PICO: Mon, 4 May, 08:30–12:30 | PICO spot 3
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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 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 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.
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.
