Today, Antarctica appears as a continent locked in eternal ice and snow, but its sedimentary record preserves rich fossil archives of past life. Because present-day Antarctic landmasses have already been circling in polar latitudes for more than 300 million years, many Antarctic fossil occurrences derive from past high-latitude palaeoecosystems without modern analogue. Of special importance are exceptional plant-fossil assemblages—some classic, some only recently discovered—from the early Mesozoic of the Transantarctic Mountains. These yield exquisitely preserved plant compressions and anatomically preserved biotas in silicified peat and wood, allowing detailed insights into the biology and ecology of past polar forests during times of global warmth. The Late Triassic vegetation of Gondwana is particularly well-known. It was dominated by Dicroidium seed-ferns, conifers, ginkgoes, cycads, and diverse fern communities, and documents sophisticated adaptations to extreme seasonal light regimes, including widespread deciduousness, growth dormancy, and specialized understorey life strategies. There is now increasing evidence that such high-latitude ecosystems acted as evolutionary refugia during major biotic crises. The iconic Triassic Dicroidium plants, for example, survived the end-Triassic mass extinction in Gondwanan high-latitude populations and persisted there long into the Jurassic, far beyond their time of disappearance at lower latitudes. Recent discoveries from previously unexplored regions of northern Victoria Land substantially expand this perspective, revealing unexpected growth strategies, complex ecological interactions, and evidence for extreme evolutionary stasis. Taken together, the fascinating fossil record of the Transantarctic Mountains highlights the varied roles of high-latitude palaeoecosystems in plant evolution during times of global change.

How to cite: Bomfleur, B.:  The green poles of a warmer past: how Antarctic polar forests shaped plant evolution , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23290, https://doi.org/10.5194/egusphere-egu26-23290, 2026.

North Atlantic DeepWater (NADW), the return flow component of the Atlantic Meridional Overturning Circulation (AMOC), is a major inter-hemispheric ocean water mass with strong climate effects but the evolution of its source components on million-year timescales is poorly known. Today, two major NADW components that flow southward over volcanic ridges to the east and west of Iceland are associated with distinct contourite drift systems that are forming off the coast of Greenland and on the eastern flank of the Reykjanes (mid-Atlantic) Ridge. Here we provide direct records of the early history of this drift sedimentation based on cores collected during International Ocean Discovery Programme (IODP) Expeditions 395C and 395. We find rapid acceleration of drift deposition linked to the eastern component of NADW, known as Iceland–Scotland Overflow Water at 3.6 million years ago (Ma). In contrast, the Denmark Strait Overflow Water feeding the western Eirik Drift has been persistent since the Late Miocene. These observations constrain the long-term evolution of the two NADW components, revealing their contrasting independent histories and allowing their links with climatic events such as Northern Hemisphere cooling at 3.6Ma, to be assessed.

How to cite: Sinnesael, M. and Karatsolis, B. T. and the Expedition 395 Scientists: Onset of strong Iceland-Scotland overflow water 3.6 million years ago, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9577, https://doi.org/10.5194/egusphere-egu26-9577, 2026.

The hydrological response of a basin is fundamentally controlled by geomorphic processes, structures, and physiographic characteristics. Horton’s geomorphological laws, basin topology, and kinematic properties have long been employed to derive flood response in ungauged basins through various Geomorphological Instantaneous Unit Hydrograph (GIUH) frameworks. This study investigates ten ungauged tributary sub-basins of the Shilabati River in eastern India to analyse how basin morphometry and topology regulate travel-time distribution of water particles and flash-flood potential. The Width Function Instantaneous Unit Hydrograph (WFIUH), a GIUH variant, is applied to derive the geomorphological control on peak flow and time to peak, while the morphometric analysis is performed to investigate the effect of basin characteristics on these hydrologic response parameters. The WFIUH is obtained using the flow length extracted from the SRTM DEM, together with spatially variable and fixed hillslope velocities estimated from land use-land cover and slope using the Soil Conservation Services (SCS), uniform-flow, and Manning’s velocity formulae. Due to the absence of observed streamflow, WFIUH results are evaluated against the Geomorpho-climatic Instantaneous Unit Hydrograph (GcIUH) derived from climate-dependent channel velocity and drainage network topology, as well as observed flood events. 
Results show that all variable-velocity WFIUHs have longer time bases and a lower peak flow than fixed-velocity WFIUHs, because the highest velocity cells are associated with the smallest drainage contributing areas. The SCS-based variable velocity WFIUH aligns with the GcIUH, reproducing both the peak flow and time to peak of the IUH more accurately compared to the other methods. Small, circular, and comparatively steeper sub-basins exhibit shorter times to peak (8.5-10.5 hours), indicating a high flash-flood potential, mainly in sub-basins 3-6. On the contrary, elongated and well-bifurcated sub-basins reveal slightly delayed peaks (10.5-15.5 h) but remain capable of producing moderate-to-high floods due to their larger drainage areas, as confirmed by the flash flood event in 2025 in sub-basins 1, 8-10. Correlation analysis reveals that circularity ratio, relief ratio, and hypsometric integral are positively associated with peak flow, suggesting enhanced flow synchronization in compact and steep sub-basins. In contrast, time to peak shows moderate to strong negative correlations with these parameters and positive correlations with stream length and bifurcation ratios, indicating delayed response in elongated and highly branched drainage networks due to dispersed flow paths.
Therefore, basin morphometry and drainage network topology effectively govern hydrologic responses of the sub-basins. The spatially variable SCS velocity-based WFIUH provides a more realistic depiction of hydrologic response in ungauged sub-basins. Hence, this method is well-suited for event-based lumped hydrological modelling as well as for sub-basin prioritization in flash flood risk assessment.

How to cite: Das, T. and Das, S.: Geomorphic controls on flood response using the Width Function Instantaneous Unit Hydrograph framework , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-570, https://doi.org/10.5194/egusphere-egu26-570, 2026.

Coastal protection infrastructures such as rubble-mound breakwaters (RMBs) demand frequent geometric inspection to quantify armor-layer dynamics and support reproducible structural monitoring. While UAV-based photogrammetry and LiDAR are established reference techniques for rapid 3D mapping, high revisit rates remain operationally constrained by wind sensitivity, sensor payload limits, and regulatory flight restrictions. Videogrammetry complements these approaches by increasing inter-frame overlap and mitigating missed-trigger acquisitions, especially useful in complex coastal scenes (e.g., those affected by occlusions between armor units and block interstices). As in conventional photogrammetry, videogrammetry relies on image redundancy and self-calibration rather than highly sophisticated instrumentation. Despite this potential, consumer-grade action cameras remain scarcely validated for multi-epoch 3D monitoring in coastal engineering, mainly due to wide-angle lens distortion and coarse onboard GNSS geotag precision.

This study assesses pole-mounted GoPro videogrammetry for multi-temporal 3D relative change detection in the emerged portions of a detached rubble-mound breakwater at Cabedelo do Douro (PT). Two survey epochs were acquired in July 2024 and November 2024 to characterize the above-water zone, inspecting the seaward slope, the landward armor-toe transition, and the horizontal crest platform segment at one of the heads of the RMB. Frames were extracted at 1 Hz and processed in Metashape using an SfM-MVS (Structure-from-Motion Multi-View Stereo) self-calibrating camera model. Multi-epoch point clouds were coregistered in CloudCompare with ICP (Iterative Closest Point) refinement over stable crest and toe areas, and 3D changes were quantified using M3C2 (Multiscale Model-to-Model Cloud Comparison), generating signed distance maps and detection histograms. A concurrent UAV-RTK survey, supported by additional GNSS-measured ground control points (GCPs), served as a geometric benchmark.

Mean ActionCam-to-UAV sensor offsets were +0.06 m, confirming that, despite potentially unstable absolute georeferencing in GoPro-derived reconstructions, the resulting point clouds preserve sufficient geometric and scale consistency to support relative multi-temporal 3D change detection and the identification of concrete armor-unit displacements. Results confirm that pole-mounted videogrammetry supports rapid, repeatable, low-cost SHM (Structural Health Monitoring) observations, providing defensible detection thresholds and reproducible change-detection limits for engineering interpretation and maintenance support.

How to cite: Martínez Olmedo, V., Bento, A. M., Arza-García, M., and Gonçalves, J. A.: Feasibility of Action Camera-Based Videogrammetry for Multi-Temporal 3D Monitoring of Rubble-Mound Breakwaters, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2250, https://doi.org/10.5194/egusphere-egu26-2250, 2026.

Quick clays are fine-grained, highly sensitive marine deposits that are widespread across formerly glaciated regions, including Norway, Sweden, Finland, and Canada. The low remoulded strength of the quick clays makes them particularly susceptible to extensive retrogressive landslides, which pose serious challenges to society. Erosion is recognized as one of the most important pre-conditioning and triggering factor for quick clay landslide. Therefore, identification of the erosion hotspots is essential for understanding landslide initiation processes and for effective hazard mitigation in quick clay terrains. Machine learning has emerged as an effective tool for erosion hotspot mapping, allowing complex spatial patterns and nonlinear interactions among erosion-controlling factors to be identified from remote sensing–derived data. Recent studies have demonstrated that Deep Neural Networks can be effectively employed to identify erosion-prone zones in quick clay environments when sufficient labelled data are available. This study investigates whether unsupervised machine learning applied to remote sensing–derived data can effectively identify erosion hotspots in quick clay areas. A fully automated, Python-based workflow was developed for erosion hotspot mapping in quick clay areas using remote sensing–derived data. The dataset includes terrain, hydrological, environmental, and anthropogenic parameters relevant to erosion and slope instability. Initially, a total of twenty input parameters were considered. Pearson correlation coefficients were computed to assess inter-feature dependencies, and principal component analysis (PCA) was employed to evaluate feature importance. The unsupervised analysis was performed using multiple clustering techniques to capture different structural characteristics of the data where each cluster represents a distinct level of erosion susceptibility. The results suggest that the proposed unsupervised framework can effectively delineate erosion hotspots in quick clay areas and constitutes an initial step toward the development of early warning systems.
Acknowledgements
This work was supported by the Research Council of Norway through the SAFERCLAY project (Grant No. 352887). Orkun Türe was supported by the Council of Higher Education of Türkiye under the DOSAP scholarship programme and served as a visiting researcher at NGI and NTNU.

How to cite: Türe, O., Tao, R., L’Heureux, J.-S., Oguz, E. A., and Tyagi, A.: Fully Automated Unsupervised Machine Learning Framework for Mapping Erosion Hotspots in Quick Clay Areas Using Remote Sensing–Derived Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5775, https://doi.org/10.5194/egusphere-egu26-5775, 2026.

The size and mobility of landslides control their impact on both landscapes and communities. Despite their importance to understanding landslide mechanisms and associated hazards, few studies have examined the factors controlling these two characteristics, particularly at a large scale. This is especially the case for deep-seated landslides that occur across diverse geomorphological and lithological settings. Further, most research focuses on recent landslides and thus fail to consider historical processes that could be associated with environmental conditions that differ from the contemporary ones. Here, we investigate the influence of geomorphology and lithology on the size and mobility of old and recent deep-seated landslides in the North Tanganyika-Kivu Rift region in Africa, an under-researched mountainous environment located in the tropics. Based on a comprehensive inventory of ~2500 landslides, we show that mobility increases with size, especially for the old landslides. These old landslides are significantly larger than the recent ones, likely due to potential progressive landslide growth over time and  influenced by the region’s paleoseismic activity. The main controls on both the size and mobility of deep-seated landslides are lithology and, to a lesser extent, fluctuations in Lake Kivu’s level during the Holocene. Landscape rejuvenation by migrating knickpoints associated with rifting also plays a key role in determining landslide size: in rejuvenated landscapes, landslides tend to be larger than those in relict landscapes. The presence of these large landslides favours the development of smaller ones along their margins, reflecting the influence of path dependency on landslide occurrence and size. Our findings underscore the importance of considering the chronology of landslide occurrence and the long-term legacy of landscape evolution in shaping landslide characteristics.

How to cite: Mugaruka Bibentyo, T., Dille, A., Deijns, A., Nzolang, C., Dewaele, S., and Dewitte, O.: Controls on the size and mobility of deep-seated landslides in the North Tanganyika - Kivu Rift region, Africa, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5929, https://doi.org/10.5194/egusphere-egu26-5929, 2026.

Ephemeral mountain streams on the western Andean slopes remain dry most of the year, yet during intense rainfall events they generate short-lived flash floods with exceptionally high sediment transport capacity. This study investigates the hydraulic response of the upper Río Seco micro-basin (Huaycoloro catchment, Peru) under extreme rainfall scenarios, using a hydraulic–geomorphological framework that links surface hydrology with sediment mobility thresholds. Design discharges were estimated through IDF-based rainfall analysis and classical hydrological methods, while sectional hydraulic modelling using the Manning equation provided flow velocities and bed shear stresses along representative channel reaches. Results indicate mean velocities ranging from 2.4 to 3.4 m/s and shear stresses up to 215 Pa. These values exceed the critical shear stress of the coarse gravel bed by more than five times, indicating generalized sediment mobility and strong incision potential in confined steep reaches. Such conditions promote significant sediment supply from the upper basin, increasing the likelihood of downstream channel aggradation and flood hazard in peri-urban sectors of eastern Lima. To our knowledge, this is the first hydraulic–geomorphological quantification of sediment mobility thresholds in an arid Andean micro-basin under design-storm conditions. The findings provide quantitative evidence supporting the need to transition from purely water-based flood models toward sediment-inclusive risk assessments in steep ephemeral mountain catchments.

How to cite: Rosales Torres, L. and Cárdenas-Gaudry, M.: High-energy sediment dynamics in ephemeral Andean mountain streams: The case of Río Seco, Peru, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6006, https://doi.org/10.5194/egusphere-egu26-6006, 2026.

Flood-prone small mountainous catchments hosting critical infrastructure, such as bridges and transport networks, require integrated hydrologic–hydraulic analyses to ensure long-term resilience under changing climatic and land-use conditions. This study develops a coupled HEC-HMS–HEC-RAS modelling framework to quantify design discharges, inundation patterns and local hydraulic controls for the torrential stream crossing the settlement of Kato Nevrokopi in Northern Greece. Using high-resolution topographic data (DEM), GIS-based basin delineation and long-term rainfall records, design storms for multiple return periods are derived and transformed into flood hydrographs at the catchment outlet. These hydrographs force 1D steady-flow simulations in HEC-RAS, explicitly representing bridges, piers and local constrictions that act as morphodynamic bottlenecks and potential failure points under extreme flows. Model results are used to generate flood extent and water-depth maps for events up to the 1,000-year return period, identify critical cross-sections where afflux and backwater effects are most pronounced, and assess the effectiveness of alternative layout and channel-training configurations. The analysis is framed within the current EU Floods Directive 2007/60/EC and Greek legislation for stream delineation, linking quantitative hazard metrics to planning constraints and infrastructure design requirements. The work highlights how relatively simple, openly available tools, when combined with detailed geometric representation of bridges and channel morphology, can support evidence-based decisions on flood protection works, minimise over-engineering, and improve the adaptive management of critical infrastructure in steep, data-scarce basins.

How to cite: Pavlidis, K. and Valyrakis, M.: Hydrologic-hydraulic modelling and flood hazard mapping for infrastructure resilience in a small mountainous catchment on Northern Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7986, https://doi.org/10.5194/egusphere-egu26-7986, 2026.

The construction of mega-canals necessitates a profound understanding of the pre-existing fluvial equilibrium to mitigate adverse geomorphic consequences, particularly in rivers with limited channel capacity. This study focuses on the intrinsic stability mechanisms of the Qin River, a typical small-to-medium-sized mountainous river in South China, prior to the implementation of the Pinglu Canal project. Field surveys and sediment analyses were conducted to characterise the natural bed state, with a focus on a morphologically representative reach. The findings indicate that the riverbed has historically maintained a strong dynamic equilibrium, supported by lateral confinement from riparian vegetation and natural armor processes unique to mountainous fluvial regimes, which are derived from tributary inputs. The analysis reveals that specific hydrodynamic thresholds and sediment connectivity are essential for maintaining this stability. Therefore, rather than hydraulic stress alone, the system's main vulnerability is determined to be the possible disruption of these established equilibrium conditions, particularly with regard to geological substrate constraints and longitudinal continuity. These results establish a scientific standard for assessing the potential disturbance risks of canalization in delicate mountainous river systems by providing a critical morphodynamic baseline.

How to cite: Zhu, S., Sun, J., Liu, C., Chen, L., and Chen, W.: Natural Riverbed Stability in a Small-to-Medium-Sized Mountainous River: A Baseline Investigation of the Qin River Prior to the Pinglu Canal Construction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8868, https://doi.org/10.5194/egusphere-egu26-8868, 2026.

The traditional workflow in palynology begins with the removal of rock minerals through acid digestion and heavy liquid separation, followed by mounting the organic residue on a glass slide, and analysing it under a transmitted light microscope. Using the microscope, palynologists manually identify and assign the observed particles to predefined categories within a designated counting area on each slide. Counting typically continues until a target number of particles has been reached (often between 200 to 300).

Beyond the commonly analysed palynomorphs such as pollen, spores, and dinoflagellate cysts, palynological slides may also contain a diverse range of acid resistant organic sedimentary particles, including freshwater algae, phytoclasts, amorphous organic matter, and many others. Examining the full spectrum of these particles is known as palynofacies analysis. It is one of the most powerful methods for reconstructing depositional environments in sedimentary rocks, as it relies on the distribution and relative abundances of these particles.

However, traditional counting methods for palynological and palynofacies analysis present several limitations. The counting area is rarely defined with precision, making it difficult to reproduce analyses. As a result, if any annotations need to be corrected, the entire counting workflow must be repeated. A particularly challenging aspect is the objective estimation of particles such as amorphous organic matter or phytoclasts, which are always fragmented and do not exist as discrete entities. Moreover, identification accuracy can vary substantially between analysts depending on experience, introducing challenges for reproducibility, comparability, and integration across datasets.

Digitizing palynological slides offers a promising opportunity to reduce subjectivity and personal bias by enabling particle annotation directly on high resolution digital images. This approach also supports iterative analysis, allowing annotations to be updated or refined without repeating the microscopy workflow. Through the ArtPOP project, we aim to develop objective, widely applicable annotation tool that enhance the robustness of paleoenvironmental reconstructions and facilitate integration across diverse palynological datasets. In this presentation, we provide an overview of challenges and advantages associated with digitizing the palynological workflow. We also present our preliminary results of the AI-augmented annotation of selected sedimentary particles.

How to cite: Śliwińska, K. K. and Andrianov, N.: ArtPOP - Automated RecogniTion of Palynomorphs and Organic sedimentary Particles , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10337, https://doi.org/10.5194/egusphere-egu26-10337, 2026.

The Cretaceous–Paleogene (K/Pg) mass extinction represents one of the most severe crises in Earth history, with marked regional variations in the tempo of pre- and post-extinction environmental stress and ecological recovery. The Um Sohryngkew River (USR) section of Meghalaya (NE India) provides a unique perspective on stress and recovery dynamics in a marine setting proximal to the Deccan Traps. This study integrates planktonic foraminiferal assemblage data with sedimentological observations and bulk-carbonate δ¹³C measurements to reconstruct the nature and duration of marine stress and to constrain the timing of ecological and carbon-cycle recovery in the eastern Tethyan realm. This integrated, high-resolution multi-proxy approach was previously lacking for this Deccan-proximal archive, and provides a critical constraint on how volcanogenic forcing modulated K/Pg stress and recovery at regional to global scales.

The late Maastrichtian record at USR indicates highly stressed surface-ocean conditions. Planktonic assemblages are dominated by small opportunistic taxa, particularly Guembelitria cretacea (>80%), with strong dwarfing, dominance of thin-walled morphotypes, poor preservation, and a near absence of heavily calcified taxa (e.g., Pseudotextularia spp., Globotruncana spp.). These assemblage and preservation features point to sustained calcification stress and unfavourable conditions for carbonate production in surface waters, consistent with enhanced nutrient input and surface-water acidification under intensified continental weathering/runoff and volcanogenic CO₂ emissions. Following the K/Pg boundary, planktonic foraminiferal abundance (4 tests/g) and diversity remained markedly suppressed through the early Danian. The post-boundary interval is similarly characterised by persistent dominance of small opportunistic taxa (>30%; e.g., Guembelitria spp. and Chiloguembelina spp.) and continued dwarfing, indicating sustained calcification stress and hindered ecosystem rebuilding. Bulk-carbonate δ¹³C indicates delayed carbon-cycle recovery, beginning only after ~750 kyr at USR compared to ~200–300 kyr at many distal sites. Ecological recovery lagged further, with low diversity and small test sizes persisting for ~2 Myr until biozone P1c, indicating decoupling between carbon-cycle recovery and biological reorganization under continued environmental forcing.

The first robust evidence for ecological improvement appears in planktonic foraminiferal biozone P1c, where assemblages become more diverse and better preserved, test sizes increase, and morphogroup proportions stabilise. These changes suggest improved conditions for calcification, progressive strengthening of the pelagic carbonate system, and a more efficient biological pump. By biozones P1c–P2, community structure indicates that ecological balance was largely restored, and carbonate production increased steadily towards a better-developed carbonate-factory environment. Comparison with global K/Pg records suggests that recovery mechanisms in the USR section broadly mirror global ecological and biogeochemical feedbacks, but their timing is substantially delayed relative to distal sections. Importantly, similar evidence for prolonged stress and delayed recovery has also been documented from the Krishna–Godavari Basin of southern India, supporting a coherent regional pattern in marine environments proximal to the Deccan Traps. Together, these Deccan-proximal records highlight strong spatial heterogeneity in post-K/Pg recovery trajectories, including a delayed return to stable carbon cycling, carbonate production, and ecosystem structure.

How to cite: Patra, S., Punekar, J., Srivastava, P., Rawat, S., Bhadran, A., and Girishbai, D.: Delayed carbon-cycle stabilization and ecological recovery across the K/Pg boundary: evidence from the Um Sohryngkew River section, Meghalaya (India), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10713, https://doi.org/10.5194/egusphere-egu26-10713, 2026.


Incipient sediment motion in turbulent flows remains difficult to characterize and predict because the underlying hydrodynamic forces are highly intermittent and events are sparse in time, even in well-controlled experiments. This study investigates whether temporal deep-learning architectures can detect the onset of particle motion directly from high-frequency velocity time series measured by an instrumented “smart sphere” [1, 2], without explicit force or torque measurements. The workflow includes detrending and cleaning of raw signals, physics-informed signal transforms (e.g. smoothed velocity, acceleration, jerk, and kinematic impulse proxies), segmentation with sliding windows, and supervised training of temporal deep-learning architectures, including recurrent, convolutional, and attention-based models, using class-imbalance mitigation such as focal loss, class weighting, and data augmentation.
Hyperparameter optimization is performed automatically with Optuna, and model performance is assessed using ROC and precision–recall curves, confusion matrices and time-resolved prediction performance. Results show that all tested architectures can learn consistent kinematic signatures preceding incipient motion from single-axis velocity time series, with models incorporating attention mechanisms achieving the highest recall on rare motion-onset events, consistent with their ability to focus on intermittent, high-magnitude kinematic bursts preceding entrainment. These findings demonstrate that deep learning applied to smart-particle sensor data can provide an efficient, non-intrusive tool for particle-scale sediment transport monitoring and real-time–capable event detection. The approach is directly relevant to the session’s focus on particle-scale transport mechanics and data-driven upscaling, and opens avenues for integrating deep-learning-based event detection into multi-scale sediment transport models in geophysical and engineered flows.

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.

How to cite: Mavris, I. and Valyrakis, M.: Rare-event detection of incipient sediment motion from smart-particle time series using deep learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11678, https://doi.org/10.5194/egusphere-egu26-11678, 2026.

Understanding transformations of the climate system in the geological past is essential for predicting and mitigating the effects of global climate change in the next future. The geological record provides a unique archive that documents long-term fluctuations of environmental variables, including seasonality. Seasonality appears to have played a crucial role in extreme climate transitions, highlighting the importance of constraining its variability in the past. Increased seasonality is often associated with colder conditions and the development of ice accumulations, making it a key parameter for understanding and forecasting climate change.

Species of the brachiopod Gigantoproductus are giants within the Palaeozoic sedentary benthos, characterised by exceptional size and thick shells, reaching over 30 cm in width and more than 1 cm in shell thickness. These features make them unparalleled bioarchives for palaeoecological and palaeoclimatic reconstructions, enabling the investigation of long-term changes during key intervals of past climate change.

In this study, specimens of Gigantoproductus semiglobosus from upper Visean (Mississippian, Carboniferous) successions of western Ireland (Aran Islands and the Burren) were subjected to detailed diagenetic screening and subsequently analysed using a sclerochemical approach (δ¹⁸O, δ¹³C). These analyses were used to reconstruct seasonal variability and to provide additional evidence for the timing of Mississippian phases of the Late Palaeozoic Ice Age (LPIA).

Our results show that δ¹⁸O profiles from well-preserved shells record high seasonal variations (Δδ¹⁸O = 0.9 to 1.9 ‰ corresponding to a ΔT = 4 to 11 °C) for palaeoequatorial settings, as also observed in coeval species of Gigantoproductus from the UK (Angiolini et al., 2019). This seasonal variation is much higher than that recorded in comparable shallow water, low latitude environments both nowadays and in the distant past. The pronounced seasonality recorded by several species of Gigantoproductus from western Ireland and the UK at low palaeolatitudes supports the onset of a sustained Gondwanan glaciation in the late Visean. Also, the palaeogeographic distribution of the species of Gigantoproductus and the geochemical composition of their shells indicate that low-latitude Mississippian ocean waters did not experience a temperature decrease at the onset of the Gondwanan glaciation, but rather a marked increase in seasonal variability.

Overall, this study highlights the importance of resolving long-term changes in seasonality, using fossil carbonate shells as palaeoclimatic archives during different intervals of climate change, in both the recent and distant past, to better understand and predict long-term transformations of the climate system.

References

Angiolini et al. (2019). The giants of the phylum Brachiopoda: a matter of diet? Palaeontology, Vol. 62, Part 6, pp. 889–917

How to cite: Crippa, G., Angiolini, L., Azmy, K., Cannaò, E., Doyle, E., Della Porta, G., Murray, J., O’Connell, M., Viaretti, M., and Harper, D. A. T.: Seasonal variability at the onset of the Late Palaeozoic Ice Age: insights from Gigantoproductus shells, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12124, https://doi.org/10.5194/egusphere-egu26-12124, 2026.

Bathymetry plays a critical role in determining the occurrence and stability of landfast sea ice, although its seasonal impact on sub-Arctic ice-covered shelves has yet to be thoroughly quantified and understood. Our study explores the ways in which nearshore bathymetry and coastal topography influence the spatial distribution, seasonal persistence, and variability of landfast sea ice, with an emphasis on shallow embayments of James Bay. Our hypothesis suggests that factors like coastal orientation and bathymetry provide extent and stability to the landfast sea ice in the James Bay region, rather than being exclusively governed by marine and atmospheric factors. Using satellite-derived observations of landfast sea-ice delineations, regional bathymetric datasets, and information on coastal geomorphological configuration, this analysis will quantify statistical relationships among the landfast-ice edge extent and persistence metrics with the bathymetric thresholds and coastal orientations. Initial findings indicate that recurrent landfast ice extents are larger and their persistence is higher when there is a shallow water column, undulating bathymetry with mounds, and/or offshore features. Our observations support the hypothesis that bathymetry plays a crucial role in determining the presence and stability of landfast sea ice. By explicitly correlating bathymetry and geomorphology with landfast ice phenology and stability indicators, our research aims to advance both conceptual and quantitative understandings within coastal ice modelling frameworks and refine projections concerning the response of landfast sea ice to ongoing Arctic amplification and climate change.

How to cite: Banerjee, D., Gupta, K., and Mukhopadhyay, A.: Geomorphological controls on the persistence and extent of Landfast Sea Ice in James Bay Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15851, https://doi.org/10.5194/egusphere-egu26-15851, 2026.

Physical geomorphometry is young way that describe land surface morphology through gravitational energy and mass and energy movement. Unlike statistical and general geomorphometric approaches, physical geomorphometry bridging land surface characteristics and fundamental physical processes allows to interpret geomorphological primitives from genetic point of view. In this study we incorporated latest achievements of physical geomorphometry concept to demonstrate a transition from theoretical aspects to practical applications of the concept.

In the research we applied a set of physical geomorphometric (PG) indices that describes landform development from different points of view. Moreover, we used a modified algorithm of physically based elementary land-surface segmentation algorithm that integrates dynamic least-squares DEM generalization with object-based image analysis. The method is evaluated across contrasting environments, including glacial and karst landscapes, and is further extended to marine settings for seabed landform classification. Key contribution is the application of PG signature concept that unify the set of PG indices and therefore quantitatively describes landforms based on the balance and magnitude of geomorphic energies.

Our results demonstrate that the approach allows us to obtain genetically interpretable landforms both in terrestrial and submarine landscapes. Physical geomorphometric signature is highly effective in landform groups comparison and detection of each group’s potential affinity to development i.e. their disequilibrium. It also helped us to define transitional forms of landforms that are usually overlooked by general geomorphological methods.

Overall, the work highlights robustness and applicability of the concept of physical geomorphometry in various application in geosciences and beyond, that was partially demonstrated in the research.

How to cite: Popov, A. and Minár, J.: Physical geomorphometry: From a concept to practical applications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17175, https://doi.org/10.5194/egusphere-egu26-17175, 2026.

The Tel River, a major tributary of the Mahanadi River in eastern India, exhibits strong spatial and temporal variability in flow and sediment dynamics due to its monsoon-driven hydrology, heterogeneous terrain, and increasing human interventions. Soil erosion and sediment transport, although naturally driven by rainfall and surface runoff, have been significantly altered by agriculture, urbanization, and water management structures, leading to changes in soil loss, sedimentation, and degradation of water resources. Therefore, in this study, the production of soil erosion in the Tel River Basin is estimated using the Revised Universal Soil Loss Equation (RUSLE), while riverine sediment transport is simulated using ANUGA-Sed, a two-dimensional shallow-water hydrodynamic and sediment transport model based on a finite-volume scheme. The ANUGA flow and sediment modules were calibrated and validated using observed discharge and suspended sediment data from multiple gauging stations along the Tel River. Parallel simulations performed on the Param Pravega high-performance computing systems significantly reduced computation time while maintaining numerical accuracy, enabling high-resolution modelling of the entire Tel River Basin. The model was further evaluated for elasticity, computational accuracy, and optimal grid distribution per node on the HPC system, demonstrating robust scalability and efficient utilization of computational resources.

The model results show strong agreement with observations, with errors in net erosion and deposition generally below 10%. The simulations successfully reproduce the spatial patterns of sediment generation, transport, and deposition along the river network. Importantly, the model provides new insights into sediment dynamics between gauging stations where direct measurements are unavailable and captures cross-sectional channel changes associated with sediment transport processes. These results were further validated using field-based suspended sediment data collected in October 2023 at intermediate river locations using portable sampling instruments. The simulations reveal distinct zones of high erosion and deposition that are critical for understanding flood conveyance and channel stability. Overall, the results confirm that ANUGA-Sed can reliably simulate suspended sediment transport and riverbed changes in monsoon-dominated river systems.

How to cite: Dahiwale, A. V., Dutta, U., Singh, Y. K., Yendargaye, G., Prabhu, T. S. M., and Muddu, S.: FROM CATCHMENT TO CHANNEL: HIGH-PERFORMANCE PARALLEL MODELING OF SEDIMENT TRANSPORT IN THE TEL RIVER BASIN USING ANUGA Sed, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19944, https://doi.org/10.5194/egusphere-egu26-19944, 2026.

We conducted a two-month-long cryoseismic monitoring study in the Schirmacher Oasis, East Antarctica, to investigate icequake activity caused by the movement and melting of ice sheets. For this purpose, we deployed a Raspberry Shake seismometer on the Antarctic land and ice sheet for a month. Through a comparative analysis of the recorded seismic data, we gained insights into ice dynamics and diurnal icequake patterns. The Raspberry Shake instrumentation, powered by solar energy, offers a cost-effective approach for establishing a dense seismic network. During installation, the seismometer, solar controller, and Li-ion battery were housed in a wooden box lined with nitrile foam for insulation. The analysis suggests that icequake detections follow a distinct diurnal pattern, with more events occurring during the daytime. Furthermore, we also observe interdependence between icequake detections and high wind speeds.We use a multi STA/LTA approach for event detection on a continuous 11-day period while the seismometer was on ice. We detect 2249 icequake events, which are further manually classified into three categories. More than half of icequakes (67%) belong to a shallow origin and some are indicative of deep icequakes (9%).These findings highlight the need for a denser seismic network and more detailed investigations to further understand the impact of climate change on melting ice sheets.

How to cite: Sattasi, N. S., Silwal, V., Tm, M., Ahamad, A., Suthar, A., and Negi, S. S.: Cryoseismic monitoring in the Schirmacher Oasis, East Antarctica, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19976, https://doi.org/10.5194/egusphere-egu26-19976, 2026.

River deltas play a crucial role in the transport of sediments and nutrients between river catchments and the sea. Scientific studies have demonstrated that Arctic deltas have a significant potential for sediment retention. Ongoing climate change is accelerating the thawing of permafrost, which largely constitutes the substrate of Arctic deltas, thereby affecting the morphological and hydrological evolution of these low-lying tundra systems.

The aim of this study is to estimate changes in the surface area and flood storage capacity of deltaic lakes using remote sensing methods. Optical and radar satellite data from Sentinel-2 and RADARSAT-2 were used, obtained under a grant from the Canadian Space Agency (application no. RCM CSA-RC-FORM-0003), together with advanced tools for spatial and radar data analysis. The selected study area is an eastern part of the Mackenzie River Delta (Canada, Northwest Territories), namely Big Lake, located near the city of Inuvik, approximately 130 km from the Beaufort Sea. The Big Lake is a through-flow lake with an area of about 800 ha. It is part of a system of approximately 2,000 lakes that maintain year-round connectivity with the East Channel, one of the main distributary channels conveying water within the delta.

The presented results are based on satellite and hydrological analyses conducted at the beginning of the ice-free water period, occurring at the turn of May and June. The study includes a comparison of satellite observations with gauge data. To determine the extent and volume of floodwaters, the Normalized Difference Water Index (NDWI), advanced radar data analyses, and statistical analyses of hydrological data from Water Survey of Canada (WSC) were applied. Satellite imagery acquired during open-water seasons made it possible to delineate shoreline extents and the associated water surface elevations. Selected years from the period 2011–2024 were analysed; for example, it was estimated that at the turn of May and June 2024 the lake stored approximately 8.2 million m³ of water over a period of 49 days.

Considering sediment transport, the Mackenzie River is the largest supplier to the Arctic Ocean, delivers more than 100 million tonnes of sediment annually. Previous studies characterise these sediments as predominantly fine-grained fractions that are easily transported. The presence of an organic-rich catchment combined with the magnitude of fluvial sediment transport highlights the importance of understanding the mechanisms governing sediment distribution, quantities, and areas of deposition within the delta system.

This research is being conducted with the permission of the Government of Canada – North West Territories (NWT) – research licence number 17694 which was issued under application number 6131 and financed by the Polish Ministry of Education and Science - National Research Agency, title: Evaluation of the settling velocity and trapping capacity of sediments in lakes in the Great Arctic River deltas, grant no. 2023/50/O/ST10/00597.

How to cite: Ciepłowski, D. and Habel, M.: Remote sensing analysis of water dynamics within floodplain lakes in the eastern part of the Mackenzie River delta, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20785, https://doi.org/10.5194/egusphere-egu26-20785, 2026.

The non-linear feedback mechanisms and interactions between discharge-sediment supply and instream (riparian) vegetation cover generate spatio-temporal heterogeneity in braided channel forms. The present study examines such relationships among three contrasting braided rivers of India: the Brahmaputra (highly braided), the Brahmani (weakly braided) and the Netravathi (meandering-braided). Long term JRC Surface water layer, vegetation-water remote sensing indices, numerical model derived hydrological datasets and periodic field visits have been integrated to understand the vegetation–hydrology–sediment coupling across these braided river systems.  The results show that the channel forming discharges in the Brahmaputra shows a hierarchical level and extreme events dominate over the effect of sparse vegetated landforms. In weakly braided reaches, channel-in-channel form oscillates between two extreme nodes depending upon the intensity of disturbing events. For rivers with meandering-braided transition form, channels are relatively stable and riparian vegetation cover generate a stable geometry and absence of floodplain sediment storage.   

How to cite: Pradhan, C.: Integrating Google Earth Engine Cloud Computing and Fluvial Surveys to Quantify Vegetation–Hydrology–Sediment Coupling in Contrasting Braided River Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21498, https://doi.org/10.5194/egusphere-egu26-21498, 2026.

Paleosols preserve critical evidence of past surface conditions and provide key insights into Earth’s environmental evolution. Pedogenetic processes, controlled by parent material, climate, topography, biological activity, and exposure time, record both the duration and intensity of weathering. Micromorphological features in paleosols are particularly valuable for establishing relationships between soil-forming processes and sedimentary structures, supporting robust paleoenvironmental and paleoclimatic interpretations. Permian paleosols from the Paraná Basin, southern Brazil, occur within the Rio do Rasto Formation, which is composed of lacustrine deposits of the Serrinha Member, overlain by aeolian systems, fluvial channels, and overbank successions of the Morro Pelado Member. This study integrates macro- and micromorphological observations with geochemical data (Chemical Index of Alteration – CIA) and mineralogical analyses (X-ray Diffraction – XRD) to reconstruct paleoclimate conditions during paleosol development. Microscale analyses show that variations in clay mineral assemblages and carbonate precipitates strongly control sample coloration, producing whitish, greenish, and grayish tones proportional to carbonate content. The results indicate a predominantly semiarid to arid paleoclimate, characterized by intense wetting–drying cycles, repeated waterlogging, and high evaporation rates. The clay fraction is dominated by expansive clay minerals, particularly smectite, reflecting reduced chemical leaching under seasonal drainage conditions. In contrast, subordinate kaolinite and illite suggest episodic phases of improved drainage and longer subaerial exposure. Pedogenic features such as desiccation cracks, slickensides, bioturbation structures (root traces and burrows), and redoximorphic mottling provide further evidence for soil development under a highly seasonal water regime. Carbonate nodules and evaporitic phases become increasingly abundant toward the top of the stratigraphic succession, indicating a progressive aridification trend associated with the continentalization of Gondwana during the Middle to Late Permian. CIA values demonstrate a regional climatic gradient within the basin, from semiarid conditions in intermediate areas to fully arid, locally evaporitic settings in more distal zones. These results reinforce the value of paleosols as reliable terrestrial paleoclimate proxies and provide new insights into the paleohydrological and climatic evolution of southern Gondwana during the Late Paleozoic. This study contributes to a better understanding of environmental dynamics prior to the Permo–Triassic transition.

How to cite: Paz, C., Bállico, M., Belitzki, L., Manna, M., and Goldberg, K.: Paleoclimate reconstruction from Permian paleosols of the Rio do Rasto Formation, Paraná Basin, Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1262, https://doi.org/10.5194/egusphere-egu26-1262, 2026.

66 million years ago, an asteroid killed the non-avian dinosaurs. It also triggered the extinction of the ammonoids, an iconic and diverse group of shelled cephalopods. Curiously, a far less diverse group of shelled cephalopods survived, the nautiloids. Why did the nautiloids survive, but the ammonoids go extinct? This question is subject to a lively and ongoing debate. Many (not mutually exclusive) hypotheses have been raised, often with some degree of empirical support. For example, nautiloids had larger hatching sizes, which might have allowed them to survive periods of low food availability. Nautiloids also had larger geographic distributions, possibly indicating greater flexibility in response to varying environmental conditions, or a higher chance to end up in refugia post-impact. Drawing on PaleoDB and other published datasets, we collected the largest dataset so far on Maastrichtian shelled cephalopods, combining fossil occurrences, hatching sizes, and body sizes. We present some preliminary findings based on this data. 

How to cite: Schmutzer, M., Saupe, E., Klug, C., Tajika, A., Wiese, F., and Witts, J.: Why did ammonoids go extinct but nautiloids survive the end-Cretaceous mass extinction?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5239, https://doi.org/10.5194/egusphere-egu26-5239, 2026.

Mutated pteridophyte spores occur abundantly in conjunction with the end-Triassic mass-extinction (ETME), ~201.6 million years ago, one of the ‘Big Five’ mass-extinction events of the past 500 million years. Based on high concentrations of sedimentary mercury (Hg) in beds that contain abundant mutated fern spore fossils, it has been hypothesized that volcanogenic Hg-emission from large-scale volcanism in the Central Atlantic Magmatic Province exerted stress on standing and pioneering vegetation, causing malfunctions in meiosis and the production of malformed pteridophyte spores. Here, we provide the first clear in vivo evidence for anomalously high Hg among the plants that survived and proliferated through the ETME using synchrotron X-ray fluorescence (XRF). Our analysis reveals highly enriched values of Hg within the fronds of the earliest Jurassic fern Phlebopteris angustiloba from southern Germany. Intriguingly, P. angustiloba, a member of the Matoniaceae, is recognized as the parent plant which produced malformed spores within the Deltoidospora-Concavisporites complex that are common in the same beds that contain the fossil fern leaves. Using XRF and X-ray absorption near edge structure (XANES) analyses, we made comparisons between the fossil fern leaves and those of extant ferns growing in high-mercury environments in Slovenia, Slovakia, and the Czech Republic. These comparisons suggest that ferns can tolerate elevated Hg-levels and bind it in their placentas with sulfurous compounds. Our combined analysis of extant and extinct ferns suggests that these traits may have evolved in response to past environments with high concentrations of toxic metals—like those caused by magmatically-triggered mass extinctions—during which metal-tolerant strategies would have greatly enhanced survivorship.

How to cite: van de Schootbrugge, B., Mays, C., Navratil, T., Rohovec, J., Lomax, B., Vogel-Mikus, K., van Konijnenburg-van Cittert, H., Brückner, D., Maas, G., Arkesteijn, M., Lindström, S., and van der Ent, A.: Mercury accumulation and mutagenesis in ferns surviving mass-extinction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5652, https://doi.org/10.5194/egusphere-egu26-5652, 2026.

The Göynük section emerges as a particularly valuable archive, preserving a continuous ~800 kyr stratigraphy from the CF4 to CF1 planktonic foraminiferal zones (~66.8–66.016 Ma), thus capturing the full trajectory of environmental perturbations leading to the KPg boundary. Notably, the progressive rise in planktonic δ¹³C values, peaks in Hg and Te concentrations between ~66.3–66.01 Ma and shifts in both planktonic and benthic δ¹⁸O point to intensified volcanic activity, most likely linked to the Poladpur pulse of the Deccan Traps. These signals—along with enhanced weathering, increased detrital input, and declining magnetic susceptibility—mark a phase of sustained environmental stress well before the Chicxulub impact. The correlation of benthic δ¹³C variability with Te enrichment suggests SO₂-induced ocean acidification and intermittent collapses/reductions of the export production as major ecosystem stress mechanisms during mid-CF2. In the Göynük and Okçular sections, the abrupt extinction of planktonic foraminifera, the sharp negative shift in δ¹³C_bulk, and the suite of impact proxies including trace element enrichments, such as an Ir anomaly at the KPg boundary in Göynük, reflect a robust signal of the Chicxulub event. The juxtaposition of both impact- and volcanism-related markers thus speaks for a compound scenario in which Deccan-driven perturbations fragilized marine ecosystems, while the Chicxulub impact delivered the final blow.

How to cite: Adatte, T., Karabeyoğlu, U., Thibault, N., Joachimski, M., and Regelous, M.: Decoding Late Maastrichtian Events: Volcanism, Ocean Changes, and the Chicxulub Impact in Central Anatolia, Turkey, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7975, https://doi.org/10.5194/egusphere-egu26-7975, 2026.

The response of deep-sea ecosystems to the Cretaceous–Paleogene (K/Pg) mass extinction is crucial for understanding post-impact carbon-cycle disruptions and benthic ecological resilience. Our research presents a new unbiased quantitative record of deep-water agglutinated foraminifera (DWAF) with high resolution, coupled with calcareous nannoplankton and stable carbon and oxygen isotopes from Gubbio (Umbria-Marche Basin, Italy) ranging from 6.4 m below to 6.4 m above the K/Pg boundary clay. The dataset is based on highly standardized sampling intervals and weights, consistent sample preparation, in an attempt to minimize the Signor–Lipps bias, accurate taxonomic treatment and statistical analysis.

DWAF abundance and benthic foraminifera accumulation rates (BFAR) show an abrupt decline and reduction across the boundary, reaching a minimum point in the earliest Danian and followed by a slow recovery over a few hundred thousand years. The case of productivity collapse parallels with a negative excursion in δ¹³C and shifts in δ¹⁸O, suggesting marine carbon cycle disruption. Shannon H and Dominance D diversity indices, supported by diversity curves, display a sharp reduction in species richness and evenness below and above the boundary. The early Paleocene assemblages are described by low diversity, high dominance, and blooms of opportunistic taxa (Reophax, Spiroplectinella). Lazarus taxa were detected higher in the Danian, along with a gradual increase in BFAR and isotopic values.

Benthic foraminifera and isotopic signals point out a temporary reduction in food supply to the deep water, reflecting an unsteady and short-term Strangelove-like response rather than a true Strangelove Ocean as postulated by previous authors. Additionally, the evidence for the survival of benthic foraminifera, the absence of extensive-scale extinction, and the rapid recovery of BFAR and diversity values, does not fully support the Strangelove Ocean scenario. Instead, our unbiased record shows a short-lived decline in marine productivity, followed by a gradual recovery and ecological reorganization. Our results suggest that deep-sea ecological communities at the Cretaceous–Paleogene boundary were able to withstand the disturbance, and experienced a reduced food supply rather than a complete shutdown of biological productivity. 

How to cite: Hikmahtiar, S., Kaminski, M., and Korin, A.: Is There Evidence of A “Strangelove Ocean” After The K/Pg Boundary?  A New Unbiased Benthic Foraminiferal Record, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8888, https://doi.org/10.5194/egusphere-egu26-8888, 2026.

The Cretaceous-Paleogene (~66 Ma) boundary marks one of the ‘Big Five’ mass extinctions of the Phanerozoic. The event continues to spark discussion, and stimulating increasing focus on the study of geological records of that boundary, including the development of robust stratigraphic frameworks and new proxies. Some of the most-studied Cretaceous-Paleogene sections are those near the town of Gubbio, located in the Umbria-Marche Basin in Italy. The construction of cyclostratigraphic age models allows for the refined understanding of the timing and pacing of paleoenvironmental effects of Deccan volcanism and the Chicxulub impact. High-resolution X-ray fluorescence derived elemental profiles allow for detailed stratigraphic correlation and paleoenvironmental interpretations that can be checked across stratigraphically equivalent sections across the basin. New integrated proxy records (e.g. platinum group element and mercury concentrations, osmium isotope ratios) featuring both extraterrestrial impact and large-scale volcanism signatures can now be put on a common timeline to allow the decomposition of its relative contributions. This contribution gives an overview of such progress made for these sections over the last decade of research, and to what new insights it leads.

How to cite: Sinnesael, M., Montanari, A., Percival, L. M. E., Schulz, T., de Winter, N. J., Vellekoop, J., De Vleeschouwer, D., Coccioni, R., Koeberl, C., Goderis, S., and Claeys, P.: The Cretaceous-Paleogene boundary at Gubbio: an overview of recent stratigraphic and proxy record updates , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9703, https://doi.org/10.5194/egusphere-egu26-9703, 2026.

Tellurium is a highly volatile, chalcophile and moderately siderophile trace element that is strongly enriched in volcanic gases relative to crustal rocks. Like mercury, tellurium concentrations in sediments can therefore represent a proxy for past volcanic activity, allowing the timing of LIP volcanism relative to environmental and biotic change during mass extinction events to be determined. Previous studies reported high Te contents in sedimentary rocks at the Permian-Triassic, Cretaceous-Paleogene and Paleocene-Eocene boundaries, which may be linked to eruption of the Siberian, Deccan, and North Atlantic flood basalts, respectively.

Due to the low abundance of Te in most geological materials, and the relatively high ionization energy of Te, this element is rarely analyzed and its geochemical behavior is poorly understood. We have developed methods for analysis of nanogram amounts of Te (and other trace elements) using desolvating nebulizer ICP-MS. Addition of a single-step cationic exchange preconcentration allows analysis of samples containing ppt levels of Te. Using these methods, we carried out analyses of different geological materials, in order to advance our understanding of the behavior of Te in volcanic and sedimentary systems and assess its potential as a proxy for volcanic activity.

Glacial diamictite composites, previously used to estimate the average composition of the Upper Continental Crust (UCC), yield an average Te concentration of 36.7 ± 0.5 ng/g. Assuming this is representative of average UCC, this enrichment in Te relative to estimates of the primitive mantle (silicate Earth) of about 12 ng/g, despite tellurium’s moderately compatible behavior during mantle melting, may indicate that Te has been concentrated in the UCC due to volcanic and hydrothermal processes.

Deccan flood basalts that have not fractionated sulfide, have low Te concentrations (average 0.94 ppb, n=12) relative to MORB (3 – 5 ppb), suggesting that Te was largely degassed during emplacement of the subaerial Deccan lavas at 66.5 – 65.5 Ma. By contrast, the red boles (fossil soil horizons) interbedded with Deccan lavas, have high Te concentrations of up to 2200 ppb, indicating that significant amounts of Te were released during volcanism, some of which was deposited close to the site of volcanism. This observation agrees with data of several thousand sedimentary rocks from profiles across the K-Pg boundary in Italy, Egypt, Morocco, Turkey and Spain, thus supporting the use of Te as a geochemical proxy for LIP volcanism.

How to cite: Regelous, M., Baumann, N. B., Adatte, T., Rudnick, R. L., Schoene, B., Keller, G., Sharma, N., and Haase, K. M.: From Volcanic Source to Sedimentary Sink - Tellurium as a proxy for LIP volcanism, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10613, https://doi.org/10.5194/egusphere-egu26-10613, 2026.

The episodic emplacement of the Central Atlantic Magmatic Province (CAMP) triggered profound perturbations to the global carbon cycle, marked by abrupt pCO₂ elevations and climatic/environmental disturbance that led to the end-Triassic mass extinction (∼201.5 Ma). While volcanogenic degassing is recognized as the primary trigger of this environmental crisis, the subsequent Earth system feedbacks, particularly the role of silicate weathering in sequestering excess carbon, remain poorly understood. Resolving the temporal interplay between pulsed magmatic degassing and the weathering of fresh basaltic rock and associated carbon drawdown, is essential for understanding the stability of the global climate systems during extreme greenhouse forcing as well as the drivers of Early Jurassic Earth system recovery. In this study, we utilize the osmium (Os) isotope proxy to disentangle the intricacies of couplings between the global carbon cycle, magmatism and continental weathering.

Seawater ¹⁸⁷Os/¹⁸⁸Os ratios are highly sensitive to the balance between radiogenic continental runoff and unradiogenic mantle-derived inputs. Given the short residence time of Os (~10–50 kyr), this system can provide a detailed archive of rapid shifts in global weathering fluxes. We present a high-resolution initial seawater Os isotope ratio (¹⁸⁷Os/¹⁸⁸Os_i) record from the Prees Borehole (Cheshire Basin, UK), drilled by the International Continental Drilling Program (ICDP) Early Jurassic Earth System and Timescale (JET) project that offers an exceptionally complete stratigraphic succession across the Triassic–Jurassic transition. Our data, integrated with well constrained carbon-isotopic and biostratigraphic frameworks, reveal stratigraphic fluctuations in sedimentary Os-isotopic compositions that suggest temporal changes in global seawater ¹⁸⁷Os/¹⁸⁸Os_i, and by inference allow tracking of CAMP magmatism and changes in global weathering. By placing these findings in a global context, we demonstrate how the competition between volcanic carbon degassing and new weathering sinks governed the evolution of the global carbon cycle and, consequently, the ocean–atmosphere climatic system, providing a mechanistic framework for the environmental recovery following one of Earth’s most severe biotic crises.

How to cite: Xu, W., Ballabio, G., Hnatyshin, D., Ruhl, M., van Acken, D., Dickson, A. J., and Hesselbo, S. P.: Magmatism and continental weathering linked to carbon cycle change and climatic disturbance across the Triassic–Jurassic transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10627, https://doi.org/10.5194/egusphere-egu26-10627, 2026.

The Frasnian-Famennian Kellwasser Crisis (~372 Ma) is one of the most severe marine biocrises of the Phanerozoic Eon. The ecological impact of the Kellwasser Crisis was global in nature and sedimentary sections that record the Kellwasser Crisis commonly contain two organic-rich layers, the Lower Kellwasser (LKW) and Upper Kellwasser (UKW) horizons. This canonical two-step pattern, however, is far from globally uniform and differences in thickness, completeness and lithology are pronounced among depositional settings. Cyclostratigraphic analyses converge in total crisis duration estimates, while high resolution studies reveal substantial differences in the duration and internal structure of the LKW and UKW depending on depositional environment. These differences challenge the assumption that the Kellwasser horizons are isochronous at fine timescales and highlight the need for high-resolution analyses across multiple depositional environments.

To address these uncertainties, we present a cyclostratigraphic and paleoclimatic analysis of a combined sediment core and hand sample dataset of the siliciclastic Walnut Creek section (western New York State, USA). Walnut Creek exhibits a pronounced meter-scale rhythmicity between thicker grey shales and thinner black shale beds that is suggestive of astronomical forcing.

Cyclostratigraphic reconstruction based on XRF analysis indicates a total crisis duration of ~880 kyr, which is consistent with independent estimates from other localities. However, reconstructed durations of ~25 kyr for the LKW and ~8 kyr for the UKW are notably shorter than observed elsewhere. Throughout the crisis interval, black shale deposition in the Appalachian Basin is indicated to be driven by top-down eutrophication linked to precession-paced variations in monsoon strength. The new geochemical and cyclostratigraphic evidence from Walnut Creek demonstrates that the onset of organic-rich LKW and UKW deposition was likely isochronous in the Appalachian Basin and the deeper Rheic Ocean margin, and that astronomical forcing controlled the pacing of the crisis. Notably, the thick organic-rich crisis beds commonly found in deposits from the Rheic Ocean correspond to several, respectively shorter, precession-paced black shale beds at Walnut Creek.

From these findings we identify three first-order factors that locally determine whether LKW and UKW organic-rich horizons formed, how thick they would become, and how long they persisted: (1) the capacity of the hinterland to generate nutrient-rich soils; (2) the sensitivity of the depositional environment to precessional forcing; and (3) the dissipation timescales of oxygen-depleted water masses. Together, these factors explain the global spatial heterogeneity of the geologic expression of the Kellwasser Crisis.

How to cite: Quabeck, J., Klisiewicz, J., Wichern, N., Bialik, O., Over, J., Hinnov, L., Tuskes, K., and De Vleeschouwer, D.: Short Local Expression, Long Global Crisis: Astronomical Constraints on Devonian Kellwasser Event Durations from Walnut Creek (New York State, USA), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11451, https://doi.org/10.5194/egusphere-egu26-11451, 2026.

The critical timespan during the Rhaetian (Norian to Hettangian), and in particular the Triassic–Jurassic transition, is known for the catastrophic end-Triassic mass extinction event (201.6 Ma). This occurred in the context of the breakup of the supercontinent Pangaea, and was accompanied by strong earthquakes and widespread volcanism.

In Luxembourg, the Rhaetian is exceptionally well preserved as a complete stratigraphic sequence in several drill cores (Elvange, Geyershaff, Grouft, and Heedhaff) and has been studied intensively in detail by the authors. It is subdivided in Luxembourg into a lower part, the Mortinsart Formation (Grès de Mortinsart), and an upper part, the Levallois Formation (Argiles de Levallois). The Mortinsart Formation is built up by alternating greyish-green sand-, and black claystones with rare thin black conglomerates and coaly horizons. They are overlain by the Levallois Formation, a very uniform sequence of reddish-brown claystones with thin silt streaks. Furthermore, the Levallois Formation shows numerous horizons with microfold structures in Luxembourg.

These soft-sediment deformation structures (SSDS) are usually interpreted as seismites because they are earthquake-induced and can be observed in the end-Triassic mass extinction interval across Europe. The origin of these is the intense seismic activity, linked to the formation of the Central Atlantic magmatic province (CAMP) caused by the breakup of Pangea.

The Levallois Formation is separated from the underlying Mortinsart Formation by an extremely chaotic, intensively deformed and completely unsorted horizon, which shows  flame structures, and vertebrate remains are enriched, including dinosaur bones. The regional distribution and geochemical fingerprints indicate that this could be a tsunamite generated by a potential asteroid impact. However, other causes may also have led to the formation of this horizon. Actually, detailed studies are ongoing.

How to cite: Thein, J., Kuhlmann, N., and Colbach, R.: Sediment deformation structures in the Rhaetian of Luxembourg , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11783, https://doi.org/10.5194/egusphere-egu26-11783, 2026.

The end-Permian mass extinction is the most severe ecosystem crisis in the Phanerozoic, profoundly reshaping Earth’s ecosystems on a global scale. How the terrestrial ecosystem was impacted during the crisis remains poorly constrained due to limited fossil records. Especially, there is the lack of a global view of terrestrial ecosystem changes during the mass extinction. Here we combine Earth system simulations with plant fossil records to reconstruct the global distributions of terrestrial biomes across the Permian-Triassic transition. The results show that terrestrial plant extinction initiated in polar regions and gradually extended to lower latitudes. Plants between 50 ºN and 75 ºS were nearly completely extinct, with survival limited to local areas. Concurrently, flora from lower latitudes migrated into polar habitats. Our results provide quantitative global and regional views of terrestrial plant extinction during Earth’s most severe ecosystem collapse, enhancing our understanding of terrestrial biotic responses to extreme environmental change. 

How to cite: Liu, Y., Guo, J., and Hu, Y.: Terrestrial plant extinction during the Permian–Triassic ecosystem crisis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11955, https://doi.org/10.5194/egusphere-egu26-11955, 2026.

The Cretaceous/Paleogene (K/Pg) boundary (~66 Ma), at which the mass extinction induced by the Chicxulub impact occurred, is preceded by the onset of Deccan Traps volcanism. According to high-precision radiometric dating, the emplacement of this large igneous province occurred from ~300 kyr prior to ~400 kyr after the boundary, potentially affecting Earth’s global climate before, during, and after the extinction event. Nonetheless, despite refined studies published over the last decade, uncertainties persist regarding the rates of volcanic eruption and outgassing, and whether volcanism played a role in the main climatic events across this interval.

In this study, we generated new high-resolution mercury (Hg) concentration data from the internationally recognized K-Pg sites of Zumaia and Caravaca (Spain) and Walvis Ridge Site 1267 (South Atlantic). Our goal is to establish reliable stratigraphic correlations and develop robust, independent age models to infer the temporal relationship between Deccan volcanism and the paleoclimatic changes recorded in the sedimentary record. We calculate Hg mass accumulation rates (MARs) to investigate the nature of the observed Hg anomalies over time. Measured Hg values and calculated Hg MARs display considerable variability between sections; in some cases, higher Hg anomalies were recorded well before the main phase of Deccan volcanism began. This finding raises questions about the utility of Hg as a standalone proxy. Consequently, we argue that for Hg to be considered a reliable geochemical marker for tracking Deccan volcanism, anomalies must be temporally consistent across distant localities and align strictly with the known eruptive history. Our results point out that the greater fit for the Hg anomalies between the studied sections occurred between ~230 kyr prior and 50 kyr after the boundary. These high Hg values are temporally compatible with the emplacement of the bigger eruptive pulses, i.e. the oldest eruptive pulse which includes Kalsubai-Lonavala subgroups formations, and the Poladpur and Ambenali formations respectively, while not showing any clear track of the fourth eruptive pulse related to Mahabaleshwar formation.

According to the extensive climatic proxies generated over the past decades, the only recognizable global climatic event beyond the K/Pg boundary during this interval is the Late Maastrichtian Warming Event (LMWE). Our Hg and MARs anomalies suggest that during the LMWE, Deccan volcanism was involved to some extent. However, the LMWE onset can be dated to ~60 kyr prior to the onset of the temporally consistent Hg and MARs anomalies, suggesting that Deccan volcanism was not the sole trigger of the LMWE. The temperature increase of the LMWE appears to track the last long eccentricity maximum of the Maastrichtian, as originally proposed by Gilabert et al. (2022), reinforcing the hypothesis that orbital forcing played a significant role in the development of this hyperthermal event.  Further studies and age refinement of sedimentary proxies are still required for a better understanding of this episode of Earth’s climatic history.

Gilabert, V., Batenburg, S.J., Arenillas, I., Arz, J.A., 2022. Contribution of orbital forcing and Deccan volcanism to global climatic and biotic changes across the KPB at Zumaia, Spain. Geology 50, 21–25. https://doi.org/10.1130/G49214.1

How to cite: Gilabert, V., Batenburg, S. J., Arz, J. A., Regelous, M., Baumann, N., Ferrer, D., Aparicio, I., and Arenillas, I.: High-resolution mercury (Hg) records across the K/Pg boundary: Assessing Deccan volcanism as a global climatic driver, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13529, https://doi.org/10.5194/egusphere-egu26-13529, 2026.

The Late Devonian and the Middle Cretaceous are crucial periods in Earth's history and especially interesting in terms of macroevolutionary changes in marine vertebrates’ faunas at this time. The Late Devonian (Kellwasser and Hangenberg events) and mid-Cretaceous (OAE 2) events are linked to climate-controlled marine and oceanic anoxic events and biotic turnovers. These intervals are distinguished by unexpected losses in top predators represented by very characterised placoderm fishes and fish-shaped marine reptiles that were lost during these catastrophic events, respectively. During the Hangenberg crisis, they totally extincted all top predatory placoderm fishes, with the largest known predators of the time, such as Dunkleosteus. The Cenomanian-Turonian Mass Extinction is the second-order event of marine extinction and is among the best studied of any mass extinctions. This event is clearly connected with submarine volcanic-controlled climatic warming and the development of anoxic conditions in the oceans. However, one of the more important changes at this time is the total extinction of the fish-shaped or dolphin-shaped marine reptiles, ichthyosaurs, which were nektonic, very mobile, and adapted to cruising long distances, and their physiological adaptation to air breathers makes them more tolerant to oxygenation of the water column. Therefore, it remains a mystery why ichthyosaurs became extinct roughly 28 million years before the end-Cretaceous mass extinction. Both placoderms, as well as ichthyosaurs, were long-lived predators occupying the highest trophic level. Therefore, they could be more sensitive and exposed to toxic metals (such as mercury) bioaccumulation and their biomagnification in the trophic pyramid. Extensive volcanic activity during these periods should deliver huge amounts of highly toxic Hg to aquatic environments. However, the organic form of Hg with one methyl group called methylmercury (MeHg) is more toxic and dangerous to living organisms because it is almost entirely absorbed by the body and flows into the blood, and methylmercury (besides dimethylmercury) is the most toxic form of Hg. The end-Devonian and OAE 2 were characterised by the expansion of anoxic zones in marine environments. In aquatic settings, the main source of methylmercury is biomethylation of Hg by anaerobic microorganisms, such as sulfate-reducing bacteria (SRB). Consequently, the conditions during these periods might have been conducive to the biomethylation of Hg. Methylmercury has received global attention since the poisoning of thousands of people in southern Japan (Minamata) in the mid-1950s. Our aim is to address the lack of knowledge surrounding the occurrence and impact of MeHg on past ecosystems, especially in the context of macroevolutionary drastic changes in aquatic vertebrates during total extinctions, such as the placoderm at the end-Devonian and the ichthyosaurs at the end-Cenomanian. Until now, we have found MeHg in sediments representing the Kellwasser event (Germany, Thuringia) and the Hangenberg event (Poland, Uzbekistan, Austria, and Oklahoma). While in the Cretaceous, we found large mercury spikes (> 1500 ppb) in the Apennines (Italy), which are promising for the search for methylmercury. We collected more samples from these crucial intervals, which are being analysed. 

This project was financially supported by the grant of the National Science Centre in Poland (2023/49/B/ST10/00505).

How to cite: Rakocinski, M., Marynowski, L., Palarz, M., Książak, D., Dubicka, Z., Kucharczyk, J., Staneczek, D., and Krawczyński, W.: The role of mercury biomethylation during end-Devonian and OAE 2 (Cretaceous) biotic perturbations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14681, https://doi.org/10.5194/egusphere-egu26-14681, 2026.

The Mississippian constituted a time of important global changes in marine environments. The mid-Tournaisian Event, also called the Lower Alum Shale Event (LASE), was a global anoxic event that occurred ca. 355 Ma ago. This event is related to global transgression connected with increased productivity, sedimentary starvation, collapsed carbonate production, and drastic facies changes from pelagic carbonate sedimentation to the widespread onset of organic-rich black shales, often with phosphate nodules, followed by black siliceous cherts and lydites in pelagic settings in many parts of the world. In contrast to the younger lower-Mississippian event, the Tournaisian Isotope Carbon Excursion (TICE), the LASE was connected with greenhouse climatic conditions associated with increased volcanic activity. The trigger for the mid-Tournaisian event is still a matter of debate, but intense volcanism (including submarine arc and explosive type) and related climate change seems to be a good causes of these environmental perturbation. The LASE interval was previously investigated in terms of high-resolution inorganic geochemistry and framboidal pyrite analyses in the Carnic Alps (Austria), Montagne Noire (France), Rhenish Massif (Germany) and Holy Cross Mountains (Poland), as well as in terms of organic geochemistry in the last area. Paleoenvironmental and paleooceanographic changes during the LASE event must have influenced the global carbon cycle. However, in contrast to inorganic geochemistry, the data on changes in C_org and C_carb isotope signatures were sparse and of low resolution. The aim of our study was to fill this gap. Positive carbon anomalies were often associated with oceanic water eutrophication, however some of recent studies provide new perspectives for decipher changes in δ¹³C_org record, and several negative isotope anomalies have been reinterpreted as a primary signal associated with large-scale thermogenic degassing of light isotopically carbon (¹²C isotope), due to increased volcanic activity. Our isotopic data reveal negative shifts in the Carnic Alps, Montagne Noire, at the beginning of the LASE interval, reflecting a volcanic impact on the global carbon cycle. The record of stable carbon isotopes presents an extremely similar trend in the isotopic curve in the studied sections (except for France), with a negative shift in the lower part of the LASE horizon, and a positive shift in the upper part. The previous results show that on a regional scale, the LASE in the pelagic setting was not uniform, both in terms of redox changes and intensities of volcanism and styles of magmatism. Several regional magmatic centers are considered as potentially responsible for the drastic depositional changes on a local scale and for the bioproductivity increase on a global scale. Their total contribution led to a maximum of climatic warming after the D-C boundary glacial episode, resultant global transgression, and to the development of anoxia in many parts of the world during the mid-Tournaisian, causing extinctions and faunal turnovers in fossil groups that had just recovered from the global Hangenberg Crisis.

This project was financially supported by the grants of the National Science Centre in Poland no. 2023/49/N/ST10/00857.

How to cite: Kucharczyk, J. and Rakociński, M.: Carbon cycle perturbation and paleoenvironmental changes during the Lower Alum Shale Event (mid-Tournaisian, Mississippian) in southern Euramerican shelf and Palaeotethys Ocean  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16352, https://doi.org/10.5194/egusphere-egu26-16352, 2026.

The Late Triassic Carnian Pluvial Episode (CPE, ~232 Ma) is characterized by significant changes in climate globally, with conditions shifting from arid to humid and wet, followed by a return to arid conditions. The climatic shift, recorded in multiple stratigraphic sections worldwide, is thought to have been driven by a perturbation of the global carbon cycle, associated with the emplacement of the Wrangellian Terrain Large Igneous Province (WT-LIP, ~231-225 Ma). The event is often linked to profound environmental and biotic change, including the rise and diversification of dinosaurs and the establishment of modern ecosystems. Here we present new high-resolution geochemical and sedimentological data from two Carnian successions from Laurasia: the Knocksoghey Formation of the Mercia Mudstone Group in the Carnduff-2 core, Northern Ireland, representing playa-lake and aeolian deposits, and the De Geerdalen Formation, Kapp Toscana Group in the DH-4 core, Longyearbyen, representing deltaic to shallow-marine settings. Together, these sites provide complementary mid- and high-latitude records of environmental change across the Carnian Pluvial Episode (CPE). We integrate carbon isotopes, elemental compositions, weathering indices, clay mineralogy, and Hg/TOC variations to assess the temporal link between the emplacement of the WT-LIP and the onset of the CPE. In the Knocksoghey Formation, the abrupt emplacement of coarser siliciclastic deposits, known as ‘Skerries’, disrupts otherwise monotonous fine-grained red paleosols, interpreted as evidence of enhanced weathering due to the CPE. These deposits are preceded by elevated Hg concentrations, a negative carbon isotope excursion of ~6‰, and concurrent increases in geochemical weathering proxies. Comparisons of Hg/TOC and δ¹³C data from our records with other localities show a marked increase in the Hg/TOC concurrently with the onset of a stepped negative carbon isotope excursion, similar to other well-characterized LIP-driven climate perturbations (e.g., Toarcian CIE), further supporting the WT-LIP volcanism as the driving mechanism of the CPE.

How to cite: Mohamed Shahid, M., Al Suwaidi, A., Ossa Ossa, F., Ruhl, M., Senger, K., Raine, R., and He, T.: Multiproxy Geochemical Records of the Carnian Pluvial Episode in Laurasia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16830, https://doi.org/10.5194/egusphere-egu26-16830, 2026.

The Triassic–Jurassic boundary (TJB) is globally marked by profound environmental change, including disruption of the carbon cycle, global warming, reorganization of sea level, and substantial turnover in marine and terrestrial ecosystems. A characteristic stratigraphic signal of this interval is a negative carbon isotope excursion (NCIE), which is widely correlated and commonly linked to volcanism associated with the Central Atlantic Magmatic Province (CAMP). However, in shallow epicontinental basins, the magnitude and continuity of this signal can be strongly influenced by depositional setting, complicating the distinction between global environmental forcing and local sedimentary overprints. To assess how nearshore environments modulate TJB proxy records, we examine three stratigraphically correlated Upper Triassic–Lower Jurassic nearshore successions spanning a proximal–distal transect across the northeastern Central European Epicontinental Sea (CEES; North German Basin). These archives comprise the delta-influenced Barth 10/65 core (proximal), the shallow-marine Schandelah core (intermediate), and the outer shallow-shelf Moseberg outcrop (distal). We integrate TOC and Rock-Eval data, δ^¹³C_org values, and major and trace element geochemistry to reconstruct carbon-cycle perturbations and depositional and redox conditions across the boundary.

All three successions record a NCIE that starts in the latest Rhaetian and reaches minimum values near the Triassic–Jurassic transition. This excursion coincides with a regressive–transgressive reversal and culminates in the earliest Hettangian flooding, linking the North German Basin records to the global end-Triassic carbon-cycle perturbation. Nevertheless, the expression of the NCIE varies systematically along the proximal–distal transect. The Barth 10/65 core exhibits strong siliciclastic dilution, dominantly oxidized Type III–IV kerogen, and a comparatively muted the NCIE (δ^¹³C_org ~3.6‰), consistent with high-energy deltaic settings and limited accommodation space. In contrast, the Schandelah and Moseberg sections preserve more pronounced excursions of approximately 5‰ in δ^¹³C_org. At Schandelah, the maximum isotope shift occurs during early transgression, whereas Moseberg retains a clearly developed NCIE despite minor stratigraphic truncation across the boundary interval. Moseberg is further distinguished by higher proportions of hydrogen-rich organic matter and enhanced organic-matter preservation associated with short-lived dysoxic conditions. Enrichment factors of redox-sensitive trace elements (Mo, U, Cu, V) indicate predominantly oxic to weakly suboxic conditions at all sites, ruling out sustained anoxia. Collectively, these results demonstrate that depositional position and sea-level–controlled accommodation exert a strong influence on the apparent magnitude and completeness of TJB carbon-cycle signals in nearshore epicontinental settings, underscoring the importance of paleoenvironmental context when comparing boundary records.

How to cite: Mazaheri-Johari, M., Ruebsam, W., Franz, M., Wiesenberg, G., Kaboth-Bahr, S., and Schwark, L.: Spatial Variability in Triassic–Jurassic Boundary Proxy Records Across Nearshore Settings in the Northeast German Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18766, https://doi.org/10.5194/egusphere-egu26-18766, 2026.

The Bonarelli event (OAE 2; ~94 Ma) is the second-order extinction event with ~ 26% of marine genera loss, starting from single-celled foraminifera, numerous marine invertebrates, and ending with marine reptiles top predators - ichthyosaurs. Increased submarine volcanic activity is believed to have been the main cause for global climate warming and palaeoceanographic change. Many magmatic centres were active during this period, such as the Caribbean-Columbian Large Igneous Province (LIP), the High Arctic LIP, the Madagascar LIP, the Kerguelen LIP and the Ontong-Java LIP. The close age correspondence between LIPs and biotic overturn suggests that large-scale volcanism could be the main driver of mass extinction. The aim of our research was classic outcrop of the Bonarelli level lying in the Bottaccione Gorge, near Gubbio (Apennines, Italy). To deciphering redox changes at Umbria-Marche basin the U/Th and V/Cr ratios as well as concentration of redox sensitive elements were used (e.g. Mo, U, V, Ni, Cu, Pb, Zn, Se). The values of U/Th ratios in the Bonarelli level (OAE 2) varying from 0.42 to 4.23, while the V/Cr range from 0,59 to 12.48, which is indicative for variable redox conditions ranging from oxic to anoxic-euxinic conditions. More restricted redox conditions in the OAE 2 interval are confirm by enrichments in U (avg. U_(EF) = 19.92, Mo (avg. Mo_(EF) = 568.45) V (avg. V_(EF) = 22.26), Ni (avg. Ni_(EF) = 21.04), Zn (avg. Zn_(EF) = 53,44) and Cu (avg. Cu_(EF) = 47,21. While in the sedimentary background (Scaglia Bianca) values of redox-sensitive trace elements are low e.g. Mo ranging from 0.04to 0.82 ppm, V ranging from 1 to 5 ppb and U often below detection limit (< 0.1 ppm). Volcanic eruptions and submarine hydrothermal activity are the main natural sources of mercury in recent and ancient environments, and are reflected by Hg spikes in sedimentary rocks. We found huge Hg spikes (maximum values >1500 ppb) in the OAE 2 interval with 5 ppb values of sedimentary background of Scaglia Bianca in the classical Bottaccione Gorge. Recently, Hg anomalies were found in the Mentelle Basin, which suggests a regional influence of the Kerguelen LIP located in the Southern Hemisphere. However, our findings of Hg spikes in the Tethys area indicate that the volcanic scenario may be more complex and that the event may be associated with the activity of several, rather than a single, magmatic province. These results are a starting point for research on potential bacterial biomethylation during OAE 2 and the influence of toxic methylmercury on aquatic life, especially top predatory marine reptiles.

 This project was financially supported by the grant of the National Science Centre in Poland (2023/49/B/ST10/00505).

How to cite: Palarz, M. and Rakociński, M.: The record of the redox changes and submarine volcanic activity during the OAE 2 event (Cenomanian-Turonian boundary) in the Gubbio area (Apennines, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19425, https://doi.org/10.5194/egusphere-egu26-19425, 2026.

The Late Paleocene-Early Eocene is well known as a time interval of greenhouse conditions. Superimposed on these conditions is a series of transient global warming events, including the Paleocene-Eocene Thermal Maximum (PETM at ~56 Ma), the Eocene Thermal Maximum 2 (ETM2 at ~54 Ma), and ETM3 at ~52.8 Ma, alongside other smaller-scale events. These events, collectively known as hyperthermals, were caused by the release of massive amounts of isotopically light carbon into the exogenic pool - as revealed by negative carbon isotope excursions (CIEs) - leading to global warming and ocean acidification. Hyperthermals were likely triggered by crossing thermodynamic thresholds for carbon release from several potential sources, often in response to orbital forcing, although a volcanic origin for the PETM cannot be excluded. While Late Paleocene-Early Eocene hyperthermals are well documented in both marine and terrestrial sedimentary archives, the recent acquisition of well-resolved records from oceanic cores and land sections has revealed the occurrence of carbon cycle aberrations, potentially representing hyperthermal events also during the early Paleocene. In particular, several events of concomitant shoaling of the lysocline/CCD, as reflected in CaCO3-depleted intervals and negative CIEs, are observed at various sites, including South Atlantic ODP Site 1262, the Bottaccione-Contessa record in Central Italy, the Zumaia section (Spain), and Equatorial Pacific ODP Site 1209. Similar to the Late Paleocene-Early Eocene hyperthermals, these events are associated with maximal astronomical forcing, occurring in correspondence with short- and long-eccentricity maxima. Notably, these events are absent in the Maastrichtian, suggesting that the bolide impact and the major mass extinction marking the Cretaceous/Paleogene boundary may have led to profound changes in the marine carbon cycle and its sensitivity to astronomical forcing.

How to cite: Mari, A., Huber, M., Lourens, L., and Galeotti, S.: Are Early Paleocene hyperthermals a legacy of the Cretaceous/Paleogene mass extinction?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19868, https://doi.org/10.5194/egusphere-egu26-19868, 2026.

The Cambrian Period (~539 to 487 Ma) was a pivotal time for biotic innovation. Extinction events played an important role in shaping evolutionary patterns throughout this interval, yet first order questions remain regarding the extent, severity, and mechanisms behind Cambrian extinctions. To address this we present a new global database of bradoriids, microscopic bivalved arthropods, spanning the Cambrian to early Ordovician, which we analyse in terms of biotic response to environmental change. 

Our analyses reveal that most bradoriid fossils come from well-oxygenated shallow marine facies deposited above storm wave base. Therefore, sea surface temperature, oxygen concentration, and mode of dispersal likely exerted strong controls on distribution of these taxa. A smaller proportion of bradoriid occurrences are from deeper water oxic and dysoxic facies, with the relative proportions of deep water oxic and dysoxic varying throughout the Cambrian. The occurrences of some bradoriid fossils in dysoxic facies suggests that these were either benthic taxa, more resilient to marginal oxygen conditions, or pelagic taxa, that lived in overlying better-oxygenated waters.

From Cambrian Age 3 (~521 to ~514.5 Ma) to Age 4 (~514.5 to 506.5 Ma) there was a poleward shift in bradoriid occurrences, away from equatorial latitudes, coupled with a sharp decrease in the proportion of dysoxic deeper water occurrences and increase in well-oxygenated shallow water occurrences. From Cambrian Age 4 to the Wuliuan Age (~506.5 to 504.5 Ma) there was a further decrease in the proportion of low latitude occurrences but an increase in dysoxic deeper water occurrences, returning to proportions similar to Age 3.

Hyperthermal events have been proposed as the driver for the early Age 4 Sinsk extinction and terminal Age 4 extinction of redlichiid and olenellid trilobites. The apparent stepwise poleward shifts in bradoriid occurrences are consistent with hyperthermal temperature rise exceeding thermal tolerance limits in lower latitudes. From Age 3 to Age 4, the decrease in occurrences from deeper dysoxic facies and proportional increase in shallow oxygenated water facies occurrences is consistent with shoaling of anoxic waters forcing benthic taxa, perhaps already close to their minimum oxygen tolerance, to migrate to shallower waters or perish. Shoaling of dysoxic waters is well evidenced as a kill mechanism during the Sinsk event on the Siberian Platform. Coming out of Age 4 into the Wuliuan, the increased proportion of occurrences in deeper waters suggests that these settings may have become more tolerable again, with a lower risk of exposure to lethally low oxygen concentrations. The similar proportional depth distributions of Age 3 and the Wuliuan contrasts with the distribution observed in intervening Age 4, an interval with known extinction events. The combination of palaeolatitude, depth, and seafloor oxygen concentration influence on bradoriid occurrences suggest that Cambrian Age 4 may have been an interval of profound biotic crisis caused by multiple hyperthermal events.

How to cite: Yanagihara, A., Vandyk, T., Wong-Hearing, T., Harvey, T., Jones, C., Zammit, A., and Williams, M.: Tracking Cambrian environmental perturbation using a new bradoriid arthropod database, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21297, https://doi.org/10.5194/egusphere-egu26-21297, 2026.

The landscape evolution of forearc ranges along accretionary convergent margins, such as the southern Chilean Coastal Cordillera, is strongly influenced by deep-seated accretion dynamics, enhancing reactivation of inherited upper-plate structures. The Nahuelbuta Range is the fastest uplifting and exhuming sector of the southern Chilean subduction margin. Stratigraphic markers and uplifted marine terraces indicate dome-shaped uplift across a ~100-km-wide zone since ~2 Ma. However, uplift mechanisms remain debated, and rates are resolved only for the last ~0.3 Myr. Furthermore, dense vegetation and weathering have hindered fault mapping, limiting the understanding of the Nahuelbuta Range deformational history.

We combined new surface geomorphic mapping, morphometric drainage analysis, and river inversion modeling to explore the tectonic and climatic influences on the Nahuelbuta Range landscape evolution. We identify a regional low-relief relic surface atop the Nahuelbuta Range, now warped and dissected by fluvial incision and faults. Drainage morphometric anomalies and microseismicity align with WSW- and ENE-trending faults, indicating ongoing trench-parallel shortening. River inversion analysis shows uplift and topographic rejuvenation between 3 and 2.5 Ma approximately, followed by two later discrete uplift episodes. Uplift transients correlate with Late Pliocene to Pleistocene Patagonian glacial expansion periods, suggesting that glacially intensified sediment flux to the trench enhanced basal accretion of sedimentary material. The location and wavelength of surface uplift events match depth and scale expected for slices of basal acreeted material. Seismic imaging of the sediment-rich subduction channel and microseismicity patterns supports this interpretation. We propose glacially driven tectonic underplating drives the oscillatory uplift history of the Nahuelbuta Range, while ongoing trench-parallel shortening enhance trench-parallel shortening and fault reactivation.

How to cite: Vega-Ruiz, A., Delgado, V., Racano, S., Clementucci, R., Véliz-Borel, V., Espinoza, M., Encinas, A., Melnick, D., Asenjo, C., Zambrano, P., and Larregla, R.: Tectono-Climatic Controls on Uplift Transients of the Nahuelbuta Forearc Range, Northern Patagonian Andes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-373, https://doi.org/10.5194/egusphere-egu26-373, 2026.

The mechanisms of stress transfer across continental plate interiors during continent-continent collision, as well as the timing and the style of far-field fault system responses, remain poorly constrained. The collision between the Indian subcontinent and what is now Tibet began in the Eocene and has involved still on-going north-south convergence throughout southern Tibet and the Himalayas, providing an exceptional natural laboratory for studying continental collision processes.

The Altyn Tagh Fault (ATF), a >1600-km-long lithospheric-scale strike-slip fault marking the northern boundary of the Tibetan Plateau, is a key structure for investigating how deformation propagated following the India-Asia collision. However, the timing of its (sinistral?) initiation remains uncertain, with proposed ages ranging from the Mesozoic to the Miocene. These uncertainties largely reflect the involved structural complexities and the difficulty of directly dating the fault's protracted brittle activity. To address this long-standing problem and to better understand the ATF’s evolution and its role in the Plateau build-up, we conducted detailed structural investigations of two significant outcrops in the Old Aksay region (Gansu province). These exposures preserve a complex fault internal architecture containing numerous Brittle Structural Facies (BSFs), that is, distinct rock domains defined by characteristic fault rocks, mineralogy, textures, and kinematics. Repeated faulting at those outcrops localized deformation into weaker zones, creating thick foliated gouge layers, and along discrete slip surfaces, while lithons from earlier slip events were locally preserved. Their juxtaposition records the temporal and spatial evolution of the ATF, including its deformation mechanisms, physical conditions during initial faulting and subsequent reactivations. We combined multiscalar structural analysis with multi-grain-size K-Ar dating of synkinematic illite separated from BSFs at both outcrops.

The results reveal a protracted, episodic faulting history from the Early Cretaceous (~115 Ma) to the Quaternary (~0.6 Ma), documenting at least five reactivation events. The earliest record at ~115 Ma suggests the ATF existed from before collision as a lithospheric weakness inherited from Mesozoic intracontinental deformation. Crucially, we identify an Early Eocene event (~56 Ma) that provides the first direct geochronological evidence for brittle deformation nearly synchronous with the initial India-Asia collision farther south, supporting models of rapid stress transfer to the northernmost plateau margin. A Late Oligocene reactivation at ~26 Ma coincides with rapid, widespread Miocene exhumation and sedimentation across northeastern Tibet. Late Pliocene (~3 Ma) and Middle Pleistocene (~0.6 Ma) events record continuing slip and deformation localization during progressive Plateau expansion.

This intricate >100 Myr archive demonstrates that long-lived lithospheric weaknesses can preserve deformation spanning multiple tectonic regimes. Beyond providing a robust temporal framework for the tectonic evolution of the northern Tibetan Plateau, our results highlight the efficiency of far-field stress transfer through rigid lithosphere even over very large distances, and establish a powerful methodological protocol for integrating geochronological records and structural investigations in intracontinental orogens worldwide.

How to cite: Sun, Z., Viola, G., Liu-Zeng, J., Zheng, Y., Del Sole, L., Shao, Y., Wang, W., Cui, F., and Shen, X.: Lithospheric weakness and episodic reactivation of the Altyn Tagh Fault since the Early Cretaceous: Insights into stress transfer and Tibetan Plateau growth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1155, https://doi.org/10.5194/egusphere-egu26-1155, 2026.

The life cycle of orogenic belts is governed by the competition between compressional tectonic forces that build topography and gravitational forces that destroy it through extension. In mature orogens, extension is commonly thought to involve viscous flow within a weak crustal channel (WCC), driven by topographic gradients between mountain belts and their margins. This process is expressed in the upper crust as normal faulting atop high mountain belts, such as the Tibetan Plateau and the Apennines. However, the mechanical link by which flow within the WCC drives extension in the brittle upper crust remains poorly understood. In previous work (Dawood et al., 2025 EGU), we designed an analytical model predicting the instantaneous, characteristic rate of brittle extension enabled by WCC flow. Here, we extend and test this framework by coupling it with two-dimensional numerical simulations to investigate the time-dependent dynamics of orogenic collapse. While the analytical model captures the static force balance and provides a snapshot estimate of extension rates for a given orogenic state, the numerical approach resolves the temporal evolution of topography, crustal-channel flow, and fault activity. Our simulations show that topographic gradients drive viscous flow within the WCC, which generates basal shear tractions that promote extension along upper-crustal normal faults. We find that sustained orogenic extension requires both a sufficiently weak WCC (η_wcc  ≤ 10²¹ Pa.s) and an orogenic elevation exceeding a critical threshold height, h_min. This threshold is controlled by the frictional strength of the brittle crust and the magnitude of basal shear stress transmitted from the WCC. Extension rates scale systematically with fault strength, orogenic height, and WCC viscosity and thickness: high extension rates occur for weak faults and high topography (h >>h_min), especially in the presence of a thick, low-viscosity WCC. In contrast, stronger faults, lower elevations, or thinner and more viscous channels suppress extension. Together, these results validate our analytical scaling laws, indicating that while a static force-balance description predicts the instantaneous extensional behavior, numerical models capture the longer-term, time-dependent, self-limiting evolution of collapsing orogens.

How to cite: Dawood, R., Olive, J.-A., and Aharonov, E.: Dynamics of Orogenic Collapse Controlled by Coupled Brittle–Ductile Deformation , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3563, https://doi.org/10.5194/egusphere-egu26-3563, 2026.

The Carpathian Bend Zone is an orocline in the Southeastern Carpathians that links different segments of the Carpathian arc and represents a structurally unique sector of the mountain range. The region experienced Cretaceous to Miocene thick- and thin-skinned nappe stacking as well as post-collisional shortening and out-of-sequence thrusting. Unlike in many other places, these nappe stacks were not overprinted by subsequent back arc extension. In addition to this tectonic inheritance, the bend zone hosts the most seismically active region in Europe, characterized by persistent deep seismicity referred as “seismic nest”. This reflects deep-seated processes that are only partially expressed in the upper crust and are partially manifested through surface uplift and landscape reorganization rather than upper crust faulting.

 These factors lead to preserved nappe stacks and ongoing landscape evolution driven by recent uplift. Previous studies aiming to quantify exhumation and uplift rates have so far been limited to regions north and south of the Bend Zone, leaving this key segment poorly constrained. This study aims at closing this knowledge gap by investigating if long-term and short-term uplift rates are comparable. Furthermore, it collates these data with preexisting rates from other segments along the orogen to reveal local differences in exhumation patterns.

To investigate long-term exhumation, six sandstone samples were analyzed using apatite (U-Th)/He thermochronology. Additionally, geomorphometric analyses such as river longitudinal profiles, knickpoints, and χ-maps were used to study topographic evidence of recent uplift and assess drainage divide migration and equilibrium conditions. Furthermore, river terraces were mapped and their relative elevations above the modern riverbed were used to estimate since the Early Pleistocene. By correlating terrace elevations with known dated levels from nearby regions, constraints were placed on the timing of Quaternary incision and rock uplift.

The Apatite (U-Th)/He dates show a variable amount of thermal overprint. Two samples yield (U-Th)/He dates younger than their stratigraphic ages while four samples show dispersed dates older as well as younger than the corresponding Miocene stratigraphic ages. This indicates partial resetting, an inherited thermal history from the grains’ sources, and limited post-Miocene burial. Therefore, assuming a geothermal gradient of 30 °C/km, a maximum amount of approximately 2.7 km of burial since the Middle Miocene can be presumed. The geomorphic signals consistently indicate active uplift within the Bend Zone, particularly in areas where structural controls induce sharp knickpoints and asymmetry in watershed geometry. The average rock uplift rate indicated by river terraces is 1.1 mm/yr since the Middle Pleistocene. In combination with estimated exhumation rates derived from the thermochronological data, a overall stable landscape surface within the Bend Zone is proposed for the last 2.5 Ma. Overall, our results indicate that the Bend Zone has been characterized by low long-term exhumation rates since the mid Miocene and higher uplift rates during the Quaternary.

How to cite: Schönleber, L., Otto, J.-C., Pollhammer, T., Friedrichs, B., Heberer, B., Dremel, F., Villamizar-Escalante, N., and von Hagke, C.: Long- and Short-term Landscape Evolution of the Carpathian Bend Zone – Linking Low-Temperature Thermochronology with Geomorphometric Analyses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3918, https://doi.org/10.5194/egusphere-egu26-3918, 2026.

When aseismic ridges carried by the subducting oceanic plate enter a subduction zone, the trench depth and hence the margin relief is reduced, which increases the compression of the upper plate. The increase in compression may be relevant for understanding surface uplift and mountain building in response to ridge-subduction, but detailed effects remain to be explored. Here we use analytical and two-dimensional finite-element force-balance models to investigate the effects of relief changes and other parameters that may change during ridge subduction, including the initial trench depth, the megathrust dip angle, the slab curvature, the submarine surface slope angle, the density structure of the upper plate, the initial mountain height and the surface topography of the upper plate.

Our modeling results indicate that the increase in upper-plate compression mainly depends on the total relief change, the trench depth prior to ridge subduction and the submarine surface slope angle during ridge subduction. Secondarily, the increase in compression also depends on the average dip angle and curvature of the plate interface, as well as on the density structure of the upper plate and the mountain height prior to subduction. The enhanced upper-plate compression due to ridge subduction promotes mountain building in the upper plate until the increase in elevation leads to stress conditions comparable to those before the entrance of the ridge. We investigate this aspect for the subduction of the Cocos Ridge, based on additional finite element models that approximate the setting along the Central American margin near Costa Rica before and after the entrance of the ridge. The models indicate that the mere decrease in trench depth of ~3.3 km due to ridge subduction promoted an increase in mountain height of ~0.6 km. This corresponds to one-third of the maximum uplift inferred for Costa Rica. We further find that the remaining elevation increase of up to 1.4 km cannot be explained by changes in the slab dip angle or upper-plate density structure but may indicate an increase in shear stress along the plate interface. Taken together, our analysis shows that the decrease in trench depth during ridge subduction increases the compression of the upper plate, which promotes surface uplift and mountain building even at greater distances to the ridge.

How to cite: Leng, Y., Dielforder, A., and Hampel, A.: Impact of decreasing trench depth during aseismic ridge subduction on the forearc stress state: Insights from analytical and finite-element force-balance models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5077, https://doi.org/10.5194/egusphere-egu26-5077, 2026.

The structural and tectonic interactions between the S-verging Southern Alps and the NE-verging Northern Apennines fold-and-thrust belt, and their shared Po Plain foreland basin, represents a classic and long-debated issue in Alpine–Apennine geodynamics. We here investigate a cross section from the Bobbio Tectonic Window (BTW) in the Emilian Northern Apennines, to the central Po Plain subsurface, which records these important relationships. Previous studies focused on fault slip-rate measurements of the buried Northern Apennine thrust fronts, but a comprehensive tectono-thermal study of the Lower Miocene turbiditic sequence outcropping in the BTW is still lacking. In this work, we investigate the relationship between BTW development and the interaction of the Northern Apennines and Southern Alps thrust fronts buried below Pliocene-Pleistocene sediments in the central Po Plain. We analysed the cooling/exhumation history of rocks exposed at the core of the BTW by means of low-T thermochronology (apatite fission-track and U-Th/He) on samples from the Lower Miocene (Burdigalian) Bobbio Fm. and compared them with the slip-rate history of the Northern Apennines buried thrust front along the Emilian Arc. Our thermochronological results from the BTW show a maximum temperature of ca. 85-90°C (apatite fission-tracks partial annealing zone) reached soon after depositional age, followed first by a relatively slow cooling in the Early Miocene- Early Pliocene time window (17-6 Ma), and then by a fast cooling starting between ca. 6 and 4 Ma.  By comparing these results with the slip-rate trend of the buried Apennines thrust front, we interpret them as the signal of an out-of-sequence thrusting reactivation within the inner Northern Apennine fold-and-thrust belt due to the interaction between the Northern Apennines outermost fronts and the Southern Alps.  This study shows how far-field geological structures can influence the general kinematics of the thrust-fold belt, promoting out-of-sequence reactivation of internal tectonic structures and the exposure of deep tectonic units within the BTW.

How to cite: Stendardi, F., Barrera Acosta, D., Carrapa, B., Toscani, G., Albino, I., and Di Giulio, A.: Tectono-thermal evolution of the Northern Apennines-Alpine knot: a case study from the Bobbio Tectonic Window, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5387, https://doi.org/10.5194/egusphere-egu26-5387, 2026.

The shallowing of subducting slabs within the upper ~200 km of the mantle, commonly referred to as flat slab subduction is associated with extensive petrological and structural modification of the continental lithosphere. Anomalously buoyant oceanic lithosphere, upper-plate overthrusting, and interactions with cratonic keels have all been proposed as mechanisms promoting shallow slab geometries, yet the dynamics governing the initiation and duration of flat slab subduction remain to be fully understood. Here, we investigate self-consistent flat-slab subduction dynamics using the finite element code ASPECT with adaptive mesh refinement and a free surface boundary condition. We explore the influence of the overriding plate structure, including the presence of continental keels, as well as the role of heterogenous subduction interface strength on shallow slab dynamics. Our results show that flat slab geometries develop when a weak, sediment-rich subduction interface is combined with a positively buoyant overriding continental lithosphere. Substantiating previous studies, we further find that the presence of a strong cratonic keel near the continental plate margin enhances shallow slab underthrusting and encourages flat slab configurations. Importantly, we show that the timing of interface weakening, such as due to influx of sediments, exerts a first-order control on the onset and the longevity of slab flattening. As the slab flattens, pronounced subsidence, extension and transient marine inundation develop within the foreland region of the upper plate, superimposed on broader, large-scale subsidence of the continental interior. Regional uplift and subsidence are thus not solely linked to flat slab emplacement and removal, but also reflect evolving slab dynamics within the shallow upper mantle. Our results provide new constraints on the geodynamic controls of flat slab evolution and their role in driving continent-scale deformation and sediment redistribution.

How to cite: Grima, A. G. and Becker, T.: How interface weakening and continental structure promote flat slab subduction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5782, https://doi.org/10.5194/egusphere-egu26-5782, 2026.

Abstract: Hinterland mountains serve as the pivotal link that spatially and temporally couples deep lithospheric processes with surface responses in orogenic systems. The Qinling Mountains, situated in the continental interior of East Asia, form a significant natural boundary that separates China into distinct north-south climatic and geographical zones. A key unresolved issue is the origin of the Qinling Mountains-specifically, the timing and mechanisms of their initial uplift and exhumation. The basin-range structure of the East Qinling provides a natural archive for elucidating this problem, as its formation records the onset of mountain building. This study employs multiple thermochronological techniques, including apatite and zircon fission-track and (U-Th)/He analyses of both basin sediments and bedrock samples across basin-bounding faults. Through analyses of lag-time, elevation profiles, and thermal history modeling, the exhumation history of East Qinling is reconstructed. Results elucidate an early-phase cooling event during ~120-100 Ma, with a rate of 5.9-3.4 °C/Ma. Following a prolonged thermal stagnation until ~80 Ma, a renewed phase of accelerated cooling occurred between 80 and 60 Ma, with cooling rates ranging from 5.3 to 1.0 °C/Ma. Integrating these new results with existing geological evidence, we propose that the Qinling Mountains underwent multi-stage uplift and orogenic processes, driven by far-field tectonic stresses associated with the convergence of surrounding plates. The early Cretaceous rapid cooling and exhumation are correlated with intracontinental deformation stage in the eastern China during the Yanshanian period. However, prolonged erosion and planation resulted in low-relief topography in the Qinling Mountains before the late Cretaceous (~80 Ma). During the late Cretaceous-early Cenozoic, under the far-field influence of Pacific Plate subduction, the East Qinling region experienced intense hinterland extension. This process broke up the pre-existing planation surface and formed a series of alternating basins and ranges, signifying the onset of the mountain building in Qinling mountains. Furthermore, the Qinling Mountains exhibit a spatio-temporal pattern of progressive mountain growth from south to north. This study provides a typical case study for understanding the uplift and tectonic evolution of hinterland mountains.

How to cite: Yuxiong, M., Zhao, Y., Xiaohui, S., Jiali, Y., and Dali, J.: Onset of mountain building in the Qinling Mountains: Evidence from bedrock and detrital low-temperature thermochronology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6495, https://doi.org/10.5194/egusphere-egu26-6495, 2026.

How to cite: Hamid, A. A., Heron, P. J., and Johnston, S. T.: Unraveling the tectonic signatures of thin and thick oroclines through a global catalogue, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8121, https://doi.org/10.5194/egusphere-egu26-8121, 2026.

This study presents a new regional-scale 3D reconstruction of the major Plio–Pleistocene tectonostratigraphic surfaces of the Po Plain Basin (Italy), providing new constraints on the deformation history of this key Mediterranean foreland basin. The model was constructed by interpreting several thousand 2D pre-stack time-migrated (PSTM) seismic profiles, calibrated with an extensive wellbore database. This approach enables a robust regional mapping of structural elements and defined Plio-Pleistocene unconformities.
The results show that the Plio-Pleistocene architecture of the Po Plain is controlled by the interaction of two different geodynamic systems, resulting in a complex source-to-sink system.  Since the Plio-Pleistocene, the advancing Northern Apennines (NA) thrust belt has mostly generated accommodation space, whereas most of the sediment supply came from the Southern Alps (SA). 
Isobath maps provide new temporal constraints on the timing and style of deformation, particularly in the central sector of the Po Plain, where the outermost buried fronts of the NA, belonging to the Emilian Arc fold system, are nearly in direct contact with the outermost fronts of the SA. Our reconstruction demonstrates that the evolution of the NA thrust front was strongly influenced by the presence of the buried SA to the north. Where the NA collided with the SA, out-of-sequence thrusting was triggered within the internal sector of the NA from the middle to late Pliocene, locally persisting until the late Pleistocene. In contrast, where this interaction did not occur, the NA thrust front evolved following a classical in-sequence style, highlighting significant along-strike variability in the structural evolution of the Northern Apennines.
The detailed 3D reconstruction of the entire Po Plain subsurface further allows a robust analysis of the progressive reorganization of basin depocenters through time via the calculation of isochore maps. Beyond providing a three-dimensional depiction of this evolution, these maps enable quantification of sediment volumes deposited between successive unconformities and, subsequently, the calculation of sedimentation rates across the basin.
Decompacted volume analysis reveals a marked increase in sediment accumulation during the Pleistocene, from approximately 31,041 km³ for the entire Pliocene, with a rate of 10.594 km³/Ma to about 60,646 km³ for the Pleistocene, with a rate of 25.269 km³/Ma, based on a 50% sand–50% shale decompaction model. This increase occurred despite an overall reduction in tectonic activity during the Pleistocene within the Alps, the primary sediment source region. This apparent paradox is interpreted as the result of strong climatic forcing associated with progressive climate deterioration and the onset of major Alpine glaciations, which dramatically enhanced erosion in the surrounding orogenic belts. The resulting increase in sediment flux, together with a major marine regression, drove rapid basin infilling and large-scale eastward progradation of the Po Basin system. These findings highlight the fundamental role of climate–tectonic coupling in controlling the evolution of the Po Plain over the last 5 Myr.

How to cite: Barrera, D., Toscani, G., and Di Giulio, A.: How Two Orogens Shaped and Filled a Foreland Basin: Plio-Pleistocene Tectonic and Climatic Controls on the Po Plain Basin (Italy) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8275, https://doi.org/10.5194/egusphere-egu26-8275, 2026.

The analysis of clastic sequences is fundamental for understanding plate dynamics, as it record variations in depositional environments and source-to-sink systems. Since the late Paleozoic, contemporaneous with the convergence between the paleo-Pacific plate and Gondwana, sedimentary basins developed in both forearc and retroarc positions of the Gondwanide orogenic system. The Beacon Supergroup in Antarctica and the Parmeener Supergroup in Tasmania represent the sedimentary infill of the Transantarctic Basin, located in a retroarc setting. These successions are mainly composed of fluvial sandy and muddy deposits, which are poorly deformed and currently unconformably overlie older units. Deposition began in the Devonian and ended in the Early Jurassic, spanning more than 200 Myr and encompassing  key events in the history of the Earth, such as the Late Paleozoic Ice Age, the subsequent transition from icehouse to greenhouse conditions, and the Permian-Triassic mass extinction. The composition of sandstones within the Beacon and Parmeener supergroups varies through time and space, correlating with major tectonic processes driven by subduction dynamics, which ultimately controlled the source-to-sink systems feeding these clastic units. Variability in sandstone composition is documented through a quantitative analysis of all available published data, integrated with new datasets from the Transantarctic Mountains and Tasmania. The results reveal a shift from quartz-feldspar-dominated sandstones, indicating derivation from crystalline basement, to volcanic lithic fragment rich sandstones, reflecting a provenance from coeval volcanic arc rocks. This provenance shift occurred diachronously along the basin, whit volcanic component appearing in the central Transantarctic Mountains during the Permian and in Victoria Land and Tasmania during the Triassic. Sandstone composition further indicates that the Victoria Land region evolved from an intracratonic basin in back-bulge position to a foredeep basin setting.

How to cite: Zurli, L., Fioraso, M., Perotti, M., Di Giulio, A., Olivetti, V., Pezzoli, S., Corti, V., Stendardi, F., and Cornamusini, G.: Tracing the evolution of the Transantarctic Basin (southern Gondwana) through sandstone petrography, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8585, https://doi.org/10.5194/egusphere-egu26-8585, 2026.

The contact between the northern edge of the Higher Himalayan Crystalline (HHC) and the overlying Tethyan Sedimentary Sequence (TSS) has long been debated as either a thrust or a normal fault. Initially thought to be a thrust contact, it was later recognized as a zone of crustal-scale normal faults dipping to the north, known as the South Tibetan Detachment System (STDS). This suggests that the overlying TSS has moved northward along the contact relative to the HHC footwall. The cause of the initiation of such a crustal-scale normal-fault system in a convergent setting remains poorly understood, which motivates the present study to re-examine the structure of the HHC-TSS contact in the Dhauliganga valley of the Garhwal Himalaya. Nevertheless, we identified a series of normal faults cutting across the regional foliation of the HHC-TSS rocks during our field investigation, characterized by intense brecciation and gouging, consistent with upper-crustal brittle deformation. Our field observations suggest that these faults primarily formed during the waning phase of Himalayan growth and are unrelated to the northward slip of the TSS over HHC, as these normal faults cut across all dominant structural elements, including the migmatitic layering of HHC at high angles.  In addition, we found a spectacular ductile shear zone within the Milam Formation of the TSS, located directly above the HHC. This zone provides strong evidence of south-vergent thrusting along the contact, as indicated by fold asymmetry, C-S structures, and low-angle Riedel shears, consistent with the Himalayan deformation. Microstructural studies of shear-zone samples reveal that quartz grains are predominantly stretched as we expect in a ductile shear zone, forming lenticular ribbons with high aspect ratios and undulose extinction, whereas the occurrence of smaller, unstrained grains along the edges of larger grains is indicative of subgrain rotation recrystallisation typical of high temperatures (~400°-500°C). XRD analysis further confirmed the presence of graphite in the mylonitized samples, and the alignment of graphite along shear fabrics suggests the influence of shear heating during their formation. Our new findings of deformation structures along the HHC-TSS contact recognize the importance of reevaluating and expanding our understanding of the structural evolution in this area, particularly in the context of the India-Eurasia collision. Based on field and microstructural observations, we suggest that the collision between India and Eurasia caused the TSS to thrust over the HHC, while steeply dipping normal faults that have affected all previous structural features in the HHC and TSS are a later phenomenon that helped the Himalayan mountain belt attain stability of the Himalayan wedge from a supercritical stage.

How to cite: Das, A. and Bose, S.: Deformation at the contact between the Higher Himalayan Crystalline and the Tethyan Sedimentary Sequence: Thrusting versus normal faulting conundrum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9016, https://doi.org/10.5194/egusphere-egu26-9016, 2026.

The Campanian/Maastrichian to Lutetian Alpine flysch sequences of the Schlieren- and Gurnigel nappes record deposition in an ocean-continent subduction setting related to Alpine orogenesis. Despite extensive studies of these flysch deposits, the existence of a source-to-sink relationship between the two units remains debated. Here, we logged 50-70 m-thick successions of the Gurnigel and Schlieren deposits at two sites, respectively, at a scale of 1:20. The ages of the analysed sediments range from the Thanetian to the Lutetian. We measured the paleoflow directions using sole marks and cross-bedding, and conducted drone surveys to document the large-scale depositional architecture. Our aim was to reconstruct a potential proximal-to-distal relationship between the two sequences.

In the Schlieren nappe, the analysed sediments are dominated by coarse-grained (grain size up to 2 mm) sandstone beds <5 m thick, characterised by a matrix-supported fabric and sole marks at their bases. The finer-grained sandstone beds (grain size up to c. 0.6 mm) are <50 cm thick. They display a massive, grain-supported fabric with normal grading at the base, followed by parallel lamination and occasionally ripple marks at the top. Mudstone beds (clay and silt fraction) are up to 30 cm thick. They are massive to parallel-laminated and locally show bioturbation. Mudstone beds contribute to <10% to the entire suite. Paleoflow directions scatter between the NE and SE. Drone surveys disclose the presence of troughs up to 7 m deep and ten meters wide. They are cut into sandstone beds and backfilled with coarse-grained, massive to laminated sandstones.

By contrast, the Gurnigel sequences are dominated by a succession of sandstone beds with mudstone interbeds. Sandstone beds are <1.5 m thick. They have a planar base, are medium- to fine-grained (grain size ranging from c. 0.1 to 0.6 mm) and show a fining-up trend. Individual beds display a succession of sedimentary structures occasionally starting with a massive fabric. It is followed by mm-scale plane lamination, ripple marks with convolute bedding and sub-mm laminations towards the top. Mudstone interbeds, up to 30 cm thick, are massive to parallel laminated and strongly bioturbated, comprising up to 40% of the surveyed outcrop. Drone imagery shows that laterally continuous, horizontally layered beds dominate the overall architecture. However, lenticular sandstone beds with scours up to 50 cm deep occur locally. Sole marks and cross bedding indicate paleoflow toward the S and W.

The sedimentary structures indicate that the Schlieren sediments were deposited predominantly by (hyper)concentrated, friction-controlled flows and concentrated currents where grain-grain interactions dominate. In contrast, the Gurnigel sediments most likely accumulated from surge-like turbidity flows driven by dynamic pressure. Although the inferred surges recorded in the Gurnigel sediments could, in principle, have resulted from flow separation – with coarse-grained material accumulating in the more proximal Schlieren area and finer-grained fractions being deposited in a more distal setting such as the Gurnigel realm – we discard this interpretation. This conclusion is supported by the opposite paleoflow directions, which indicate that no source-to-sink relationship existed between the two depositional systems.

How to cite: Swaton, S. J., Bozetti, G., Schmidt, C. L., Epprecht, B. L., Graf, G. L., Hermann, J., and Schlunegger, F.: Sedimentary architecture of Late Cretaceous to Early Eocene flysch sequences in the Swiss Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9943, https://doi.org/10.5194/egusphere-egu26-9943, 2026.

The Eastern Anatolian Plateau is a broad, high-elevation (~2 km), low-relief collisional plateau in eastern Turkey that developed following the Arabia-Eurasia collision and the transition to a post-collisional tectonic setting. It occupies a central position between the Bitlis-Zagros suture to the south and the Eastern Pontides-Lesser Caucasus mountain ranges to the north and is associated with widespread Neogene volcanism. Since the Early-Middle Miocene, uplifted regions along the Bitlis segment of the Arabia-Eurasia convergence zone, including parts of the Eastern Anatolian Plateau, were drained toward the northern Eastern Mediterranean, delivering large volumes of sediment to the deep sea and forming thick flysch successions. These deposits archive the crustal inventory exposed at the time and provide a valuable record of the tectono-magmatic evolution of the convergence zone. Here, we present detrital zircon U-Pb-Hf data from Late Miocene sediments recovered from DSDP Sites 375/376 and ODP Site 968 in the northern Eastern Mediterranean to constrain the sequence of tectono-magmatic events associated with Arabia-Eurasia convergence, with particular emphasis on the timing of the establishment of a post-collisional regime. Detrital zircon U-Pb-Hf data record Upper Cretaceous and Eocene magmatic flare-ups related to Neotethys subduction, as well as a prominent Miocene magmatic flare-up with distinct age modes at ~17, ~11, and ~6 Ma associated with the transition to a post-collisional regime. Hf isotope compositions of Miocene detrital zircons reveal a systematic shift from highly variable, evolved signatures before ~13 Ma to predominantly juvenile signatures thereafter. This shift indicates an increasing contribution of mantle-derived sources to magmatism since the mid-Miocene, relative to earlier evolved or mixed mantle-crustal sources. We interpret this transition to indicate that Neotethys slab break-off or lithospheric mantle delamination beneath Eastern Anatolia had largely progressed toward completion by ~13 Ma, signaling the establishment of post-collisional tectonic conditions. Notably, this transition slightly predates the inferred onset of plateau uplift at ~11 Ma, suggesting that mantle reorganization beneath Eastern Anatolia preceded, and was not synchronous with, the surface expression of uplift.

How to cite: Glazer, A., Avigad, D., and Morag, N.: Dynamic Mantle Support Beneath the Eastern Anatolian Plateau Since ~13 Ma Inferred from Zircon Hf Isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11098, https://doi.org/10.5194/egusphere-egu26-11098, 2026.

One of the main ways in which deep seated tectonic or geodynamic processes influence the Earth's surface is by driving rock uplift. Variations in rock uplift through space and time combine with surface processes, such as erosion in rivers and on hillslopes, to shape the surface landscape. These relationships imply that, if we can adequately parameterise surface processes, we may be able to infer rock uplift histories from observations of present day topography. Efforts to do so formally using inverse modelling have mostly focused on the shapes of river profiles. Such approaches can reproduce well observed profiles, and yield uplift histories broadly consistent with independent constraints. However, they generally assume a fixed drainage planform, and neglect any information stored in the rest of landscape (i.e., in hillslope topography). Landscape evolution models, which include descriptions of hillslope processes and allow drainage planforms to evolve, may address these issues, but come with their own challenges. In particular, a strong dependence of modelled drainage planforms on the initial condition, which is generally poorly constrained, complicates direct comparison of observed and modelled topography.

Here, we explore the utility of hypsometric curves – cumulative distribution functions of elevation within a domain – in inverse landscape evolution modelling (we also include equivalent functions for slope and curvature). These curves' integrative nature should make them relatively insensitive to the precise positions of individual valleys and ridgelines. By comparing hypsometric curves from many simulations, with and without added noise, we assess their sensitivity to initial conditions, erosional parameters and uplift histories. We confirm that hypsometric curves are insensitive to initial conditions, particularly when normalised by the mean – rather than, as is traditional, the maximum – value in the domain. For landscapes in a dynamic equilibrium with the imposed uplift rate, the main control on the normalised hypsometric curve is the relative importance of fluvial and hillslope processes. Multiple erosional parameters influence this balance, introducing trade-offs to the misfit space. Nevertheless, individual parameters do have subtle secondary effects that allow them to be determined independently, at least for relatively low noise levels. In transient landscapes, features of simple uplift histories – such as timings and amplitudes of step changes in uplift rate – also appear to be recoverable. We conclude that hypsometric curves can form useful bases for inverse landscape evolution modelling, which could in turn provide novel insights into the tectonic and geodynamic processes that drive rock uplift.

How to cite: McNab, F., van der Beek, P., Schildgen, T., and Turowski, J.: Inferring uplift histories from landscapes using hypsometric curves, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11459, https://doi.org/10.5194/egusphere-egu26-11459, 2026.

The Prealps represent a complex nappe system consisting of Mesozoic to early–middle Cenozoic sediments deposited in the Penninic domains, detached from its substratum during the Alpine orogeny. During subsequent phases of subduction and collision, these nappes were transported along the active plate interface between Adria and Europe far to the north. Today, they lay above the transition between the Helvetic Nappes and the Subalpine Molasse. As a result of long-term displacement and successive deformation, the Prealps exhibit a complex structural architecture that records the cumulative tectonic evolution. We developed a 3D model to yield a high-resolution visualization of the structural architecture and its spatial changes within the Préalpes Romandes. These observations allow us to correlate nappe internal deformation with movements of underlying nappes, which is the goal of this work.

The Préalpes Romandes are crosscut by predominantly north–south–oriented sinistral strike-slip faults. These structures range from large-scale faults that transect the entire Prealps nappe stack and accommodate offsets of several kilometers, to minor faults with displacements of only a few meters to tens of meters. Smaller faults are commonly linked by lateral offsets to form continuous step-over fault systems and typically terminate within the detachment horizon. In contrast, larger strike-slip faults must breach the basal detachment of the Prealps to maintain a kinematic balance and are therefore rooted in deeper structural units. Despite a regional change in stratigraphic orientation of approximately 30° from east to west, the orientation of sinistral strike-slip faults remains largely unchanged. An increasing number of NW–SE–oriented dextral strike-slip faults in the eastern Préalpes Romandes indicate a change in the regional kinematic regime.

Based on our results, we interpret that the Préalpes Romandes experienced a young (Miocene) phase of deformation following early stages of subduction related nappe transport. We relate this Miocene phase of deformation to the uplift of the Aar Massif. This caused differential motion beneath the Prealps, which is expressed by strike-slip deformation, rotation and back-thrusting within the Préalpes Romandes. We additionally invoke this motion to have controlled the differential migration within the nappe stack, resulting in ~30° counter-clockwise rotation and a general northwestward displacement of the eastern Préalpes Romandes. In addition, the presence of a northern backstop subsequently promoted the occurrence of a lateral escape along local dextral strike-slip faults. A correlation of our 3D model with seismically active zones at greater depth discloses the occurrence of structures that were offset in response to the uplift of the Aar massif during Miocene times. These observations document a complex multistage deformation sequence associated with late-stage collision and uplift tectonics in the subsurface, where the initial sinistral movement has been disrupted and partially reoriented by the latest tectonic evolution. It also highlights the role of strike-slip structures as key elements for understanding the long-term tectonic evolution of the region.

High-resolution 3D modelling therefore provides a powerful framework to unravel internal structural relationships, integrate them with surrounding geology, and develop coherent palaeogeographic reconstructions through space and time.

How to cite: Drvoderić, S., Herwegh, M., Berger, A., Schlunegger, F., Furlan, M., Kurmann, E., Dall’Agnolo, S., Garefalakis, P., Monti, R., and Musso Piantelli, F.: Indentation tectonics in the Swiss Préalpes Romandes caused by the uplift of the Aar Massif: insights from high-resolution 3D structural modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12076, https://doi.org/10.5194/egusphere-egu26-12076, 2026.

The influence of deep-seated processes on tectonics and magmatism has been documented at large scale in different orogens, such as the American Cordilleras. Understanding how these processes shape orogens through time is essential to disentangle their interactions with climatically-driven surface processes. The Colorado Plateau experienced a complex Cenozoic uplift and exhumation history, yet the drivers, magnitude and timing of the successive exhumation phases, as well as their role in conditioning late-stage canyon incision, remain strongly debated. In particular, the legacy of Farallon slab subduction, through slab flattening, subsequent rollback, and associated uplift from combined tectonics, magmatism, and dynamic topography, may have fundamentally structured the plateau prior to more recent canyon incision.

We combine apatite (U–Th–Sm)/He dating with apatite fission-track analysis from bedrock samples collected along an elevation profile in the Black Canyon of the Gunnison (eastern Colorado Plateau). By integrating these thermochronological data with the timing of regional erosional unconformities, we provide new constraints on the Cenozoic thermal evolution of basement rocks in this area. Our results reveal an early cooling phase between ca. 70 and 60 Ma. This phase is followed by reheating between ca. 35 and 30 Ma, corresponding to a temperature increase of ~40 °C, and by a subsequent cooling phase from 30 to 25 Ma of similar magnitude. A final cooling phase occurring after ~5 Ma is required to reach present-day surface temperatures. We interpret the early cooling phase as exhumation related to Laramide deformation associated with Farallon slab flattening. The reheating phase is contemporaneous with a widespread mid-Cenozoic magmatic flare-up interpreted to reflect slab rollback processes. The reheating may be specifically associated with a regional increase in the geothermal gradient or burial beneath volcanic sequences, or a combination of both. The final cooling phase is attributed to Plio-Quaternary incision of the Black Canyon, which generated ~800 m of relief.

Together, these results highlight how the sequence of slab flattening and subsequent rollback exerted a first-order control on Colorado Plateau surface uplift, exhumation and magmatism, thereby preconditioning the landscape on which Plio-Quaternary canyon incision developed. These thermochronological data will be integrated with existing thermochronological datasets to assess at larger scale the spatio-temporal variability of exhumation and reheating in response to changes in the geometry of the downgoing slab.

How to cite: Margirier, A., Stanley, J. R., Thomson, S., Valla, P. G., Stübner, K., Huppert, K., and King, G. E.: Thermochronological record of slab flattening and roll-back in the eastern part of the Colorado Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13259, https://doi.org/10.5194/egusphere-egu26-13259, 2026.

First-order orogenic arcs are often divided into second-order curves, termed salients and recesses (convex and concave to the transport direction, respectively). Although several studies have analysed the supracrustal factors controlling this festooned geometry, the potential role of deep-seated mechanisms has received little attention.

In the northern branch of the Gibraltar Arc, the orogenic grain of the central and western Betics external fold and trust belt (FTB) draws two secondary arcs, connected by a salient-recces transition segment, whose southernmost limit is the Torcal shear zone (TSZ). The central FTB salient consists of WSW-ENE to W-E thin-skinned shortening structures involving post-Burdigalian, syn-orogenic sequences in its deformation front. Thrust surfaces are dominantly SE to S-ward dipping and slickenlines suggest NNW-SSE to N-S transport directions. At the SW end of this salient, just east of the TSZ, the shortening structures trend becomes N-S. The westernmost FTB salient, within the Gibraltar Arc hinge, is defined by NW to W-ward verging, shortening structures with radial transport direction. Arc-parallel extension occurred coeval with arc-orthogonal shortening. Both salients are connected by the aforementioned transitional domain, an E-W to ENE-WSE transpressive band, dominated by dextral strike-slip deformation. This transpressive zone is significantly segmented into scattered topographic highs due to  orogen-paralell extension, mainly  accommodated by NW-SE  normal and dextral faults.

These three tectonic domains seem to have been differentiating since the upper Miocene to Holocene suggesting a decoupling between the W-ward migrating hinge of the Gibraltar Arc and the rest of the arcuate chain. Such decoupling would fit well with the existence of a W-E trending STEP fault, whose easternmost tip were located under the transition between the central and western Betics. Thus, the dominantly dextral, significantly stretched TSZ, located just north of the betic FTB/hinterland boundary, would be the expression in the FTB of such deep STEP fault. In this context, the recent FTB deformation in the central Betics would respond mainly to the current NW-SE shortening undergone by the Iberian Peninsula, whereas the kinematic features of both the transitional transpressive band and the westernmost FTB are consistent with a WNW-ESE directed far field vector associated with the arc westward migration. Interestingly, the recent intraplate deformation in the Betics foreland has produced greater relative uplifts in front of the central Betics, mostly accommodated in overall WSW-ENE faults, than in westernmost sectors. Additionally, the kinematics of reactivated structures in the westernmost sector of the foreland is compatible with a WNW-ENE convergence. Assuming some amount of mechanical plates coupling along the northern branch of the Betics, these foreland deformation features would agree with the proposed difference in the convergence angle along the central and western Betics FTB.

This work is supported by projects PID2024-159481NB-I00 and by ERDF/EU.

How to cite: Expósito, I., Díaz-Azpiroz, M., Jiménez-Bonilla, A., and Balanyá, J. C.: Kinematic Decoupling and Orogenic Trend Variations in Arcuate Fold-and-Thrust Belts: Exploring Possible Deep Controls, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13851, https://doi.org/10.5194/egusphere-egu26-13851, 2026.

At 30º South, the western Central Andes are comprised by the Coastal Cordillera, a seemingly little-deformed zone containing Mesozoic volcanic arc and back arc-related rocks . To the east, the Vicuña fault separates the Coastal Cordillera from the Principal Cordillera and the Frontal Cordillera. Those two units  display relatively small areas of Mesozoic sedimentary cover that have been preserved despite the uplift which exposes mainly Carboniferous to Triassic plutonics. Further east in the Precordillera, deformation involves increasingly recent Cenozoic sedimentary units.

Based on 2025 campaign field data acquisition and the revision of previous geological maps, we present a structural cross section along a 30ºS, E-W transect and its restoration . During the Mesozoic, extension in the Coastal Cordillera was mainly accommodated by the west-dipping Vicuña fault from the Jurassic to Late Cretaceous. Constraints from pluton emplacement depths and stratigraphic relationships suggest that significant uplift and topographic growth might have interrupted this extension in the Early Late Cretaceous in the Coastal Cordillera. Uppermost Cretaceous syn-orogenic deposits mark the onset of contraction. Upon shortening, the Vicuña fault was folded and reactivated as a west-vergent thrust during the uplift of the Principal Cordillera. This shortening episode also created the present-day relief in the Coastal Cordillera although the timing of this uplift is not well constrained. Subsequently, shortening propagated eastwards into the foreland of the orogen, forming the folds and thrusts of the Precordillera.

Our cross section suggests successive phases of extension and compression which can alternate at variable timescales and operate in different locations. This tectonic evolution raises numerous questions: Which geodynamic factors drive the occurrence of contraction or extension? What is the relationship between surface and deep crustal structures? In a non collisional context, what controls the localization of deformation?...

How to cite: Munday, W., Santolaria, P., and Muñoz, J. A.: Andean Cross Section at 30ºS: A Window Onto the Tectonic Evolution of a Non-Collisional Orogen, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14604, https://doi.org/10.5194/egusphere-egu26-14604, 2026.

The northeastern margin of the Arabian Plate, now represented by the Zagros Fold–Thrust Belt, records the tectonic evolution of the region from Paleozoic rifting and the opening of the Neo-Tethys Ocean to Mesozoic convergence and Cenozoic continental collision. Furthermore, under oblique collision, late Cenozoic deformation is partitioned between right-lateral strike-slip motion along the Main Recent Fault in the northeast (NE) and a shortening component across the Zagros Fold–Thrust Belt. In this study, we examined the brittle structures that developed during deformation in the northwestern segment of the Zagros Fold–Thrust Belt, within the Kurdistan Region of Iraq. Our goal was to reconstruct the deformation history and spatial variations in stress. We collected approximately 250 fault-slip measurements at 28 localities along a transect crossing the belt, from the Zagros Suture Zone in the northeast to the Foothill Zone in the southwest. We applied paleostress inversion techniques to the dataset, enabling identification of distinct stress regimes in the region. Our initial results indicate temporal changes in the paleostress regime, which could be linked to a slight anticlockwise rotation associated with oblique collision. These paleostress analyses have implications for reconstructing convergence direction, kinematics, and the temporal evolution of the orogen.

How to cite: Zebari, M., Navabpour, P., and Ustaszewski, K.: Paleostress Reconstruction in the Zagros Fold–Thrust Belt, Kurdistan Region of Iraq: Implications for the Arabia–Eurasia Convergence and Oblique Collision, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14813, https://doi.org/10.5194/egusphere-egu26-14813, 2026.

Topography is a direct manifestation of the coupling of tectonic and surface processes and this connection between rapid erosion and high uplift rates is most readily evident in the frontal High Himalayas– an area that provides an excellent opportunity to study the progressive evolution geomorphic features in response to the interplay of these processes. An abrupt topographic break between the low-relief Lesser Himalaya and the high-relief Greater Himalaya has received significant attention, but the processes that govern its evolution remains debated. While it is commonly accepted that active tectonics are required to produce the topographic break, it remains debated whether it is driver by a blind mid-crustal ramp or discrete thrust faulting that daylights at the mountain front. Evidence for out-of-sequence thrusting has been documented along the orogen at similar elevations as the topographic break, suggesting active surface faulting could play a major role in generating and sustaining this marked topographic break. In central Nepal, where the topographic break is most pronounced, thermobarometric data indicate pronounced differences in maximum pressure temperature estimates (>300°C, >4 kbar) experienced by juxtaposed Greater Himalayan units. Consequentially, this structure likely plays a major role in accommodating shortening within the orogen, which is expected to build significant topography. In the Annapurna region, this boundary lacks a thick mylonitic shear zone, suggesting that it may have experienced recent brittle activity. This study investigates neotectonic offsetting and warping of fluvial terraces that record recent thrust activity within the past tens of thousands of years. Newly available two-meter resolution digital elevation data coupled with field observations, provide an unprecedented opportunity for identifying neotectonic deformation of fluvial terrace geometries across the topographic break. We present terrace tread data from the Seti river drainage in central Nepal. An important limitation, however, is that these digital elevation data allow for detailed imaging of terrace tread deposits, rather than bedrock strath terraces, and thus are also influenced by sedimentation processes. We present preliminary interpretations based on first-order changes in terrace tread geometries over kilometers distance, ensuring that evidence is recorded across multiple terrace levels, and in some cases supported by additional bedrock data. Seti River terrace tread profiles suggest divergence upstream of the topographic break, which can be caused by differential uplift or changes in sediment flux. Multiple terrace levels also appear folded near the structural position of the Chamrong thrust, mapped in the neighboring Modi Khola drainage. At this location, we also report evidence of pervasive brittle bedrock deformation. The combination of these features suggests possible tectonic deformation at multiple locations along the Seti River that are consistent with active brittle out-of-sequence thrusting along the mountain front. We plan to combine these data with UAV models of strath terrace geometries to clarify these preliminary interpretations.

How to cite: Preece, M., Stockli, D., Thigpen, R., and Gallen, S.:  Insight on recent tectonic deformation in the Himalayas of central Nepal provided by fluvial terrace geometries , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15999, https://doi.org/10.5194/egusphere-egu26-15999, 2026.

The Korean Peninsula is located along the eastern margin of the Eurasian Plate and is characterized by a pronounced east-high, west-low topography, commonly attributed to Cenozoic tectonic processes associated with the evolution of the East Sea (Sea of Japan). The East Sea is a back-arc basin that opened from the Early Oligocene (ca. 32 Ma) to the late Middle Miocene (ca. 12 Ma) and has been subjected to an E–W compressional stress regime since the Early Pliocene (ca. 4 Ma). Quaternary marine terraces indicate rapid uplift along the east coast (200–300 m/Myr), whereas the western coast shows relative stability or subsidence, suggesting strong spatial heterogeneity in recent crustal deformation. However, low-temperature thermochronological data generally indicate more moderate long-term Cenozoic exhumation rates, implying that the rapid Quaternary uplift reflects late-stage acceleration rather than long-term average behavior.

To investigate the long-term cooling and exhumation history of the Korean Peninsula, we conducted zircon and apatite fission-track (FT) dating on 21 samples from 12 plutonic bodies. Zircon FT ages range from ca. 173 to 51 Ma, and apatite FT ages range from ca. 46 to 12 Ma, with mean track lengths of 12.94–14.61 μm, indicating no significant post-cooling thermal disturbance. Apatite FT ages are generally older in inland regions (av. ~37.5 Ma) than along the east coast (av. ~25.0 Ma), suggesting long-term differences in cooling and exhumation histories. Assuming a geothermal gradient of ~30 °C/km, average exhumation rates are estimated to be ~90 m/Myr for inland regions and ~150 m/Myr for the east coast. However, fission-track data alone cannot uniquely constrain the timing of possible uplift acceleration. To better resolve late Cenozoic exhumation and assess the role of Quaternary tectonics, apatite (U–Th)/He dating is currently being conducted on selected samples.

How to cite: Chae, Y.-U., Ha, S., Lee, Y. I., Choi, T., Jeen, S.-W., Lim, H. S., and Shin, S.: Reconstructing the Cenozoic uplift history of the Korean Peninsula using fission-track thermochronology: implications for East Asian tectonics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16211, https://doi.org/10.5194/egusphere-egu26-16211, 2026.

The Betic Cordillera of southeastern Spain experienced kilometer-scale surface uplift since the late Miocene, leading to widespread emergence of marine sedimentary units and contributing to the isolation of the Mediterranean Sea from the Atlantic Ocean at the end of the Miocene. Previous geophysical studies have linked this uplift to deep lithospheric processes, particularly the evolution and detachment of a subducted slab beneath the region. However, the geomorphic imprint of these processes across the Betic Cordillera has not been comprehensively characterized.

Here, we investigate the landscape response to late Cenozoic uplift using quantitative geomorphic analysis. We combine high-resolution topography with river longitudinal profile analysis, knickpoint mapping, and river network metrics such as normalized channel steepness (k_sn) and χ-values. This approach allows us to assess spatial patterns of landscape disequilibrium and to infer the evolution of surface uplift.

Our results reveal a clear obliquity between the trend of maximum topography and the main tectonic structures of the Betics, a relationship that differs from other Mediterranean orogens. This anomalous elevation pattern spatially coincides with the region of lithospheric slab detachment previously identified by seismic tomography, suggesting a strong coupling between mantle dynamics and surface deformation. River profile metrics show strong contrasts in k_sn and χ-values across the main drainage divide, indicating a transient, orogen-scale landscape and asymmetric erosion. These contrasts imply active migration of the principal drainage divide toward the Atlantic-facing basins, supported by the presence of wind gaps and river capture features.

Knickpoint distributions further indicate increasing landscape disequilibrium toward the southwestern Betics, consistent with a laterally propagating uplift signal. Together, these geomorphic observations provide independent evidence for epeirogenic uplift driven by slab tearing beneath the Betic Cordillera, with westward propagation rates estimated at approximately 100–160 km per million years.

This work is funded by GEOADRIA (PID2022-139943NB-I00) and MAPA (PIE-CSIC-202430E005) from the Spanish Government and the Generalitat de Catalunya Grant (AGAUR 2021 SGR 00410).

How to cite: Viaplana-Muzas, M., Vergés, J., Jiménez‐Munt, I., Torne, M., Struth, L., Cruset, D., Najafi, M., and García‐Castellanos, D.: Linking Surface Geomorphology to Deep Lithospheric Processes beneath the Betic Cordillera (SE Spain), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20678, https://doi.org/10.5194/egusphere-egu26-20678, 2026.

In the northern Andean block the subducting Nazca plate contains a flat slab segment that notably influences the structural styles of the mountain belts of the Southamerican plate. A seismotectonic break at approximately 4°N is often referred to as the Caldas Tear. In contrast to the obvious aseismic ridges associated with the southern edges of the Peruvian and Chilean flat slab segments, there is no distinct single oceanic feature that limits the size of the North Andean flat slab segment. Instead, a ridge-transform system can be extrapolated into the inboard domain of the trench. This explains the presence of the Istmina Transverse Range along a transform-parallel sector, as well as the Miocene Combia volcanic province where this transform-parallel sector turns into the ridge-parallel discontinuity of the Caldas Tear. Folding of the forearc basins and the Eastern Cordillera of the retroarc domain provides evidence of a margin-wide, NW-SE contractional regime, which has been independently documented by regional paleostress determinations. Further structural evidence for oblique convergence comes from a clear collisional feature formed by a sweeping linear transform fault, which is now situated beneath the Istmina Transverse Range. This feature resulted in a triangular re-entrant of the Western Cordillera, causing it to bend around the Transverse Range. On the retroarc side, the southward propagation of the flat slab segment is evident in fold terminations within the Eastern Cordillera, as well as in the relay pattern of frontal thrust faults at its foothills. The southern morphotectonic break of the Caldas Tear juxtaposes the intramontane Bogotá basin, which belongs to the flat-slab segment, with a folded flank of an E-vergent anticlinorium that marks the deformational style related to the steeply dipping Nazca plate. In our contribution, we depict representative, but less evolved transverse lineaments of the Eastern Cordillera and characterize their deformation style. We also observe the local presence of salt nappes and compare the retarded vs. accelerated intrusive ascent of magmatic manifestations, discussing their relevance with respect to possible plate configurations that suggest lithospheric tearing or bending. The guiding question that informs our research is whether these surface processes provide insight into time slices of the evolving flat slab segment.

How to cite: Kammer, A., Zeilinger, G., Quintero, C. E., and Cifuentes, W. D.: Evolution of the northern Andean Flat Slab Segment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21961, https://doi.org/10.5194/egusphere-egu26-21961, 2026.

The Hellenides constitute a long-lived convergent system resulting from oceanic–continental subduction and subsequent continental collision between Apulia and Eurasia. Their external domain developed above inherited sectors of a hyperextended Mesozoic passive margin, composed of alternating thick carbonate platforms including the Apulian (and Pre-Apulian) and Gavrovo units, and thin basinal domains such as the Ionian. Such inherited structural and stratigraphic architecture exerted a first-order control on thrust localization, wedge geometry, and foreland basin evolution. Since the Late Cretaceous, convergence was accompanied by significant slab retreat, producing a strongly asymmetric orogen with outward thrust propagation in the prowedge and coeval extension in the Aegean region.

We present three E-W, regionally balanced cross sections across the External Hellenides, sequentially restored to constrain the pre-contractional configuration of the sedimentary cover, the kinematic evolution of the thrust belt, and its relationship with inherited rift-related domains and salt-related deformation. The cross sections run through the western Hellenides and are roughly parallel to the main transport direction. The northernmost section crosses the Corfu area, whereas the southernmost profile is located south of the Kefalonia Fault, where the tectonic regime transitions from continental collision to active oceanic–continental subduction.

The sections are based on detailed field surveys along the Ionian structural unit, integrated with published seismic profiles and exploration wells. In the eastern Ionian zone, synclines affecting Jurassic to Oligocene–Miocene flysch are generally broad, whereas toward the west, folding becomes tight to isoclinal, locally forming box-type folds with overturned limbs. Anticlines are tight, variably elongated, doubly plunging, and locally associated with breakthrough thrusts. This structural contrast reflects variations in pre-orogenic stratigraphic thickness and mechanical behaviour: tight folds involve a thin sedimentary cover detached on Triassic salt, while broader synclines record deformation of thicker, locally welded successions. The pre-contractional Ionian basin consisted of a salt-influenced deeper-water carbonate system with salt pillows and plateaus, and subsident areas receiving episodic carbonate debrites from adjacent shallow-water domains. The absence of halokinetic sequences in the pre-orogenic succession suggests that diapirism in the study area was exclusively syn- to post-shortening and controlled by shortening-related uplift and erosion.

During contraction, all the Ionian structural units show regionally consistent allochthonous behaviour, detached along Triassic evaporites and overthrusting the autochthonous structural units together with Aquitanian deposits, as documented by tectonic windows. Progressive Miocene deformation involved thicker sub-thrust units, producing broader structures that subsequently controlled deformation of the overlying thinner Ionian units.

Sequential restoration from the Oligocene to the present reveals forward-propagating thrusting consistent with a prowedge-dominated orogen above a retreating slab. This supports an evolution in which thin-skinned deformation above Triassic evaporites and subsequent reactivation of sub-thrust structural units was driven by underplating of Adriatic crust beneath the External Hellenides. Our balanced cross sections provide quantitative constraints on the relative proportions of accreted versus subducted continental crust of the former hyperextended margin, and allow prosing a tentative location for the transition between the Pre-Apulian ramp and the Ionian basinal domain, which acted as precursor for thrust nucleation.

How to cite: Snidero, M., Martinez Granado, P., Santolaria, P., and Muñoz, J. A.: Thrust tectonics in the External Hellenides: from a salt-bearing rifted margin to convergence in a retreating subduction zone , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22451, https://doi.org/10.5194/egusphere-egu26-22451, 2026.

Landslides are key geomorphic features on Mars that record past climate conditions, slope stability, and volatile-driven processes. We present a regional inventory of 290 landslides between 20°S and 50°S on Mars, focusing on Late Amazonian events underrepresented in global databases. To map landslides, we used high-resolution Context Camera (CTX) (5 m/px) satellite imagery, and detailed morphometric analyses were performed using stereo-derived CTX Digital Elevation Models (DEMs) (6 m/px) satellite. The mapped landslides were classified into three major types: rock avalanches, slumps, and ejecta-type features. Our results indicate that landslide areas range from 0.26 to 174 km², with estimated volumes between 0.003 and 5.72 km³. The height-to-length (H/L) ratios, varying from 0.00013 to 0.268, reveal substantial differences in mobility and formation mechanisms. Approximately 40% of landslides at high southern latitudes display morphologies suggestive of basal ice lubrication or cryosphere involvement, supporting ice-facilitated movement mechanisms. Crater size-frequency distribution (CSFD) analysis constrains absolute model ages of these landslides between 3.50 and 480 Ma (Middle to Late Amazonian), indicating repeated mass-wasting activity over extended geological timescales.

Spatial correlation analyses between landslides and glacial features such as Lineated Valley Fill (LVF), Lobate Debris Aprons (LDA), and Concentric Crater Fill (CCF) reveal a strong association between ice-bearing terrains and enhanced landslide mobility. These findings indicate that subsurface ice acted as both a stabilizing and lubricating agent, reducing basal friction while promoting high mobility under favourable thermal conditions.

These results provide the first comprehensive dataset of southern mid-latitude landslides, filling a major gap in Martian landslide inventories. The morphometric variability observed in this region demonstrates that cryosphere-substrate interactions play a crucial role in shaping Martian slope processes. Our findings underscore the complexity of mass wasting dynamics and their strong linkage to past climate fluctuations, providing new constraints on the timing and preservation conditions of buried ice deposits across Mars' recent geological history.

How to cite: Yazıcı, D., Karagoz, O., Kenkmann, T., Carboni, F., and Görüm, T.: Inventory of young mass wasting events in Mars' Southern Hemisphere: Insights into characterization and formation mechanisms, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-533, https://doi.org/10.5194/egusphere-egu26-533, 2026.

Lunar swirls remain one of the most enigmatic geological features on the Moon's surface. They appear as sinuous, high albedo patterns that are interwoven with “dark lanes” and stand out against the low-albedo background. Their unique spectral properties and strong correlation with lunar magnetic anomalies have attracted widespread scientific interest. The origin of lunar swirls is still debated. The prevailing solar wind deflection model suggests that pre-existing magnetic anomalies deflect incoming solar wind particles, leading to different degree of space weathering inside and outside the swirls and resulting in their distinctive spectral characteristics. As a key product of space weathering, nanophase iron (npFe⁰) directly reflects this differences inside and outside the swirls. In this study, we investigated the npFe⁰ content distribution of the swirl regions, offering a new perspective on the origin of lunar swirls.

In this study, we developed a model to estimate npFe⁰ content in lunar highland and maria soils using band ratio of remote sensing data based on laboratory-measured spectral data and npFe⁰ content of returned Apollo lunar samples. Then, this model was employed to the hyperspectral data acquired by Chang’E-1 Interference Imaging Spectrometer (IIM) to map the npFe⁰ content across five typical lunar swirl regions including Reiner Gamma, Mare Ingenii, Rima Sirsalis, Airy, and Firsov. Our results showed that npFe⁰ content in on-swirl regions is lower than that in off-swirl regions, indicating a suppressed space weathering effect within the swirl regions. Moreover, the relative npFe⁰ abundance between swirl dark lanes and surrounding off-swirl regions seems to be linked to different stages of space weathering. The distinct difference in npFe⁰ abundance between on-swirl regions and off-swirl fresh craters could be due to their different weathering processes. Additionally, we found a correlation between npFe⁰ abundance and the intensity of lunar magnetic anomalies in swirl regions. This indicates that the shielding effect of magnetic anomalies against solar wind particles may be influenced by the strength of the magnetic field. A potential relationship between npFe⁰ and OH^-/H₂O distributions within swirl regions also offer valuable insights into the solar wind-induced formation of lunar surface water. These findings support the hypothesis that incoming solar wind particles are deflected in swirl regions, leading to reduced space weathering on their surfaces.

How to cite: Liu, D., Li, Z., Zhang, Z., Zhang, H., and Li, C.: Formation of lunar swirls: Implications from Chang’E-1 Interference Imaging Spectrometer data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2886, https://doi.org/10.5194/egusphere-egu26-2886, 2026.

China's Tianwen-2 exploration mission is designed to perform comprehensive remote sensing, in-situ exploration, and sample return from the target small celestial bodies (2016HO3 and the main-belt comet 311P) through a series of operations including flyby, orbiting, landing, and sample collection. The mission will further investigate the formation and evolution of these target celestial bodies, their orbital dynamics, as well as correlations between the returned samples, meteorites, and data obtained from ground-based and remote sensing observations. Prior to the launch of the Tianwen-2 mission, we carried out comprehensive ground-based test to verify the detection capabilities of its nine onboard payloads and to assess the accuracy of the data they are designed to acquire. 

Results show that all payloads have met the predetermined test objectives, demonstrating robust detection performance and reliable data validity. The images obtained by the Asteroid Medium Angle Camera and Narrow Angle Camera deliver images with a modulation transfer function (MTF) ≥ 0.2, capable of providing high‑quality imagery for morphological studies. The Asteroid Laser Detection and Ranging achieves a measurement accuracy better than 3cm, enabling precise acquisition of three-dimensional topographic data of the asteroid surface. Spectral data obtained by the Asteroid Multispectral Camera, Visible and Infrared Imaging Spectrometer, and Thermal Emission Spectrometer show good agreement with reference measurements from standard instruments, confirming their capability to identify various minerals. The Dust Multi-properties Analyzer module of the Asteroid Dust and Volatiles Analyzer successfully measures dust‑particle size, morphology, velocity, and mass. The Volatiles Ion Trap Analyzer module of the Asteroid Dust and Volatiles Analyzer can detect no fewer than 14 gas species, with concentration measurement accuracy better than 33%. Using a dual‑probe gradient magnetic‑field measurement method, the Asteroid Magnetometer effectively suppress spacecraft magnetic interference and acquired valid magnetic-field information of the detection target. The Asteroid CoreScan Radar can achieve penetration depths of 35m and 5m for its low-frequency and high-frequency channels, respectively.

How to cite: Li, C.: Ground Verification Test for Tianwen-2 Payloads, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2921, https://doi.org/10.5194/egusphere-egu26-2921, 2026.

Throughout our Solar System, erosional processes reshape the surfaces of terrestrial and icy bodies, ranging from planets and moons to asteroids and comets. One such process is mass wasting, which transports loose material downslope driven by gravity, forming slides, avalanches or flows depending on conditions. Over the past decades, the role of volatiles in their formation has been debated. Our understanding of extraterrestrial mass wasting relies heavily on Earth analogues; however, these are mostly influenced by liquid water, which is not stable on other planetary surfaces. Yet, numerous extraterrestrial landforms indicative of mass wasting occur on planetary surfaces with (seasonal) ice or frost and on slopes too gentle for dry material to move unaided.
Ice sublimation is a potentially plausible mechanism for driving extra-terrestrial mass wasting, whereby solid volatiles directly transition into vapour. This can initiate flow and reduce friction between sediment particles. However, because of the lack of terrestrial analogues and the complexity of producing a usable numerical model, the mechanics of sublimation on sediment mobilisation, particle dynamics and flow behaviour remain unclear. Here, we investigate the roles of volatiles and environmental conditions on the mobility and dynamics of sublimation-driven mass wasting and the morphology of their deposits.
Over the past two years, we created flows driven by sublimating CO₂ using flume set-ups in two low-pressure chambers at the Open University (Milton Keynes, United Kingdom) and Aarhus University (Aarhus, Denmark). Ambient pressure was varied stepwise from 0.1 to 1000 mbar to cover the
environmental conditions of a broad range of terrestrial and icy bodies. The mass flows consisted of dry ice mixed with either high-density (∼ 2600 kgm⁻³) or low-density granular material (410 - 1300 kgm⁻³), the latter was utilised to simulate reduced gravity. The results show that reduced ambient pressures increase the volume flux of gas, thereby enhancing the fluidisation, flow mobility and runout length, particularly for low-density flows. This suggests that terrestrial bodies with lower surface gravity have more mobile sublimation-driven flows. The behaviour of the mass flows varied noticeably with ambient pressure, showing transitions through different fluidisation regimes, each marked by distinct features. At high pressures (> 20 mbar), we observe steady flows. In the 20 - 1 mbar range, the flows start to exhibit bubbles, surges and outbursts. Below 1 mbar, turbulent behaviour emerges with a diffuse particle suspension flowing above a dense layer. These behavioural regimes are similar to the regimes observed in fluidised bed experiments and have been recognised in snow avalanches and pyroclastic density currents on Earth. Currently, we are analysing internal particle dynamics and velocities for these regimes using particle tracking software. Our research shows that sublimation can be an effective driver for mass wasting on terrestrial bodies with low ambient pressures, low gravity and the presence of volatiles other than water, and might operate in distinct fluidisation regimes.

How to cite: Diamant, S., Conway, S., Roelofs, L., Sylvest, M., Emerland, Z., Merrison, J., Iverson, J. J., Kleinhans, M., McElwaine, J., Patel, M., and de Haas, T.: Flow dynamics and behavioural characteristics of sublimation-driven granular flows under laboratory conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5111, https://doi.org/10.5194/egusphere-egu26-5111, 2026.

The Curiosity rover continues its exploration of Mount Sharp, Gale crater’s ~5000 m-high sedimentary pile, and has been traversing for the past three years the Layered Sulfate unit (LSu), an interval initially characterized from orbit and thought to have recorded a global climatic transition toward the more arid conditions we observe nowadays on Mars. This unit, also informally known as the Mirador formation, is rich in sulfates and record mostly aeolian settings. Unexpectedly, the rover has also encountered numerous strata arguing for a recurring aqueous activity punctuating the overall arid, aeolian depositional environment.

Lately, Curiosity explored the “boxwork” unit, a high-interest region named after the orbital observation of “box-forming”, (deca-)meter-scale rectilinear features cropping out of the ground. Diagenetically-altered, fine-grained rocks making the most of the boxwork unit are probably of lacustrine origin, stressing out the importance of these aqueous conditions in the midst of the LSu. But when looking at the walls of this valley, made up of the Texoli, Mishe Mokwa and Cordillera buttes, we notably observe coarser-grained, erosion-resistant beds displaying a wealth of multi-scale sedimentary structures.

Among them are several occurrences of clinoform geometries that we sorted into three classes. Type 1 are characterized by inclined, sigmoidal to poorly cross-bedded strata, filling meter-scale, individualized lens-shaped bodies. Type 2 are characterized by inclined strata, sigmoidal but more cross-bedded strata. They are also observed filling lens-shaped bodies, but contrary to Type 1, these lenses are laterally stacked and cross-cutting each other’s immediate neighbor. Finally, Type 3 clinoforms occur in unconfined packages evidencing clearly sigmoidal, steeply-dipping (15-20°) and non-cross-bedded strata. While they are conformable with lower sub-horizontal layers pertaining to the bedrock, their top is mostly truncated by unconformable sub-horizontal layers. At the outcrop, the steeply dipping, sigmoidal strata also define a conspicuous lobate shape.

We interpret Types 1 and 2 clinoforms as the record of fluvial channels, with Type 1 a record of braided rivers and Type 2 a record of laterally migrating bars of a meandering river. Type 3 marks a conspicuous change and we interpret the vertical tripartite stratal pattern as bottomsets, foresets and topsets of a Gilbert-deltaic suite. These strata reflect fluvial to deltaic depositional settings with decreasing levels of energy from strictly fluvial, individual channels (Type 1), meandering channels (Type 2) and finally within a delta (Type 3).

These settings are in line with the quieter, presumably lacustrine, environment the boxwork unit’s strata likely origin from, and could represent the local sedimentary input. They contrast with the overall arid, aeolian structures observed to make most of the surrounding buttes and overall LSu. They nevertheless highlight a recurrence of humid episodes throughout the LSu. These events illustrate a more complex and unpredictable climatic pattern as Mars became colder and more arid.

How to cite: Caravaca, G., Mangold, N., Dromart, G., Rapin, W., Kite, E. S., Williams, R. M. E., Le Mouélic, S., Gasnault, O., Dehouck, E., Lanza, N., Vasavada, A., and Fraeman, A.: Fluvial to deltaic clinoforms observed by Curiosity in Gale crater’s Mount Sharp, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5639, https://doi.org/10.5194/egusphere-egu26-5639, 2026.

Barchans are crescent-shaped dunes found in deserts with little sand, where winds blow continuously in one direction. They migrate in the downwind direction at speeds of several meters per year as sand eroded from the upwind slope is deposited on the downwind side. A characteristic feature of barchans is the localized sand outflow from their downwind-extending horns. Because barchans typically exist in clusters, this horn outflow can become sand inflow to barchans located further downwind, inducing sand-mediated interaction between upwind and downwind barchans.Most previous studies on barchan interaction have focused on direct contact interactions, i.e., collisions. However, it has recently been recognized that non-contact interaction mediated by sand transport can occur without collision. Studies on this type of interaction remain limited.This research focuses on non-contact sand-mediated interaction between upwind and downwind barchans. The interaction is investigated using a simplified crest line model [1]. This model is characterized by a small number of variables, which provides a distinct advantage in making theoretical analysis tractable.We obtain an analytical steady-state solution. The steady-state barchan shape is symmetric with respect to the sand supply source. The steady-state configuration consists of two parabolic solutions whose axes are laterally shifted due to sand inflow and connected at the supply source. Both the crest height of the steady-state barchan and the lateral displacement of the axes can be obtained analytically. We find that the steady-state barchan shape is determined by the migration velocity of the barchan and the sand inflow rate. In addition, the inverse proportionality between barchan height and migration velocity is theoretically confirmed in this study, a relationship well known in previous studies.The analytical solution shows good agreement with our previous numerical results. Our results provide deeper mathematical insight into non-contact sand-mediated interaction in barchan dune fields and offer a foundation for future studies on barchan collisions.

[1] L. Guignier. et al., Sand dunes as migrating strings, Physical Review E (2013)

How to cite: Navarro Yabe, S., Otoguro, K., Ninomiya, H., Shiraishi, M., and Nishimori, H.: The Effect of Sand-Mediated Non-Contact Interaction Between Barchans onTheir Steady-State Profiles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7823, https://doi.org/10.5194/egusphere-egu26-7823, 2026.

This study aims to isolate the effect of gravity on delta morphodynamics, a key uncertainty in interpreting Martian deltaic systems. Terrestrial deltas are commonly used as a framework to interpret deltas on Mars, yet the planet’s lower gravity fundamentally alters sediment transport processes and, consequently, delta morphology and evolution. Previous work has demonstrated that reduced gravity enhances net sediment transport for a given discharge and channel geometry, promoting a higher proportion of suspended sediment transport (Braat et al., 2024). However, the implications of these effects for delta morphodynamics have remained largely unexplored.

We conducted physical experiments in the Earth Simulation Laboratory at Utrecht University. Deltas were formed autonomously in a 3 cm-deep flume with a constant water (300 L/h) and sediment supply (2 L/h). Martian gravity was simulated by reducing the sediment particle weight through the use of low-density grains (nutshell particles, ~1350 kg/m³), thereby isolating sediment density as a proxy for gravitational effects. This approach generated higher mobility sediment and a greater fraction of suspended transport, consistent with expectations for Martian conditions. The resulting low-density deltas were compared to reference deltas formed with standard silica sand (~2650 kg/m³).

The experiments show that reduced sediment density leads to deltas with gentler equilibrium slopes and larger surface areas. The lower equilibrium slope requires little aggradation, and most of the sediment supply can be used for progradation. Low-density deltas also develop more pronounced levees, likely due to enhanced suspended sediment transport. These levees, together with minimal gradient advantages across the delta plain, result in reduced system dynamics: channels are more stable, and large-scale avulsions occur at relatively low frequencies. In contrast, normal-density deltas exhibit more frequent channel migration and avulsions. As a result, low-density deltas develop more irregular, multi-lobed planform geometries, whereas normal-density deltas tend to remain semi-circular or half-oval in shape.

These findings demonstrate that gravity alone can exert a first-order control on delta morphodynamics. Morphological characteristics commonly interpreted on Mars as indicators of fine grain sizes, high sediment mobility, or elevated discharges may instead arise from the effects of reduced gravity. Consequently, caution is required when interpreting Martian deltas solely based on terrestrial analogues.

How to cite: Braat, L.: Rethinking Martian Deltas: The Influence of Reduced Gravity on Delta Morphology and Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11314, https://doi.org/10.5194/egusphere-egu26-11314, 2026.

Slope lineae are bright, elongated streaks on Mercury’s slopes. Along with hollows, lineae are considered one of the youngest geologic features on Mercury. Past surveys suggested a qualitative relation between lineae and subsurface volatiles, implying that lineae could be geologic markers of the recent – and potentially ongoing – release of subsurface volatiles on Mercury. However, lineae have not been systematically mapped across Mercury and no quantitative analysis of their abundance, distribution, and geostatistical properties has been conducted. In [1], we use a deep learning-driven approach to scan through ~112,000 MESSENGER images and catalog slope lineae across Mercury to a) characterize their spatial distribution as well as their morphometric and spectral properties and b) use geostatistical and change detection approaches to explore whether lineae are active today – and whether they could be tied to recent or ongoing devolatilization on Mercury. Our analysis presents several arguments for a direct link between lineae formation and devolatilization: 1) lineae appear to feature a blue spectral slope, like hollows, 2) lineae largely source from hollows and hollow-like features, 3) lineae are predominantly hosted by small, young impact craters that penetrated volcanic deposits, i.e., in a geologic context that facilitates (vertical and lateral) access to subsurface volatiles, 4) lineae tend to cluster on equator-facing slopes, 5) lineae appear to be hosted by terrain with slightly higher (modelled) bi-annual peak temperatures at the surface and at shallow depth, and 6) several lineae occur on shallow slopes well below the angle of repose of dry regolith, suggesting the presence of volatiles as a fluidizing agent (more details are presented in [1]). We do not observe any lineae activity between 2011 and 2015, such as changed or newly formed lineae, implying that lineae activity occurs below MESSENGER’s spatial resolution and/or on timescales longer than ~4 years. Devolatilization-driven lineae activity is a hypothesis that will be scrutinized by the ESA/JAXA (European Space Agency, Japanese Aerospace Exploration Agency) BepiColombo spacecraft and the SIMBIO-SYS instrument suite (Spectrometer and Imaging for MPO BepiColombo Integrated Observatory SYStem) that are expected to initiate their science investigations in early 2027.

[1] Bickel et al. (2026). Slope lineae as potential indicators of recent volatile loss on Mercury. Communications Earth & Environment (in press).

How to cite: Bickel, V. T., Munaretto, G., Bertoli, S., Cremonese, G., Cambianica, P., and Vergara Sassarini, N. A.: Slope Lineae as Potential Geologic Markers of Recent Devolatilization on Mercury, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12154, https://doi.org/10.5194/egusphere-egu26-12154, 2026.

Mafic eruptions and their associated lava fountains are a widespread form of volcanism on both Earth and other planets. These eruptions typically produce scoria and spatter cones, or hybrids of the two, and both the characteristics of the associated tephra blanket and the morphology of the pyroclastic cone can forensically provide quantitative information about the eruption conditions. However, the morphology of a pyroclastic cone results from a complex interplay between syn-eruptive processes (e.g., volume of magma erupted, grain size of pyroclasts produced, syn-eruptive wind) and post-formation erosional processes. Thus, to quantitatively use cone geomorphology to inform on volcanic processes, the contribution of each of these factors must be disentangled. Specifically, here, we focus on the effect that atmospheric winds have at the time of the eruption in controlling the resultant cone morphology. We investigate Volcán del Cuervo, a pyroclastic cone in Lanzarote that has a complex morphology consisting of a distinct, elongated shape, with a second accumulation of pyroclastic material adjacent to the main crater. Here, we use an unnamed aerial vehicle to acquire a high-resolution, photogrammetrically derived digital elevation model (DEM). This DEM allows us to quantify the cone morphology and the precise location of the associated pyroclastic deposits. Samples were collected and associated grain size and density measurements were performed to characterise the pyroclastic material constituting the cone. Together, these data were then used in a ballistic trajectory model to constrain the critical wind and eruptive conditions required to form a secondary cone. Through transplanetary analogies, we conclude that secondary cone formation by this mechanism may bias remotely sensed detections of eruptive centres on planetary surfaces. Misinterpretation of these cones as separate eruptive vents would lead to an overestimation of past volcanism. Correct identification of secondary cones can instead provide direct constrains on eruption dynamics and past atmospheric conditions, including prevailing wind directions—an aspect that is particularly important in planetary environments where direct field validation remains unfeasible.

How to cite: Jones, T. J. and Pieterek, B.: Secondary pyroclastic cones created by syn-eruptive wind , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13591, https://doi.org/10.5194/egusphere-egu26-13591, 2026.

Diverse aeolian bedforms, including dunes, megaripples, and ripples, are migrating across the surface of Mars today, as driven by seasonally variable winds. While long-term sand flux and their regional boundary conditions have been well constrained for many dune fields, an understanding of annual sand transport variability (or consistency) is lacking. Here we provide a decadal-scale analysis of migration patterns for Martian aeolian dune systems and test the hypothesis that global dust storm (GDS)-related winds can influence bedform sediment fluxes.

Annual migration was assessed at select sites in High Resolution Imaging Science Experiment (HiRISE) orthoimages (0.25–1-m/pix) and digital terrain models. Displacements were recorded by manually mapping polylines along the dune crests in GIS over 3-8 Mars years’ worth of images. Sand fluxes were computed using slipface heights from the HiRISE topography, along with dune migration estimates – see Urso et al. 2017; Chojnacki et al. 2024. A total of 20 dune fields were analyzed from 85°N-45°S for Mars years (MY) 28-36, where sites were chosen based on data availability and long-term migration trends.

Migration rates for dunes ranged between 0.3-1.2-m/Earth year, with dune median heights of 6-17-m. Whereas median sand fluxes for sites ranged between 1-10-m³/m/yr over decadal-scale time periods, annual measurements may vary by an order of magnitude. The north polar erg dunes yield the highest rates despite being largely frozen and immobile during the northern autumn, winter, and spring. Here, the seasonal cap thickness and springtime defrost timing dictate how long winds can transport sand. There were notable sand flux maxima over the MY28-29 timestep and minima in MY34-35. The most notable events during these periods were the MY28 and MY34 global dust storms, which impacted the polar vortex, temperatures, and CO₂ ice deposition. MARCI and HiRISE image mapping demonstrated that MY29 (early defrost) and MY35 (late) were endmembers in terms of spring defrosting. These events were attributed to the observed sand flux heterogeneity for some polar dune fields - see Chojnacki et al., 2024.

Equatorial or tropical latitude sites also showed significant deviations of sand transport rates, including during GDS years. Five dune fields showed reduced sand fluxes (33-49%) during the 2018/MY34 (~L_s 180-240°) GDS, relative to the prior year’s measurements. This reduction of nominal sand transport may be due to the depressed daytime surface temperatures or misaligned storm track directions (relative to nominal dune-forming winds) during the 2018 GDS, which were reported in the literature. In contrast, four dune fields were observed with increased fluxes (16-39%) in that GDS year. Elevated transport rates may relate to the alignment of dunes with dust storm corridors that experienced elevated wind shear or more localized factors. Finally, three sites showed no significant deviations in annual measurements, suggesting some bedforms may be in steady state in terms of sand transport. Climate factors such as global dust storms, seasonal ice cycles, and temperature variability appear to have a crucial role in sand availability and transport for Martian dunes; these factors demonstrate the complex interplay of boundary conditions on Mars.

How to cite: Chojnacki, M., Vaz, D., and Silvestro, S.: Interannual variability of sand dune fluxes and the influence of dust storms across Mars, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14513, https://doi.org/10.5194/egusphere-egu26-14513, 2026.

How to cite: Perissutti, D., Marchioli, C., and Soldati, A.: Numerical assessment of celerity scaling laws for ice ripples in turbulent shear flows, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15361, https://doi.org/10.5194/egusphere-egu26-15361, 2026.

Past studies of Martian-analogue landscapes in Antarctica have focused on the Dry Valleys [e.g., 1-3] with the goal of understanding the drivers and potential evolution of geomorphic features in predominantly “cold and dry” conditions. Here we present a new study of a Martian analogue-landscape from the seldom studied Schirmacher Oasis (SO, 70°45′30″S 11°38′40″E) which contains landlocked lakes, polygonal patterns attributed to seasonal thermal contraction and ice wedging, in addition to chloride surface deposits, and even desiccation features associated with the seasonal and long-term drying of the land-locked lakes [e.g, 4, 5]. The features of SO have been observed on Mars, including in terrains that have been dated to Early Mars (The Noachian Period, more than 3.6 Gya).

 We investigated a number of land locked lakes using drone surveys, onsite characterization, and sample collection (Figure. 1). Preliminary results indicate that Schirmacher Oasis indeed provides a potential analogy for specific terrain on Mars, namely those associated with chloride deposits in lacustrine setting. Specifically, we propose that at least a subset of these terrains on Mars may have experienced a similar evolutionary history to that observed in SO; a fluvial, lacustrine and periglacial activity in a previously glaciated area. Studying such regions could help provide new insights into the geological and climatic evolution of Mars, particularly on regional scale, and in periods of transient warming under prevalent cold/icy conditions.

Figure 1: [Top] Geomorphological map of SO adapted from [6]. The legend has been slightly modified to highlight only a few selected units that are of relevance to this study. [Bottom] Satellite view of SO from Google Earth showing the sites visited and sampled in this study.

Acknowledgments: This work was carried out under an MOU between the Indian National Center for Polar and Ocean Research (NCPOR) and the Emirates Polar Program (EPP). The scope of work and collected materials were approved under the research permit MoES/CAG-EP/2025/45-ISEAlP1/23 from the Indian Government’s Ministry of Earth Sciences in full compliance with the Antarctic Treaty. We are deeply indebted to the support throughout from NCPOR under the guidance of Dr. Thamban Meloth, including all logistical support before travel and “on the ground” by the NCPOR team and Goa and at Maitri Station.

References: [1] Marchant, D. R., & Head, J. W. (2007). Icarus, 192(1), 187–222. [2] Tamppari LK, et al. (2012). Antarctic Science. 2012;24(3):211-228.  [3] Heldmann, J. L. et al. (2013). Planetary and Space Science 85, 53-58. [4] Phartiyal, B., et al. (2011). Quaternary International 235,  128–136. [5] Dharwadkar, A., et al. (2018). Polar Science 18, 57–62. [7] Geological Survey of India (2006). Retrieved from: https://ncpor.res.in/files/40 Antarctic Exp/Schirmacher Oasis map.pdf. 

How to cite: El-Maarry, M. R., Aldhanhani, O., Ray, Y., and Alsuwaidi, A.: Schirmacher Oasis, Antarctica: An Earth Analog for Glaciofluvial Landforms and Process on Early Mars?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15988, https://doi.org/10.5194/egusphere-egu26-15988, 2026.

Aeolian megaripples develop on bimodal sands and are stabilized by an armoring layer enriched in coarse grains that developed on the crest. While size-selective transport is central to the segregation mechanism involved in megaripple formation, recent field observations indicate that shape segregation may also contribute to megaripple formation (Saban et al, Geosci. Lett., 2025). Here, we quantify the shape contrast between fine and coarse fractions of megaripples across multiple sites worldwide and investigate the physical mechanism that may explain it. Additionally, we investigate how ripple formation is affected by shape segregation through controlled wind tunnel experiments.

We analyzed samples from megaripple crests at multiple sites. Each sample was divided into sub-samples of fine fraction (<355µm) and a coarse fraction (>710µm), which represent the bimodal grain size distribution (GSD) of all the samples. Grain shape was quantified using a Circularity index (isoperimetric quotient), computed from a 2D projected grain outline derived from microscopy images. Grain outlines were produced by automated segmentation and were manually validated to ensure accuracy. Mineralogical composition and GSD were also measured and used as proxies for mechanical durability and abrasion history contrasts between the size fractions.

Across most sites, the coarse fraction is more angular (less circular) than the fine fraction, indicating a robust shape contrast between size fractions. To explain this pattern, we used a physically motivated combined index that accounts for the size contrast and the quartz contrast between the fine and coarse fractions. Sites where the fine grains are both relatively finer and more quartz-rich compared to the coarse fraction show a stronger shape contrast (i.e., fines are more circular). This suggests that abrasion history and mechanical durability influence grain shape.

Finally, we designed a wind tunnel experiment to isolate the role of shape segregation in the formation of nascent megaripple. We used mixtures of angular natural sand and spherical glass beads with the same grain size. These mixtures were subjected to wind above the fluid threshold until ripple formation. Spatial distribution analysis of grain shape at the end of the experiments reveals clear sorting patterns, driven solely by shape segregation, where angular grains accumulate on the crest and form an armoring-like layer.

How to cite: saban, L., Katra, I., and Yizhaq, H.: Beyond Size Sorting - Shape segregation in aeolian megaripple, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18079, https://doi.org/10.5194/egusphere-egu26-18079, 2026.

Glacier-like forms (GLFs) are one subtype of glacial features found on the Martian surface. They are located within the mid-latitudes of Mars (30-60 degrees) in both hemispheres. These features having formed within the Amazonian period during a period of higher obliquity than Mars' is at today which allowed for the preferential accumulation of icy material in the mid-latitudes. While previous studies have investigated the geographic controls on GLF formation, their former extent, and their former dynamics (Souness, et. al., 2012; Brough, et. al. 2016, 2019), the boundary conditions under which GLFs formed remain poorly constrained, particularly on a local-scale.

Our primary aim is to improve our understanding of how Martian GLFs formed and evolved with respect to their climactic and geomorphological setting using terrestrial rock glaciers as analogues. As there is still ongoing debate as to the formation dynamics of rock glaciers on Earth, be they permafrost-derived or derived from debris-covered glaciers, with the issue being that both start points can adequately describe the end-state of palaeo rock glaciers, we need to take an approach which acknowledges this issue of equifinality. Bayesian inversion is one such method that can do this. We start with the assumption that these GLFs represent permafrost-derived ice bodies where ground-temperature is a key boundary-condition for their formation. With this method, we use observed glacier geomorphology to reconstruct the former extent, volume, and thickness of the GLF to compute a posterior probability distribution for ground temperatures that are physically consistent with the reconstructed geometry of the palaeo glacier. We also consider near-surface air temperature as a secondary factor in accumulation feasibility. 

Here we present our ongoing work in this effort. We manually demarcated the geomorphological constraints of multiple GLFs on Mars within GIS software based on identifiable geomorphology within the orthorectified imagery that mark the former maximum extent of the glacier, and extract morphometric data using the georeferenced HiRISE DEM. We then used the perfect-plasticity approximation to reconstruct palaeo ice-thicknesses and volume of the palaeo glacier. These morphometrics are then compared with modelled outputs for glacier deformation, employing Bayesian logic to constrain a boundary range of long-term mean ground temperature that would be compatible to produce the reconstructed glacier morphology. We also investigate several terrestrial rock glaciers in order to assess the accuracy and validity of our approach against measurable analogue examples, which further enables us to compare the dynamics of terrestrial and Martian glaciers.

References:

Brough, Stephen, Bryn Hubbard, and Alun Hubbard. 2016. “Former Extent of Glacier-Like Forms on Mars.”, Icarus 274 (August): 37–49. https://doi.org/10.1016/j.icarus.2016.03.006.

Brough, S., Hubbard, B., & Hubbard, A. (2019, 02). Area and volume of mid latitude glacier-like forms on mars. Earth and Planetary Science Letters, 507 , 10–20. Retrieved from https://linkinghub.elsevier.com/retrieve/pii/S0012821X18306903 doi: 10.1016/j.epsl.2018.11.031

Souness, Colin, Bryn Hubbard, Ralph E. Milliken, and Duncan Quincey. 2012. “An Inventory and Population-Scale Analysis of Martian Glacier-Like Forms.” Icarus 217 (1): 243–55. https://doi.org/10.1016/j.icarus.2011.10.020.

How to cite: Jones, M., Sam, L., Mullan, D., Rea, B., and Bhardwaj, A.: Investigating the formation conditions of glacier-like forms using Bayesian inversion. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20367, https://doi.org/10.5194/egusphere-egu26-20367, 2026.

Since the robust performance of Long Short-Term Memory (LSTM) networks was established, their physics-awareness and interpretability have become central topics in hydrology. Seminal works (e.g., Lees et al. (2022)) have argued that LSTM internal states spontaneously capture hydrological concepts, and suggested that cell states can represent soil moisture dynamics despite not being explicitly trained on such data. Conversely, more recent studies (e.g., Fuente et al. (2024)) demonstrated that mathematical equifinality causes non-unique LSTM representations with different initialisations.

In this work, we report an arguably more systematic "bug" in the software environment that causes instability in internal states. We initially aimed to investigate how internal states behave differently when trained with or without historical observation data. We encountered this issue while reassembling a computational stack and attempting to replicate the initial results, as the original Docker environment was not preserved. While random seeds have been indicated to lead to different internal state trajectories, we found the computational backend (e.g., changing CUDA versions, PyTorch releases, or dependent libraries) also produces them. These are the findings:

• In gauged catchments: Discharge predictions remained stable (in one catchment, NSE was 0.88 ± 0.01) across computational environments, yet the internal temporal variations (e.g., silhouette, mean, and std of cell states) fluctuated noticeably.
• In pseudo-ungauged scenarios: The prediction performance itself became more reliant on the computational environment (in the same catchment, NSE dropped to 0.31 ± 0.15), yet the internal temporal variations of the cell states fluctuated only as much as they did during the gauged scenario.

These findings suggests that instability in the computational environment poses not only a risk of altering interpretability in training (by altering internal states) but also casts doubt on reliability in extrapolation (by altering outputs).

It is worth mentioning that we confirmed this is not a replicability issue; completely identical cell states and predictions are produced when the computational environment, seeds, and training data are held constant. We argue that such stability must be established as a standard benchmark before assigning physical meaning to deep learning internals.

How to cite: Nagumo, R., Woods, R., and Rico-Ramirez, M.: The Unreliable Narrator: LSTM Internal States Fluctuate with Software Environments Despite Robust Predictions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1897, https://doi.org/10.5194/egusphere-egu26-1897, 2026.

Moments or periods of struggle not only propel scientists forward, but sharing these experiences can also provide valuable lessons for others. Indeed, the current bias towards only publishing ‘positive’ results arguably impedes scientific progress as mistakes that are not learnt from are simply repeated. Here we present a new article type in EGU journals covering LESSONS learnt to help overcome this publishing bias. LESSONS articles describe the Limitations, Errors, Surprises, Shortcomings, and Opportunities for New Science emerging from the scientific process, including non-confirmatory and null results. Unforeseen complications in investigations, plausible methods that failed, and technical issues are also in scope. LESSONS thus fit the content of the BUGS session and can provide an outlet for articles based on session contributions. Importantly, a LESSONS Report will offer a substantial, valuable insight. LESSONS Reports are typically short (1,000-2,000 words) to help lower the barrier to journal publication, whilst LESSONS Posts (not peer-reviewed, but with a DOI on EGUsphere) can be as short as 500 words to allow early-stage reporting. LESSONS aim to destigmatise limitations, errors, surprises and shortcomings and to add these to the published literature as opportunities for new science – we invite you to share your LESSONS learnt.

Finally, a big thank you from this paper’s ‘core’ writing team to the wider group who have helped shape the LESSONS idea since EGU GA in 2025, including PubCom and in particular its Chair Barbara Ervens.

How to cite: Hillier, J., Proske, U., Gaillard, S., Blume, T., and Queiroz Alves, E.: New EGU Manuscript Types: Limitations, Errors, Surprises, and Shortcomings as Opportunities for New Science (LESSONS), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2771, https://doi.org/10.5194/egusphere-egu26-2771, 2026.

Photocatalysis is frequently presented in the literature as a straightforward route toward efficient degradation of pollutants, provided that the “right” material is selected. Layered double hydroxides (LDH) are often highlighted as promising photocatalysts due to their tunable composition and reported activity in dye degradation. Motivated by these claims, this study evaluated LDH as mineral analogs for photocatalytic water treatment, ultimately uncovering a series of unexpected limitations, methodological pitfalls, and productive surprises.

In the first stage, Zn/Cr, Co/Cr, Cu/Cr, and Ni/Cr LDHs were synthesized and tested for photocatalytic degradation of methylene blue (0.02 mM) and Acid Blue Dye 129 (0.3 mM). Contrary to expectations,¹ photocatalytic performance was consistently low. After one hour of irradiation, concentration losses attributable to photocatalysis did not exceed 15%, while most dye removal resulted from adsorption. Despite extensive efforts to optimize synthesis protocols, catalyst composition, and experimental conditions, this discrepancy with previously published studies could not be resolved.

To overcome limitations related to particle dispersion, surface accessibility, and charge-carrier separation, a second strategy was pursued by incorporating clay minerals as supports.² Zn/Cr LDH, identified as the most active composition in preliminary tests, was coprecipitated with kaolinite, halloysite, and montmorillonite. Experiments with methylene blue (0.1 mM) and Acid Blue 129 (0.3 mM) demonstrated enhanced adsorption capacities. However, photocatalytic degradation efficiencies remained poor, typically below 10% after one hour, indicating that apparent performance gains were largely adsorption-driven rather than photochemical.

This failure proved to be a turning point. Instead of abandoning LDH entirely, they were combined with graphitic carbon nitride (GCN) to form a heterostructure.³ This approach resulted in a dramatic improvement: after optimization of the synthesis protocol, 99.5% of 1 ppm estrone was degraded within one hour.⁴ Further modifications were explored by introducing Cu, Fe, and Ag into the LDH/GCN system. While Cu and Fe suppressed photocatalytic activity, silver, at an optimized loading, reduced estrone concentrations below the detection limit within 40 minutes.⁵

This contribution presents a full experimental arc - from promising hypotheses that failed, through misleading adsorption-driven “successes,” to an ultimately effective but non-intuitive solution - highlighting the value of negative results and surprises as drivers of scientific progress.

This research was funded by the AGH University of Krakow, grant number 16.16.140.315.

Literature:

1            N. Baliarsingh, K. M. Parida and G. C. Pradhan, Ind. Eng. Chem. Res., 2014, 53, 3834–3841.

2            A. Í. S. Morais, W. V. Oliveira, V. V. De Oliveira, L. M. C. Honorio, F. P. Araujo, R. D. S. Bezerra, P. B. A. Fechine, B. C. Viana, M. B. Furtini,
              E. C. Silva-Filho and J. A. Osajima, Journal of Environmental Chemical Engineering, 2019, 7, 103431.

3            B. Song, Z. Zeng, G. Zeng, J. Gong, R. Xiao, S. Ye, M. Chen, C. Lai, P. Xu and X. Tang, Advances in Colloid and Interface Science, 2019, 272, 101999.

4            A. Jędras, J. Matusik, E. Dhanaraman, Y.-P. Fu and G. Cempura, Langmuir, 2024, 40, 18163–18175.

5            A. Jędras, J. Matusik, J. Kuncewicz and K. Sobańska, Catal. Sci. Technol., 2025, 15, 6792–6804.

How to cite: Jędras, A. and Matusik, J.: False Starts and Silver Linings: A Photocatalytic Journey with Layered Double Hydroxides, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3077, https://doi.org/10.5194/egusphere-egu26-3077, 2026.

BUGS can arise in individual research projects, but also at the level of communities of researchers, leading to shifts in the scientific consensus.  These community-level BUGS typically arise from observations that are surprising to (or previously overlooked by) substantial fractions of the research community.  In this presentation, we summarize several community-level BUGS in our field: specifically, key surprises that have transformed the hydrological community's understanding of hillslope and catchment processes in recent decades.  

Here are some examples.  (1) Students used to learn (and some still do today) that storm runoff is dominated by overland flow.  But stable isotope tracers have convincingly shown instead that even during storm peaks, streamflow is composed mostly of water that has been stored in the landscape for weeks, months, or years.  (2) Maps, and most hydrological theories, have typically depicted streams as fixed features of the landscape.  But field mapping studies have shown that stream networks are surprisingly dynamic, with up to 80% of stream channels going dry sometime during the year.  (3) Textbooks have traditionally represented catchment storage as a well-mixed box.  But tracer time series show fractal scaling that cannot be generated by well-mixed boxes, forcing a re-think of our conceptualization of subsurface storage and mixing.  (4) Waters stored in aquifers, and the waters that drain from them, have traditionally been assumed to share the same age.  But tracers show that waters draining from aquifers are often much younger than the groundwaters that are left behind, and this was subsequently shown to be an inevitable result of aquifer heterogeneity. 

Several examples like these, and their implications, will be briefly discussed, with an eye to the question: how can we maximize the chances for future instructive surprises?

How to cite: Kirchner, J., Benettin, P., and van Meerveld, I.: Instructive surprises in the hydrological functioning of landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4074, https://doi.org/10.5194/egusphere-egu26-4074, 2026.

Coming from geosciences, we hopefully know what we want to do. Coming from numerics, however, we often know quite well what we are able to do and look for a way to sell it to the community. A few years ago, deep-learning techniques brought new life into the glaciology community. These approaches  allowed for simulations of glacier dynamics at an unprecedented computational performance and motivated several researchers to tackle the numerous open questions about past and present glacier dynamics, particularly in alpine regions. From another point of view, however, it was also tempting to demonstrate that the human brain is still more powerful than artificial intelligence by developing a new classical numerical scheme that can compete with deep-learning techniques concerning its efficiency.

Starting point was, of course, the simplest approximation to the full 3-D Stokes equations, the so-called shallow ice approximation (SIA). Progress was fast and the numerical performance was even better than expected. The new numerical scheme enabled simulations with spatial resolutions of 25 m on a desktop PC, while previous schemes did not reach simulations below a few hundred meters.

However, the enthusiasm pushed the known limitations of the SIA a bit out of sight. Physically, the approximation is quite bad on rugged terrain, particularly in narrow valleys. So the previous computational limitations have been replaced by physical limitations since high resolutions are particularly useful for rugged topographies. In other words, a shabby house has a really good roof now.

What are the options in such a situation?

• Accept that there is no free lunch and avoid contact to the glacialogy community in the future.
• Continue the endless discussion about the reviewers' opinion that a spatial resolution of 1 km is better than 25 m.
• Find a real-world data set that matches the results of the model and helps to talk the problems away.
• Keep the roof and build a new house beneath. Practically, this would be developing a new approximation to the full 3-D Stokes equations that is compatible to the numerical scheme and reaches an accuracy similar to those of the existing approximations.
• Take the roof and put it on one of the existing solid houses. Practically, this would be an extension of the numerical scheme towards more complicated systems of differential equations. Unfortunately, efficient numerical schemes are typically very specific. So the roof will not fit easily and it might leak.

The story is open-ended, but there will be at least a preliminary answer in the presentation.

How to cite: Hergarten, S.: How useful is a new roof on a shabby house? An example from glacier modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4196, https://doi.org/10.5194/egusphere-egu26-4196, 2026.

“Show your working!” – is the universal phrase drilled into science and maths students to show a clear demonstration of the steps and thought processes used to reach a solution (and to be awarded full marks on the exam). 

Beyond the classroom, “show your working” becomes the methods section on every scientific paper, and is critical for the transparency and replicability of the study. However, what happens if parts of the method are considered assumed knowledge, or cut in the interests of a word count? 

An inability to fully replicate the results of a study became the unexpected glitch at the start of my PhD. Eager to familiarise myself with global climate model datasets, I set out to replicate the results of a widely cited paper which calculates the equilibrium climate sensitivity (ECS) across 27 climate models. The ECS is the theoretical global mean temperature response to a doubling of atmospheric CO₂ relative to preindustrial levels. A commonly used method to calculate the ECS is to apply an ordinary least squares regression to global annual mean temperature and radiative flux anomalies. 

Despite the simplicity of a linear regression between two variables, we obtained ECS estimates for some climate models that differed from those reported in the original study, even though we followed the described methodology. However, the methodology provided only limited detail on how the raw climate model output – available at regional and monthly scales – was processed to obtain global annual mean anomalies. Differences in these intermediate processing steps can, in turn, lead to differences in ECS estimates.

Limited reporting of data-processing steps is common in the ECS literature. Whether these steps are considered assumed knowledge or deemed too simple to warrant explicit description, we demonstrate that, for some models, they can materially affect the resulting ECS estimate. While the primary aim of our study is to recommend a standardised data-processing pathway for ECS calculations, a secondary aim is to highlight the lack of transparency in key methodological details across the literature. A central takeaway is the importance of clearly documenting all processing steps – effectively, to “show your working” – and to emphasise the critical role of a detailed methods section.

How to cite: Zehrung, A., King, A., Nicholls, Z., Zelinka, M., and Meinshausen, M.: The importance of describing simple methods in climate sensitivity literature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4587, https://doi.org/10.5194/egusphere-egu26-4587, 2026.

Observation of atmospheric constituents and processes is not easy. As atmospheric chemists, we use sensitive equipment, for example mass spectrometers, that we often set up in a (remote) location or on a moving platform for a few-weeks campaign to make in-situ observations. All this with the goal of explaining more and more atmospheric processes, and to verify and improve atmospheric models. However, glitches can happen anywhere in an experiment, be it in the experimental design, setup, or instrumental performance. Thus, complete data coverage during such a campaign is not always a given, resulting in gaps in (published) datasets. And the issue with air is that you can never go back and measure the exact same air again. Here, I would like to share some stories behind such gaps, and what we learned from them. This presentation aims to encourage early career researchers who might be struggling with feelings of failure when bugs, blunders and glitches happen in their experiments - you are not alone! I will share what we learned from these setbacks and how each of them improved our experimental approaches.

How to cite: Pfannerstill, E. Y.: Why are there gaps in your measurements? Sharing the stories behind the missing datapoints, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5494, https://doi.org/10.5194/egusphere-egu26-5494, 2026.

Over a 24-year research period, three successive experimental investigations led to three publications, each of which falsified the author’s preceding hypothesis and proposed a revised conceptual framework. Despite an initial confidence in having identified definitive solutions, subsequent experimental evidence consistently demonstrated the limitations and inaccuracies of earlier interpretations. This iterative process ultimately revealed that samples, in particular geological reference materials, sharing identical petrographic or mineralogical descriptions are not necessarily chemically equivalent and can exhibit markedly different behaviors during chemical digestion procedures. These findings underscore the critical importance of continuous hypothesis testing, self-falsification, and experimental verification in scientific research, particularly when working with reference materials assumed to be identical. I will be presenting data on the analysis of platinum group elements (PGE) and osmium isotopes in geological reference materials (chromitites, ultramafic rocks and basalts), which demonstrates the need for challenging matrices for method validation. 

How to cite: Meisel, T. C.: Self-falsification as a driver of scientific progress: Insights from long-term experimental research, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5771, https://doi.org/10.5194/egusphere-egu26-5771, 2026.

In atmospheric sciences, a central tool to test hypotheses are numerical models, which aim to represent (part of) our environment. One such model is the weather and climate model ICON [1], which solves the Navier-Stokes equation for capturing the dynamics and parameterizes subgrid-scale processes, such as radiation, cloud microphysics, and aerosol processes. Specifically, for the latter exists the so-called Hamburg Aerosol Module (HAM [2]), which is coupled to ICON [3] and predicts the evolution of aerosol populations using two moments (mass mixing ratio and number concentration). The high complexity of aerosols is reflected in the number of aerosol species (total of 5), number of modes (total of 4), and their mixing state and solubility. The module calculates aerosol composition and number concentration, their optical properties, their sources and sinks, and their interactions with clouds via microphysical processes. Aerosol emissions are sector-specific and based on global emission inventories or dynamically computed.

Within our work, we stumbled upon an interesting pattern occurrence in our simulations upon changing/turning off single emission sectors. If we, e.g., removed black carbon from aircraft emissions, the strongest changes emerged over the African continent, which is not the region where we were expecting to see the strongest response. Further investigations revealed that this pattern emerges independently of the emission sector as well as species, confirming our suspicion that we are facing a bug within HAM. Here, we want to present how we approached the challenge of identifying and tackling a bug within a complex module with several thousand lines of code.

[1] G. Zängl, D. Reinert, P. Ripodas, and M. Baldauf, “The ICON (ICOsahedral Non-hydrostatic) modelling framework of DWD and MPI-M: Description of the non-hydrostatic dynamical core,” Quarterly Journal of the Royal Meteorological Society, vol. 141, no. 687, pp. 563–579, 2015, ISSN: 1477-870X. DOI: 10.1002/qj.2378

[2] P. Stier, J. Feichter, S. Kinne, S. Kloster, E. Vignati, J. Wilson, L. Ganzeveld, I. Tegen, M. Werner, Y. Balkanski, M. Schulz, O. Boucher, A. Minikin, and A. Petzold, “The aerosol-climate model ECHAM5-HAM,” Atmospheric Chemistry and Physics, 2005. DOI: 10.5194/acp-5-1125-2005

[3] M. Salzmann, S. Ferrachat, C. Tully, S. M¨ unch, D. Watson-Parris, D. Neubauer, C. Siegenthaler-Le Drian, S. Rast, B. Heinold, T. Crueger, R. Brokopf, J. Mülmenstädt, J. Quaas, H. Wan, K. Zhang, U. Lohmann, P. Stier, and I. Tegen, “The Global Atmosphere-aerosol Model ICON-A-HAM2.3–Initial Model Evaluation and Effects of Radiation Balance Tuning on Aerosol Optical Thickness,” Journal of Advances in Modeling Earth Systems, vol. 14, no. 4,e2021MS002699, 2022, ISSN: 1942-2466. DOI: 10.1029/2021MS002699

How to cite: Omanovic, N., Ferrachat, S., and Lohmann, U.: Back to square one (again and again): Finding a bug in a complex global atmospheric model  , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6794, https://doi.org/10.5194/egusphere-egu26-6794, 2026.

In situ cloud measurements are essential for understanding atmospheric processes and establishing a reliable ground truth. Obtaining these data is rarely straightforward. Challenges range from accessing clouds in the first place to ensuring that the instrument or environment does not bias the sample. This contribution explores several blunders and unexpected glitches encountered over fifteen years of field campaigns.

I will share stories of mountain top observations where blowing snow was measured instead of cloud ice crystals and the ambitious but failed attempt to use motorized paragliders for sampling. I also reflect on winter campaigns where the primary obstacles were flooding and mud rather than cold and snow. While these experiences were often frustrating, they frequently yielded useful data or led to new insights. One such example is the realization that drone icing is not just a crash risk but can also serve as a method for measuring liquid water content. By highlighting these setbacks and the successful data that emerged despite them, I aim to foster a discussion on the value of trial and error and persistence in atmospheric physics.

How to cite: Henneberger, J.: How Not to Measure a Cloud: Lessons from Fifteen Years of Fieldwork Failures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8228, https://doi.org/10.5194/egusphere-egu26-8228, 2026.

Forests are powerful climate regulators: Their CO₂ uptake provides a global biogeochemical cooling effect, and in the tropics, this cooling is further strengthened by evapotranspiration. Given that temperature-related mortality is a relevant global health burden, which is expected to increase under climate change, we set out to test what we thought was a promising hypothesis: Can forests reduce human temperature-related mortality from climate change? 

To test this, we used simulated temperature changes to reforestation from six different Earth System Models (ESMs) under a future high-emission scenario, and paired them with age-specific population data and three methodologically different temperature-mortality frameworks (Cromar et al. 2022, Lee et al. 2019, and Carleton et al. 2022). We expected to find a plausible range of temperature-related mortality outcomes attributable to global future forests conservation efforts.

Instead, our idea ran head-first into a messy reality. Firstly, rather than showing a clear consensus, the ESMs produced a wide range of temperature responses to reforestation, varying both in magnitude and sign. This is likely due to the albedo effect, varying climatological tree cover and land use processes implemented by the models, in addition to internal variability which we could not reduce due to the existence of only one ensemble member per model. Consequently, the models disagreed in many regions on whether global forest conservation and reforestation would increase or decrease temperature by the end of the century.

The uncertainties deepened when we incorporated the mortality data. Mortality estimates varied by up to a factor of 10 depending on the ESM and mortality framework used. Therefore, in the end, the models could not even agree on whether forests increased or decreased temperature-related mortality. We found ourselves with a pipeline that amplified uncertainties of both the ESM and mortality datasets.

For now, the question remains wide open: Do trees save us from temperature-related deaths in a warming world, and if so, by how much?

* The first two authors contributed equally to this work.

How to cite: Hohmuth, N., Fahrenbach (presenting), N. L. S., Zou (presenting), Y., Reek, J., Specker, F., Crowther, T., and Zohner, C. M.: Do trees save lives under climate change? It’s complicated , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8359, https://doi.org/10.5194/egusphere-egu26-8359, 2026.

Hydrological modelling has long been shaped by a steady drive toward ever more sophisticated models. In the era of machine learning, this race has turned into a relentless pursuit of complexity: deeper networks and ever more elaborate architectures that often feel outdated by the time the ink on the paper is dry. Motivated by a genuine belief in methodological progress, I, like many others, spent considerable effort exploring this direction, driven by the assumption that finding the “right” architecture or model would inevitably lead to better performance. This talk is a reflection on that journey; you could say my own Leidensweg. Over several years, together with excellent collaborators, I explored a wide range of state-of-the-art deep-learning approaches for rainfall–runoff modelling and other hydrological modelling challenges. Yet, regardless of the architecture or training strategy, I repeatedly encountered the same performance ceiling. In parallel, the literature appeared to tell a different story, with “new” models regularly claiming improvements over established baselines. A closer inspection, however, revealed that rigorous and standardized benchmarking is far from common practice in hydrology, making it difficult to disentangle genuine progress from artefacts of experimental design. What initially felt like a failure to improve my models turned out to be a confrontation with reality. The limiting factor was not the architecture, but the problem itself. We have reached a point where predictive skill is increasingly bounded by the information content of our benchmark datasets and maybe more importantly by the way we frame our modelling challenges, rather than by model design. Like many others, I have come to believe that if we want to move beyond the current performance plateau, the next breakthroughs are unlikely to come from ever more complex models alone. Instead, as a community, we need well-designed model challenges, better benchmarks, and datasets that meaningfully expand the information available to our models to make model comparisons more informative.

How to cite: Loritz, R., Dolich, A., and Heudorfer, B.: The empty mine: Why better tools do not help you find new diamonds, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10401, https://doi.org/10.5194/egusphere-egu26-10401, 2026.

Examining catchment response to precipitation at event scale is useful for understanding how various hydrological systems store and release water. Many of such event scale characteristics, for example event runoff coefficient and event time scale are also important engineering metrics used for design. However, deriving these characteristics requires identification of discrete precipitation-streamflow events from continuous hydrometeorological time series.

Event identification is not at all a trivial task. It becomes even more challenging when working with very large datasets that encompass a wide range of spatial and temporal dynamics. Approaches range from visual expert judgement to baseflow-separation-based methods and objective methods based on the coupled dynamics of precipitation and streamflow. Here, we would like to present our experience in the quest to devise the “ideal” method for large datasets – and trust us, we tried, a lot. We demonstrate that expert-based methods can be seriously flawed simply by changing a few meta parameters, such as the length of displayed periods, baseflow-separation-based methods deliver completely opposite results when different underlying separation methods are selected, and objective methods suddenly fail when dynamics with different temporal scales are simultaneously present.

Ultimately, we realized that finding a one-size-fits-all method was not possible and that compromises had to be made to select sufficiently representative events across large datasets. Therefore, we advocate for pragmatic case-specific evaluation criteria and for transparency in event identification to make study results reproducible and fit for purpose, if not perfect.

How to cite: Tarasova, L. and Astagneau, P.: How NOT to identify streamflow events?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13630, https://doi.org/10.5194/egusphere-egu26-13630, 2026.

A defining attribute of global-storm resolving models is that modelling is replaced by simulation.  In addition to overloading the word “model”  this avails the developer of a much larger variety of tests, and brings about a richer interplay with their intuition.  This has proven helpful in identifying and correcting many mistakes in global-storm resolving models that traditional climate models find difficult to identify, and usually compensate by “tuning.”  It also means that storm-resolving models are built and tested in a fundamentally different way than are traditional climate models. In this talk I will review the development of ICON as a global storm resolving model to illustrate how this feature, of trying to simulate rather than model the climate system, has helped identify a large number of long-standing bugs in code bases inherited from traditional models; how this can support open development; and how sometimes these advantages also prove to be buggy.

How to cite: Stevens, B., Giorgetta, M., and Segura, H.: Buggy benefits of more fundamental climate models, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14148, https://doi.org/10.5194/egusphere-egu26-14148, 2026.

Hydrological and water systems modelling has long been driven by the search for better models. We do so by searching for models or at least parameter combinations that provide the best fit to given observations. We ourselves have contributed to this effort by developing new methods and by publishing diverse case studies. However, we repeatedly find that searching for and finding an optimal model is highly fraught in the presence of unclear signal-to-noise ratios in our observations, of incomplete models and of highly imbalanced databases. We present examples of our own work through which we have realized that achieving optimality was possible but futile unless we give equal consideration to issues of consistency, robustness and problem framing. We argue here that the strong focus on optimality continues to be a hindrance for advancing hydrologic science and for transferring research achievements into practice – probably more so than in other areas of the geosciences.

How to cite: Wagener, T. and Pianosi, F.: The dangerous temptation of optimality in hydrological and water resources modelling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14374, https://doi.org/10.5194/egusphere-egu26-14374, 2026.

Among soil physical analyses, determination of the soil particle-size distribution (PSD) is arguably the most fundamental. The standard methodology combines sieve analysis for sand fractions with sedimentation-based techniques for silt and clay. Established sedimentation methods include the pipette and hydrometer techniques. More recently, the Integral Suspension Pressure (ISP) method has become available, which derives PSD by inverse modeling of the temporal evolution of suspension pressure measured at a fixed depth in a sedimentation cylinder. Since ISP is based on the same physical principles as the pipette and hydrometer methods, their results should, in principle, agree.

The ISP methodology has been implemented in the commercial instrument PARIO (METER Group, Munich). While elegant, the method relies on pressure change measurements with a resolution of 0.1 Pa (equivalent to 0.01 mm of water column). Consequently, the PARIO manual strongly advises avoiding any mechanical disturbance such as thumping, bumping, clapping, vibration, or other shock events. This warning is essentially precautionary, because to date no systematic experimental investigation of such disturbances has been reported.

To explore this issue, we prepared a single 30 g soil sample following standard PSD procedures and subjected it to 26 PARIO repeated measurement runs over a period of five months, each run lasting 12 h. Between runs, the suspension was remixed but otherwise not altered. The first ten runs (over ten days) were conducted without intentional disturbance to establish baseline repeatability. This was followed by eight runs with deliberately imposed and timed disturbances that generated single or repeated vibrations (“rocking and shocking”). After approximately two and five months, we conducted additional sets of five and three undisturbed runs, respectively.

We report how these mechanical disturbances, along with temperature variations during measurement and the time elapsed since sample pre-treatment, affected the derived PSD. The results provide a first quantitative assessment of how fragile—or robust—the ISP method and PARIO system really are when reality refuses to sit perfectly still.

How to cite: Nemes, A. and Durner, W.: Rocking and Shocking the PARIOTM: How Sensitive Is ISP-Based Particle-Size Analysis to Mechanical Disturbance?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14763, https://doi.org/10.5194/egusphere-egu26-14763, 2026.

Predicting soil hydraulic behavior is necessary for the modeling of catchments and agricultural planning, particularly for a country like Norway where only 3% of land is suitable for farming. Soil texture is an important and easily accessible parameter for the prediction of soil hydraulic behavior. However, some Norwegian farmland soils, which formed as glacio-marine sediments and are characterized by a medium texture, have shown the hydraulic behavior of heavy textured soils. Coined by the theory behind well-established sedimentation-enhancing technology used in waste water treatment, we hypothesized that sedimentation under marine conditions may result in specific particle sorting and as a result specific pore system characteristics. To test this, we designed four custom-built devices to produce artificially re-sedimented columns of soil material to help characterize the influence of sedimentation conditions. We successfully produced column samples of the same homogeneous mixture of fine-sand, silt, and clay particles obtained by physically crushing and sieving (< 200 µm) subsoil material collected at the Skuterud catchment in South-East Norway, differing only in sedimentation conditions (deionized water vs 35 g per liter NaCl solution). Then, the inability of standard laboratory methods to measure the saturated hydraulic conductivity of such fine material, led us to “MacGyver” (design and custom-build) two alternative methodologies to measure that property, i.e. i) by adapting a pressure plate extractor for a constant head measurement and ii) by building a 10 m tall pipe-system in a common open area of the office, in order to increase the hydraulic head on the samples. There was a learning curve with both of those methods, but we have found that the salt-water re-sedimented columns were about five times more permeable than the freshwater ones, which was the complete opposite of our expectations. However, an unexpected blunder in the conservation of our samples suggests that our hypothesis should be further explored rather than dismissed. These contributions hint about the mechanisms that may underlie the anomalous hydraulic behaviour of certain Norwegian soils and raise new questions on the formation of marine clays, improving knowledge available for land managers and modellers.

How to cite: Nemes, A., Bazzocchi, P., Weiland, S., and van der Ploeg, M.: Some Norwegian soils behave differently: is it an inheritance from marine sedimentation?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14852, https://doi.org/10.5194/egusphere-egu26-14852, 2026.

“It is in the tentative stage that the affections enter with their blinding influence. Love was long since represented as blind…The moment one has offered an original explanation for a phenomenon which seems satisfactory, that moment affection for his intellectual child springs into existence…To guard against this, the method of multiple working hypotheses is urged. … The effort is to bring up into view every rational explanation of new phenomena, and to develop every tenable hypothesis respecting their cause and history. The investigator thus becomes the parent of a family of hypothesis: and, by his parental relation to all, he is forbidden to fasten his affections unduly upon any one” (Chamberlin, 1890).

The MADE (macro-dispersion) natural-gradient tracer field experiments were conducted more than 35 years ago. It aimed to determine field-scale dispersion parameters based on detailed hydraulic conductivity measurements to support transport simulation. A decade of field experiments produced a 30-year paper trail of modelling studies with no clear resolution of a successful simulation approach for practical use in transport problems.  As a result, accurately simulating contaminant transport in the subsurface remains a formidable challenge in hydrogeology.

What went awry, and why do we often miss the mark?

Herweijer et al. (2026) conducted a ‘back to basics’ review of the original MADE reports and concluded that there are significant inconvenient and unexplored issues that influenced the migration of the tracer plume and or biased observations. These issues include unreliable measurement of hydraulic conductivity, biased tracer concentrations, and underestimation of sedimentological heterogeneity and non-stationarity of the flow field. Many studies simulating the tracer plumes appeared to have ignored, sidestepped, or been unaware of these issues, raising doubts about the validity of the results.

Our analysis shows that there is a persistent drive among researchers to conceptually oversimplify natural complexity to enable testing of single-method modelling, mostly driven by parametric stochastic approaches. Researchers tend to be anchored to a specialised, numerically driven methodology and have difficulty in unearthing highly relevant information from ‘unknown known’ data or applying approaches outside their own specialised scientific sub-discipline. Another important aspect of these ‘unkowns knowns’ is the tendency to accept published data verbatim. Too often, there is no rigorous investigation of the original measurement methods and reporting, and, if need be, additional testing to examine the root cause of data issues.

Following the good old advice of Chamberlin (1890), we used a knowledge framework to systematically assess knowns, unknowns, and associated confidence levels, yielding a set of multi-conceptual models. Based on identified 'unknowns', these multi-models can be tested against reliable 'knowns' such as piezometric data and mass balance calculations.  

Chamberlin, T.C., 1890, The method of multiple working hypotheses. Science 15(366): 92-96. doi:10.1126/science.ns-15.366.92.

Herweijer J.C., S. C Young, P. Hayes, and O. Batelaan, 2026, A multi-conceptual model approach to untangling the MADE experiment, Accepted for Publication in Groundwater.

How to cite: Batelaan, O., Herweijer, J., Young, S., and Hayes, P.: The unknown knowns – the inconvenient knowledge in hydrogeology we do not like to use, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16619, https://doi.org/10.5194/egusphere-egu26-16619, 2026.

Free-slip boundary conditions are routinely used in 3D geodynamic modelling because they reduce computational cost, avoid artificial shear zones at domain edges, and simplify the implementation of large-scale kinematic forcing. However, despite their apparent neutrality, our experiments show that free-slip boundaries systematically generate first-order artefacts that propagate deep into the model interior and can severely distort the interpretation of continental rifting simulations.

Here we present a set of 3D visco-plastic models inspired by the South China Sea (SCS) that were originally designed to study the effect of steady-state thermal inheritance and pluton-controlled crustal weakening. Unexpectedly, in all simulations except those with a very particular inverted rheological profile (POLC), the free-slip boundary on the “Vietnam side” of the domain generated a persistent secondary propagator, producing unrealistic amounts of lithospheric thinning in the southwest corner. This artefact appeared irrespective of crustal rheology, seeding strategy, or the presence of thermal heterogeneities.

We identify three systematic behaviours induced by free-slip boundaries in 3D:
(1) forced rift nucleation at boundary-adjacent thermal gradients,
(2) artificial propagator formation that competes with the intended first-order rifting, and
(3) rotation or shearing of micro-blocks not predicted by tectonic reconstructions.

These artefacts originate from the inability of free-slip boundaries to transmit shear traction, which artificially channels deformation parallel to the boundary when lateral thermal or mechanical contrasts exist. In 3D, unlike in 2D, the combination of oblique extension and boundary-parallel velocity freedom leads to emergent pseudo-transform behaviour that is entirely numerical.

Our results highlight a key negative outcome: free-slip boundaries cannot be assumed neutral in 3D rift models, especially when studying localisation, obliquity, multi-propagator dynamics, or the competition between structural and thermal inheritance. We argue that many published 3D rift models may unknowingly include such artefacts.

How to cite: Le Pourhiet, L.: The Hidden Propagator: How Free-Slip Boundaries Corrupt 3D Simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17373, https://doi.org/10.5194/egusphere-egu26-17373, 2026.

How to cite: Williamson, E., Pritchard, M., Iwi, A., Pepler, S., and Parton, G.: Data Disaster to Data Resilience: Lessons from CEDA’s Data Recovery , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18600, https://doi.org/10.5194/egusphere-egu26-18600, 2026.

Aerosol-cloud interactions remain one of the largest uncertainties in global climate modelling. This uncertainty arises because of the dependence of aerosol-cloud interactions on many tightly coupled atmospheric processes; the non-linear response of clouds to aerosol perturbations across different regimes; and the challenge of extracting robust signals from noisy meteorological observations. The problem is particularly acute in the Arctic, where sparse observational coverage limits model constraints, pristine conditions can lead to unexpected behaviour, and key processes remain poorly understood.

A common way to tackle the challenge of uncertainties arising from aerosol-cloud interactions in climate simulations is to conduct sensitivity experiments using cloud and aerosol microphysics schemes based on different assumptions and parameterisations. By comparing these experiments, key results can be constrained by sampling the range of unavoidable structural uncertainties in the models. Here, we apply this approach to a case study of an extreme, polluted warm air mass in the Arctic that was measured during the MOSAiC Arctic expedition in 2020. We simulated the event in the WRF-Chem-Polar regional climate model both with and without the anthropogenic aerosols from the strong pollution event to study the response of clouds and surface radiative balance. To understand the sensitivity of our results to the choice of model configuration, we tested two distinct, widely-used cloud microphysics schemes.

Initial results showed that the two schemes simulated opposite cloud responses: one predicted a surface cooling from the pollution that was reasonably in line with our expectations of the event, while the other predicted the opposite behaviour in the cloud response and an associated surface warming. These opposing effects seemed to suggest that structural uncertainties in the two schemes relating to clean, Arctic conditions was so strong that it even obscured our ability to understand the overall sign of the surface radiative response to the pollution.

However, since significant model development was required to couple these two cloud microphysics schemes to the aerosol fields in our model, there was another explanation that we couldn’t rule out: a bug in the scheme that was producing the more unexpected results. In this talk, we will explore the challenges of simulating the Arctic climate with a state-of-the-art chemistry-climate model and highlight how examples like this underscore the value of our recent efforts to align our collaborative model development with software engineering principles and Open Science best practices.

How to cite: Lapere, R., Price, R., Marelle, L., Bastien, L., and Thomas, J.: Opposite cloud responses to extreme Arctic pollution: sensitivity to cloud microphysics, or a bug?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19755, https://doi.org/10.5194/egusphere-egu26-19755, 2026.

All statistical tools come with assumptions. Yet many scientists treat statistics like a collection of black-box methods without learning the assumptions. Here I illustrate this problem using dozens of studies that claim to show that solar variability is a dominant driver of climate. I find that linear regression approaches are widely misused among these studies. In particular, they often violate the assumption of ‘no autocorrelation’ of the time series used, though it is common for studies to violate several or all of the assumptions of linear regression. The misuse of statistical tools has been a common problem across all fields of science for decades. This presentation serves as an important cautionary tale for the Earth Sciences and highlights the need for better statistical education and for statistical software that automatically checks input data for assumptions.

How to cite: Steiger, N.: Pervasive violation of statistical assumptions in studies linking solar variability to climate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19776, https://doi.org/10.5194/egusphere-egu26-19776, 2026.

A key reason for the widespread use of peat-based growth media in horticulture is their reliable nutrient availability when supplemented with fertilisers. However, due to environmental concerns over continued peat-extraction and use, peat-alternatives (e.g., coir, wood fibre, composted bark, biochar) are increasingly being used commercially. These alternative media often blend multiple materials, making it crucial to understand elemental composition and nutrient interactions between components. This study evaluates whether benchtop Energy Dispersive X-ray Fluorescence (EDXRF) can provide a rapid method for determining the elemental composition of peat-alternative components.

Representative growing media components (peat, coir, wood fibre, composted bark, biochar, horticultural lime, perlite, slow-release fertilisers, and trace-element fertiliser) were blended in different ratios to generate industry-representative mixes. Individual components and prepared mixes were dried and milled to ≤80 μm. An industry-representative mix (QC-50: 50% peat, 30% wood fibre, 10% composted bark, 10% coir, with fertiliser and lime additions) and 100% peat were analysed by EDXRF (Rigaku NEX-CG) for P, K, Mg, Ca, S, Fe, Mn, Zn, Cu and Mo, and compared against ICP-OES reference measurements. The instrument’s fundamental parameters (FP) method using a plant-based organic materials library showed large discrepancies relative to ICP-OES (relative differences: 268–390 084%) for most elements in both QC-50 and peat, with the exception of Ca in QC-50 (11%). These results confirm that the FP approach combined with loose-powder preparation is unsuitable for accurate elemental analysis of organic growing media.

An empirical calibration was subsequently developed using 18 matrix-matched standards (CRMs, in-house growing media and individual component standards). Matrix matching is challenging because mixes are mostly organic by volume, yet variable inorganic amendments (e.g., lime, fertilisers, and sometimes perlite) can strongly influence XRF absorption/enhancement effects. Calibration performance was optimised iteratively using QC-50 as the validation sample, until relative differences were <15% for all elements. When applied to 100% peat, agreement with ICP-OES results improved substantially for some macro-elements (e.g. Mg 10%, Ca 1%, S 19%) but remained poor for most trace elements (28–96%), demonstrating limited transferability of this calibration method across different elements and matrices tested.

Overall, these results demonstrate that loose powder preparation does not provide sufficiently robust accuracy for EDXRF analysis of organic growing media even with meticulous empirical matrix-matched calibration. We are therefore developing a pressed pellet method using a low-cost wax binder to improve sample homogeneity (packing density) and calibration transferability. Twenty unknown mixes will be analysed using both loose powder and pressed-pellet calibrations, and agreement with reference data (ICP-OES) will confirm method validation, supporting the development of EDXRF as a novel approach for growing media analysis.

How to cite: De Silva, T., Tupaz, C., Croffie, M., Daly, K., Gaffney, M., Stock, M., and Corbett, E.: Developing Matrix-Matched Empirical Calibrations for EDXRF Analysis of Peat-Alternative Growth Media, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20122, https://doi.org/10.5194/egusphere-egu26-20122, 2026.

In catchment hydrology, long-term data collection often starts as part of a (doctoral) research project. In some cases, the data collection continues on a limited budget, often using the field protocol and data management plan designed for the initial short-term project. Challenges and issues with the continued data collection are likely to arise, especially when there are multiple changes in the people involved. It is especially difficult for researchers who were not directly involved in the fieldwork to understand the data and must therefore rely on field notes and archived data. They then often encounter issues related to inconsistent metadata, such as inconsistent date-time formats and inconsistent or missing units, missing calibration files, and unclear file and processing script organization.

While the specific issues may sound very case-dependent, based on our own and other’s experiences from various research projects, it appears that many issues recur more frequently than one might expect (or be willing to admit). In this presentation, we will share our experiences with bringing spatially distributed groundwater level data collected in Sweden and Switzerland from the field to ready-to-use files. Additionally, we provide recommendations for overcoming the challenges during field data collection, data organization, documentation, and data processing using scripts. These include having a clear, detailed protocol for in the fieldwork and the data processing steps, and ensuring it is followed. Although protocols are often used, they are frequently not detailed enough or are not used as designed. The protocols might also not take into account the further use of the data, such as for hydrological modelling, beyond field collection. 

How to cite: Bremer, K., Staudinger, M., Seibert, J., and van Meerveld, I.: From Field to File: challenges and recommendations for handling hydrological data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20375, https://doi.org/10.5194/egusphere-egu26-20375, 2026.

In 2014 we developed the Wageningen Lowland Runoff Simulator (WALRUS), a conceptual rainfall-runoff model for catchments with shallow groundwater. Water managers and consultants were involved in model development. In addition, they sponsored the steps necessary for application: making an R package, user manual and tutorial, publishing these on GitHub and organising user days. WALRUS is now used operationally by several Dutch water authorities and for scientific studies in the Netherlands and abroad. When developing the model, we made certain design choices. Now, after twelve years of application in water management, science and education, we re-evaluate the consequences of those choices.

The lessons can be divided into things we learned about the model’s functioning and things we learned from how people use the model. Concerning the model’s functioning, we found that keeping the model representation close to reality has advantages and disadvantages. It makes it easy to understand what happens and why, but it also causes unrealistic expectations. Certain physically based relations hampered model performance because they contained thresholds, and deriving parameter values from field observations resulted in uncertainty and discussions about spatial representativeness.

Concerning the practical use, we found that the easy-to-use, open source R package with manual was indispensable for new users. Nearly all users preferred default options over the implemented user-defined functions to allow tailor-made solutions. Parameter calibration was more difficult than expected because the feedbacks necessary to simulate the hydrological processes in lowlands increase the risk of equifinality. In addition, lack of suitable discharge data for calibration prompted the request for default parameter values. Finally, the model was subject to unintended model use, sometimes violating basic assumptions and sometimes showing unique opportunities we had not thought of ourselves.

C.C. Brauer, A.J. Teuling, P.J.J.F. Torfs, R. Uijlenhoet (2014): The Wageningen Lowland Runoff Simulator (WALRUS): a lumped rainfall-runoff model for catchments with shallow groundwater, Geosci. Model Dev., 7, 2313-2332, doi:10.5194/gmd-7-2313-2014

How to cite: Brauer, C.: Re-evaluating the WALRUS rainfall-runoff model design after twelve years of application, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21915, https://doi.org/10.5194/egusphere-egu26-21915, 2026.

The end-Guadalupian (Middle Permian) mass extinction represents a pivotal yet enigmatic event in Earth's history. Its drivers, often attributed to the emplacement of the Emeishan Large Igneous Province, are intensely debated, with proposed mechanisms ranging from volcanic outgassing to sea-level fluctuations and widespread marine anoxia. However, a critical lack of high-resolution, multi-proxy records from key paleo-tropical regions has hindered a unified model. This study presents a fully integrated dataset combining field sedimentology, microfacies analysis, and a comprehensive suite of major, trace, and rare earth element geochemistry from the Wordian carbonates of the Salt Range, Pakistan, a classic Neotethyan margin. Our data reveal a pronounced transgressive systems tract, marked by a shift from peritidal cycles to deeper-water carbonates. Crucially, geochemical proxies (e.g., Sr/Ca, Mn/Sr) confirm this sea-level rise was accompanied by a shift in oceanic chemical budgets. More significantly, we identify a pre-extinction perturbation in redox-sensitive trace elements (e.g., V/Cr, U/Th, Mo enrichment) and nutrient tracers (P, Ba), indicating a trend towards deoxygenation and increased nutrient loading in the Tethyan ocean during the Wordian. We interpret this coupled sedimentological-geochemical signal as a direct record of eustatic rise-driven oceanographic stagnation. The transgression likely flooded vast continental shelves, enhancing organic matter burial and fostering the development of stratified, anoxic water masses on a near-global scale. The synchronicity of this event with the onset of Emeishan volcanism suggests a powerful feedback mechanism: sea-level rise created the environmental context in which the effects of volcanism (e.g., nutrient runoff, greenhouse warming) were dramatically amplified. By providing a high-resolution record from the Tethyan gateway, this research places the Wordian of the Salt Range as a vital recorder of pre-extinction environmental deterioration. Our findings demonstrate that the stage for the end-Guadalupian catastrophe was set several million years earlier by oceanographic upheaval, forcing a re-evaluation of the extinction's triggers and providing a critical ancient analogue for modern sea-level rise and ocean deoxygenation.

How to cite: Wadood, B.: Pre-Extinction Stress in the Salt Range: Wordian Eustasy and its Role in the End-Guadalupian Crisis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-546, https://doi.org/10.5194/egusphere-egu26-546, 2026.

On the modern Earth, oxidative weathering of continental crust constitutes the dominant source of most nutrient elements to the ocean that ultimately sustains the biosphere over geological timescales. However, continental crust exposed above sealevel may have been scarce on the early Earth, and oxidation was limited prior to the rise of atmospheric O₂ at ca. 2.4-2.3 billion years ago (Ga). Several experimental and modelling studies have therefore suggested that anoxic seafloor weathering and hydrothermal alteration provided the major sources of bioessential elements such as phosphate and transition metals. Here, these datasets are reviewed, and new supportive evidence is presented from the Paleoarchean North Star and Mount Ada basalts (3.5-3.47 Ga) in the Pilbara craton, Western Australia. Alteration gradients reveal depletion in key nutrients, supporting the idea that this process contributed to sustaining microbial ecosystems at that time. Direct evidence of a Paleoarchean seafloor biosphere is preserved in the form of microbialites found in an offshore marine setting with no evidence of felsic material influx. Collectively, these findings show that life could be maintained on an ocean-dominated planet; however, continental emergence was perhaps important for biological diversification and innovation over the later course of Earth’s history.

How to cite: Stüeken, E.: Exploring seafloor alteration as a viable mechanism to sustain Earth’s earliest biosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2631, https://doi.org/10.5194/egusphere-egu26-2631, 2026.

Banded Iron Formations (BIFs) are authigenic marine sedimentary rocks that record the composition of Precambrian seawater and provide key insights into early marine environments. The Paleoarchean Algoma-type Tomka BIF from the Daitari Greenstone Belt (India) is considered to be ~3.37–3.50 Ga old and to have experienced only greenschist-facies metamorphism, in contrast to many Eo- to Paleoarchean BIFs that were metamorphosed under much higher amphibolite-facies conditions. Despite this relatively low metamorphic overprint, the potential of the Tomka BIF as a reliable archive of ancient seawater chemistry has not yet been evaluated. Still, this location may be crucial to better understand the evolution of Palaeoarchean marine habitats and their interactions with early landmasses and the atmosphere.

To better constrain both the depositional age and the paleoenvironmental conditions of the Tomka BIF, we analysed major and trace element abundances together with radiogenic Hf–Nd isotope compositions of individual Fe- and Si-rich BIF layers, as well as an associated shale. Tomka BIF samples lacking detrital contamination and post-depositional alteration display typical Archean, shale-normalised seawater-like rare earth and yttrium (REY_SN​) patterns. These include positive La_SN, Eu_SN​, and Gd_SN​ anomalies, superchondritic Y/Ho ratios, the absence of negative Ce_SN​ anomalies, and enrichment of heavy relative to light REY_SN​. Collectively, these signatures indicate deposition in an anoxic marine environment influenced by high-temperature submarine hydrothermal activity.

BIF samples preserving pristine Hf–Nd isotope compositions define coherent trends along the ¹⁷⁶Lu–¹⁷⁶Hf and ¹⁴⁷Sm–¹⁴³Nd reference isochrons corresponding to the inferred depositional age of 3.37–3.50 Ga. Initial εNd values (+0.1 to +5.3) indicate a juvenile source contribution to Tomka seawater, while the associated shale (εNd = -0.3 to +1.1) reflects a similarly juvenile provenance for the detrital component. In contrast, initial εHf​ values of the BIFs (-4.8 to +145) are strongly decoupled from the Nd isotope system and from the so-called terrestrial array, which reflects the coupled behaviour of Hf-Nd in magmatic systems. A Hf-Nd isotope decoupling in low-temperature systems, however, is related to incongruent Hf weathering, as described by the so-called zircon effect. Applied to the Daitari BIFs, this decoupling likely reflects the emergence and weathering of a zircon-bearing crust in the proto-Singhbhum Craton, which influenced Archean seawater chemistry by at least 3.37 Ga.

How to cite: Viehmann, S., Krayer, J., Jodder, J., Pakulla, J., Münker, C., Hofmann, A., Schulz, T., Koeberl, C., and Weyer, S.:  Banded Iron Formations as archives for ca. 3.5 Ga old marine environments: Insights from REE and Hf-Nd isotope signatures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2702, https://doi.org/10.5194/egusphere-egu26-2702, 2026.

Loess–paleosol sequences (LPS) constitute continuous terrestrial archives of Quaternary climate change, recording both local environmental conditions and large-scale atmospheric dynamics. While LPS have been extensively studied worldwide, those of the Lower Danube–Black Sea (LDBS) region of Romania and Bulgaria remain comparatively underexplored. Situated at the nexus of Mediterranean, central European, and continental western Asian air masses, the LDBS region offers a unique opportunity to investigate large-scale climate shifts and their associated environmental responses.

The LOEs-CLIMBE project, funded by the Swiss National Science Foundation (SNSF) through the Multilateral Academic Projects (MAPS) scheme with support from the Romanian (UEFSCDI) and Bulgarian funding agencies, addresses this gap through a high-resolution, multi-proxy investigation of two key LPS sites: Urluia (Romania) and Kolobar (Bulgaria). Spanning the last ~800 ka, with particular focus on the Mid-Brunhes Event onwards (MBE), the project integrates elemental composition, stable isotope records, and molecular biomarkers within a newly established chronological framework. These proxies support reconstructions of vegetation dynamics, climate variability, and pedogenic processes across multiple glacial–interglacial cycles.

Here, we present preliminary results from both LPS. The site at Urluia, located in southeastern Romania, is a former quarry exposing a >20 m thick, continuous LPS. The sequence comprises multiple complex palaeosols (S1–S5), interpreted as interglacial soils, interbedded with massive loess units deposited during glacial periods.

Near the village of Kolobar, situated in northeastern Bulgaria and distal from both the Danube and the Black Sea, is an active quarry. Here, a ~25 m thick LPS is exposed with ~1.1 m of modern soil on top. Approximately seven major palaeosols (S1–S7) extend back to ~800 ka. Field observations identify a marked stratigraphic shift at S4, from thick loess units with thin palaeosols above to massive palaeosols with thinner loess below. This transition coincides with an increase in bulk density from ~1.41 to 1.61 g cm⁻³ and is interpreted as the onset of the MBE, a transition not represented at Urluia. Carbonate precipitation is observed in all palaeosols above the S7, while loess dolls occur in the L1 and L2. Bioturbation, including crotovinas from mammals and earthworm burrows as well as root traces, is widespread throughout the whole sequence. However, this is present at different depths in different assemblages. Altogether, these field observations argue for an apparent grass steppe vegetation with fluctuating populations of burrowing organisms throughout the last 800 ka, while hydrological and sedimentary conditions have changed considerably between periods with predominant loess sedimentation and stronger soil formation. We will present these first findings and support them with elemental and stable isotope composition alongside organic matter composition gained from infrared spectroscopy measurements.

How to cite: Trott, A., Veres, D., Jordanova, D., and Wiesenberg, G.: A reconstruction of Lower Danube-Black Sea climate history. First insights from novel loess-paleosol sequences., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2744, https://doi.org/10.5194/egusphere-egu26-2744, 2026.

As a consequence of the evolution of the water-bearing basal magma ocean (MO), water-induced mantle overturn can well account for many puzzling observations in the early Earth, such as the formation of the Archean continents, the Archean–Proterozoic boundary, and high Archean paleomagnetic field (Wu et al., 2023; Wang and Wu 2026). The early Earth may have experienced a deep-water cycle totally different from the current. High pressure studies suggest that the whole-mantle MO evolved into an outer MO and a basal MO. With the solidification, water in the basal MO moved toward the core-mantle boundary and the basal MO eventually became gravitationally unstable because of the enrichment of water (Fig.1). The instability triggered the massive mantle overturns and resulted in the major pulses of the thick SCLM and continental crust generations in the Neoarchean. The mantle overturns eventually got rid of the whole basal MO and the mechanism which generated the Archean-type SCLM and continents likely no more worked after the overturns. Thus, water-induced mantle overturns can account for why Archean-type SCLM and continents basically occurred in the Archean (Wu et al., 2023). The mantle overturn can substantially accelerate the cooling of the core and strengthen the geomagnetic field, which explains well the high paleointensity records from ~3.5–2.5 Ga (Wang and Wu 2026).

Besides the enrichment of water, the basal MO was enriched with ferric iron. This study shows that the ascent of ferric-rich basal MO and its mixing with the upper mantle could account for the observed shift in the redox state of the upper mantle during the Archean. Both the redox state shift and the generation of Archean continents result from these mantle overturns. Therefore, it is expected that the shift in mantle fO₂ aligns with the timing of continental generation, which is supported by the observations. The mantle overturns are rare with age > ~ 3.6 Ga, but their frequency increases with age < ~3.6 Ga and reaches the maximum in the Neoarchean. The combined effects of the ascent of the deep oxidized material, the emergence of continents, and oxygenic photosynthesis generated the broader First Redox Revolution of the Earth system, ultimately initiating the GOE shortly after the end of the Archean.

Wu, Z., Song, J., Zhao, G., and Pan, Z. (2023). Water-induced mantle overturns leading to the origins of Archean continents and subcontinental lithospheric mantle. Geophysical Research Letters, 50, e2023GL105178. https://doi.org/10.1029/2023GL105178

Wu, Z., and Wang, D. (2026) Water-Induced Mantle Overturn Explains High Archean Paleointensities. National Science Review. https://doi.org/10.1093/nsr/nwaf578

Figure 1. Schematic illustration of the water-induced mantle overturns (superplumes). The waterdrop is used to describe the hydrous silicate melts although hydrogen mainly exists as hydroxyls in silicate melts. (a) The solidification of a whole mantle magma ocean (MO) at the mid mantle forms an outer MO and a basal MO. (b) The basal MO eventually becomes gravity unstable and generates mantle overturns because of the enrichment of water

How to cite: Wu, Z., Deng, X., and Song, J.: Water-Induced Mantle Overturns Leading to the Oxidation of Archean Upper Mantle, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3482, https://doi.org/10.5194/egusphere-egu26-3482, 2026.

Understanding the dynamics between past global climate events and their impact on marine ecosystems and paleoclimate is essential for the estimation of potential future changes. Accordingly, sedimentary archives accumulating on the seafloor provide crucial information on climate-driven environmental variability during the late Quaternary. Sediment cores were taken from the Gulf of Edremit, which is located in the northern Aegean Sea. We aimed to provide a preliminary, multi-proxy parameters, including sedimentological and geochemical records during the Holocene. During the marine survey with the R/V TÜBİTAK MARMARA Research Vessel, three sediment cores (E-01, E-02, and E-03A) obtained from different water depths across the gulf were investigated. Lithological observations from all cores indicate a sedimentation pattern dominated by fine-grained clay- and silt-sized deposits. However, locally occurring black laminae and FeS bands reflect depositional conditions sensitive to variations in bottom-water oxygenation. Fluctuations in the density and magnetic susceptibility measured by MSCL further support variability in sediment input and depositional processes at the sea floor. TOC data from core E-02 (at a water depth of 86 m) show low values (0.8–1.0 wt%) in the lower part, indicating low productivity and/or poor preservation of organic matter. TOC then rises to ~1.0–1.5 wt% further up the core, suggesting improved productivity or preservation. The highest values (1.5–2.0 wt%) in the uppermost 0–10 cm may reflect the presence of sapropelic material. XRF data from core E-03A reveal a Sr/Ca peak at 40–50 cm, which indicates increased salinity during drier periods. At 140–150 cm, the Sr/Ca ratio decreases while the Ca/Ti ratio increases, suggesting enhanced carbonate deposition relative to detrital input. In core E-01, a Mn/Fe peak at 10–15 cm reflects changes in redox and oxygen conditions. There is strong variability in Ca/Ti and Sr/Ca at 45–50 cm: higher Sr/Ca above this depth indicates greater carbonate production, while lower Ca/Ti implies reduced clastic input. Below 65 cm, falling Sr/Ca and rising Ca/Ti suggest diminished carbonate production and a return to lithogenic dominance. As a conclusion, sedimentation in the Gulf of Edremit appears to be highly sensitive to climate and carbon cycle changes.

This study was granted and supported by the TÜBİTAK (The Scientific and Technological Research Council of Türkiye) with Project number 123Y108.

Keywords: Gulf of Edremit, Holocene, multi-proxy analysis, TOC, XRF.

How to cite: Vurmuş, Z. D., Erol, İ., Biltekin, D., Eriş, K. K., Atabay, H., Özsu, E., Çiftbudak, Ö. F., Tolun, L. G., Akyol, O., Kanbur, S., Ustaoğlu, B., Koç, D. E., Uçarkuş, G., and Schwamborn, G. J.: Paleoenvironmental and Paleoclimate Changes in the Gulf of Edremit (Northern Aegean Sea) during the Holocene based on Sedimentological and Geochemical Multi-Proxy Records, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5038, https://doi.org/10.5194/egusphere-egu26-5038, 2026.

Phosphorous availability is required for biological productivity, nutrient cycling and oxygenation. Over recent years, reduced phosphorous (phosphite) has moved into focus as a potentially new proxy that can provide information about environmental conditions and biogeochemical cycles in deep time. Phosphite can be generated by a range of biological and abiotic processes, but its distribution and implications are so far poorly understood.

To address this knowledge gap, we investigated phosphate and phosphite concentrations in stromatolites spanning from the Archean to the modern. Stromatolites are among the oldest life forms found on Earth, preserved in the fossil record, dating back to 3500 million years ago. They are formed in shallow water, mostly by the metabolic activity of a diverse microbial ecosystem. They are composed of carbonate minerals, which can trap both phosphate and phosphite in their crystal lattice. 

We measured phosphorus speciation with Ion Chromatography and Inductively coupled plasma mass spectrometry. The data reveal that carbonate-associated phosphate and phosphite date back to the early Precambrian, presenting the first record of phosphite in carbonate rocks of low metamorphic grade. The phosphite may be of biogenic origin, but also non-biological sources such as meteorite impacts, hydrothermal activity or weathering of high-grade metamorphic rocks are plausible. These abiotic sources could potentially be more important on Mars, whose mantle has a lower oxygen fugacity, and where impact debris is well-preserved near the surface. Our study reveals that carbonate records can be used to reconstruct the history of phosphorus redox speciation on Earth and perhaps early Mars.

How to cite: Tsinidis, M. and Stueeken, E.: Tracking phosphorus redox speciation in microbial carbonates through Earth’s history and beyond, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5153, https://doi.org/10.5194/egusphere-egu26-5153, 2026.

Isotope distribution in precipitation along with climate monitoring data such as amount of precipitation, temperature and relative humidity were collected from a region characterized by a high continentality index, region situated in the external sector of the Southern Carpathians. Stable isotope composition of hydrogen and oxygen in precipitation were collected monthly from 2012 to 2025, with climate monitoring measured automatically each 30 minutes. The isotope and temperature signals were split in two groups including October to April and May to September, variations over an interval of 14 years being statistical presented. For the intervals considered, the LMWL show the effect of secondary evaporation of falling raindrops with lower slope for the warm season. The data support significant relationships between d¹⁸O and d D values and average air temperatures with r² = 0.7, n = 150. Deuterium excess values over the year are compatible with seasonal variations for the origin of moisture, with high values during wintertime, possible resulting from the input of seasonal related Mediterranean moisture during November to February. The strong seasonal distribution of precipitation amount combined with elevated temperature peaks during July have a strong impact on the clastic multi-layered aquifers situated in the Lower Quaternary deposits, driving during the last years to complete evaporation of the highest aquifer.

How to cite: Bojar, A.-V., Chmiel, S., Bojar, H.-P., Pelc, A., and Vaida, F.: Stable isotope composition of precipitation and temperature seasonal distribution from the South Carpathians: insights for climate variations in the interval 2012 to 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5244, https://doi.org/10.5194/egusphere-egu26-5244, 2026.

Oceanic anoxic events represent major perturbations of marine redox conditions with varying spatial extents of ocean deoxygenation through Earth’s history. The isotopic composition of redox-sensitive elements, preserved in sedimentary archives, particularly molybdenum (Mo) and uranium (U) isotopes, are powerful proxies for reconstructing past ocean oxygenation. However, Mo and U isotope compositions can be influenced by both global ocean anoxia and local depositional conditions. Both isotope systems show opposite isotope fractionation behavior under variable local redox conditions but are expected to be shifted in the same direction (towards lower values) at a global expansion of seafloor anoxia, allowing combined U-Mo isotope analyses to discriminate between local and global redox signals. The Toarcian Oceanic Anoxic Event (T-OAE; ~183 Ma) represents an Early Jurassic interval of marine deoxygenation and environmental perturbation, but it remains incompletely understood whether ocean anoxia was globally extensive or locally restricted.

Here, we present combined U-Mo isotope data from black shales deposited during and after the T-OAE at two locations within the European Epicontinental Sea (Schandelah, North German Basin, and Metzingen, South German Basin). During the T-OAE, all sections are characterized by light Mo and U isotope compositions, reaching values as low as 0.61-0.73 ‰ for δ⁹⁸Mo and -0.19 to -0.13 ‰ for δ²³⁸U. Following the T-OAE, both isotope systems show an increase towards heavier δ⁹⁸Mo values between 1.66 and 1.73 ‰ and δ²³⁸U values between 0.12 and 0.19 ‰ across both sites. This observed positive correlation between Mo and U isotope compositions is consistent with a global expansion of seafloor anoxia. To further exclude potential local effects, we used redox- and salinity-sensitive proxies, such as Fe/Al, Sr/Ba, B/Ga, and TS/TOC ratios. These proxies show no significant variations across the T-OAE interval and beyond, indicating stable depositional conditions at both localities. Therefore, the U-Mo isotope shifts in the black shales likely reflect a global expansion of seafloor anoxia during the T-OAE.

How to cite: Klamt, V., Krencker, F.-N., Mann, T., Kaufmann, A., Arp, G., van de Schootbrugge, B., Viehmann, S., and Weyer, S.: Reconstructing marine redox conditions during the Toarcian Oceanic Anoxic Event constrained by combined U-Mo isotopes in black shales, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7126, https://doi.org/10.5194/egusphere-egu26-7126, 2026.

Reconstructing past climate dynamics on terrestrial environment remains a major challenge in paleoclimate research. Improving our understanding of how continental ecosystems responded to abrupt climate oscillations is essential for assessing future climate impacts on terrestrial environments and human societies. While ice-core and marine archives document large-scale and rapid climate variability, the links between climate and continental surface processes remain poorly constrained. Identifying robust climate proxies in continental sedimentary records is therefore crucial.

Fossil earthworm calcite granules preserved in loess–paleosol sequences have recently emerged as promising archives of past climate conditions, providing insights into temperature and precipitation during the last glacial period in Western Europe. However, the climatic interpretation of these proxies requires a robust calibration based on modern earthworm calcite granules to better constrain the environmental and biological parameters controlling granule formation, such as temperature, soil moisture, and litter composition.

Here, we present an experimental calibration approach using modern earthworms (Lumbricus terrestris) reared under controlled environmental conditions. Soil temperature and food sources were systematically varied to assess their influence on granule production and isotopic signatures. Calcite granules were analysed for δ¹⁸O and δ¹³C, while δ¹³C was also measured in soil organic matter and litter. For the first time, clumped isotope (Δ₄₇) measurements were performed on earthworm calcite granules, allowing direct temperature estimates independent of past soil-water δ¹⁸O.

This experimental approach provides new constraints on vital effects and isotopic fractionation in earthworm calcite granules and improves their use as quantitative paleoclimate proxies. Our results complement previously established empirical relationships between (i) the oxygen isotopic composition of meteoric water, granules, and temperature, and (ii) the δ¹³C of litter and the δ¹³C of granules, strengthening the potential of earthworm calcite granules for reconstructing past terrestrial climate dynamics.

How to cite: Prud homme, C., Rigaudier, T., Auclerc, A., and Daëron, M.: Reconstructing climate dynamics on terrestrial environment using the stable isotope composition of earthworm calcite granule: An experimental approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7400, https://doi.org/10.5194/egusphere-egu26-7400, 2026.

The analysis of isotopic composition (δ¹⁸O and δ²H) in precipitation is a powerful approach for investigating (paleo)climatic processes within the hydrological cycle. Variations in δ¹⁸O and δ²H in precipitation result from successive isotopic fractionation processes during atmospheric transport and are observed across both spatial and temporal scales. While modern isotopic records are extensively documented, e.g., through the IAEA/WMO network, European datasets are largely limited to monthly resolution and remain sparse at the regional scale. This is particularly the case for the Swabian Alb (or Swabian Jura) in southwestern Germany, a karst plateau south of Stuttgart, approximately 220 km long and 40 km wide, with mean elevations around 500 m and peaks reaching 1110 m. The Swabian Alb holds international significance as a UNESCO Global Geopark and includes six caves designated as UNESCO World Heritage sites. The region constitutes a natural divide between two significant European basins: the Rhine and the Danube. The oxygen isotopic composition of meteoric water from the Swabian Alb provides key insights into modern moisture sources and, when preserved in paleoclimate archives such as speleothems, offers valuable information on past atmospheric circulation and hydroclimate.

Here, we compare measured δ¹⁸O and δ²H in meteoric water with simulations of isotope-enabled climate model (ECHAM6-wiso) to investigate spatial and temporal variabilities, and identify climatic factors influencing regional isotopic patterns. We present δ¹⁸O and δ²H records of weekly to monthly sampled rainwater across the Swabian Alb from October 2023 to present-day. We examine simulated and observed interannual changes in precipitation, teleconnections, and seasonality patterns. In addition, we fill a gap by providing daily δ¹⁸O and δ²H values of meteoric water collected at a weather station located in Tübingen.

Investigating variations in modern water isotope records across the Swabian Alb is essential for regional paleoclimate research and allows the validation of isotope-enabled climate models on the local scale. Our results show the first model–data comparison for the Swabian Alb and pave the way towards regional climatic reconstructions e.g., paleoclimate of the last glacial period, when modern humans occupied caves of the Swabian Alb.

How to cite: Ballian, A., Racky, M., Maisch, M., Novello, V., Lo Triglia, D., and Rehfeld, K.:  A regional scale data–model comparison of modern oxygen stable isotopes in precipitation (Swabian Alb, southwest Germany) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7765, https://doi.org/10.5194/egusphere-egu26-7765, 2026.

Around the Late Priabonian-Early Rupelian, the Paris Basin is characterized by an incomplete succession of sediments deposited at the marine-continent interface. In the overall marine record, this interval is marked by the Eocene-Oligocene Transition (EOT), characterized by a climate deterioration and a significant sea level drop, associated with the permanent establishment of the Antarctic ice cap. Nevertheless, the EOT is poorly documented and understood in terrestrial areas.

Located between the active tectonic regions of the Pyrenean and Alpine orogens and the West-European Cenozoic Rift Systems, the lagoon to lacustrine deposits of the Paris Basin therefore enable to acutely record both global and local processes (glacio-eustasy, climate, tectonic). A detailed stratigraphic framework is consequently necessary to estimate the contribution of each of these controls. This study is based on: 1) a large-scale correlation of boreholes in order to study the 3D organization of deposits and their lateral and vertical variations, and 2) an elementary and isotopic geochemical, mineralogical, and paleontological study to clarify the depositional environments and the causes of the observed variations (sea level, tectonic and hydrological changes). The analyzed sites are located around tectonic structures (the Bray, Beynes-Meudon, and Remarde anticlines and the Saint-Denis syncline) and in various areas, ranging from the edges to the center of the Paris Basin.

We established a correlation between lagoon-marine deposits of the center of the basin and lacustrine deposits of its southern and eastern edges. Detailed sedimentological studies of the sites reveal a two-steps evolution. The first step is marked by marls deposited during the latest Priabonian. Their mineralogical and chemical composition indicates a deposition evolving from a clastic to a chemical-dominated system in a wetter to drier climate. The second step, during Early Rupelian times, shows the return to detrital deposition in a wetter climate. More specifically, the sections show a mineralogical, chemical and environmental separations. The Priabonian cycle is influenced by sea level variations (marine incursion, then confinement of the basin) and a climate changing from wetter to drier. The Rupelian cycle shows a global transgression in a wetter climate, briefly interrupted by a confinement of the basin, but above all the reactivation of tectonic structures linked to the Pyrenean compression, which caused palustrine deposits on the anticlines and marine deposits in the synclines.

The Paris Basin shows to a lesser extent the same record of the EOT as several marine sites. The major regression is only illustrated by the confinement and partial emersion of the basin in the latest Priabonian; the cooling seems to be recorded by the progressive increase in oxygen isotope values, and the aridification by mineralogical proxies and the known floral evolution. The basin also reflects the west-European regional geodynamics with the recurrence of tectonic structures in the Early Rupelian associated with the African-Eurasian convergence, illustrated for instance as well by the inversion of the Cotentin and Hampshire basins, further north of the Paris Basin. 

How to cite: Beernaert, M., Le Callonnec, L., Minoletti, F., Bauer, H., and Quesnel, F.: A not so tranquil basin: recording of the west-European geodynamics amidst marine incursions and retreats in the Paris Basin., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7870, https://doi.org/10.5194/egusphere-egu26-7870, 2026.

The Oxfordian interval is characterized by a long-term (~6 Myr) increase in carbon isotope values, punctuated by several short-lived (<1 Myr) positive carbon isotope excursions (CIEs) occurring in the lower Oxfordian, and in the middle Oxfordian. These excursions have only been recognized in a limited number of sections and their spatial extent, stratigraphic reproducibility, and paleoenvironmental significance remain poorly constrained, and their potential relationship to oceanic anoxic events (OAEs) remains uncertain.

Here, we present a high-resolution, multi-proxy chemostratigraphic dataset from shallow-marine Oxfordian successions of northwestern Europe, integrating inorganic and organic carbon isotopes (δ¹³C_inorg and δ¹³C_org), palynofacies analysis, and Rock-Eval pyrolysis. The dataset combines subsurface data from the Konrad #101 borehole (southeastern Lower Saxony Basin, northern Germany) with new outcrop data from the northern Paris Basin (Normandy, France). Both successions are constrained by robust biostratigraphic frameworks, enabling detailed intra- and interbasinal correlations.

Our results reveal pronounced and reproducible carbon isotope trends, including a ~3.0‰ positive CIE recorded in both δ¹³C_inorg and δ¹³C_org within the lower to middle Oxfordian interval. Comparison with available records from Europe, western Asia, and the Gulf of Mexico suggests that these excursions may reflect regionally synchronous perturbations of the exogenic carbon cycle, although the degree of global synchronicity remains equivocal. The integration of geochemical and palynofacies data provides new insights into the paleoenvironmental context of these events by demonstrating that the observed carbon isotope fluctuations are not driven by changes in organic matter preservation or mixing of organic matter sources (e.g., marine versus terrestrial inputs). This multi-proxy approach allows a critical assessment of whether Oxfordian CIEs constitute robust chemostratigraphic markers and whether they can be plausibly linked to episodes of widespread marine oxygen depletion.

How to cite: Krencker, F.-N., Hansen, J., Rudolph, M., Andrieu, S., Blumenberg, M., Mann, T., and Heimhofer, U.: Carbon isotope excursions during the Oxfordian: multi-proxy constraints on carbon cycle dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10177, https://doi.org/10.5194/egusphere-egu26-10177, 2026.

The Mundrabilla meteorite can be classified as a medium octahedrite nickel-iron type, the kamacite being the dominant mineral. The meteorite was discovered in 1911 in Mundrabilla (Australia), the most important fragments weighing between 3.5 kg and 24 tons.

To get more information concerning the structure and composition of a 1.5 kg fragment of the Mundrabilla meteorite existing in the collection of the National Geological Museum, Bucharest, a small fragment was extracted using a water jet cutter. More analytic techniques, such as XRD, SEM-EDX, and ultra-low background gamma ray spectrometry, were used to analyse it.

A detailed investigation performed by XRD evidenced the presence of the α-FeNi phase, identified as kamacite. Its crystal chemical formula, calculated based on SEM-EDX analysis, was Fe_0.937Ni_0.063. The cell parameters of kamacite, as determined by least squares refinement of the X-ray powder data, are: a = 2.8717(7) Å and V = 23.68 ų. On the diffraction pattern, minor peaks were observed, which could be attributed to γ-FeNi taenite.

The geochemical composition determined by SEM-EDX investigation is typical of iron-bearing meteorites. XRD indicates as main phase kamacite, but traces of other elements reflect the presence of other minor mineral phases. The presence of quite abundant C and minor Si fits with the presence as minor phases of moissanite (SiC) and cohenite (Fe,Ni)₃C. The S content could be related to traces of troilite (FeS) or pyrrhotite (Fe_1-xS), while the presence of minor P could be attributed to rhabdite (Fe, Ni)P.

The gamma-ray spectroscopy performed in the ultra-low background laboratory at the Slanic (Prahova) salt mine evidenced the presence of ²⁶Al and ⁶⁰Co, two cosmogenic radionuclides produced by cosmic neutrons through the spallation of ²⁸Si or resulting from the β-decay of ⁶⁰Fe, which is also generated by the neutron activation of the stable ²⁸Fe. Both ²⁶Al and ⁶⁰Fe are long-lived isotopes with half-life times of 0.747 and 2.62 My, respectively, which explain their presence in meteorites.

How to cite: Dumitras, D.-G., Radulescu, C., Margineanu, R. M., Ricman, C., Blebea-Apostu, A.-M., Gomoiu, C., Dulama, I.-D., Stihi, C., Bucurica, I.-A., Duliu, O. G., Marincea, S., and Sirbu-Radaseanu, D. S.: Ultra-low background gamma-ray spectrometry, SEM-EDX and XRD investigation of a fragment of the Mundrabilla (Australia) iron meteorite. Rare cosmogenic 26Al and 60Co radioisotopes evidenced, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10242, https://doi.org/10.5194/egusphere-egu26-10242, 2026.

Lead (Pb) and its isotopes are known to be released incongruently during early chemical weathering in continental settings. Incongruent weathering implies that a chemical weathering induced continental runoff trace metal isotope signature is not identical to bulk rock isotopic compositions. The incongruent release of Pb can mostly be ascribed to preferential chemical weathering of less weathering resistant accessory uranium and thorium-rich mineral phases present that are most abundant in differentiated continental crust. If this continental crust is ancient, these accessory mineral phases contain present-day Pb isotopic signatures that are in places extremely radiogenic, as well as substantially different from bulk rock Pb isotopic compositions. Several studies that investigated the Pb isotopic runoff evolution in the Labrador Sea, NW Atlantic and Arctic Beaufort Sea already reported very radiogenic Pb isotopic runoff signatures in these marine basins bordering the Laurentide Ice Sheet (LIS) during key time intervals of the last deglaciation. These earlier results require the existence of very radiogenic Pb isotopic freshwater signatures inland North America that were generated during incipient post-glacial chemical weathering reactions in response to the retreat of the LIS during the last deglaciation.

We targeted subarctic Lake Melville in central Labrador aiming to resolve how the Pb specific chemical weathering signature changed in response to deglacial warming, in an initially subglacial setting that transitioned to completely ice-free conditions in the early Holocene. Lake Melville is a fjord‑like subarctic estuary in central Labrador that receives most of its freshwater and sediment from the Churchill River and other major tributaries draining a large early to mid-Proterozoic shield. We analysed two sediment cores from central Lake Melville that together archived the ambient dissolved Pb isotope signature over the past 13 ka. Our authigenic Pb isotope records are complemented by associated bulk detrital Pb isotope compositions, enabling us to compare the dissolved Pb isotope signature in the lake with corresponding sedimentary signatures. The lake was covered by the LIS until about 10.3 ka BP, yet still located in an ice-proximal setting until 8.5 ka BP. The region Labrador-Québec was ice free after ca. 5.7 ka BP.

The most striking result of our record is the observation of (i) very radiogenic authigenic Pb isotope compositions throughout that are (ii) much elevated relative to the associated detrital compositions, which are rather unradiogenic. Very invariant Pb isotopic signatures observed until 10.5 ka BP confirm the suggested subglacial lacustrine sedimentary setting in the oldest section. The subsequent deglaciation witnessed most variable compositions, with most radiogenic compositions seen at ~8.2 ka BP. The record becomes substantially smoother after ~6 ka BP when the catchment area was no longer influenced by direct glacial runoff. While the detrital compositions suggest some geographic variability in sediment sourcing, the authigenic Pb isotopic compositions are not following these detrital signatures. Our results highlight the unique geological setting that make authigenic Pb isotopes in proximal North American sediment cores a sensitive proxy for for the detection of elevated deglacial runoff fluxes in circum-North American marine basins.   

How to cite: Gutjahr, M., Thomsen, S., Hallmaier, M., Gebhardt, C., and Ohlendorf, C.: Continental runoff lead isotopic signatures released during incongruent chemical weathering in subarctic Lake Melville associated with the retreat of the Laurentide Ice Sheet over the past 14 ka, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10274, https://doi.org/10.5194/egusphere-egu26-10274, 2026.

This presentation examines recent developments in the application of oxygen stable isotope analyses to lacustrine invertebrate remains (e.g. chironomids) within palaeoenvironmental science. We explore improvements to instrumentation and measurement, and the opportunities that this presents for a more nuanced palaeoenvironmental approach. The improvements to the existing methodology of δ¹⁸O_chitin measurements now allow the possibility of taxon specific δ¹⁸O_chitin reconstructions and thus the potential to enhance our understanding of paleoclimate dynamics. Opportunities to reduce the sample size required have come from improvements to instrumentation, through more sensitive Thermal Conversion Elemental Analyser isotope ratio mass spectrometry (TC/EA-IRMS). We discuss the considerations needed to assess the sample size measured and avoid systematic bias. Is smallest always best or does this lead to a biased environmental reconstruction? Further, it is also unclear what between-taxa offsets exist for different chironomid morphotypes and whether δ¹⁸O_chitin offsets between taxa are stationary across large climate transitions, and the extent to which changing vital effects play a role. We present new data on taxon-specific trends from the robustly dated late-glacial sediment record from Lake Llangorse, UK. This will allow us to determine whether temperature is the main driver of the δ¹⁸O_chitin signal of each taxon, or if vital effects play a role.

How to cite: Lamb, A. and Engels, S.: Stable isotope analyses of lacustrine chitinous invertebrate remains: analytical advances, challenges and potential., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10452, https://doi.org/10.5194/egusphere-egu26-10452, 2026.

Banded iron formations (BIFs) are authigenic marine sedimentary rocks that formed in Precambrian oceans. They may record the chemical composition of the ambient seawater and are thus important archives for reconstructing ancient marine environments. The ca. 3.25 Ga Algoma-type BIF of the Fig Tree Group in the Barberton Greenstone Belt, South Africa, provides insights into the Palaeoarchaean marine environments and seawater chemistry during the early development of the Kaapvaal Craton [1,2]. However, it remains incompletely understood, which mineral phases within this BIF most reliably preserve primary seawater-derived signatures and therefore represent the most suitable archives for palaeo-environmental reconstructions.

We present trace and major element concentrations of 28 individual layers of Fig Tree Group BIF. These layers are dominated by either magnetite, chert, or siderite. In addition, mudstones intercalated with BIF were also analysed. All samples originate from the BARB 4 drill core and were digested using HF–HNO₃–HCl digestion combined with ICP-MS and OES analyses to investigate the geochemical composition of the different mineral phases and their reliability as archive for ancient seawater chemistry.

Immobile element (Zr, Th) concentrations are in the ppb to ppm level range and vary over four orders of magnitude between the BIF samples. Samples with the highest immobile element concentrations show non-seawater-like shale-normalised (subscript SN) rare earth element and yttrium (REY) patterns and a positive correlation of REY and immobile element concentrations (e.g. Zr), in indicating detrital contamination. However, cherts and five of the magnetite samples with the lowest immobile element concentrations show typical Archaean seawater-like signatures with positive La_SN Gd_SN, and Y_SN anomalies as well as a depletion of light REY relative to heavy REY_SN, indicating a seawater-derived origin. Positive Eu_SN anomalies indicate contributions of high-temperature hydrothermal fluids. The lack of negative Ce_SN anomalies indicates anoxic depositional conditions with respect to the Ce³⁺-Ce⁴⁺ redox couple. The chert layers, however, show Th/U fractionation compared to the value of the continental crust, suggesting redox-dependent uranium mobilization, indicative of slightly oxic conditions.

We identified chert and magnetite, if devoid of detrital contamination, to be the most suitable phases in Fig Tree Group BIF for obtaining information to reconstruct their depositional environment. The remaining layers, on the contrary, do not reflect pure seawater precipitates and have to be excluded for interpretations regarding ancient seawater chemistry.

[1] Hofmann, 2005, Precambrian Res. 143, 23-49

[2] Satkoski et al., 2015, EPSL 430, 43-53

How to cite: Winkler, V., Krayer, J., Hofmann, A., Weyer, S., and Viehmann, S.: An evaluation of phases in banded iron formation of the 3.25 Ga Fig Tree Group (Barberton Greenstone Belt) suitable as a seawater archive , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11051, https://doi.org/10.5194/egusphere-egu26-11051, 2026.

There is a growing need within the paleoclimate community for robust soil paleoproxies capable of reconstructing past terrestrial environments with high precision. Existing proxies for past mean annual air temperature (MAT), such as branched GDGTs (1) and chironomids (2), suffer from large uncertainties (i.e., ≥ 4°C error on these land temperature reconstructions), which limit their applicability.

Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoid membrane lipids produced by bacteria that are ubiquitous in terrestrial and aquatic environments (3). Functionalized BHPs have a large structural diversity both in the rings and head groups. They have been detected in sedimentary archives extending back 1.2 Myr (4), underscoring their considerable potential as tools for reconstructing past climatic conditions.

BHPs with nucleoside (adenosyl and inosyl) head groups (Nu-BHPs) have been widely used as indicators of terrestrial organic matter input into marine systems (Rsoil) (5). Recently, a large range of previously unknown Nu-BHPs were identified thanks to a newly developed method using Ultra High Performance Liquid Chromatography – high resolution Orbitrap Mass Spectrometry (6). The relative abundances of several Nu-BHPs found in Alaskan soils were shown to correlate with pH and temperature and thus are potential paleotemperature proxies (7). To validate these correlations on a global scale, we present Nu-BHP abundances analyzed across 89 globally distributed surface soil samples. These include soils previously used to calibrate branched GDGTs (1), as well as soils from Northern Norway and Finland and Brazil, to complete coverage from the Arctic to the tropics. Complementary analyses included six soil environmental variables (pH, latitude, total organic carbon (TOC), C/N, δ¹³C, δ¹⁵N) and four climate parameters (mean annual and warmest quarter air temperature, obtained from CHELSA climatological data (8), annual and wettest quarter precipitation, retrieved from the Copernicus Climate Change Service (9)).

Forty-eight Nu-BHPs were identified in soils with a pH range of 3.3-8.1 and total organic carbon (TOC) range of 0.2 and 48.4%. The most dominant compound in the dataset is adenosylhopane with 0 methylations. Of the forty-eight Nu-BHPs, thirty compounds were present in trace amounts (less than 1% of total relative abundances). The remaining eighteen Nu-BHPs were further used to investigate climatic controls on Nu-BHP abundances.

This showed that only a few Nu-BHPs showed a good correlation with pH (R² ~0.65), while temperature did not appear to influence Nu-BHP distributions. Non-metric multidimensional scaling analysis was conducted on relative abundance of these eighteen Nu-BHPs, along with the soil environmental variables and climate parameters (Fig. 1).  This revealed that none of the measured parameters measured fully explains the variability in Nu-BHP distributions. We hypothesize that the main control factors instead are related to nutrient availability and/or bacterial community diversity. Future work includes investigating these variables using samples with strong nutrient and pH gradients; and known bacterial community abundances.

 References

• Weijers et al., 2007.
• Brooks et al., 2001. 
• Cooke et al., 2009. 
• Zhu et al., 2011.
• Talbot et al., 2014. 
• Hopmans et al., 2021. 
• O’Connor, 2025. 
• Krager et al., 2017. 
• Dorigo et al., Copernicus Climate Change Service (C3S) Climate Data Store (CDS).

How to cite: Novik, O., Schouten, S., Chen, Y., Berke, M., Gleixner, G., Mackay, H., van der Meer, M., Hopmans, E., and Rush, D.: Investigating the controlling factors of nucleoside bacteriohopanepolyol abundances in soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11598, https://doi.org/10.5194/egusphere-egu26-11598, 2026.

Carbonates are widely used as paleoenvironmental archives because they record past environmental conditions through their chemical and isotopic signatures. However, primary crystallization processes and subsequent diagenetic alterations can modify these signatures, potentially affecting their reliability as paleoenvironmental proxies.

This study investigates isotopic changes during the precipitation of amorphous calcium carbonate (ACC) into crystalline CaCO₃ under variable pH and temperature (T) conditions, in order to better constrain the role of ACC in calcification processes and its influence on the final isotopic composition of the crystalline carbonate polymorphs. ACC was synthesized by automated titration of an equimolar CaCl₂ solution into NaHCO₃ (+NaOH) solutions. A first set of experiments was conducted over a pH range of 8–11 and at temperatures of 10, 20, and 30 °C. A second set was performed at pH 8 and T of 10, 20, and 30 °C in the presence of polyaspartic acid (pASP) to simulate biomineralization effects on ACC metastability and its transformation to crystalline CaCO₃ polymorphs. Precipitates were characterized using scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and in-situ Raman; oxygen and carbon isotope ratios were measured by isotope-ratio mass spectrometry.

The onset of vaterite precipitation from ACC occurs rapidly at all investigated pH and T conditions, with transformation times less than 1 min. In the presence of pASP, ACC is stabilized and crystalline phase precipitation is delayed to 5 min. The transformation of ACC into calcite is strongly T dependent, with shorter transformation time periods at higher T for all pH conditions. Spherulitic ACC size is strongly controlled by pH and T, decreasing from ~0.25 µm at pH 8 and 10 °C to ~0.10 µm at pH 11 and 30 °C.

For all investigated temperatures and pH conditions, oxygen isotope values of the initial ACC (e.g. at 10 °C and pH 8: δ¹⁸O_VPDB = –4.94 ‰) decrease during CaCO₃ precipitation, reaching lower values in the resulting calcite (e.g. δ¹⁸O_VPDB = –6.10 ‰), with values systematically decreasing with increasing T and pH. In contrast, carbon isotope values are comparatively more constant, showing only limited differences between ACC and crystalline phases (e.g. at 10 °C and pH 8, δ¹³CVPDB= –3.99 ‰ for ACC and –4.95 ‰ for calcite). This relative stability reflects the weaker temperature dependence of carbon isotope fractionation and the dominant control exerted by pH on dissolved inorganic carbon (DIC) speciation, sensitive to pH variations.

Oxygen and carbon isotope equilibrium between carbonate phases and the initial reactive water is variably approached depending on pH, T, and mineral phase. At high pH (≥10) and elevated T, isotopic equilibrium is not reached for ACC and the resulting crystalline phases due to rapid precipitation and transformation kinetics that limit isotope exchange with the aqueous phase. Lower pH and moderate T favor closer approach to equilibrium, whereas low water/solid ratios and the presence of pASP promote isotopic disequilibrium by limiting recrystallization-driven exchange.

These results highlight the potential for kinetically controlled isotopic signatures in carbonates formed via amorphous precursors, with implications for paleoenvironmental interpretations.

How to cite: Pace, A., Pettauer, M., Dietzel, M., Auer, G., and Asta, M. P.: Effect of pH and temperature on oxygen and carbon isotope fractionation during ACC transformation to crystalline carbonates., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12194, https://doi.org/10.5194/egusphere-egu26-12194, 2026.

Constraining the weathering history of the British Isles in the Cenozoic is limited by the sparse distribution of terrestrial rock units of appropriate age.  This has prompted many workers to rely on examination of the regional marine record to make inferences about terrestrial weathering and climate in this era.  We have begun a project to date supergene mineral deposits across the region to provide direct temporal information about the timing and extent of weathering processes.  We show first results of dating with the ⁴⁰Ar/³⁹Ar technique on cryptomelane (KMn8O16) from Scotland, suggesting a late Miocene age.  A full sample suite from across Great Britain and Ireland is currently being analysed.

In addition to dating of cryptomelane and other Hollandite group minerals, the NEIF argon isotope laboratory at SUERC has developed the capability of dating difficult hydrous sulphate minerals alunite and jarosite that occur across the region and will be the subject of future weathering studies. Sample preparation remains a challenging aspect of dating supergene minerals.  This is because of the fine-grained nature of the material coupled with the intergrowth of potentially complicating phases such as clay, feldspar or quartz.  HF leaching of materials to remove silicate impurities have shown promise, suggesting a reduction in the budget of trapped atmospheric argon, and reproducible ages have been obtained for samples as young as Pleistocene.  Attempts at micro-sampling, for example, growth layers in cryptomelane using microdrill techniques, have met with limited success.  Future work will look at laser micro-sampling coupled with high precision and high sensitivity ⁴⁰Ar/³⁹Ar analysis on the next-generation THERMO ARGUS VI mass spectrometer.

How to cite: Barfod, D. and Pickersgill, A.: Progress on supergene mineral dating utilising the 40Ar/39Ar technique and terrestrial weathering in Great Britain & Ireland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12719, https://doi.org/10.5194/egusphere-egu26-12719, 2026.

Evaporites are rarely recorded in the Precambrian. In the oldest rocks they are known mostly from pseudomorphs of salt minerals, or can be inferred from other sedimentary and geochemical features. Only in some younger rocks are they present as salt minerals.

About 50 inferred or definitive occurrences of evaporites in Archean through Mesoproterozoic rocks were compiled. These data allow characterisation of the mineralogy and sedimentary environments of the earliest evaporite sediments and insight into their evolution over time.

The earliest documented evaporites are from the Archean eon, with about 15 occurring mostly in the Paleoarchean (3.6–3.2 Ga) and Neoarchean era (2.8–2.5 Ga). 

The earliest Paleoarchean deposits considered as „evaporitic” in origin are bottom-grown barite crystals, formerly interpreted as pseudomorphs after gypsum, and silica pseudomorphs after radiating splays of aragonite in North Pool Chert of the Dresser Formation (3.48 Ga old), Australia. Barite and aragonite presumably crystallized in a volcanic caldera evaporitic basin from brine of both hydrothermal and seawater derivation. However barite, unlike aragonite, cannot be classified as an evaporite mineral due its very low solubility. The other Palaeoarchean evaporites are represented mostly by enigmatic pseudomorphs (after possible gypsum, aragonite, nahcolite, halite, and others). The Archean evaporite crystals are interpreted as precipitated in both marine and non-marine environments, including soils or weathering zones where they could represent terrestrial or pedogenic evaporites.

In the Proterozoic eon the most frequent occurrences are from the Paleoproterozoic (Rhyacyan, Orosirian and Statherian; 2.3–1.6 Ga). Their appearance directly follows the beginning of the Great Oxidation Event in Siderian at about 2.4 Ga. The first abundant evaporites, with mineralogy similar to the present-day marine evaporites (carbonates, Ca-sulphates, halite, and KMg sulphates), appear in the Mesoproterozoic and include several saline giants (evaporites with volume ≥ 1000 km³). The oldest ones are: a) 2.31 Ga old Gordon Lake Formation, Canada, and Kona Dolomite, USA, b) ca 2.0 Ga old Tulomozero Formation, Onega Basin, Karelian craton, Russia (with preserved KMg salts), c) 2.1 Ga old Juderina Formation, Yilgarn craton, Australia. They strongly suggest appearance of marine water very similar to the modern ocean water.

Information about evaporite minerals from the Archean era is uncertain and ambiguous, coming from enigmatic pseudomorphs and geochemical signals. This evidence originates from sedimentary environments that are not widely recognised, including marine, terrestrial, hydrothermal and/or lacustrine environments. Such evidence does not provide a basis for unambiguously characterising the composition of Archean seawater.

How to cite: Kremer, B. and Bąbel, M.: Evidence and significance of the oldest Paleoarchean to Mesoproterozoic evaporites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14831, https://doi.org/10.5194/egusphere-egu26-14831, 2026.

The Cambrian Sauk transgression marks one of the most extensive episodes of marine inundation in Earth’s geological record. Despite its importance, accurately constraining its timing remains problematic in many regions because of limited biostratigraphic indicators and the scarcity of robust chronometric tools. In this study, we introduce an integrated petrographic, geochemical, and geochronological framework to constrain the age of the Sauk transgression on the southeastern Arabian Plate. This is achieved through analysis of trace-fossil burrows developed along the Cambrian maximum flooding surface (Cm20 MFS) within the middle Miqrat Formation of central Oman. Microscopic examination shows that calcite cement infilling the burrows is characterized by a drusy crystal fabric and occupies loosely arranged framework grains, indicating early cementation under near-surface conditions soon after sediment deposition. This interpretation is corroborated by clumped isotope (Δ47) data, which indicate calcite precipitation temperatures between 33.8°C and 36.4°C, with a mean value of approximately 34.8°C. These temperatures align well with independently estimated middle Cambrian sea-surface conditions. Measured Sr87/86 ratios of the burrow-filling calcite range from 0.7088456 to 0.7090134 (mean 0.7089270), yielding an inferred age of approximately 508.20–509.86 Ma, with an average age of 509.26 Ma. This age assignment falls within the middle Cambrian and is marginally younger than the maximum depositional age of ~511 Ma obtained from detrital zircon analyses. The ages reported here represent the first direct numerical constraints on the Sauk transgression from the southeastern Arabian Plate and demonstrate consistency with equivalent ages documented from the northern and northwestern parts of the plate. Overall, the results highlight the effectiveness of Sr87/86 isotope analysis of early diagenetic calcite as a chronostratigraphic tool. Because such calcite precipitates from marine-derived fluids shortly after deposition, it faithfully records the seawater isotopic composition at the time of cementation, allowing reliable dating of sedimentary successions.

How to cite: El-Ghali, M., Moustafa, M., Ahmed Abbasi, I., Shelukhina, O., Salad Hersi, O., and Ali, A.: Timing the Cambrian Sauk Transgression in the Southeastern Arabian Plate: Evidence from Radiogenic Strontium of Early Calcite Cement, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16562, https://doi.org/10.5194/egusphere-egu26-16562, 2026.

The geochemical signatures of clastic sedimentary sequences are determined by the parent rocks, weathering intensity, and the complex processes of transport and deposition. These variables define the mineralogical and chemical attributes of the basin fill, offering significant insights into the prevailing geodynamic settings and paleoclimatic conditions. The Upper Cretaceous deposits in the Lesser Caucasus are widely distributed and represent a vital geological archive for studying the region’s history. To reconstruct the paleogeographic and depositional conditions of the northeastern slope of the Lesser Caucasus, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was employed for high-precision elemental analysis, while X-ray diffraction (XRD) was utilized to determine the mineralogical composition of the sequences. The terrigenous sequences of the region comprise the diverse lithological assemblages, primarily categorized as shales, iron-rich shales (Fe-shales), and greywackes. These rocks exhibit low compositional and mineralogical maturity, indicating accumulation in high-energy environments with a significant influx of fresh volcaniclastic material. Geochemical proxies for chemical weathering reveal a transition from intensive to moderate alteration. This low maturity is further substantiated by the preservation of primary silicates, which is characteristic of rapid sediment burial. Elemental analysis indicates that the detrital material was predominantly derived from first-cycle mafic and ultramafic magmatic sources, reflecting the significant erosion of ophiolitic and associated sequences. Geochemical indicators confirm a first-cycle sedimentary regime with minimal recycling and limited hydraulic sorting. Tectonic discrimination functions identify an oceanic island arc setting, where volcaniclastic and terrigenous debris accumulated in basins governed by active subduction and convergence processes. These findings are consistent with semi-humid and semi-arid paleoclimatic conditions that prevailed during the Late Cretaceous. Collectively, these indicators elucidate the geodynamic setting of the region and emphasize the interplay between arc volcanism and the regional tectonic framework in shaping the Mesozoic sedimentary record.

How to cite: Guliyev, E. and Aliyeva, E.: Geodynamic and paleogeographic settings of the Upper Cretaceous terrigenous successions, northeastern slope of the Lesser Caucasus: Geochemical and mineralogical constraints , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16974, https://doi.org/10.5194/egusphere-egu26-16974, 2026.

Benthic foraminifera are widely considered as marker proxy for past changes in surface and deep water productivity, organic matter flux, bottom water oxygenation, and deep water circulation. This study presents benthic foraminiferal relative abundance records from ODP Site 1087 (31°27.9137’S, 15°18.6541’E, water depth 1374m), located in the southeast Atlantic Ocean beneath the productive Benguela Upwelling System (BUS). The main objective is to assess long-term productivity and oceanographic variability in the region from the Late Miocene to Pleistocene. Our results indicate a major shift in regional oceanographic conditions at ~10 Ma. A distinct increase in the relative abundance of Bulimina striata, a dysoxic, infaunal species associated with elevated flux of organic matter, suggests enhanced surface productivity and marks the emergence of the BUS. This timing closely matches with the onset of the BUS as inferred from multiple independent proxy records. The late Miocene–early Pliocene biogenic bloom (~ 8–5 Ma), characterised by sustained and widespread high productivity across the Indian, Pacific and Atlantic Oceans, is often indicated by higher relative abundance of Uvigerina proboscidea, a suboxic, infaunal species associated with high delivery rates of organic matter to the seafloor. A similarly higher relative abundance of U. proboscidea is clearly recorded in our benthic assemblages, pointing to intensified export productivity during this interval. Additionally, an increased relative abundances of the opportunistic species Epistominella exigua during ~8 to 6 Ma and ~3.7 to 3.0 Ma indicate seasonal input of phytodetritus from the surface waters due to extensive phytoplankton blooms associated with the strengthening of the upwelling. The early Pliocene interval between ~5 and 3.7 Ma is marked by the co-occurrence of Globocassidulina subglobosa, U. proboscidea, and B. striata. This assemblage reflects alternating oxic and suboxic–dysoxic benthic environments, which might be linked to oligotrophic and eutrophic surface conditions, respectively. Decreased surface productivity related to reduced upwelling and enhanced oxygenation of bottom waters favoured oxic species, but the continued presence of dysoxic-suboxic species indicate a continuous nutrient supply, perhaps related to Agulhas Leakage. A rapid increase in U. proboscidea and Uvigerina peregrina during the Plio–Pleistocene cooling reflects re-intensification of BUS-related productivity. Overall, benthic foraminiferal assemblages at ODP Site 1087 provide a robust record of productivity and associated oceanographic changes in the Southeast Atlantic Ocean between the Late Miocene and Pleistocene.

How to cite: Mohanty, R. N., Gupta, A. K., and Majumder, J.: Late Miocene to Pleistocene deep water Productivity in the Southeast Atlantic: Evidence from Benthic Foraminiferal Assemblages, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18474, https://doi.org/10.5194/egusphere-egu26-18474, 2026.

The Zr/Hf ratio of modern seawater (150-300¹) is significantly fractionated relative to the chondritic value (32.7-34.2²) and magmatic systems. This deviation is driven by the higher particle reactivity of Hf relative to Zr in low-temperature, aqueous systems, resulting in preferential sorption of Hf onto (particle) surfaces. The Zr/Hf ratio of aqueous systems increases from the continents towards the open oceans, varies with water depth and water mass age, making it a powerful tool for tracing water masses. While reasonably well constrained in modern aquatic systems, the Zr/Hf composition of ancient seawater remains poorly understood, but may provide unique insights into the circulation of water masses.

To investigate the Zr/Hf evolution of the seawater throughout Earth’s history, banded iron formations (BIFs) represent a viable archive for the Precambrian seawater chemistry because they are chemical sedimentary rocks and reflect the chemistry of the seawater from which they precipitated. Here, we present new high-precision Zr–Hf data from Precambrian BIFs, complemented by available literature data, to evaluate the Zr/Hf ratio as a paleoceanographic tracer of ancient water masses.

Archean BIFs predominantly display near-chondritic Zr/Hf ratios, with ratios not exceeding 75. The first super-chondritic Zr/Hf ratios occur in individual BIF-layers at ~2.51 Ga, and the formation showing overall super-chondritic Zr/Hf ratios is the ca. 2.4 Ga Hotazel Formation, indicating widespread Zr/Hf fractionation in marine environments. Formation-scale averages largely remain near-chondritic until ~2.0 Ga, while younger BIFs show predominantly super-chondritic ratios. This secular trend from chondritic towards super-chondritic Zr/Hf ratios in the early to mid Proterozoic likely reflects changing seawater conditions that enabled widespread Zr–Hf fractionation. The increasing availability of Fe–Mn(oxide) particles, based on increasing atmospheric oxygenation but also the progressive development of modern-style estuarine and shelf environments, may have led to global Zr-Hf fractionation in marine systems by that time. Within individual formations, Zr/Hf ratios correlate with Mn/Fe ratios, indicating a link between Zr-Hf fractionation and the redox-evolution of the Earth. Moreover, regional differences among coeval BIFs suggest variable depositional settings and distinct water-mass circulation patterns already in the Neo-archean. Thus, our results highlight the potential of Zr/Hf ratios in BIFs and other chemical sedimentary rocks to trace the redox-evolution of the Earth with the appearance and spatial heterogeneity of oxygenated water masses in Early Earth oceans.

 ¹Godfrey et al., 1996, GCA 60

 ²Münker et al., 2025, GPL 36

How to cite: Krayer, J., Ravindran, A., Pakulla, J. J., Münker, C., Weyer, S., and Viehmann, S.: Zr/Hf ratios in Banded Iron Formations as tracers of Early Ocean evolution , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18713, https://doi.org/10.5194/egusphere-egu26-18713, 2026.

In many carbonate archives, Δ₄₇ signatures appear to be primarily driven by crystallization temperatures, with little evidence for other influencing factors, implying that ¹³C and ¹⁸O isotopes are effectively (re)distributed among carbonate isotoplogues in accordance with thermodynamic stability during or just before mineralization. This is not the case for all types of carbonates, but appears to hold true for biocarbonates such as bivalves, gastropods, or planktic foraminifera. For historical reasons, things are not as clear-cut when it comes to benthic foraminifera, a particularly important source of information on past marine environments at the scale of the Cenozoic and beyond. In hope of fostering productive discussions, we revisit this issue with a focus on the following questions:

• What is the current body of evidence from modern/recent observations?
• How much do the various Δ47 calibrations currently applied to foraminifera differ?
• Is there any practical difference between Δ47 calibrations based exclusively on modern/recent foraminifera and "composite" calibrations based on many different types of carbonates?
• What should be the foraminifer Δ47 community's next steps to try and resolve these issues?

How to cite: Daëron, M. and Gray, W.: Does it matter whether benthic foraminifera achieve clumped-isotope thermodynamic equilibrium?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19790, https://doi.org/10.5194/egusphere-egu26-19790, 2026.

The rare earth elements (REE) are transported and transformed coherently in the environment, yet subtle differences in their chemical properties cause variable fractionation patterns. In the ocean, their relatively long residence times (centuries to millennia) allow REE to be advected across basins while recording fractionation processes en route. Scavenging onto sinking particles – especially metal oxides and organic matter – leads to their burial on the seafloor, where their abundances can be further modified by early diagenetic processes. The fraction of REE preserved in sediments enters the geological record where it can be used to reconstruct past ocean chemistry provided their marine geochemical cycling is understood well enough.

Here we present REE concentration data from authigenic phases of a global suite of marine sediments. We assess which environmental parameters they predominantly relate with, how early diagenesis affects the archived REE, and whether authigenic REE can be used to reconstruct past ocean chemistry and particle fluxes.

How to cite: Blaser, P., Monedero-Contreras, R., Scholz, F., Jaccard, S. L., and Frank, M.: Rare Earth Elements as tracers for past ocean chemistry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20576, https://doi.org/10.5194/egusphere-egu26-20576, 2026.

Cryogenic cave calcite is a relatively rare type of cave deposit formed in periglacial environments by drip water freezing and discharging its soluble components in form of mostly calcium carbonates. While cryogenic calcite formation as a phenomenon was recognized early on by researchers (see [1,2] for references), most studies to date have focused on the morphological characteristics of these deposits or their stable isotope composition.

In this contribution we investigate the elemental and stable isotopic composition of cryogenic cave carbonate deposits (pearls) from the Scărișoara Ice Cave, Romania. The pearls were collected from within the cave at locations where active drip water was present. Samples (millimeters to centimeters in diameter) were embedded in epoxy resin, cut in half and the exposed surface was analyzed. Laser ablation inductively coupled mass spectrometry (LA ICP TOF MS) was used to identify the qualitative distribution of trace elements that can we expected to reach the cave from atmospheric deposition above the cave, rather that from the bedrock. A Teledyne Photon Machine 193 nm wavelength excimer laser Iridia was used in conjunction with Nu Instruments Vitesse time-of-flight ICP MS for elemental mapping. Stable isotopic (δ¹³C and δ ¹⁸O) composition was explored using laser ablation isotope ratio mass spectrometry (Photon Machines Fusions CO2 laser coupled to a Sercon HS2022 IRMS).

Elemental data shows highly zoned structures in the studied deposits. Layers of clear detrital input (characterized by high 89Y and low ⁴⁸Ca⁺/²⁸Si⁺) alternate with layers with monotonous chemical composition. Furthermore, the layers of detrital input are often characterized by the presence of 3–5 micron Au-containing particles. We believe those particles to be anthropogenic pollutants windblown from areas with historically intense Au mining located in relative proximity of the cave. 

[1] I.D. Clark, B. Lauriol, Kinetic enrichment of stable isotopes in cryogenic calcites, Chem. Geol. 102 (1992) 217–228.

[2] K. Žák, B.P. Onac, A. Perşoiu, Cryogenic carbonates in cave environments: A review, Quat. Int. 187 (2008) 84–96.

How to cite: Pușcaș, C. M., Stremțan, C. C., Perșoiu, A., and Schlatt, L.: Elemental mapping and stable isotope analyses of cryogenic cave carbonates from Scărișoara Ice Cave, Romania, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21375, https://doi.org/10.5194/egusphere-egu26-21375, 2026.

The mechanisms that allowed the oxygenation of the Earth’s atmosphere to occur at the end of the Archean, an event known as the Great Oxidation Event (GOE), remain unclear. For the GOE to occur, two conditions must be met: first, oxygenic photosynthesis must evolve; second, the net production of dioxygen by photosynthesizers (i.e. the imbalance between carbon fixation and respiration corresponding to burial of organic matter), must exceed oxygen sinks such as reduced volcanic gases. Evidence points toward oxygenic photosynthesis evolving long before the traces of the GOE appear in the geological record. Thus, the oxygenation of Earth’s atmosphere may have been triggered by a combination of an increase in the burial flux of organic carbon (net O2 source) or a decreased O2 sink (e.g. via a decrease in the volcanic emissions of reduced gases). However, the drivers and dynamics of each of these processes are complex, and leveraging the geological record (e.g. stable carbon isotope record) to draw mechanistic conclusions about geochemical cycling at the time of the GOE remains challenging.

Recent modeling studies have highlighted the role of ecological competition for nutrient between anoxygenic and oxygenic photosyntheses as a potential driver for a delayed oxygenation of the atmosphere following the emergence of oxygenic photosynthesis (Ozaki et al 2019; Olejarz et al 2021). Here, I use adaptive dynamics theory (Metz et al., 1992) to rigorously and efficiently model the outcome of ecological competition in the upper layer of the Archean ocean as a function of boundary conditions set by the compositions of the deep ocean and of the atmosphere. Using a separation of timescales assumption, I then use the steady-state outcome of this ecological model as a boundary condition in a simplified geochemical model of phosphorous and iron cycling, and atmospheric oxygen.

The model shows how small perturbations in the delivery rate of iron or phosphorous to the deep ocean can trigger reversible or irreversible global oxygenation events. I examine a scenario where the upper ocean is initially phosphorous-limited and photoferrotrophs (anoxygenic photosynthesis where the electron donor is soluble iron) competitively exclude oxygenic photosynthesis. Then I assume that delivery rates of iron and phosphorus evolve or are perturbed such that the upper ocean transitions to conditions where photoferrotrophs would be iron-limited, giving oxygenic photosynthesis a fitness advantage (owing to its use of abundant water as an electron donor). In this scenario, an initially rare variant performing oxygenic photosynthesis may take come to dominate phototrophic primary production while the total remains constant, if local oxidation of soluble iron by dioxygen is fast enough (i.e. if the pH is high enough). The model demonstrates that coexistence between anoxygenic and oxygenic photosyntheses may not prevent oxygenation of the atmosphere, if the total productivity is high enough, and determines conditions where small perturbation in the geochemical system can trigger reversible or irreversible atmospheric oxygenations.

How to cite: Affholder, A.: Eco-Evolutionary dynamics of oxygenic and anoxygenic photosyntheses in the late Archean., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21473, https://doi.org/10.5194/egusphere-egu26-21473, 2026.

Banded Iron Formations (BIFs) are important archives of early Earth's history, offering critical geochemical insights on Archaean oceanic and atmospheric chemistry. BIFs provide critical constraints on ancient seawater conditions, temperature, pH, nutrient cycles, redox processes and the evolution of microbial metabolisms, which are fundamental to understanding early planetary habitability. In the Singhbhum Craton of India, their immense economic importance has made BIFs a primary research target for decades.

But so far, the different BIF units exposed within the Singhbhum Craton remain yet to be dated and characterized. Numerous BIF units are distributed within the Singhbhum Craton, which holds immense potential to unravel deep insights into not only seawater chemistry but also conditions related to the emergence of the craton and/or presence of terrestrial landmass. Recent studies have placed BIFs exposed in the southern part of the Singhbhum Craton amongst some of the oldest BIFs with evidence for terrestrial inputs around ca. 3.37 Ga. Here, we report ancient BIFs of the Gorumahisani Greenstone Belt that are well exposed near the mining town of Gorumahisani, with alternate banding of Si- and Fe-rich bands and intercalated with cherts. To date, the age of this critical iron formation within the Gorumahisani greenstone sequence remains poorly known. We dated an intrusive granitoid within the BIF sequence. U-Pb dating of zircon crystals recovered from the intrusive granitoid provided a ²⁰⁷Pb/²⁰⁶Pb age of 3286 ± 10 Ma. The emplacement age of this granitoid brackets the minimum age for the Gorumahisani greenstones, and on the other hand, it is identified as part of the Singhbhum Granitoid Complex (i.e., the Singhbhum Suite). Field and geochronological evidence confirms the presence of Palaeoarchaean BIFs in the Gorumahisani belt, establishing a critical foundation for future studies to determine precise depositional constraints and unravel details of early Earth surface processes.

How to cite: Jodder, J. and Elburg, M.: Banded Iron Formation of the Gorumahisani Greenstone Belt, Singhbhum Craton, India: Insights into Archaean surface processes., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21888, https://doi.org/10.5194/egusphere-egu26-21888, 2026.

The Azores Front marks the boundary between subtropical and
subpolar water in the North Atlantic. Its position during glacial periods
is debated, tracing it would improve our understanding of glacial ocean
circulation. Neodymium (Nd) isotopes are an important tracer for past and
current water mass mixing. They are however subject to overprinting on
local scales by processes including erosion and volcanic activity.
Cold-water corals incorporate Nd into their skeletons without
fractionation, making them valuable archives. In this work, the epsilon-Nd
of corals from several locations close to the Azores Islands was measured.
The corals were previously dated by U/Th measurements, which revealed ages
between 0.458 and 22.14 ka. The epsilon-Nd measurements found a range of
values between -12.07 and -1.26. The results reveal clear
evidence of radiogenic overprinting, which occurs on decadal timescales
and can most likely be attributed to volcanic activity. The extent and
frequency at which this overprinting occurs does not depend on climate
phases. A part of the samples may represent unaltered seawater values,
these show no evidence of a change in water mass mixing over the last 20
ka.'

How to cite: Schöfer, C. and Frank, N.: Epsilon-Nd-Signatures and Radiogenic Overprinting in Cold-Water Corals near the Azores, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22506, https://doi.org/10.5194/egusphere-egu26-22506, 2026.

Mercury (Hg) is a volatile toxic metal with strong atmospheric mobility, making its biogeochemical cycle highly sensitive to climate change. A key challenge is distinguishing natural climate-driven variability from anthropogenic impacts. This study examines how colonisation and climate change have shaped Hg contamination across the Australia–Pacific region. Previous work shows increasing Hg deposition in remote environments since the colonial era. Here, we apply a multi-proxy framework—combining Hg isotopes, geochemistry, and robust chronologies derived from radiocarbon, lead-210, and plutonium dating—to lake sediments from southern Australia and sub-Antarctic islands (Macquarie and Campbell). These records allow us to separate long-range transport, anthropogenic emissions, invasive animal disturbance, and climate drivers such as the southern hemisphere westerly winds. By integrating isotopic, geochemical, and age-model data, we quantify Hg sources and accumulation rates, providing new insights into Hg cycling in lacustrine ecosystems under changing climate conditions.

How to cite: Schneider, M., Schneider, L., Saunders, K., Latimer, J., Roberts, S., Child, D., Fallon, S., Haberle, S., and Sun, R.: Pollution history and colonial-induced increase in the transport of mercury from Australia to Sub-Antarctic islands: using mercury isotopes to trace the source, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-316, https://doi.org/10.5194/egusphere-egu26-316, 2026.

The past century of increases in human population and resource consumption has produced some undesirable effects, ranging from environmental degradation to political unrest. We are accustomed to seeing these dependent variables charted with time on the x-axis. But this study presents metrics of biodiversity, consumption, and pollution and their extremely strong correlations when charted against human population size. Then we suggest that a more rapid yet non-coercive lowering of global Total Fertility Rates to 1.75 by 2050, and holding there, will produce many benefits for current and future generations of our own species and for nature. Among these benefits are reduced CO2 emissions, habitat recovery, protection of wild species, reduction of poverty, and reduced conflict over scarce resources.

How to cite: Keegan, M.: Gently easing population to 4 billion by 2200 would help people and nature, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1998, https://doi.org/10.5194/egusphere-egu26-1998, 2026.

What Could Geosociology Be? Preliminary Considerations on the Sociology of the Earth

Geosociology represents a fundamental shift in sociological inquiry, moving away from treating nature as an extra-social entity to viewing the Earth and society as a single, entangled reality. This "Sociology of the Earth" is increasingly necessary considering the planetary crises called ‘Anthropocene’, which reveal that social life is deeply embedded in planetary dynamics that shape the atmosphere, continents and oceans. What were exogenous drivers in the Holocene become endogenous processes in the Anthropocene. 

The presentation portrays sociology as a methodological science, drawing a parallel to geology. Much as a geologist observes physical strata, a sociologist observes the "layered" realities of social institutions. This comparison facilitates a dialogue between the two fields as epistemic equals, establishing a foundation for an interdisciplinary field.

Central to this perspective is the anthropological shift. Drawing on Bruno Latour, the text argues that humans must be understood as "terrestrials" or "earthlings." This rejects the modern illusion of human autonomy and acknowledges that social achievements—like urbanisation—are essentially geo-social arrangements. It further builds upon classical schools of thought, for example, Ibn Khaldun, who in his Muqaddimah (1377) observed how specific landscapes and resource availability (such as the contrast between desert and hill dwellers) shape social organisation.

The proposed epistemology of Geosociology navigates the space between social construction and material reality. While Berger and Luckmann famously defined reality as a social construct, Geosociology suggests that geological knowledge is a hybrid: it is mediated by human frameworks but anchored in the independent expedition into the telluric.

The presentation also addresses the linguistic dimension, specifically the use of geological metaphors (e.g., "social tectonics") to convey broader concepts, such as ‘deep time’. While these tools help visualise complexity, Geosociology insists on critical reflection on whether they illuminate realities or merely aestheticize social matters. As Markus Schroer (2022) suggests, sociology must venture beyond the humanities into biology and geology to go beyond such metaphors and learn how to keep constant contact with reality.

The multifaceted notion of the Anthropocene serves as the pivotal diagnostic tool, demonstrating that human activity has become peers with geological forces. This realisation challenges Ludwig Wittgenstein’s notion of the world as "everything that is the case" by asking whether the Earth's facticity carries ethical weight.

Finally, inspired by Auguste Comte’s dictum that science leads to foresight, Geosociology looks toward the future. It even touches on "extraterrestrial sociology," citing Cixin Liu’s novel The Dark Forest, which posits that, as civilisations grow, the quantity of matter remains constant. Hence, ultimately, the recently coined neologism Geosociology integrates deep-time perspectives with social action, for intra- and extra-terrestrial Earthlings.

Literature:

Berger / Luckmann: The Social Construction of Reality, 1991

Cixin Liu: The Dark Forest, 2015

Comte: Cours de philosophie positive, 1830

Grutzpalk: Strong Metaphors for Invisible Actants, 2016

Ibn Khaldun: Al Muqaddimah, 1377

Latour: Où suis-je ?: Leçons du confinement à l'usage des terrestres, 2021

Schroer: Geosoziologie, 2022

Wallenhorst / Wulf: Encyclopedia of the Anthropocene, 2024

Wittgenstein: Tractatus logico-philosophicus, 1921

How to cite: Grutzpalk, J. and Bohle, M.: What Could Geosociology Be? Preliminary Considerations on the Sociology of the Earth, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3965, https://doi.org/10.5194/egusphere-egu26-3965, 2026.

The planetary boundaries (PBs) represent key Earth system processes and their safe limits to maintain planetary resilience and stability. The 2023 assessment reflects that the Earth has transgressed six of nine boundaries while the 2025 Planetary Health Check indicates that a seventh has been breached. Given that human pressures are driving these transgressions, guidance is needed for translating planetary-scale limits into decision-relevant inputs for local actors. Sustainability reporting standards provide business organizations with guidelines for disclosing their impacts but often do not require benchmarking against the PBs. Interactions across disclosure categories are also not captured in target-setting. Tools are needed to help organizations assess their performance while bridging local pressures to planetary impacts.

To this end, Lade et al. (2021) formulated a prototype Earth System Impact (ESI) metric which enables evaluations of an organization’s systemic impacts on climate, land, and water in relation to the 2015 PBs translated into sub-global guardrails. Interaction strengths for climate, land and water at the sub-global scale were derived from 1901-2013 simulations from a dynamic global vegetation model, LPJmL4. Feedback modeling was applied to estimate the impacts of pressures given these interaction strengths and to determine the extent to which pressure in one component of the Earth system is amplified into impacts in other components. Final ESI scores were produced by weighting impacts on climate, land and water with current state as of 2013 to account for existing degradation.

We present an update to the ESI which uses LPJmL5 simulations from 1901-2023 to estimate interaction strengths. Sub-global clusters were updated to include dominantly barren land types in additions to forests and grasses. We then draw from both the 2023 PBs and the 2025 Earth Commission safe and just Earth-system boundaries to develop sub-global guardrails. For water, we set guardrails for both wet and dry deviations from a preindustrial baseline. Current conditions are updated to 2023.

Overall, amplification of impacts increased compared to the prototype, largely due to how all runoff deviations are considered adverse. Notably, the effects of deforestation on the earth system are doubled to tripled. Most barren land experienced no net amplification except in Australia and Africa (~39% and 65%, respectively) where surface water scarcity is aggravated.  The final ESI metrics were higher in smaller areas (e.g. C3 grass ecosystems in Africa), indicative of the sensitivity of smaller ecosystems to anthropogenic pressures compared to the relative resilience of larger intact land with greater surface water availability. Insights from the ESI metrics can aid businesses, investors, and potentially the public sector in planning future developments by providing a basis for comparing impacts of assets in different sites globally beyond just carbon emissions. The ESI can help with setting site-specific targets for environmental performance that are aligned with sub-global guardrails, and, in this way, facilitate a shift towards a “business within boundaries” paradigm that supports sustainability transformations.

Lade, S. J., Fetzer, I., Cornell, S. E., & Crona, B. (2021). A prototype Earth system impact metric that accounts for cross-scale interactions. Environmental Research Letters, 16(11), 115005.

How to cite: Gotangco Gonzales, C. K., Lade, S., Amellina, A., Chuadhary, N., Crona, B., Fetzer, I., Fiedler, T., Marone, D., Parlato, G., Rocha, J., Wang Erlandsson, L., and Zoller, H.: An updated Earth System Impact metric for bridging sub-global pressures and planetary boundaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4590, https://doi.org/10.5194/egusphere-egu26-4590, 2026.

In the early 2000s, the Anthropocene was proposed by Paul J. Crutzen, Nobel Prize winner in chemistry and Earth system scientist, as a new geological epoch dominated by human activities and a new noosphere yet to come (Crutzen et Stoermer 2000; Crutzen 2002). In this sense, the Anthropocene Working Group was created in 2009 to try to get the Anthropocene officially recognized within the geological time scale. (Zalasiewicz et al. 2008; 2019). Since then, controversy surrounding its work has continued to grow within the natural and social sciences, culminating in its rejection by geological institutions in March 2024 (International Union of Geological Sciences (IUGS) 2024). 

What should be done with this concept, given its rejection? What research review can be drawn from the debates on the subject? And how can we continue to foster dialogue between disciplines in order to meet the vital challenges of this new epoch?

The aim of this proposal is to show that the Anthropocene requires a new transdisciplinary field of research, which could be called “Anthropocenology.” Far from being based on nothing, this new field could draw on research in Earth system sciences (Steffen et al. 2018), geological sciences (Zalasiewicz et al. 2021), and social sciences (Latour 2017), which accompanied the debates on the Anthropocene. Its ambition would be to continue creating new knowledge networks around the Anthropocene. (Thomas, Williams, et Zalasiewicz 2020), in order to better cope with the disruptions currently occurring from the Holocene Epoch (Wallenhorst et Wulf 2023). More specifically, the latest research on the Anthropocene has made the Great Acceleration a pivotal moment in the trajectory of human civilizations (Head et al. 2022; Syvitski et al. 2020), particularly in terms of the overall transformation of the relationship between science, technology, and society (STS). 

In this sense, this proposal will draw on the latest online debates surrounding the Anthropocene to identify emerging knowledge on the subject. In terms of data, the focus will be on a qualitative and quantitative analysis of several thousand scientific websites and articles, following the methodology of controversy mapping. (Latour et al. 2012; Venturini et Munk 2021). On a theoretical level, the aim will be to identify knowledge, both online and in society, that will enable us to open up a new trajectory and reflexivity within the Anthropocene (Thomas et al. 2020; Wallenhorst et Wulf 2023; Renn 2020; Leinfelder 2024).  

How to cite: Colombo, F.: Toward an Anthropocenology: foresting new networks of knowledge within the Anthropocene., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5770, https://doi.org/10.5194/egusphere-egu26-5770, 2026.

Anthropogenic material fluxes have reached magnitudes comparable to natural biological and geological processes, yet they are rarely addressed within integrated Earth system frameworks. Iron, the most abundantly extracted metal from Earth’s lithosphere, is primarily used for steel production and constitutes a fundamental material basis of modern infrastructure and societal development worldwide. However, data on iron extraction, production, and use remain fragmented across national inventories and are rarely spatially linked to end-use sectors, limiting our ability to assess its role in the Anthropocene Earth system.

Here, we present a new approach based on global technogeochemical flows and apply it to the approximately 2 Gt yr⁻¹ anthropogenic flows of iron. We synthesize disparate datasets using the SESAME gridding tools to demonstrate how iron extracted from a limited number of locations, about 2.3% of global land grid cells, is transformed through a similarly concentrated set of steel production sites, about 2.7% of land grid cells, before accumulating in widely distributed in-use stocks. Using a spatiotemporal, grid-based material flow analysis combined with a tariff-weighted gravity model, we link iron extraction and steel production to end-use sectors at the full planetary scale.

Our results show that Eastern Asia functions as the dominant global locus of iron flows from extraction to in-use, accounting for over 50% of global crude steel production and nearly 44% of total in-use stock accumulation between 2000 and 2016. At the global scale, the network flow models indicate that approximately 2/3 of total mass displacement occur between iron source locations and steel production sites, about 10.4 Tt·km, while 1/3 occurs between steel production and in-use locations, about 5.2 Tt·km. This combined displacement exceeds the total mobility of all human beings by a factor of four.

By explicitly resolving the spatial and temporal interconnections of iron flows, this work advances a systems-based understanding of how industrial economic processes are physically embedded within the Earth system. The approach highlights the uneven spatial distribution of societal pressures and material dependencies that underpin sustainability challenges in the Anthropocene. More broadly, this spatiotemporal framework can be extended to other critical minerals, offering a pathway toward integrative and transformative research on Earth and societies.

How to cite: Faisal, A. A., Kaye, M., and Galbraith, E.: Global Technogeochemical Flows of Iron from Lithosphere to Technosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5854, https://doi.org/10.5194/egusphere-egu26-5854, 2026.

The restoration or ‘rewilding’ of rivers and catchments, which generally involves manipulating biotic drivers, has traditionally used several palaeoecological techniques including plant macrofossils, microfauna and pollen. However, these have well known limitations due to both taxonomic level and indeterminate source-areas. SedaDNA potentially offers partial answers to both of these limitations as well as expanding the organism groups substantially to animals, fish and invertebrates. But in order to fully utilize this new approach we need to understand the taphonomy of sedaDNA so that biases can be assessed and allowed for in any baseline reconstruction. Taphonomy here includes aspects of transport, preservation and bioturbation in the sedaDNA record. In this paper we resolve the spatial input of sedaDNA into a small lake within a small Boreal-zone catchment and the influence of the methodological approach. The taphonomic biases can theoretically come from spatial factors, such variations in sediment connectivity, local environmental factors such as pollution loading, and longer-term variations in sedimentation and land-use. One of the advantages of sedaDNA is that it can record aspects of taphonomy such as the appearance of bioturbating organisms. Notwithstanding this, with comprehensive taxonomic data that is spatially constrained it becomes possible to investigate biotic interactions as well as construct past food webs and ecological dynamics. In this paper we show how sedaDNA metabarcoding can be used to provide an ecological history of key-stone and functionally critical organisms, from a variety of ecosystems and organism groups. These include upland and lowland pasture systems, aquatic plants, mammals, amphibians and fish all of which are part of culturally mediated ecological systems.

This approach is being rolled-out in a new pan-European project on the Molecular Ecology of Medieval European Landscapes (MEMELAND) which aims to provide a 2 millennia evidence based for biocultural restoration in NW Europe from The Arctic Circle to the Alps. The approach utilized here is highly relevant today as it can provide and evidence-base for environmental policies that seek to restore former catchment conditions, promote resilient ecological dynamics and biodiversity.

How to cite: Brown, A. G., Liu, Y., Lang, A., Ataman, T., Hamerow, H., Mottl, O., Dubois, N., and Alsos, I.: The taphonomy of sedaDNA, cultural biodiversity and catchment ecological restoration in North West Europe , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6990, https://doi.org/10.5194/egusphere-egu26-6990, 2026.

The Anthropocene is not only a human-driven geological epoch, as argued by the Earth System Sciences, but also a multi-faceted discourse on socio-ecological relations, as analysed by the social sciences and humanities. Within the Anthropocene discourse, several grand narratives compete for hegemony: The dominant ‘naturalist narrative’ claims that the human species has inadvertently altered the Earth system at a geological scale. The ‘post-nature narrative’ claims that nature is socially constructed and, thus, appropriate technology might tackle the planetary crisis. The ‘eco-catastrophist narrative’ highlights the unsustainable mode of production and consumption that drives the transgression of planetary boundaries towards tipping points. The ‘eco-Marxist narrative’ argues that capitalist elites in the core countries of the world-system accumulated profit and power through unequal economic and ecological exchange with the peripheries, where the resulting social and ecological costs undermine (non-)human habitability. Such highly abstract and complex notions of the Anthropocene can be assessed in a more concrete and simplified manner through the lens of commodities. By following a commodity across time and space, we can gain a broader and deeper understanding of the dynamics of the Anthropocene. As an example, the more-than-human network around soy has gained a broad and deep planetary footprint in the ‘Great Acceleration’ and its aftermaths. A soy-focused history of the Anthropocene – or ‘Soyacene’ – is relevant not only in academic research but also in public debates on the current polycrisis. By highlighting the socio-natural dynamics behind the Earth’s Anthropocene trajectory from a historical perspective, the soy lens gains useful insights for navigating the planetary crisis.

How to cite: Langthaler, E.: Navigating the Anthropocene through a Commodity Lens, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7299, https://doi.org/10.5194/egusphere-egu26-7299, 2026.

The Terai Arc Landscape is a unique subtropical landscape at the foot of the Himalayas, that sustains many keystone species, including the continental tiger (Panthera tigris). Conservation efforts have led to an increase of this species, increasing human-wildlife conflict significantly. To optimize the habitat suitability and reduce conflict, conservationists aim to implement various interventions in Bardia District. However, this ecologically and geomorphologically complex landscape is understudied, making it difficult to estimate the potential impact of different interventions.

Therefore, this study aims to reconstruct past ecosystem states and drivers of  the Bardia landscape to help estimate the outcomes of conservation measures. To achieve this, sediment cores were collected and analyzed for sedimentary ancient DNA, combining shotgun sequencing with mitochondrial mammalian capture, providing a vegetation- and land use history. In addition, the fluvial history of the sampling sites was investigated using grainsize analysis and x-ray fluorescence.

The results from these cores indicate consistent, low-intensity human land use over the last centuries. Only in the last few decades, does the intensity increase, likely due to a confirmed migration wave of people from the hill regions of Nepal to the lowlands after the eradication of Malaria. However, before this, changes in vegetation composition appear more so due to geomorphological change. Namely, one lake is an oxbow lake that was shaped from a past channel of the Karnali river. The combination of past vegetation and fluvial history shows how the severing of the meander from the river led to a fairly fast transition of riverine grassland and forest to a wetland-environment with denser vegetation.

This finding is particularly relevant for Bardia National Park, as the river branch that currently determines its western boundary, the Geruwa, appears to be undergoing a process of disconnection from the Karnali and thus becoming ephemeral or even drying up. Our outcomes show that such a transition can rather quickly affect the presence of riverine grasslands, which are seen as crucial for the tiger, thus affecting habitat suitability. A potential outcome of such a habitat change could be the movement of tigers towards other riverine grasslands nearby, which have a higher human population density, thus increasing the risk of human-wildlife conflict.

One of the interventions proposed by park managers is to artificially keep the Geruwa branch of the Karnali open by removing gravel from blocked channels. This study demonstrates that although this is a somewhat controversial measure, it could actually be desirable in terms of maintaining the tiger population within the National park rather than outside of it. This highlights how assessing past environments can meaningfully contribute to making optimal conservation decisions in challenging contexts.  

How to cite: Kleijwegt, Z., Nota, K., Vernot, B., Atag, G., and Larsen, A.: Past Landscape Dynamics as a Guide for Conservation Interventions in Bardia National Park, Nepal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7554, https://doi.org/10.5194/egusphere-egu26-7554, 2026.

Air pollution is one of the most serious challenges at the interface between the Earth system and societies, linking atmospheric processes, climate dynamics, human health, and social vulnerability. While advances in atmospheric and Earth system sciences have substantially improved the understanding of pollutant sources, transport, and threats, integration of societal dimensions into air pollution research remains uneven and conceptually fragmented. Here, we present a systematic literature review that examines how air pollution as interlinkage between Earth system and societies is conceptualised, operationalised, and addressed across interdisciplinary research. Following the PRISMA framework, we screened 1,297 peer-reviewed publications retrieved from the SCOPUS database using a structured search string spanning Earth system sciences, air pollution, and societal dimensions. A combination of a Large Language Model-assisted abstract screening, topic modelling, and full-text qualitative synthesis resulted in the final references of 104 interdisciplinary studies. We analyse temporal and geographic trends, emergent research themes, conceptual framings, and persistent barriers to integration. The literature is dominated by health impacts and air quality monitoring, while governance, equity, and justice perspectives remain marginal. We identify five main operationalisations of the air pollution as Earth system and societies interlinkage: (1) Emissions-to-exposure pathways, (2) Capacity to adapt to atmospheric load, (3) Monitoring and decision infrastructures, (4) Societal interventions as levers of change, and (5) Institutions, commons, and justice framings. Most studies treat societal systems as external drivers or endpoints, rather than as constitutive elements of coupled Earth and societies dynamics. Across the references, recurring barriers include data and monitoring gaps, methodological and scale mismatches between natural and social sciences, weak institutional coordination, and the limited integration of participatory and justice-oriented approaches. We argue that advancing air pollution research as Earth and societies interlinkages requires moving beyond additive interdisciplinarity toward integrative and interdisciplinary co-produced frameworks that embed e.g., social institutions, power relations, and equity and justice to identify key research needs. Strengthening this integration is critical for developing effective, legitimate and equitable air quality intervention measures towards sustainability within planetary boundaries.

How to cite: Alas, H. D., Govender, M., Glaser, M., Marcovecchio, G., Schaefer-Rolffs, U., Birkicht, M., Grossart, H.-P., Abel, D., Macke, A., and Schanze, J.: Air pollution as Earth and societies interlinkage: A systematic literature review on emerging themes, conceptualisations, and important gaps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9328, https://doi.org/10.5194/egusphere-egu26-9328, 2026.

This contribution examines the applicability of the Doughnut Economics framework as a systemic and ethically grounded analytical tool for navigating socio-ecological challenges of the Anthropocene. Focusing on a comparative analysis of Bosnia and Herzegovina, Croatia, Slovenia, and Austria, the paper develops a regional Doughnut model that captures both national performance and relational interdependencies across ecological ceilings and social foundations. By situating these four countries within a shared socio-ecological system, the analysis highlights asymmetries, spillover effects, and structural interconnections that are often obscured in single-country sustainability assessments. Methodologically, the study builds on the transformative model developed by the Institute for Political Ecology (IPE) in Zagreb and further advances it through an integrated indicator framework that combines Doughnut Economics, selected Sustainable Development Goals (SDGs), and a relational, colour-coded diagnostic logic. This approach enables a systemic reading of the Anthropocene as a condition marked not only by biophysical limits but also by socio-economic inequalities, governance failures, and uneven responsibility for ecological overshoot. Beyond diagnosis, the paper engages directly with key ethical and political questions raised by the Anthropocene concept: how to communicate systemic limits without foreclosing future imaginaries; how to use scientific frameworks to challenge public policy without technocratic determinism; and how to translate structural diagnosis into actionable yet hopeful transformation pathways. By comparing countries across different development trajectories and governance regimes, the study demonstrates that the Doughnut Economy can function as more than a sustainability narrative; it can operate as a replicable scientific methodology that supports reflexive governance, informs public debate, and fosters ethically grounded responses to Anthropocene conditions. The findings contribute to interdisciplinary discussions on how systemic concepts of the Anthropocene can be operationalised in ways that retain both analytical rigour and transformative potential.

How to cite: Safet, K.: Comparing Pathways through the Anthropocene and semi periphery perspective:A Doughnut Economics Assessment of Four European States , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9905, https://doi.org/10.5194/egusphere-egu26-9905, 2026.

The Anthropocene debates are rooted in epistemological differences. Geologists seek temporal metrics of spatially-even anthropogenic impact. Thus, they favor geologic data that fit this category. Humanists and social scientists, on the other hand, tend to focus on the negative effects of spatial unevenness. Without linking the Anthropocene’s temporal and spatial components, the intention for it to be useful for wider segments of society will be futile. By recognizing threshold moments in human history, the uneven spatial distributions of anthropogenic damage can be traced to specific events, thus actualizing the predictive value of geology.  We argue that the Anthropocene started in the 17^th century with a shift in worldview that resulted in removing the “spirit” from nature and thus it could be rendered, as Newton put it, “brute,” and it could consequently be viewed as a natural resource readily available for extractive economies.  By removing the spiritual value--or enchantment--from nature, the notion of protecting nature for its own good was lost to extracting profit for the benefit of the economic elites.

Acknowledging such a worldview shift makes more legible two fundamental dynamics between human and natural trajectories: the intensification of global inequity coterminous with the intensification of natural damage; and humanity’s ever more audacious attempts to control the environment. This ethos, wielded as the prime justification for taking over that which belonged to cultures not espousing it, has resulted in anthropogenic damage disproportionately affecting the most economically and historically vulnerable peoples. However, their alternative modes of coping with the damages—an ineluctable responsiveness to, rather than control over, environment—enables them to survive.  Often, the indigenous or traditional knowledge of these cultures sees nature as infused with spirit, i.e. enchanted.  As such, they could lead the way through the Anthropocene, modeling adaptation and mitigation strategies, and obviating the global North’s unsound hope for a technological solution.  By expanding the data beyond the stratigraphic, coordinated interdisciplinary research can measure variegated effects of––and responses to––the Anthropocene, thus better equipping humanity to adapt to and/or mitigate climate change and to eschew unsustainable practices.

How to cite: Nichols, K. and Gogineni, B.: Nature’s enchantment, lost but not forgotten: A way forward in the Anthropocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12481, https://doi.org/10.5194/egusphere-egu26-12481, 2026.

Integrating the human components into the Earth system framework can help fill the existing gap between the science of the natural world and society, thereby deepening our understanding of socio-environmental relationship. In the Anthropocene, these human-Earth interactions have intensified, particularly driven by the acceleration of resource-use since the Industrial Revolution. The growth of the technosphere, which refers to the global assemblage of non-food human-creations including machineries, infrastructure, and buildings, has played a central mechanistic role in this acceleration.

Here, we present an idealized model to couple the dynamics of the technosphere with other Earth spheres and to capture its interaction with human activities. The key driver of the numerical model is a dynamic time allocation of the human population to food provision, technosphere construction, or services, based on a competition of state-dependent motivations. The products of the activities computed from the labour and efficiency, together with Earth system feedbacks, thereby impact the motivations during the next time step. The mass of the technosphere contributes to the efficiency of human activities. We compare model outputs with historical data and find that the simulation reproduces trends in the global food supply, technosphere mass accumulation, and their feedback on the change of the sectoral labour distribution since 1900. The study establishes a novel integrated framework for advancing systemic human–Earth coupling, paving the way for country-level and grid-scale analyses in the future.

How to cite: Su, Y. and Galbraith, E.: An idealized model of the coupled human-technosphere-Earth system and hindcast from 1900, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13361, https://doi.org/10.5194/egusphere-egu26-13361, 2026.

The effects of decades of human action have led to the crossing of multiple planetary boundaries, yet humanity's structures remain built on extractivist logics that further constitute the loss of biocultural capital.

The anthropogenic changes in Earth’s geo-ecological systems are unprecedented for anything any historical society had to face. While early human ecologies were characterized by local feedbacks and gradual natural change, the globalized world assimilates and synchronizes crises far more rapidly than both human and non-human adaptation measures can keep up with. Synchronizing implies no geographical escapes as formerly regional problems tend to become connected by globalization and telecoupling. Following this asymmetry, the gap between the resilience of socio-ecological systems and the ongoing escalation widens.

In contrast to any other epoch, the Anthropocene is marked by the dominance of a single species and a specific way of living within the diversity of lifestyles. The capacity of local ecosystems, and even of the entirety of planet Earth, is eroded. In geological understanding, humanity leaves traces of the systemic failures of the present.

In the current discussion about the Anthropocene, two core readings of the new era prevail. One claims that now that humans are dominating global processes, they have the right, and the responsibility to take full control and manage the Earth system, with technical means and based on existing patterns. Visions of post-human economic systems, run by new forms of AI solving all problems, belong to this category. The other core narrative is not based on rights but on responsibility, in particular to respect the planetary boundaries of the Earth system to give it time to recover (albeit in a modified way – some changes are irreversible).

We hold that moving “beyond extractivism” is at the core of the second, responsibility-driven Post-Anthropocene horizon and a necessary prerequisite for: a humanistic, not a post-human future, with resilient societies providing the chance for a dignified life to its members. However, the disturbances of global systems the Anthropocene-humanity has set in motion will have lasting effects, which cannot be stopped or reversed (almost impossible in complex evolving systems) on human timescales. Hence, there are no (technical or other) ways out of the crisis humans created – we must find pathways towards a humane Post-Anthropocene under the given and emerging conditions. This will require more than mere adaptation to external (e.g. climate) changes; it calls for a co-evolutionary process of human societies with their (no longer really natural) environment. Resilient societies in a resource-constrained future will need to decouple human flourishing from planetary degradation – a future beyond the Anthropocene patterns of production and consumption, and a modification of the value systems driving the permanent escalation of human impacts. Such a vision offers evidence-based hope for future generations, who necessarily must be part of the solution.

Aiming to link the geological dimension of the Anthropocene to future outlooks based on current and historical human nature, this concept can support the mobilization of communities by giving back agency, informed by state-of-the-art research.

How to cite: Best, M. and Spangenberg, J. H.: Beyond Extractivism: Humanity Entering the Post-Anthropocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15538, https://doi.org/10.5194/egusphere-egu26-15538, 2026.

Nature-based Solutions (NbS) are increasingly highlighted in climate adaptation policy, yet spatial planning still lacks operational tools to identify where NbS are most feasible and desirable. This contribution develops an NbS potential mapping framework that combines an ESG perspective with ecosystem-service modelling, and illustrates its first implementation in Taiwan using InVEST carbon storage as a prototype for the Environmental/Ecosystem (E) dimension.

We reinterpret ESG as Ecosystem (services)–Social–Governance and organise the framework into three stages: Identification, Assessment, and Retrospective Validation. In the Identification stage, national land-use data are reclassified into nine categories (forests and conservation areas, agricultural land, residential areas, industrial and commercial zones, infrastructure and utilities, coastal and marine areas, water bodies and river systems, urban green and recreational spaces, and mixed/special use zones). Each category is assigned initial qualitative E, S and G attributes based on environmental sensitivity, social exposure, and governance conditions relevant to climate risk and adaptation.

To move from qualitative “environment” toward quantified natural capital, we implement the E dimension using the InVEST Carbon Storage model. Carbon stocks are estimated for different land-use types and normalised to produce an E indicator that is applied as an additional constraint on the initial E category: within each land-use class, areas with higher carbon storage are flagged as high natural capital. We test this ESG–ecosystem services framework in two contrasting Taiwanese landscapes—a coastal wetland–aquaculture system and a mountain catchment affected by landslide-related hazards—to generate NbS potential maps that highlight combinations of high natural capital, high climate risk, and feasible governance conditions.

For retrospective validation, we compare our ESG land-use definitions and the spatial pattern of NbS potential with published ESG-based environmental scoring and NbS selection studies in similar land-use contexts, to check whether our classification logic and prioritisation are consistent with independent frameworks. Rather than delivering a full national ecosystem-service assessment, this work focuses on the structure of the ESG–ecosystem services framework and a first, carbon-based NbS potential map, designed to be progressively enriched with additional quantified ecosystem services. In future work we plan to refine the framework through structured expert feedback (e.g. a Delphi process), and invite interested researchers to contribute to this co-development.

How to cite: Wu, Y.-H., Wu, J.-Y., Chen, Z.-S., and Chung, M.-K.: Developing an NbS potential map with an ESG–ecosystem services framework: integrating InVEST carbon storage in Taiwan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15664, https://doi.org/10.5194/egusphere-egu26-15664, 2026.

We live in the Anthropocene (Crutzen & Stoermer, 2000) or, in Stengers’ (2015) terms, in the time of catastrophes, a period marked by the intensification of interdependencies between socio-environmental crises. Scientific literature on the Anthropocene has produced increasingly consistent diagnoses of ongoing biogeophysical transformations, grounded primarily in contributions from the Earth System Sciences (Steffen et al., 2018) and the Geological Sciences (Zalasiewicz et al., 2021), which are extensively systematised in the works of Wallenhorst (2020; 2025). These studies provide a robust framework for understanding planetary boundaries, dynamics of acceleration, and systemic risks associated with transformations driven by the capitalist mode of production. In parallel, the concept of the Anthropocene has been further developed by scholars working at the interface between Earth sciences and the humanities, incorporating economic, historical and political dimensions into the understanding of the contemporary crisis. In this regard, contributions by Veiga (2019; 2023; 2025) and Latour (2017; 2021) shift the debate beyond a strictly biogeophysical perspective, interrogating models of development, forms of social organisation and regimes of knowledge production that sustain socio-environmental collapse, while offering occasional reflections on the role of education. It is within this context that a central question emerges, guiding this proposal: in the face of the gravity of the Anthropocene, is what we lack a deeper knowledge of the urgency of the times in which we live, or do existing bodies of knowledge rather collide with political, economic and institutional interests that hinder their translation into social transformation? The aim of this article is to address this question from the perspective of Environmental Education (EE), exploring its analytical contributions to understanding the relationships between science, power and socio-environmental inequalities. EE is here understood as a field in permanent (re)foundation in response to socio-environmental transformations. As noted by Reigota (2004), EE emerged as a response to environmental issues produced by a predatory and unsustainable capitalist economic model, gaining international visibility from the Stockholm Conference (1972) onwards. However, as indicated by Leite Lopes (2004) and Carvalho (2001), some early approaches adopted a conservationist and normative character, centred on individual responsibility and avoiding a critical interrogation of the social structures that produce environmental degradation. Over recent decades, authors such as Layrargues (2012) and Carvalho (2014) have deepened the critical foundations of EE, highlighting it as a field traversed by epistemological, ethical and political disputes. Methodologically, this proposal is based on a bibliographic review of scientific productions from the Earth sciences, the humanities and Environmental Education, with an emphasis on articulations between the Anthropocene, scientific knowledge, politics and socio-environmental justice. In dialogue with Carvalho and Ortega (2024), we argue that the dimension of catastrophes should not be understood solely as collapse, but also as an opportunity to reinvent ways of doing science, educating and inhabiting the world, reaffirming the centrality of Environmental Education in the construction of socially just responses to the Anthropocene.

How to cite: Pinheiro, S., Lopes, R., and Bordes, M.: Environmental Education and the Anthropocene: Convergences, Distances, and Contemporary Challenges, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18296, https://doi.org/10.5194/egusphere-egu26-18296, 2026.

Current observations of the climate, ocean, biodiversity, soils, and freshwater indicate that the Earth system is undergoing rapid change that exceeds natural variability. The environmental sciences regard this development as a defining characteristic of the Anthropocene. The Earth system change, in turn, results in increasing societal impacts and risks due to resource depletion and deterioration, as well as global warming with more severe and frequent extreme events. While research in the earth, environmental, and social sciences has expanded in response, the complexity and scale of the phenomena require deeper integration combined with a focus on sustainability transformations.

This research identifies critical gaps in current Anthropocene research and proposes an approach for Integrative and Transformative Research on Earth and Societies. It emphasises three core areas: (i) multi-system approaches for Earth and societies to deal with the heterogeneity and dynamics of main interlinkages; (ii) system-based scientific rationales for societal agreement on planetary boundaries and societal goals for basic needs; and (iii) systemic innovations fostering transformations to reduce societal pressures on the environment and build resilience to Earth system impacts and risks according to planetary boundaries and societal goals, taking into account levers, perceptions and capacities.

The interface between the freshwater compartment of the Earth system and societies is used to explain the novel approach. This encompasses main water-related interlinkages, planetary boundaries relevant for freshwater change and societal goals for basic water needs; and innovations for reducing societal pressures on freshwater and strengthening resilience to water extremes.

How to cite: Shehayeb, R., Schanze, J., Gerten, D., Prys-Hansen, M., Tetzlaff, D., Abel, D., Dubbert, M., Düthmann, D., Fröhlich, C., Glaser, M., Gronenborn, D., Jöris, O., Moosdorf, N., and Grossart, H.-P.: Integrative and Transformative Research on Earth and Societies and its specificity for Freshwater , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20091, https://doi.org/10.5194/egusphere-egu26-20091, 2026.

The Baltic Sea has a long history of anthropogenic disturbance, that started earlier than in most other coastal oceans and marginal seas. Especially in regions where shallow depths and limited space constrain the area that is available for anthropogenic use, conflicts of interest arise from the rising demand of multiple socio-economic players such as offshore wind, nature conservation, shipping, coastal protection, fishing, military, tourism and many more. The intensive use over many centuries has left long-lasting and partly irreversible traces on the seafloor and the benthic ecosystem. We aim to make the traces of different seafloor modulating processes such as bottom trawling, ship anchoring, propeller wake erosion, seabed constructions or material dumping visible using marine geophysical data of different resolution and spatial coverage. From this data, we can derive the spatial distribution and intensity of anthropogenic disturbances in the Baltic Sea and subsequently evaluate the pressures that they exert in certain areas. This approach is exemplified for propeller wakes that are generated by commercial ships, and that are not yet included in cumulative impact assessments. The results outline how single processes can exert pressures on the entire vertical sea, from the ocean-atmosphere boundary down to the seafloor and below, with likely impacts on ecosystem functioning and marine biodiversity. For propeller wakes, the broad spectrum of direct consequences suggests that the challenges associated with this anthropogenic stressor can only be met and moderated through intensive interdisciplinary research.

How to cite: Geersen, J., von Thenen, M., Feldens, P., Kaiser, J., and Stuckas, H.: The Baltic Seafloor in the Anthropocene: from societal pressures to sustainability transformations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20277, https://doi.org/10.5194/egusphere-egu26-20277, 2026.

This is a review paper discerning: 1. Three broad and deep transitions (the energy transition, current use of space, and the total greenhouse emissions of the food system), and 2. A call for transformation that is supported by a multi- to inter- to transdisciplinary theory of the Anthropocene. Is the theoretical transformation (2) needed to support the practical transformations (1)? How can disciplines become overarching, supporting to each other and contribute to potential solutions? Anthropocene examples and discussions from social science, humanities and science domains are presented: Is the Anthropocene driven by force majeure? Can humans develop from weak and strong forces towards an emphatic society? The composite model of the Anthropocene is presented with the anthromes/Nature Relationship Index [1), the commons transition [2] and the convivial society [3] as an integrated concept/theory. Through self-domestication and non-violent cooperation the paper stimulates a thoughtful call on theoretical and practical transformations to local to global communities.

1.  Ellis EC, Malhi Y, Ritchie H et al (2025) An aspirational approach to planetary futures. Nature 642, 889–899. Available at: https://doi.org/10.1038/s41586-025-09080-

2.  Bauwens M, Kostakis V and Pazaitis A (2019) A Commons Transition Strategy. In: Peer to Peer: The Commons Manifesto Vol. 10: pp. 55–70. Available at:  http://www.jstor.org/stable/j.ctvfc53qf.11

3.  Second Convivialist Manifesto (2020) Towards a Post-Neoliberal World. Convivialist International. Civic Sociology (2020) 1 (1): 12721. https://doi.org/10.1525/001c.12721

How to cite: van der Linde, L., Lont, J., and Kluiving, S.: Towards a Multi- to Inter- to Transdisciplinary Theory of the Anthropocene - Review of overarching disciplines and research on overstepped planetary boundaries and social and humanitarian crises, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22330, https://doi.org/10.5194/egusphere-egu26-22330, 2026.

The sedimentation patterns within endorheic basins are primarily controlled by climate. These basins are sensitive to atmospheric circulation patterns that influence the distribution of moist and dry air masses. During the Middle to Late Permian period, Western Gondwana underwent continentalization, during which fluvial, lacustrine, and aeolian deposits formed the stratigraphic framework of several basins. Field data from the Rio do Rasto Formation of the Paraná Basin in southern Brazil reveal a highly complex depositional architecture within this broad endorheic basin. By analyzing vertical facies succession and paleocurrent patterns, we identified two distinct catchments that feed distributive fluvial systems (DFS) anchored in different source areas within a large paleogeographic depositional area. The Rio do Rasto Formation's stratigraphic framework reveals the intercalation of medial-to-distal DFS deposits that form tens of meters of progradational cycles. These cycles consist of basal deltaic lobes and lacustrine deposits. Ephemeral fluvial channels, aeolian deposits, and red beds are recognized toward the top. Additionally, linking paleocurrent data with facies associations suggests that the two distinct catchments were influenced by different atmospheric circulation mechanisms. The more perennial basal deposits were supplied with sediment and water from southern and southeastern African terrains. In contrast, ephemeral streams and arid-related deposits were fed by west-northwestern catchments associated with the Asunción Arch. When analyzing the vertical patterns of facies in progradational cycles, ephemeral deposits tend to dominate perennial ones toward the top. This indicates an increasing trend of aridization in the Late Permian. Comparative sedimentological and paleontological data from the Karoo Basin reveal similar depositional patterns, with basal deposits influenced by a moisture-rich center. Paleoclimatic models from the Middle to Late Permian suggest that the moisture center migrated southward. This migration caused an intensification of arid conditions and a decrease in precipitation in southern Africa. Consequently, this climatic shift likely diminished the supply of water and sediment to fluvial and deltaic systems in the northern Paraná Basin, reinforcing an aridification trend across western Gondwana on a regional scale. High discharge variability in western and northwestern catchments may have been exacerbated by orographic barriers producing rain shadows. The Asunción Arch and the volcanic belt along the western margin of South America, associated with the Sierras Pampeanas, further restricted moisture-bearing air masses from reaching the continental interior. Observed stratigraphic patterns reflect endorheic basins' sensitivity to shifts in atmospheric circulation and hydrological regimes. The increasing aridity recorded in the upper portions of the Rio do Rasto Formation aligns with global climatic trends recognized in other Permian basins. Such widespread aridization may have contributed to the paleoenvironmental instability preceding the End-Permian mass extinction. This highlights the broader significance of basin-scale sedimentary records in reconstructing climatic and ecological change.

How to cite: Manna, M., Bállico, M., Scherer, C., Scotese, C., Feitosa, A., and Franqueira, A. V.: Paleoclimate-driven depositional dynamics of Western Gondwana Endorheic Basins during the Middle to Late Permian., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-632, https://doi.org/10.5194/egusphere-egu26-632, 2026.

The storage of carbon dioxide (CO₂) in depleted hydrocarbon reservoirs and saline aquifers is regarded as a key strategy to mitigate the accumulation of greenhouse gases in the atmosphere. Evaluating a geological formation for CO₂ storage requires assessing its capacity, injectivity, and trapping mechanisms, all of which depend on its geological and petrophysical properties. Outcrops of sedimentary rocks that serve as reservoir analogues have increasingly been used to support the determination of spatial and temporal distribution parameters and reservoir heterogeneities. These outcrops provide essential geological information for understanding subsurface rock characteristics, including geometry, textural and compositional variations, and diagenetic features. Among the different reservoir types, saline aquifers are considered the most promising for geological carbon storage due to their high capacity and broad regional distribution. In this context, within the Paraná Basin, the Rio Bonito Formation stands out as a potential target for CO₂ storage because of its favorable lithological characteristics. The sandstones of this formation, deposited in a transgressive setting, encompass a wide range of depositional systems, from tide-influenced environments to wave-dominated platforms. High-resolution sedimentological, stratigraphic, and structural information obtained from outcrops plays a crucial role in refining the understanding of subsurface reservoir rocks. Detailed stratigraphic surveys are greatly enhanced by 3D outcrop modelling, which has advanced through the use of digital photogrammetry and laser-scanning techniques. When applied with unmanned aerial vehicles (UAVs), these methods enable the acquisition, processing, and integration of large datasets with high spatial accuracy. This study aimed to characterize the depositional architecture and identify macro- and mesoscale heterogeneities using a 3D digital outcrop model. Five photofacies were distinguished based on the visual tracing of photohorizons, erosional surface patterns, and image-based color and texture criteria. These photofacies supported the identification of stacking patterns and the definition of key architectural elements. The high-resolution stratigraphic elements exhibit geometries ranging from lenticular to tabular, with moderate to high lateral continuity. Laterally extensive deposits are associated with wave-dominated shoreface and barrier-lagoon systems, whereas lenticular bodies with moderate lateral traceability correspond to tidal channels and bar deposits.
Overall, the integration of detailed outcrop analysis with high-resolution 3D modelling provides a robust framework for characterizing the depositional architecture and heterogeneity of potential CO₂ storage reservoirs. The identified photofacies and their associated geometries offer valuable insights into the spatial continuity and connectivity of sedimentary bodies within the Rio Bonito Formation, reinforcing its suitability as a saline-aquifer reservoir analogue. By improving the understanding of reservoir-scale variability, this approach enhances predictions of capacity, injectivity, and trapping efficiency, thereby contributing to more reliable assessments of the formation’s potential for geological carbon storage.

How to cite: Barreto, L., Bállico, M., Souza, E., Manna, M., Scherer, C., Santos, A., Paz, C., Fontoura, G., and Feitosa, A.: Using 3D Digital Modeling to Identify Reservoir Heterogeneities: A Case Study from the Rio Bonito Formation, Paraná Basin, Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1273, https://doi.org/10.5194/egusphere-egu26-1273, 2026.

The Junggar Basin is a typical intracontinental petroliferous basin in Central Asia, and the Moxizhuang area, located in the hinterland of the basin, is a key target for Jurassic hydrocarbon exploration. The Sangonghe Formation serves as the major petroliferous reservoir interval in this region, yet the coupling relationship between sedimentary architecture  and reservoir microscopic characteristics  remains unclear, which restricts the accurate evaluation of reservoir quality and efficient hydrocarbon exploration. This study aims to investigate the spatial assemblage relationship of sedimentary microfacies and reveal the controlling mechanism of sedimentary architecture on reservoir microscopic characteristics.

Based on the core samples, rock thin sections, and logging data of 12 wells in the Moxizhuang area, a multi-index comprehensive research method was adopted.The research methods include: (1) Sedimentary framework analysis: Through core logging and well log correlation, the types of sedimentary microfacies associations were identified, and the sand body distribution characteristics and geometric morphology were delineated.(2) Reservoir microscopic characterization: Cast thin section observation, scanning electron microscopy  analysis, and mercury intrusion capillary pressure  experiments were carried out to quantitatively characterize the pore types, pore-throat distribution, and reservoir physical parameters.(3) Diagenesis analysis: By means of rock thin section identification and scanning electron microscopy-cathodoluminescence  observation, the diagenetic processes and their impacts on reservoir quality were clarified.

The Sangonghe Formation in the study area is dominated by the estuary bar microfacies and subaqueous distributary channel microfacies of the delta front. A total of four sedimentary microfacies association patterns have been identified in the study area, namely ，superimposed subaqueous distributary channels, truncated subaqueous distributary channels, channel overlying reworked estuary bar, and superimposed estuary bars. These patterns reflect distinct sedimentary environments and hydrodynamic conditions.There are significant differences in reservoir characteristics under different sedimentary microfacies association patterns. Specifically, the sand bodies in the superimposed subaqueous distributary channel pattern exhibit superior overall porosity, permeability, and pore connectivity compared with those in the other patterns.(The conclusion supported by quantitative analytical data.) The sedimentary framework is the dominant factor controlling the microscopic reservoir characteristics of the Sangonghe Formation in the Moxizhuang area.The sedimentary framework controls reservoir quality by regulating diagenetic processes: the superimposed subaqueous distributary channel sand bodies formed in high-energy environments are well-sorted, characterized by intense feldspar dissolution and the development of abundant secondary pores; the superimposed estuary bar sand bodies formed in low-energy environments undergo significant carbonate cementation, resulting in substantial pore loss;In the truncated subaqueous distributary channel pattern, multiple phases of channels are vertically superimposed in an erosional manner, leading to the widespread development of erosion surfaces. The poorly sorted glutenites are mostly cemented by calcite crystals in a mosaic form, resulting in generally poor physical properties.

By identifying the types of sedimentary microfacies associations and comparing the differences in reservoir characteristics among various types, this study establishes the coupling relationship between the sedimentary framework and reservoir quality. The findings hold important significance for the fine evaluation and exploration of hydrocarbon reservoirs in the hinterland of the Junggar Basin and analogous intracontinental basins.

Presentation preference: Poster presentation is also acceptable if PICO slots are full.Thank you.

How to cite: Guo, T. and Zhang, L.: Controlling effect of sedimentary architecture on microscopic reservoir characteristics: Sangonghe Formation, Moxizhuang Area, Junggar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2277, https://doi.org/10.5194/egusphere-egu26-2277, 2026.

This study focused on the evaluation and comparison of three image-based techniques for pore-space segmentation in Cambrian sandstones from the Baltic Basin: ImageJ thresholding, QuPath thresholding, and a U-Net convolutional neural network. Core samples from a borehole in Western Lithuania were obtained from the Lithuanian Geological Survey storage facility. Conventional epoxy-impregnated thin sections were scanned using a petrographic microscope equipped with a digital camera to acquire high-resolution images.

In QuPath, images were pre-processed and segmented using fixed-threshold pixel classification, followed by visual inspection and manual adjustment to produce validated masks used for U-Net training. ImageJ analysis involved a median filter, conversion to grayscale, automatic thresholding, and binary mask generation. Porosity estimates derived from each method were compared with laboratory-measured core-plug porosity.

The mean absolute error (MAE) relative to laboratory porosity was 3.88% for QuPath, 3.91% for U-Net, and 4.25% for ImageJ. Threshold-based methods performed well in samples with uniform pore–mineral contrast but tended to underestimate pore space where contrast was heterogeneous or pore geometries were complex. The U-Net model more consistently detected smaller and disconnected pores, however, its overall MAE was similar to that of QuPath, reflecting its reliance on threshold-derived training masks.

The results demonstrate that manually validated threshold-based segmentations can serve as effective training data for deep-learning models, enabling reproducible pore-scale characterization of Cambrian sandstones where fully annotated datasets are limited.

How to cite: Talibov, N., Kaminskas, D., and Cichon - Pupienis, A.: Image-based porosity estimation in Cambrian sandstones from the Vilkyčiai-22 well, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3317, https://doi.org/10.5194/egusphere-egu26-3317, 2026.

The island of Grande-Terre in New Caledonia (NC) hosts one of the world’s largest lagoon complexes, and its sediment infilling makes it an ideal case study to understand the evolution of mixed siliciclastic-carbonate platforms. The eastern margin of Grande-Terre, relatively unknown until now, presents the opportunity to examine the major changes in lagoon sedimentation since the end of the Mio-Pliocene in response to climate variation, vertical movements and anthropogenic activities. Using geomorphological and seismic interpretations constrained with dated sediment cores, this study identifies three seismic sequences separated by major channelized and erosional unconformities. The upper and last unconformity is supposed to be linked to the sea-level lowstand during the Last Glacial Maximum. The overlying sedimentary record, dated to the Holocene, contains both clastic and carbonate deposits, resulting from the reflooding of the shelf. This mixed sediment infill displays significant spatial variation. The inner lagoon concentrates terrigenous inputs whereas the median lagoon is dominated by a series of large carbonate reef flats. The outer-shelf retains a remarkable succession of falling stages deposits that reflect 100 kyr depositional sequence cycles resting atop the Mio-Pliocene carbonate platform. Stratigraphic analysis of these Pleistocene sequences dates their deposition from 630 kyr (MIS 16) and allows us to estimate a subsidence rate of approximately 0.06 m/kyr on the outer shelf, enabling the barrier reef to keep up and the successive lowstand sediment wedges to stack.

How to cite: Kerouédan, L., Le Roy, P., Jouet, G., Leroux, E., and Jorry, S.: Late Neogene seismic stratigraphy of the eastern mixed siliciclastic-carbonate platform of New Caledonia (SW Pacific), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4038, https://doi.org/10.5194/egusphere-egu26-4038, 2026.

Submarine turbidites and mass-transport deposits (MTDs) provide potential valuable archives for reconstructing earthquake histories beyond the limits of instrumental and historical records. This study examines turbidite sequences in the Gulf of Aqaba–Eilat (GAE), the southern segment of the Dead Sea Transform (DST), to evaluate their potential as paleo-earthquake indicators. Although the region has experienced major historical earthquakes, including the Mw 7.3 1995 Nuweiba event, offshore paleoseismic records south of the gulf head remain fragmentary. Previous work has demonstrated that turbidite layers in the northern GAE can be correlated with historical and pre-historical earthquakes, supporting the feasibility of turbidite-based paleo-seismic reconstruction in this setting.

Five gravity cores collected during RV Meteor cruise M44/3 from water depths of 135-838 m were studied using a multi-proxy approach integrating sedimentology, X-ray fluorescence (XRF) core scanning, and radiocarbon dating. Grain-size distributions and sedimentary structures are used to characterize turbidites and distinguish earthquake-triggered deposits from non-seismic gravity flows—such as flash-flood-induced hyperpycnal events.

Mass-transport events are expressed in the cores as coarse-grained units with sharp stratigraphic boundaries and distinct geochemical anomalies relative to background pelagic sediment and are more frequent in the deeper basin (> 500 m). Several units may exhibit stratigraphic synchronicity across multiple cores, supporting a seismic trigger, which will be verified by dating.

XRF-derived elemental ratios (Zr/Rb, Sr/Ti, Sr/Ca, Fe/Ca) provide additional constraints on sediment source and mass-transport processes. The coarse-grained event layers reveal systematic geochemical variability among units with high Zr/Rb and comparatively elevated Fe/Ca values characterizing terrigenous-dominated turbidites, while relatively enhanced Sr/Ca and Sr/Ti ratios typify biogenic carbonate-rich event layers probably representing reef debris originating from the shelf edge. While bathymetric and chronological analyses are still ongoing, this may indicate different processes and triggering mechanisms. Radiocarbon dating of planktonic (pelagic background sediment) and benthic (event layers) foraminifera combined with Bayesian age-depth modeling will support the triggers and transport mechanisms interpretation.

Overall, this study aims to refine earthquake recurrence estimates along the southern DST, improve criteria for identifying seismo-turbidites in hyper-arid marine settings, and contribute to regional seismic and tsunami hazard assessments.

How to cite: Bichachi, G., Bookman, R., Trubin, Y., and Hebbeln, D.: Seismic Activity and Turbidite Deposition in the Gulf of Aqaba-Eilat: Insights from Sediment Core Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5412, https://doi.org/10.5194/egusphere-egu26-5412, 2026.

Abstract: Shallow-water deltas represent a focal point in sedimentology research. However, studies on shallow-water deltas developed under arid climatic conditions, characterized by intermittently oscillating water bodies and complex sedimentary features and processes, are relatively scarce. Based on an integrated analysis of core, well logging, laboratory analytical, and seismic data, and guided by insights from modern sedimentary analogues and sedimentary numerical simulations, this study conducts a systematic investigation of the sedimentary facies within the Jurassic Qigu Formation (J₃q) in the Yongjin area of the central Junggar Basin. A sedimentary model for the Qigu Formation is subsequently established. The key findings are as follows: ① Depositional Evolution. During the Middle-Late Jurassic, the climate in the Junggar Basin shifted to arid, leading to shallow and frequently oscillating lacustrine water bodies during the deposition of the J3q. Sand groups 1 to 3 are dominated by shallow-water braided river delta deposits. By sand group 4, with diminished sediment supply and persistent aridity, the sedimentary system transitioned to a meandering river delta. ② Characteristics of Arid Shallow-Water Deltas. Compared to their humid-climate counterparts, the arid shallow-water deltas in this study area exhibit rapidly shifting, frequently bifurcating subaqueous distributary channels, resulting in various channel sandbody morphologies. The sedimentary record shows interbedded red and gray layers, with sandstones being finer-grained, texturally immature, and limited in distribution scale. Sustained aridity led to continuously decreasing accommodation space, resulting in the near-absence of mouth bars within delta lobes. The primary sedimentary bodies are various types of subaqueous distributary channel sands. ③ Reservoir Heterogeneity and Exploration Implications. Controlled by single-point sources, the sedimentary bodies are limited in scale and show significant downstream differentiation. Three sedimentary microfacies are identified: high-energy main subaqueous channels, medium- to high-energy anastomosing distributary channels, and low-energy reworked distributary channels. The poor connectivity between individual sandbodies and strong reservoir heterogeneity pose significant challenges for hydrocarbon exploration and development in such settings.This research not only deepens the understanding of sedimentary processes in arid-climate shallow-water deltas but also provides a crucial sedimentological model and basis for refined reservoir prediction in analogous geological settings.

Keywords:  arid climate,  sedimentary model, shallow-water delta,  Jurassic,  Junggar Basin

How to cite: Kong, Q. and Wang, Y.: Sedimentary Processes and Model Reconstruction of Shallow-Water Deltas under Arid Climate: A Case Study from the J3q in the Hinterland of the Junggar Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7036, https://doi.org/10.5194/egusphere-egu26-7036, 2026.

The Dinarides Lake System (DLS) constituted a set of intramontane freshwater lakes, which expanded during the Early to Middle Miocene in southeastern Europe. Sedimentation between ca. 18-12.5 Ma was contemporaneous with two well-documented climatic phases in marine records: the warm and humid Miocene Climatic Optimum (MCO; ca. 16.9-14.7 Ma) and the subsequent Middle Miocene Climatic Transition (MMCT; ca. 14.7-13.8 Ma). The MMCT was characterized by global cooling and the establishment of permanent Antarctic ice sheets. Here, we aim to reconstruct continental paleoenvironmental and paleoclimate dynamics during the MCO and MMCT in southeastern Europe based on sedimentary records from the DLS.

We focus on four former lake basins (Pag, Gacko, Livno-Tomislavgrad, and Bugojno) and build on existing stratigraphic, sedimentological, and geochronological studies, including magnetostratigraphy, biostratigraphy, and the absolute dating of ash layers. We establish stable carbon and oxygen isotope records for the four basins and combine them with petrographic and mineralogical analysis derived from Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD).

Our first quantified XRD results show the presence of high-Mg calcite and aragonite in some samples from each section, which indicates little to no diagenesis affecting our samples. δ¹⁸O and δ¹³C values for each lake basin are positively correlated. We interpret the positive correlation to reflect hydrologically closed lake conditions during carbonate precipitation. Additionally, δ¹⁸O values display a positive relationship with modern elevations and distance to the coast for two time-equivalent lake records (Pag and Livno-Tomislavgrad) during the onset of the MCO. While the near-coastal Pag section yields mean δ¹⁸Ovalues of -9.1 ± 0.1 ‰ (n= 89; V-PDB), the Livno-Tomislavgrad basin (located ca. 50 km off the coast at ca. 750 m elevation) yields δ¹⁸O values of -5.0 ± 0.2 ‰ (n= 22; V-PDB). This may indicate that δ¹⁸O values are primarily controlled by evaporation in the lake basin located further away from the coast, rather than the isotopic composition of the incoming waters. By combining existing studies with our new data, we aim to reconstruct the terrestrial paleoenvironment and paleoclimate during lake deposition during the MCO and MMCT in southeastern Europe.

How to cite: Moreau, M., Löberbauer, M., Sanchez-Ortiz, G., Mandic, O., Andrić Tomašević, N., K.C. Rugenstein, J., Baldermann, A., Dietzel, M., Pavelić, D., Demir, V., Vuković, B., Auer, G., Kurz, W., and J.M. Meijers, M.: Early to Middle Miocene terrestrial paleoenvironmental reconstructions of the Dinarides Lake System (Croatia, Bosnia and Herzegovina), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7590, https://doi.org/10.5194/egusphere-egu26-7590, 2026.

Fluvial crevasse splay deposits and their traditional facies models are often modified significantly due to marine influence, viz., incoming flood tidal currents and/or wave encroachments, particularly in downstream-controlled river setting near to delta-estuary mouth areas. An integrated sedimentological-ichnofabric analysis, often typically representing such episodic marine encroachments, may properly represent the depositional models. In the present study, a ~7-8 m-thick siliciclastic interval comprising amalgamated bioturbated sandstones-heteroliths-shale is studied in terms of sedimentological-ichnofabric properties to assess a possible crevasse splay deposit. The succession is a part of the Permian Barren Measures Formation, West Bokaro Basin, India, which is broadly interpreted as a fluvio-marine estuary-delta depositional system. Seven fining-upward cycles represent tide-dominated crevasse-channel, characterized by lenticular and horizontally laminated sandstone, followed by crevasse-fan lobes, ranging from proximal organic-rich, wave-modified bioturbated sandy-heteroliths to medial-distal muddy-heteroliths. Eight diminutive, low-diversity brackish-water ichnogenera are recorded, grouped into six ichnofabrics: Planolites (IF1), Macaronichnus (IF2), Rosselia (IF3), Palaeophycus (IF4), Cylindrichnus-Planolites (IF5), and Teichichnus (IF6) ichnofabrics; reflecting sensitive ecological responses to shifting sub-environmental controls within individual cycles. Salinity fluctuations governed colonization, with euryhaline taxa dominating tidally influenced channels and stenohaline fauna typifying wave-modified lobes. Up-section increase in ichnodiversity and wave influence suggest more frequent marine-influenced flood surges, followed by post-flood quiescent sedimentation, and episodic colonization windows in the low-lying overbank areas. Variations in sedimentation rate across flood and interflood periods regulated colonization strategies, tiering patterns, and the transition from softground to firmground ichnofabric. Collectively, these results demonstrate that interactions between fluvio-marine processes and associated benthic colonization uniquely characterize a crevasse-splay architecture near the tide-wave influenced estuarine mouth system.

How to cite: Bhattacharya, A., Bhattacharya, B., Banerjee, M., and Pathak, A.: Sedimentological–ichnofabric architecture of a crevasse splay deposit near an estuary mouth: A study from Permian Barren Measures Formation, West Bokaro Basin, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10879, https://doi.org/10.5194/egusphere-egu26-10879, 2026.

Deciphering the subsurface architecture of Quaternary successions in glacially influenced environments represents a significant challenge, particularly in transitional settings where pronounced lateral variability and the common amalgamation of coarse-grained sedimentary bodies with similar facies characteristics may obscure stratigraphic boundaries. Within the framework of the CARG geological mapping project (Sheet 124 - “Verona Est”), we propose an updated stratigraphic framework for the upper 100 m of the eastern Verona plain (northern Po Basin), developed through the application of Unconformity-Bounded Stratigraphic Units (UBSUs). Our investigation builds upon a robust legacy dataset comprising 667 stratigraphic and geotechnical records, including continuous cores, water wells and cone penetration tests. This extensive database has been recently upgraded and integrated with seven newly acquired sediment cores, ranging from 30 to 85 m in length, specifically targeted to test preliminary stratigraphic models. We employed event-stratigraphy principles to discriminate between aggrading glacial outwash systems and incising fluvial systems associated with glacial-interglacial cycles. Within this framework, laterally continuous peat horizons, traceable across the entire study area, act as key regional stratigraphic markers and record the development of major stratigraphic unconformities. Furthermore, we tested a combined approach integrating classic stratigraphy method with geophysical exploration, involving the acquisition of a dense dataset of single-station ambient noise measurements. We aimed to build a geophysical cross-section based on the Horizontal-to-Vertical Spectral Ratio (HVSR) technique to highlight resonance frequency variations induced by near-surface stratigraphic heterogeneities. Finally, through the inversion of HVSR curves, constrained by Shear Wave Velocity (Vs) measurements and direct stratigraphic observation, we aim to determine the depth of major impedance contrasts to infer the architecture of the basin fill.

How to cite: Lucci, G., Di Martino, A., Viola, G., and Amorosi, A.: Late Quaternary unconformity-bounded stratigraphy of the northern Po Plain (Verona area) from subsurface data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11293, https://doi.org/10.5194/egusphere-egu26-11293, 2026.

Mixed siliciclastic-carbonate sedimentation is a special phenomenon formed by the intermixture of carbonate and siliciclastic, which holds great significance for unconventional hydrocarbon exploration but also possesses considerable value in the study of sedimentary dynamics, and reconstruction of paleoenvironment-paleoclimate. The Bolila Formation drilled in well QZ-8, eastern part of the Qiangtang Basin, developed mixed siliciclastic-carbonate rocks and successions. However, their sedimentary characteristics and genetic mechanisms remain unclear. Based on well-logging data, core and microscopic observations, and zircon U‑Pb dating of mixed siliciclastic-carbonate rocks from the Bolila Formation in well QZ‑8, this study constrains the types, characteristics, and provenance of mixed siliciclastic-carbonate rocks. On this basis, an astronomical timescale for the Bolila Formation in well QZ‑8 was established, clarifying the controlling effects of tectonic evolution and astronomical orbital parameters on mixed siliciclastic-carbonate rocks. The Bolila Formation in well QZ-8 contains clastic rocks, carbonate rocks and mixed siliciclastic-carbonate rocks, with 18 lithofacies identified, including mudstone(F1), silty mudstone(F2), greywacke(F3), micrite/crystalline limestone(F4), intraclastic/ooid-peloid wackestone(F5&F6), floatstone(F7), calcareous/bioclastic mudstone(F8&F9), calcareous siltstone/sandstone(F10&F11), marlstone (F12), silty/mixed siliciclastic micrite(F13&F14), mixed siliciclastic ooid-peloid packstone(F15), mixed siliciclastic bioclastic wackestone(F16), mixed siliciclastic peloid wackestone/packstone(F17), and mixed siliciclastic sparry bioclastic-ooid grainstone(F18). It was deposited in a distally steepened carbonate ramp, which can be subdivided into inner ramp, middle ramp, distal slope, and outer ramp. The terrigenous clastic grains in the mixed siliciclastic-carbonate rocks are dominated by feldspar and lithic fragments, with poor sorting and roundness. Cathodoluminescence analysis of the quartz indicates magmatic origin. The detrital zircons are predominantly euhedral with distinct oscillatory zoning and high Th/U values, indicating the magmatic origin. The age spectrum shows a unimodal distribution, which correlates well with the reported U-Pb age spectrum of magmatic arcs in adjacent Tanggula Pass, Yanshiping, Geladandong, Zaduo and Shuanghu areas, indicating the provenance is mainly derived from the proximal magmatic arcs. Furthermore, the zircon U-Pb weighted mean age obtained from the tuffaceous mudstone sample at 286 m is 237.78±0.98 Ma,representing the depositional age of the strata. Taking it as the anchor point, combined with the filtering results of the long eccentricity(~405 kyr), a floating astronomical time scale for the Bolila Formation was established, constraining its age to 242.72–235.06 Ma with a duration of ~7.66 Ma, spanning the Middle Triassic Anisian to the Late Triassic Carnian. The formation of the mixed siliciclastic-carbonate rocks in the Bolila Formation is jointly controlled by tectonic evolution and the periodic changes of astronomical orbital parameters. During the Middle-Late Triassic, the Longmu Co-Shuanghu Paleo-Tethys underwent northward subduction, forming a multi-magmatic island arcs provenance supply system in the North Qiangtang Depression, providing sufficient material for mixed siliciclastic-carbonate rocks. Climate fluctuations driven by periodic variations of astronomical orbital parameters further regulated the formation of mixed siliciclastic-carbonate rocks. When long eccentricity and obliquity increased, monsoon intensity enhanced, which led to increased precipitation and intensified surface runoff, increasing terrigenous input and promoting the development of mixed siliciclastic-carbonate rocks; conversely, when long eccentricity and obliquity decreased, monsoon intensity weakened and precipitation reduced, resulting in the lower terrigenous input, facilitating the formation of carbonate rocks.

How to cite: Sui, B. and Wang, Z.: Sedimentary characteristics and genetic mechanism of mixed siliciclastic-carbonate rocks of the Bolila Formation in the eastern Qiangtang Basin , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11345, https://doi.org/10.5194/egusphere-egu26-11345, 2026.

Upper Cretaceous sedimentary successions of the Gurpi Formation in the eastern Lurestan Zone (Zagros Basin, Iran) provide a valuable record of paleo-depth variations during the early development of the Zagros foreland basin associated with Neo-Tethyan closure. This study presents an integrated sedimentological and micropaleontological analysis of the Campanian–Maastrichtian Gurpi Formation exposed in the Zangul anticline in a proximal foreland setting.

Lithofacies observations combined with quantitative planktonic–benthic foraminiferal data and morphotype-based paleoecological analysis were used to reconstruct relative bathymetric changes and evaluate controls on carbonate preservation. Planktonic foraminiferal biostratigraphy constrains the succession from the Globotruncanita elevata Partial Range Zone (middle–late Campanian) to the Gansserina gansseri Interval Zone (early Maastrichtian). A thin fossiliferous marl interval equivalent to the Seymareh Member records a short-lived late Campanian shallowing event related to forebulge development. This phase is followed by progressive deepening into the Maastrichtian, expressed by increasing proportions of deep-dwelling foraminiferal morphotypes.

The upper Gurpi Formation shows a marked decline in foraminiferal abundance and preservation, accompanied by radiolarian-rich micrites, glauconite, and pyrite. These features indicate deposition under low-oxygen and carbonate-corrosive conditions and are interpreted as the result of local shoaling of the lysocline and an effectively shallower carbonate compensation depth in a tectonically active foreland basin, rather than extreme bathymetric deepening. The transition to flysch sedimentation of the Amiran Formation and the presence of slump structures record foredeep development and basin steepening.

Regional comparison across Lurestan demonstrates that Campanian–Maastrichtian depth changes were diachronous and primarily controlled by flexural subsidence and forebulge migration, highlighting the dominant role of tectonics over global eustatic signals in shaping Late Cretaceous basin evolution of the Zagros Basin.

How to cite: Razmjooei, M. J. and Bazvand, A.: Late Cretaceous Paleo-depth Variations in the Zagros Foreland Basin (Iran): Insights into Basin Evolution and Regional Paleoenvironment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11857, https://doi.org/10.5194/egusphere-egu26-11857, 2026.

Seafloor sediment characterization is fundamental to understanding marine environmental processes, including sediment transport, depositional dynamics, and acoustic behavior. However, direct measurements of sediment physical properties such as bulk density and P-wave velocity are often limited by high costs, logistical constraints, and sparse spatial coverage. As a result, large-scale seafloor models frequently rely on simplified or incomplete representations of sediment properties. This study examines the application of sedimentary proxies, specifically elemental concentrations determined by X-ray fluorescence (XRF), to enhance predictions of key physical and acoustic sediment properties.

Sediment cores from the fine-grained New England Mud Patch (NEMP) provide a test case for evaluating proxy-based approaches in a depositional environment dominated by cohesive sediments. Multivariate regression models were developed using both wet and dry XRF measurements to assess how sample preparation influences predictive performance. Results indicate that dry XRF consistently produces stronger elemental signals and higher predictive accuracy than wet XRF, with coefficients of determination (R²) exceeding 0.7 to 0.9 for bulk density and P-wave velocity. These differences reflect the attenuation effects of pore water on elemental detection and highlight the importance of XRF methodology when integrating geochemical data into sediment property models.

Beyond their application to geoacoustic prediction, XRF-derived elemental proxies capture environmentally meaningful variations in sediment composition related to sediment source, grain size distribution, and depositional processes. Incorporating these proxies into statistical frameworks offers a rapid, non-destructive, and cost-effective means of enhancing spatially continuous sediment characterization. This approach supports improved parameterization of seafloor sedimentation models and provides a pathway for reducing uncertainty in marine geophysical analyses and seabed infrastructure assessment and design.

How to cite: Ledezma, K., Pederson, C., Lee, T., and Wallace, D.: Proxy-based characterization of physical properties in fine-grained shelf sediments using X-ray fluorescence, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12262, https://doi.org/10.5194/egusphere-egu26-12262, 2026.

The Swiss Molasse Plateau is the most prominent near-surface geological body across the
entire northern Alpine Foreland and hosts most of Switzerland’s population, cities, and
infrastructure. Molasse sedimentary assemblages are composed of mixed continental and
marine siliciclastic units subdivided stratigraphically into Lower Marine Molasse, Lower
Freshwarter Molasse , Upper Marine Molasse and Upper Freshwarter Molasse . The
Molasse has been extensively used for road and tunnel construction and is a preferential
target for major underground infrastructures, such as CERN’s Future Circular Collider. In
particular, the presumed lateral continuity of sand bodies with good reservoir qualities makes
the Lower Freshwater Molasse (LFM) a potential target for geo-energy storage, such as
heat, and anthropogenic CO₂ sequestration. The success of these projects depends on
detailed rock characterisation, from a thorough understanding of the tectono-stratigraphic
evolution of sedimentary units at basin scale down to sediment composition and reservoir
property distribution. However, understanding and predicting fluid flow in Molasse units is not
straightforward, due to the occurrence of subsurface heterogeneities in the form of variable
geometry and architecture of depositional elements, variable textural and fabric properties of
sediments, and the anisotropy of key reservoir parameters (e.g. porosity, permeability).
Therefore, a comprehensive analysis of borehole records, lithofacies, facies associations,
petrophysical analysis and interpretation of 2D seismic (where possible) was performed in
this study to assess reservoir heterogeneities and structural complexities. This study
integrates multiple datasets, including borehole records (Weiach, Bassersdorf, Rheinau, and
four QHAB wells), outcrops (including the Fisibach Quarry) and 2D seismic datasets with a
focus on the Lower Freshwarter Molasse (LFM) in north-eastern Switzerland. The study
demonstrates how the distribution, dimensions, and stacking patterns of sedimentary
architectural elements vary abruptly across small spatial scale, and how these
heterogeneities can be explained by the original complex pattern of fluvial depositional
environments. The results also emphasize the necessity of bridging regional depositional
models with site-specific characterization to reduce uncertainties in rock-property prediction
and to optimize project planning in complex, heterogeneous fluvio-lacustrine deposits of the
LFM.

How to cite: Akhtar, N., Ventra, D., and Moscariello, A.: Geological storage of CO2 in heterogenous Lower Freshwarter Molasse successions of NE Switzerland: Uncertainties and Opportunities., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12917, https://doi.org/10.5194/egusphere-egu26-12917, 2026.

The hypothesis of aesthetic evolution offers a compelling alternative to traditional view of natural selection by suggesting that trait evaluation can occur independently of immediate survival or reproductive fitness factors. While often viewed as arbitrary or even as detrimental at the individual or population level, aesthetic preferences may function as significant determinants of fitness at the species or clade level. 

In this study, we investigate the palaeontological record of Cervid species. Research suggests that their antlers serve a dual role as both armaments for male-male competition and ornaments for female choice. The evolution of these traits appears to be driven by a complex interplay between male-male competition and female choice, eventually decoupling from purely functional demands. We utilize Bayesian models of Cervid evolutionary histories, allometric data and phylogenetic path analysis in order to investigate possible causal links between antler size, evolutionary success and phylogenetic patterns. 
Our preliminary results aim to clarify the link between antler size and the evolutionary success of specific lineages, offering a foundation for future research into the biotic drivers that shape macroevolutionary patterns.

This study was supported by the grant S-MIP-24-62 BretEvoGeneralized.

How to cite: Bekeraitė, S. and Spiridonov, A.: Is Antler Size Driving Evolutionary Success in Cervids?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13169, https://doi.org/10.5194/egusphere-egu26-13169, 2026.

The Late Albian–Turonian Judea Group represents a significant sequence of shallow-water carbonates deposited across the Israel-Sinai sub-plate. While the biostratigraphy of the Judea Gr. has been extensively studied using ammonites, ostracods and foraminifera, calcareous nannofossil data remain sparse. This study documents the taxonomic composition and stratigraphic distribution of calcareous nannofossils in the Jerusalem and Northern Negev areas, providing a crucial comparative analysis with the high-diversity assemblages of the Carmel area.

To establish this biostratigraphic framework, 281 samples were examined from eight surface sections in the Judea Mountains and three boreholes in the Northern Negev (Kohal 1, Massada 1 and Zohar 1).

Species richness varies significantly from impoverished assemblages in the Jerusalem area (only Moza and Kefar Shaul Fms) (29–60 species) and Negev (33–39), to highly diverse complexes in the Carmel area (95–113).

In the Judea Mts, extremely rare nannofossils in the Kefira Fm. indicate the Upper Albian–Maastrichtian age, the benthic foraminifera indicate the Albian–Cenomanian age, and the presence of Hemicyclammina points to the Middle Cenomanian. In the Soreq Fm., rare nannofossils indicate the Albian–Maastrichtian age and benthic foraminifera specify the Cenomanian age. The Beit Me'ir Fm. is devoid of nannofossils, while benthic foraminifera indicate the Cenomanian age. Diverse nannofossils of the Moza Fm. indicate the Early–early Middle Cenomanian age (Zones UC1–UC2), whereas abundant benthic and scarce planktonic foraminifera point to the Cenomanian age. The Kefar Shaul Fm. is Late Cenomanian based on rich nannofossils (Subzone UC3d, undivided UC3e–Zone UC4 and Subzone UC5a). Rare planktonic foraminifera and ostracods specify the Late Albian–Cenomanian and Late Cenomanian ages, respectively. Rare nannofossils of the Bina Fm. broadly indicate the Upper Albian–Maastrichtian age, and benthic foraminifera point to the Late Cenomanian–Turonian age.

In the Northern Negev Hazera Fm., the nannofossils and ostracods identify the Hevyon Member as Early Cenomanian (Massada 1: nannofossil Zones UC1 and UC2, ostracod Zone UC-1) or Late Albian–Early Cenomanian (Zohar 1 nannofossil undivided Zones UC0–UC1 and Zone UC2; Kohal 1 nannofossil (Sub)Zones: UC0a–b, UC0c–UC1, UC2a, UC2b–c). Nannofossils from the 'En Yorqe'am Member specify the Early–Late Cenomanian age (Zone UC2, undivided Zones UC3–UC4) and the ostracods suggest the Late Cenomanian age (Zone UC-3) in the Massada 1 and Kohal 1 boreholes. The Zafit Member is Middle–Late Cenomanian in all boreholes (nannofossil undivided UC3–UC4 Zones, Subzone UC5a). The Avnon Member is Late Cenomanian (nannofossil Subzones UC5a and UC5b) in Kohal 1.

In the Carmel area, both boreholes yielded rich nannofossil assemblages supporting the Isfiye Fm. as Late Albian, and the Arqan Fm. as Late Albian–Middle Cenomanian (Zones UC0–UC3; foraminiferal zones P. appenninica, Th. globotruncanoides, Th. reicheli and R. cushmani). The Tavasim Volcanics is Late Albian (borehole CT2) or Late Albian–Lower Cenomanian (borehole CT8).

By integrating novel nannofossil data with existing macro- and microfossil zonations, this research establishes a robust framework for correlating lithologically diverse formations of the Judea Gr., filling a significant gap in the regional micropaleontological biostratigraphy.

How to cite: Ovechkina, M.: Biostratigraphic framework of the Judea Group of Israel (Jerusalem, Negev and Carmel areas): A calcareous nannofossil approach. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14379, https://doi.org/10.5194/egusphere-egu26-14379, 2026.

Cores recovered by the Trans-Amazon Drilling Project (TADP) in the Acre Basin provide an unprecedented opportunity to investigate the stratigraphic record in the Andean foreland in the western Brazilian Amazon. This study integrates subsurface data with sedimentological data of correlative units from outcrops along the Juruá River and roadcuts, providing key information on depositional geometry and architectural elements. The entire sampled interval of the core (870 m), except the uppermost 12 m,  is assigned to a single lithostratigraphic unit, identified as the Solimões Formation. The core succession comprises fine- to medium-grained sandstones, siltstones, and mudstones, exhibiting variable degrees of paleopedogenetic alteration. The sand-grade facies are rich in feldspar grains and lithic fragments, displaying a grayish coloration that contrasts with the reddish oxidized hues and locally green-mottled colors observed in more intensely paleoweathered profiles. Four facies associations (FA) are defined: sandy fluvial channel deposits (FA1 and FA2) and finer-grained overbank and floodplain deposits (FA3 and FA4). Facies associations FA1 and FA2 are best represented by deposits exposed along the BR-364 highway in the eastern Acre Basin, where they form channel-dominated sandy successions, with homogeneous successions up to 1.5 m thick. FA3 and FA4 are best represented by deposits exposed along the Juruá River riverbanks in the western Acre Basin, characterized by laterally extensive tabular beds intercalated with thin sandy bodies deposits forming fine-grained heterolithic deposits, generally with well-developed paleoweathering features and cemented by calcite. Subsurface deposits from the core record a phase of long-term aggradation associated with foreland basin subsidence. These facies are interpreted as bar top deposits transitioning into floodplain environments of a large alluvial system, with very limited occurrence of lacustrine sequences. The limited lateral accretion in floodplain or shallow pond environments was subject to repeated subaerial exposure with prolonged floodplain stability under waterlogging and/or seasonal discharge variability. Further refinement of these interpretations, together with ongoing geochronological and geochemical analyses, should help to improve our understanding of Amazonian basin development and its linkage to climate and tectonic change through the Late Miocene and Pliocene.

How to cite: Bezerra, I. S., Almeida, R., Geraldo, G., Gomes, P., Figueiredo, F., Althaus, C., Janikian, L., Galeazzi, C., Sawakuchi, A., Fritz, S., Noren, A., Guizan, C., and Baker, P.: Subsurface and outcrop characterization of large fluvial channel deposits of the Late Cenozoic Solimões Formation (Acre Basin, western Amazonia)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14819, https://doi.org/10.5194/egusphere-egu26-14819, 2026.

Abstract: Early Permian sedimentation within the Gondwana intracratonic basins provides
important insights into the sedimentation history. Integrated petrographic and geochemical
proxies offer an effective means to reconstruct these processes. This study examines
siliciclastic rocks—sandstone, shale, and sandstone–mudstone heteroliths from the Permian
Barakar Formation of the West Bokaro Basin, eastern India. The rocks were analysed for
their mineralogical and geochemical properties to interpret provenance, paleoclimate, paleo-
tectonic setting, paleoredox conditions, and paleo-depositional environment. XRD, SEM, and
petrographic analyses, accompanied by major and trace element chemistry, supported by REE
patterns normalized to PAAS and UCC, indicate a predominant felsic provenance, which is
potentially considered to be the granite-granodiorite rocks of the Proterozoic Chhotanagpur
Gneissic Complex, Singhbhum cratonic block. Higher CIA values with A–CN–K plots, along
with MFRW weathering trends, suggest intense chemical weathering under a warm, humid
climate. Relative abundance of redox-sensitive trace elements (e.g., V, Ni, Cu, Zn, Ce, etc.)
points to oxic-dysoxic (for sandstone) and dysoxic-anoxic (for shale) conditions, often
supported by presence of localized pyrite framboids and abundant organic matter in shales
and heteroliths. Tectonic discrimination diagrams indicate deposition in a passive margin
riftogenic basin. Binary and ternary plots of common major element oxides suggest a
continental-marine transitional depositional setting, indicating marine incursions within the
continental Gondwanaland. The results and the interpretations provide important clues
regarding the Early Permian post-glacial warm paleoclimatic transition within the broader
Gondwana paleogeographic-paleoclimatic framework.

How to cite: Banerjee, M., Bhattacharya, B., Pathak, A., and Bhattacharya, A.: Geochemical Perspectives on the Permian Barakar Formation, Gondwana Supergroup, WestBokaro Basin, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18078, https://doi.org/10.5194/egusphere-egu26-18078, 2026.

The Gadvan Formation (Barremian–Aptian) in the Persian Gulf represents a heterogeneous mixed carbonate–siliciclastic succession with important implications for depositional architecture and reservoir characterization. In this study, fourteen distinct microfacies (MF-1 to MF-14) were identified based on detailed core descriptions and petrographic analysis of thin sections from five wells across several oil fields.

Outer-ramp facies (MF-1 to MF-4) are dominated by mud-supported argillaceous bioclastic mudstones and wackestones, radiolarian- and sponge spicule–rich wackestones, and planktonic foraminiferal wackestones, reflecting low-energy open-marine deposition below the storm wave base. Middle-ramp facies (MF-5 to MF-8) comprise echinoderm-rich wackestones, orbitolinid wackestones, benthic foraminifera–echinoderm wackestones, and sandy bioclastic facies, indicating moderate-energy open-marine conditions with episodic siliciclastic input. Inner-ramp facies (MF-9 to MF-13) include peloidal packstones to grainstones, Lithocodium floatstones to boundstones, and green algae–benthic foraminiferal wackestones, representing shoal, back-shoal, and semi-restricted lagoonal environments. Coastal to proximal depositional settings (MF-14) are characterized by argillaceous sandstones and scattered quartz grains, reflecting sporadic terrigenous supply from nearby continental sources.

The vertical and lateral distribution of these microfacies documents deposition on a homoclinal carbonate ramp that locally evolved into a distally steepened geometry, particularly in the northwestern part of the Persian Gulf. Shoal complexes acted as barriers separating open-marine conditions from restricted lagoonal settings. This microfacies-based framework improves the depositional model of the Barremian–Lower Aptian Gadvan Formation on the northeastern Arabian Plate and provides a robust basis for regional correlation and reservoir-scale interpretation.

How to cite: Yari Nejad, A., Farahpour, M. M., Yousefi Yeganeh, B., and Wagreich, M.: Microfacies Distribution and Depositional Environments of the Lower Cretaceous Gadvan Formation (Barremian–Aptian) in the Persian Gulf, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19154, https://doi.org/10.5194/egusphere-egu26-19154, 2026.

Marginal-marine successions deposited in restricted basins under arid conditions are characterised by complex interplay between variable hydrodynamic conditions, localised carbonate-evaporitic production and continental surface processes. In such scenario, climatically driven shifts of depositional belts may result in stratigraphic compartmentalisation through vertical facies and environments dislocation. As importantly, accommodation variations across marine margins can lead to preferential deposition of coeval systems which may ultimately translate into stratigraphic sealing through lateral facies transition. By deciphering the relative influence of allogenic controls upon marine margins stratigraphic architectures in arid and restricted settings and by documenting their sedimentary products, this work provides a generalised sequence stratigraphic model for arid epicratonic basin fills.

Stratigraphic arrangement of mixed paralic deposits is investigated across two margin-perpendicular transects of the Middle to Upper Jurassic San Rafael Group in Utah. Transgressive sequences of the Carmel and the Curtis formations deposited during flooding events of the Sundance Sea are intercalated between the aeolian- to fluvially-dominated low stand deposits of the Entrada Sandstone and the Summerville Formation. Facies changes and sequence stratigraphic surfaces are documented through detailed sedimentary logging and architectural panel interpretations at locations representative of 1) sediment-supply and accommodation controlled continental basin flanks; 2) autogenically overprinted paralic basin margin settings; 3) climatically controlled basin centre. Gamma-ray log data were collected in parts of the basin characterised by differing tectonics settings.

Successions deposited during transgressions are dominantly associated with complex tidal embayments reworking contemporaneous continental sediment deposited further inland and may present contrasting architectural and lithological characteristics linked to variability in basin physiographic settings and climatic conditions. Transgression sequences are generally recorded as composite surfaces in continental basin flank settings although thin fluvial deposits may locally be preserved in the case of favourable accommodation and sediment supply conditions. Sedimentary successions deposited during relative sea-/base-level low stands are characterised by the advance of aeolian systems during aridity maximums and translate basinward to coastal unconfined large-scale alluvial accretion successions. Maximum regression surfaces are associated with terminations of aeolian dune fields. High-frequency climatic fluctuations are preferentially recorded in continental basin flank settings during regressive trends as aeolian dune field growth stages bounded by deflationary supersurfaces. Larger-scale T-R sequential frameworks and their associated spatio-temporal facies evolution are more likely to be controlled by overarching changes in rates of accommodation creation due to foreland basin tectonics. By incorporating spatial facies variations within stacking trends at a basin scale, the proposed model highlights the architectural complexity and facies diversity of depositional sequences within arid epicratonic basins and may constrain reservoir characteristics and associated stratigraphic heterogeneities.

How to cite: Hême de Lacotte, V., Clarke, S., Zuchuat, V., and Button, O.: Sequence stratigraphic model for epicratonic basin fills in arid settings, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20088, https://doi.org/10.5194/egusphere-egu26-20088, 2026.

Hadal trenches uniquely preserve exceptional sedimentary archives of past geological events, yet their depositional processes remain poorly constrained. The Japan Trench captures complex earthquake-triggered event beds that record repeated sediment-gravity flows that deliver terrigenous and biogenic material into the trench, influencing both paleoseismic reconstruction and deep-sea carbon cycling on multi-millennial timescales. Classical event stratigraphy treats these event beds as the product of a brief, isochronous process. This study aims to build on this concept to enable the documentation of relative depositional timing within a single event bed. Within four well documented historical earthquake-triggered beds recovered during IODP Expedition 386 and linked to megathrust earthquakes (CE 2011 Tohoku-Oki, CE 1454 Kyotoku, CE 869 Jogan, and ~2.3 ka), we develop a systematic, facies-based framework to identify event-internal characteristics. This integrated approach resolves sedimentary structures—physical, chemical and biogenic characteristics—by combining visual core description with high-resolution 2D and 3D imaging (X-ray computed tomography and X-ray radiography), grain-size measurements, and geochemical datasets (X-ray fluorescence). Six event-internal facies (F1–F6), bounded by hemipelagic facies (F0), form a fining-upward sequence that records the shift from high-energy, non-cohesive, bedload-dominated flows to low-energy, cohesive, suspension-dominated deposition. This shift is marked by a 32 µm grain-size threshold that separates coarse-grained (F1–F3; >32 µm) from fine-grained (F4–F6; <32 µm) facies. Grain-size breaks at this threshold mark the transition from non-cohesive to cohesive deposition, and from bed-load to suspended-load dominated regimes. Event-internal facies organize into pulses and pulse groups that stack hierarchically into three patterns: single-pulsed, multi-pulsed and amalgamated. The amalgamated pattern comprises two or more single- or multi-pulsed successions separated by breaks in the fining-upward trend. Breaks marked by opportunistic trace fossils or by F6 indicate pauses during deposition (quasi-synchronous flows); whereas their absence suggests synchronous flows. Most event beds are amalgamated and comprise flows emplaced at different times and sourced from different directions, as reflected by variable composition, facies, and paleo-flow indicators. Basin physiography strongly influences facies development and deposit thickness: basin highs record erosion–deposition stages, whereas depocenters favor ponding turbid water masses in prolonged suspension, producing thick fine-grained tops. Here, transitional facies (F4) forms where new flows interact with the still-settling suspension clouds, allowing interpretation of complex mainshock–aftershock sequences; this process is enhanced in depocenters but absent at basin highs. By providing new insights into hydrodynamic conditions, relative depositional timing and duration of event bed deposition in hadal trenches, the resulting facies-based framework advances the event stratigraphy concept and improves global understanding of deep-marine and hadal sedimentary dynamics and supports the use of hadal event beds as robust natural archives of mainshock–aftershock and source-to-sink processes.

How to cite: Muthre, M., Proust, J.-N., Pizer, C., Ikehara, K., Huang, J.-J. S., Naruse, H., and Strasser, M.: Facies analysis provides new insights into event bed deposition in a hadal trench environment , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20371, https://doi.org/10.5194/egusphere-egu26-20371, 2026.

The reconstruction of detrital flux, paleoclimate, paleosalinity, paleo-primary productivity, paleohydrodynamic conditions, and paleo–water depth enhances the understanding of sedimentary processes and their drivers in deep-time greenhouse-icehouse transitions such as the Eocene to Oligocene times. This study uses detailed geochemical analyses of major oxides and trace elements in sediment samples collected from the Beni Suef Formation (Bartonian–Priabonian) and the Maadi Formation (Priabonian) in the southern Tethys shelf (Egypt, northeastern Desert). Detrital proxies, including Si/Al, Ti/Al, and Zr/Al, indicate an enhanced influx of terrigenous sediments in the middle portion of the Qurn Member of the Beni Suef Formation, as further supported by noticeable facies variations, particularly the transition from shale to coarser silt- and sand-sized fractions. Paleoclimate indicators (Sr/Ba, Rb/Sr, K₂O/Al₂O₃, and Sr/Cu) point to a climatic shift from humid to arid conditions, consistent with the regional Late Eocene aridification across the Tethyan realm. Paleosalinity proxies (Sr/Ba, Ca/Al, and Mg/Al*100) suggest episodic intensification of open marine influence and a reduction in freshwater input, with the upsection increase in Sr/Ba ratios, reflecting phases of enhanced marine water settings or decreased terrestrial runoff. Primary productivity was evaluated using multiple geochemical proxies such as P, Ni/Al, Cu/Al, P/Al, P/Ti, and Babio ratios, which collectively indicate generally low primary productivity interrupted by intervals of enhanced paleoproductivity or increased organic matter export to the sediments. This interpretation is further supported by the low total organic carbon (TOC) values. These results highlight the sensitivity of the southern Tethys shelf to Middle–Late Eocene climatic variability and the key role of prevailing paleoenvironmental conditions in controlling sediment supply, water chemistry, and biological productivity.

How to cite: Mohamed, M., Wagreich, M., Heinz, P., Abd El-Gaied, I. M., Gier, S., Wolfgring, E., El-Kahawy, R., Ali, A. G., Mannaa, A., Haredy, R., and Sayed, D. M.: Deciphering Middle-Upper Eocene Environmental Conditions Using Geochemical Trends: Insights from Beni Suef area, Northeastern Desert, Egypt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20784, https://doi.org/10.5194/egusphere-egu26-20784, 2026.

The stratigraphic relationship between flowstones and clastic cave deposits in the Cradle of Humankind (Cradle) UNESCO World Heritage Site is central to establishing the ages of key hominin-bearing sequences. A recent petrographic synthesis suggested that intrusive flowstones do not occur in the Cradle, implying that all flowstones represent conformable depositional breaks and provide reliable chronological constraints. Our new field observations from the Gladysvale Cave challenge this interpretation and document a clear example of intrusive flowstone formation within fossil-bearing sandstone. The observed carbonate body penetrates the sandstone along bedding planes and fractures, incorporating angular clasts and forming irregular, cross-cutting, and vein-like geometries. These field relationships demonstrate the precipitation of calcite from infiltrating CaCO₃-rich fluids into pre-existing voids, which postdate clastic deposition and partial lithification. The intrusive flowstone displays multiple sub-packages with interfingering terminations, abundant small to large-sized cavities, and lateral offshoots that wrap around brecciated clasts. Such geometries are diagnostic of intrusion rather than surface accretion. The Gladysvale example provides definitive field evidence that intrusive flowstones occur within fossil-bearing deposits of the Cradle and can mimic the morphology of primary depositional flowstones. Their recognition is essential for correctly interpreting speleothem–clastic relationships and for refining the chronological framework of hominin-bearing cave systems.

How to cite: Makhubela, T. V., Berger, L. R., Onyeogu, T., van Rooyen, L., and Hawks, J.: Field Evidence for Intrusive Speleothem Formation in the Cradle of Humankind, South Africa, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21414, https://doi.org/10.5194/egusphere-egu26-21414, 2026.

Proboscideans (Afrotheria, Paenungulata) have been found in Early Miocene layers of Portugal. The oldest specimens of proboscideans in Portugal have been found in the Targus Basin. The Museo Geológico in Lisbon, Portugal, houses teeth of Early to Middle Miocene proboscideans from the Lisbon area. These remains have been ascribed to the genera: Deinotherium, Serridentinus, Trilophodon, and Zygolophodon. Serridentinus and Trilophodon are recognised as synonym for Gomphotherium. However, specimens in Portugal ascribed to Zygolophodon are most likely misinterpreted and instead belong to Gomphotherium. The current consensus is that Gomphotherium and Deinotherium are the only two genera present in the Early Miocene of Portugal. They migrated to the Iberian Peninsula from France in two separate events. Dinotherium reached Portugal later than Gomphotherium, most likely due to a change in the vegetation following the Miocene Climatic Optimum. Platybelodon may also have been present in Portugal at this time. Here, we study the Early Miocene proboscidean teeth from the Museo Geológico in Lisbon. We analysed and compared the teeth morphometrically to deduce the taxonomic diversity and morphological variability. These results can further be related to the environmental conditions and the diet of proboscideans in the Early Miocene of Portugal.

How to cite: Cincinnatus, K., Rios, M., and Roures, V.: Taxonomic Diversity and Morphological Variability of Proboscidea from the Early Miocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22335, https://doi.org/10.5194/egusphere-egu26-22335, 2026.

Salse di Nirano (Fiorano Modenese, Italy) host one of the largest mud volcano fields of Europe. They are positioned upon an anticline structure of the NE-verging fold-and-thrust Northern Apennine belt and emit fluids mainly consisting of clay mud, saline water and hydrocarbons (liquid and gas). Like most of the world’s mud volcanoes, their gas emissions are primarily composed of methane (> 98%), with minor contributions from carbon dioxide, nitrogen, and other hydrocarbons (Mazzini and Etiope, 2017). Two main fault and fracture systems (one NW-SE oriented and the other SW-NE/ENE-WSW oriented) allow fluids migration to the surface (e.g., Bonini, 2008). From a geomorphological point of view, Salse di Nirano are placed within a caldera-like depression presumably formed by progressive collapse due to degassing (e.g. Bonini, 2008) or as the final stage of mud diapir evolution (Castaldini et al., 2005).

As many world’s mud volcanoes, Salse di Nirano activity is closely linked to tectonic processes (Martinelli and Ferrari, 1991; Bonini, 2009). With the aim of studying the interplay between geofluids and seismicity, a multiparametric monitoring system was set up in 2023. Two distinct mud pools were selected for the continuous monitoring of mud level/density, temperature and electrical conductivity. In addition, a permanent station measuring CO₂ flux diffused by the soil was installed at the edge of the mud volcanoes field, where higher gas fluxes were detected (Ferrari et al., 2024). Recently, the station has been upgraded with a methane sensor. A meteorological station and a velocimeter were installed to monitor the atmospheric parameters and the seismic activity of the area, respectively.

Overall, the multiparametric monitoring system continuously recorded about two years of data. Periodic oscillations were identified, with some anomalous variations of mud level, temperature, electrical conductivity and soil gas flux that have been compared with environmental data (meteorological and soil-related) and seismicity. Notably, synchronous changes in mud pools electrical conductivity and soil CO₂ fluxes were detected in relation to two distinct seismic swarms occurred in February and August 2024. In addition, differences in the behaviour of the two mud pools were also observed throughout all the time-series and presumably point to extremely local conditions influencing the common feeding system. All these observations highlight the efficiency of the presented continuous multiparametric monitoring system in inferring new insights on mud volcano crustal fluids dynamics. This work reports the results achieved in the framework of the INGV-MUR project Pianeta Dinamico.

References

Bonini, M.; 2008: Geology Vol. 36, pp. 131-134, https://doi.org/10.1130/G24158A.1.

Bonini, M.; 2009: Tectonophysics Vol. 474, pp. 723-735. doi:10.1016/j.tecto.2009.05.018.

Castaldini, D., Valdati, J., Ilies, D.C., Chiriac, C., Bertogna, I.; 2005: Italian Journal of Quaternary Sciences Vol. 18, n. 1, pp. 245-255.

Martinelli, G., Ferrari, G.; 1991: Tectonophysics Vol. 193, n. 4, pp. 397-410, https://doi.org/10.1016/0040-1951(91)90348-V.

Mazzini, A., Etiope, G.; 2017: Earth-Science Reviews Vol. 168, pp. 81-112, http://dx.doi.org/10.1016/j.earscirev.2017.03.001.

Ferrari, E., Massa, M., Lovati, S., Di Michele, F., Rizzo, A.L.; 2024: Frontiers in Earth Science Vol. 12, n. 1412900, pp. 1-26, https://doi.org/10.3389/feart.2024.1412900.

How to cite: Ferrari, E., Rizzo, A. L., Capelli Ghioldi, G., Sciarra, A., Tamburello, G., Viveiros, F., Lovati, S., and Massa, M.: Earthquake-related fluids behaviour at Salse di Nirano mud volcano field (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1738, https://doi.org/10.5194/egusphere-egu26-1738, 2026.

Natural gas seeps and mud volcanoes are widely distributed across terrestrial and shallow submarine sedimentary basins and contribute considerable amounts of fossil methane to the atmosphere. Methane emissions from these systems are commonly interpreted as dominantly thermogenic in origin; however, microbial activity may significantly contribute to, or overprint, these emissions through secondary methanogenesis or methane oxidation during gas migration and storage.

Conventional bulk isotope composition (δ¹³C and δD) and hydrocarbon concentration ratios are often insufficient to distinguish secondary microbial contributions from an initial thermogenic source. Independent of bulk isotopic signatures, methane clumped isotopes (Δ¹³CH₃D and Δ¹²CH₂D₂) provide direct constraints on methane formation pathways and post-generation alteration processes.　Recent studies have revealed low-temperature near-equilibrium clumped-isotope signatures in mud-volcano systems in Azerbaijan¹, indicative of strong microbial overprinting, whereas methane from Japanese mud volcanoes exhibits clumped isotope signatures spanning from far from equilibrium to near equilibrium values². For the latter, clumped isotope signatures of methane correlate with ¹³C-position-specific isotope composition of propane, suggesting the biodegradation of higher hydrocarbons is associated with progressive modification of methane clumped isotopes.

Here, we investigate methane emissions from mud volcanoes and gas seeps in central and southern Italy (n = 14) and Romania (n = 15). Methane bulk and clumped isotope composition (δ¹³C, δD, Δ¹³CH₃D and Δ¹²CH₂D₂) are analyzed using a quantum cascade laser absorption spectrometer (QCLAS) equipped with a customized gas-inlet system at Empa³. Propane concentrations span from below detection to 0.8%, indicating a wide range of potential microbial influence. Selected samples are further characterized by propane position-specific isotope analyses at Science Tokyo following established protocols by Gilbert et al. ⁴, providing constraints on the extent of secondary microbial processes affecting higher hydrocarbons.

Preliminary clumped-isotope results from Italian mud volcanoes indicate near-equilibrium signatures consistent with strong microbial influence, comparable to patterns reported from Azerbaijan mud-volcano systems. In contrast, Romanian samples exhibit pronounced variability in propane concentrations, providing a critical test case to explore whether methane clumped-isotope systematics transition toward more thermogenic-dominated patterns with secondary microbial influence, similar to those observed in Japanese systems. By integrating new datasets from Italy and Romania with published clumped-isotope and propane intramolecular isotope data, this study explores whether microbial influences on methane emissions follow consistent or system-specific patterns across mud-volcano and gas-seep systems globally.

[1] Liu et al., 2023 Geology

[2] Gilbert et al., 2025 EGU2025 Abstract

[3] Zhang et al., 2025 Anal. Chem.

[4] Gilbert et al. 2019 Proc. Natl. Acad. Sci.

How to cite: Zhang, N., Meissner, J., Kueter, N., Bernasconi, S., Emmenegger, L., Baciu, C., Lupulescu, A., Sciarra, A., Grassa, F., Mazzini, A., Gilbert, A., Yamada, K., Ueno, Y., and Mohn, J.: Clumped isotope signatures of methane from mud volcanoes in Italy and Romania: implications for microbial activity , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5050, https://doi.org/10.5194/egusphere-egu26-5050, 2026.

This study presents a comparative analysis of the two key example of sedimentary volcanism in Italy: the mud volcanoes of Salse di Nirano (Northern Italy) and the Maccalube of Aragona (Sicily). Mud volcanoes are not related to magmatic activity but result from the ascent of gas, mainly methane, which transports mud, water and fine-grained sediments to the surface These systems represent natural laboratories for investigating subsurface fluid migration, gas-driven processes, and their surface expressions.

At both sites, mud and fluid samples were collected to perform geochemical, mineralogical, magnetic, and paleontological analyses, providing integrated constraints on fluid sources, sediment provenance, and mud volcano dynamics

Despite their apparent similarities, the two sites display markedly different genetic mechanisms and activity style. The study is carried out within the framework of the INGV-MUR project Pianeta Dinamico, called PROMUD.

The Nirano mud volcanoes are characterized by slow and persistent activity, forming small and stable mud cones and bubbling pools. This behavior reflects the compressional tectonic setting of the Northern Apennines, where fractures facilitate the upward migration of fluids and hydrocarbons. The extruded material mainly consists of ARGILLE SCAGLIOSE, the main constituent of the volcanoes, marly clays rich in CaCO₃, and Plio-Pleistocene clay sediments, while saline waters indicate an ancient marine depositional environment.

In contrast, the Maccalube of Aragona area exhibits highly variable and sometimes violent activity, with bubbling mud pools and sudden eruptive events. Here, the mud composition derives from poorly consolidate shallow clayey sediments, and methane is generated within organic-rich sediments. Brackish waters are likely derived from compaction processes of marine sediments.

The comparison highlights how similar fluid-driven process can produce contrasting surface features, levels of activity and hazard scenarios.

How to cite: Misiti, V., Pinzi, S., Sciarra, A., Grassa, F., Cascella, A., and Venuti, A.: Mud volcanoes as natural laboratories for fluid-driven processes: a comparison between Nirano and Aragona (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5222, https://doi.org/10.5194/egusphere-egu26-5222, 2026.

Mud volcanoes represent key natural pathways for the transfer of deep-seated fluids to the surface, yet their gas composition and degassing behavior can vary significantly depending on geological setting and post-genetic processes. Here we present a comparative geochemical and monitoring-based study of mud volcano systems from Azerbaijan and Northern Italy, integrating molecular composition, stable isotopes (δ¹³C-CH₄, δ²H-CH₄, δ¹³C-CO₂) and soil gas flux measurements, to investigate the dynamics of crustal fluid circulation and the release of climate-relevant gases to the atmosphere.

Azerbaijani mud volcanoes are characterized by CH₄-dominated gases with variable contributions of CO₂ and higher hydrocarbons, wide ranges in C₁/C₂⁺ ratios, and isotopic signatures indicating predominantly thermogenic methane, locally affected by secondary microbial processes and mixing during migration. These systems commonly display significant and spatially focused CH₄ and CO₂ fluxes, reflecting active and deep-rooted fluid pathways, and highlighting an efficient transfer of deep fluids to the atmosphere and a potentially significant role in natural greenhouse gas emissions.

Northern Italian mud volcanoes are also characterized by CH₄-dominated gases with low content of CO₂ and wide ranges of C₁/C₂⁺ ratios, but isotopic signatures indicate a dominant secondary microbial methane origin, associated with biodegradation of hydrocarbons and subsequent methanogenesis, producing isotopically heavy CO₂. Soil gas flux measurements are generally lower than those reported for Azerbaijan mud volcanoes, suggesting that deep-sourced gases are largely attenuated by shallow processes and limited near-surface permeability.

The comparison highlights how mud volcanoes with similar surface expressions can reflect markedly different subsurface processes, fluid sources and degassing dynamics. These results emphasize the importance of integrated geochemical characterization and monitoring to 1) properly assess mud volcano activity, 2) their contributions to greenhouse gas emissions and 3) their environmental and societal implications including associated geohazards.

How to cite: Sciarra, A. and Mazzini, A.: Comparative gas geochemistry and degassing behavior of mud volcanoes: insights from Azerbaijan and Northern Italy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8482, https://doi.org/10.5194/egusphere-egu26-8482, 2026.

Mud volcanoes are highly dynamic geohazard environments in which surface conditions can change over very short timescales due to episodic mud extrusion, flow, drying, cracking and oxidation. The resulting landscapes are spatially heterogeneous and typically include mixtures of fresh and weathered mud, crusted deposits, bare soil and dense or sparse vegetation. Considering the opportunities offered by deep learning for environmental monitoring, a consistent categorization of these surfaces is essential to quantify spatial patterns through time and to assess the evolution of active areas. However, progress is often limited by the lack of high quality, domain-specific labelled datasets. This gap slows the adoption of deep learning models in specialized environmental settings such as mud volcanoes, because the most readily available training datasets are largely drawn from urban and human-centered contexts. While manual annotation can partially compensate for limited training data, it is labor-intensive and difficult to standardize across operators, especially where class transitions are gradual and boundaries are diffuse rather than sharp.

This study investigates how multispectral orthophotos can support separation of key mud volcano surface features and thereby accelerate mask creation for dataset generation. We present a case study at the Aragona mud volcano field (Sicily, Italy), called the Maccalube, using imagery acquired with a DJI Mavic 3 Multispectral and processed into an orthomosaic with Agisoft Metashape. We first evaluated common soil and vegetation oriented spectral indices as separability baselines. In this setting, however, baseline indices can be ambiguous because wet clay-rich substrates and thin surface water films may yield intermediate responses that overlap low cover vegetation. We additionally tested common rapid segmentation methods on the RGB orthomosaic including K-means, Simple Linear Iterative Clustering and Segmentate Anything.  These algorithms show poor performance, often merging distinct classes and fragmenting individual ones, which requires substantial manual correction.

We therefore introduce a practical band combination that integrates information from the visible channels with the red-edge and near-infrared bands to improve discrimination between vegetation, wet mud and drier or more weathered mud areas. The calculation is constructed in two steps: first, the visible channels are combined into a neutrality term that increases when RGB responses are similar (low color contrast). Second, this term is multiplied by an inverted red-edge contrast component derived from the near-infrared and red-edge bands, reducing the output where a strong red-edge rise is present. The result of the proposed band combination is a pre-labelling layer that can be thresholded to generate candidate masks with improved vegetation suppression. Remaining ambiguities are mainly confined to non-vegetated materials with similar dark appearance, including very fresh dark mud versus other bare substrates.  Overall, the workflow offers a practical way to accelerate mask creation in domains where labelled data are limited. It supports the rapid development of domain specific training datasets for deep learning applications, in light of future automated monitoring of these environments.

How to cite: Guastella, M., Martorana, R., Pisciotta, A., and D'Alessandro, A.: Multispectral pre-labelling workflow for mud volcano training datasets: a case study at the Maccalube of Aragona, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12274, https://doi.org/10.5194/egusphere-egu26-12274, 2026.

We describe the design, implementation, and evaluation of a combined monitoring tasks to better understand a mud volcano (MV) activity, in the framework of INGV Pianeta Dinamico – MT-PROMUD project. The study site is the Maccalube d’Aragona (Sicily, Italy) protected reserve, hosting a MV field. Maccalube MV is characterized by continuous low-energy emissions of mud, water and gases (mainly CH₄) as well as episodic paroxysmal eruptions. During the 2014 paroxysm, two children were buried by the mud fallout, and the site has been under judicial seizure for several years, until early 2025.

Starting from 2023, we carried out a series of pilot studies and consultations to design a monitoring network and to plan simultaneous acquisitions of multidisciplinary signals and spot surveys. The resulting monitoring strategy includes: 1) permanent instrumentation, acquiring in a continuous mode, seismic signals, meteorological parameters, soil temperature, apparent volumetric water content, Temperature, Electric Conductivity and water column pressure (CTD) in the mud pool; 2) mobile devices, for spot acquisitions of mud emitting vents positions (GNSS), tromographies, hydrophone recordings for acoustic soundscape characterization, apparent soil volumetric water content and environmental radioactivity measures, (focused on ²²²Rn and ²²⁰Rn emissions), and geoelectrical tomographies; 3) sample collections of plants  for metabolomic analysis, water and gas emitted from MV and mud pools for chemical and isotopic analyses, mud for magnetic, micropaleontological and mineralogical investigations. All spot surveys were documented with photographic reportages.

This monitoring system enabled the acquisition of high quality and unique data associated with the paroxysmal eruption of 29 August 2025, as well as variations in MV activity in occasion of a local earthquake.

Our combined and multidisciplinary approach provided a comprehensive picture of mud volcanoes functioning and can serve as a model to assess the need for future monitoring of other mud volcanoes.

How to cite: Bellucci Sessa, E. and the Maccalube Team: The Maccalube d’Aragona mud volcano Monitoring System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13197, https://doi.org/10.5194/egusphere-egu26-13197, 2026.

On 22–23 April 2025, a seismic noise survey was carried out at the Maccalube di Aragona mud volcano field (Sicily, southern Italy), with the aim of investigating the characteristics of the background seismic signal related to vent activity, and the shallow subsurface structure. The experiment, named DEMETRA (DEnse MaccalubE TRomino Acquisition), was conducted within the INGV–PROMUD multidisciplinary research project, aimed at identifying diagnostic indicators of mud volcano activity and potential precursors of paroxysmal events. Ambient seismic noise was acquired at 21 sites using three-component, 24-bit digital tromograph deployed with a high spatial density across vent zones and surrounding areas. The data analyses include spectral characterization, horizontal-to-vertical spectral ratio (HVSR) computation, and estimate of the polarization pattern of the recorded signals. The HVSR results do not reveal distinct amplification peaks but instead show site-dependent deamplification features. Polarization analysis highlights coherent directional patterns within the vent areas. Furthermore, transient signals embedded in the background noise were detected at some sites; their spectral content and polarization properties suggest a possible association with degassing processes, mud emissions, or surface bubbling phenomena. Owing to its dense spatial coverage, the DEMETRA experiment provides a valuable dataset for improving the understanding of subsurface properties and dynamic processes in active mud volcano systems.

How to cite: Petrosino, S., Cusano, P., Madonia, P., and Gucciardo, D.: DEMETRA - A Seismic Noise Survey at the Maccalube di Aragona Mud Volcanoes: Results and Perspectives, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16824, https://doi.org/10.5194/egusphere-egu26-16824, 2026.

Halophytic species thriving in these environments display remarkable phytochemical resilience through specialized metabolite production. In Atriplex sagittata Borkh. (Nirano), 64 compounds, including flavonoids and phenylethylamine alkaloids, were identified. Sulfated flavonoids and alkaloids were enriched in populations exposed to higher salt inputs (Na⁺, Cl⁻, Br⁻). Similarly, Puccinellia fasciculata (Torr.) E.P.Bicknell exhibited enhanced production of sulfated flavonoids and alkaloids in the more saline soil of Ferdinando cone, and its polar extract inducing up to 85.3% mortality in Drosophila melanogaster, indicating environmentally triggered bioactive defenses. We studied the metabolome of Lavatera agrigentina Tineo and Suaeda vera Forssk. ex J.F.Gmel collected in Maccalube Nature Reserve and in a nearby stress-free environment. Analysis of the hydroalcoholic extract of S. vera using by LC-MS revealed a rich phytochemical profile, including flavonoids and sulphated flavonoids, phenylethylamine alkaloids and phenolic compounds. Similarly, HR-ESI-MS analysis of L. agrigentina identified metabolites such as flavonoids, coumarins, and terpenes. Comparative analysis showed that plants from the stress-free environment  produced lower levels of abscisic acid, glycosylated, and sulphated derivatives.

Radionuclide measurements in soils, mud and water pools complemented the botanical observations, revealing significant site-specific behavior. High concentrations of radon (²²²Rn) were detected exclusively at active mud emission centers, correlating with gas bubbling flows. Gamma spectrometry of mud, soil, and plant tissues (²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs) indicated generally homogeneous distributions; however, ⁴⁰K levels in dried plants were linked to biological activity, suggesting an interplay between vegetation and the radioactive properties of volcanic substrates.

This study, conducted on both Nirano and Maccalube Nature Reserves, was supported by the PROMUD (PROtocol for MUD volcanoes) project, funded by the Italian Ministry of University and Research INGV Pianeta Dinamico Project. The results show how the  plant species, particularly halophytes, can modulate their specialized metabolite pathways in response to environmental stressors in sedimentary volcanic settings. These findings underscore the value of sedimentary mud volcanoes as natural laboratories for studying environmental stress adaptation and biogeochemical interactions.

How to cite: De Lauro, E., Falanga, M., Alizadeh, Z., De Tommasi, N., Forlano, P., Giunti, G., Gucciardo, D., Rosa, E., Mancini, S., Sciarra, A., and Cusano, P.: Biodiversity and Environmental Stressors: Some applications to mud volcanoes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17707, https://doi.org/10.5194/egusphere-egu26-17707, 2026.

Mud volcanoes are key geo-environmental features, particularly in central Italy, where their origin is linked to the interaction between tectonics, fluid migration, and high sedimentation rates. In the Monteleone di Fermo area (Marche Region), these structures are aligned with active thrust faults and anticlines of the Marche–Abruzzi system. Despite their relevance as geo-heritage sites and their potential as geohazard indicators, a significant gap persists in the knowledge of their subsurface architecture. Previous studies have focused primarily on compositional aspects and geomorphological descriptions, proposing contrasting triggering and fluid transport mechanisms.This work constitutes a pioneering study in the geophysical characterization of the Monteleone di Fermo mud volcanoes, aiming to define their near-surface geometry and distribution. A multi-parametric approach was applied, integrating full-waveform 3D Electrical Resistivity Tomography (ERT) and 2D seismic refraction tomography (P- and S-wave velocities). Results show distinctive geophysical signatures associated with the system’s saturation state and mud accumulation. The 3D ERT imaging, reaching effective depths of nearly 100 m, shows a slight resistivity contrast between mud bodies (ρ = 10–15 Ω·m) and the hosting clay-rich deposits with lower resistivity (ρ = 8–10 Ω·m). Seismic tomography reveals a marked contrast between the mud edifice and the hosting sediments. In particular, Poisson’s ratio increases (ν > 0.45), indicating the presence of fully saturated muds intruding the clay-rich sediments (ν = 0.35–0.40).These results demonstrate both the feasibility and limitations of full-waveform geo-electrical data for deep 3D resistivity imaging in clay-rich sediments, testing the detectability of mud-volcano structures under low resistivity-contrast conditions. The study further benchmarks sensitivity against complementary seismic indicators (Vp/Vs and Poisson’s ratio), supporting a multi-physics strategy for resolving fluid-migration pathways in challenging near-surface settings.

How to cite: Zambrano, M., Arellano, H., Torres, D., Lucci, N., Ughi, A., Arias, A., Ramos, S., and Mateus, Y.: Imaging near-surface geometry of mud volcanoes: a multi-method geophysical study from Monteleone di Fermo (Marche Region, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17807, https://doi.org/10.5194/egusphere-egu26-17807, 2026.

The early Eocene long-term warming was punctuated by relatively short (50 to 200 kyr) and abrupt warming events, which are used as analogues to understand current anthropogenic global warming. Among these hyperthermal events, the Eocene Thermal Maximum 2 (ETM2) corresponds to an orbitally paced release of 2,600 to 3,800 Gt of carbon at 54.1 Ma. It has primarily been identified in deep oceanic settings, while terrestrial and coastal records of this event remain scarce. Indeed, the ETM2 has only been identified in shallow marine settings in a few locations (Arctic, USA Atlantic coast, Egypt, India, and New Zealand), hindering a full understanding of its environmental impact.

Here, we present a high-resolution multi-proxy record from a newly drilled 25-m-long core in southwest Belgium (Mons Basin), at a paleolatitude of ~40°N, combining Gamma-ray spectrometry, mineralogy (XRD bulk-rock and clays, TEM, grain-size) and organic geochemistry (δ¹³C_org, Rock-Eval^®, and palynofacies). Sedimentological interpretation indicates a siliciclastic tidal shallow marine environment (a few tens of meters water depth). Using an age model based on nannofossils, dinocysts and cyclostratigraphy, the ETM2 is recorded over approximately 2.5 m by a ~1‰ negative carbon isotope excursion (CIE) located within the NP11 nannofossil biozone. The peak of this CIE corresponds, with a slight delay, to an increase in carbonate content and nannofossil abundance, suggesting enhanced primary productivity related to an intensified hydrological cycle and higher nutrient inputs during the ETM2. An increase in detrital input is also suggested by the transition to coarser grain size. After a progressive decline in kaolinite, illite, and chlorite contents in the clay fraction, smectite becomes the dominant clay mineral during the CIE, possibly pointing to a transgressive event in relation with the ETM2, as also suggested by palynofacies and dinocyst assemblages.

This study presents the first high-resolution record of the ETM2 in the coastal environments of the southern North Sea Basin, preserved in the Mons Basin. In these settings, the ETM2 is associated with a deepening trend, possibly related to sea-level rise, as well as with increased primary productivity and detrital inputs, which point to an enhanced hydrological cycle.

How to cite: Talon, J., Pellenard, P., Iakovleva, A., Shcherbinina, E., Martinez, M., Quesnel, F., Rusch, C., Dupont, N., Schnyder, J., Baudin, F., Dupuis, C., and Baele, J.-M.: Unravelling the impact of the Eocene Thermal Maximum 2 (ETM2) : A high-resolution shallow marine record from Belgium , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-305, https://doi.org/10.5194/egusphere-egu26-305, 2026.

The response of ice sheets and sea level to a warming climate is of global concern, with significant implications for human populations. To better understand these dynamics, especially during climates warmer than today, this project reconstructs sea-level and ice-sheet variability across six glacial-interglacial (G-IG) cycles of the late Cenozoic (~5 Ma), spanning the transition from the Pliocene greenhouse to the Pleistocene icehouse.

We use paired measurements of benthic foraminiferal δ¹⁸O and Mg/Ca ratios to reconstruct bottom-water temperature (BWT) and derive seawater δ¹⁸O (δ¹⁸O_sw), a proxy for global ice volume. While effective for interglacials, the Mg/Ca proxy likely overestimates glacial lowstands due to non-thermal effects. To improve reconstructions, we integrate carbonate clumped isotope (Δ₄₇) thermometry, a seawater chemistry-independent BWT proxy, using material from Eastern Equatorial Pacific ODP Site 849. Though analytically demanding, Δ₄₇ offers a critical calibration check for Mg/Ca-derived BWTs.

Preliminary paired δ¹⁸O-Mg/Ca data from Oridorsalis umbonatus (3.35–2.0 Ma) at sub-millennial resolution reveal G-IG sea-level cycles with glacial lowstands lower than previous estimates. Δ₄₇-BWTs, available at lower resolution, broadly support the Mg/Ca-based reconstructions, reinforcing their validity despite limited precision and resolution.

Future work will refine the understanding of discrepancies between Mg/Ca- and Δ₄₇-derived BWTs, improving glacial sea-level estimates. This study aims to constrain sea-level variability rates and assess existing reconstructions, offering a more robust understanding of past ice-volume dynamics and informing projections of future sea-level rise.

How to cite: Koniarczyk, L., Friedrich, O., Meckler, N., and Taylor, V.: BENTHICS: Benthic Foraminiferal Temperature-Based High-Resolution Ice-Volume Reconstructions during Cenozoic Snapshots, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1424, https://doi.org/10.5194/egusphere-egu26-1424, 2026.

Reconstructing terrestrial climate conditions in the high Arctic during the Late Miocene (∼11.6–5.3 Ma) is essential for understanding how polar environments respond to warmer-than-present global climates. However, direct land-based climate archives from the Arctic are rare, limiting understanding of terrestrial climate sensitivity under greenhouse-gas concentrations comparable to present and near-future conditions. Here we present a terrestrial proxy record from speleothems collected in a cave in eastern North Greenland (∼80.3°N). Speleothem growth phases indicate repeated intervals of sustained permafrost absence, implying significantly warmer and wetter conditions than today under moderate atmospheric CO₂ forcing and elevated regional sea-surface temperatures. Trace-element variability further suggests episodic glaciation in North Greenland during the Late Miocene, pointing to a highly dynamic cryosphere. Together, these results highlight pronounced terrestrial climate variability in the Arctic under warm background conditions broadly relevant to future climate trajectories. This new archive provides an important benchmark for assessing high-latitude climate sensitivity and feedbacks in a warming world.

How to cite: Moseley, G. E., Koltai, G., Baker, J. L., Wang, J., Stoll, H., Donner, A., Anders (née Friedrich), L., Spötl, C., Smith, M. P., Scholz, D., Cheng, H., Hartland, A., Hejny, C., and Edwards, R. L.: Reconstructing Late Miocene Arctic Climate from North Greenland Speleothems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2851, https://doi.org/10.5194/egusphere-egu26-2851, 2026.

How to cite: Voelker, A. H. L. and Ogretmen, N.: Paleoclimatic conditions during Marine Isotope Stage 31 – a global database for PMIP Interglacials, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3542, https://doi.org/10.5194/egusphere-egu26-3542, 2026.

Australia’s Neogene hydroclimate evolved in response to continental drift and major global climate reorganizations, yet the magnitude and spatial structure of these changes remain poorly constrained. Moreover, the ability of climate models to reproduce Australian hydroclimate variability during deep-time warm periods has rarely been evaluated against geological data. Here, we reconstruct hydroclimate evolution across the Northwest Shelf of Australia over the past 23 million years using a continent-scale compilation of downhole natural gamma radiation (NGR) records and directly compare these reconstructions with climate model simulations.

We integrate NGR measurements from 105 industrial and scientific boreholes into a regionally coherent stratigraphic framework using automated Dynamic Time Warping, with biostratigraphic age control providing temporal calibration. High-resolution (~100 kyr) time-slice reconstructions reveal pronounced spatiotemporal variability in terrigenous input, reflecting changes in precipitation and continental runoff.

The reconstructions indicate persistently humid conditions during the Early Miocene, followed by an abrupt transition to widespread aridity at ~18-17 Ma. This major hydroclimate shift is not reflected in HadCM3 simulations, which instead suggest wetter conditions than those inferred from the NGR reconstruction across subtropical Australia during this interval. A subsequent increase in hydroclimate variability at ~6.5 Ma, marked by elevated NGR values, aligns with enhanced modeled precipitation and is consistent with an intensified Leeuwin Current and southward migration of the Intertropical Convergence Zone, pointing to a transient return to wetter conditions. Lower NGR values during the Late Pliocene indicate the onset of a transitional phase preceding the establishment of fully arid conditions by ~2.4 Ma.

Together, these results demonstrate that the magnitude and spatial complexity of Neogene Australian hydroclimate variability inferred from geological records exceed those predicted by state-of-the-art climate models. The pronounced data-model mismatch in the Early and Middle Miocene highlights persistent challenges in simulating regional hydroclimate responses in warmer-than-present greenhouse climates. These findings underscore the importance of geological benchmarks for evaluating model performance and improving projections of future hydroclimate change.

How to cite: Samant, R., Farnsworth, A., Bialik, O. M., Back, S., Reuning, L., Gallagher, S., Sarr, A. C., and De Vleeschouwer, D.: Neogene Australian hydroclimate variability exceeds model predictions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4308, https://doi.org/10.5194/egusphere-egu26-4308, 2026.

The Paleocene–Eocene Thermal Maximum (PETM) is among the most extensively studied climatic events in Earth’s history, primarily due to its relevance as an analogue for future climate change. This brief interval (<200kyr) is marked by a pronounced global temperature increase of approximately 4–8°C and widespread environmental disruptions, including ocean acidification, sea-level rise, intensification of the hydrological cycle, ice-sheet retreat, and significant species extinctions. Despite its importance, ichnological analyses—an essential tool for paleoenvironmental interpretation—remain relatively scarce compared to other Earth science studies.

To address this gap, we performed an ichnological analysis across several sections of the Iberian Peninsula: four sites within the Pyrenean Basin (Esplugafreda, Serraduy, Campo, and Zumaia), representing a continental-to-marine transect in a deep-water gulf opening toward the Bay of Biscay, and one deep-sea section along the southern margin of the Iberian Massif, connected to the Tethys Sea (Río Gor). In the south-pyrenean foreland, conforming an elongated restricted basin, the onset of the PETM coincided with the extinction of the tracemaker community. After that, on the platform areas, trace fossil assemblages were re-established prior to the recovery of the carbon isotope excursion, whereas in deep-sea settings, assemblages only partially recovered even after the excursion ended. These findings indicate a prolonged tracemaker recovery period during the PETM, suggesting that deep-sea tracemaker communities experienced extended ecological stress. In the southern margin of the Iberian Massif (i.e., open ocean setting), during the PETM a high trace fossil abundance is recorded.

Finally, by comparing our results with those from other parts of the world (previous published studies and ongoing research), we can hypothesize why the PETM did not cause a global extinction in the macrobenthic tracer community.

How to cite: Miguez Salas, O., Valero, L., Rodríguez-Tovar, F. J., Lopez Blanco, M., Pujalte, V., and Garcés, M.: Ichnology of the Paleocene-Eocene Thermal Maximum , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5445, https://doi.org/10.5194/egusphere-egu26-5445, 2026.

Understanding the pace of past carbon-cycle disruptions is essential for contextualizing today’s rapid warming. The Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma) is commonly invoked as an analogue for anthropogenic change, yet its comparatively protracted onset implies carbon release, warming, and acidification rates substantially slower than those observed today. In contrast, a short-lived 1–2‰ negative carbon isotope excursion immediately preceding the PETM, termed the pre-onset excursion (POE), has been reported from multiple sites, but its timing and duration remain controversial due to limited chronological control. Key questions therefore remain: How rapidly did climate and environmental change unfold during the POE, and can it provide a more appropriate rate analogue for near-future change? Here we analyze two high-sedimentation-rate paleo-shelf cores from the Mid-Atlantic Coastal Plain (Maryland, USA): South Dover Bridge (SDB) and Cambridge Dorchester Airport (Cam-Dor). High-resolution paleoclimate proxy time series from X-ray fluorescence (XRF) scanning are evaluated using spectral and tuning approaches, and astrochronologic robustness is assessed with statistical tests. Dominant stratigraphic cycles at ~10.5 m and ~2.0 m yield ratios consistent with short eccentricity (~100 kyr) and climatic precession (~20 kyr), implying a mean sedimentation rate of ~10 cm/kyr. The resulting astrochronology constrains the total duration of the POE to 6-8 kyr. Independent δ¹¹B constraints indicate that the POE was accompanied by measurable surface-ocean acidification of ~0.1–0.3 pH units. The inferred rate of pH decline during the POE is of the same order as the present, reinforcing the POE as a potential high-rate analogue and highlighting rapid recovery consistent with strong Earth-system buffering prior to full PETM feedback activation.

How to cite: Li, M., Jiang, Q., and Wu, Y.: A modern-like rate of climate change observed in the latest Paleocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6048, https://doi.org/10.5194/egusphere-egu26-6048, 2026.

The late Miocene cooling (LMC; ~7–5.4 Ma) represents a major global climate transition associated with declining atmospheric CO₂, large-scale aridification, and reorganization of terrestrial ecosystems. While cooling at high and mid latitudes during this interval is well documented, temperature changes in the tropical oceans appear muted. Existing tropical sea-surface temperature (SST) reconstructions based on alkenone unsaturation (UK’37​) are limited by proxy saturation at ~29 °C, potentially leading to an underestimation of tropical warmth. Here, we investigate tropical upper-ocean temperature evolution during the late Miocene using coccolith clumped isotope (∆47) thermometry, which reflects habitat-depth temperatures rather than regressed SSTs.

We present new coccolith ∆47 temperature records from ODP Site 926 (Ceara Rise) spanning the late Miocene and compare them to late Pleistocene glacial and interglacial intervals from nearby ODP Site 925. Coccolith-enriched sediment fractions were carefully isolated and screened prior to ∆47 analysis. Results indicate muted tropical cooling of ~3 °C during the LMC, consistent with global temperature compilations. Notably, reconstructed late Miocene upper-ocean temperatures (~20–25 °C) are similar to those observed during Pleistocene interglacials, despite fundamentally different climate states characterized by Antarctic-only glaciation in the late Miocene and bihemispheric glaciation in the Pleistocene.

These findings suggest that muted tropical cooling during the late Miocene is not solely an artefact of alkenone saturation.

This study underlines the potential of coccolith clumped isotopes to provide constraints on upper-ocean temperatures, avoiding uncertainties associated with regressing proxy signals to SST. However, changes in coccolithophore depth habitat and water-column stratification remain key uncertainties. Ongoing paired coccolith–foraminifera ∆47 and foraminifera δ¹⁸O analyses will improve interpretations of tropical ocean temperatures and vertical gradients across contrasting climate states.

How to cite: Leusch, M., Jaggi, M., Bernasconi, S., and Stoll, H.: Similar Tropical Upper-Ocean Temperatures in the Late Miocene and Pleistocene Interglacials, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7307, https://doi.org/10.5194/egusphere-egu26-7307, 2026.

The Plio–Pleistocene transition represents the shift from a warmer Pliocene to a cooler Pleistocene, offering key insights into climate sensitivity to CO₂ forcing and ice-volume changes. However, the upper-ocean thermal response of the Pacific mid-latitudes and upwelling regions remains poorly constrained, despite their critical role in global climate and ocean circulation. Here, we present paired U^K′₃₇–TEX₈₆ upper-ocean temperature records spanning 3.4–2.4 Ma from the subtropical and equatorial Pacific at ODP Site 1012 (California Margin), IODP Site U1338 (Eastern Equatorial Pacific, EEP), and DSDP Site 593 (Tasman Sea). Surface sediment data in these regions indicate that U^K′₃₇ reflects annual mean sea surface temperatures. In contrast, high GDGT [2/3] ratios (>7) observed in surface sediments and downcore records suggest that TEX₈₆ records shallow subsurface temperatures, likely near the nitrite maximum, as inferred from matching TEX₈₆ temperatures to climatological annual mean temperature profiles, regardless of the calibration used. In upwelling regions, this depth correlates strongly with thermocline depth, indicating deeper (shallower) TEX₈₆ recording depths during weakened (intensified) upwelling. Downcore U^K′₃₇ SST records from both subtropical sites indicate warmer-than-present Pliocene conditions, ~5 ºC cooling during the M2 glaciation, warming at KM5c, and a long-term cooling after the Mid-Pliocene Warm Period (MPWP), whereas SSTs at the equatorial Pacific site show no significant Pliocene–Pleistocene cooling trend. However, TEX₈₆-derived subsurface temperatures exhibit significant Pliocene-Pleistocene cooling across all three regions. Based on the U^K′₃₇–TEX₈₆ temperature difference (ΔT), we infer weaker upwelling along the California Margin during the MPWP, possibly linked to an intensified North American Monsoon (NAM) that weakened upwelling-favorable winds, followed by stronger upwelling under a weakened NAM during the early Pleistocene. In contrast, there is no change in upwelling in the EEP from the Pliocene to the Pleistocene. In the Tasman Sea, U^K′₃₇ likely records northward-sourced surface waters transported by the East Australian Current, whereas TEX₈₆ reflects subsurface South Antarctic Mode Water (SAMW). The convergence of U^K′₃₇ and TEX₈₆ temperatures between 3.1 and 2.6 Ma likely indicates northward migration of the Subtropical Front, allowing SAMW to shoal and influence surface conditions at the site. Overall, during the Plio–Pleistocene transition, the mid-latitude Pacific experienced an expansion of cold high-latitude waters. This study highlights the usefulness of paired U^K′₃₇–TEX₈₆ analyses in advancing our understanding of upper-ocean thermal evolution across diverse Pacific hydrological settings during past key climate transitions.

How to cite: Azharuddin, S., Ho, S. L., Hefter, J., McClymont, E., and Groeneveld, J.: Upper-ocean temperature and upwelling variability across the Pacific during the Plio–Pleistocene transition: Insights from UK′37 and TEX86, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8860, https://doi.org/10.5194/egusphere-egu26-8860, 2026.

The late Miocene and Pliocene were periods characterized by warmer-than-present climatic conditions and are therefore commonly used to investigate the possible effects of ongoing global warming. The Atlantic meridional overturning circulation (AMOC) is a crucial component of the climate system, since it involves oceanic currents and controls the redistribution of heat around the globe. Specifically, warm and saline water from the low-latitudes reaches the high-latitude North Atlantic, where it loses heat and sinks to form deep-water masses. This sinking generates strong bottom currents, which flow southwards, powering what is known as the global ocean conveyor belt. Understanding the generation and evolution of these water masses during past warm periods provides valuable insights into their potential response to ongoing increases in ocean temperatures. Recently, International Ocean Discovery Program (IODP) expeditions 395 and 395C made such investigations possible by recovering deep sea sedimentary sequences spanning the late Miocene and Pliocene in the high latitude North Atlantic region (60°N; Parnell-Turner et al., 2025). In this study, we investigate sediment samples from IODP Site U1562 (60°06.3006′N, 26°30.1044′W; ~2003m water depth), located at the edge of a sediment body deposited under the influence of deep-water currents (Björn Drift). This site exhibits continuous sedimentation and excellent microfossil preservation during the latest Miocene to Pliocene (~6.5–3.6 Ma). For our investigation, we use a combination of micropaleontological and geochemical proxies, including X-Ray fluorescence (XRF) core scanning, isotopic analysis of foraminiferal shells, and microfossil species identification and morphometrics. Combining these proxies allows for reconstructing the evolution of temperature, primary productivity, and ocean circulation in the region. Pronounced cyclic variations in calcium carbonate (CaCO₃) preservation indicate a highly dynamic depositional environment, likely controlled by changes in export production and bottom ocean dissolution related to deep-sea currents. These cycles are accompanied by distinct isotopic signatures, with intervals of high CaCO₃ content broadly corresponding to lighter δ¹⁸O values, and vice versa. The occurrence of planktonic foraminifera Orbulina universa, as well as calcareous nannofossils belonging to the genus Discoaster reveal periodically warmer conditions, driven by an overall increase in upper-ocean temperature or enhanced influence of warm currents associated with stronger AMOC. Further analyses will aim to better characterize these cyclic changes, link them to orbital cycles, and combine them with other sedimentological observations to reconstruct the evolution of AMOC during past warm intervals of the late Neogene.

References

Parnell-Turner, R.E., Briais, A., LeVay, L.J., and the Expedition 395 Scientists, 2025. Reykjanes Mantle Convection and Climate. Proceedings of the International Ocean Discovery Program, 395: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.395.2025

How to cite: Karatsolis, B. T., Pearson, P. N., Dunkley Jones, T., Suzuki, T., Müller, I. A., Sinnesael, M., Le Tuyet, N. P., Treand, C., Henderiks, J., Asanbe, J. D., Wade, B., and Claeys, P. and the Expedition 395 scientists: Micropaleontological and geochemical evidence for late Miocene to Pliocene warming in the high-latitude North Atlantic (IODP Site U1562)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10100, https://doi.org/10.5194/egusphere-egu26-10100, 2026.

Carbonate clumped isotope thermometry is a powerful tool increasingly utilized across earth science disciplines. This proxy measures the thermodynamically controlled bonding of heavy rare isotopes ¹³C and ¹⁸O within the same CO₂ molecule (mass 47) derived from carbonate acid digestion. Unlike the widely used Mg/Ca thermometer, △47 thermometry is independent of seawater chemistry changes, including past pH, dissolved inorganic carbon, and carbonate saturation states, although it typically requires larger sample sizes and yields lower precision.

Here, we report on the establishment of a small-sample carbonate △47 measurement method using a Thermo Fisher Kiel IV coupled to a MAT253Plus mass spectrometer at the State Key Laboratory of Marine Geology, Tongji University. Using an aliquot mass of ~120 μg, we achieved a reproducibility for the IAEA-603 standard (n = 35) of 0.04‰ in △47, 0.02‰ in ¹³C, and 0.05‰ in ¹⁸O (1 SD). We applied this method to planktonic foraminifera G. sacculifer from ODP Site 762 in the eastern Indian Ocean. The measured △47 values were 0.666‰ (n = 17, 1 SE = 0.009‰) for the 5.95 Ma interval and 0.673‰ (n = 35, 1 SE = 0.005‰) for the 3.95 Ma interval. Using the recalculated Kele et al. (2015) calibration (Bernasconi et al., 2018), we reconstructed SSTs of 26.8±6.0°C at 5.95 Ma and 24.7±3.4°C at 3.95 Ma. For comparison, temperatures reconstructed using Mg/Ca analysis were 25.9°C at 5.95 Ma and 23.5°C at 3.95 Ma, based on the calibration by Anand et al. (2003). The results demonstrate strong consistency between the two proxies, validating the utility of △47 for paleotemperature reconstruction even when temperature variations are subtle.

Keywords: Clumped isotope (△47), Mg/Ca thermometry, Temperature reconstruction, Foraminifera

How to cite: Ding, Y. and Tian, J.: Reconstructing Late Miocene and Early Pliocene Sea Surface Temperatures: A Comparison of △47 and Mg/Ca Thermometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11064, https://doi.org/10.5194/egusphere-egu26-11064, 2026.

Geological archives from past warm periods are essential for contextualising future climate change under ongoing global warming. However, interpreting these archives requires a robust understanding of how palaeotemperature proxies record oceanographic variability under modern boundary conditions. This study presents ongoing Holocene alkenone-based sea surface temperature (SST) reconstructions from marine sediment cores collected around Denmark. The primary aim is to constrain alkenone signal provenance through comparison with instrumental SST datasets, and to apply this understanding to reconstructions of Gulfstream variability during past warm climates.

The Danish coastal seas, including the Skagerrak–Kattegat region and shelf settings along the Jutland Peninsula, occupy a climatically sensitive position at the interface between warm Atlantic waters transported by the North Atlantic Current and waters derived from the Nordic Seas, Baltic outflow, and terrestrial runoff. Variability in this Atlantic inflow has been linked to changes in North Atlantic heat transport and proposed as a sensitive indicator of broader AMOC-related variability. As such, the Danish marine realm offers a strategic location for assessing how surface ocean temperatures respond to circulation changes under differing climate states.

We use Holocene-age sediment cores to reconstruct SSTs using alkenone palaeothermometry, a biomarker-based proxy derived from marine haptophyte algae that records upper-ocean temperature conditions. Comparison of Holocene alkenone-derived SSTs with instrumental datasets provides a framework for assessing how proxy temperatures relate to observed surface ocean variability, including the influence of regional circulation changes, stratification, and potential freshwater input. This is of particular importance when examining alkenones, as these compounds may be transported by ocean currents, potentially biasing the recorded temperature signal if such effects are not accounted for. In addition to constraining proxy behaviour, the Holocene record is used to explore the expression of Holocene climate variability in the Danish coastal seas and its relationship to other North Atlantic records.

This Holocene–instrumental framework directly supports ongoing research investigating Gulfstream variability during the Eemian Interglacial (MIS 5e, or the Last Interglacial), a past warm period when the average global temperature was approximately 1–1.5 °C higher than present. Exceptionally thick Eemian marine clay sequences from the Vendsyssel region of Denmark are currently being analysed to develop high-resolution alkenone-based SST records capable of resolving multidecadal variability under warm-climate boundary conditions. Anchoring these reconstructions in a modern, provenance-sensitive analogue improves confidence in interpretations of Gulfstream behaviour during past warm periods and enhances the use of geological archives to inform expectations of future oceanographic change.

How to cite: Walker-Trivett, C., Kiel, E.-C., Śliwińska, K., and Snowman Andresen, C.: Gulfstream Variability in a Globally Warming World – The Forgotten Danish Archive, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11918, https://doi.org/10.5194/egusphere-egu26-11918, 2026.

The Indonesian Throughflow (ITF) is a key component of the Indo-Pacific Warm Pool (IPWP) and global ocean circulation, regulating the transfer of heat and freshwater from the Pacific to the Indian Ocean. Here we reconstruct surface and thermocline hydrographic variability of the ITF over the past 150 kyr using paired δ¹⁸O and Mg/Ca records from Globigerinoides ruber, Pulleniatina obliquiloculata, and Neogloboquadrina dutertrei in sediment core MD10-3334 (0.22°N, 119.30°E; 1169 m water depth) from the northern Makassar Strait. The records reveal pronounced glacial–interglacial variability in upper-ocean thermal structure and ITF dynamics. During the last two deglaciations (~27 and ~144 ka), upper thermocline warming preceded sea-surface warming resulting in a smaller vertical temperature gradient (i.e., deepening of the thermocline), which suggests an increase in La Niña–like mean state conditions associated with enhanced heat accumulation in the IPWP and intensified subsurface ITF transport. In contrast, the mid-Holocene and early Marine Isotope Stage (MIS) 5e are characterized by a progressive cooling of thermocline temperatures (increasing vertical temperature gradients), suggesting a reduced subsurface heat transport, consistent with a weakened ITF. These changes likely reflect adjustments in zonal and/or monsoonal wind-driven circulation and upper-ocean stratification linked to orbital-scale shifts in ITCZ position, sea level, and seasonal insolation. Our results suggest changes in the vertical temperature gradients in the Makassar Strait that we interpret as a measure of ITF strength and highlight the critical role of subsurface processes in modulating tropical Indo-Pacific climate variability across glacial–interglacial timescales.

How to cite: Agusta, V. C., Elliot, M., Bassinot, F., Lo, L., Rivoal, M., Richard, P., Manssouri, F., Govin, A., and Kissel, C.: Changes in the surface and subsurface temperature across Glacial-Interglacial transitions in the Indonesian Throughflow over the past 150-kyr: A perspective from the northern Makassar Strait, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12158, https://doi.org/10.5194/egusphere-egu26-12158, 2026.

The Eocene experienced pronounced temporal changes in temperature and atmospheric pCO₂, with multiple warming phases from the early to late middle Eocene. High-resolution, sub-annual palaeoclimate reconstructions are essential to evaluate the impact of elevated pCO₂ on seasonal climate dynamics, providing critical insights for mitigating future climate crises. Middle Eocene Climatic Optimum (MECO), the Lutetian–Bartonian boundary warming event (~41 Ma) is particularly relevant, as current pCO₂ levels are rising rapidly and could reach similar concentrations within a century.

Bivalvia shells, growing incrementally, record seasonal to even sub-daily climatic and environmental fluctuations throughout their life. Shells of the oyster Cubitostrea cubitus, a shallow-to-marginal marine cementing bivalve from the Sables du Guépelle Formation (~41 Ma) of the Paris Basin (~41° N palaeolatitude), contain very low Mn and Fe concentrations (<250 µg/g), indicating their pristinity. These shells are used as a palaeoclimate archive in a multiproxy approach that combines LA-ICP-MS trace element analyses and clumped isotope thermometry (Δ₄₇), integrated with simulations from the Community Earth System Model (CESM). Sub-annual periodic variations in trace elements to Ca ratios along the oyster hinge indicate an oyster lifespan of ~16 months when aligned with monthly temperature variability from CESM simulations. Clumped isotope thermometry (Δ₄₇-T) records a seasonal sea surface temperature (SST) amplitude of ~8 °C, where the summer temperature reaching 28.3 ± 4.4 °C (68% CI) and winter temperatures of  19.6± 3.5 °C. Summer δ¹⁸O_w (-1.1± 0.9  ‰), consistent with Bartonian seawater compositions (-0.5 to -1.0 ‰), indicate a strong seasonal marine influence in early Bartonian Paris Basin. In contrast, significantly lower winter δ¹⁸O_w values (-2.9± 0.7 ‰) reflect enhanced freshwater input, which is further supported by relatively lower Sr/Ca profile, a salinity indicator consistent with increased winter rainfall predicted by CESM simulations.

In summary, our preliminary results indicate that during the MECO, the Paris Basin experienced seasonal sea-surface temperature variability comparable to that of modern shallow waters along the French North Sea coast, but with higher temperatures of approximately 10 °C throughout the year. In contrast to the modern climate (in the region of : 0–5° E, 46–50° N), where annual precipitation is relatively evenly distributed, rainfall during the MECO appears to have been strongly seasonal.

How to cite: Mitra, A., Goderis, S., Baatsen, M., Zhao, X., Chaudhuri, S., Ledésert, B. A., Claeys, P., and Müller, I. A.: Oyster shells record seasonal climate variability in the middle Eocene Paris Basin under higher-than-modern temperatures and seasonal rainfall patterns, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12459, https://doi.org/10.5194/egusphere-egu26-12459, 2026.

Large uncertainty surrounds efforts to model the regional response to CO₂-driven warming in the southwestern U.S. The region hosts a seasonally variable hydroclimate and significant topography – much of which is tied to the region’s complex Cenozoic geologic history. These intricacies are difficult to reconcile in models, leading to disagreement even on the modelled sign of future precipitation change in the southwestern U.S. Previous and new stable isotope analyses of pedogenic carbonates from the well-dated Santa Fe Group of New Mexico suggest a potential shift from a middle Miocene winter-wet climate towards the dual-wet season regime seen in the region today, where annual precipitation is relatively low but delivered in both the summer and winter. This shift in regime might be spurred by either a strengthening of the North American Monsoon or a weakening of the westerlies. New clumped isotope analysis of these pedogenic carbonates documents a long-term cooling of as great as 18.5 ± 10.3°C between the Miocene Climatic Optimum (MCO) and the Pleistocene. This Neogene cooling trend in New Mexico tightly tracks the global benthic δ¹⁸O record over the same period, as well as Pacific sea-surface temperature records. This correlation suggests that paleotemperature change throughout the record is controlled by global climate rather than a potential shift in carbonate formation season driven by a shift in the precipitation regime. However, climate models, including both modern ocean-equilibrated LongRunMIP and Middle Miocene simulations, are unable to match the degree of continental MCO warmth in New Mexico indicated in our data even at CO₂ concentrations 8x higher than pre-industrial levels. Illustrating the magnitude of disagreement, Miocene and modern simulations respectively predict 4.6°C and 3.2°C of warming in New Mexico under a 560-ppm climate while the clumped isotope temperatures at the MCO are roughly 10°C warmer than modern mean annual temperatures in New Mexico. The disagreement between the magnitude of MCO warmth indicated by our clumped isotope record and that resulting from models can be explained either by (1) an underprediction of modelled temperature responses to CO₂-driven warming in the southwestern U.S. or (2) other factors that modify local temperature, such as changes in elevation associated with ongoing rifting along the Rio Grande rift and/or long-wavelength uplift associated with passage of the Farallon plate beneath the southwestern U.S. Whether the discrepancy in magnitude is an indication of extreme warmth at the MCO in New Mexico or a result of paleotemperatures encapsulating tectonic signals, our record demonstrates that global drivers pace temperature change in the U.S. Southwest.

How to cite: Bernstein, R., Koning, D. J., Maloney, A., Spaur, S., Lee, O., Sanchez Ortiz, G., Methner, K., Mulch, A., Fiebig, J., Ibarra, D. E., Acosta, R. P., Snell, K. E., and Rugenstein, J. K. C.: Neogene U.S. Southwest Temperatures Paced by Global Climate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14189, https://doi.org/10.5194/egusphere-egu26-14189, 2026.

While the Miocene Climate Optimum (MCO) is viewed as an analogue for near-future conditions resulting from anthropogenic climate change, improving our understanding of this event requires the development of proxy records within a well-calibrated temporal framework. Large igneous province emplacement in the Columbia River Basalt Group (CRBG) has been suggested to cause elevated global temperatures and CO₂ during the MCO, but assessing the connection between volcanism and warming requires robust timelines for proxy records of these events. While we have developed a new age model for CRBG volcanism based on high-precision U-Pb geochronology (Kasbohm et al., 2023) and a U-Pb age model for the MCO that reinforces the validity of astronomically tuned age models for this event (Kasbohm et al., 2024), only a small number of MCO proxy records have been age-calibrated through astronomical tuning. Existing boron isotope CO₂ proxy records from the MCO were age-calibrated through biostratigraphy alone, hindering correlation to known intervals of CRBG volcanism. These records showed high-amplitude CO₂ variability, calling into question the stability of the Miocene climate system.

Here, we present a new foraminiferal boron isotope record from International Ocean Discovery Program Site U1490 (Western Pacific Warm Pool), which has an astronomically tuned age model concordant with our radiometric ages for the MCO (Holbourn et al., 2024). This new record targets the onset of the MCO through the end of the main-phase CRBG volcanism (17.1-16 Ma) at ~15 kyr resolution, with lower resolution across the entire MCO (17.8-13 Ma). We find well-resolved and relatively stable pH values across the MCO, with sampling resolution that reveals orbital pacing of these records. Our reconstructed CO₂ estimates show less variability than prior records, though we note somewhat variable correlation with changes in MCO benthic δ¹⁸O values, which may reflect dynamism in foraminifera’s habitat during the warmest conditions of the MCO. We observe little change in CO₂ resulting from CRBG surface volcanism, and no strong correlation between CO₂ changes and the tempo of CRBG eruptions. A transient uptick in CO₂ prior to surface eruptions, as well as sustained somewhat higher values afterwards, may be explained by cryptic degassing of large amounts of CRBG magma trapped in the crust, but the magnitude of this CO₂ change was small.

How to cite: Kasbohm, J., Jurikova, H., Holbourn, A., Nana Yobo, L., Wade, B., Ring, S., Planavsky, N., Rae, J., and Hull, P.: Testing the role of large igneous province volcanism in the Miocene Climate Optimum with a new boron isotope record from the Western Pacific Warm Pool, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14704, https://doi.org/10.5194/egusphere-egu26-14704, 2026.

High reconstructed temperatures and pCO₂ concentrations during the Miocene Climatic Optimum (MCO; ~17-15 Ma) make it a possible analog for future warm climates. Proxy sea surface temperature (SST) reconstructions often indicate warm high latitudes, with a relatively small latitudinal temperature gradient. However, Earth system models generally do not yield the relatively flat latitudinal temperature gradients given by proxy reconstructions, and instead have cooler polar regions and somewhat warmer tropics. In tropical regions, this proxy-model disagreement may be due to habitat depths below the surface mixed layer, where the proxy would record temperatures from deeper, cooler waters, whereas the model output is simply SST. At high latitudes, however, the proxy-model disagreement cannot be fully explained by habitat depth or seasonal temperature, leaving two possibilities: one, that the models do not fully capture the Earth System; or two, that proxies are impacted by widespread non-thermal effects.

In an attempt to elucidate matters, we investigated clumped isotopes in coccoliths (cocco-Δ₄₇) at Southern Ocean sites 1168 (South Tasman Sea) and 751 (Kerguelen Plateau) and compare these results to previously published biomarker-based temperature proxies (U^K’₃₇ and TEX₈₆) at Site 1168. Clumped isotope samples were screened for good preservation, and contain little or no diagenetic carbonate. Unlike most temperature proxies, cocco-Δ₄₇ values are independent of seawater chemistry and do not exhibit species- or strain-specific offsets, instead yielding an absolute growth temperature. Additionally, coccoliths and alkenones are derived from the same organisms, and should be directly comparable. During peak warmth (~16.5 Ma), cocco-Δ₄₇ values yield temperatures of 12.0 ± 2.8 and 7.3 ± 2.8 °C at Sites 1168 and 751, respectively, and agree well with latitudinal averages of climate model output. At Site 1168, previously published U^K’₃₇ and TEX₈₆ yield much higher temperatures (27 °C SST and 21 °C 0-200 m temperatures, respectively; Guitián and Stoll P&P, 2021; Hou et al. Clim. Past, 2023). The difference in proxy temperature estimates is large and cannot be reconciled with modern ranges in seasonal SST or photic zone habitat depth temperature. Mixing effects and physiological influences will be further explored.

How to cite: Rice, A., Bernasconi, S. M., Jaggi, M., and Stoll, H. M.: Exploring proxy-proxy and proxy-model (dis)agreements during the leadup to the Miocene Climatic Optimum in the Southern Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17248, https://doi.org/10.5194/egusphere-egu26-17248, 2026.

Global cooling during the Eocene-Oligocene Transition (EOT; 33.9 Ma) drove pronounced environmental and biotic shifts across the globe. However, the paleo-climatic response on the North American continent remains debated, especially in the high-elevation Cordillera, which may have been cold and dry already before the EOT. To test the response of this high-elevation terrain to global climate forcing, we studied three sedimentary sections in SW Montana (Easter Lily, Black Butte and Lion Mountain) that span the Eocene-Oligocene boundary and contain calcretes for paleo-environmental reconstructions. Dual clumped isotope thermometry in the Easter Lily section shows cooling of ~2°C during the earliest Oligocene followed by warming to pre-EOT temperatures. This indicates that EOT cooling was only transient and that long-term temperatures during the early Oligocene were similar to the late Eocene. In addition, calcrete oxygen (δ¹⁸O) and carbon (δ¹³C) isotope ratios within the three sections do not record major changes across the EOT. Instead, large differences are observed among the studied sections in δ¹⁸O values (up to 2‰) and especially in δ¹³C values (up to 6‰). This suggests strong heterogeneity of the intermontane paleo-environments in SW Montana, with individual basins recording different temperatures and degrees of aridity. Such a topographically and climatologically complex landscape may have produced the diverse endemic mammal fauna observed in these fossil localities.

How to cite: Meijer, N., Seymour, N., Methner, K., Fiebig, J., and Mulch, A.: Calcrete clumped and stable isotopes reveal transient cooling and heterogeneous Eocene-Oligocene paleo-environments in SW Montana, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18001, https://doi.org/10.5194/egusphere-egu26-18001, 2026.

Earth’s climate and ocean circulation have reorganized profoundly since the late Miocene. Global compilations of sea surface temperature reconstructions indicate cooling trends during the late Miocene and the Pliocene-Pleistocene periods. However, there is no long-term high-resolution temperature record from the northwestern Pacific yet. Here we present a new, extremely high-resolution (1-3 kyr), continuous alkenone sea surface temperature record spanning the past 10 million years from the subarctic front region of the northwestern Pacific. On glacial-interglacial timescale, SST variance and dominant frequencies changed stepwise, defining three phases: strong-amplitude variability (~5–9°C) at 0–1.7 Ma, moderate variability (~2–5°C) at 1.7–5.6 Ma, and weak variability (~1–2°C) at 5.6–9 Ma. Band-pass filtering isolates 405, 100, 41 and 21/19 kyr components, revealing pervasive orbital pacing and reproducing the three-phase structure. On long-term timescale, our results exhibit multistage process of the North Pacific cooling with related climate changes during the time period. In particular, the late Miocene (5-7 Ma) cooling can be compared with that of the late Pliocene-Pleistocene periods (1-3 Ma). Further comparisons between our temperature record at the subarctic front region with those from the western and eastern equatorial Pacific have been conducted, anticipating being able to reconstruct the evolution/variability of the subarctic front and its relationship with the evolution of the North Pacific subtropical gyre during the northern hemisphere glaciation.

How to cite: Lee, K. E. and Ko, T. W.: Multistage process of North Pacific cooling during the past 10 million years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18266, https://doi.org/10.5194/egusphere-egu26-18266, 2026.

The trend of hydroclimatic variability represents a major area of concern in the context of global warming. The Pliocene–Pleistocene Transition (PPT) provides a valuable geological analogue, characterized by a dramatic shift in global ice volume and temperature. Here we present a pollen-based quantitative summer precipitation record spanning 3.4–2.4 Ma, derived from a fluvio-lacustrine sequence from the Datong Basin in the mid-latitude East Asia. Pollen data were converted to precipitation estimates using a pollen-derived Weighted Averaging Partial Least Squares (WA-PLS) model. Our results show that the summer precipitation remained broadly stable across the PPT, with no clear long-term trend. Instead, pronounced changes occur in precipitation variability. Before ~2.9 Ma, the late Pliocene hydroclimate showed large-amplitude fluctuations, with more frequent wet and dry extremes. After 2.9 Ma, variability decreases, and extreme values became less frequent, indicating a transition to a more stable rainfall regime. Spectral analyses further support this regime shift in the frequency domain: while ~100-kyr eccentricity-scale variability dominated the late Pliocene hydroclimate, it weakened and became less coherent following 2.9 Ma. Under future warming scenarios, these results imply that changes in hydroclimatic variability may represent a critical source of risk to mid-latitude Asian climate systems.

How to cite: Ge, J., Long, H., Cheng, L., Wang, H., and Seppä, H.: Reduced precipitation variability over mid–latitude East Asia during the Pliocene-Pleistocene Transition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18622, https://doi.org/10.5194/egusphere-egu26-18622, 2026.

Past greenhouse climates like the Early Eocene Climatic Optimum (~53-49 million years ago, Ma) provide an opportunity to assess the sensitivity of global temperature to greenhouse forcing, with proxy-based temperature reconstructions from such time intervals providing crucial benchmark data for evaluating Earth System Models. However, estimating global mean temperatures is complicated by sparse proxy evidence for surface temperatures and heterogenous warming patterns. For this reason, most depictions of global mean temperature evolution use temperature reconstructions from the deep ocean, a vast and (proposedly) relatively homogenous heat reservoir (e.g., Hansen et al., 2013; Westerhold et al., 2020). Deep ocean temperature reconstructions, however, are usually based on the oxygen isotopic composition (δ¹⁸O) of benthic foraminifera, which can additionally be influenced by the isotopic composition of seawater and other non-thermal factors.

Here we present new deep ocean temperature reconstructions for ~52–50 Ma from both the North Atlantic (IODP Site U1409) and the Pacific Ocean (ODP Site 1209) using clumped isotope thermometry, which is independent from seawater composition and less affected by non-thermal influences. We confirm previously reported deep North Atlantic temperatures exceeding δ¹⁸O-based estimates (Meckler et al., 2022). Crucially, our results show that deep ocean warmth is not a regional feature of the Atlantic Ocean, with similarly warm temperatures also found in the vast deep Pacific Ocean. The new data advocate for a revision of previous, δ¹⁸O-based estimates of global mean temperatures. Combined with new CO₂ estimates, we derive an updated and more robust estimate of equilibrium climate sensitivity for the Early Eocene Climate Optimum, which is higher than most previous estimates, an important new constraint for Earth System Models.

References

Meckler, A.N., et al. (2022), Cenozoic evolution of deep ocean temperature from clumped isotope thermometry. Science 377, 86-90

Hansen, J., et al. (2013), Climate sensitivity, sea level and atmospheric carbon dioxide. Philos. Trans. A Math. Phys. Eng. Sci. 371, 20120294

Westerhold, T., et al. (2020), An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science 369, 1383–1387

How to cite: Meckler, N., Taylor, V., Marquardt, J., Lypiridou, I., Ring, S., Rae, J., Sexton, P., Westerhold, T., Zachos, J., and Kirtland-Turner, S.: Globally warm deep ocean during the Early Eocene Climatic Optimum indicates high climate sensitivity to greenhouse gases, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19376, https://doi.org/10.5194/egusphere-egu26-19376, 2026.

The response of the climate system to rapid carbon-cycle perturbations can be constrained by studying past transient climate events such as the Paleocene–Eocene Thermal Maximum (PETM, ~56 million years ago). The PETM is marked by a massive input of isotopically light carbon, as recorded by a 3–4‰  negative carbon isotope excursion (CIE) in sedimentary records globally. Estimates of the duration of the rapid onset of the CIE range from a few hundred to several thousand years. The exact duration remains poorly constrained due to the scarcity of marine sedimentary records that 1) have sufficiently high sedimentation rates to resolve rapid decadal- to centennial scale transitions, 2) provide robust controls on sedimentation rates and event timing, and 3) preserve proxy data that record perturbations of the dissolved inorganic carbon (DIC) pool. Consequently, the rate of carbon release during the CIE onset, and its relevance for understanding anthropogenic climate change, remains unclear.

International Ocean Discovery Program (IODP) Expedition 396 recovered expanded PETM successions on the Norwegian Margin, including a microlaminated CIE onset interval that preserves decadal-scale variability. We document the first occurrence of haptophyte alkenones from the onset of the PETM CIE and present a high-resolution record of their stable carbon isotopic variability (δ¹³C_alk) across the onset interval. The δ¹³C_alk records variations in the (isotopic) composition and concentration of the dissolved inorganic carbon (DIC) pool. We show that the δ¹³C_alk record is not strongly influenced by local (volcanically induced) input of ¹³C-depleted carbon based on high-resolution sedimentary mercury and polyaromatic hydrocarbon data from this interval. Finally, we provide robust age control from the diatom laminations, enabling a direct and well-constrained estimate of the duration of the global CIE onset interval.

How to cite: Nelissen, M., Bats, Y., Furlong, H., Verkooijen, S., Frieling, J., Jones, M., Mather, T., Scherer, R., van der Meer, M., Schouten, S., Peterse, F., Sluijs, A., and Brinkhuis, H.: New constraints on the duration of the onset of the PETM carbon isotope excursion, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20142, https://doi.org/10.5194/egusphere-egu26-20142, 2026.

Paleoproxy records of bottom water temperature (BWT) have been used to investigate past reconfigurations of ocean circulation, infer changes in global ice volume following deconvolution of benthic oxygen isotopes, and extract information about average surface climate in warm, equilibrated states. Despite the wealth of BWT data available for the past 5 Myrs, persisting uncertanties in the proxy systems and methods most widely used to derive BWT have led to different, at times conflicting, views of climate and sea level variability across key Plio-Pleistocene transitions. Here we present ongoing work to better constrain the long-term evolution of Plio-Pleistocene BWTs using clumped isotopes from benthic foraminifera, bypassing well-known pitfalls affecting other temperature indicators and opening new avenues of leverage in multiproxy comparisons. Our results question previous definitions of the relationship between mean ocean BWTs and global ice volume, with puzzling implications  for the so-called intensification of Northern Hemisphere glaciations after the mid-Piazencian Warm Period and the expected influence of ice-sheets on global climate. Moreover, these new records support the use of mean ocean BWT as a reflection of average surface climate beyond the Miocene, thereby showing great potential to inform the development of new paleo-informed climate models.

How to cite: Domínguez Valdés, E., Kocken, I. K., Agterhuis, T., Müller, I. A., van der Kloos, R. M., Hendriks, P., Bode, N. J., Lourens, L. J., and Ziegler, M.: More Ice in Warmer Worlds? Reassessing Plio-Pleistocene Climate Relationships, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20224, https://doi.org/10.5194/egusphere-egu26-20224, 2026.

The short-lived (~30 Kyr) warming C19r event or Late Lutetian Thermal Maximum (LLTM) is the hyperthermal recorded 41.52 Ma ago in the upper part of
magnetochron C19r. Like most Eocene hyperthermals, this event has been defined by a sharp negative excursion in the oxygen and carbon isotopic records in the Atlantic Ocean, including ODP Sites 1260, 1263 and 702 and in a land section in Spain. To understand how marine biota responded to past warming is crucial also for a future climatic perspective. However, differently from the early Eocene hyperthermals for which biotic response has been widely analyzed, the LLTM has been so far explored only for the benthic foraminiferal response. Planktic foraminifera, that are extremely sensitive to ocean changes, have a key role to evaluate how global warming affects marine ecosystems. We present here the impact on planktic foraminiferal communities to this event, at the south Atlantic Site 1263. Although the LLTM records a moderate temperature increase with respect to other Eocene warming events, planktic foraminiferal assemblages reveal to be extreme sensitive as showing marked variations that include a decline in abundance of the cold-index Subbotina and a not straightforward response of the mixed-layer warm-index taxa, suggesting possible ecological competition and different flexibility to challenge the new environmental conditions.

How to cite: Ferrando, F., Sigismondi, S., Westerhold, T., and Luciani, V.: Impact of the Late Lutetian Thermal Maximum (41.52 Ma) on plankticforaminiferal assemblages (Site 1263, Atlantic Ocean), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20368, https://doi.org/10.5194/egusphere-egu26-20368, 2026.

The dissolution of calcium carbonate (CaCO₃) is a key regulator of long-term changes in oceanic CO₂ uptake, through the generation of alkalinity. Geological records from past climatic and carbon-cycle perturbation events contain abundant evidence for ocean acidification and seafloor CaCO₃ dissolution. Such events can thus serve as natural laboratories to assess the role of carbonate compensation in mitigating extreme carbon release and stabilizing the Earth system. In this study, we aim to evaluate the magnitude, rate, and climatic significance of carbonate dissolution for the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), the most dramatic of the early Cenozoic hyperthermals. Specifically, we use a new high-resolution record from IODP Site U1514 from the Mentelle Basin in the SE Indian Ocean (paleolatitude: ∼60°S at 50 Ma) to quantify the dissolution of seafloor CaCO₃ deposited prior to the PETM (‘burndown’), in the earliest phases of the event.  Our site is ideally positioned to document this process due to its location in the deep-sea, relatively high sedimentation rates, expanded upper Paleocene record and sensitivity to changes in carbonate saturation. We use precession-scale cyclostratigraphy to create an age model for the late Paleocene and early Eocene at U1514, anchored within 405-kyr astrochronozones and subsequently tied to the established astrochronology of ODP Site 690 in the Weddell Sea, allowing for refined interbasinal stratigraphic alignment across the Southern Ocean. The age model forms the basis for our analysis of ‘burndown’ dissolution and alkalinity generation at our site and across the PETM seafloor. Our work is an important step forward in our ability to quantify alkalinity fluxes from seafloor dissolution and their impact relative to terrestrial weathering, on millenial to orbital timescales.

How to cite: Papadomanolaki, N. M., Jones, H. L., Hanson, E. M., Edgar, K. M., Bialik, O. M., Batenburg, S. J., and De Vleeschouwer, D.: Quantifying PETM Carbonate Burndown and Alkalinity Feedbacks through Cyclostratigraphy , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2001, https://doi.org/10.5194/egusphere-egu26-2001, 2026.

Reconstructing carbon release fluxes during extreme climatic events in Earth history—particularly quantifying the magnitude and climatic impacts of biogenic greenhouse-gas emissions—is crucial for building high-confidence “past–future” climate analog frameworks. In paleoclimate research, the Toarcian Oceanic Anoxic Event (T-OAE; ~183 Ma), one of the most prominent global warming episodes of the Mesozoic, still features key knowledge gaps regarding the coupled mechanisms linking its carbon-isotope excursions (CIEs) to greenhouse-gas release. Here we integrate multi-proxy constraints to develop a global coupled biogeochemical model that explicitly represents methane cycling across the sediment–ocean–atmosphere system, and we apply a Markov chain Monte Carlo (MCMC) Bayesian inversion to systematically quantify methane emission fluxes during the T-OAE for the first time. Model simulations indicate that reproducing the pulsed negative CIEs, the rise in atmospheric pCO₂, and the 4–6 °C global warming inferred from paleotemperature proxies requires at least ~4700 Gt (CO₂-equivalent) of sustained biogenic methane input to the Earth’s surface system. Notably, the inferred carbon-isotopic composition of the methane (δ¹³C = −50‰ to −70‰) closely matches the characteristic fractionation associated with methanogenic archaeal metabolisms. The model further suggests that methane release may have amplified methanogenesis and increased organic-matter input, while sulfate-depleted ocean conditions reduced methane oxidation, together establishing a positive feedback of “enhanced methane production–suppressed oxidation efficiency.” Sensitivity experiments show that methane emissions of this magnitude could drive an atmospheric pCH₄ increase of >5 ppm, producing additional radiative forcing sufficient to yield ≥2 °C extra surface warming. Moreover, oceanic methane release promotes a millennial-scale decline in dissolved oxygen, triggering systemic collapse of benthic habitats. This nonlinear coupling between biogeochemical cycling and ecosystem responses may have been a key driver of widespread marine biotic losses during the T-OAE.

How to cite: Qiu, R.: Pulsed biogenic methane emissions and episodic carbon cycle perturbations during the Toarcian Oceanic Anoxic Event, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2050, https://doi.org/10.5194/egusphere-egu26-2050, 2026.

Understanding of different types of El Niño events, notably Eastern Pacific (EP) and Central Pacific (CP) El Niño, is hindered by the limited length of observations. Using climate simulations, we investigated the evolution of El Niño flavor from 250 million years ago (Ma) to present. Results show that El Niño has been persistent throughout the entire period the simulation spans, but was dominated by CP El Niño at 250 Ma - 80 Ma. With the emergence of the Atlantic Ocean, which modulated the state of the Pacific Ocean through atmospheric circulation, EP El Niño became the predominant El Nino state (70 Ma - 10 Ma). After the closure of the Central American Seaway (0 Ma), EP and CP El Niño occurred with similar frequencies. Our findings highlight that El Niño types are controlled by geography over tectonic timescales.

How to cite: Hu, Y., Wu, S., and Liu, Y.: Eastern Pacific El Niño activated by the Atlantic Ocean, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2419, https://doi.org/10.5194/egusphere-egu26-2419, 2026.

Paleoproterozoic cap carbonates provide vital records of post-glacial environmental and biogeochemical transitions, offering crucial insights into early Earth’s climatic, ocean–atmosphere evolution, and the planet’s habitability^[1]. This study reports, for the first time, well-preserved evidence of such cap carbonates from the Aravalli Supergroup, India, identified within calc-silicate horizons embedded in the metavolcanics of the Delwara Formation. Comprehensive geochemical and isotopic analyses confirm their primary depositional signatures and effectively rule out major diagenetic or metamorphic overprinting. The systematically collected samples exhibit negative δ¹³C_V-PDB values, characteristic of global cap-carbonate sequences that formed immediately after the Paleoproterozoic glaciation. These strata are subsequently overlain by dolomites displaying the pronounced positive δ¹³C_V-PDB excursion associated with the Lomagundi–Jatuli Event (LJE). Unlike the Sausar Group of India, which records cap carbonates without evidence of the LJE, the Aravalli Supergroup uniquely preserves both features within its Paleoproteozoic succession^[2]. This integrated record establishes the Aravalli Basin as a key site for understanding the temporal link between deglaciation, large-scale carbon-cycle shifts, and atmospheric oxygenation. Furthermore, the coexistence of post-glacial and LJE signatures enables refined global chemostratigraphic correlations with other Paleoproterozoic basins across continents such as South Africa, Canada, and Australia^[3]. These findings highlight the Aravalli Basin’s pivotal role in tracing the aftermath of Paleoproterozoic glaciations and provide new perspectives on how early Earth’s surface environments evolved during one of the most transformative intervals in the planet’s history.

References

[1] Bekker et al. [2005]. Precamb Res. 137(3-4), 167-206.

[2] Goswami et al. [2023]. Precamb Res. 399.

[3] Maheshwari et al. [2010]. Gondwana Res.  417, 195-209.

How to cite: Goswami, A., Jang, Y., and Kwon, S.: When Ice Met Oxygen: Unveiling the Oldest Clues of Earth’s Climate Shift from the Aravalli Supergroup, India. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2953, https://doi.org/10.5194/egusphere-egu26-2953, 2026.

We use benthic isotope data from 491 sediment cores compiled in the World Atlas of late Quaternary Foraminiferal Oxygen and Carbon Isotope Ratios (Mulitza et al., 2022) to evaluate transient simulations across the last 25 kyr performed with BICYCLE-SE, the solid Earth version of the Box model of the Isotopic Carbon cYCLE (Köhler & Mulitza, 2024), which have been updated by data-based constraints on the deglacial release of ~250 PgC from land via permafrost thaw (Winterfeld et al., 2018), extensive petrogenic organic carbon oxidation (Wu et al., 2022) and biomass burning (Riddell-Young et al., 2025). These additional land carbon fluxes reduce mean ocean δ¹³C by 0.1‰ since the Last Glacial Maximum (LGM). The increase in mean ocean δ¹³C is 0.45‰ since the LGM in both data and model, but the rise started only after Heinrich Stadial 1 in the data, but earlier in the simulations. Abrupt reductions in Atlantic Meridional Overturning Circulation during Greenland stadials as suggested from ¹⁴C (Köhler et al., 2024) lead to simulated anomalies in δ¹³C in most ocean boxes, that are not confirmed by the δ¹³C data. Further model-data offsets suggest that the so far applied assumptions on changes in the Southern Ocean physical and biological carbon pumps during the deglaciation in BICYCLE-SE might need to be revised – or point to the limitations of this simple box model approach.        

References:

Köhler, P. and Mulitza, S.: No detectable influence of the carbonate ion effect on changes in stable carbon isotope ratios (δ¹³C) of shallow dwelling planktic foraminifera over the past 160kyr, Clim. Past, 20, 991–1015, https://doi.org/10.5194/cp- 20-991-2024, 2024.

Köhler, P., Skinner, L. C., and Adolphi, F.: Radiocarbon cycle revisited by considering the bipolar seesaw and benthic ¹⁴C data, Earth Planet. Sc. Lett., 640, 118801, https://doi.org/10.1016/j.epsl.2024.118801, 2024.

Mulitza, S., Bickert, T., Bostock, H. C., Chiessi, C. M., Donner, B., Govin, A., Harada, N., Huang, E., Johnstone, H., Kuhnert, H., Langner, M., Lamy, F., Lembke-Jene, L., Lisiecki, L., Lynch- Stieglitz, J., Max, L., Mohtadi, M., Mollenhauer, G., Muglia, J., Nürnberg, D., Paul, A., Rühlemann, C., Repschläger, J., Saraswat, R., Schmittner, A., Sikes, E. L., Spielhagen, R. F., and Tiedemann, R.: World Atlas of late Quaternary Foraminiferal Oxygen and Carbon Isotope Ratios, Earth Syst. Sci. Data, 14, 2553–2611, https://doi.org/10.5194/essd-14-2553-2022, 2022.

Riddell-Young, B., Lee, J. E., Brook, E. J., Schmitt, J., Fischer, H., Bauska, T. K., Menking, J. A., Iseli, R., and Clark, J. R.: Abrupt changes in biomass burning during the last glacial period, Nature, 637, 91–96, https://doi.org/10.1038/s41586-024-08363-3, 2025.

Winterfeld, M., Mollenhauer, G., Dummann, W., Köhler, P., Lembke-Jene, L., Meyer, V. D., Hefter, J., McIntyre, C., Wacker, L., Kokfelt, U., and Tiedemann, R.: Deglacial mobilization of pre-aged terrestrial carbon from degrading permafrost, Nature Communications, 9, 3666, https://doi.org/10.1038/s41467-018-06080-w, 2018.

Wu, J., Mollenhauer, G., Stein, R., Köhler, P., Hefter, J., Fahl, K., Grotheer, H., Wei, B., and Nam, S.-I.: Deglacial release of petrogenic and permafrost carbon from the Canadian Arctic impacting the carbon cycle, Nature Communications, 13, 7172, https://doi.org/10.1038/s41467-022-34725-4, 2022.

How to cite: Köhler, P. and Mulitza, S.: Data-model comparison of marine 13C across Termination I , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3078, https://doi.org/10.5194/egusphere-egu26-3078, 2026.

Climate-induced changes in salinity and hydrological restriction can reshape ecological communities and biogeochemical cycles in anoxic water bodies, thereby altering the productivity–preservation balance and influencing organic carbon burial. This study distinguishes two anoxic depositional modes and employs lipid biomarkers, trace element indices, and C–N stable isotopes to elucidate their ecological and biogeochemical implications. During arid intervals (Mode A), characterized by hypersaline, restricted conditions and high TOC, elevated δ¹⁵N values (~6‰) indicate enhanced denitrification. Although cyanobacterial abundance is relatively high, low Mo/TOC ratios suggest limited Mo availability, which constrains nitrogen fixation. In humid periods (Mode B), corresponding to low‑salinity, open‑system settings with low TOC, δ¹⁵N values decrease (~4.5‰). Increased Mo/TOC ratios point to improved Mo availability that promotes nitrogen fixation, superimposing a nitrogen‑fixation signal on the δ¹⁵N record and causing a slight negative shift even under anoxic conditions. Differences in δ¹³C between the two modes further indicate that higher productivity during arid phases enriches the dissolved inorganic carbon pool in heavier carbon, whereas humid periods are marked by reduced productivity and greater input of terrestrially derived light carbon. Overall, the sensitivity of the nitrogen cycle to environmental perturbation is primarily governed by the supply of Mo—a key cofactor for nitrogenase—rather than cyanobacterial abundance. Meanwhile, aridity‑driven nutrient concentration combined with brief oxidative decomposition under a shallow halocline jointly enhances both organic matter input and preservation, ultimately promoting organic carbon burial. This framework highlights the coupling among climate, nutrient dynamics, trace‑metal limitation, and biological communities, offering an ecological‑process perspective for interpreting nitrogen‑cycle perturbations and carbon‑sink formation in anoxic systems.

How to cite: Chen, A. and Liang, C.: Climate fluctuations drive periodic shifts in anoxic depositional environments: Mo availability regulates nitrogen cycling and organic carbon burial, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3098, https://doi.org/10.5194/egusphere-egu26-3098, 2026.

Organic carbon (OC) burial is a critical process regulating the global carbon cycle and climate system. However, compared to well-studied marine systems, the role and mechanisms of lacustrine OC burial in deep time remain poorly constrained. Despite covering an area only 1/80th that of the oceans, modern lakes contribute 10–50% of the global OC burial, highlighting their exceptional sequestration efficiency. This review synthesizes OC burial records from typical deep-time lacustrine shales, revealing that the geological-scale transition in OC burial capacity was driven by the evolution of lake ecosystems from "dead" and "starved" lakes to "ecologically primary" and "prosperous" ones. Based on the "productivity, preservation, and dilution" ternary equilibrium theory, we evaluate the multi-factor composite controls on the OC burial process, including tectonics, climate, hydro-ecological conditions, volcanic–hydrothermal activities, and marine transgressions. Our findings show that efficient OC burial results from the synergistic coupling of tectonic–climatic–ecological systems. Notably, nutrients from volcanic and hydrothermal activities were crucial for overcoming adverse climatic or ecological conditions—particularly during the "ecologically primary lakes" stage before the Late Paleozoic—thereby enabling effective OC sequestration. Finally, we propose five primary mechanisms for large-scale lacustrine OC burial: (1) volcanic–hydrothermal driven, (2) climate–volcanic activities coupling, (3) climate–basin scale coupling, (4) climate–transgressions coupling, and (5) tectonic–climate coupling. This synthesis not only offers a new perspective from lake records for understanding deep-time Earth's sphere interactions and carbon cycling but also establishes a geological-historical framework for predicting the response of lacustrine carbon reservoirs to future climate change.

How to cite: Liang, C., Chen, A., and Cao, Y.: Lacustrine organic carbon burial in deep time: Perspectives from major geologic events and tectonic-climatic-ecological coupling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3702, https://doi.org/10.5194/egusphere-egu26-3702, 2026.

Methane seeping from the submarine has long been recognized as a driver of climate warming, owing to its oxidation that emits carbon dioxide to the atmosphere. Yet, the biogeochemical processes that transfer methane to organic carbon (OC), serving as a negative feedback on warming, remain largely under constrained. Here, we measured concentration and stable and radiocarbon isotopes of the dissolved and sedimentary OC, as well as foraminifera, across contemporary and past methane seepage settings. Our findings reveal that methane undergoes transformation into OC, promoting its long-term burial in sediments and mitigating climate change. At active methane seeps in the South China Sea, methane contributes up to 23% of dissolved OC in the contemporary bottom water. And our results suggest that methane may be emitted to the water column ~700 m above the seafloor during the Last Glacial Maximum, and subsequently undergoes transformation into OC buried in sediments. It accounts for up to 11% of methane-derived OC burial during the Last Glacial Maximum with active methane seepage events, and reduces the radiative forcing caused by methane emission over glacial cycles. Our discovery of the enhanced methane carbon burial calls for reconsideration of methane’s impact on climate warming.

How to cite: Dong, L., Chu, M., and Bao, R.: The transformation and burial of methane-derived organic carbon in the South China Sea, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4416, https://doi.org/10.5194/egusphere-egu26-4416, 2026.

Ocean productivity is highly sensitive to climate change, but its future trend remains largely unknown, complicating projections for marine ecosystems and fisheries. Past warm climate events offer valuable analogs for understanding the long-term effects of anthropogenic warming on ocean productivity. The Paleocene–Eocene Thermal Maximum (PETM, about 56 million years ago) is one of the most pronounced global warming events in the Cenozoic era, triggered by massive and rapid injections of isotopically light carbon into the ocean-atmosphere system. While previous studies have evaluated ocean productivity during the PETM, proxy records and model results remain contradictory, and the response of fish productivity is also poorly constrained. Here we present global records of ichthyolith accumulation rates (IAR) from deep-sea sediment cores across the PETM. Our new data show the temporal and spatial evolution of pelagic fish productivity as well as the resilience in fish communities. These IAR data are then compared with export productivity estimates derived from marine barite accumulation rates (BAR) from the same or proximal sites to explore their correlation. Using the Earth system model cGENIE, we further conduct sensitive simulations to investigate the roles of elevated atmospheric pCO₂, changes in nutrient supply (internal and external), and ocean circulation in driving carbon export during the PETM. Through combining multi–proxy and model–informed analyses, this study provides an integrated perspective on how ocean productivity and fish communities reacted to abrupt warming, offering a critical long-term context for understanding the future of ocean ecosystems.

How to cite: Zhou, X., Zhang, R., Tsang, M.-Y., and Yao, W.: Reconstructing pelagic fish productivity and export productivity during the Paleocene-Eocene Thermal Maximum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4725, https://doi.org/10.5194/egusphere-egu26-4725, 2026.

Proxy records from the Miocene epoch (∼23‐5 Ma) indicate a warmer climate than today with a reduced meridional temperature gradient. These characteristics have been partly attributed to atmospheric CO₂ changes and differences in the tectonic setting. In this contribution we present climate simulations using the complex coupled earth system model AWI-ESM2  for Miocene boundary conditions to investigate the impact of different atmospheric CO₂ concentrations and paleogeographic configurations.  Besides investigating their individual contribution, we will also examine the combination of both forcing factors and differences that arise from different orographic and bathymetric reconstructions. We will discuss implications for global and meridional temperature responses, as well as sea ice changes and high latitude ocean ventilation.

How to cite: Knorr, G. and Lohmann, G.: The impact of paleogeography and atmospheric CO2 concentrations on Miocene warmth in AWI-ESM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5416, https://doi.org/10.5194/egusphere-egu26-5416, 2026.

Changes in the geological carbon cycle and associated surface input and output CO₂ fluxes drive long-term Cenozoic climate trends mainly through magmatic emissions and weathering of silicate minerals. Proxy records, which indirectly reconstruct past climate conditions, demonstrate a steady decline in both surface CO₂ and temperature since ˜50 million years ago (Ma), punctuated by shorter periods of climatic optima and hyperthermals such as the PETM, EECO, MECO and MMCO. However, lack of constraints in terms of input and output CO₂ fluxes prevents the assessment of responsible processes for these trends. Here, we use a newly developed technique based on a reversible-jump Markov chain Monte Carlo algorithm (rj-McMC) to invert the temporal CO₂ changes from the Proxy Integration Project (CENCO₂PIP) (Hönisch et al., 2023) and obtain estimates of the surface input and output CO₂ fluxes throughout the Cenozoic. We base the inversion on a general formulation of the geological carbon cycle that includes a degassing source and a temperature-dependent sink term, with the temperature time history (Hansen et al., 2023) used as an additional constraint. Reconstructed fluxes reveal that perturbations of the carbon cycle are stronger during the early Cenozoic (i.e., ˜66 – 34 Ma), while these reduce since˜34 Ma. We hypothesise that stronger degassing from the solid-Earth during the EECO and MECO prevent an earlier onset of the Antarctic ice cap during the Eocene. We discuss that the higher carbon emissions during these periods can partially link to the evolution of the Neo-Tethyan magmatic margin, which extinction occurs ˜34 Ma. Results show that carbon flux stabilization since the Oligocene could be due to temperature dependent processes like albedo increase and enhanced silicate weathering in the context of Tibetan Plateau uplift. Finally, we estimate that the net amount of CO₂ removed since ˜34 Ma is four times greater than that of the first half of the Cenozoic.  

References

Hansen, J. E., Sato, M., Simons, L., Nazarenko, L. S., Sangha, I., Kharecha, P., Zachos, J. C., von Schuckmann, K., Loeb, N. G., Osman, M. B., Jin, Q., Tselioudis, G., Jeong, E., Lacis, A., Ruedy, R., Russell, G., Cao, J., & Li, J. (2023). Global warming in the pipeline. Oxford Open Climate Change, 3(1). https://doi.org/10.1093/oxfclm/kgad008.

Hönisch, B., Royer, D. L., Breecker, D. O., Polissar, P. J., Bowen, G. J., Henehan, M. J., Cui, Y., Steinthorsdottir, M., McElwain, J. C., Kohn, M. J., Pearson, A., Phelps, S. R., Uno, K. T., Ridgwell, A., Anagnostou, E., Austermann, J., Badger, M. P. S., Barclay, R. S., Bijl, P. K., … Zhang, L. (2023). Toward a Cenozoic history of atmospheric CO2. Science, 382(6675). DOI: 10.1126/science.adi517.

How to cite: Castrogiovanni, L., Pasquero, C., Piana Agostinetti, N., Vaes, B., Longman, J., and Sternai, P.: Input and output fluxes of surface CO2 throughout the Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5914, https://doi.org/10.5194/egusphere-egu26-5914, 2026.

Investigating changes in ocean oxygenation during past warm climates advances our process understanding of biogeochemical and physical dynamics in the ocean and may inform our predictions of future changes. The Miocene Climatic Optimum (MCO) was a warm climate episode ~15, million years ago (Ma), with high atmospheric CO₂ concentrations that are comparable to end-of-century predictions for mid-range future emission scenarios. Proxy records suggest that the Oxygen Minimum Zone (OMZ) in the Eastern Tropical Pacific (ETP) was small or non-existent during the high-CO₂ MCO, and only expanded when CO₂ declined after 15 Ma. In contrast, the OMZ in the Eastern Pacific was already extensive in the recent preindustrial era, and is currently expanding further with increasing CO₂, due to ocean warming and stratification. Despite the importance of understanding the controls on Pacific OMZ extent under warm conditions, there are no existing model investigations of these opposing OMZ dynamics. Here, we use a climate model with an offline biogeochemical framework to investigate ocean oxygen concentrations during the Miocene for a range of CO₂ concentrations and two different topographic configurations. We compare results to available physical and biogeochemical proxies and assess which combination of boundary conditions best replicates recorded proxy trends. We find that for higher CO₂ concentrations, oxygen declines globally and OMZs expand, particularly in the Atlantic Ocean. However, for one of the topographic configurations, OMZs in the ETP contract under higher CO₂ concentrations. This contraction can be attributed to regionally reduced export production and remineralization rates, which are caused by weaker upwelling due to a southward shifted Hadley cell and correspondingly weaker southern hemisphere trade winds. This atmospheric response is driven by hemispheric asymmetries in warming due to changes in large scale ocean circulation. These results emphasize the complexity and spatial heterogeneity of the marine oxygen response to climate change.

How to cite: Berg, J., Hutchinson, D., Meissner, K., Pasquier, B., Holzer, M., and Auderset, A.: Simulated Ocean Oxygen under Miocene Boundary Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5952, https://doi.org/10.5194/egusphere-egu26-5952, 2026.

Neoproterozoic “snowball Earth” refers to extreme glaciations when sea ice extended from the poles to the tropics and perhaps to the equator. Despite decades of study, the mechanisms that triggered global glaciation are still debated, although many mechanisms link their onset to reductions in atmospheric CO₂ concentration. We use a coupled general circulation model and two geologically constrained paleogeographic reconstructions to re-examine the CO2 threshold for the initiation of the Sturtian snowball Earth (~717 Ma). With modern landmasses, a hard-Snowball transition occurs at 95±5 ppm CO₂, consistent with prior estimates. In contrast, one 720 Ma reconstruction, resists global glaciation down to 6±1 ppm CO₂ – a threshold so low that initiation via CO₂ drawdown might be challenging – while maintaining an "oasis climate" with a small, zonally asymmetric region of open tropical ocean. A second 720 Ma reconstruction glaciates at 110±10 ppm, similar to modern. We show that the oasis climate is possible because the former continental configuration inhibits ocean heat transport out of a small, tropical ocean basin, allowing it to maintain above-freezing sea surface temperatures. While the "oasis climate" lacks the hysteresis expected for snowball glaciations in our climate model, hysteresis might be supplied by land ice sheets. The apparent sensitivity of Earth's snowball glaciation behavior to subtle changes in continental geometry points to a need for better-constrained paleogeographic reconstructions for understanding snowball Earth events and highlight potential challenges to CO₂ drawdown mechanisms for snowball initiation.

How to cite: Fu, M., Graham, R., and Abbot, D.: Paleogeography strongly influences CO2 threshold for Sturtian Snowball Earth initiation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5987, https://doi.org/10.5194/egusphere-egu26-5987, 2026.

Loess deposits are silt sediments that can contain up to 30% carbon. As they are transported into the ocean, whether by wind or by rivers, they can increase the ocean's alkalinity. Recent studies have reported that accounting for the carbon weathering of loess under glacial conditions could increase the global alkalinity flux by more than 50% compared with previous estimates. This, in turn, could lower atmospheric CO₂ concentrations by increasing the ocean's buffering capacity. To test this hypothesis in a transient Earth System Modeling framework and quantify the role of loess weathering in orbital-scale global carbon reorganizations, we employed the cGENIE model, nudged the ocean circulation state to a previously conducted transient 3 Ma CESM1.2 simulation, and applied various loess weathering scenarios. Our results suggest that plausible estimates of loess-derived carbon fluxes can explain a considerable fraction of interglacial/glacial CO₂ variability during the last 1 Ma.

How to cite: Ishizu, M., Timmermann, A., and Yun, K.-S.: Loess weathering as an important contributor to the glacial atmospheric pCO2 drawdown, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6267, https://doi.org/10.5194/egusphere-egu26-6267, 2026.

Long paleoclimate time series combine strong persistence, multiple orbital cycles, and regime shifts, which complicates the analysis of dynamical coupling and predictability. We analyze Cenozoic variability using the Cenozoic global reference benthic foraminiferal carbon and oxygen isotope dataset, in a regime based time series framework that integrates deterministic decomposition, cyclical fractional cointegration, and regime aware forecasting. We divide the record into segments in line with the major Cenozoic climate states. Within each segment, deterministic components are estimated and removed, including linear trends, orbital forcing variables, and harmonic cycles identified via a GARMA based filtering procedure. We then apply cyclical fractional cointegration tests at shared orbital frequencies to assess whether common spectral peaks reflect a stable frequency specific linkage (cointegration) between the proxies and orbital variables. The results reveal pronounced regime dependence. The long eccentricity cycle (405 kyr) shows recurrent evidence of cointegration with both proxies across different climate states. For obliquity, an indication of frequency specific linkage is primarily found after the middle Miocene Climate Transition. Finally, we fit regime specific VAR(2) models to the residuals and report in-sample forecasts, and we generate a 100 kyr out-of-sample projection based on the Icehouse specific dynamics. Forecast behaviour varies across climate states, highlighting that non-stationarity and regime specific dynamics place strong constraints on predictability in long paleoclimate records. 

How to cite: Özer, Y., del Barrio Castro, T., Escribano, Á., and Sibbertsen, P.: Modeling Long Memory Cyclical Trends in the Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7593, https://doi.org/10.5194/egusphere-egu26-7593, 2026.

Coccolithophores, calcifying marine phytoplankton, play a dual role in the oceanic
carbon cycle by contributing to carbon fixation through photosynthesis and to carbon
release via calcification (uptake of bicarbonate and release of CO2). To evaluate the net
effect of coccolithophore long-term evolutionary and productivity dynamics on the car-
bon cycle, we analyzed two sediment cores, MD96-2060 (Mozambique Channel) and MD97-
2125 (Coral Sea), spanning the past 1 Myr. Using automated light microscopy and im-
age recognition, we quantified coccolithophore assemblages, morphology, and calcite mass.
These data were complemented by stable isotope analyses (δ13C and δ18O) of coccolith-
dominated the fine fraction (< 30 µm,) sediment samples. Our results reveal pronounced
coccolithophore bloom phases, characterized by high abundances of Gephyrocapsa caribbean-
ica and Emiliania huxleyi, and sharp increases in total Noelaerhabdaceae mass accumu-
lation rate. The Morphological Divergence Index, a proxy for evolutionary divergence,
exhibits similar long-term trends at both sites, in phase with orbital eccentricity cycles.
Fine-fraction δ13C records display long-term patterns that are absent in benthic and plank-
tonic foraminiferal δ13C records, indicating a persistent coccolithophore-driven isotopic
signal. We interpret this signal as the result of species-specific vital effects in dominant
blooming taxa, particularly during periods of low eccentricity, when reduced ecological
niche partitioning may have favored the proliferation of smaller more cosmopolitan species.
This, in turn, may have led to a significant depletion in δ13C values of the fine fraction
during low eccentricity phases, thereby influencing the marine carbon cycle on orbital
timescales.