 8 million years ago, to its current configuration with a gateway through the Gibraltar Strait. The aim of the project is to evaluate the influence of Mediterranean-Atlantic exchange on local, regional and global climate before, during and after the formation of a salt giant – the Messinian Salinity Crisis (MSC). This is being achieved by targeting Miocene offshore sediments on either side of the Gibraltar Strait with IODP Expedition 401 and recovering Miocene successions from the two precursor connections now exposed on land in southern Spain and northern Morocco with ICDP.

Expedition 401 (December 2023-February 2024) drilled three Atlantic sites (U1385, U1609 and U1610) and one in the Alborán Sea (U1611). The Atlantic sites record strong precessional cyclicity in NGR and XRF data. These records have been astronomically tuned and correlated with Mediterranean Late Miocene-Pliocene sequences that include the MSC. Changes in the character of the Atlantic signals correlate with Mediterranean-Atlantic gateway changes associated with progressive restriction of exchange that led to evaporite precipitation in the Mediterranean and the abrupt termination of the MSC with the Zanclean deluge.

The influence of gateway changes in the Alborán Basin are less obvious. The Messinian sequence recovered from the Site U1611 includes 150 m of near continuous subaqueous sediments through the MSC. Initial sedimentological, faunal and geochemical results suggest during the Miocene the basin was mostly highly stratified with anomalous but not extreme salinity even during the MSC. Sediments deposited by bottom currents which are commonly associated with gateway exchange only occur in the Pliocene. This suggests that the Gibraltar Strait only started functioning as the Mediterranean-Atlantic gateway from 5.33 Ma and that during the Messinian the Mediterranean-Atlantic connection must have been elsewhere. Future ICDP drilling of the fossil gateways through Morocco and Spain are required to identify and characterise this enigmatic gateway.

How to cite: Krijgsman, W., Flecker, R., Ducassou, E., Williams, T., and 401 Science Party, E.: New results from IODP Expedition 401 and their implications for the next phase of IMMAGE Land-2-Sea drilling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11595, https://doi.org/10.5194/egusphere-egu25-11595, 2025.

The ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase-1 investigates a series of drill cores from glacially overdeepened troughs at several locations along the northern front of the Alps. These basins provide an excellent but yet underexplored archive with regard to the age, extent, and nature of past glaciations. Drilling operations started in 2021 when two sites were drilled in the Northern Alpine foreland. In addition, DOVE analyses included four legacy sites providing a combined 1750 m of cored Quaternary sediment and over 40 m of underlying bedrock cores. A unified characterization of the sedimentary infill of these troughs allowed recognition of various orders of glacial sequences, which were defined by depositional pattern (lithology, sedimentology, geotechnics), wire-line logging data (petrophysics) and seismic data (seismic sequence stratigraphy and facies analysis). Several geochronological methods were employed and luminescence dating proved to allow assigning the glacial sequences to respective marine isotope stages (MIS).

This glacial sequence stratigraphy is interpreted in terms of glacial advance and retreat cycles into basins carved by this or by older glaciations. All drilled overdeepened glacial troughs contain more than one glacial advance-retreat leading to a stacked preserved record of past ice advances. Correlation of the glacial sequence stratigraphy across the northern Alpine arch emphasizes that most sediments were deposited during MIS 6, indicating a strong erosional and depositional pulse during the penultimate glaciation with two-to-three ice advances. Some troughs contain older sequences (i.e. MIS 8) indicating that MIS 6 might have reoccupied pre-existing basins formed by older glaciations. Erosion and infilling patterns during MIS 2 clearly contrast that from MIS 6 and older glacial cycles as many troughs remained underfilled since the Last Glaciation Maximum (LGM) and contain still lakes today. Moreover, it is important to note that during the last glacial cycle, a desynchrony of glaciations has been observed across the Alps, i.e. more extensive glaciation during MIS 4 as well as an earlier onset of the last glacial advance in the western Alps. This can be explained by shifts of the polar front over the North Atlantic that caused different regional maxima of precipitation, which triggered spatial offsets in the timing of past glaciations.

Overall, the overarching pattern emerging from DOVE Phase-1 so far is the dominance of MIS 6-dated sedimentary fills of overdeepenings with older sequences only preserved in a few selected sites. MIS 6 played obviously a key role in landscape evolution along the northern margin of the Alps. This consistent pattern is very surprising and poses the question if it also occurs around the entire Alpine arch, or whether it is restricted to the northern Alpine sections that were covered in DOVE Phase-1. Thus, a prolongation within DOVE Phase-2 is currently planned to comprise four sites in overdeepened troughs in the southern and western areas (Slovenia, Italy, France).

How to cite: Anselmetti, F., Bavec, M., Crouzet, C., Fiebig, M., Gabriel, G., Mencin Gale, E., Monegato, G., Novak, A., Preusser, F., Scardia, G., Valla, P., and Scientific Team, D.: ICDP project DOVE: Drilling Overdeepened Alpine Valleys to decipher (a)synchroneities of glaciations around the Alps, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11809, https://doi.org/10.5194/egusphere-egu25-11809, 2025.

The mixed carbonate-siliciclastic barrier and atoll reef system offshore Belize is the largest modern tropical reef complex in the Atlantic Ocean, highly sensitive to past and future sea-level changes. The deglaciation and increasing temperatures after the Last Glacial Maximum caused a rise in sea level characterized by multiple melt-water pulses and stillstands, which left their characteristic marks in the morphology and growth pattern of the Belize Barrier Reef. Such postglacial sea-level change indicators provide thus critical details to reconstruct how sea level rose from the full glacial to Late Holocene levels. We present a study that was done within the framework of the active IODP proposal “Postglacial Atlantic sea-level and climate reconstruction through drilling the Belize Barrier Reef (BBRdrill)”. To gain better insight into the morphological details, we acquired a high-resolution (1 x 1 m) topographic dataset of the Belize Barrier Reef with a state-of-the-art multibeam bathymetric device. Moreover, by investigating the entire point cloud of sonar reflections, we were even able to visualize the rarely investigated overhanging reef walls in great detail.

Concise morphological features indicating stagnant or slow-change phases were mapped in detail. They comprise elongated ridges at various water depths, indicating reef build-up to past sea level, which are aligned in single or multiple parallel lines, connecting hook-like structures, or complex honeycomb patterns. We hypothesize that older, postglacial and glacial reefs are stacked more or less vertically below the outermost ridge and the wall. The walls contain various erosional notches indicating still stands of sea level causing enhanced erosion in the quasi-vertical structure. This vertical stacking of the barrier reef crests gets affected towards the submarine outflow area of the English Cay Channel, where turbid waters likely challenged reef growth so that the aggradation eventually stopped and reefs drowned forming a reef line deepening towards the channel.

We provide a statistical distribution of features indicative for sea levels over 100 km length of Belize Barrier Reef, indicating the different slow-downs or stillstands of sea levels since the last glacial maximum. Several levels of erosional notches could be mapped at water depths of ~ -60 to -110 m, whereas the single or multiple reef crest occurs within a range of ~ -15 to -40 m water depth relating to sea levels ~13-16 ka and ~8-11 ka, respectively. The bathymetric distribution of notches and reefs suggests also the existence of a vertical tectonic displacement in the reef.

"BBRdrill" proposes to drill these morphological features in order to i) reconstruct the LGM and postglacial sea-level rise in the western Atlantic ii) reconstruct environmental parameters using corals, coralline algae, and cryptic microbialites; iii) elucidate reef paleoecology in relation to postglacial sea-level rise and associated environmental changes; and iv) assess microbial life in a barrier-reef system.

How to cite: Hosmann, S., Fabbri, S. C., Anselmetti, F. S., and Gischler, E.: Morphology of the Belize Barrier Reef as indicators for postglacial Atlantic sea-level changes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11853, https://doi.org/10.5194/egusphere-egu25-11853, 2025.

We report the first results of the International Ocean Discovery Program Expedition 402 in the Tyrrhenian Sea (February 9 to April 8, 2024).  Almost 40 years have passed since the discovery of exposed mantle west of Iberia by ODP but key questions remain unanswered, such as the nature of the mantle, whether it is subcontinental or formed by ultraslow seafloor spreading, or how models can explain the apparent lack of melting. Since then, the mantle has only been probed at mid-ocean ridges, because obtaining samples and data from drilling in magma-poor COTs is a major challenge, as the exposed mantle is typically buried under kilometers of sediment.

The Tyrrhenian Basin is the youngest of the western Mediterranean, formed from the Middle Miocene to recent times by continental extension associated with the ESE-SE rollback of the subducting slab and with the migrating Apennine subduction system. The Tyrrhenian is an outstanding location to test COT formation models by drilling because of its thin sedimentary cover, the presence within a few tens of kilometers of the conjugate pair of COT margins, and the availability of high-quality geophysical data suggesting the presence of serpentinized mantle rocks in its center. A surprising key feature of the basin is the lack of seafloor spreading after mantle exhumation, which allows for the first time a close look into the early stages of the exhumation process.

The main objective of the IODP Exp. 402 was to determine the nature of the geological basement in the central part of the Tyrrhenian Basin and in the conjugate margins to the west and east. The objectives included the kinematics of the opening, the deformation mechanisms of the crust and mantle, and the relationship of the melted products to the exhumed mantle.

The samples and data collected during Exp.402 provide an extensive new data set to determine mantle heterogeneity, the nature and history of melt production and impregnation, and the extent and evolution of serpentinization and carbonate formation; to constrain the geometry and timing of deformation that led to mantle exhumation; to study fluid-rock interactions between seawater, sediment, and the serpentinizing mantle; and to constrain geodynamic models of rifting and COT formation.

How to cite: Zitellini, N. and the Exp. 402 Science Party: Tyrrhenian magmatism and mantle exhumation: first results from IODP Exp. 402, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12058, https://doi.org/10.5194/egusphere-egu25-12058, 2025.

The success of 55+ years of scientific ocean drilling through the International Ocean Discovery Program (IODP) and its predecessors has provided the international scientific ocean drilling (ISOD) community with a wealth of legacy material and data. These physical and digital archives are stored in the three IODP core repositories and several programme databases. Greater utilisation of legacy archives is anticipated as ISOD enters its next phase starting in 2025. For instance, advances in dedicated Earth Science software now make it possible to generate digital representations of cores and use these as a primary data source (e.g., through packages like Code for Ocean Drilling Data, or CODD; Wilkens et al., 2017). There is significant scope for integrating these “virtual cores” and data derived from them following the re-analysis of physical “legacy core” stored in IODP’s core repositories. This integration offers one pathway to increase the capacity and utilisation of legacy material in the future.

The 21^st Century Drilling Workshops Project aimed to test best practices for the re-analysis and integration of physical and digital IODP/ODP/DSDP legacy material through four global workshops hosted at all three core repositories. These workshops also tested best practices for training early career researchers in hands-on core analysis. Finally, the linked workshops also addressed the scientific objectives of tracing changes in ice-rafted debris (IRD) and biological responses to shifting Antarctic fronts in the Southern Ocean due to Miocene ice volume variability. To achieve this, the four workshops targeted five sites spread across the Indian, Atlantic and Pacific sectors of the Southern Ocean.

The first workshop was hosted as part of J-DESC’s RECORD ReC23-01 at the Kochi Core Centre (KCC, Japan) in August 2023. Two ECORD MagellanPlus 21^st Century Drilling Workshops were held at the Bremen Core Repository (BCR, Germany) in April and November 2024. The final USSSP 21^st Century Drilling workshop was held in February 2025 at the Gulf Coast Repository (GCR, USA). RECORD ReC23-01 investigated DSDP Site 266 (Indian Ocean Sector), MagellanPlus Workshop 1 and 2 respectively investigated ODP Site 704 and ODP Sites 1090 and 1092 (Atlantic Ocean Sector), while the USSSP Workshop will investigate a Pacific Sector site. The target sites were carefully chosen to address the scientific objectives while ensuring coverage of sites spanning IODP’s entire history. This approach enabled the workshops to identify potential differences in the analytical requirements of legacy material depending on the age of the cores.

Through the four workshops, we have brought together ~80 researchers (early career to experienced) from a wide range of IODP and non-IODP countries. Though linked by common goals, each workshop had its own specific focus and developed a path tailored toward participant needs and site-specific requirements. By conducting the workshops sequentially, we had the opportunity to evaluate our approaches and adapt them as appropriate. Here, we aim to illustrate initial research highlights alongside several case studies highlighting best practice approaches for investigating digital and physical legacy material to provide powerful research and training opportunities for the next generation researchers engaged with ISOD.

How to cite: Drury, A. J., Auer, G., Christensen, B., Kuroda, J., Kubo, Y., De Vleeschouwer, D., Westerhold, T., Röhl, U., Childress, L., and Ikehara, M. and the 21st Century Drilling Workshops Team Members (in alphabetical order): 21st Century Drilling Workshops Project - Building capacity in the digital domain using scientific ocean drilling legacy material, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13173, https://doi.org/10.5194/egusphere-egu25-13173, 2025.

The Nankai Trough subduction zone, located off the southern coast of southwestern Japan, has a well-documented history of large Mw > 8 earthquakes and significant tsunamis (e.g., Ando, 1975; Garrett et al., 2016). This region has been the focus of extensive research, including numerous scientific ocean drilling expeditions conducted through the Deep Sea Drilling Project (DSDP), the Ocean Drilling Program (ODP), the Integrated Ocean Drilling Program (IODP), and the International Ocean Discovery Program (IODP).

In this study, we compile all available friction data and shipboard routine X-ray diffraction (XRD) analyses from across the Nankai Trough. Our findings reveal that while individual friction studies show systematic variations related to mineralogy (e.g., Ikari et al., 2018), temperature (e.g., den Hartog et al., 2012), and pore-fluid pressure (e.g., Bedford et al., 2021), only the correlation between friction and clay mineral content is consistently observed across the entire dataset. Specifically, the friction coefficient measured over velocity scales from nanometers per second to millimeters per second generally remains below 0.6, which is lower than the typical ‘Byerlee’ friction value of 0.85 under normal stress conditions below 200 MPa (Byerlee, 1978), and exhibits an inverse correlation with clay mineral content. The rate-and-state friction parameter (a-b) varies significantly between -0.01 and 0.02, showing no clear relationship with clay mineral content. This lack of correlation is likely due to the diverse experimental conditions across different studies. However, it is notable that velocity-weakening behavior becomes less frequent at the higher end of this velocity scale (>10 μm/s), which may help explain the widespread occurrence of slow slip events in the Nankai Trough. In contrast, samples tested at higher velocity scales (centimeters per second to meters per second) display pronounced frictional weakening, with the friction coefficient dropping to very low values (~0.1) once slip velocities exceed 0.1 m/s.

The wide variation in experimental friction data reflects the complex and heterogeneous frictional properties of the Nankai Trough and aligns with the diverse seismic behaviors observed in the region. The dataset compiled in this study serves as a robust basis for constraining the frictional characteristics of the shallow portion of the Nankai Trough subduction zone.

How to cite: Zhang, J., Faulkner, D., Okuda, H., Bedford, J., Ikari, M., Schleicher, A., and Hirose, T.: Synthesis of the laboratory frictional properties of a major shallow subduction zone: the Nankai Trough, offshore SW Japan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13865, https://doi.org/10.5194/egusphere-egu25-13865, 2025.

Scientific ocean drilling has a rich history in the United States, beginning with Project Mohole in 1961. In 1966, the National Science Foundation (NSF) funded the establishment of the Deep Sea Drilling Project (DSDP), which, beginning in 1968, carried out coring expeditions aboard the purpose-built drilling vessel Glomar Challenger, managed by the Scripps Institution of Oceanography. The program became international in 1975 when the Federal Republic of Germany, United Kingdom, France, Japan, and the Soviet Union joined DSDP.

DSDP concluded in 1983 and was succeeded by the Ocean Drilling Program (ODP). The workhorse vessel for ODP (1985-2003) and the subsequent Integrated Ocean Drilling Program (IODP-1; 2003-13) and International Ocean Discovery Program (IODP-2; 2013-24) was the JOIDES Resolution (JR), owned by Siem Offshore and leased and managed by Texas A&M University. Expeditions during IODP-1 and IODP-2 were also implemented by the European Consortium for Ocean Research Drilling using a mission specific platform model, and by Japan aboard the riser-equipped drilling vessel Chikyu.

Because of a long-term decline in available funds, the lease agreement for the JR ended in 2024; thus, for the first time in more than 50 years, the U.S. is without a dedicated platform for scientific ocean drilling. In this presentation we describe U.S. plans for a Subseafloor Sampling Program (S3P) to succeed IODP-2. S3P will follow a mission specific platform approach. Proponents will submit drilling proposals directly to NSF, which will employ a semiannual review panel to evaluate them in the context of the internationally developed guiding document, “2050 Science Framework: Exploring Earth by Scientific Ocean Drilling.” In addition, the U.S. community is developing a list of near and intermediate term science priorities through the FOCUS (“Future Ocean Drilling in the U.S.”) workshop effort.

A newly created Scientific Drilling Coordination Office (SODCO) will identify and procure appropriate platforms for projects that are positively reviewed and selected for drilling; it is hoped that up to two expeditions per year can be implemented. SODCO will also assist the U.S. community through planning and training workshops, pre-drilling activities, support for technological innovation, and science communication and outreach. A robust advisory committee structure will ensure that the U.S. subseafloor sampling effort is open, broad-based, community-driven, and motivated by achieving the highest quality science at acceptable risk.

International collaboration in ocean drilling remains a priority for the U.S. For example, NSF is contributing significant funds toward IODP³/NSF Expedition 501 (New England Shelf Hydrogeology) and will support the participation of around a dozen U.S. scientists. Similarly, the U.S. is interested in providing opportunities for non-U.S. scientists aboard S3P expeditions. The exact mechanisms and policies for mutual participation remain to be developed; the U.S. will take a flexible approach that emphasizes transparency, reciprocity, and the interests of potential partners.

How to cite: Brenner, C. and Johnson, K.: After IODP: The Next Phase of U.S. Scientific Ocean Drilling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14232, https://doi.org/10.5194/egusphere-egu25-14232, 2025.

China has been an active participant in scientific ocean drilling programs over the past decades, significantly contributing to advances in marine science, talent development and technological innovation. With the officially conclusion of the International Ocean Discovery Program (IODP) in 2024, China is gearing up for a new phase of ocean exploration. This presentation will comprehensively review China's achievements in ocean drilling and outline its ambitious future plans.

Under the leadership of the Ministry of Science and Technology and the National Natural Science Foundation of China, a new China Multifunctional Platform (CMP) will be established. The CMP will be jointly operated by the Science Center at Tongji University and the Platform Center at the Guangzhou Marine Geological Survey. It will operate with high flexibility, selectively deploying appropriate drilling ships or subsea drilling rigs such as the DV Meng Xiang for deep-water drilling, the "Haiyang Dizhi Shihao" for shallow-water drilling, and the "Hainiu" for shallow target layer drilling, based on specific scientific goals and drilling requirements.

China's ocean drilling strategy is founded on the principles of openness and inclusivity. Proposals for drilling missions will be solicited globally, evaluated by an international panel of experts, and the best projects will be selected for implementation. In keeping with the tradition of scientific ocean drilling programs, all data and samples collected during China-led expeditions will be shared openly, enabling scientists from around the globe to contribute to groundbreaking research. China's commitment to international cooperation extends to maintaining and expanding partnerships with current IODP members, including the United States, Japan, 14 European countries, Canada (ECORD), Australia and New Zealand (ANZIC), India, and others. By broadening the scope of collaboration, China aims to create opportunities for more countries, particularly developing nations, to engage in ocean drilling and contribute to the collective understanding of our oceans.

How to cite: Tuo, S., Wang, W., and Jian, Z.: China's Scientific Ocean Drilling: Past and Future, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14554, https://doi.org/10.5194/egusphere-egu25-14554, 2025.

Since 2004, the U.S. office of the International Ocean Discovery Program (IODP) has utilized the JOIDES Resolution (JR) and its related facilities and scientists to reach out to educators and the general public in efforts to raise awareness and knowledge about the interdisciplinary fields of the program, including climate and ecosystem evolution, palaeoceanography, the deep biosphere, sustainable georesources, deep crustal and tectonic processes, geodynamics and geohazards. Over these past few decades, IODP has strived to not just push the bounds of scientific knowledge, but also make these findings accessible to the public. Towards these goals, the program has hosted the School of Rock (SOR) professional development program – focusing on the training and education of educators – as well as Onboard Outreach Officers (professional education and outreach personnel embedded into expedition science parties). Together, these two programs have generated a vast library of resources – developed through partnerships with shipboard educators and scientists – available to educators worldwide. Topics addressed range from seafloor spreading and plate tectonics, to microbiology and climate change. The materials are easy to filter (e.g. by grade level) to meet the needs of learners in varied settings.

The JR’s Onboard Outreach (OOO) program has also served as a pivotal bridge between the scientific endeavors of the JOIDES Resolution and the public. This program evolved significantly over the past 15 years, leveraging both advancements in technology and changing needs and attitudes towards public outreach. Through the efforts of Outreach Officers, the importance of deep sea ocean drilling has been disseminated to the general public on a global scale.

School of Rock has also served as a fruitful generative vehicle for new ideas, including a community-driven, travelling informal exhibit program, and mechanisms for developing long-lasting relationships between K12 educators and university faculty.  Beyond its legacy of a significant body of educational resources, SOR has also impacted how professional development is done by serving as a template for teacher/researcher collaboration and exchange of knowledge —  spawning and inspiring new programs such as STEMSEAS and JR Academy (for undergraduate students). In this presentation, we will share highlights of this legacy, plans for the future of scientific ocean drilling education and outreach in a post-JR world, and new efforts to shape the next generation of geoscientists.

How to cite: Cooper, S., White, L., and Thesenga, D.: IODP Education and Outreach: An Enduring Legacy from Two Decades of IODP programming and opportunities in the U.S. and beyond, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14962, https://doi.org/10.5194/egusphere-egu25-14962, 2025.

The exploration well GeoLaB-1 will be drilled in February 2025 into the Tromm pluton in the Odenwald (SW Germany) with a maximum depth of 500 m. An only 20-30 cm thin veneer of Quaternary sediments is expected on top of a few m of weathered granite, followed by massive granites and quartz-monzonites until final depth. The drilling plan involves full coring and a comprehensive logging program of the Tromm pluton. Drilling is accompanied by 2D-seismic, gravimetric, geoelectric, and magnetic surveys. The cores will provide basic information about the compositional heterogeneities of the Tromm pluton, particularly their mineralogy, fracture network, hydrothermal alteration, and their microbiology with depth. The focus of the investigations will be on petrography and mineralogy, petrophysical properties, quantitative analysis of fracture networks, the native upper crustal microbiome, hydrochemistry, hydrotesting, and geomechanical modelling. Borehole completion includes implementation of glass fiber optic cables and geophones for later monitoring.

The results will influence the site selection and design for the construction of the GeoLaB research underground infrastructure. Furthermore, it will allow the evaluation of potential future impacts from tunnel construction and laboratory operation.

How to cite: Deon, F., Grimmer, J. C., Mitzscherling, J., Kamrani-mehni, S., Giese, R., Bauer, F., Garipi, X., Seib, L., Dashti, A., Schmidt, N. L., Bahrami Dashtaki, N., Lüth, S., Sass, I., Kohl, T., Rudolph, B., and Kolditz, O.: The GeoLaB-1 well, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15640, https://doi.org/10.5194/egusphere-egu25-15640, 2025.

The Tibetan Plateau is part of a region often referred to as the ‘Third Pole’ because its ice fields are the world’s largest outside the polar regions.  Almost one third of the world's population depends on the water supply from the Tibetan Plateau and future climate change will have a large impact on the region, affecting the water cycle, water resources, ecology and the economy. To assess predictive climate model scenarios, it is crucial to improve our understanding of the timing, duration and intensity of past climatic variability and its environmental impact in this sensitive area over long geologic time scales. For this, we use a sequence of lacustrine sediments from the Tibetan Plateau, which was acquired during the drilling campaign for the international ICDP project ‘The Nam Co Drilling Project, Tibet (NamCore)’ that was carried out in June/July 2024. The lake is located 4700 m above sea level, has a maximum depth of approximately 100 m, and covers an area of more than 2000 m². In contrast to much younger and often incomplete climate archives on the Tibetan Plateau, the sedimentary sequence of Nam Co contains continuous information on climate history with age estimations of more than one million years. The investigation of this sequence will cover several cycles of glacial and interglacial stages.

The LIAG Institute for Applied Geophysics completed geophysical downhole measurements at the drill site in the central area of the lake. This involved multi-tool logging of two boreholes down to a depth of 185 m and 360 m below lake floor, respectively. Preliminary analyses reveal several lithological units that can be characterised by their physical properties. In addition, certain sections exhibit cyclic variations in the sedimentary sequence. This is beneficial for cyclostratigraphy and time series analyses, which in turn can lead to the creation of a robust time-depth scale.

Information on depositional age and lithology will be combined to derive statements on the relationship between aridity and precipitation in the past and to interpret these in the context of global climate development.

How to cite: Ulfers, A., Haberzettl, T., Wang, J., Zhu, L., Clark, L., Henderson, A. C. G., Vogel, H., Ju, J., Adolph, M.-L., Vinnepand, M., Zeeden, C., and NamCore Science Team, T.: Insights into geophysical downhole logging data from the ICDP project ‘The Nam Co Drilling Project, Tibet (NamCore)’, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16325, https://doi.org/10.5194/egusphere-egu25-16325, 2025.

Charles Darwin described in 1842 the island of Bora Bora (Society Islands, Central South Pacific) as key example for a subsiding basaltic oceanic island with related reef development. He recognized that the Bora Bora lagoon developed between an outer barrier reef with a sand apron and an inner fringing reef attached to the shore of the volcanic island. In order to quantify past sea-level and paleoenvironmental changes and island subsidence, the lagoonal sediments were cored in 2024 in the context of the Bora²coring project. Previous shorter cores indicated that the Holocene lagoonal sediments are of a mixed-carbonate-siliciclastic nature: the carbonate fraction is formed in-situ in the shallow-water depositional environment, whereas the siliciclastic fraction originates from the volcanic island. A recent seismic survey documented that below the Holocene sequence, several stacked depositional sequences occur, which must reflect the combined effect of sea-level fluctuations and ongoing island subsidence. To unravel the complex depositional history, a full suite of sedimentological, paleontological, petrophysical and geochemical analysis of the cores are conducted. In addition, samples of recent soil and lagoonal sediment will provide a data set to calibrate the measured proxies from the cores.

A total of 33 m of sediment cores were recovered and spliced into a composite section with a length of 18.2 m. The composite section reveals variable lithologies. A 4.5 m thick Holocene carbonate mud overlays a stiff, red to grey-bluish mottled, carbonate-free clay, forming the next underlying sequence. Coarse-grained carbonate sediments reappear at a depth of 9 m. Below this second carbonate unit, carbonate-free, grey-to-brown clay occurs, with occasional interbeds of white carbonate. Downcore, the clay becomes reddish again.

These sediments will be interpreted in the context of the interplay between sea-level, island subsidence and resulting accommodation space. A permanent connection to the open ocean seems to have existed only during the Holocene. In contrast, the deposition of siliciclastic fines during glacial phases suggests a distal alluvial or even shallow lacustrine depositional environment with no carbonate production within the lagoon. The occurrence of carbonates in 9 m depth indicate an older marine transgression and regression cycle presumably during an interglacial period overlying another glacial sequence.

All the different analyses will eventually merge toward an improved knowledge of island subsidence and the chronology and amplitudes of sea-level changes. The siliciclastic fines will additionally serve as an excellent proxy for hydroclimate-dependent weathering and erosion processes on the island.

How to cite: Felder, M. H., Hosmann, S., Camoin, G., Eisenhauer, A., Gischler, E., De Jonge, C., Kremer, K., Lecchini, D., Milne, G., Vogel, H., and S. Anselmetti, F.: Multiple interglacial sequences in a Darwin-type barrier-reef lagoon: Implications for paleoclimate, sea-level changes and subsidence since the Late-Pleistocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16330, https://doi.org/10.5194/egusphere-egu25-16330, 2025.

IODP Expedition 405 “Tracking Tsunamigenic Slip Across the Japan Trench” (JTRACK) was a challenging but successful 4-month expedition (September 6 to December 24, 2024 – 56 scientists) that revisited and drilled the large co-seismic slip region of the 2011 Mw 9.0 Tohoku-oki earthquake, 12 years after IODP Expedition 343 “JFAST” had done so. One of the expedition’s primary objectives is to evaluate temporal variations in stress state, fluid flow, and physical properties in the thirteen years since the Tohoku-oki earthquake. This will allow an assessment of how faults heal and reload after a major earthquake, and the role of fluids in such processes. The second objective is to investigate the compositional, structural, mechanical, hydrological, and frictional properties of the rocks in and around the shallow plate boundary, to assess the role of each of those components on the plate boundary location and slip behavior, and to understand the long-term evolution of this prism. Two sites were successfully drilled. At Site C0019, located ~8km landward of the trench axis, drilling intersected the frontal prism, décollement, and subducted plate at the JFAST location. Drilling at Site C0026 intersected the sediment sequence and underlying oceanic crust of the incoming Pacific Plate, thus serving as a reference site. Operations consisted of: 1) collecting logging while drilling (LWD) data at C0019 and C0026 from the seafloor to oceanic crust; 2) coring at C0019 through the entire frontal prism, décollement, and oceanic crust, and at C0026 through the incoming sediment sequence; 3) installing temperature sensors in two borehole observatories to characterize fault zone hydrogeology by re-instrumenting the existing observatory in borehole C0019D (JFAST observatory) and the developing and instrumenting a new observatory borehole C0019P (JTRACK observatory). Overall, Expedition 405 was a huge operational success. Under 7 km of water, it successfully recovered cores from multiple shallow hydraulic piston coring system (HPCS) holes at each site, as well as three deep small-diameter rotary core barrel (SD-RCB) holes at Site C0019 to ~950 mbsf and one SD-RBD hole at Site C0026 to ~300 mbsf. Together, the boreholes provide continuous records of the subsurface from the seafloor to the deep sedimentary rocks and mafic volcanic rocks of the oceanic crust, documenting the Pacific oceanic plate as never before. The plate boundary fault zone was drilled and sampled in multiple holes, providing a unique dataset from an active fault zone that constrains its lateral heterogeneity. Measurements and observations made provide key data to evaluate the controls on shallow tsunamigenic slip and the temporal variations in stress and physical properties and conditions that occur following a great subduction zone earthquake. Overall, the range of data gathered during the expedition is vast, encompassing sedimentary and volcanic processes, paleoseismology, paleoclimate and paleo-oceanography, earthquake mechanics, and tectonic processes at convergent margins.

How to cite: Conin, M., Kodaira, S., Fulton, P., Kirkpatrick, J., Regalla, C., Ujiie, K., Okutsu, N., Maeda, L., Toczko, S., and Eguchi, N. and the IODP Expedition 405 Scientists: Preliminary assessment of IODP Expedition 405 JTRACK in the Japan trench: investigating slip and tracking fault healing after a Mw9 earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16584, https://doi.org/10.5194/egusphere-egu25-16584, 2025.

We report initial results from the first phase of the ICDP-funded ‘Drilling the Ivrea-Verbano zonE‘ (DIVE) project in Val d’Ossola (northern Italy). Characterized by pronounced geophysical anomalies, the exposed Ivrea-Verbano Zone offers unique opportunities to test geophysical and petrologic models about the lower continental crust (LCC) and its transition to the upper mantle. From October 2022 to April 2024 two boreholes of respectively 578.5 and 909.5 m depth were drilled using continuous diamond double tube wireline coring. Core recovery was ~100% for both boreholes. During and after drilling, geophysical logs were acquired, providing natural and spectral gamma ray, magnetic susceptibility, electrical resistivity (SPR and DLL), spontaneous potential, sonic, acoustic and optic televiewer data. Retrieved rock cores were described and classified by the DIVE drilling project science team and later shipped to the BGR Rock Core Repository in Spandau-Berlin, where core density and magnetic susceptibility were measured with a multi-sensor core logger followed by XRF scans.

Here we summarize core descriptions, initial geochemical results, geophysical logging data, drill hole fluid chemistry and gas compositions, and preliminary microbiological investigations. The two boreholes sampled two fundamentally different compositions of the lower continental crust: one (5071_1_B) mostly consists of metasedimentary rocks and a few amphibolites, and the second hole (5071_1_A) mostly captures a variety of gabbroic rocks with intercalations of granulite facies metasediments, pyroxenite, and intrusive gabbronorite. This is in agreement with the expected structural positions but allow to study the continental lower crust across numerous spatial scales.

In borehole 5071_1_A, several zones of ultramylonites, cataclasites, fault gauges and pseudotachylites were recovered documenting important episodes of semi-brittle behaviour of the LCC after assembly in the Lower Permian. Along the entire drillholes fractures and open cracks were observed and sampled, some of them filled with precipitates of quartz, carbonates, sulfides, graphite, and oxides.

Continuous monitoring of borehole fluids and gases provide evidence of varying gas mixtures including H₂, CH₄, and CO₂, indicating diverse fluid sources and microbial activities in the deep crust. At the current stage, we are evaluating the biotic and abiotic contributions. Some of these open fractures are potentially promising hosts for microbial communities and are currently under investigation. Additional samples for microbiological studies were taken every 20 m from the drillcores and are currently cultivated for further investigations and also analyzed for bulk rock major and trace elements.

The two drillholes of DIVE provide unprecedented details of the variability of lower continental crust. Metasedimentary sections of the drilled LCC are important reservoirs for volatile and radiogenic heat producing elements, while dominantly mafic sections of the lower continental crust are depleted in these elements. Measured seismic velocities and densities are affected by numerous fractures but metasedimentary rocks are uniformly lower in density (2.5-2.8 g/cm³) compared to the mafic section (2.8-3.4 g/cm³) indicating that the lowermost part of the drilled section enters the continental crust–mantle transition zone.

How to cite: Müntener, O., György, H., Andrew, G., Luca, Z., Alberto, Z., Mattia, P., Donato, G., and Marco, V. and the DIVE Drilling Project Science team: From the lower crust towards the crust–mantle transition zone: Initial results from the ICDP DIVE project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16604, https://doi.org/10.5194/egusphere-egu25-16604, 2025.

After the climatic and environmental context of hominin evolution in East Africa centred the spotlight for decades, West Africa gains increasing interest considering a pan-African early human history. However, long and continuous continental climate records from this area illuminating regional hydroclimatic impacts and differences across Africa are missing. This is a major shortcoming as fundamental offsets in W-E hydroclimates are expectable that may have influenced human dispersal. Here we present the million-year-old hydroclimate record from Lake Bosumtwi in tropical West Africa, suggesting that this area has been strongly impacted by hemispheric system interactions (N-S-Atlantic, 100 ka cycles) and local insolation including half-precession. Comparing our findings with records from tropical East Africa governed by an Indian Ocean signal (20 ka, 400 ka cycles), we can confirm strongly contrasting hydroclimatic trends. To understand the meaning of these, we compare hydroclimatic signals from Lake Bosumtwi and Chew Bahir (tropical East Africa) providing us with important relative (moister-dryer) information with climate model output data delivering mean annual precipitation (MAP) estimates. This reveals striking similarities between the considered geoscientific data and climate models raising confidence that the MAP estimates can be reliably used to infer supported biomes. Whilst modelled MAP at Lake Bosumtwi varies between 1050 mm (wet savannah) and 1550 mm (rainforest), Chew Bahir may have been characterised by thorn to dry savannah conditions (550-750 mm/a). In this context, cross-Africa climate modelling suggests that large W-E savannah corridors supporting migration of large mammals and humans spread during periods, when the differences between MAP at both end-members have been low. In contrast, these corridors are interrupted by conditions supporting rainforests, when δMAP is high. These phases coincide with major steps in the evolution of the mega-fauna and hominins providing us with a basis for discussing new perspectives on climate and human co-evolution scenarios.

How to cite: Vinnepand, M., Kaboth-Bahr, S., Gosling, W., Noren, A., Paknia, M., Wonik, T., Martinez, M., Pierdominici, S., Kück, J., Ulfers, A., Danour, S., Afrifa, K., and Zeeden, C.: A million years of contrasting climate system influences shaped potential hominin habitats across Africa – Novel perspectives from Lake Bosumtwi (Ghana, West Africa), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17257, https://doi.org/10.5194/egusphere-egu25-17257, 2025.

Understanding the history of the northern Greenland Ice Sheet (NGrIS) and its connection to long-term changes in the Arctic is crucial for assessing glacial instability thresholds and the cryosphere's response to greenhouse gas emissions. To fill knowledge gaps in the evolution of the GrIS and its climate role, IODP Expedition 400 collected sedimentary records from Sites U1603–U1608 along the northwest Greenland margin and into Baffin Bay. These sites recover a range of deep ocean-to-shelf depositional settings and lithofacies which form proximal archives of NGrIS evolution through the late Cenozoic era.  Across six sites, 2299 meters of core material were recovered, and wireline logging was conducted at four sites. The expedition targeted high-accumulation contourite drifts within, and below, a well-mapped trough mouth fan system. At Site U1607, deep time objectives were achieved with cores extending to 978 meters below the seafloor, capturing Miocene and late Oligocene sediments. This presentation summarizes the initial results in alignment with the key scientific objectives pursued by the expedition scientists: (1) evaluating near-complete NGrIS deglaciations during the Pleistocene and mid-Pleistocene orbital shifts, (2) examining NGrIS expansion timing and links to Pliocene marine heat transport, and (3) studying climate-ecosystem conditions under higher atmospheric CO2 levels over the past 30 million years. The X400 shipboard results, and the ensuing post-cruise research, will enable the assessment of the forcings—oceanic, atmospheric, orbital, and tectonic—affecting the GrIS over various timescales and improve models of glacial inception and interglacial transitions.

How to cite: Knutz, P. C., Jennings, A., and Childress, L. B. and the IODP Expedition 400 Scientists: Unravelling Greenland Ice Sheet and Arctic climate history over the last 30 Million years – Results from IODP Expedition 400, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20836, https://doi.org/10.5194/egusphere-egu25-20836, 2025.

We investigate the characteristics of low-temperature yellow stimulated luminescence (YSL), to compare its utility for dating with infrared stimulated luminescence (IRSL) stimulated at 50 °C (IR₅₀), post-IR₅₀ yellow stimulated luminescence (pIR-YSL) and pIRIR₂₉₀. Altogether, eleven samples from a range of depositional environments and known ages were tested. Thermal stability, bleachability, dose recovery, fading tests and equivalent dose estimation were undertaken. The pIR-YSL signal is stable up to 150 °C but susceptible to thermal transfer at higher temperatures and both the pIR-YSL and YSL₅₀ signals bleach out at a rate and extent that is similar to the IR₅₀ signal. Dose recovery tests on four of the young intermediate samples illustrate that the pIR-YSL signal can be both recovered and fully reset. Fading tests show that all three signals suffer from significant fading and equivalent dose estimations of the saturated samples IR₅₀, IR-YSL and YSL₅₀ signals significantly underestimate relative to the pIRIR₂₉₀ signal. Elevated temperature signal combinations are additionally evaluated with the aim of further understanding the effect of elevated temperatures on the fading rate and ultimately the utility of YSL signals for dating.

How to cite: Buchanan, G., Preusser, F., Fitzsimmons, K., and Lauer, T.: Progress exploring the characteristics of yellow stimulated luminescence on potassium feldspar , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-646, https://doi.org/10.5194/egusphere-egu25-646, 2025.

The sedimentary units overlying the so-called ‘Falaise de la Mine d'Or’ on the South-East coast of Brittany (France) have been studied for decades to reconstruct the evolution of fossil fluvial valleys in Brittany during the Pliocene and Quaternary (Guillocheau et al., 1998; Menier et al., 2006). However, published numerical ages are insufficient to provide a precise age of each of the units described, whose chronology relies on correlations with ESR dating of fluvial sediments from the interior of Central Brittany (Laurent et al., 1996). Thanks to the cron-BRET Project of the MSCA-Bienvenüe Bretagne Programme carried out by the Geo-Ocean Laboratory of the Université de Bretagne Sud in collaboration with the Cosmogenic Nuclide Laboratory of the University of Cologne (Germany), it has been possible to date the lower unit (U1), mainly composed of quartzite gravels and pebbles. In situ ¹⁰Be and ²⁶Al concentrations produced within the quartz of these clasts become controlled by differential rates of decay when shielded from production at the surface (Dunai, 2010). The fact that the sediments are buried under a sedimentary shield of more than three metres, allows for the calculation of a burial age from the concentration of ¹⁰Be and ²⁶Al by using the isochron method (Balco and Rovey, 2008; Granger et al., 2022). Preliminary results provide numerical data that place the formation of this unit 2.72 ± 0.19 million years ago, at the Plio-Quaternary boundary. Our study also includes the dating of the upper unit (U3) mainly composed of sand-sized materials (90-2000 µm), by analysis of the optically stimulated luminescence (OSL) signal of quartz (Murray et al., 2021) at the RenDaL Luminescence Laboratory (Géosciences- Univ. Rennes). The calculation of the palaeodose using Bayesian procedures (BayLum; Philippe et al., 2019) and of the natural dose rate from high-resolution gamma spectrometry (HRGs) measurements provides a burial age range between 263 and 408 ky. These data will be complemented by the dating of the materials composing unit U2 by analysing the infrared stimulated luminescence signal (IRSL) of potassium feldspar to extend the available dates and the knowledge of the landscape evolution of this coastal area linked to glacioeustatic oscillations and neotectonics during the Pleistocene.

How to cite: Arce Chamorro, C., Sautter, B., Guérin, G., Guillocheau, F., Binnie, S., Dunai, T., and Menier, D.: Optically Stimulated Luminescence and in situ 10Be / 26Al cosmogenic dating of the Upper and Lower Units from ‘La Falaise de la Mine d'Or’ at Pénestin (SW Brittany, France) within the cron-BRET Project., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1384, https://doi.org/10.5194/egusphere-egu25-1384, 2025.

Lake sediments form a valuable and often continuous record for reconstructing past climate and the occurrence and impact of natural hazards. The interpretation of this record, however, relies heavily on a robust chronology formed by age-dating the sediments. For recent (i.e. Quaternary) lake sediments, radiocarbon dating of organic material is a fundamental dating technique. However, constructing a lake sediment chronology can be challenging, since the use of radiocarbon dating is dependent on many factors, including the type of material to be dated, depositional circumstances and possible contamination of ¹⁴C. Volcanogenic CO₂, for instance, is depleted in ¹⁴C. This implies that in regions with surface exhalations of volcanic CO₂ the concentration of ¹⁴C in the surrounding atmosphere is diluted. For this study, the effect of volcanogenic CO₂ gas emissions on the use of radiocarbon dating was investigated in the Laacher See volcanic crater in western Germany. This crater was formed after the eruption of the Laacher See Volcano around 13 ka BP. It contains multiple degassing vents emitting CO₂ of magmatic origin, in the form of underwater bubble seeps in the lake (“wet mofettes”) and onshore soil degassing (“dry mofettes”). Living plant material, i.e. leaves of Taraxacum genus plants, were sampled in several locations in the crater and dated to examine their range in radiocarbon ages and spatial variability. Additionally, a > 4 m long sediment core taken in the lake was sampled for organic material and bulk sediment to assess the offset of radiocarbon ages to their true or expected ages. Our results show that all dated samples exceed their true or expected ages, with the Taraxacum samples giving variable radiocarbon ages of up to 9000 a BP. Along a transect of sampled Taraxacum plants, the radiocarbon ages decrease with an increasing distance from the degassing vents along the lake shore. The radiocarbon ages of the sediment core samples show that organic material deposited in the lake is also affected by volcanogenic CO₂ emissions, with some radiocarbon ages exceeding the age of the Laacher See eruption that formed the crater, although no regular offset could be determined for these samples with regard to their depth in the core. Furthermore, the radiocarbon ages do not correspond to a ²¹⁰Pb/¹³⁷Cs age-depth model that was established for the top of the core. Radiocarbon dating is shown to not provide reliable results for establishing a chronology for the sedimentary infill of Laacher See. Further research is required to better understand the influence of volcanogenic CO₂ on organic material, such as effects of temporal and spatial variations in CO₂ flux. In the case of Laacher See, other age-dating techniques should be considered to establish an age-depth model with reliable, non-¹⁴C dependent ages.

How to cite: Claeys, L., Albers, S., Hajdas, I., and De Batist, M.: Volcanogenic CO2 emissions affect radiocarbon dating in a case study from the Laacher See crater lake, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1725, https://doi.org/10.5194/egusphere-egu25-1725, 2025.

This study details the construction of an age-depth model for the uppermost 128 meters of the 600 m long Acıgöl2009-B03 sediment core, retrieved from hypersaline Lake Acıgöl in southwestern Anatolia. The model matches the arboreal pollen record from Acıgöl2009-B03 with the LR04 benthic δ18O stack marine oxygen isotope record. Initial correlation employs the Dynamic Time Warping algorithm, refined through manual tuning. Validation of the model's accuracy incorporates multiple chronological constraints, including three radiocarbon dates, three U/Th dates, and the Kos Plateau Tuff, dated at 161.3 ± 0.1 ka. According to this model, the upper 128 meters of the Acıgöl2009-B03 sequence spans approximately the last 487,000 years, encompassing Marine Isotope Stages (MIS) 1 to 12 and part of MIS 13. Our model serves as an update to the previously published, linearly constructed, age model as being used more anchor point and an efficient algorithm for similarity measurements which lies on a robust statistical foundation. In this period, arboreal pollen data suggest increasing (decreasing) arboreal vegetation input during interglacial (glacial) periods.

How to cite: Çaldırak, H., Ön, Z. B., Akkiraz, S., Çağatay, M. N., Ghaleb, B., Wulf, S., Eriş, K. K., Acar, D., Kaiser, J., and Akçer Ön, S.: Chronology and environmental changes from a sediment core spanning the last 487 kafrom Lake Acıgöl (SW Anatolia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1998, https://doi.org/10.5194/egusphere-egu25-1998, 2025.

Luminescence dating has long been used for dating sediments both in geological as well as archaeological context. Following numerous advances in feldspar and quartz luminescence dating in recent decades, a new method for feldspar dating is currently under development: Infrared photoluminescence (IRPL) is a novel technique, which allows the direct and non-destructive measurement of luminescence emitted by trapped electrons in feldspars (Prasad et al., 2017). IRPL arises from radiative excited state to ground state relaxation of trapped electrons within the principal trap in feldspar.

IRPL measurements enable the investigation of two emissions, one at 880 nm and another one at 955 nm (Kumar et al., 2018, 2021). Whilst most research on IRPL has focussed on understanding the physical processes leading to the IRPL emission in feldspars, yet little is known with regard to the application of IRPL as a dating technique. We build upon a first measurement protocol for sediment dating developed by Kumar et al. (2021) and combine the IRPL measurements with a modified post-IR IRSL protocol (pIRIR₂₂₅ with IR stimulation at 50°C, 90°C, 225°C), which allows a comparison of the IRPL signals with three IRSL signals. This integration of the IRPL measurements in a pIRIR protocol might possibly reduce fading to a negligible level due to the successive IRSL and IRPL measurement steps.

First promising results on loess samples with known (independent) age from the Balta Alba Kurgan loess-paleosol sequence in Romania (Scheidt et al., 2021) will be presented. We conducted dose recovery tests, bleaching experiments and equivalent dose measurements using different test doses and will show first results of fading measurements. The dose recovery tests are within 10% of unity for most of the measurements suggesting sufficient performance of our novel IRPL/pIRIR protocol. However, IRPL equivalent doses seem to slightly underestimate previously measured pIRIR₂₉₀ equivalent doses. Possible reasons will be discussed within the EGU presentation.

References

Kumar, R., Kook, M., Murray, A.S. & Jain, M. (2021). Towards direct measurement of electrons in metastable states in K-feldspar: Do infrared-photoluminescence and radioluminescence probe the same trap? Radiation Measurements 120, P. 7-13.

Kumar, R., Kook, M., & Jain, M. (2021). Sediment dating using infrared photoluminescence. Quaternary Geochronology 62, 101147.

Prasad, A.K., Poolton, N.R.J., Kook, M. et al. (2017) Optical dating in a new light: A direct, non-destructive probe of trapped electrons. Sci Rep 7, 12097.

Scheidt, S., Berg, S., Hambach, U., Klasen, N., Pötter, S., Stolz, A., ... & Nett, J. J. (2021). Chronological assessment of the Balta Alba Kurgan loess-paleosol section (Romania)–a comparative study on different dating methods for a robust and precise age model. Frontiers in Earth Science, 8, 598448.

How to cite: Nett, J. J., Reimann, T., and Riedesel, S.: Luminescence dating of feldspar using a novel infra-red photoluminescence signal – first dating results from loess samples, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2273, https://doi.org/10.5194/egusphere-egu25-2273, 2025.

How to cite: Cui, F., Zhang, H., Liu, J., and Qin, J.: Rock Luminescence Dating Method for Studying the Temporal and Spatial Evolution of the Maying River, Qilian Mountains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3717, https://doi.org/10.5194/egusphere-egu25-3717, 2025.

Dikes are among the most significant ancient human-made earthworks for flood control, land reclamation, and water management for millennia. However, determining the age of dike construction and development based on traditional dating methods (e.g., historical documents, archaeological find materials, and radiocarbon dating), is challenging, due to the paucity of materials and historical records. Luminescence dating may provide an alternative as it uses ubiquitous quartz or feldspar minerals to directly determine the burial age of sediments. In this study, we applied quartz optically stimulated luminescence (OSL) and feldspar single-grain post-infrared infrared stimulated luminescence (pIRIR) dating on two dikes: the Waal dike (near Wolferen-Sprok) in the Netherlands and the Scheldt dike (near Bornem) in Belgium. Our results confirm that luminescence dating provides reliable age estimates, consistent with other independent proxy data such as radiocarbon dating, archaeological artifacts, and historical evidence, and may refine site chronologies. Based on the age results, the history of dike construction and evolution was reconstructed. Additionally, the well-reset OSL signals for dike-related sediments suggest that fresh flood deposits were used for construction. This study highlights the potential of luminescence dating as a robust tool for reconstructing the history of dike construction and understanding ancient engineering.

How to cite: Huang, C., van Beek, R., Chamberlain, E., Wallinga, J., Moree, J., Cruz, F., Laloo, P., and Norde, E.: Reconstructing dike history using luminescence dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4772, https://doi.org/10.5194/egusphere-egu25-4772, 2025.

We use in-situ cosmogenic 10Be in an attempt to date the construction of the Kalasasaya Platform temple at the UNESCO Heritage archaeological site at the ancient city of Tiwanaku, Bolivia. The unique site is located within the altiplano valley of Tiwanaku at 3870 masl near the southern shores of Lake Titicaca. The monuments at Tiwanaku were constructed as ceremonial and civic buildings of exceptional precision and quality by an Andean civilization, who were precursors of the Inca Empire. The date of construction of Tiwanaku is unknown. Earliest settlement is believed to be at least ~3,000 years ago and archeological evidence supports a drought-based empire collapse in the first half of the 12th century. Radiocarbon dating of construction material and other debris range from 300 to 950 AD (ie 1700 to 1050 years ago). At its apogee Tiwanaku is estimated to have extended over an area of as much as 6km2 and to have housed between 70,000 and 125,000 inhabitants.We gained permission to sample the very tops of 3 of the Kalasasaya pillars, and multi-meter sized excavated sandstone blocks and adjacent unmodified bedrock outcrop at a known quarry site which was used for sourcing material for Tiwanaku construction.  The pillars, ~5 meters tall and of square meter section, frame the outer perimeter wall of the 120m square Kalasasaya Platform and are made of andesite and sandstone. Samples at the quarry site, about 15 km distant and at 4300 masl,   were taken from  surfaces of the cavity from where blocks originated, select faces from the extracted blocks and  unmodified  bedrock outcrop. We were able to re-orient extracted blocks back into their original excavated cavity and thus determine pre-excavated buried and post-excavated exposed faces which allowed us to measure how long ago the block was carved out of bedrock and rotated in the process. Our results show that the cosmogenic signal in platform pillar tops is dominated by inheritance but that blocks had been quarried as recently as 1500-3000 tears ago, the age range depending on choice of attenuation length and estimating shielding. Details of sampling, site descriptions and 10Be-age calculations will be presented.

How to cite: Fink, D., Levchenko, V., and Fujioka, T.: Cosmogenic exposure dating the Pre-Columbian archaeological structures at Tiwanaku, Bolivia , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5262, https://doi.org/10.5194/egusphere-egu25-5262, 2025.

U-Th geochronology is a key tool in Quaternary geology, widely applied to carbonate matrices with significant advancements achieved through MC-ICP-MS technology. However, ²³⁰Th dating remains challenging for samples with low-uranium concentrations and high-detrital thorium content which often reflecting open-system behavior. These factors increase uncertainties in age calculations. This study introduces an optimized U-Th dating methodology that integrates refined wet chemistry protocols and 10¹³-ohm amplifiers, significantly reducing expanded uncertainties.

The study employs a four-step validation process: i) testing 10¹³-ohm amplifiers using the NBL U-reference material (CRM 112A), and Th-reference material (IRMM035) of IRMM, ii) application to low-U (10–15 ppb) speleothem samples from the Cueva Fantasma (Atapuerca paleontological-archeological site, Burgos, Spain), iii) analysis of open-system shell samples from Turkey, iv) analysis of the internal speleothem standard (BSS2) of CENIEH.

Initial results using CRM 112A and IRMM035 reveal a tenfold improvement in signal-to-noise ratios with the 10¹³-ohm amplifiers. This configuration enables the use of Faraday cups instead of SEM detectors for U and Th-standard analyses, even at very low intensities (0.002–0.007V), a critical improvement for minimizing uncertainty budgets during bracketing sequences in U-Th dating. Comparative analyses of real samples from Atapuerca, Turkey, and the CENIEH speleothem standard (BSS2) show that the refined methodology reduces U-Th age uncertainties from 2–3% to 0.5–1%.

Beyond improved precision for younger, low-U samples, the method reduces the required sample size from ~100-150 mg to 40–50 mg, substantially lowering the influence of detrital Th contamination. The broader significance of this optimized approach lies in its application to environmental reconstruction during the Quaternary, offering robust tools for deciphering climate archives, paleoenvironments, and archaeological contexts.

How to cite: Hasözbek, A., Pourmand, A., Sharifi, A., Isabel Ortega, A., Parés Casanova, J., Vallverdú Poch, J., and Constantin, S.: Optimized U-Th Chronometry for Carbonates Using MC-ICP-MS: Advancements in Precision and Applications, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6277, https://doi.org/10.5194/egusphere-egu25-6277, 2025.

Past climate and environmental changes can be reconstructed using paleoclimate archives such as ice cores, lake and marine sediment cores, speleothems, tree rings and corals. The dating of these natural archives is crucial for deciphering the temporal sequence of events and rates of change during past climate changes. It is also essential to provide quantified estimates of the absolute and relative errors associated with the inferred chronologies. However, this task is complex since it involves combining different dating approaches at different paleoclimatic sites and often on different types of archives. Here we present Paleochrono-1.1, a new probabilistic model to derive a common and optimised chronology for several paleoclimatic sites with potentially different types of archives. Paleochrono-1.1 is based on the inversion of an archiving model: a varying deposition rate (also named growth rate, sedimentation rate or accumulation rate) and also, for ice cores, a lock-in-depth of air (since, in the absence of significant surface melt, the air is trapped in the ice at about 50-120 m below the surface) and a thinning function (since glacier ice undergoes flow). Paleochrono-1.1 integrates several types of chronological information: prior knowledge of the archiving process, independently dated horizons, depth intervals of known duration, undated stratigraphic links between records, and, for ice cores, Δdepth observations (depth differences between events recorded synchronously in the gas and solid phases of a certain core). The optimization is formulated as a least-squares problem, assuming that all probability densities are near-Gaussian and that the model is nearly linear in the vicinity of the best solution. Paleochrono-1.1 is the successor of IceChrono, which produces common and optimized chronologies for ice-cores. Paleochrono-1.1 outperforms IceChrono in terms of computational efficiency, ease of use, and accuracy. We demonstrate the ability of Paleochrono-1.1 in an experiment involving only the MSL speleothem in Hulu Cave (China) and compare the resulting age model with the SISALv2 age models. We then demonstrate the multi-archive capabilities of Paleochrono in a new ice-core–speleothem dating experiment, which  combines the Antarctic Ice Core Chronology 2023 dating experiment, based on records from five polar ice cores, with data from two speleothems from Hulu Cave dated using uranium/thorium radiometric techniques. We analyse the performance of Paleochrono-1.1 in terms of computing time and memory usage in various dating experiments. Paleochrono-1.1 is freely available under the MIT open-source license.

How to cite: Parrenin, F., Marie, B., Christo, B., Emilie, C., Ellen, C., Drysdale, R., Kawamura, K., Landais, A., Mulvaney, R., Oyabu, I., and Rasmussen, S.: The Paleochrono-1.1 probabilistic model to derive a common age model for several paleoclimatic sites using absolute and relative dating constraints, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6728, https://doi.org/10.5194/egusphere-egu25-6728, 2025.

While highly desired, it remains a challenge for luminescence dating to determine high doses, hence high ages (e.g., >300 ka). The challenge is to project a natural dose close to saturation to a dose-response curve generated with high laboratory doses. The single saturating exponential (SSE) function mostly delivers poor fits to this type of dose responses. Other functions, e.g., the single saturating exponential plus linear function, are then often employed, but these include constants that have no direct physical meaning. Such an approach is inconsistent with the OSL/IRSL measurement parameters (e.g. detection wavelength) by which the signal from a dosimeter’s specific trap-hole pair is targeted out of a broad light spectrum. It is therefore beneficial to employ a physically based model that allows to interpret observations obtained from high laboratory dose responses.

Here we employ the analytical expression, Lambert W, developed by Pagonis et al. (2020) which is an exact solution of the well-studied OTOR (one trap one recombination centre) model, and extended by Lawless and Timar-Gabor (2024) to the OTORX model. We compare results obtained from SSE fits, in particular the characteristic saturation dose (“D₀”) parameter, with those obtained from the OTOR(X) functions. Well-bleached fine-grained polymineral samples irradiated up to ~5000 Gy were used and measured using the pIRIR₂₂₅ protocol.

For the SSE function the results point to the 80% rule of thumb: at ca 80% of the saturation dose the SSE-fitted dose response tend to underestimate the natural dose. The OTOR(X) functions reveal that this is due to the ratio of trapping rate versus recombination rate of free electrons which changes as the regenerated dose response approaches saturation. Consequently, the shape of the dose response curve flattens out in a way that the SSE function is unable to predict. We show here how the change of shape affects the dose interpolation point and how the accuracy of dose estimate is tested using the 63% (D₀) and 80% dose values. We conclude that the OTOR(X) functions provide accurate estimates of natural doses close to saturation.

How to cite: Mauz, B., Kreutzer, S., and Lawless, J. L.: Using OTOR(X) fit functions to improve estimation of high natural luminescence doses, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8761, https://doi.org/10.5194/egusphere-egu25-8761, 2025.

The chronology of Late Glacial and Early Holocene dune formation and wildfire activity at the Łaskarzew site, eastern Poland, was established using AMS radiocarbon (¹⁴C) and optically stimulated luminescence (OSL) dating. Situated within the European Sand Belt, the profile preserves 13 aeolian-soil cycles characterised by alternating phases of aeolian deposition, soil formation, and wildfire episodes, demonstrating the dynamic response of aeolian systems to short-term climatic oscillations. A total of 26 charcoal samples, collected from palaeosols and charcoal layers, were radiocarbon-dated, and cross-referenced with OSL ages of quartz grains, resulting in a robust chronological framework. Dune formation began during the Oldest Dryas, with intensified aeolian activity and four wildfire events recorded during the Allerød interstadial, a period marked by rapid vegetation regeneration and recurring fire episodes. The absence of Younger Dryas sediments reflects extreme environmental conditions, including aridity, limited vegetation, and intensified aeolian erosion. The Holocene sequence, enriched with charcoal-rich deposits, records nine independent wildfire episodes over approximately 4500 years, linked to warm climatic conditions that favoured the expansion of fire-prone pine forests and shaped dune environments. Aeolian activity persisted through this period, accumulating approximately three metres of sediment, before ceasing around 7 ka BP as vegetation stabilised the landscape. The integration of radiocarbon and luminescence dating techniques provided a detailed Late Quaternary chronology, offering valuable insights into the interplay of fire, vegetation, and aeolian processes within the European Sand Belt.

How to cite: Piotrowska, N., Moska, P., Sokołowski, R. J., Poręba, G., Zieliński, P., Mroczek, P., Łopuch, M., Jary, Z., Ustrzycka, A., Wojtalak, A., Szymak, A., Tudyka, K., Raczyk, J., Krawczyk, M., Adamiec, G., and Skurzyński, J.: Reconstructing Late Glacial–Early Holocene dune formation and wildfire dynamics using radiocarbon and OSL dating: Łaskarzew, Poland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12582, https://doi.org/10.5194/egusphere-egu25-12582, 2025.

The Middle Palaeolithic site of Chez-Pinaud in Jonzac (SW France) provides an unparalleled insight into the hunting and butchering behaviour of Neanderthals from ~60 ka ¹ ago. Excavations in the late 1990’s and early 2000’s uncovered a 6-meter sedimentary sequence comprising apparently alternating thin sterile layers and artefact-rich deposits, hosting densely packed accumulations of large ungulate bone fragments and lithics of the Quina Mousterian industry ² . These periodic deposits suggest repeated occupation and abandonment of the site, where Neanderthals were not inhabiting for long periods.  Despite these observations we are still limited in a obtaining a full occupational history of the site, predominantly due to limitations in existing dating methods.

In this study a novel sampling approach was applied to improve the chronological resolution of this site, combining high-resolution Optically stimulated luminescence (OSL) dating and Bayesian modelling. A 40 x 40 x 40 cm sediment block was removed from the main Quina-bearing layer (Layer 22 ²). Under controlled orange light at the RenDaL OSL laboratory at Université de Rennes, the block was carefully excavated by scraping away sediment in horizontal layers. Coordinates of artefacts were recorded and samples for OSL dating were collected at ~1 cm intervals down the block.  Single-grain quartz OSL data were analysed using the BayLum R package ³, incorporating Bayesian statistical modelling to reduce age uncertainties and to investigate the models capacity to handle OSL ages in close temporal and spatial distribution.

Our results indicate that the top of the section represents more modern deposits (~2 ka), which are void of bone fragments. These ages suggest sediment mixing from surface disturbances such as collapsing limestone or anthropogenic activities. Beyond this modern layer, two artefact-rich occupational layers separated by a thin sterile layer are identified through plotting the 3D distribution of the artefacts. The corresponding Bayesian ages for these layers vary between 58 – 80 ka, and do not increase linearly with depth and are thus difficult to correlate directly with the individual artefact bearing layers. These varying ages raise questions over dose rates when we consider the complexity of the heterogeneous sediments in the block. Continuing modelling will be conducted with BayLum as well as further investigation into the dose rate of the samples in attempts to further investigate and increase precision of the ages.

This work underscores the value of combining precise excavation methods with Bayesian analytical approaches for OSL data to construct precise chronologies, especially in important prehistoric archaeological contexts which host well preserved and challenging chronologies.

References:

¹ Richter, D. et al. Thermoluminescence dates for the Middle Palaeolithic site of Chez-Pinaud Jonzac (France). Journal of Archaeological Science 40, 1176–1185 (2013).

² Airvaux, J. & Soressi, M. Le site paléolithique de chez-Pinaud à Jonzac, Charente-Maritime. Prehistoire du Sud-Ouest 8, (2004).

³ Philippe, A., Guérin, G. & Kreutzer, S. BayLum - An R package for Bayesian analysis of OSL ages: An introduction. Quaternary Geochronology 49, 16–24 (2019).

How to cite: Sellwood, E., Malservet, H., and Guérin, G.: Investigating the cyclicity of Neanderthal occupations at Chez-Pinaud, SW France, using high-resolution OSL dating and Bayesian analysis., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12656, https://doi.org/10.5194/egusphere-egu25-12656, 2025.

Continental sedimentary deposits are essential geological records for understanding landscape evolution over time. In this context, the “modern analog” approach is employed in the Andes-Amazon system to deepen the understanding of past changes and the factors influencing them. This methodology involves studying contemporary fluvial deposits using advanced techniques and methods to identify how natural processes shape the current landscape. The main objective of this study is to determine the spatial variability and environmental controls of the sediment provenance and the erosion rates in modern deposits of the Ucayali, Maranõn, Napo, Madre de Dios, Huallaga, and Solimões rivers in the Andes-Amazon fluvial system. This approach will involve luminescence sensitivity signatures of quartz and feldspar grains, which can indicate grain source and transport process; the latitudinal gradient of erosion rates using in situ cosmogenic nuclides; the relationship between sedimentary variability and tectonic, topographic, lithologic, and climatic controls using Geographic Information Systems (GIS). The new cosmogenic nuclide and luminescence data will be used together to evaluate the compatibility of these methods in analyzing sediment provenance and erosion rates. This comparison will assess whether these methods and approaches can be consistently integrated, contributing to a more comprehensive understanding of sedimentary and erosive processes in the Andes-Amazon fluvial system. (FAPESP #2023/16318-1)

How to cite: Brandino de Campos, G., Barbosa Leite Cruz, C., Emerich Souza, P., Luísa Souza Simões, A., Breda, C., Cassimiro Brito, R., Bookhagen, B., Oliveira Sawakuchi, A., and Nascimento Pupim, F.: Sediment provenance and erosion rates in the Andes-Amazon fluvial system: a study using luminescence and cosmogenic nuclides technics, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12755, https://doi.org/10.5194/egusphere-egu25-12755, 2025.

Since the 19^th century, various authors have assigned the glacial landforms in the lower valleys of northern Italy to different ice ages (Penck and Brückner 1909). This study was part of a project that involved a broad geomorphological analysis and the first-time absolute in-situ exposure dating of erratic boulders using ¹⁰Be and ³⁶Cl (Braakhekke et al. 2020). In addition to the cosmogenic analysis, seven radiocarbon samples were taken from a fluvial terrace outcropping 6 meters high along the Ticino River. Where possible, the samples were sieved to separate a bulk fraction (<125 μm) from the undefined organic fragments. Some samples were partly dissolved during the subsequent ABA preparation of all fractions. This way, we obtained up to four ages per initial sample: one each for the insoluble bulk fraction, the humic acid of the bulk, the organic fragments, and the humic acid of the organic fragments. The obtained radiocarbon ages vary significantly, with the extreme being thousands of ¹⁴C years between the insoluble bulk fraction and the organic fragments for the same sample. For all samples, radiocarbon analysis of the bulk fractions gave much younger ages than the hand-selected macro remains. Here, we discuss the age differences and possible sources of old and young carbon found in samples. The ages of the organic fragments showed the most consistency over the whole profile, and these fragments are least likely contaminated by younger material. Based on our results obtained on macro remains, this deposit is dated to MIS3 age. About 3 meters of fine-grained sediment were deposited here during ca. 8 ky. This could tell us more about the sediment budgets during some of the (Greenland) stadial-interstadial oscillations at the outlet of a major lake (e.g., Lake Maggiore) and the erosive power of glaciers during a phase preceding the global Last Glacial Maximum.

References

Braakhekke J, Ivy‐Ochs S, Monegato G, Gianotti F, Martin S, Casale S, and Christl M. 2020. Timing and flow pattern of the Orta glacier (European Alps) during the last glacial maximum. Boreas 49: 315-332.

Penck A, and Brückner E. 1909. "Die alpen im Eiszeitalter." Tauchnitz.

How to cite: Hajdas, I., Braakhekke, J., Monegato, G., Gianotti, F., Christl, M., and Ivy Ochs, S.: Different 14C ages for various fractions of peat, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12806, https://doi.org/10.5194/egusphere-egu25-12806, 2025.

Anthropogenic carbonates such as lime mortars and plasters have been receiving growing attention as they are an invaluable source of information for archaeologists, conservators, and restorers of cultural heritage. Taking into account the production process, the age of mortars reflects the age of the building. Two physical dating methods currently enable us to date mortars: radiocarbon (¹⁴C) dating and optically stimulated luminescence (OSL). Fast development in ¹⁴C and OSL mortar dating naturally widens the scope of performed analysis, and promotes the search for different methods which may be applied to these materials. In this study we present the analysis of historical lime mortars in order to assess the possibility of future dating by Electron Spin Resonance (ESR) spectroscopy. ESR dating has been applied to various geological and archaeological materials, but there are virtually no examples of dating carbonates younger than 10 000 years. Since carbonate crystals are formed during the mortar production, this moment can be regarded as the zero point for the accumulation of trapped charges, and their concentration in a measured sample should reflect the age of the mortar.

Our previous works on samples from Sveta Petka church in Budinjak, Croatia, and an ancient settlement Hippos, Israel, show the growth of signals related to the paramagnetic centres with the dose of laboratory radiation. However, in order to obtain the age of the samples the natural material should exhibit measurable ESR signals of the centres suitable for dating. In the relatively young (as far as ESR dating is concerned) materials the signals are very weak, however detailed analyses showed presence of such signals in several investigated mortar samples. In this work we investigate ESR signals in natural and laboratory-irradiated carbonate lime binders from several different archaeological sites, with ages ranging from about 2000 to 500 years old. The samples have been previously dated by ¹⁴C method, which means they had undergone extensive characterisation and preparation, ensuring the selection of binder, which reflects the true age of the mortar. We analyse the spectra with the aid of ESR simulations in order to identify the paramagnetic centres present in the samples, and compare them to the centres commonly found in carbonates and used for ESR dating. The goal of this work is a qualitative analysis of the natural signals found in a variety of mortars, assessing their potential suitability for ESR dating. This study is a first part of the ongoing project focused on establishing ESR as a method of dating anthropogenic carbonates in a form of lime mortars, and comprises the preliminary analysis of the subject, which will be followed by future in-depth studies.

How to cite: Kabacińska, Z. and Michalska, D.: Towards Electron Spin Resonance dating of anthropogenic carbonates: ESR signals of 14C-dated historical lime mortars, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13244, https://doi.org/10.5194/egusphere-egu25-13244, 2025.

We have studied the loess-palaeosol sequences of the Khovaling Loess Plateau in Tajikistan, which form the most complete record of subaerial sedimentation in Central Asia. Studied sections contain several layers with Early and Middle Palaeolithic tools, and therefore record some of the earliest events of hominin dispersal into Central Asia.

As part of a major NordForsk funded project ‘Timing and Ecology of the Human Occupation in Central Asia’ (THOCA; www.thoca.org), we applied high-resolution luminescence dating to the upper parts of three sections of Khovaling loess plateau (Khonako-II, Kuldara, and Obi-Mazar) in order to: (1) provide an independent timescale for palaeoclimatic studies; (2) assess the completeness of the sedimentary record; and (3) investigate the main stages of dust accumulation over this interval.

The luminescence chronology extends back to ~250 ka and reveals distinct erosional hiatuses ranging in duration from ~7 ka to a full glacial-interglacial cycle (~100 ka). Some of these breaks were not identifiable in the field. These discontinuities had not been previously recognized, potentially leading to significant errors in palaeosol identification and, consequently, in the presumed chronology. Now, we have a better understanding of the aeolian sedimentation in the region and the stages of loess/palaeosol formation. The new chronology provides a reliable correlation of regional features with global events and relates them to climate change, soil cover development, and the evolution of Early and Middle Paleolithic.

How to cite: Taratunina, N., Buylaert, J.-P., Challier, A., Murray, A., Sosin, P., and Kurbanov, R.: High resolution luminescence dating of the Khovaling Loess Plateau sites (Tajikistan), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13277, https://doi.org/10.5194/egusphere-egu25-13277, 2025.

Surface and buried paleosols are a significant archive of information about environmental change and are widely used in paleogeographic reconstructions. Soil features and their profiles change over time as a result of environmental change. The soil memory is the palimpsest-like, as opposed to the book-like, sedimentary record (Targulian and Goryachkin, 2004). The palimpsest-like memory of the soil requires informed and well-adapted strategies for deciphering and interpreting the information it contains. The question of soil age and its synchronization with reconstructed events remains one of the most controversial issues in paleosol interpretations. The complexity of the interpretation of obtained radiocarbon dates is related to the heterogeneous and heterochronous of soil organic matter (SOM). At present, there are many approaches to dating SOM, but for the paleosol for paleogeographic reconstructions, ¹⁴C dating is most often performed on total organic carbon (bulk carbon). This choice of dating fraction is usually related to the poor preservation of SOM and its low carbon concentration in paleosols. Dates obtained for SOM in buried soils are based on the assumption that SOM was formed "in situ". However, due to various natural processes, paleosols can contain carbon from a number of potential sources.
For buried soils formed in periglacial landscapes, a significant source of carbon is the supraglacial material: cryoconites and other organo-mineral formations that form on the surface and in the body of the glacier and enter the landscape during glacial melting. Our studies on glaciers and in periglacial landscapes of different natural zones (Svalbard, Franz Josef Land Archipelago, Polar Urals, Altai, Kamchatka) have shown that supraglacial material can have a radiocarbon age ranging from modern to very ancient (several thousand, sometimes tens of thousands of years). The largest dataset we have obtained for supraglacial objects is represented by carbon pools aged 1000 to 10,000 radiocarbon years, BP and >10,000 radiocarbon years, BP. The pool with an age of >10,000 radiocarbon years is associated with the presence of a "dead carbon" source near the studied glacier. Dates in the range of 10,000-20,000 radiocarbon years may also reflect the age of soils and sediments formed during the last deglaciation and buried within the body of the glacier as it advanced. Soils formed in the periglacial zone inherit the isotopic composition of SOM from supraglacial material and become carriers of "apparent" / inherited ¹⁴C age. The presence of cryoconite material in buried paleosols can be diagnosed by studying their micromorphology and identifying morphological structures characteristic of cryoconites. We have shown this for soils formed on cryoconite material in Svalbard and for lenses of buried fine-grained material in marginal glacial formations (Keiva) on the Koly Peninsula.  When ¹⁴C dating paleosol series (traditional paleoarchives are studied in foothills and mountainous areas), it is necessary to consider the ice-carbon contribution to SOM in order to make correct paleo-reconstruction.

How to cite: Zazovskaya, E., Mergelov, N., Dolgikh, A., Turchinskaia, S., Dobryanskiy, A., and Bronnikova, M.: “Ice carbon” as a possible source of apparent age in paleosol dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14514, https://doi.org/10.5194/egusphere-egu25-14514, 2025.

Abstract: The SAR-SGC method, integrating single aliquot regenerative (SAR) and standardised growth curve (SGC) protocols with advantages of saving machine measurement time. It has gained widespread application in recent years over diverse sediment types, including glacial, aeolian, fluvial, lacustrine, deltaic, and marine sediments. The method constructs inter-aliquot SGCs using conventional SAR measurements and determines SGC D_es by inserting the L_N/T_N values of additional aliquots into the SGC. The final SAR-SGC De is obtained by calculating the arithmetic mean of the SAR D_es and SGC D_es. However, the optimal number of SAR and SGC aliquots for reducing machine time while retaining precision, is still ambiguous. To address this issue, we systematically investigated how varying the number of SAR aliquots and additional L_N/T_N​ measurements influences the stability and consistency of equivalent dose derived from SAR-SGC method with SAR protocol. We examined the minimal SAR-SGC combinations for three samples (JNZK01-G09, MW10-G16 and XBG06-G07, with an equivalent dose of ~44 Gy (with largest scatter in inter-aliquot SAR growth curves), ~46Gy and ~55Gy (with marginal scatter in inter-aliquot SAR growth curves) in the lower Yellow River plain, utilizing a Risø TL/OSL-DA-20 reader with a 90Sr/90Y beta source. Through extensive statistical evaluations, SAR-SGC estimation of the equivalent dose obtained with differing aliquot combinations shows that equivalent dose could be accurately estimated within acceptable uncertainty (<10%) using 6–15 SAR aliquots and additional 12–30 L_N/T_N aliquots. For samples with dispersed growth curves, we recommend a minimum of 6 SAR and 12 L_N/T_N aliquots for reliable age determination. And samples with concentrated growth curves may suffice with 4 SAR and 10 L_N/T_N aliquots. This study demonstrates that the combined SAR-SGC method significantly reduces machine time (at least 70%) compared to the SAR protocol alone while maintaining acceptable precision. These findings provide valuable guidance for luminescence dating laboratories and researchers in optimizing instrument usage under time constraints.

Key words: SAR-SGC method; Standardized growth curve; Single aliquot regenerative protocol; Equivalent dose; Luminescence dating; Statistical analysis; Machine time optimization

How to cite: Zhou, X., Liu, Y., Feng, X., and Lai, Z.: Performance of SAR-SGC method for equivalent dose determination of quartz OSL, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15342, https://doi.org/10.5194/egusphere-egu25-15342, 2025.

Stone fish traps and weirs are the most common archaeological remains in fluvial and coastal environments. In Brittany, almost 800 of them were identified by Daire and Langouët (2014). Usually, these are made of numerous erected stones, that more or less precisely outline an alignment. Dating these remains represents a real archaeological issue, since stone fish traps have been raised for millennia, presumably from the early Neolithic to the Middle Ages. However, it is also a challenge as there is no organic matter preserved in the core of these structures.

In this presentation, we assess the age of fish weirs found in Brittany by comparing their altitude with the sea-level rise estimation curve since the last glaciation 20 000 years ago. A software named CHRONOE was developed in R in order to improve the reliability of the data, among which tidal curves (García-Artola et al. 2018). Statistical analysis – using the R package ArchaeoPhases (Philippe and Vibet 2020) – of the ages determined by CHRONOE for a corpus of    diverse stone fishing weirs, identifies periods of intensification and rarefaction of fishing using such structures. Thus, it is possible to discuss the evolution of fishing practices in human societies along the coasts of Brittany.

This work is the first step of a PhD Thesis; it will be followed by direct dating of stone fish traps. Indeed, rock surface luminescence dating \autocite{soh12} has been shown to reliably estimate the last time a rock surface was exposed to light (Sohbati et al. 2012) has been shown to reliably estimate the last time a rock surface was exposed to light (Freiesleben et al. 2015). Therefore, it will be applied to a few of these structures, after careful selection based on their presumed age. The bottom surface of sampled rocks from fish weirs will be sampled for OSL intensity profiling and burial dating. The numerical absolute ages given by obtained with OSL will then be compared to those assessed with CHRONOE, to discuss the reliability of the underlying assumptions and refine the model. Eventually, CHRONOE may hold the potential to date any submerged object whose utility (or existence) is linked with the intertidal zone.

Keywords : geochronology, OSL, archaeology, fish weirs.

References

Daire, M.-Y., & Langouët, L. (2014). Se nourrir le long des côtes bretonnes : Réflexions à partir d'une analyse diachronique des barrages de pêcheries. Actes des congrès nationaux des sociétés historiques et scientifiques, 138 (2), 105133.

Freiesleben, T., et al. (2015). Mathematical model quantifies multiple daylight exposure and burial events for rock surfaces using luminescence dating. Radiation Measurements, 81, 1622.

García-Artola, A., et al. (2018). Holocene sea-level database from the atlantic coast of europe. Quaternary Science Reviews, 196, 177192.

Philippe, A., & Vibet, M.-A. (2020). Analysis of archaeological phases using the R package ArchaeoPhases. Journal of Statistical Software, 93, 125.

Sohbati, R., et al. (2012). Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating. Journal of Geophysical Research: Solid Earth, 117, 2012JB009383.

How to cite: Jumaucourt, A., Guérin, G., Le Bris, D., Stephan, P., Bernier, I., and Pailler, Y.: A way to date stone fish weirs ? Some perspectives., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19154, https://doi.org/10.5194/egusphere-egu25-19154, 2025.

Holocene sedimentary sequences lacking organic remnants or containing redeposited organic material pose a challenge for detailed chronological investigations, as radiocarbon dating is unsuitable. Optically stimulated luminescence (OSL) can be used instead, but high-resolution OSL is costly. A more cost-effective and efficient approach involves the combination of low-resolution OSL dating with portable OSL (pOSL) profiling in 5–10 cm increments (e.g. Sanderson and Murphy, 2010; Brill et al. 2016). This method has been employed in the analysis of cored lacustrine sedimentary sequences from the northern shore of Lake Schweriner See, Germany.

In well-bleached Holocene sediments, quartz equivalent doses and portable post-infrared blue-light stimulated luminescence signals (further pOSL) from the polymineral fraction are linearly correlated (e.g. Brill et al., 2016). We used the obtained linear functions to estimate equivalent doses (D_es) in quartz for each pOSL signal. The dose rates were then interpolated between full OSL samples, and the ages were calculated by dividing the D_es by the corresponding dose rates. Finally, both the quartz full OSL ages and the ages derived from the pOSL signals were incorporated into a Bayesian age-depth model to obtain a continuous chronology.

The pOSL-to-D_e ratio is also a useful tool in the identification of incompletely bleached samples. Poorly bleached sediments exhibit a higher pOSL-to-D_e ratio in comparison to well bleached sediments because pOSL is a composite of signals from quartz and feldspars, which require a greater exposure time for complete bleaching than OSL from pure quartz (e.g. Murray et al., 2012). In the littoral sequences studied, elevated pOSL-to-D_e ratios were found to correspond with high quartz D_eoverdispersion (OD), which is another indicator of poor bleaching. One particular sample was observed to exhibit a high pOSL-to-D_e ratio yet low OD (15%), which may be attributed to distinct OSL sensitivity linked to a specific sediment source.

Our results demonstrate that the proposed approach suits littoral sediments and improves chronological frameworks for lacustrine sequences. A potential avenue for further refinement of age-depth models lies in the measurement of dose rates for all pOSL samples, as opposed to their estimation through interpolation.

References

Brill, D., Jankaew, K., & Brückner, H. (2016). Towards increasing the spatial resolution of luminescence chronologies – Portable luminescence reader measurements and standardized growth curves applied to a beach-ridge plain (Phra Thong, Thailand). Quaternary Geochronology, 36, 134–147.

Murray, A. S., Thomsen, K. J., Masuda, N., Buylaert, J.-P., & Jain, M. (2012). Identifying well-bleached quartz using the different bleaching rates of quartz and feldspar luminescence signals. Radiation Measurements, 47(9), 688–695.

Sanderson, D. C. W., & Murphy, S. (2010). Using simple portable OSL measurements and laboratory characterisation to help understand complex and heterogeneous sediment sequences for luminescence dating. Quaternary Geochronology, 5(2–3), 299–305.

How to cite: Ruchkin, M., Lorenz, S., Adolph, M.-L., and Haberzettl, T.: Applying portable OSL to obtain a detailed chronology of littoral sedimentary sequences from the northern shore of Lake Schweriner See, Germany, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21256, https://doi.org/10.5194/egusphere-egu25-21256, 2025.

Magnetotactic bacteria produce biogenic magnetite in aquatic environments with reduced oxygen (O₂) and high Fe concentrations. Increased biogenic magnetite contents in geological archives have been associated with marine deoxygenation, Fe fertilization and productivity. However, these conditions, which depend on amplified nutrient supply to marine settings, enhance organic matter production and subsequent magnetic mineral dissolution due to reductive diagenesis. This suggests that the paleoenvironmental significance of biogenic magnetite content variability remains elusive, and more records are needed to clarify the mechanisms that control the abundance of magnetotactic bacteria biomineralization products in sedimentary records. Accelerated nutrient input from the continents to the oceans and reduced seawater O₂ concentrations are recurrent during global warming events due to temperature controls on both O₂ solubility and hydroclimate. This has motivated the generation of multiple early Eocene biogenic magnetite records, which based on rock magnetic and electron microscopy experiments, have related biogenic magnetite contents with productivity and seawater O₂ variability. Here, we present new geochemical and rock magnetic data from the Contessa Road section (Gubbio, Italy), which records a series of early Eocene global warming events. Our new data reveal that biogenic magnetite content variability cannot be directly used as an index for increased productivity and/or marine deoxygenation; alternatively, it can be seen an index for Fe availability in marine settings. Our observations indicate that biogenic magnetite does not exclusively reveal a specific process, which suggests that its content variability may depend on different local paleoenvironmental conditions.

How to cite: Piedrahita, V., Roberts, A., Rohling, E., Heslop, D., Galeotti, S., Florindo, F., Yan, L., and Li, J.: Biogenic magnetite as an index for Fe availability , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-464, https://doi.org/10.5194/egusphere-egu25-464, 2025.

Marine anoxia events, as indicated by geochemical proxies, have been widely studied as a possible mechanism driving the end-Permian mass extinction, which also inhibited the subsequent biotic recovery. However, redox changes in the aftermath of extinction and their further ecological effects are still controversial. Here, we report the characteristics of rock magnetic changes in several sections of the Permian-Triassic transition in South China and reinterpret the changes in redox conditions during this period. Our study shows that the magnetic mineral assemblages and magnetic characteristics considerably altered in the aftermath of the extinction, implying significant environmental changes. In microbialite sections developed in the shallow-water carbonate platform after the extinction, the variation of magnetic mineral assemblages records the fluctuated redox conditions under oxic and euxinic conditions, which explains the cleavage between continuous oxic or euxinic conditions suggested by paleontological and pyrite framboid evidence in earlier work, respectively. Due to the sensitivity of magnetite and hematite to the redox change, their preservation and the relative change between these two minerals have the potential to reflect the redox state. Hence, we propose a new magnetic proxy to reflect the redox conditions in the ancient ocean. This proxy correlates well with other geochemical redox proxies and the abundance changes of aerobic fossils, supporting its considerable reliability. In all, our study indicates that the microbialites were affected by frequent anoxia events while the photosynthetic oxygen production of cyanobacteria in the microbialites may be the key factor for buffer effect. Under the rapid increase in ocean temperature and an overall seawater oxygen depletion during the Permian-Triassic transition, microbialite and the microbes within it thus provide a more favorable habitat for the surviving metazoans.

How to cite: xiong, W. and wang, T.: Fluctuated redox condition in Lower Triassic microbialite: evidence from magnetic mineral assamblage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-805, https://doi.org/10.5194/egusphere-egu25-805, 2025.

Knowledge of the seismogenic environment of fault zones is critical for understanding the processes and mechanisms of large earthquakes. We conducted a rock magnetic study of the fault rocks and protoliths to investigate the seismogenic environment of earthquakes in the Motuo fault zone, eastern Himalaya syntaxis. The results indicate that magnetite is the principal magnetic carrier in the fault rocks and protolith, while the protolith has a higher content of paramagnetic minerals than the fault rocks. The fault rocks are characterized by a high magnetic susceptibility relative to the protolith in the Motuo fault zone. This is likely due to the thermal alteration of paramagnetic minerals to magnetite caused by coseismic frictional heating with concomitant hydrothermal fluid circulation. The high magnetic susceptibility of the fault rocks and neoformed magnetite indicate that large earthquakes with frictional heating temperatures > 500°C have occurred in the Motuo fault zone in the past, and that the fault maintained an oxidizing environment with weak fluid action during these earthquakes. Our results reveal the seismogenic environment of the Motuo fault zone, and they are potentially important for the evaluation of the regional stability and the selection of major construction sites in the eastern Himalaya syntaxis.

How to cite: Cao, Y.: Rock Magnetic Evidence for the Seismogenic Environment of Large Earthquakes in the Motuo Fault Zone, Eastern Himalaya Syntaxis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1274, https://doi.org/10.5194/egusphere-egu25-1274, 2025.

The 2024 Ma Vredefort (South Africa) impact structure comprises a 40-50 km central region of Archean basement rocks surrounded by a 15-20 km wide collar of late Archaean to early Proterozoic Witwatersrand Supergroup sedimentary and volcanic rocks. The collar is characterized by a ring of prominent, negative (<-5,500 nT) aeromagnetic anomalies surrounding much of the structure where the strata dip near-vertical to overturned. To better understand the origin of this magnetic feature, we undertook a ground magnetic survey throughout the Vredefort structure using a three-axis fluxgate magnetometer mounted on a mountain bicycle. The upward continuation of our profiles to 150 m matches the aeromagnetic data in shape and amplitude. The near-ground magnetic measurements allowed us to pinpoint the rocks responsible for the intensely negative anomalies. Field observations and microfabric analyses of six outcrops confirmed that the magnetic signal correlates with specific metamorphosed banded iron formations (BIFs) at the base of the supergroup, 10 to 100 m thick, as the main producer of the strongly negative magnetic anomalies. Paleomagnetic samples collected from the rocks at the surface that produce the most intense anomalies (up to -22,000 nT) have extremely high natural remanent magnetization intensities (up to >1000 A/m) likely arising from lightning strikes. Stepwise demagnetization and rock magnetic experiments distinguish one site as likely having escaped remagnetization from lightning that possesses the established 2.02 Ga paleodirection at Vredefort. Thermoremanent magnetizations (TRM) imparted on 41 samples using a 40 μT field yielded an average intensity of 25 A/m. Using the results of TRM experiments and the paleodirection enabled us to successfully model the prominent negative anomalies in the metasediments only when accounting for the post-impact orientation of the BIFs. We interpret the strongly negative magnetic anomaly in the collar region as being formed directly after crater exhumation and uplift of the rocks. This interpretation implies that Bushveld-related metamorphism created the up to mm-sized magnetite and garnet crystals in the BIFs, which resided at temperatures higher than the Curie temperature of magnetite (580°C) until the impact rapidly brought the BIFs close to the surface where magnetite cooled to acquire a thermal remanence in the 2.02 Ga field.

How to cite: Sleptsova, I., Gilder, S., Le Goff, M., Dellefant, F., Trepmann, C., Lhuillier, F., and Webb, S.: Explaining the Intensely Negative Magnetic Anomalies in the Vredefort Impact Structure, South Africa, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4372, https://doi.org/10.5194/egusphere-egu25-4372, 2025.

Understanding how human activities mitigate the negative impacts of climate change and promote sustainable development is a critical scientific question (e.g., Lamb and Steinberger, 2017). Throughout history, humans have made many attempts to adapt to climate change, particularly through their adoption of settlement environments and the evolution of building materials (e.g., Olsson, 2024). The controlled use of fire, a hallmark of human civilization, has been instrumental in developing ceramic building materials since the Neolithic period (e.g., Jones, 2021). While numerous burned clay artifacts from the Neolithic period have been found worldwide (e.g., Pérez-Monserrat et al., 2022), little is known about their detailed characteristics and the potential influence of climate change on artificial fire usage. This study focuses on a Neolithic site in eastern Fujian, South China. By magnetic and geochemical analysis, we aim to reconstruct the firing temperatures and, consequently, the technological characteristics of artificial fire used in Neolithic house construction in the context of climate change. Magnetic results suggest an average ancient firing temperature of approximately 620°C, consistent with findings from other Eurasian Neolithic sites (e.g., Jordanova et al., 2020). The magnetic properties of burnt clay may reflect the characteristics of the in-situ clay source, offering insights into the geological background. However, the artificially controlled fires result in differences in the structure, geochemical characteristics, and color of the various layers of the burned clay. Furthermore, a potential link between temporal variations in ancient firing temperatures and surrounding paleoenvironmental changes is suggested, potentially influenced by feedback mechanisms between temperature-moisture conditions and human activities. In addition, this study would potentially contribute to further studies on artificial fire usage evolution in cultural relics from an interdisciplinary perspective under specific environmental conditions.

References

Jones, R., 2021. The Decoration and Firing of Ancient Greek Pottery: A Review of Recent Investigations. Advances in Archaeomaterials. 2, 67–127.

Jordanova, N., Jordanova, D., Lesigyarski, D., et al., 2020. Imprints of paleo-environmental conditions and human activities in mineral magnetic properties of fired clay remains from Neolithic houses. Journal of Archaeological Science: Reports. 33,102473.

Lamb, W. F., Steinberger, J. K., 2017. Human well‐being and climate change mitigation. Wiley Interdisciplinary Reviews: Climate Change. 8(6): e485.

Olsson, O. 2024. Human Capital Evolution in a Cooling Climate[M]//Paleoeconomics: Climate Change and Economic Development in Prehistory. Cham: Springer Nature Switzerland. 39-58.

Pérez-Monserrat, E. M., Causarano, M., Maritan, L., et al., 2022. Roman brick production technologies in Padua (Northern Italy) along the Late Antiquity and Medieval Times: Durable bricks on high humid environs. Journal of Cultural Heritage. 54,12-20.

How to cite: Li, G., Chen, G., Cheng, Z., Huang, Y., Fang, J., Ge, W., and Zhan, C.: Magnetic Constraints on the Role of Artificial Fire in Neolithic Burnt Clay in Southern China under Climatic Impacts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5355, https://doi.org/10.5194/egusphere-egu25-5355, 2025.

Néel's theory of single domain magnetizations has been widely applied in paleomagnetism since its conception in the 1940s. When applying this theory, paleomagnetists typically assume that all magnetic particles are composed of magnetite, and are shaped like highly elongate needles. Even in the SD size range, natural samples exhibit a much wider range of morphologies, causing a gap between theory and experiments. Although these assumptions were necessary in the 1940s, computing power today means they are no longer required.

To understand the behaviour of other types of SD particles, we have created a new software package called the Single Domain Comprehensive Calculator (SDCC). The SDCC can derive the magnetic properties of SD particles from first principles, without making the assumptions of Néel. The package provides a simple python scripting interface to simulate almost any paleomagnetic experiments, with assemblages of particles of different sizes, shapes and compositions.

Simulations with the SDCC show that single domain particles exhibit a much wider range of experimental behaviour than has previously been discussed. In particular, we show that the relationship between blocking temperature and relaxation time is strongly dependent on the shape and composition of the particle. This causes viscously acquired remanences to unblock over a wide range of temperatures on laboratory timescales. To demonstrate this, we ran a simulation where an assemblage of SD particles acquired a viscous overprint over a primary thermal remanence. On simulated thermal demagnetization, the two magnetizations exhibited overlapping unblocking spectra, which would lead to problematic behaviour in paleomagnetic experiments.

How to cite: Cych, B., Paterson, G., Nagy, L., and Williams, W.: PSD: Possibly Single Domain?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10133, https://doi.org/10.5194/egusphere-egu25-10133, 2025.

 Toxic metal content testing, environmental magnetic monitoring and in vitro bioaccessibility experiments each have their own advantages and are often used independently for environmental monitoring, but there are few studies that combine the three to evaluate the hazards of toxic metals to humans. This paper investigated the total content, magnetic properties and bioaccessibility of nine potentially toxic metal elements (Zn, Sn, Pb, Cu, Fe, Ni, Cr, Sr, Mn) in dustfall from different functional zones in Shanghai, China, and systematically compared the related results. The results show that these nine metal elements have different degrees of contamination and enrichment in outdoor dustfall, and their content distribution shows the following trend: Zn > Sn > Pb > Cu > Fe > Ni > Cr > Sr > Mn. Magnetic characteristics χ_lf and SIRM are mostly positively correlated with the metal elements, indicating that the higher the content of magnetic minerals in the sample, the higher the concentration of metal elements. It was also found that χ_lf, SIRM, and χ_ARM can well reflect the characteristics of dustfall pollution. The magnetic minerals have a certain degree of enrichment, and the particle size of the magnetic minerals is relatively coarse, mainly in the form of coarse multi-domain and pseudo-single-domain particles, which are largely derived from anthropogenic pollution. The χ_lf and PM10 concentrations in the precipitation show relatively similar spatial trends, so χ_lf, SIRM, and χ_ARM can be used as air pollution indices to facilitate the evaluation of metal elements pollution in dustfall. The overall trend in gastric bioaccessibility is Pb > Zn > Mn > Cu > Cr. Due to the increase in the pH of digestive fluid, the bioavailability of toxic metals decreases significantly from the gastric stage to the intestinal stage. χ_lf, SIRM, and χ_ARM/SIRM are all related to the bioaccessibility of toxic metals in the intestinal stage, so they can be used as toxicity indicators to evaluate the bioaccessibility of toxic metals in dustfall.

How to cite: Wang, G., Yang, F., Wang, Y., Ren, F., Hou, Y., Su, S., and Li, W.: Magnetic response and bioaccessibility of heavy metal pollution inoutdoor dustfall in Shanghai, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10426, https://doi.org/10.5194/egusphere-egu25-10426, 2025.

Marine magnetic anomalies provide fundamental information on plate tectonics, seafloor spreading, and geomagnetic field variations over time. It has long been debated whether the long-term variations of the marine magnetic anomalies are related to records of paleointensity variations or the progressive off-axis hydrothermal oxidation of magnetic minerals in mid-ocean-ridge basalts (MORBs). However, these processes are highly dependent on rock type and textures. Moreover, the style and extent of off-axis low-temperature alteration in MORBs varies and can be pervasive through the rock matrix or localized in vein halos, leading to significant heterogeneities in the upper crust. Studying the magnetic properties of both fresh and altered MORBs from transects covering a range of crustal ages is essential to assess and constrain the factors affecting the origin and evolution of magnetic anomalies.

In this study, we combined rock magnetic investigation with petrography and geochemical data to characterize the magnetic behaviour of basalts formed between ~7 and 61 Ma across the western flank of the Mid-Atlantic Ridge, recovered during the South Atlantic Transect (SAT) ocean drilling expeditions. This transect provides the opportunity to test the influence of primary and secondary factors on the magnetic signature of MORBs.

Our results show the strong influence of primary igneous features on the intensity of the remanent magnetization of MORBs. For example, the grain sizes and concentrations of magnetic minerals change according to different emplacement styles, with finer and coarser-grained magnetite in basaltic pillows and massive lava flows, respectively. Moreover, the combination of rock magnetic and major elements analyses reveals variation in primary and alteration mineral assemblages (clay minerals and goethite), composition (e.g., changes in Ti-content) and grain-size across the alteration halos, which in turn affects the intensity of the magnetic signature.

Overall, the variation of magnetic properties across the ridge flank testifies to a complex interplay of factors such as the nature of volcanic units and the style and evolution of hydrothermal alteration on the nature and long-term variation of the marine magnetic anomalies.

How to cite: Robustelli Test, C., Amadori, C., Harris, M., Belgrano, T., Jonnalagadda, M., Evans, A., Grant, L., Albers, E., Coggon, R., Teagle, D., and Zanella, E. and the The South Atlantic Transect IODP Expedition 390 & 393 Scientists: Unveiling factors affecting the magnetic signature of MORBs and their long-term variation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10493, https://doi.org/10.5194/egusphere-egu25-10493, 2025.

The Moinhos Velhos-Contenda Cave, located in the Estremenho Karst Massif, Central Portugal, is the second-largest and the most visited cave of Portugal. Here we provide new paleomagnetic, rock magnetic and mineralogical data from a stalagmite (GMA-III) collected in Moinhos Velhos Cave, at about ~60m depth. Besides, cave sediments, surface soils and another (clean/whitish) stalagmite (GMA-IV) was collected. This speleothem is mushroom-shaped with dark-reddish laminations, hypothesized to be related to flooding periods. However, how the flooding events are recorded in the calcite laminae of the stalagmite and how the respective conditions affected the quality of the paleomagnetic signal is poorly constrained. After stepwise alternating field demagnetization, the viscous remanent magnetization was cleaned below 10mT, followed by a natural remanent magnetization pointing to the origin. After 100mT, more than 90% of the magnetization was cleaned, suggesting low to medium coercive magnetic minerals as main magnetic carriers of the natural remanence. Sample-based mean directions show an average declination of ~353º and a mean inclination of 38.5º. Isothermal Remanent Magnetization (IRM) curves shows the presence of two components – the first one with a mean coercivity of ~30mT and a DP of ~0.26, typical of pedogenic/detrital magnetite, contributing to ~94% of the total remanence; and the second one with a mean coercivity of ~245mT and a DP of ~0.30, interpreted as being hematite, contributing to ~6% of the total remanence. Plot of k_ARM/IRM versus the mean demagnetization field (MDF) show three distinct clusters, corresponding to the GMA-III and GMA-IV stalagmites, while the third cluster corresponds to the soils and cave sediments. All clusters are close to the pedogenic-detrital zone of the diagram. Notably, the GMA-III stalagmite has significantly lower values of k_ARM/IRM than the GMA-IV stalagmite. Cisowski test on GMA-III samples shows an interaction degree close to 0.5, suggesting the presence of non-interacting single-domain magnetite. Under binocular microscope, the reddish horizons show the presence of opaque materials and dissolution features, suggesting the occurrence of hiatus of precipitation. Analysis of these horizons under scanning electron microscopy (SEM) coupled to energy dispersive spectra show the presence of large (~50-100 micrometers) crystals of Ti-bearing iron oxides, quartz, and carbon-rich particles. Sylvite is also observed in the form of small (~2 micrometer) crystals and filling fractures, suggesting evaporitic conditions. Polarized light observations indicate that Ti-iron oxides correspond to titano-hematite, probably with a detrital origin. Oil immersion objective microscopy observation of carbon-rich particles classifies them as fossil organic matter particles, with grain size between 60 to 300 micrometers. The association of hematite, quartz grains and organic matter particles deposited onto dissolution surfaces confirm a detrital origin, presumably during flooding periods. Although magnetite was not observed under SEM and optical microscope, it carries the natural remanent magnetization, suggesting that hematite deposited by flood events has no or few implications in the quality of the paleomagnetic directions.

This project is funded by Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), and PTDC/CTA-GEO/0125/2021, and is part of the Ph.D. of Rafael Dinis (FCT-10216.2022.BD).

How to cite: Dinis, R., Font, E., P. S. Reboleira, A. S., Ribeiro, J., Gomes, E., and Vilhena, L.: Mineralogical and magnetic evidence of flooding events recorded in a stalagmite from the Moinhos Velhos-Contenda Cave, Portugal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13770, https://doi.org/10.5194/egusphere-egu25-13770, 2025.

Nihewan Basin is one of a series of well-developed East Asian Cenozoic basins in Hebei Province, North China, which are rich sources of mammalian faunas and Paleolithic sites. During the past decades, detailed magnetostratigraphic dating was conducted on the Nihewan Formation and associated mammalian faunas and Paleolithic sites, and the results have contributed significantly to our understanding of the chronostratigraphy of the Nihewan Basin. However, the information about the local regional environments in the Nihewan Basin is limited. In this study, 456 oriented samples were collected from the fluvio-lacustrine sequences of Xiashagou section (thickness 260 m) for detailed rock magnetic and magnetic fabric studies. We try to rebuild the environmental evolution process of Xiashagou area and then discuss the evolution of the paleolake, and provide some new instructions for the environmental changes in Nihewan Basin. We selected 12 typical samples to measure hysteresis loops，isothermal remanence magnetization acquisition and its back-field demagnetization characteristics. The results show that the magnetic minerals in the fluvio-lacustrine sequences are mainly Pseudo-Single Domain (PSD) magnetite particles and a small amount of hematite. The results of magnetic fabric are typical for a primary sedimentary magnetic fabric, which show that the original sedimentary fabric has been preserved in the Xiashagou deposits.

The magnetic foliation (F) of sediments was found to be larger than the magnetic lineation (L).  F and anisotropy degree (Pj) and the flow velocity function (Fs) in the magnetic fabric parameters are more obviously sensitive to environmental changes. There is no long-term stable flow direction in Xiashagou area. According to magnetostratigraphic age framework of fluvio-lacustrine sequences in the Xiashagou section and the top age of fluviol-acustrine sediments in the Haojiatai section, the age of the magnetic fabric parameters and magnetic susceptibility change curves in the Xiashagou section is from 2.7 Ma to 0.3 Ma. The analysis of the lithology and the periodic changes of the parameters of the Xiashagou section showed that the environment of the lake has undergone several significant changes during the period of 2.7～0.3 Ma，which occurred at 2.4 Ma，1.9 Ma，1.3 Ma and 0.9 Ma. So the environmental evolutions of the Nihewan paleolake are divided into five stages.

How to cite: Liu, P., Li, J., and Gao, X.: Charcteristics analysis of magnetic fabric in Xiashagou section and the environmental changes of the Nihewan Lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16484, https://doi.org/10.5194/egusphere-egu25-16484, 2025.

We investigated the rock magnetic and geochemical properties of a collection of pumice samples gathered from the shores of Japan and France. These pumices exhibit a vitreous matrix with a foam-like texture, resulting in low density that allows them to float and drift far from their point of origin to distant coastlines.

A range of analytical techniques was employed, including major and trace element geochemical analyses, SEM and FEG-SEM imaging, EDS-X analyses, and rock magnetic experiments such as thermomagnetic analyses, hysteresis loops, coercivity measurements, and FORC diagrams. The collected pumices display contrasting geochemical signatures and magnetic properties.

The origin of the Japanese pumices was unambiguously traced to the 2021 Fukutoku-Okanoba (FOB) eruption. In contrast, the origin of the pumices found along the French coastline remained uncertain prior to this study. Their geochemical and magnetic properties place most of them slightly outside the range of natural volcanic pumices. We therefore favor an anthropogenic origin.

The concentrations of elements such as arsenic, mercury, and nickel were analyzed to assess potential biohazard risks associated with these pumices. While some metal levels, such as barium and nickel, were found to exceed European hazardous limits, they remain at trace levels. To further explore possible sources, we used oceanic current modeling, which helped us narrow down likely points of origin for these anthropogenic pumices. This finding raises questions about the drift of floating materials across oceans and their impact on coastal environments.

How to cite: Carlut, J., Isambert, A., Garcia da Fonseca, G., Carvallo, C., Fluteau, F., Besson, P., and Libier, Y.: The Journey of Pumice: Rock Magnetic and Geochemical Insights from Coastal Stranding Samples, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17203, https://doi.org/10.5194/egusphere-egu25-17203, 2025.

The Quantum Diamond Microscope holds the potential to revolutionize our field of research. It enables measurements on micrometer scale, going beyond the measurements on bulk rocks that we as a field of research have been using so far. An inherent limitation of QDM observations, however, is that it measures magnetic flux in one direction, usually perpendicular to the surface of a sample. A QDM image is therefore a set of one-dimensional measurements, characterizing the magnetic flux in a plane very close to a polished surface of a sample. Following the potential theory of Kellogg, this geometry precludes making reliable three-dimensional interpretations of these magnetic measurements unless additional information is added.

The required additional constraints can be in the form of imposed boundary conditions, or additional data. If the magnetic sources are assumed to be well separated and of dipolar nature, it is possible to determine the magnetic moment and location of the magnetic sources. This works well in samples with a very low concentration of very small magnetic particles that behave single-domain-like, such as speleothems. In the vast majority of geological materials, however, the sources are not sufficiently well isolated, and complex magnetic anomalies as measured from especially the larger particles are expressions of multidomain states in the grains. Such samples require additional data to reliably determine the magnetic moments of the magnetic grains in them.

Micromagnetic Tomography combines QDM data with information on the location of the magnetic sources in the sample material that is obtained by NanoCT scans. NanoCT measurements can identify iron-oxide bearing grains by their attenuation contrast that is much higher than the other minerals present in geological materials. Currently it is possible to routinely acquire NanoCT scans with a resolution down to 350 nm, enabling the identification of potentially magnetic grains well into the range of vortex domain states.

In this contribution we will present the potential and pitfalls of the interpretation of QDM data, the current state-of-the-art of Micromagnetic Tomography, and their practical applications for paleomagnetic studies on various types of geological samples.

How to cite: de Groot, L., Out, F., de Boer, R., Kosters, M., Bian, G., Cortés-Ortuño, D., and Fabian, K.: The Potential of the Quantum Diamond Microscope and Micromagnetic Tomography for Paleomagnetic Measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17536, https://doi.org/10.5194/egusphere-egu25-17536, 2025.

Paleomagnetic signals from bulk rock samples are often affected by the magnetic properties of individual minerals and the limitations of laboratory methods. Focusing on understanding single magnetic grains enhances the reliability of these signals and refines their interpretation. Advances in micromagnetometry have significantly improved magnetic field imaging capabilities, enabling detailed analyses at the grain level. In this study, quantum scanning microscopy (QDM) and magnetic force microscopy (MFM) were employed to measure magnetic stray fields and domain states of a ~4.5 µm³ large single magnetite grain. Micromagnetic simulations using MERRILL (Conbhuí et al. 2018) were conducted to investigate the grain’s magnetic configurations under varying external fields. The aim was to understand the grain's magnetic behavior in response to these fields and to establish correlations between experimental observations and simulation results.

Four hundred simulations revealed that the magnetite grain, due to its size, symmetry and crystallographic orientation, developed multi-vortex structures with magnetization concentrated near its boundaries. The vortex cores exhibited intricate configurations and were not aligned with specific crystallographic axes. Mean magnetization varied by approximately 38% after exposing to the external field ranged from 100 to 150 mT. The average dipole moment orientations shifted by up to 40° across this field range. After exposure to an external field of 700 mT, the dipole moment orientations became highly stable.

Surface scans showed the evolution of magnetic domains under different external field strengths, particularly at scan heights below 400 nm. At 300 nm, the stray field intensity reached 5 mT, with Bz extremes localized at the grain corners. At scan heights exceeding 500 nm, the stray field patterns transitioned into dipole configurations, obscuring domain-level details. Despite variations in domain structures, dipoles exhibited consistent shapes at higher scan heights. These findings highlight the magnetite grain's response to external fields, with simulations providing valuable insights into its magnetic domain state developments. Systematic analyses with experiements and simulations will enable the differentiation of magnetically stable and unstable grains based on their shape, size, and composition, improving the assessment of magnetic grains as reliable paleomagnetic recorders.

Reference: Ó Conbhuí et al. (2018). Geochemistry, Geophysics, Geosystems, 19, 1080–1106.

How to cite: Bian, G., Williams, W., de Boer, R., Fabian, K., and de Groot, L.: Magnetic Behavior of Single Magnetite Grains: Insights from Micromagnetics and Micromagnetometry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17992, https://doi.org/10.5194/egusphere-egu25-17992, 2025.

Under certain conditions, buried rocks rich in organic matter can undergo spontaneous combustion if their temperature is raised to a certain ignition threshold and oxygen is supplied. Although spontaneous combustion is not very common, it has been described by several authors (Alastuey et al., 1993; Svensen et al., 2003; Abad et al., 2019). In the geological record, these phenomena can be observed due to the pyrometamorphic processes they generate, characterised by very high temperature and low pressure. When the altered rocks are clays, the result are natural clinkers. In this work we carry out a palaeomagnetic and rock magnetism study of these very rare materials. Specifically, we study stratiform bodies of baked clays by spontaneous combustion from 1) the Lower Cretaceous Escucha Formation near Utrillas (Iberian Ranges) and 2) lake sediments from the upper Miocene Molinicos Basin (Betic Cordillera).

Rock magnetism analysis indicates that natural baked clays are characterised by the presence of a very rare mineral phase of high coercivity, low unlocking temperature and thermal stability so-called HCSLT. This phase has only been described in controlled laboratory conditions (Petersen et al., 1987) and in some well-heated archaeological materials (McIntosh 2007). Recently, it has been shown that HCSLT is carried by ε-Fe2O3, a rare metastable polymorph of Fe2O3 with ferrimagnetic behaviour at room temperature (López-Sánchez et al., 2019; Dejoie et al., 2014). In the samples analysed, this phase coexists with magnetite, hematite or maghemite. The palaeomagnetic study indicates that the NRM is carried by the HCSLT phase with the same palaeomagnetic direction as the other high-temperature magnetic phases. The analysis of the directions of the characteristic component provides information about the timing of the spontaneous combustion that generated the carrier minerals and their magnetization.

References:

Abad, I., Sánchez-Gómez, M., Reolid, M., Sánchez-Vizcaíno, V.L. (2019). Minerals, 2019, 9(12), 748

Alastuey, A., Bastida, J., Fernández-Turiel, J.L., Querol, X., Signes, M. (1993). Cuadernos de Geología Ibérica, 17, 171–184.

Dejoie, C., P. Sciau, W. Li, L. Noé, A. Mehta, K. Chen, H. Luo, M. Kunz, N. Tamura, and Z. Liu (2014).  Sci. Rep., 4, 4941

López-Sánchez, J., McIntosh, G., Osete, M.L., del Campo, A., Villalaín, J.J., Pérez, L., Kovacheva, M., Rodríguez de la Fuente, O. (2017). Geochemistry, Geophysics, Geosystems, 18 (7), pp. 2646-2656.

McIntosh, G., M. Kovacheva, G. Catanzariti, M. L. Osete, and L. Casas (2007). Geophys. Res. Lett., 34, L21302.

Petersen, N., N. Schembera, E. Schmidbauer, and H. Vali (1987). Phys. Chem. Miner., 14, 118–121.

Svensen, H.; Dysthe, D.G.; Bandlien, E.H.; Sacko, S.; Coulibaly, H.; Planke, S. (2003). Geology, 31, 581–584.Díaz García, F. (1993). Revista de la Sociedad Geológica de España 6, 105-114.

How to cite: Villalaín, J. J., Casas-Sainz, A. M., Sánchez-Gómez, M., Calvín, P., Yenes, L., Marcén, M., and Pérez-Valera, L. A.: Paleomagnetic and rock magnetic study of baked clays by spontaneous combustion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18109, https://doi.org/10.5194/egusphere-egu25-18109, 2025.

Speleothems can provide high-resolution records to reconstruct the ancient Earth's magnetic field. However, little is known about the influence of speleothem morphologies on the natural remanent magnetisation record. A previous study by Ponte et al. (2017) showed that the magnetic inclination recorded in stalagmites decreases according to the slope of the calcite laminae. Magnetic inclination is 5º lower at the bottom of the stalagmite than at the top. The authors suggest that magnetic particles are re-orientated due to particle rolling during the deposition onto the flank of the stalagmite, resulting in magnetic inclination shallowing. In this scenario, magnetic inclinations are expected to be deeper on the other flank of the stalagmite. Still only half of the stalagmite was available for the study of Ponte et al. (2017). Here, we present new data on a cone-shaped stalagmite from Central Portugal, labelled LM1. We use alternating field demagnetisation, anisotropy of magnetic susceptibility (AMS), anisotropy of anhysteretic remanent magnetisation (AARM), and X-ray microtomography to investigate the orientation of the calcite and magnetic fabrics along the flanks of three detrital-rich calcite layers and their relationship with paleomagnetic directions. We show that magnetic inclination varies up to more than 10° depending on the slope of the calcite laminae. In contrast, magnetic declination is almost constant, corroborating previous results by Ponte et al. (2017). Orientation of the k1 of the calcite fabric determined by AMS shows a striking correlation with the k1 of the magnetic fabric obtained by AARM, suggesting that the orientation of the magnetic particles is mainly controlled by the growth direction of the calcite crystals, which is perpendicular to the surface of the stalagmite. However, magnetic inclinations are not symmetrical between both flanks, suggesting that the particle rolling hypothesis is invalid in this case. In addition, the fact that the maximum variations of the remanent magnetic inclination do not exceed 10º indicates that not all the magnetic carriers are reoriented according to the calcite fabric and that the mechanisms responsible for the acquisition of the detrital remanent magnetisation are more complex than previously thought.     

Acknowledgments: PTDC/CTA-GEO/0125/2021 Foundation of Sciences and Technology (Portugal) and BU037P23 Junta de Castilla y León (Spain). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101005611 for Transnational Access conducted at DMEX-UPPA-FRANCE.

How to cite: Sánchez-Moreno, E. M., Font, E., Calvín, P., Faucher, S., Sénéchal, P., and Dimuccio, L. A.: New insights into the origin of magnetic inclination shallowing in stalagmites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18301, https://doi.org/10.5194/egusphere-egu25-18301, 2025.

Magnetic hysteresis measurements are widely used in Earth and planetary sciences with the aim of identifying geologically meaningful magnetic recorders, and to study variations in present and past environments. The interpretation of hysteresis data in terms of domain state and paleomagnetic stability are major motivations behind undertaking these measurements, but are fraught with challenges and ambiguities. We have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room-temperature magnetite as a function of particle size (45–195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant); our models span uniformly magnetized single domain (SD) to non-uniformly magnetized single vortex (SV) states. Within our models the reduced magnetization associated with SV particles marks a clear boundary between SD (≥0.5) and SV (<0.5) magnetite. We further identify particle sizes and shapes with unexpectedly low coercivity and coercivity of remanence. These low coercivity regions correspond to magnetite particles that typically have multiple possible magnetic domain state configurations, which have been previously linked to a zone of unstable magnetic recorders. Of all the hysteresis parameters investigated, transient hysteresis is most sensitive to particles that exhibit such domain state multiplicity. When experimental transient hysteresis is compared to paleointensity behavior, we show that increasing transience corresponds to more curved Arai plots and less accurate paleointensity results. We therefore strongly suggest that transient behavior should be more routinely measured during rock magnetic investigations.

How to cite: Paterson, G., Moreno, R., Muxworthy, A., Nagy, L., Williams, W., and Tauxe, L.: Magnetic Hysteresis Properties of Magnetite: Trends With Particle Size and Shape, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18553, https://doi.org/10.5194/egusphere-egu25-18553, 2025.

Understanding the nanoscale composition and exsolution behaviour of iron oxides is crucial for interpreting paleomagnetic signals and the thermochemical history of volcanic rocks. This study employs Atom Probe Tomography (APT) and Transmission Electron Microscopy (TEM) to investigate the nanoscale features of exsolved iron oxides within a volcanic basalt sample.

We investigate an intergrowth of ilmenite, titanohematite, and rutile, using 3D chemical mapping to precisely determine exsolution boundaries and quantify compositional transitions between the minerals with atomic-scale precision. TEM analyses complement these findings, offering structural and morphological context to the chemical variations. Preliminary results reveal distinct exsolution zones characterized by well-defined compositional gradients and interfacial features. These findings offer novel perspectives on the nanoscale architecture of exsolved iron oxides, providing a foundation for more accurate interpretations of paleomagnetic data.

While this study currently focuses on ilmenite-titanohematite-rutile systems, ongoing research will incorporate data from a magnetite-ilmenite assemblage, expanding our understanding of the broader mineralogical and magnetic structure of the sample. This research will be particularly valuable for researchers who may not be extensively familiar with the capabilities of APT in resolving nanoscale compositions and mineral phase relationships within geological samples.

How to cite: Gergov, H., Muxworthy, A., J. Harrison, R., and Williams, W.: Compositional insights into exsolved mineral phases: Atom Probe Tomography at the exsolution boundary., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19138, https://doi.org/10.5194/egusphere-egu25-19138, 2025.

The behaviour of the geomagnetic field through time provides insight into the formation and evolution of Earth’s interior. However, for certain geological periods the Earth’s magnetic field behaviour is poorly understood. For instance, the Devonian period remains enigmatic as palaeomagnetic records of this time are ambiguous. Devonian bulk rock samples often yield scattered magnetic directions, even when ideal magnetic carriers are present. This may be explained by partial remagnetisation or by complex, non-dipolar magnetic field behaviour.

We conducted a palaeomagnetic study on Middle Devonian pillow basalts from the Rhenish Massif, Germany and encountered inconclusive bulk magnetic behaviour. Directions obtained through alternating field (AF) demagnetisation are scattered and do not cluster around a common mean. While some of these results can be attributed to partial overprints, not all findings can be explained with this mechanism. To investigate this further, we analysed the individual magnetic grain behaviour in the samples using Micromagnetic Tomography (de Groot et al., 2018; 2021).

With MMT, we measured the natural remanent magnetisation (NRM) of the samples, and we conducted an AF demagnetisation sequence. With this, we studied the individual grains in the samples across five demagnetisation states. This approach aimed to identify the magnetically stable grains in the samples that are capable of preserving interpretable geomagnetic signals.

Our findings may improve the understanding of Middle Devonian geomagnetic field behaviour and enable the use of previously uninterpretable samples in reconstructing long-term geomagnetic field behaviour.

How to cite: de Boer, R. and de Groot, L.: Deciphering Middle Devonian geomagnetic field behaviour through analysis of individual remanence carriers., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19482, https://doi.org/10.5194/egusphere-egu25-19482, 2025.

Magnetic particles trapped into speleothems usually originate from the soils capping the cave and are transported into the cave by dripwaters. However, authigenic magnetic particles may also precipitate under conditions likely to prevail during speleothem growth. Here we investigate the magnetic mineralogy of a stalagmite from the Cerâmica Cave, Central Portugal, characterized by brown to red calcite laminations. We also analyzed the host carbonate, the cave sediments, and the soils capping the cave. We measured concentration- and grain size-dependent magnetic proxies, including natural remanent magnetization, anhysteretic remanent magnetization, isothermal remanent magnetization, mass-specific magnetic susceptibility, FORC, and hysteresis curves.  Results show that magnetic and hematite are the main magnetic carriers in all samples. A gradual enrichment of hematite relative to magnetite is observed following the transportation path from the soils to the cave sediments up to the stalagmite. The higher contribution of hematite relative to magnetite in the speleothem may reflect the precipitation of authentic hematite during speleothem growth or the selective transport of finer particles from the soil to the cave. 

This project is funded by Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025, UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020), and PTDC/CTA-GEO/0125/2021, and is part of the Ph.D. of Ana Raquel Bras (2024.03482.BD).

How to cite: Brás, A. R., Font, E., Feinberg, J., Dinis, R., Reboleira, A. S., and Adatte, T.: Origin of hematite in a stalagmite from the Cerâmica Cave, Central Portugal, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20296, https://doi.org/10.5194/egusphere-egu25-20296, 2025.

Reconstructing the North Atlantic Deep Water (NADW) formation and strength over time is fundamental to understanding North Atlantic and global ocean circulation and climate evolution. A multi-proxy approach on sedimentary core records can provide the temporal resolution needed to investigate NADW history for the last 12 Ma (from Upper Miocene to Pleistocene).

Here, we focus on the Björn Drift, located in the eastern flank of the Reykjanes Ridge, where the accumulation rate and provenance of sediment in the Iceland-Scotland Overflow Water (ISOW) path are sensitive to variations in the strength of NADW production as well as sediment production processes. IODP expeditions 384, 395C, and 395 drilled site U1554 (holes A-H) on the Björn Drift (60°7.5'N, 26°42.1'W, 1870 mbsl). A preliminary biostratigraphic and magnetostratigraphic age model defines the age of the basement-sediment interface at approx. 12 Ma and a maximum ≥10 cm/kyr accumulation rate. Preliminary rock magnetic analyses on selected discrete samples consist of bulk magnetic susceptibility, Anysteretic remanent Magnetization (ARM), and Isothermal Remanent Magnetization (IRM). These are compared with Nd-Sr isotopes (measured on the same samples) and used as proxies to examine sediment provenance in the Björn Drift. The aim is to determine changes to the endmember components before and after drift development. Correlations of these components with previous studies targeting IODP and ODP cores from the North Atlantic suggest that terrigenous sediment has a dominance of Icelandic source contribution in interglacial intervals and a dominance of European continental source contribution during glacial intervals.

How to cite: Di Chiara, A., Dweyer, D., Friedman, S., Satolli, S., Bonilla-Alba, R., Hemming, S. R., Rasbury, T., Karatsolis, B. T., Sinnesael, M., Parnell-Turner, R., Briais, A., Levay, L., and 395Scientists, E.: Rock magnetic proxies to infer terrigenous provenance variation on Björn Drift IODP Site U1554, preliminary results., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21031, https://doi.org/10.5194/egusphere-egu25-21031, 2025.

Evidence of profound climatic changes and wetter conditions during the late Quaternary are mentioned by several authors for the deserts of central Iran (e.g. Khademi and Mermut, 1999; Jalilian et al., 2022). The region today is strongly influenced by aeolian and desertification processes which are mainly attributed to human activities. To examine the role of chemical weathering (under moist conditions) and long-term dust influx (under dry conditions) on soil genesis, we studied the mineralogical composition of soil materials in a relict paleosol of an arid region of eastern Isfahan, central Iran. A high-resolution sampling strategy (10 cm interval) and qualitative and quantitative X-ray diffraction method were applied. The paleosol is located on an upper terrace with a flat surface having a gravelly structure and neither groundwater influence nor input of materials from adjust landforms. The results showed that quartz, calcite, Na-plagioclase and chlorite are dominant minerals in the clast fraction of the paleosol. The comparison of the mineralogical composition of soil materials and gravels revealed that K-feldspar, gypsum, smectite and palygorskite in the soil matrix were not inherited from the gravels but were provided by dust influx and/or pedogenesis processes. K-feldspar was absent in the gravels and was added by dust influx as its neoformation in the soil environment is unlikely. This hypothesis is supported by the exponential increase of its amount towards the soil surface and the maximum accumulation of the mineral in the surface dust-derived (vesicular) horizon. Smectite is also absent in both the clast fraction and the vesicular horizon and showed a maximum abundance in the middle and lower parts of the pedon where pedogenic calcite deposition occurred ~29 ka, suggesting a pedogenic origin of the mineral under the semiarid and seasonal climate. Palygorskite is absent in gravels but occur in the surface vesicular horizon and was relatively uniformly distributed throughout the pedon. It seems that palygorskite has both exogenic (from dust) and endogenic (by pedogenic processes) sources in the paleosol. Scanning electron microscopy (SEM) images support this postulation. SEM images exhibited dense fibers of palygorskite in the soil matrix and broken and small pieces of palygorskite in the dust-derived horizon. The investigated paleosol provided evidence of environmental changes from a semi-arid and seasonal climate during the time of smectite pedogenesis to an arid and dust deposition environment. Consequently, the palaeosol exhibited a mostly natural trend of aridification and desertification in this region during the late Quaternary.

Jalilian, T., Lak, R., Taghian A. and J. Darvishi Khatooni, 2022, Evolution of sedimentary environments and geography of the Gavkhouni Playa during the Late Quaternary, International Journal of Environmental Science and Technology, 19, 1555–1572.

Khademi, H. and A. R. Mermut, 1999, Submicroscopy and stable isotope geochemistry of carbonates and associated palygorskite in Iranian Aridisols, European Journal of Soil Science, 50 (2), 207-216.

How to cite: Bayat, O., Plötze, M., Karimi, A., and Egli, M.: High-resolution mineralogical record of soil genesis and dust influx in a relict palaeosol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-229, https://doi.org/10.5194/egusphere-egu25-229, 2025.

Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin, northwest China, with high spatiotemporal resolution. This paper presents comprehensive radiocarbon and tree-ring data sets of subfossilized medieval forest in the Tarim Basin compiled from geomorphological investigations of the palaeochannels of the Tarim River, the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. This study describes the centennial-scale dynamics in the Tarim River flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior. Subsequently, we consider the role of the river-based hydrological fluctuations in connectivity of the ancient continental Silk Road networks.

How to cite: Li, K., Qin, X., Plunkett, G., and Brown, D.: Hydrological fluctuations in the Tarim Basin, northwest China, over the past millennium, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-506, https://doi.org/10.5194/egusphere-egu25-506, 2025.

Australia's drylands, covering nearly 70% of the continent exhibit the most variable precipitation and streamflow regimes globally. The endorheic Lake Eyre Basin (LEB) terminates at Kati Thanda-Lake Eyre (KT–LE), Australia’s largest lake and drains 1.14 M km². This basin experiences remarkable ecological fluctuations with spectacular boom and bust cycles during extreme flooding events. This vast unregulated river basin, despite its ecological significance, has limited stream gauges and no lake monitoring, making the lake's water balance a real challenge due to its vast size, remote location and complex lake geometry. Recent observations reveal significant water loss in endorheic basins worldwide, emphasizing the urgency for improved freshwater monitoring solutions for KT – LE and its basin. Therefore, in this study, we present a space-based monitoring solution to estimate the storage volume of the KT–LE as an alternative to in situ measurements.  To do so, we utilized the data from the Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022, to monitor the 2024 KT-LE filling event. The duration of this event was between March and October 2024. The predicted maximum lake storage volume (recorded on 1^st May) reached 0.82 Km³ with a predicted average depth of -14.2 metres AHD (Australian Height Datum). We cross-compared the volume estimates from three bathymetry digital elevation models to evaluate the derived estimates in the absence of in situ data. We achieved the accuracy of the derived water surface elevation estimates with a root mean square error (RMSE) of <0.6 meters. This research highlights the potential of SWOT data for addressing critical data gaps in hydrological monitoring and advancing water balance assessments in arid and semi-arid regions and in large wide and shallow playa lakes.

How to cite: Rai, A. K., Cohen, T. J., Armon, M., and Marx, S. K.: Quantifying input volumes in Australia’s largest playa lake using SWOT data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-754, https://doi.org/10.5194/egusphere-egu25-754, 2025.

Effective water resource management in arid and data-scarce regions necessitates innovative approaches that incorporate advanced hydrological modeling and remote sensing technologies. This study focuses on developing nature-based solutions for groundwater recharge, specifically identifying aquifer recharge zones to combat water scarcity in areas characterized by low precipitation and limited streamflow data.

Utilizing the Soil and Water Assessment Tool Plus (SWAT+), this research integrates remote sensing datasets with observed hydrological data for model calibration, aiming to estimate water availability and optimize storage potential. A comprehensive water balance approach is employed to evaluate precipitation, evapotranspiration, runoff, and infiltration dynamics, which enables precise estimation of water availability for recharge efforts.

By coupling SWAT+ with a groundwater module, the study analyzes infiltration capacity at a grid scale, facilitating the identification of high-potential groundwater recharge zones. The integration of remote sensing-derived parameters, including land use, soil type, and topography, enhances the model's ability to simulate water flow dynamics across watersheds.

This methodology is applied to Balochistan, Pakistan’s most vulnerable province to floods and droughts, where groundwater overexploitation and insufficient infrastructure exacerbate water challenges. The study’s findings provide insights into sustainable aquifer recharge strategies, supported by spatial analyses and thematic maps. These results inform the development of targeted interventions for water conservation, flood mitigation, and drought resilience in one of the world’s most water-stressed regions. This approach highlights the transformative potential of combining nature-based solutions with advanced hydrological modeling to secure water resources in arid regions.

How to cite: Naseer, A., Hafeez, M., Arshad, M., and Faizi, F.: Developing Nature-Based Solutions for Sustainable Groundwater Recharge through Advanced Hydrological Modelling and Water Availability Assessment in Arid Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1434, https://doi.org/10.5194/egusphere-egu25-1434, 2025.

Several studies demonstrated that >~100 absolute ages of sand at certain spatial/vertical resolutions are required for constructing a reliable chronological framework for palaeoenvironmental and palaeoclimatic interpretations of dunefield construction (Telfer and Hesse, 2013). As acquiring abundant absolute ages demands significant field and lab resources, several methodological approaches, such as port-OSL-OSL age estimates, have attempted to partly overcome this necessity (Stone et al., 2019).

Arid-zone encroaching dunes in the past and present, often dam drainage systems and generate proximal upstream, dune-dammed waterbodies that when dry, form playas. These waterbodies that are often seasonal, deposit distinct, low-energy, fluvial, fine-grained sediments (LFFDs), often as couplets. This recurring aeolian-dominated aeolian-fluvial (AF) process gradually leads to amplified LFFD accumulation, and partly configures dunefield, and particularly dunefield margin landscape evolution.

The INQUA DuneAtlas of global dunefield chronological data includes some dated samples that are non-dune sediments such as interdune and LFFD samples. However, the complementary contribution of such sediments to interpreting dunefield chronologies has not been fully assessed (Lancaster et al., 2016). Furthermore, and surprisingly, DuneAtlas dune sand samples that date to the LGM are sparse. We demonstrate that OSL ages, partly supported by port-OSL profiling, mainly of sandy units within LFFDs, improves the resolution and reliability of dating dunefield construction events and morphological maintenance of existing dunes, and in some cases even reveals periods of dune mobilization that are absent in dated dune cores.

Spatially dense, OSL-dated dune cores and sections of the ~10³ km² sized northwestern Negev dunefield (Israel) study area, revealed that the dunefield was constructed in two main sand incursion and vegetated linear dune (VLD) buildup/extension periods during the Heinrich 1 (H1) and Younger Dryas (YD) (Roskin et al., 2011; Thomas and Bailey, 2019). In this study, exposed, OSL-dated LFFD sections along the dunefield margins revealed that dune-dammed waterbodies destroyed earlier dunefield-margin dunes, partly erode others, but also preserve remains of eroded dunes between LFFD units. The LFFD sections revealed for the 1^st time, significant and initial dune incursion and damming during the LGM, and also LFFD deposition thru the early Holocene (Robins et. al., 2022, 2023). The extent and relative thickness of H1-dated LFFDs suggest that dune encroachment then was greater than during the YD of the climate may have been slightly wetter. Early Holocene sediments may imply partial dune buildup or equilibrium-like dune maintenance in the early Holocene and, or also, a lag between YD dune-damming and later fluvial dune-breaching - when LFFD stratigraphic buildup gradually neared dune crest elevation leading to an outburst flood.

Altogether, studying and dating dune-dammed LFFDs are proposed to not only be a complementary, but rather a primary approach to date dunefield evolution and interpret past forcing drivers of sand mobilization and stabilization, and palaeohydrology.

References

Lancaster, N., et al., 2016. QI 

Robins, L., et al., 2022. QSR 

Robins, L., et al., 2023. QSR

Roskin, J., et al., 2011. QSR 

Stone, A. et al. 2019. QG 

Telfer, M.W. and Hesse, P.P., 2013. QSR 

Thomas, D.S. and Bailey, R.M., 2019. AR 

How to cite: Roskin, J., Robins, L., and Greenbaum, N.: OSL-dated, dune-dammed waterbody sediments along dunefield fringes improves resolution and reliability of dunefield evolution chronologies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2344, https://doi.org/10.5194/egusphere-egu25-2344, 2025.

Neogene tectonics, geomorphological processes, and Quaternary climate change control landscape evolution in the internally drained basins of the Basin of Great Lakes (BGL), western Mongolia. The interplay of aeolian, fluvial, and lacustrine processes has resulted in a variety of landforms, such as large dune fields, beach bars, and alluvial fans. Their associated sedimentary archives and sediment transport pathways reflect mid-to-late Quaternary landscape evolution. The ongoing project analyzes geomorphological processes and sedimentary records. Different dating methods constrain the timing of landforms and deposits.

(1) Aeolian and fluvial dynamics: Mongolia's three largest dune fields, resulting from a long-term Quaternary sediment cycle, are located in the BGL. Rivers transport sediment into endorheic lakes. During lake-level low stands, winds transport the sand eastwards along the dune fields. The lakes exhibit different paleolake levels, and sandy plains with mobilized sand at their eastern ends exist. Three climatic and paleoclimatic implications are derived from a mapping approach¹. (i) The fundamental west-east orientation of the dune fields is a result of the westerly winds that prevailed during the arid periods of the Quaternary. (ii) The highest lake levels occurred during pluvial phases caused by increased moisture supply. (iii) In the modern semi-arid climate, wind systems from north to northwest predominate, while in the southernmost dune field, minor winds from the southeast occur. Preliminary dating results give mid-Pleistocene dates for the core of the dune fields and Holocene dates for the youngest and smaller dunes.

(2) Lake level fluctuations: The first comprehensive late Quaternary chronology of lake level variations for the Khyargas Lake in the BGL is presented. The data is based on a geomorphological approach supported by luminescence dating. The lake is the ultimate sink of a sequential water and sediment cascade from the adjacent Mongolian Altai and Khangai Mountains. Several intercalated lakes repeatedly merged to form a large paleolake, as evidenced by various shoreline features. Twelve paleolake levels between +7m and +188m above the modern lake level (a.m.l.) are identified from well-preserved paleoshoreline sequences. Calculations of paleolake extent and water volumes emphasize times of enhanced inflow and gradual capture and subsequent reduced inflow and abandonment of upstream-located lakes. Three distinct phases of lake level dynamics can be differentiated: (i) A transgression to a maximum level of +129m (a.m.l.) during Marine Isotope Stage 5c primarily controlled by enhanced atmospheric moisture supply. (ii) A post-Last Glacial Maximum lake expansion to a level of +118m (a.m.l.) around 14 ka, ultimately controlled by glacial meltwater pulses. This period was followed by a rapid lake level drop during the Late Glacial–Holocene transition in response to decreasing meltwater supply and a drier climate. (iii) Small-scale lake level fluctuations throughout the Late Holocene reflect a hydro-climatically controlled equilibrium between ~ 2.6 and 0.7 ka.

The final project phase will obtain TCN dating of paleoshorelines and alluvial fan activity.

¹ Lehmkuhl, F. et al. Aeolian sediments in western Mongolia: Distribution and (paleo)climatic implications. Geomorphology 465, 109407 (2024).

How to cite: Lehmkuhl, F., Wolf, D., Frechen, M., Rahimzadeh, N., Tskamato, S., Batkhishig, O., Owen, L. A., and Wegmann, K.: Paleoclimate and landscape evolution in an extreme continental interior – Interplay between aeolian, fluvial, and lacustrine systems in the Basin of the Great Lakes, Western Mongolia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3123, https://doi.org/10.5194/egusphere-egu25-3123, 2025.

The hyperarid conditions of the central Atacama, characterized by extremely low precipitation and high evaporation rates, create a unique environment where soil stability is generally thought to be exceptionally high due to the widespread gypsum and salt enrichment. Terrestrial cosmogenic nuclide-based surface exposure ages suggest that many surfaces underwent limited to no changes since the Neogene or early Pleistocene. However, a number of recent studies also underline the younger landscape-scale geomorphodynamic activity, as evidenced by e.g., the incision of the Rio Loa canyon during the late Pleistocene, or by growth of calcium-sulphate wedges and associated patterned grounds in the Central Depression at the onset of the Holocene. Despite this discrepancy, there is a limited understanding of past and present soil dynamics under this extreme hyperaridity, including subsurface turbation processes driven by both biological and salt dynamics (bioturbation, haloturbation). So far, no geochronological framework exists for these important subsurface soil processes, and the factors controlling these processes are still unknown.

Our study aims at providing new insights into the dynamics of subsurface soil processes in the hyperarid Atacama Desert. We use feldspar single grain luminescence dating techniques combined with sedimentological and geochemical analyses to decipher the activity or inactivity of soil material conveyance processes. We present results from investigations of four soil profiles. All profiles are situated in alluvial (fan) deposits along a west-to-east climatic transect stretching from the fog-affected western slopes of the Coastal Cordillera near sea level to the hyperarid core of the Atacama Desert at approximately 2000 m above sea level. Even though all studied profiles are situated in alluvial (fan) deposits, the geomorphic setting and thus the (sub)recent sedimentation dynamics differed considerably between the profiles. Soil dynamics in the form of vertical grain transport as well as material exchange and mixing were only detected in the coastal profiles where sufficient moisture supply supports the presence of vegetation and associated soil fauna. In these lower elevations, alluvial (fan) surfaces appear geomorphologically stable since their deposition, but our profiles exhibit evidence of significant post-depositional soil material reworking. In the hyperarid region above fog occurrence, that is only affected by rare episodic rain, post-depositional turbation processes seem to be absent or restricted to the surface layer. However, in these hyperarid regions, sediment (re)deposition seems to have taken place on relatively recent time scales, thereby adding more data on late Pleistocene to Holocene surface activity in the driest non-polar desert on Earth, that are likely driven by aeolian dust and/or episodic alluvial processes.

How to cite: Maßon, L., May, S. M., Riedesel, S., van der Meij, M., Steiner, J., Opitz, S., and Reimann, T.: Activity and stability of surfaces and soils in the Atacama Desert, Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4036, https://doi.org/10.5194/egusphere-egu25-4036, 2025.

Last major fluvial modification along the hyperarid coast of the Atacama Desert is relatively young. It has been found that the coastal alluvial fans (CAFs) were formed during the Late Pleistocene and Holocene. No remnants older than the last interglacial period could be constrained as yet. However, robust geochronological frameworks by numerical dating using radiocarbon dating, trapped charge dating techniques, and in situ terrestrial cosmogenic nuclides are restricted to few sites. This is related to both the geomorphic and stratigraphic complexity of the multi-stage CAFs as well as the high costs of those numerical dating methods. Consequently, it has remained unclear so far to what extent fan aggradation and progradation is controlled by large-scale allogenic versus individual autogenic forcing.

As a first study, an application of the cost-effective Schmidt hammer exposure-age dating (SHD) technique was explored for constraining the age of terminal aggradation of the CAF generations along the south-central coast of the Atacama Desert (24°15’S–25°15°S) using an ¹⁰Be exposure-dated telescopic alluvial fan featuring four control surfaces (after Walk et al., 2023) for age calibration. Apart from the calibration site, SHD was applied on, in total, 19 depositional lobes from 11 CAFs featuring at least one phase of progradation following main channel incision. Morphostratigraphies are primarily based on in-field mapping. Rebound (R) values were systematically assessed using an electronic N-type Schmidt hammer for each abandoned fan generation (Q1–Q3) by randomly sampling 50 surface boulders of comparable lithology. For calibration with recent deposits (Q4), multiple impacts were exerted on a careful selection of few boulders. Linear age calibration and error propagation follows the two-point solution by Matthews and Winkler (2022), adapted to a segmented approach for four control surfaces and complemented by Deming regression.

Calibration results in a negative and significant linear relationship between ¹⁰Be exposure ages and R values, presenting a robust regional calibration model for SHD of fan boulders exposed at least since the last interglacial period. SHD of the 19 fan surface generations yield ages of terminal aggradation ranging between the mid MIS 4 (late MIS 3) and early to mid MIS 5. The age range exceeds the usual dating range reported for SHD applied in (sub)humid regions by up to one order of magnitude, which can be explained by the comparatively low weathering rates at the arid-hyperarid transition. The relative age uncertainties amount to 3–20% (10–24%) and allow to deduce a spatial heterogeneity in the Late Quaternary fan morphodynamics. While the CAFs south of 24°53’S show a systematic response probably related to palaeoclimatic changes of the SE Pacific, those to the north are decoupled – indicating a potential control by individual autogenic forcing.

References
Matthews, J.A., Winkler, S. (2022): Schmidt-hammer exposure-age dating: a review of principles and practice. Earth-Science Reviews 230, 104038. DOI:10.1016/j.earscirev.2022.104038

Walk, J., Schulte, P., Bartz, M., Binnie, A., Kehl, M., Mörchen, R., … Lehmkuhl, F. (2023): Pedogenesis at the coastal arid-hyperarid transition deduced from a Late Quaternary chronosequence at Paposo, Atacama Desert. Catena 228, 107171. DOI: 10.1016/j.catena.2023.107171

How to cite: Walk, J.: Expansion of the Late Quaternary morphochronology of Atacama’s coastal alluvial fans (northern Chile) by Schmidt hammer exposure-age dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4535, https://doi.org/10.5194/egusphere-egu25-4535, 2025.

On dryland hillslopes, vegetation water availability is often subsidized by the redistribution of rainfall runoff from bare soil (sources) to vegetation patches (sinks). In regions where rainfall volumes are too low to support spatially continuous plant growth, such functional connectivity between bare soil and vegetated areas enables the establishment and persistence of dryland ecosystems. Increasing the connectivity within bare soil areas can intensify runoff and increase water losses from hillslopes, disrupting this redistribution and reducing the water available to sustain ecosystem function. Inferring functional connectivity (from bare to vegetated, or within bare areas) from structural landscape features is an attractive approach to enable rapid, scalable characterization of dryland ecosystem function from remote observations. Such inference, however, would rely on metrics of structural connectivity, which describe the contiguity of bare soil areas. Unfortunately, several studies have observed non-stationarity in the relations between functional and structural connectivity metrics as rainfall conditions vary. Consequently, the suitability of using structural connectivity to provide a reliable proxy for functional connectivity remains uncertain.

Here rainfall runoff simulations across a large range of dryland hillslopes, under varying soil and rainfall conditions are used to establish relations between structural and functional connectivity metrics. The results identify that the relations very between two hydrologic limits -- a 'local' limit, in which functional connectivity is related to structural connectivity, and a 'global' limit, in which functional connectivity is most related to the hillslope vegetation fraction, regardless of the structural connectivity of bare soil areas. The transition between these limits within the simulations depends on rainfall intensity and duration, and soil permeability. While the local limit may strengthen positive feedbacks between vegetation and water availability, the implications of these limits for dryland functioning need further exploration, particularly considering the timescale separation between storm runoff production and vegetation growth.

How to cite: Crompton, O., Katul, G., and Thompson, S.: Linking structural and functional connectivity in drylands under varying rainfall and soil conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4557, https://doi.org/10.5194/egusphere-egu25-4557, 2025.

Drylands cover approximately 41% of the global land area and support diverse fluvial systems. Identifying the geomorphic diversity of dryland rivers and their maintenance is essential for sustaining ecosystems in arid and semi-arid regions. Furthermore, amidst climate change and the anticipated expansion of dryland areas, gaining insights into this diversity is crucial for developing adaptive and effective management strategies for dryland rivers.  However, dryland rivers are often generalized, with studies focusing more on their distinct characteristics than the inherent geomorphic diversity that shapes river character and behaviour. A comprehensive understanding of the occurrence, spatial distribution, and major controls on channel morphological diversity of dryland rivers is still lacking. To address this gap, we have examined the geomorphic diversity within and across two semi-arid dryland river basins in western India: the Mahi River Basin (MRB) and the West Banas River Basin (WBRB). We employed River Styles classification for geomorphic characterization, combined with hydrological analysis, total stream power and specific stream power assessment for a more comprehensive evaluation. Hydrological analysis indicates that MRB and WBRB are monsoon-dominated rivers. MRB is a perennial dryland river with high flow permanence downstream, whereas WBRB is intermittent, with discharge decreasing downstream. Geomorphic characterization shows that MRB predominantly exhibits a confined, terrace margin controlled, meandering, gravel bed River Style. Only a small section of the estuarine zone exhibits a partly confined, terrace margin controlled, fine-grained bed River Style. Terraces impose antecedent confinement on the contemporary river processes in the MRB, limiting floodplain development. On the contrary, WBRB predominantly features laterally unconfined, continuous channel, low sinuosity, gravel-to-sand bed River Style with extensive floodplain development. The midstream section shows a partly confined, terrace margin controlled, gravel bed River Style in the pediment zone. Stream power analysis showed high stream power even in the mid-to-downstream pediment zone of both basins, primarily driven by site-specific structural controls influencing current channel processes. Field investigations indicated that erosion processes, notably plucking, predominantly shape the reaches with higher stream power. The maximum specific stream power in the pediment zone is 98 W/m² and 255 W/m² in the WBRB and MRB, respectively. Geomorphic diversity within the basin is primarily shaped by geological control in the rocky uplands, while the pediment and alluvial zones reflect a combination of geological controls and Holocene climatic imprints. Although both basins are in semi-arid regions, the observed geomorphic diversity across the basin is governed by stream power distribution patterns with underlying geological controls and valley evolution at the millennial time scale. Insights from this study can enhance ground-level river management practices by incorporating the diversity of dryland rivers and contributing to the global inventory, thereby enriching our understanding of dryland river systems.

How to cite: Raj, A. and Jain, V.: Geomorphic diversity of dryland rivers and their controls in the semi-arid region, Western India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4741, https://doi.org/10.5194/egusphere-egu25-4741, 2025.

Whether the provenance of eolian deposits on the extensive Chinese Loess Plateau (CLP) is spatiotemporally heterogeneous/homogeneous is highly controversial. Here we present detrital zircon U-Pb ages for the eolian dust from the central-eastern Mu Us desert, its underlying Cretaceous sandstones, and the loess from the northeastern CLP. The comparable detrital zircon U-Pb age signatures between the eolian deposits from eastern Mu Us and Cretaceous sandstones suggests that eolian deposits in the eastern Mu Us are largely the product of weathering and recycling of regional bedrock. Typical loess on the northeastern CLP show relatively consistent zircon age spectra with those from the eastern Mu Us, indicating significant contributions of the western North China Craton (NCC) to the loess on the northeastern CLP. Temporal consistencies of U-Pb age spectra for a 13.6 m-thick eolian sand-loess sequence in the eastern Mu Us desert reveals that there is no apparent provenance shift at least since the last interglacial. Comparison of detrital zircon U-Pb age spectra of Late Pleistocene loess developed on the northeastern, eastern, and west-central CLP demonstrates that the contributions from the western NCC increase significantly for the loess on the eastern-northeastern CLP, while the west-central CLP received more eolian dust from the northeastern Tibetan Plateau (NTP) and the Central Asian Orogenic Belt (CAOB). The contribution of detritus from the NTP decreases, and the contribution from the western NCC outweighs that from the NTP on the eastern-northeastern CLP. Our new detrital zircon data provide robust evidence for the spatial heterogeneity of provenance across the CLP, regardless of the general characteristics of multiple recycling and thorough mixing of Chinese loess.

How to cite: Sheng, M., Wang, X., and Zhang, S.: Spatial variations in the provenance of eolian deposits on the Mu Us desert and the Chinese Loess Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7661, https://doi.org/10.5194/egusphere-egu25-7661, 2025.

The high-accumulation-rate eolian deposits in the eastern Hexi Corridor retain invaluable archives of rapid climatic fluctuations in the transitional zone of the northwestern Chinese Loess Plateau, the Tengger Desert, and the northern foothills of the Qilian Mountains. High-resolution mineral magnetic and bulk grain size analyses for the Shagou loess–paleosol sequences since the last interglacial reveal that loess accumulation in northwestern limit of the East Asian summer monsoon is essentially continuous at multi-centennial scales, and variations in magnetic granulometry of the last glacial loess are predominated by the intensity of the East Asian winter monsoon (EAWM). Based on Greenland Ice Core Chronology, the complete recording of all Dansgaard–Oeschger (D–O) cycles and Heinrich events substantiates a rapid response of the EAWM to the northern high-latitude abrupt climatic changes, regulated by the strength of the Atlantic Meridional Overturning Circulation (AMOC) and Arctic sea-ice extent. A synthesis of various high-resolution paleo-proxy records from the Northern Hemisphere further suggests the generally identical phasing of stadial–interstadial oscillations and tight coupling of the atmosphere-ice-ocean system. We propose that the relatively stronger D–O signals in low-latitude tropical marine sequences compared with middle-latitude land-based paleo-records may be accounted for by northward transport of heat and moisture originated from the warmest tropical oceans during interstadials, and the more significant influence of oceanic processes than that of atmospheric processes in propagating the northern high-latitude climatic signals during stadials. This study highlights the pivotal role of AMOC in modulating millennial-scale regional and global climate.

How to cite: Wang, X., Sheng, M., and Yi, S.: Links of abrupt climate events in the eastern Hexi Corridor to Atlantic meridional overturning circulation changes during the last glacial：magnetoclimatological evidence of the Shagou loess record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7789, https://doi.org/10.5194/egusphere-egu25-7789, 2025.

Identifying reliable indicators of environmental changes is crucial for effective ecosystem management, particularly in drylands which are prone to climate change impacts. Here, we report on how we are integrating time-series remote sensing, advanced data science techniques, and ground-based observations to identify, map, and assess the sensitivity of a diverse suite of wetlands in drylands to environmental perturbations.  We are particularly interested in potential ‘sentinel wetlands’: natural features that are highly sensitive to subtle climatic changes. These wetlands may act as early warning systems, reflecting the cumulative effects of various climate stressors on their hydrodynamic state.

We have developed a method to automatically map different surface waterbodies (including a range of low- and high-altitude wetlands) and characterise their wetness dynamics at pixel-scale using time-series multispectral satellite data. We have applied the method to drylands spanning three different continents (western and northern India, southwest Spain, Argentinian Patagonia) and validated the mapped wetness dynamics of key features such as floodplain and valley-bottom wetlands, interdunal depressions, playas and pans through extensive field visits (~10 000 km of road trip).

From our field visits, we conclude that not all wetlands are good candidates for serving as sentinel wetlands. The best candidates are those wetlands which are devoid of direct human interventions, sit within endorheic catchments, and are relatively small in size (<10 km²). Each dryland visited hosts several such candidates. We classify these candidates in two categories: controls and targets. Controls are sentinel wetlands with in-situ hydrometeorological data logging stations (e.g. interdunal wetlands in Doñana National Park, Southwest Spain), while targets are the remaining sentinel wetlands that we plan to use as a distributed sensor array. Our field visits reveal that in some wetlands, there has been an increase in wetness frequency in recent years.  In the case of low-altitude wetlands, it is almost exclusively because of human interventions (i.e. these are non-sentinel wetlands) and in the high-altitude wetlands, it is because of increased glacier meltwater supply (i.e. these are sentinel wetlands).  By contrast, most sentinel wetlands in low-altitude regions are exhibiting reduced wetness frequency, in some cases dramatically. The next steps are to monitor and evaluate a wider set of hydrodynamic responses to stressors, including by tracking subtle changes at pixel scale and correlating these changes with local to regional climate.  The results will help further demonstrate how wetlands in drylands can act as robust indicators of climate change.

Knowing the wetness dynamics of sentinel and non-sentinel wetlands will help us to identify and separate the various climate and direct human stressors that might impact future water availability and hence water security in the world’s diverse drylands. This separation is crucial for developing targeted management strategies. By further characterising the sensitivity of sentinel wetlands, our research will enhance predictive models of waterbody responses to climate change and provide actionable insights for sustaining water resources amidst ongoing climate changes.

How to cite: Singh, M. and Tooth, S.: Time-series remote sensing and multi-continental field work reveals that wetlands in drylands can be robust indicators of climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11577, https://doi.org/10.5194/egusphere-egu25-11577, 2025.

Loess-Paleosol-Sequences (LPS) are important sedimentary archives that enable to infer climatological parameters during the Quaternary at high temporal resolution. Three isochronous, central European LPS sites (Nussloch, Münzenberg, Hecklingen) were accessed at high temporal resolution by means of heavy mineral, single-grain sedimentary provenance analysis (SPA) using a highly automated, correlative workflow guided by machine learning (Lünsdorf et al., 2023). The goals of this study are (1) to investigate if regional differences exists between the LPS in terms of heavy mineral composition (i.e. Alpine vs. Fennoscandinavian provenance) and (2) if short lived processes that affected the source-to-sink system can be detected.

The studied LPS compose a transect from SW to NE Germany and synchronicity of the archives was controlled by presence of the Eltville tephra (ET; ca. 23.2 – 25.6 ka, Zens et al. 2017) and/or precise OSL age modeling. Thus, the LPS recorded sedimentation during the last glacial maximum. From each LPS 1 m of sediment was continuously sampled in 5 cm intervals, whenever possible centered on the ET. 120 heavy mineral aliquots of the grain size fractions 10 – 30 µm and 30 – 62 µm were analyzed by optical microscopy, Raman spectroscopy and electron probe micro analysis (EPMA) at the single grain level. Resulting in a correlated dataset of optically derived grain parameters (size, shape, roundness, color, etc.), mineralogy and chemical composition for each individual grain analyzed.

First preliminary results suggest that the three LPS are readily differentiated based on heavy mineral composition, supporting a Southern, Alpine and Northern, Fennoscandinavian loess provenance. While heavy mineral ratios and garnet chemical composition reveal abrupt changes in the Southern (Nussloch) and Northern (Hecklingen) LPS. It is assumed that the abrupt changes at the Nussloch site are related to variation in storm intensity with periods of high storm activity reflecting a distal source and periods of low storm activity a more local source. A reasonable explanation for the abrupt change in provenance indicators at the Hecklingen site is the advancement of the Scandinavian Ice Sheet, potentially changing the fluvial drainage pattern and introducing more moraine material to the deflation area.

How to cite: Lünsdorf, N. K., Speck, M.-C., Moine, O., Antoine, P., Fuchs, M., and Lehmkuhl, F.: Isochronous provenance variability during the last glacial maximum revealed by heavy mineral analysis of loess deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12167, https://doi.org/10.5194/egusphere-egu25-12167, 2025.

Groundwater serves as an unsung hero in the worldwide freshwater crisis, supporting agriculture, sustaining communities, and mitigating the effects of climate variability. India leads the world in groundwater consumption. It extracts approximately 250 km³  annually, surpassing the combined withdrawals of China and the United States. Groundwater extraction is expected to escalate in the coming future due to agricultural demands, thereby stressing the already over-exploited groundwater reserves. These findings emphasize the critical need for in-depth research on groundwater systems. The present study focuses on the agro-ecological zones (AEZs) of India, as classified by the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP). AEZs are characterized by unique climatic, soil, and hydrological properties, providing an ideal framework for analyzing groundwater trends at a regional scale. The intricate relationship between rainfall and groundwater levels across different agro-ecological zones was analyzed. The Mann-Whitney U test results reveal significant (p < 0.05) differences in groundwater-levels between normal and dry (deficient rainfall) years in Zones 3, 10, 16, and 19, as well as between normal and wet (excess rainfall) years in Zones 3, 10, 11, 15, 16, and 17, highlighting the pronounced impact of rainfall variability on groundwater availability in these regions. A decline in water table over the two decades (1996-2016) is observed in 57.42% of the total geographical area. Furthermore, regression analysis demonstrated strong correlations (r > 0.7) between annual rainfall and post-monsoon groundwater levels in ten out of the eighteen AEZs considered for the analysis. In addition, Zone 11 ‘Central Highlands’ and Zone 16 ‘Deccan Plateau (Karnataka)’ exhibited stronger correlations at a lag of 1 month, highlighting the delayed response of groundwater to rainfall in these regions. It was also observed that the total area where groundwater extraction during monsoon exceeds recharge, expands from 0.68% in 1996, to 1.21% in 2006, and to 3.89% in 2016. The findings of this study emphasize the need for adaptive, zone-specific strategies to ensure sustainable groundwater management under the changing climate and socio-economic conditions.

How to cite: Feroz, Z. and Jha, M. K.: Unraveling the Link between Rainfall and Groundwater: A Regional Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14669, https://doi.org/10.5194/egusphere-egu25-14669, 2025.

Conventional interpretations of alluvial fan margins attribute their changes to environmental factors such as tectonic activity or climate variations. Under steady dynamic conditions, fan margin (s) is expected to grow continuously, following the time (t) dependence of s~t^(1/3), based on the mass conservation. However, this study aims to propose a new concept that challenges this conventional understanding. A key finding of this research is that the alluvial fan margin can retreat even under constant upstream boundary conditions, a phenomenon significantly influenced by ‘groundwater infiltration’. This study focuses on investigating the role of infiltration process in alluvial fan evolution. Seven tank experiments with varying sediment and water discharge rates were conducted, enabling analysis of fan retreat under constant upstream boundary conditions. Fans typically exhibited continuous progradation, but a critical point was observed where runoff water no longer reached the fan margin, resulting in fan retreat. At this stage, all runoff water infiltrated into the sediment deposit. Applying Darcy’s Law, we found a strong correlation between deposit thickness (dh) and infiltration rate, assuming constant hydraulic conductivity (K_s). Based on these experimental results, a computational model was developed to simulate the alluvial fan trajectories under similar conditions. The findings provide insights into field-scale applications by accounting for infiltration processes on alluvial fans.

How to cite: Shin, H. and Kim, W.: Alluvial Fan Retreat: Tank Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15509, https://doi.org/10.5194/egusphere-egu25-15509, 2025.

In recent decades, the need to quantify and understand water resources in drylands, such as insular volcanic systems, has grown, along with the obligation to assess how climate change might impact them in the future. These resources are constrained not only by climatic, geographic, and geological factors, but also by increasing demand from agronomic, urban, and tourism areas. This, is mostly relevant in the Canary Islands, especially in the coastal region of Maspalomas located in the southern part of Gran Canaria, where an exponential increase in freshwater demand has been observed from 1960 to the present.

Within the framework of the NATALIE project a hydrological model was developed using the Soil and Water Assessment Tool (SWAT) software to estimate the infiltration and recharge rate of Maspalomas aquifers. The water balance results show an average annual precipitation of 272 mm, of which 68% evapotranspires (181 mm/yr). The infiltration rate is estimated at 19% of the precipitation (50.65 mm/yr), equivalent to an annual aquifer recharge of 8.2 hm³.

Gran Canaria faces a unique challenge in water resource management due to strong anthropogenic pressure and the impact of climate change on reserves and available resources. Climate projections towards 2100 suggest a drop of 22.2% in annual precipitation, which would represent a reduction of 34.63 mm/yr in infiltration, i.e., a decrease of 2.59 hm³/yr in groundwater reserves. These results will be key to both prevent scarcity and improve fresh water resource management in volcanic islands.

Keywords: Water resources, Maspalomas, SWAT, recharge rate, climate projection

How to cite: Sariago, R., Marazuela, M. Á., Martínez-León, J., Jimenez, J., Baquedano, C., Gasco, S., Meixueiro Rios, G., Santamarta García-Gil, J. C., and García-Gil, A.: Evaluating Aquifer Recharge in Volcanic Islands: A Case Study of Maspalomas, Gran Canaria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17392, https://doi.org/10.5194/egusphere-egu25-17392, 2025.

We geochemically-fingerprinted a large set of sediments collected from potential source areas (PSAs) in southeastern and southcentral Australia and to compare these data with the record obtained from X-ray Fluorescence (XRF) scanning on a long deep-sea sediment core MD03-2607 obtained offshore Kangaroo Island, South Australia. The entire data set of samples collected on land as well as the downcore measurements were unmixed using the numerical end-member method AnalySize. In this approach, we successfully use the elements Al, Fe, K, Mn, S, Sr and Y to define end members. In addition, the on-land occurrences of the chemical ratios of Zr/Zn, Ti/Rb, Ti/Y and Zr/Rb are used to support the provenance of the chemical end-members. Three main PSA’s are defined: Murray River Basin (MRB), Darling River Basin (DRB) and Kati Thanda – Lake Eyre District (LED), of which the MRB is represented in two different chemical end members. The downcore contributions of these end members in the sediment core are consequently interpreted in terms of fluvial (MRB and DRB) versus aeolian (LED) input.  Consequently, the downcore dominance of sediment-transport modes are interpreted in terms of river runoff versus aeolian input over the last 125 kyr. The downcore palaeoclimate proxies show a dominance of MRB during the interglacial intervals versus a dominance of both LED (dust) and DRB input during the glacial ones, suggesting increased seasonal contrasts during glacial austral winter. See: www.nioz.nl/dust

How to cite: Stuut, J.-B., De Deckker, P., and Hennekam, R.: Provenancing dryland sediments recovered from the marine realm to reconstruct Late Quaternary Australian climate variability  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17564, https://doi.org/10.5194/egusphere-egu25-17564, 2025.

In semi-arid regions, the growing demand for water, particularly for irrigation, accelerates the overexploitation of water resources, often leading to severe scarcity that constrains sustainable economic development. This issue is particularly acute in the Merguellil watershed in central Tunisia, where the impacts of climate change exacerbate the challenges. This study employs the Water Evaluation and Planning (WEAP) system model to analyze current and future trends in surface and groundwater resources in the Merguellil watershed, assessing the combined effects of climate change and human activities on these resources. The primary objective is to identify critical thresholds, evaluate sustainable solutions and guide adaptive water management strategies. An essential element of the study is estimating the demand for irrigation water in the Kairouan plain using high-resolution Landsat 8 imagery to calculate crop evapotranspiration (ETC). Once the required input data from 2000 to 2020 are introduced in the WEAP model, the impact of different scenarios (Climatic and anthropogenic) for the actual and future water balance were evaluated until 2050. The simulation results under the RCP 4.5 climate scenario indicate a significant decline in aquifer levels across the basin; the Kairouan aquifers being particularly impacted. Additionally, scenarios involving the expansion of irrigated areas show a substantial increase in agricultural water requirements. To address these pressing challenges, this study explores multiple management strategies, including improving the efficiency and satisfaction levels of public irrigation systems, optimizing reservoir management during drought periods, and interconnecting existing water infrastructures. Notably, the findings highlight the importance of gradually increasing water transfers to the El Haouareb Dam to meet irrigation demands effectively. Finally, we conclude by emphasizing the importance of proactive and adaptive measures in order to mitigate the adverse impacts of climate change and human activities on water resources in this area. This study highlights the need for integrated, resilient, and sustainable water management practices to ensure the long-term viability of water resources in this vulnerable region.

How to cite: Ataallah, H., Oueslati, I., Le Page, M., and Lili Chabaane, Z.: Sustainable Water Resource Management in the Merguellil Watershed (Tunisia): Assessing the Impacts of Climate Change and Human Activities Using the WEAP Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19705, https://doi.org/10.5194/egusphere-egu25-19705, 2025.

, Are the Vibrationand Equation and Wave Equation of Tidal Forc. These Physicale Equations are the basis for further study of the Wave theory of the Earth. Due to a combination of the Earth Rotation and Tidal Forces, the Earth to Wave constantly. The Wave of the Earth produce many Physical Effect, such as: Harmonic Motion of the Earth, Ocean Tides, and so on. Harmonic Dynamics of the Earth (D) studies only two Physical Effects of crustal Wave Processes: Fatigue Effect and Surge Effect. The Fatigue Fracture of Continents forms Peninsulas or Islands, such as: Madagascar and the Malay Peninsula. Continental Surge Effects create Plateaus and Mountain Ranges, such as the Andes and the Brazilian Highlands.

The Topography of the Ocean Floor records the Move Trackway of the Continents. Reconstructing Continents along their Move Trackway on the Ocean Floor is not the same as " fitting " two Continent Masses into one. For the Reconstruction of the Antarctic Continent and South America: Where the two Continents were connected earlier, they have been pulled in two tails by the Ocean Floor of the Drake Passage. The Continent connecting North and South America has also been severely deformed. The Ocean Floor and the Continents all are constantly contraction and deformation. This contraction makes room for the New Ocean Floor. The area where the two Continents joined before 250Ma is already con not fully " fitting " now. For example, the Continent Side of the Mariana Trench cannot accommodate the Continent of the middle and lower Yangtze River plain and Wuyi Mountain. The Side of Gulf of Mexico of the North American Continent cannot accommodate the Northern tip of South America. Ocean Ridges often develop from Early Rifts in Continents. Therefore, the Ocean Ridge can be used as evidence that the Continent Mass was connected ever to the Continent: The Indian Ocean Ridge at 90° E is the evidence of Australia and Asia once connected. The Southwest Indian Ocean Ridge is the evidence of Antarctica and Africa once connected. The Mid-Atlantic Ridge is evidence that the Americas were once connected to Asia and Africa.

The Reconstruction of Ancient Continent needs to follow three basic constraints: (1) Regression point by point based on time. It follows the Calculation Results of the Harmonic Dynamics of the Earth. Because every centimeter of Continental Drift requires a huge Driving Force. (2) Pay attention to the correspondence between the Topography of the Ocean Floor and the location of the Continent. (3) To consider the " fitting " of the Shape, Geological Structure, Paleomagnetism, and Ancient Plant and Animal communities between Continent Masses. This Reconstruction Method is beneficial for determining the Paleogeographic Location of each City. Provide clearer information on Continental Drift.

How to cite: xin, X.: Harmonic dynamic of the Earth （D）, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4, https://doi.org/10.5194/egusphere-egu25-4, 2025.

Longitudinal river profiles record the uplift history of any tectonically active area. The tectonic forcing causes variation in the topography in the form of channel slope adjustments. The change in the gradient tends to migrate along the river profile at a definite rate. Thus, linear inverse modelling of the river profile can decrypt the spatiotemporal variability of the tectonic uplift rate. This approach relies on the analytical solution of the linear stream incision model. The inversion scheme is applied to the Siang Basin, a sub-basin of the tectonically active  Brahmaputra river system, to provide insight into the uplift history and paleo topography of the basin. The V-shaped Siang valley, located south of the Eastern Himalayan Syntaxis, undergoes a sudden change in slope descending from the Tsangpo gorge. The inversion is performed in the Siang Basin, assuming that the uniform tectonic uplift rate is time-independent but space-invariant. Inversion results reveal a temporal pattern of uplift acceleration between 1-2 Myr ago towards the present. The elevation profile indicates the occurrence of some prominent features that have rejuvenated the topography and increased erosion rates in the past. The base level plot also revealed a drastic fall in the base level since the past 2 Myrs. These results provide insights into the evolutionary history of the Siang Basin.

How to cite: Narayan M, U., Bharti, R., and M Nair, A.: Linear Inversion of Fluvial Long Profiles to deduct the Upliftmet history:A case study of Siang Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-758, https://doi.org/10.5194/egusphere-egu25-758, 2025.

Ischia Island, Italy, is a densely populated, active resurgent volcanic caldera that has undergone rapid deformation during the Holocene. The northern sector of the island, particularly the Casamicciola area, is notable for destructive shallow earthquakes, among the most severe in the Italian seismic catalog; for instance, the 1883 event claimed more than 2300 lives.

Dense vegetation has historically hindered detailed mapping efforts, but the application of drone-based LiDAR has facilitated us a high-resolution neotectonic mapping. Previously, we investigated the fault geometries along the Casamicciola Holocene Graben fault by integrating high-resolution remote sensing data with field-based mapping techniques in the epicentral area of the 1883, Mw 5.0, and 2017, Md 4.0, earthquakes.

The identified fault structures served as initial conditions for numerical simulations using the mantle convection and lithospheric dynamics code ASPECT. The simulations incorporated the effects of fault strength variations, high geothermal gradients, and contrasts in viscosity and mechanical properties on Holocene deformation distribution. Three primary scenarios were tested: (1) deformation driven by regional NE-SW extensional tectonic stress, (2) deformation caused by pressurization of a magmatic intrusion driving resurgence, and (3) deformation resulting from magma depressurization associated with subsidence.

Results reveal that the high deformation rates are primarily driven by shallow magmatic intrusions (~2 km depth) that induce resurgence of the caldera floor, with minimal contribution from regional tectonic stress. Modelled cumulative slip rates during the Holocene, range from 5.0 mm/yr to 31.12 mm/yr, closely matching rates derived from geological data. Additionally, velocity profiles simulating magma intrusion elucidate how the geometry, pressure, and volume of magma govern the asymmetric uplift of the caldera floor. These findings provide insights into the relationship between magmatic processes and earthquake occurrences in the Casamicciola Holocene Graben.

How to cite: Silva Fragoso, A., Naliboff, J., Norini, G., Douglas, D., Nappi, R., Groppelli, G., and Michetti, A.: Exploring the resurgence stage of Ischia caldera by coupling 2D numerical modelling and high-resolution remote sensing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1092, https://doi.org/10.5194/egusphere-egu25-1092, 2025.

We conducted a series of numerical modelling experiments to investigate the mechanism of slab breakoff beneath the Java Trench. The subduction of seamounts, which are characterized by overthickened and buoyant crust, can be a key factor conducive to slab detachment. The modeling experiments explored a range of variable parameters, including whether seamount is involved in the subduction process, the geometry and rheological properties of the seamount, the convergence rate, and the age of subducting oceanic lithosphere. The modelling results demonstrate that the presence of seamount significantly affects the slab breakoff process. Slab breakoff typically occurs at the edges of the subducting seamount. The specific geometry and rheological strength of the seamount emerges as the internal factors in determining whether the slab breakoff will occur. Additionally, the slab age and convergence rate are the external effective controlling factors on the timing and depth of slab breakoff. The evolution of surface elevation caused by seamount subduction differs from that of general oceanic lithosphere subduction, featuring an additional uplift event related to the slab breakoff. Based on our findings, we infer that the participation of seamounts in the subduction process beneath the Java Trench (110°E) has led to the development of low-velocity zone in the mantle wedge and high potassium volcanoes in the Java Island, which has further resulted in a compressional tectonic region in the overriding continental crust. 

How to cite: Ding, W., Liang, D., and Niu, X.: 2-D Numerical modelling Experements on slab breakoff mechanism beneath the Java Trench , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1865, https://doi.org/10.5194/egusphere-egu25-1865, 2025.

Diapiric intrusions induce significant thermal and mechanical changes in the surrounding host rock, including heating and deformation. While previous studies have focused on intrusion formation, few models detail the thermal field evolution during progressive pluton boundary migration, even less, with the associated host-rock deformation. This study aims to simulate the Flamanville granitic diapir's growth and cooling processes to investigate the coupling between thermal evolution and deformation in the aureole during contact metamorphism. The Flamanville intrusion, located in Normandy, northwest France, is a homogeneous, coarse-grained granodioritic diapir with an elliptical geometry, measuring 7.4 km (E-W) by 4.5 km (N-S), and a maximum depth of over 3 km. The pluton intruded Cambrian to Devonian meta-sediments around 318 ± 1.5 Ma. The contact metamorphic aureole extends up to 1 km from the pluton boundary, where intense deformation is characterized by radial shortening, concentric stretching, boudinage, and shear structures. A thermal model is constructed using OpenFOAM 11, an open-source computational fluid dynamics (CFD) platform. To accurately capture the dynamic emplacement of the Flamanville pluton, a custom solver is developed to incorporate an adequate advection term into the thermal diffusion equation, representing the gradual migration of the Flamanville pluton boundary during its emplacement. The solver accounts for the spatial variation in deformation intensity within the aureole, where deformation decreases systematically with increasing distance from the diapir, reflecting observed field patterns of shortening, stretching, and shear structures. Approximately 90 host-rock samples were collected across the aureole to determine maximum metamorphic temperatures using the Laser Raman Spectroscopy Carbon Geothermometer (RSCM) method. The temperatures, ranging from 250°C to 650°C, provide a robust dataset for validating the thermal model and defining the thermal variation in the aureole. This numerical model will simulate the thermal evolution of the host rock during diapiric growth and cooling. By comparing the results with Raman-derived temperature profiles, it is expected to facilitate a quantitative analysis of the evolution of the thermal field within the aureole, offering advanced insights into the thermal regimes governing aureole deformation and contact metamorphism processes.

Key words: Numerical modeling; thermal evolution; aureole deformation; Flamanville granitic diapir; contact metamorphism; Raman Spectroscopy Carbon Geothermometer (RSCM)

How to cite: Chen, Y., Wang, B., Richard, G., Liu, J., Augier, R., Raimbourg, H., Guillou-Frottier, L., Canizares, A., and Chen, Y.: A Thermal Model of the Flamanville Granitic Diapir Deforming Aureole, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3129, https://doi.org/10.5194/egusphere-egu25-3129, 2025.

Mountain regions are globally recognized as biodiversity hotspots. Taiwan is a vivid example, offering an ideal landscape to study the interplay between mountain building and biodiversity. The island resulted from an active arc-continent collision that created a high-relief landscape. The high rates of tectonic uplift, shortening, and extension together with its location in the typhoon belt with high rates of precipitation and erosion results in some of the highest rates of landscape change globally. The short tectonic history and extensive tectonic and geomorphic research provide an opportunity for exploring how mountain building has influenced the island's biodiversity. In this study, we use the landscape evolution model ‘Divide and Capture’ (DAC) to simulate Taiwan’s topography from the onset of uplift to the present day. Landscape evolution modeling predicts the river network patterns, erosion rates, and physical geography in response to tectonic and climatic forcing. We subdivide Taiwan into four major geological domains (Western Foothills, Hsuehshan Range, Central Range, and the extensional Ilan back-arc) and apply horizontal and vertical velocities to each domain subject to a sea level boundary condition that changes in time to simulate the island shape. The resulting model is constrained to fit the exhumation history estimated from low-temperature thermochronometry. Cooling ages from apatite and zircon fission track and helium dating are converted to erosion rates using a thermal model (GLIDE), and used for calibration of the landscape evolution model. The model improves our understanding of Taiwan’s geomorphic history and lays the groundwork for future studies on the interconnection between tectonics, landscape evolution, physical geography, and biodiversity.

How to cite: Krug, C. and Willett, S. D.: Modeling Taiwan’s landscape evolution, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3159, https://doi.org/10.5194/egusphere-egu25-3159, 2025.

The structural deformation of foreland thrust zones is notably complex and remains a central focus in structural geology. This study investigates the deformation characteristics and formation mechanisms of the Hutubi anticline, located in the southern margin of the Junggar Basin, through numerical simulations using Underworld software. By designing three experimental setups, we analyzed the key controlling factors of the anticline's development.

The primary findings are as follows: (1) the simulation results of Experiment 1 exhibit a high degree of similarity to seismic profile characteristics, indicating that the high brittleness of the stratigraphy, pre-existing paleo-uplifts, and faults are the primary controlling factors for the formation of the Hutubi anticline. Furthermore, the localized depression above the paleo-uplift is attributed to lateral adjustments within the plastic layer, which provides a significant structural indicator for identifying paleo-uplifts; (2)Experiment 2 shows that under high-brittleness stratigraphic conditions, pre-existing faults do not play a dominant role in controlling paleo-uplift formation, highlighting other key mechanisms in such settings; (3)Experiment 3 indicates that in high-plasticity stratigraphic environments, multiple uplifts are prone to formation, with pre-existing faults influencing the specific locations of individual uplifts.

Overall, these results provide critical insights into the formation mechanisms of the Hutubi anticline and underscore the value of numerical simulations in experimental design. The findings not only advance the understanding of thrust tectonics in the southern Junggar Basin but also provide a solid foundation for further detailed studies of regional structural evolution.

How to cite: Cui, L., Chen, Y., Huang, Y., Niu, Y., Tao, Y., Liu, Y., and Chen, Z.: Numerical Simulation of the Deformation of the Hutubi Anticline in the Southern Margin of the Junggar Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4669, https://doi.org/10.5194/egusphere-egu25-4669, 2025.

Analogue modeling for Earth Sciences started over two centuries ago as an explorative technique that allowed for the first time unfolding and visualizing a wide range of tectonic processes. While this character remains a compelling feature of analogue models, this experimental methodology has evolved over the last few decades into a quantitative, reproducible and reliable method. Most recent developments aredispersed across scientific journal articles, many behind pay-walls and sometimes hidden in appendices, but no open-access overview exists that brings all this knowledge together.

In the context of the EU research infrastructure EPOS, we are preparing the first comprehensive guide (SPRINGER will publish that as open access) on the state-of-the-art in analogue modeling of geologic processes. This community-built book will be organized into three sections. The first section will serve as a “cookbook” for building analogue models, offering up-to-date guide on scaling down models, selecting suitable analog materials, collecting experimental data, and interpreting those results. The second section will focus on a variety of tectonic processes that can be reproduced in the lab and analyzed using analogue modelling. The final section will emphasize the importance of sharing experimental research data through Open Access data publications and illustrate how analogue models can enhance the Earth Science teaching experience in classrooms. This book will fill a significant gap in the scholarly literature and will serve as a reference and guide for both early-career and experienced researchers as well as reaching out to a broader community of educational and academic teachers. In this presentation, we will share our journey toward this community-effort and give examples of the different sections of the book.

How to cite: Funiciello, F., Buiter, S., Corbi, F., Reitano, R., Rosenau, M., Rudolf, M., Willingshofer, E., and Zwaan, F. and the Authors of the book: Analogue modelling in Geosciences uncovered: a textbook for modern minds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7471, https://doi.org/10.5194/egusphere-egu25-7471, 2025.

Volcano deformation can be a key signal of volcanic unrest and often precedes an eruption. Understanding the relationship between magmatic intrusions and subsequent deformation is crucial for predicting temporal and spatial eruption patterns and thus reducing the impacts of volcanic hazards by enhancing preparedness.

Laboratory analogue models enable the direct study of model volcano subsurface changes. A 2D experimental approach enables subsurface intrusions to be tracked through time and directly compared to the surface displacements. In this study, golden syrup, a viscous fluid, was injected as a magma analogue into a cone-shaped granular material representing an analogue edifice. Images were taken to capture the time-series evolution of the intrusions and associated deformation. The relationship between subsurface intrusions and subsequent surface deformation was investigated by analysing the frame-by-frame pixel displacements using Particle Image Velocimetry (PIV).

Initial findings indicated that the internal compaction of granular material accommodated the radial deformation resulting from the intrusions. Transitions to surface displacement correlated with increased strain rate from the intrusions. Material cohesion influenced material compaction; injections into high cohesion material produced surface deformation when the intrusion approached near-surface regions, compared to injections into low cohesion material (that produced surface deformation when the intrusion was deeper). These findings highlight the role of material (host rock) strength in accommodating deformation via compaction.

In the experiments, an “eruption” occurred when the golden syrup breached the surface of the analogue edifice, and this terminated the experiment. The extrusion location was consistent for each experiment and occurred along the edges of the deforming section at the surface. This finding may improve our ability to locate eruption locations based on surface deformation patterns, enhancing preparedness for deforming volcanoes and their potential eruption location.

How to cite: Mitchell, A., Lane, S., Gilbert, J., Tuffen, H., and James, M.: Analogue Modelling of Intrusion Dynamics in Relation to Internal and Surface Deformation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10571, https://doi.org/10.5194/egusphere-egu25-10571, 2025.

Strike-slip faults are subvertical faults with horizontal movement. They are a fundamental expression of plate tectonics and play a fundamental role in the dynamics of our planet. Transform faults are one of the three types of terrestrial plate boundaries and transcurrent faults occur almost in all tectonic environments on Earth. Understanding their kinematics and dynamics is, therefore, essential for advancing knowledge of plate’s deformation and their seismicity. However, the kinematics and dynamics of the different types of strike-slip faults are still not fully understood. In this study, we use analogue models to investigate four distinct types of strike-slip movement. The strike-slip systems are simulated by deforming a sand-cake on top of two rigid basal acrylic plates. We impose four movements to these plates: 1) two plates moving in opposite directions; 2) one plate stopped and another moving; 3) two plates moving in the same direction but at different velocities and 4) two plates moving in alternating manner in the same direction. The results show some unexpected and insightful outcomes that shed new lights on how some of these systems work. These experiments can be used to gain knowledge on natural prototypes and have implications for our understanding of how strike slip faults operate in different tectonics environments, with important implications for seismic hazards.

How to cite: A. Reis, C., C. Duarte, J., M. Rosas, F., João, M., and Gomes, A.: Analogue modeling of strike-slip faults: a new insight from different kinematic constrains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10756, https://doi.org/10.5194/egusphere-egu25-10756, 2025.

The linearity of current-day ocean floor fracture zones demonstrates the longevity of periods of relatively steady plate motion, characterized by little to very slow movement of the associated Euler poles that describe the motion of the plates on a spherical surface. However, the geologic record also holds evidence that periods of nearly steady plate motion have been interrupted by comparatively rapid plate reorganization events, occurring in less than 10 Myr, that are well described by considering the associated change in the history of the Euler vector directions and/or magnitudes of the affected plates. One category of proposals for the driving mechanism for plate reorganization events makes a case for deeper mantle derived forces instigating surface motion change. A key factor in starting the initiation of mantle driven plate reorganization events may be the mantle’s radiogenically derived internal heating, which acts to form unstable reservoirs of buoyancy below the oldest sections of a plate, adjacent to mature slabs. The potential for internal heating to produce focused hot parcels in the mantle, capable of disrupting the steadiness of convection patterns, was described in previous numerical studies of thermal convection in momentum free fluids. Determination of the degree of success of plate generation is dependent on identifying all potential plate boundaries and inverting the implied intra-plate velocities to test their agreement on a common rotation axis (i.e., the plate’s Euler pole). Here, we utilize an iterative method for implementing a previously described tool for identifying potential plate boundaries in the output of a 3D numerical model of mantle convection. Post-processing model output for a period simulating nearly 150 Myr of evolution we track the history of several neighbouring plates and find that they maintain rigidity well demonstrated by Euler vector fitting of the intra-plate velocities. We find that generally, as their sizes and position change, the plates exhibit motion that changes direction and magnitude slowly. However, we also find that steady evolution can be punctuated by major but relatively short duration reorganization events, that we identify as being driven by the impact of mantle internal heating on the loss of slab-pull at a mature convergent plate boundary.

How to cite: Lowman, J., Guerrero, J., Fairservice, C., Javaheri, P., and Tackley, P.: A rapid tectonic plate reorganization event dynamically modelled by subduction cessation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14030, https://doi.org/10.5194/egusphere-egu25-14030, 2025.

The Huoerguosi-Manasi-Tugulu (HMT) fold-and-thrust belt, which is located in the southern Junggar Basin, has formed in response to contraction during Late Cenozoic. However, the tectonic environment for its formation before Late Cenozoic is still controversial. In this paper, we conducted geometric and kinematic analysis of seismic profiles and outcrop data to reveal the Late Jurassic deformation characteristics in this area. Angular unconformity between Cretaceous and Jurassic is well preserved in Qigu anticline belt south to the HMT fold-and-thrust belt. This unconformity also exists in the HMT fold-and-thrust belt, indicating that HMT fold-and-thrust belt started to active during Late Jurassic. We use surface data, recently collected and processed subsurface seismic refection data, isopach map of Lower Jurassic and balanced sections to propose pre-existing half-graben system developed in the Lower Jurassic with this fold-and-thrust belt. We also use results of a series of scaled sandbox analogue models, where industrial CT apparatus was used to monitor deformation, to simulate the evolution of this fold and thrust belt. We suggest that the segmented shape of the HMT fold-and-thrust belt is a response to the presence of thrust ramps, which were formed during early Jurassic. During late Jurassic and Cenozoic shortening, the Lower Jurassic syn-rift sediments served as major detachment horizon, making a pre-existing normal fault act as a stress concentration zone leading to steeping of a thrust-ramp over the normal fault and cover detachment overstep the underlying half-grabens. Modeling results reveal that the presented structural framework has close resemblance with paleostructures especially in the intracontinental environment, which underwent a complex multicycle evolution process, and provide a new prospective for the interpretation of natural examples.

How to cite: Ma, D., Koyi, H., He, D., Sun, Y., Pan, S., Qu, Y., Wang, H., Wang, Y., Cui, J., and Yang, S.: Modelling inversion of two stages shortening overprinted pre-existing grabens: A case study of Huoerguosi-Manasi-Tugulu fold-and-thrust belt, northern Tian Shan, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14708, https://doi.org/10.5194/egusphere-egu25-14708, 2025.

The Central Mediterranean is a great natural laboratory for many processes related to subduction. Along the Dinaric-Hellenic margin, the rigid Adria microplate indents the Eastern Alps and Dinarides in the north, while the southern part subducts beneath the advancing Hellenides. The Kefalonia Transform Fault System (KTFS) marks the current position of this unique transition between subduction of more buoyant continental lithosphere and less buoyant oceanic lithosphere. The resulting differential convergence is thought to have caused vertical tearing or bending of the subducting slab, although the lack of detailed seismological investigations leaves an open question concerning this geometry.

Slab tears have a significant role in surface evolution around subduction zones. They affect mantle flow, stress propagation within the subducting plate, as well as dynamic topography and volcanism on the surface. However, most models of slab tears investigate their evolution by pre-cutting the subducting lithosphere. We investigated the mechanisms underlying the dynamic formation of a vertical slab tear to interpret geodetic, tomographic, and tectonic observations from around the KTFS. To achieve this, we built a setup with a geometry inspired by the natural subduction system, varied the continental domain's rheology, and introduced an ocean-continent transition zone composed of non-Newtonian analogue materials that allow for strain localisation and slab detachment.

In particular, we wanted to: i) explore how the subducting plate deforms when a tear is forming; ii) observe how the mantle flow reacts to such changes in subduction dynamics; iii) estimate what are the resulting effects on the stress distribution and surface strain on the overriding plate.

We analysed two experimental end-members (i.e., model (A) ocean and continent in lateral contact Vs model (B) separated by non-Newtonian, transitional material) and compared them with the natural observations and the geometry of the subduction system. In both models the rigidity of the continental segment has a critical role in the type of deformation we observe during continental subduction, and controls the amount of stretching, rotation, and continental subduction. The transition zone in model (B) localises deformation, minimising shear and extensional deformation of the continent.

At the end of the experiment, the subduction front geometry of model (B) better reproduces the actual eastern Adriatic margin in correspondence of the KTFS, and the deformation observed on the continental plate is consistent with the structures observed on the field, indicating a certain level of coupling between slab and overriding plate. This similarity without achieving slab tearing suggests that a slab bend may be sufficient to reach the present natural configuration. Consequently, a slab tear may be absent or its extent be limited to a deeper section of the slab.

How to cite: Crosetto, S., Király, Á., Brizzi, S., Funiciello, F., and Faccenna, C.: To tear or not to tear? A comparison between analogue modelling and field observations along the Kefalonia Transform Fault System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16959, https://doi.org/10.5194/egusphere-egu25-16959, 2025.

Title:

Insights into plume-ridge-transform fault interactions as derived from 3D numerical geodynamic modelling of the Azores Triple Junction

Authors: J. Almeida; J. Duarte; F. Rosas; R. Fernandes; R. Ramalho

The Azores archipelago is located at the centre of the Northern Atlantic Ocean and is characterized by a large bathymetric plateau bisected by the Mid Atlantic Ridge (MAR). Over the last 10 Myr, the interaction between the Azores plume, the MAR, and the Gloria Fault zone has led to a complex tectonic history, namely the transition from a R-R-T to a diffuse R-R-R triple junction. The implied tectonic stresses are presently accommodated along several right-lateral oblique extensional structures, which includes the Terceira intra-oceanic rift. To this day, a full understanding of the geodynamic mechanisms behind this change in triple junction configuration is still lacking.

With the present work, we explore how the Azores system was shaped by the complex plume-ridge-transform-fault interactions by conducting 3D viscoelastoplastic geodynamic models. Prior publications concerning this region argued that most NW-SE oriented features – such as the Terceira Rift – form due to the onset of the right-lateral motion between Eurasia and Nubia during the Early Miocene. We thus designed an initial model setup which follows plate reconstructions for Azores and implemented a complying shift from extensional to right-lateral shear tectonic conditions. We further assessed the role of the Azores plume by imposing a thermal anomaly close to the MAR to gain additional insight on the main geodynamic processes which govern this system.

Our results suggest that the primary controlling mechanism behind the formation of the Terceira Rift is the change in tectonic forcing imposed by the change in motion between Eurasia and Nubia during the Early Miocene, acting in tandem with the strain localization effects of the Azores Plateau. The shift towards a relative right-lateral motion between these plates induces a rotation of the local stress field, promoting the localization of transtensional shear along the NE edge of the plateau, closely mirroring the present-day location of the Terceira Rift.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through projects GEMMA (https://doi.org/10.54499/PTDC/CTA-GEO/2083/2021) and through national funds (PIDDAC) – UID/50019/2025 and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).

How to cite: Almeida, J., Duarte, J., Rosas, F., Fernandes, R., and Ramalho, R.: Insights into plume-ridge-transform fault interactions as derived from 3D numerical geodynamic modelling of the Azores Triple Junction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18844, https://doi.org/10.5194/egusphere-egu25-18844, 2025.

How to cite: Uchusov, E., Clementucci, R., Wang, Y., and Willett, S.: Rifting, Cenozoic volcanic and tectonic processes control the landscape of Madagascar , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19272, https://doi.org/10.5194/egusphere-egu25-19272, 2025.

Radiogenic isotopes are widely used for sediment provenance. Sedimentary processes are often neglected but may influence the radiogenic Sr isotope-based provenance [1]. This study explores the radiogenic Pb-Nd isotopic systematics in fine lithic materials from the critical zone of Deccan Basalt (Raigad, Maharashtra). An insignificant Pb and Nd isotope variability of fine lithic materials (<20 mm, <5 mm, and <2 mm) is highlighted in the soil (n=5) and saprolite (n=10) samples. The fine soil and saprolite materials also show statistically insignificant differences in CIA (Chemical Index of Alteration) irrespective of the grain size. However, the soil materials (²⁰⁶Pb/²⁰⁴Pb 17.422±0.513, ²⁰⁷Pb/²⁰⁴Pb 15.354±0.104, ²⁰⁸Pb/²⁰⁴Pb 37.843±0.409, and e_Nd –14.4±2.4) are isotopically different as compared to the saprolite materials (²⁰⁶Pb/²⁰⁴Pb 16.823±0.063, ²⁰⁷Pb/²⁰⁴Pb 15.219±0.013, ²⁰⁸Pb/²⁰⁴Pb 37.374±0.056, and e_Nd –15.7±1.0). The less radiogenic Nd isotopes suggest altered basalt as the source rock composition. Further, the mass balance suggests that one topsoil sample has a significant contribution of ~75–80 % dyke materials exposed nearby. Whereas the other soil samples show <10 % and <6 % contributions from the dyke and UCC-type materials, respectively. These data reaffirms the robust use of Pb and Nd isotopes in sediment provenance. 

Reference:

[1] Dasch, E.J., 1969. Strontium isotopes in weathering profiles, deep-sea sediments, and sedimentary rocks. Geochimica et Cosmochimica Acta, 33(12): 1521-1552.

How to cite: Sahu, S., Singh, S. P., and Joshi, K. B.: Radiogenic Pb and Nd isotopic variability of fine lithic materials in weathering profiles of Deccan Trap, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-764, https://doi.org/10.5194/egusphere-egu25-764, 2025.

Stable water isotopes (δ¹⁸O) in precipitation are one of the most abundant paleoclimate proxies and have been used to infer temperature changes at high latitude and hydrological changes in the tropics. In spite of much progress, however, fundamental questions on the paleoclimate interpretation of stable water isotopes still remain open. Combing water isotope observations and an isotope-enabled TRAnsient ClimatE simulation of the last 21,000 years (iTREACE-21), I will discuss some recent progresses towards the understanding of paleoclimatic inferences of  δ¹⁸O.

I will first discuss the δ¹⁸O for the pan-Asian monsoon region. We show that the widespread δ¹⁸O variability that is coherent over the Asian monsoon continental region is accompanied by a coherent hydroclimate footprint, with spatially opposite signs in rainfall. This footprint is generated as a dynamically coherent response of the Asian monsoon system to meltwater forcing and insolation forcing, reinforced by atmospheric teleconnections. As such, a widespread δ¹⁸O depletion in the Asian monsoon region is accompanied by a northward migration of the westerly jet and enhanced southwesterly monsoon wind, as well as increased rainfall from South Asia to northern China, but decreased rainfall in southern China. 

I will then discuss the temperature effect of polar ice core δ¹⁸O, quantitatively, in a new framework called the Unified Slope Equations (USE) that illustrates the general relationship between spatial and temporal δ¹⁸O-temperature slopes. The application of USE to the Antarctica in model simulations and observations shows that the comparable Antarctica-mean spatial slope with deglacial temporal slope in δ¹⁸O-surface temperature is caused accidentally by the compensation responses between the δ¹⁸O-inversion layer temperature relation and the inversion layer temperature itself.  This finding further leads us to propose a paleothermometer that is more accurate and robust than the spatial slope as the present day seasonal slope of -inversion layer temperature, suggesting the possibility of reconstructing past polar temperature changes using present observations.

I will finally discuss the climate interpretation of tropical alpine ice core δ¹⁸O by combining proxy records with climate models, modern satellite measurements and radiative-convective equilibrium theory. I show that the tropical ice core δ¹⁸O is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of ~7oC . Furthermore, it severs as a Goldilocks indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as ~6oC .

How to cite: Liu, Z.: Understanding Paleoclimatic Inference of Stable Water Isotopes using iTRACE Simulation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1813, https://doi.org/10.5194/egusphere-egu25-1813, 2025.

Enhanced chemical weathering in glacial regions, driven by climate change, is projected to increase the delivery of dissolved and particulate matter to the ocean, significantly disrupting biogeochemical cycles of critical elements which exert a strong influence on the global carbon cycle. This study investigates the elemental and Mg isotope geochemistry of meltwater, suspended particulate matter (SPM), and bedrock samples from Ny-Âlesund, Svalbard, in order to elucidate the link between glacial weathering processes and Mg isotope variations within this glacial environment. Magnesium isotopic compositions (δ²⁶Mg) in meltwaters and SPMs exhibit significant variability, in which meltwater δ²⁶Mg values are in isotopic equilibrium with corresponding SPM values, yielding two distinct isotope fractionation factors depending on the drainage lithology.

A global comparison of water δ²⁶Mg values in Arctic rivers reveals that variability in waterδ²⁶Mg can be attributed to two primary factors, which are a global isotopic equilibrium state that is consistent with what is observed in Svalbard, and an influence of drainage lithology (silicates versus dolomite). Globally, riverine Mg, on average, exhibits a consistent Mg isotopic signature that closely resembles that of the upper continental crust, regardless of the diverse environmental conditions encountered by these river systems. This observation strongly suggests that dynamic interactions between erosion and weathering processes rapidly drive the system towards isotopic equilibrium, which is well supported by this study. 

Overall, this study highlights that the difference in δ²⁶Mg between waters and SPMs can be used as a novel indicator for predicting weathering disequilibrium induced by global warming and other factors influencing the Earth's surface evolution.

How to cite: Ryu, J.-S., Lim, H. S., Song, H., Kim, O.-S., Yang, M., and Vigier, N.: Factors controlling Mg isotopes in meltwater and suspended sediments of Arctic rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1984, https://doi.org/10.5194/egusphere-egu25-1984, 2025.

Tracing the sources and transport pathways of marine sediments provides criticle insights into regional atmospheric and oceanic circulation patterns. Strontium (Sr) and neodymium (Nd) isotopes proxies, when applied to thick and well-dated marine sediment cores, offer a powerful tool for evaluating regional climate dynamics over glacial-interglacial cycles. In this study, we present 13 paired Sr and Nd isotope records for each of two size fractions of lithogenic sediments spanning the past 143 ka, collected from the Benham Rise in the western Philippine Sea. Our goal is to assess the contributions of Asian dust and Southeast Asian volcanogenic sediments under varying global climate conditions. Preliminary results indicate distinct isotopic signatures between size fractions. Volcanogenic Sr isotopic ratios (⁸⁷Sr/⁸⁶Sr = 0.705 to 0.707) were found in sediment grain size >20 μm, while more radiogenic strontium isotope signatures (⁸⁷Sr/⁸⁶Sr = 0.709 to 0.711) were found in sediments in the 2–20 μm fraction. The differences in Sr isotopic signatures between size fractions may partly result from the size effect. Coupled with ε_Nd values, although with some fluctuations, we found shifts in sediment sources over the past 134 ka, indicating decreased contributions of Asian dust source towards the Las Interglacial Highstand. These findings contribute to a deeper understanding of sedimentary processes and environmental shifts in the western Pacific region, offering new perspectives on regional climate.

Keywords: Strontium and neodymium isotopes; Marine sediments; source and transport pathways, Last glacial-interglacial cycle

How to cite: Wang, W.-C. and Liu, Y.-W.: Tracing sediment sources in the western Philippine Sea since 143 ka with Sr and Nd isotopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3043, https://doi.org/10.5194/egusphere-egu25-3043, 2025.

The primary aim of our study is to monitor carbon dioxide concentrations and carry out advanced analyses of the carbon cycle through mass spectrometry-based research in the biosphere within an urban environment in the southern region of Poland. Sampling sites within urban agglomerations are crucial for examining both the similarities and differences between urban areas, including the levels of CO₂ and their sources. Preliminary findings (Sensuła et al., 2023) suggest that continuous monitoring is essential, and incorporating additional research on carbon isotopes in the air may significantly contribute to understanding the carbon cycle in the studied areas.

In 2022, a new laboratory setup was established in Gliwice (Silesia, Poland) to monitor CO₂ levels, enabling precise measurement of CO₂ concentrations in the atmosphere. This system allows for high-time-resolution measurements of the CO₂ molar fraction, as well as the collection and analysis of air samples. Furthermore, the extraction of CO₂ from these samples, followed by ¹⁴C analysis via the MICADAS system, provides valuable data on the isotopic composition of both atmospheric and biospheric samples.

This study presents initial results in the form of a database documenting the molar fraction of CO₂ and ¹⁴CO₂ in atmospheric air samples from the urban area of Gliwice, Poland, covering the period from August 2023 to April 2025. CO₂ concentrations have been measured using a low-cost system (CARBOCAP GMP-343), while ¹⁴C concentrations were determined through the MICADAS technique. Our observations in 2024 indicate that the ¹⁴C values in the air samples ranged from -55‰ to -24‰, while the monthly CO₂ molar fraction varied between 428 and 469 ppm, depending on seasonal changes.

Additionally, since 2019 till 2024 we have investigated pine needles as potential archives of radiocarbon in contemporary environments. This examination focused on the radiocarbon concentration variations in pine needles of different ages, with thirty needle samples collected seasonally in Gliwice. The 14C concentrations in these samples were determined using a liquid scintillation counter, revealing a mean ¹⁴C fraction of 99.83 (69) pMC.

In January 2025, we began calibrating a new system based on the CRDS (cavity ring-down spectrometer) technique to analyze the stable isotopic composition of atmospheric gases (CO₂ and CH₄).

This work was supported by the following contracts and grants: the Initiative of Excellence – Research University programme implemented at the Silesian University of Technology, in the years 2022-2024 as part of a grant for cutting-edge research grant no.: 14/020 / SDU / 10-21- 03; project title: Analysis of CO₂ changes in the atmospheric air: construction of a new module to monitor CO2 concentration in the air; EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027 : The modern methods of
the monitoring of the level and isotopic composition of atmospheric CO₂ (project no.FESL.10.25-IZ.01-06C9/23-00) implemented at the Silesian University of Technology (2024-2026).

How to cite: Sensuła, B., Ustrzycka, A., and Michczyński, A.: Dynamics change in carbon cycle in contemporary environment in urban area in Gliwice, Poland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3149, https://doi.org/10.5194/egusphere-egu25-3149, 2025.

This study presents a reconstruction of Holocene mean July air temperatures based on chironomid assemblages preserved in the sedimentary record of Laguna de la Mosca (LdlMo), an alpine lake in the Sierra Nevada of southern Spain. The LdlMo record reveals that the highest temperatures occurred during the Early and early-Middle Holocene, between 8500 and 7000 cal yr BP, followed by a significant cooling event. During the Middle Holocene, temperatures stabilized, but a second major cooling event occurred at approximately 4200 cal yr BP, possibly associated with the 4.2 kyr event. Throughout the Late Holocene, temperatures generally remained low, punctuated by warming episodes between 2300–1600 cal yr BP during the Iberian Roman Humid Period (IRHP) and around 1000 cal yr BP during the Medieval Climate Anomaly (MCA). The lowest temperatures were recorded at the end of the Little Ice Age (LIA), circa 1800 CE. Since ~1955 CE, a rapid and pronounced warming trend of 2.5°C has been observed, driven by anthropogenic climate change. This study shows the amplification of recent warming at high elevations, highlighting the vulnerability of these fragile and unique alpine environments to the impact of climate change.

This work was funded by grants BIOD22_001 and BIOD22_002, funded by Consejería de Universidad, Investigación e Innovación and Gobierno de España and Unión Europea – NextGenerationEU and PID2021-125619OB-C21 funded by the Ministerio de Ciencia e Innovacion of Spain, the Agencia Estatal de Investigacion and the Fondo Europeo de Desarrollo Regional FEDER MCIN/AEI/10.13039/501100011033/FEDER, UE

How to cite: Jiménez-Moreno, G., Prats, N., Heiri, O., García-Alix, A., Anderson, R. S., Jiménez-Espejo, F. J., and Pérez-Martínez, C.: Chironomid-based Holocene summer temperature dynamics from southern Spain , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3260, https://doi.org/10.5194/egusphere-egu25-3260, 2025.

The "Shuram Excursion (SE)" stands as the largest known negative carbon isotope excursion (CIE) in geological history and is thought to represent the largest carbon cycle perturbation, possibly pivotal in the evolution of complex life forms and, thereafter, the Cambrian biotic explosion. Apart from the Shuram Formation at its type locality in Oman (the maximum depleted stable carbon isotopic ratio [δ¹³C value] in carbonate [peak δ¹³C_Carbonate] of ~ –12 ‰), comparable negative CIE of similar ages has also been documented from different parts of the globe, among which the well constrained globally recognized SE sections are the Wonoka Formation of Australia (peak δ¹³C_Carbonate of ~ −10 ‰), the Doushantuo Formation of South China (peak δ¹³C_Carbonate of ~ −14 ‰), and the Rainstorm Member in the Johnnie Formation of Death Valley, California (peak δ¹³C_Carbonate of ~ −11‰). Considering the inherent problem with the exact depositional age estimation for sedimentary rocks, although all the global locations show similar CIE patterns, the peak δ¹³C_Carbonate values, and stratigraphic thicknesses vary from section to section. Because of these disparities, two distinct perspectives exist regarding the origin of the SE. While one group argues that a globally synchronous diagenetic event is responsible for the SE CIE, the other suggests it is a record of the temporal variation in the primary δ¹³C composition of the seawater dissolved inorganic carbon (DIC) and, hence, represents the actual carbon cycle perturbation. Based on the preliminary data obtained by other studies from the late Neoproterozoic Lesser Himalayan Krol Formation, previous workers tentatively suggested that the succession may contain the SE. However, because of the composite nature of the studied sections and the large spread in carbonate δ¹³C values in lithologically correlative stratigraphic (temporal) intervals, the proposition was not confirmed. So, the current study tries to recognize the possible SE CIE in the Lesser Himalayan Krol Formation, India, by studying continuously measured structurally undisturbed sections by employing vigorous fieldwork, detailed high-resolution carbonate δ¹³C data, and Pb-Pb dating of the carbonates after careful thin section and cathodoluminescence (CL) based screening for any possible diagenetic alterations. The transmitted light and CL-based petrographic observation, along with bulk and fabric-specific (micro-sampling) carbonate δ¹³C data, suggests the presence of distinct negative CIE with a peak δ¹³C_Carbonate value of ~ –10.7 ‰ (CIE magnitude of ~10.7 ‰) in the Lesser Himalayan Krol Formation. The depositional age of ~560 ± 12 Ma, estimated by Pb-Pb dating of the carbonate across this CIE, further suggests the possible presence of SE CIE in the investigated section.

How to cite: Pradhan, D., Bera, M. K., Nandi, A., and Vadlamani, R.: Does the Largest Recorded Negative Carbon Isotope Excursion from the Neoproterozoic Krol Formation (India) Represent a Globally Synchronous Diagenetic Event?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4264, https://doi.org/10.5194/egusphere-egu25-4264, 2025.

⁴¹Ca (half-life = 99 ka) is a cosmogenic radionuclide that has long been proposed as a promising dating tracer for geological and archaeological samples from Middle and Late Pleistocene [1]. Calcium is abundant and has a residence time of 800 ka in the oceans, much longer than the half-life of ⁴¹Ca. This has led to the expectation of a uniform distribution of ⁴¹Ca/Ca ratios in oceans around the globe. Ocean deposits acquire the global seawater value of ⁴¹Ca/Ca upon the initial formation. Since ocean deposits are shielded from cosmic rays by overlying seawater, no cosmogenic ⁴¹Ca is produced as deposits grow older. These conditions are ideal for ⁴¹Ca dating of marine deposits.

However, the ⁴¹Ca/Ca ratio is typically less than 10^⁻15 in the environment, posing significant challenges for their measurements. Recent advances in Atom Trap Trace Analysis (ATTA) [2] have enabled the detection of ⁴¹Ca in geological samples [3]. The lowest ⁴¹Ca/Ca ratio measured so far is 3 × 10⁻¹⁸, found in a foraminifer sample from the Pacific Ocean.

We measured the ⁴¹Ca/Ca ratios in seawater samples from various depths in oceans around the world and mapped the spatial distribution of ⁴¹Ca. This work identifies the critical initial ⁴¹Ca/Ca value for ⁴¹Ca dating of marine deposits. Building on these findings, we performed ⁴¹Ca dating on foraminifera and coral samples from the Pacific, South China Sea, and Southern Ocean, and compared the results with those obtained from other dating methods. Meanwhile, we are exploring the feasibility of applying ⁴¹Ca dating to other geological and archaeological samples.

References:

[1] Raisbeck, G., Yiou, F. Possible use of ⁴¹Ca for radioactive dating. Nature 277, 42–44 (1979).

[2] A Primer on Atom Trap Trace Analysis (ATTA). http://atta.ustc.edu.cn/en-us/events/attaprimer.html

[3] Xia, TY., Sun, WW., Ebser, S. et al. Atom-trap trace analysis of ⁴¹Ca/Ca down to the 10^–17 level. Nat. Phys. 19, 904–908 (2023)

How to cite: Sun, W.-W., Bender, M., Huang, E.-Q., Huang, H., Jiang, W., Lu, Z.-T., Tian, J., Xia, T., Yan, Y.-Z., Yang, G.-M., and Zhu, H.-M.: 41Ca dating of marine deposits from Middle and Late Pleistocene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4937, https://doi.org/10.5194/egusphere-egu25-4937, 2025.

The Sea of Okhotsk, situated at the northern boundary of the East Asian summer monsoon's domain, represents the southernmost region in the Northern Hemisphere where perennial sea ice develops year-round. It serves as a critical source of ventilation for modern North Pacific Intermediate Water and is highly sensitive to global climate change, making it an ideal natural laboratory for studying environmental changes. Despite its importance, our understanding of the basin-scale environmental evolution of the Sea of Okhotsk remains limited. This study addresses these gaps by compiling paleoenvironmental records from several sediment cores in the Sea of Okhotsk. We recalibrated the age models of these cores to reconstruct the histories of sea surface temperature (SST), sea ice activity, surface productivity, and intermediate water ventilation since 30 ka. Based on the reconstruction, we propose the conceptual modes of environmental evolution: the "glacial type," dominated by sea ice, and the "interglacial type," controlled by both sea ice and ocean currents. During the Last Glacial period (30 - 18 ka), the Sea of Okhotsk experienced low SSTs, extensive sea ice coverage, weak intermediate water ventilation, and reduced surface productivity. In contrast, the Late Holocene (< 6 ka) was characterized by higher SSTs, diminished sea ice, robust intermediate water ventilation, and increased surface productivity, with siliceous ooze being the dominant sediment component. Notably, during the Bølling-Allerød (14.7 - 13 ka) and Preboreal (11 - 9.7 ka) warm periods, the marine environment resembled the "interglacial type" but featured anoxic intermediate waters. During Heinrich Stadial 1 (18 - 14.7 ka) and the Younger Dryas (13 - 11.7 ka), environmental regimes were generally similar to the "glacial type" but with enhanced intermediate water ventilation. Since 30 ka, the evolution of environmental factors in the Sea of Okhotsk has been shaped by external forcings, internal feedbacks, and climate processes at both high and low latitudes, underscoring the complex interplay of factors influencing this dynamic region.

How to cite: Zou, J., Wang, Q., and Shi, X.: Basin-scale environmental changes in the Okhotsk Sea over the last 30,000 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5402, https://doi.org/10.5194/egusphere-egu25-5402, 2025.

Palaeoclimatic reconstructions rely heavily on accurate interpretation of isotopic signal, retrieved primarily from fossil biominerals. Evaluating whether these geochemical proxies reflect original environment is often a challenge. In our recent study we have attempted to illustrate fossil vertebrate dental tissue geochemistry and, by inference, its extent of diagenetic alteration, using quantitative, semi-quantitative and optical tools to evaluate bioapatite preservation. Here we present visual comparisons of elemental compositions in fish and plesiosaur dental remains ranging in age from Silurian to Cretaceous, based on a combination of micro-scale optical cathodoluminescence (CL) observations (optical images and scanning electron microscope) with in-situ minor, trace and rare earth element (REE) compositions (EDS, maps and REE profiles), as a tool for assessing diagenetic processes and biomineral preservation during fossilization of vertebrate dental apatite. Tissue-selective REE values have been obtained using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), indicating areas of potential REE enrichment, combined with cathodoluminescence (CL) analysis. Energy dispersive X-ray spectroscopy (EDS) mapping was also used to identify major elemental components and identify areas of contamination or diagenetic replacement. We conclude that the relative abilities of different dental tissues to resist alteration and proximity to the exposure surface largely determine the REE composition and, accordingly, the inferred quality of preserved bioapatite.

How to cite: Žigaitė-Moro, Ž., Cowen, M., de Rafélis, M., Ségalen, L., Kear, B., and Dumont, M.: Visualizing and quantifying biomineral preservation in fossils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5723, https://doi.org/10.5194/egusphere-egu25-5723, 2025.

The carbon cycle perturbations in geological history are preserved in the form of changes in stable carbon isotope ratios (δ¹³C values) in different carbon-bearing sedimentary archives. The carbon cycle perturbation that occurred across the Paleocene-Eocene boundary (~56 Ma) is known as the Paleocene Eocene thermal Maximum (PETM). After more than three decades of research, the exact magnitude of the negative carbon isotope excursion (CIE) is still fuzzy. The shallow marine sedimentary archive, deposited far above the lysocline, is considered to be the best archive to quantify the carbon cycle perturbation because the deep marine (carbonate) was likely to be affected by carbonate dissolution and terrestrial sedimentary records influenced by different climatic parameters. However, different biotic and abiotic processes could influence the magnitude of the CIE during the perturbed carbon cycle-climate state in a shallow marine environment. For this reason, the present study investigated the early Paleogene marine carbonate rocks deposited in the eastern Tethyan Sea (Ladakh, NW India) to check the possible presence of the PETM CIE and test whether shallow marine carbonate is a good archive for measuring the CIE magnitude. The presence of age-diagnostic larger benthic foraminifera and detailed micro-facies analysis indicates the investigated shallow marine carbonate rocks were deposited during the ~56 to 54 Ma (Shallow Benthic Zone - 4 to 7) and are likely to hold the PETM CIE. The secular variation in the δ¹³C values of unaltered bulk carbonate, screened through the cathodoluminescence microscopic study, reveals a PETM CIE magnitude of -3.6 ‰.  The observed CIE magnitude is similar to the globally accepted CIE magnitude (-4 ± 0.4 ‰) for PETM and suggests that shallow marine carbonate can be used to assess the magnitude of PETM and other carbon cycle perturbations.

How to cite: Dadabhau Raskar, T., Samanta, A., and Kumar Bera, M.: Can shallow marine carbonate faithfully preserve the true signal of carbon cycle perturbation?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6511, https://doi.org/10.5194/egusphere-egu25-6511, 2025.

Ursus spelaeus, the Late Pleistocene a cave bear is known from numerous accumulations found in the fossil sector of caves situated in the Carpathian and Apuseni Mountains. In this study, we present approximate population variation in time using the temporal distribution and interval frequencies of radiocarbon ages from literature. Most of the dated skeletons were preserved in caves. The data suggest that, during the entire Marine Isotope Stage 3 (MIS 3) interval,  caves were serving as a shelter for U. spelaeus, with the oldest dated bone indicating ages over 60,000 and the youngest ones less than 30.000 years cal BP. Histogram plots of over 110 radiocarbon data from different caves of the Carpathian and Apuseni Mountains as Cioclovina Uscată, Peștera (Cave) cu Oase, Peștera Muierii, or Peștera Urșilor, respectively, show a maximum expansion of the cave bear population between 50,000 and 40,000, a decline between 40,000 and 35,000 and a partial recovery from 35,000–30,000 years cal BP. Radiocarbon data of Homo sapiens remains, younger than 35,000 years cal BP, support the fact that H. sapiens accessed the same caves where the cave bear persisted to hibernate. Besides general cool conditions and restricted food sources, the presence of H. sapiens constituted an additional stress factor driving the cave bear to extinction (Bojar et al., 2024).

References

Ana-Voica Bojar, Natalia Piotrowska, Victor Barbu, Hans-Peter Bojar, Fatima Pawełczyk, Andrei Smeu & Ovidiu Guja: Ursus spelaeus (Rosenmüller, 1794) during the MIS 3: new evidence from the Cioclovina Uscată Cave and radiocarbon age overview for the Carpathians, Isotopes in Environmental and Health Studies, DOI: 10.1080/10256016.2024.2376730

How to cite: Bojar, A.-V., Barbu, V., Piotrowska, N., Bojar, H.-P., Smeu, A., Pawełczyk, F., and Guja, O.: Ursus spelaeus (Rosenmüller, 1794) during the MIS 3: temporal population distributions and relationship with climatic fluctuations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8827, https://doi.org/10.5194/egusphere-egu25-8827, 2025.

Conturines cave opens at 2775 m a.s.l. in the Dolomites (Northern Italy), hundreds of meters above the modern tree line. The cave is about 200 m long and comprises a single ascending paleophreatic conduit. The entrance of the cave is located at the base of the headwall of a former glacial cirque, testifying its pre-Pleistocene origin. Large parts of the cave floor are covered by an extensive (up to 3.5 m thick) flowstone and large stalagmite formations are present in the inner part of the passage, where the flowstone starts. All these large formations are inactive, partly corroded and dissected by fractures. The catchment area is a sharp ridge devoid of vegetation and soil, and the dripping water in the cave is undersaturated with respect to calcite, leading to the slow demise of these large speleothems.

Several drill cores covering the entire stratigraphy of the flowstone were obtained along the course of the gallery, the longest reaching bedrock at 3.5 m depth. Multi-proxy analyses of the two longest cores drilled approximately 5 m apart in the proximal part of the flowstone replicate well. Multiple magnetic reversals are preserved in the flowstone stratigraphy. According to preliminary U-Pb dating, speleothem deposition began ca. 5.5 - 5.0 Ma ago, likely coincident with the end of the Messinian Salinity Crisis in the Mediterranean, and continued intermittently until around 3 Ma. This uplifted ancient speleothem record provides a rare window into the Neogene at high resolution.

How to cite: Spötl, C., Koltai, G., Scholger, R., Wang, J., Knipping, M., and Cheng, H.: Ancient speleothem giant preserved in a high-Alpine cave (Dolomites, N Italy): rare insights into the Neogene, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9061, https://doi.org/10.5194/egusphere-egu25-9061, 2025.

LA-ICP-MS, and XRD were used to investigate representative samples of gypsum collected from four deposits, all of them of Badenian age: Cheia (Transilvanian Basin, Cluj county), Ivancauti (Moldavian Platform, Botosani county), Negresti (Moldavide, Neamt county) and Moinesti (Moldavide, Bacau county) deposits were selected. The main objective of this study consisted of a geochemical, crystallo-chemical and economical potential detailed characterization of these deposits.

Accordingly, the LA-ICP-MS permitted determining the mass fractions of 21 elements including 10 REE (La, Ce, Nd, Sm, Eu, Gd, Er, Yb and Lu), as well as of Mg, P, Ti, Fe, Ni, Sr, Y, Ba, Pb, Th and U. Their content was interpreted considering their presence in the upper continental crust (UCC), sea water and chondrites.

Concerning the investigated elements, excepting for the REE ones, the LA-ICP-MS determinations evidenced in the case of Sr and U contents comparable with the UCC ones. It worth mentioning the presence of Sr of which mass fractions of 930 ± 47 and 545 ± 100 mg/kg in the Ivancauti and Cheia samples exceeded the UCC one of 330 mg/kg by a factor up to three, in good agreement with reported data concerning the lagunar Mediterranean gypsum.

At its turn, the U showed mass fractions varying between 1.76 ± 0.94 mg/kg in the case of Moinesti deposit and 2.93 ± 0.8 mg/kg for the Cheia samples, having the same order of magnitude as the UCC one of 2.7 mg/kg. On contrary, the maximum value of Th mass fraction of 68 ± 31 mg/kg was 155 times smaller than the value reported for UCC one. By comparing the ratio of the mass fractions of Th and U in investigated samples with the same ration of the sea water, the gypsum samples ratio of 0.02 significantly overpasses the sea water ratio of 0.0015, suggesting rather a terrigenous origin.

The great variability of the mass fractions of the investigated 11 elements makes possible the discriminant analysis of their distribution by considered elements as variable and deposits as cases. Indeed, a Root 2 vs. Root 2 bi-plot evidenced the presence of four clusters, the Negresti and Moinesti ones relatively closer and differing by the Ivancauti and Cheia ones with respect of Root 1, while Root 2 discriminates only the Cheia one with respect with the other three, i.e. Ivancauti, Negresti and Moinesti.

Likely, the investigated REE distribution showed for all of them mass fractions lower with one order of magnitude and more than the corresponding UCC values, e.g., varying from 5.59 ± 2.82 mg/kg for Yb in Ivancauti samples to 0.21 ± 0.04 mg/kg in the case of Lu in Moinesti gypsum. A peculiarity which we observed for all samples consisted of positive Ce and Eu anomalies. If the Ce anomaly could be associated to an oxidative depositional medium, the positive Eu anomaly could be associated to an increased content of Sr, but these facts need more investigations to be elucidated, especially as this anomaly was evidenced for all investigated samples, regardless the deposit.

How to cite: Dumitras, D.-G., Duliu, O. G., Luffi, P. I., Marincea, S., Sirbu Radasanu, D. S., Iancu, A. M., and Persa, D.: Comparative analysis of gypsum from four different deposits of Badenian age in Romania, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10131, https://doi.org/10.5194/egusphere-egu25-10131, 2025.

This study explores Late Holocene climate variability and environmental transitions in the NW Iberian Peninsula by analyzing organic biomarkers (n-alkanes) and their isotopic signatures (δ¹³C and δD) from two contrasting lake systems: Lake Ocelo, a mountain lake (1517 m a.s.l.) located at a crucial point between the Atlantic and Mediterranean bioclimatic regions, and Lake Doniños, a coastal back-barrier perched lake (2.5 m a.s.l.) within the sub-Atlantic climatic domain. Lakes at varying altitudes provide complementary paleoenvironmental records that capture diverse ecosystem responses to past climate changes across vertical gradients.

In both Lake Ocelo and Lake Doniños, δD values reflect hydrological variability. In Ocelo, long-chain n-alkanes indicate terrestrial vegetation as the main source of organic matter. δD values (~-190‰ to ~-160‰) reflect wetter and cooler conditions during the Older Subatlantic (OSA; ca. 800-200 BCE), the Dark Ages (DA; ca. 300-750 CE) and Little Ice Age (LIA; ca. 1300-1900 CE), contrasted with warmer and drier conditions during the Roman Warm Period (RWP; ca. 200 BCE-300 CE), Medieval Climate Anomaly (MCA; ca. 750-1100 CE) and the Industrial Era (IE; ca. 1850 CE-present). Similary, in Doniños, δD values during the MCA became more positive, suggesting drier conditions. The MCA-LIA transition (ca. 1100–1300 CE) in Ocelo shows a shifts to wetter and cooler conditions, with δD and δ¹³C values declining. In Doniños, between 1200 CE and 1585 CE, δD became more positive, suggesting episodic drying and marine influence, likely linked to increased storminess. Also, δ¹³C rose sharply between 1400 CE and 1550 CE, during the LIA, possibly indicating increased nutrient input associated with climatic fluctuations or marine incursions. After a hiatus spanning 1585-1700 CE, δD stabilized at its most positive levels, marking reduced hydrological variability and arid conditions. Post-1850 CE, δD and δ¹³C trended toward more negative levels, reflecting increased meteoric water input due to wetter climate conditions or anthropogenic watershed. Additionally, the lowering of δ¹³C values during the IE may also reflect the Suess effect from fossil fuel combustion.

In Ocelo, δ¹³C data align with δD trends, reflecting shifts in vegetation composition and water stress, with relative enrichment in δ¹³C during the RWP and MCA suggesting warmer and drier conditions, while more negative δ¹³C during the LIA and DA reflects cooler and wetter conditions.

These findings emphasize the utility of biomarkers in reconstructing regional climate variability and the contrasting responses of mountain and coastal lakes to Late Holocene transitions. Despite their geographical proximity (185 km), both lakes reflect different climatic influences: Lake Ocelo records broader fluctuations linked to its bioclimatic position, while Lake Doniños is influenced by local processes, including marine intrusions and anthropogenic impacts. Similarities include drier conditions during the RWP and MCA in both lakes, while differences emerge during the LIA, where marine influence and storminess played a larger role in Lake Doniños. 

This work is supported by Grants PID2019-107424RB-I00 and PID2022-139775OB funded by MCIN/AEI/10.13039/501100011033, with the latter also co-funded by “ERDF A way of making Europe”. Xunta de Galicia also supports this work through projects ED431F 2022/18 and ED431B 2024/03.

How to cite: Fernández-Pérez, U., Bao, R., Schefuß, E., Rodrigues, T., Sáez, A., Raposeiro, P., Prego, R., Carballeira, R., and Hernández, A.: Late Holocene Climate Contrasts in NW Iberian Lakes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11318, https://doi.org/10.5194/egusphere-egu25-11318, 2025.