This session aims to address these challenges by showcasing the latest advancements in S2S research across Asia and Oceania. We welcome the submission of interdisciplinary studies that highlight recent advancements in perspectives, methods, and applications. The session will span the breadth of S2S research with contributions that utilize multi-proxy approaches including geophysical data, numerical and analogue modelling, sedimentary provenance analysis, and field observations to develop a comprehensive understanding of sediment routing systems. By promoting diverse research that links S2S dynamics to urgent global issues such as sustainable geoscience, energy transition, geohazard mitigation, and climate change, this session will not only deepen our fundamental understanding of Earth surface processes but also underscore the vital role of S2S science in addressing contemporary societal challenges.
Orals: Tue, 5 May, 14:00–15:40 | Room -2.93
Slope failures and turbidity currents are the most common subaqueous processes and are ubiquitous on all continental margins. Their deposits mass-transport complexes (MTCs) and turbidites commonly co-occur and constitute key infilling elements of sedimentary basins. In this study, we use 3D seismic reflection data from the Taranaki Basin, northwest New Zealand, to investigate how a buried MTC influences the initiation, emplacement, and evolution of subsequent turbidity currents. We interpreted a buried MTC (MTC-1) that contains large transported blocks with well preserved internal reflections and adjacent debrites with chaotic to transparent seismic facies. We reveal that differential compaction driven by rheological contrasts between the blocks and debrites produced a rugose MTC top surface with local relief and asymmetrical depressions. This inherited relief locally enhances flow confinement and slope variability, promoting turbidity current acceleration and repeated hydraulic jumps across local depressions, thereby facilitating transitions to supercritical flow and the development of cyclic steps. Cyclic steps recur on successive stratigraphic surfaces above MTC-1 up to the modern seabed, indicating that inherited MTC relief continued to influence turbidity current over an extended geological timescale. Additionally, retrogressive failure associated with MTC emplacement generated fault-bounded, trough-like depressions in the headwall of MTC-1. These negative-relief features are interpreted to reorganize incoming turbidity currents through reflection and deflection, trapping flow within the trough and progressively focusing near bed transport along the trough axis, ultimately promoting channel incision and initiating a new channel pathway that is oriented approximately perpendicular to the original flow direction. Given that MTCs and turbidity currents are ubiquitous in subaqueous environments, and that differential compaction and retrogressive failure are common features of MTCs. We therefore indicate that combined effects of differential compaction and retrogressive failure exert a fundamental control on deep-water sediment distribution and stratigraphic architecture in deep-water systems.
How to cite: Li, W. and Wu, N.: Influence of Buried Mass-Transport Complexes on the Initiation and Evolution of Turbidity Currents, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15849, https://doi.org/10.5194/egusphere-egu26-15849, 2026.
Hydropower is increasingly central to low carbon energy strategies worldwide, yet its geomorphic and ecological impacts remain incompletely understood. While reductions in downstream sediment load below dams is well documented, a key unresolved challenge lies in quantifying how sediment capture by reservoirs alters sediment composition and disrupts source-to-sink pathways. These compositional changes influence nutrient transfer, habitat quality, and long-term landscape evolution making it essential to understand how dams reshape sediment routing.
The Citarum River, West Java, Indonesia, provides an ideal setting to investigate these dynamics. Flowing ~300km from its source in the volcanic highlands above Bandung to the Java sea, the river hosts three well established dams, Saguling, Cirata, and Jatiluhur, characterised by well-constrained geology and rapid hydropower expansion. Indonesia aims to produce an additional 16GW of hydropower by 2034 as part of a wider goal to increase their overall renewable energy share. Sediment samples were collected along the Citarum River over two field seasons. The 2023 campaign targeted the main channel, comparing sediments entering and exiting reservoirs with upstream reference sites to evaluate the influence of artificial sediment sinks. The 2024 campaign expanded sampling to tributaries to contextualise downstream compositional changes and address gaps identified in 2023. Heavy mineral analysis has been completed for 16 samples, providing a sensitive tracer of sediment provenance and transport processes.
Heavy mineral assemblages are dominated by pyroxene and hornblende, reflecting the volcanic lithologies of West Java. Systematic shifts occur across hydrological boundaries: modern sediments exhibit a low hornblende-pyroxene ratio, whereas ancient deposits within Saguling reservoir show a significantly higher hornblende-pyroxene ratio, potentially reflecting longer residence times and preferential pyroxene alteration under hot, humid conditions. Increased hornblende-pyroxene ratios in modern low-energy settings further support energy-dependent mineral sorting. Reduced diversity in the Cirata reservoir, followed by downstream increases in e.g., rutile, xenotime, and zircon highlight disruptions in source-to sink-connectivity linked to reservoir trapping, tributary inputs, and/or channel erosion. Hydrological and sediment-transport modelling in MATLAB with TopoToolbox and CASCADE Toolbox, incorporating discharge, rainfall, and runoff datasets is underway to evaluate the influence of Java’s strong seasonal hydrology on sediment transport and composition. Integrating these models with heavy mineral stratigraphy will help assess the reliability of mineralogical signals as proxies for dam-driven perturbations to sediment routing.
This combined stratigraphic and modelling approach provides new insight into how hydropower infrastructure reshapes sediment pathways from source to sink, with implications for future hydropower development in Indonesia and other rapidly urbanising, energy‑intensive regions.
How to cite: Holmes, S., Gough, A., Hikmy, I., Rudyawan, A., Nicholson, U., and Dodd, T.: Sinks Before the Sea: Rethinking Source‑to‑Sink Pathways in a Dam‑Stepped River. An example from the Citarum River, Java, Indonesia., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7183, https://doi.org/10.5194/egusphere-egu26-7183, 2026.
The Sabah province of northern Borneo records a long-lived achieve of deep marine turbidite deposition ranging in age from the Mesozoic to the Early Miocene. Whilst the Mesozoic is poorly preserved, the Paleogene to Early Miocene deep water deposits form a relatively complete succession that was deposited along the southern margin of the Proto-South China Sea (PSCS). This comprises the Sapulut and Trusmadi Formations of central-south Sabah, the Labang and Kulapis Formations of eastern Sabah, the Kudat Formation of NW Sabah and the Crocker Formation of western Sabah. Sandstone petrography, heavy mineral analysis and detrital zircon U-Pb geochronology reveal the changing provenance sources associated with the evolution of the PSCS across key stratigraphies and can be used to reconstruct its subduction history. Most analysed formations contain abundant ultra-stable heavy minerals and Mesozoic zircons which indicate multi-recycling from southern sources. However, volcanic lithic fragments in some Labang Formation samples and Middle Eocene zircons in a lower Crocker Formation sample, as well as unstable heavy minerals such as apatite and epidote, indicate input from contemporaneous volcanism, likely derived from the PSCS subduction arc to the north. The thickest and most extensively exposed deep water sequence, the Crocker Formation in western Sabah, was deposited by two different drainage systems. The lower part of the Crocker Formation has a provenance similar to the Rajang Group in Sarawak and is interpreted as a more distal equivalent sourced by multi-recycling of Borneo and Malay Peninsula sources with some input from the Cagayan/PSCS arc. In contrast, the upper Crocker Formation has a provenance similar to the Nyalau Formation in Sarawak and is interpreted as its deeper marine continuation, sourced by sediments from the Sunda Shelf-Malay Peninsula transported in a drainage system which by-passed SW Borneo. The detrital mineralogy of parts of the Labang and Kulapis Formations suggest an extension of this Nyalau-Upper Crocker depositional system into eastern Sabah. In the Early Miocene the Palawan microcontinental fragment collided with the Cagayan Arc and finally closed the PSCS. The forearc was uplifted and mélanges preserved across eastern Sabah document this collision. The uplifted forearc was most likely the source of sediments in the Lower Miocene Temburong Formation in western Sabah, which marks the end of deep marine deposition in Sabah.
How to cite: Breitfeld, T., van Hattum, M. W. A., Hall, R., Burley, S., Hennig-Breitfeld, J., Franzel, M., Suggate, S. S., Vermeesch, P., and Webb, M.: Provenance of Paleogene to Early Miocene deep-water sedimentary rocks in Sabah, northern Borneo and implications for the Proto-South China Sea subduction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9548, https://doi.org/10.5194/egusphere-egu26-9548, 2026.
Instantaneous event deposits (e.g., turbidites and slumping layers) are common and occur frequently in the abyssal plain of marginal seas. These instantaneous deposits represent seconds to days in duration, and may significantly impact age-depth models and interpretation of paleoclimate history based on sedimentary sequences recovered in deep cores. However, these event deposits have rarely been considered when investigating IODP/ODP deep cores from marginal seas. To resolve this problem, we take the South China Sea as a typical research example, which is one of the largest active marginal seas worldwide. We apply the methodology of high-resolution event sedimentology to Hole U1433A (189-0 m, 800-0 kyr) from the SW South China Sea deep basin. We identify centimeter-to-meter-scale turbidite layers (N=129) using high-resolution NGR, GRA, magnetic susceptibility data, and core images. These instantaneous event deposits account for ~16% of the total sediment thickness in Hole U1433A. We refine the preliminary age-depth model that is based on paleomagnetic and microfossil ages recovered from the hole by removing those instantaneous event deposits. We further test the effectiveness of our revised approach by comparing paleoclimate profiles that either include or omit those event layers. This test indicates that the event-free approach is effective and essential for a better reconstruction of the age-depth model and paleoclimate history based on the IODP deep core. Our innovative sedimentological methodology may also prove suitable for other marginal seas with frequent instantaneous event deposits elsewhere in the world.
How to cite: Li, X., Sun, S., Zhang, Y., Mao, Z., Jin, L., Zhao, Y., Alsop, G. I., Liu, Z., and Lu, Y.: Frequent event deposits in IODP Hole U1433A (South China Sea) over the past 800 kyr: Implications of a revised methodology for chronology and paleoclimate reconstruction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-361, https://doi.org/10.5194/egusphere-egu26-361, 2026.
Clinoforms are characterized by basinward-dipping chronostratigraphic surfaces. They are ubiquitous sedimentary slope architectures in continental-margin settings worldwide. The growth of clinoforms records the influence of sea-level change, sediment supply, and basin subsidence. Quantifying clinoform geometry provides a basis for reconstructing these controlling processes through geological time. We use high-resolution 3D seismic data covering approximately 6,000 km² in northwestern Sichuan Basin, South China. In the study area, the Ediacaran to Cambrian succession records three major shifts in sedimentary environments, from mixed siliciclastic-carbonate shelf system (Doushantuo Formation), to carbonate-dominated platform system (Dengying Formation), to clastic-dominated deepwater system (Maidiping and Qiongzhusi Formation), and ultimately to carbonate-dominated shallow-water system (Longwangmiao Formation). Here, we focus on the clastic-dominated succession of the Qiongzhusi Formation to reconstruct sediment provenance, constrain sedimentary evolution, and evaluate the influence of regional tectonics. Seismic interpretation reveals the lower section of the Qiongzhusi Formation contains submarine fans, turbidite channels, and mass-transport complexes, indicating gravity-driven depositional processes in a relatively deepwater environment. Within the upper section, we interpret at least seven clinoform sets (C1~C7). These clinoform sets show oblique stacking, recording a progradational, basinward migrating shelf-edge trajectory, which is consistent with limited accommodation and sea-level fluctuations during the evolution. To infer progradation rates and total sediment flux during clinoform evolution, we calculate the progradation factor (Pf) and volumes (Ve) of the clinoform sets. Based on the results, we demonstrate that the clinoforms developed in multiple phases, corresponding to periods of intensified and weakened orogenic loads caused by tectonic activity in the northwestern region. In the first stage (Start to C1-C2), the orogenic loading intensified and resulted in a rapid increase in sediment influx and accelerated progradation, as reflected by elevated Pf and Ve values. In the second stage (C1-C2 to C3-C4), the orogenic loading was subdued and led to slower progradation and reduced sediment flux, as indicated by decreased Pf and Ve values. In the third stage (C3-C4 to C6), the orogenic loading intensified again. In the final stage (C6 to End), the orogenic loading neared termination, as evidenced by an abrupt decrease in Pf and Ve values. Thus, we propose that the increases and decreases in sediment flux were driven by the orogenic activity (i.e. Motianling Orogeny) in the northwestern region of Sichuan Basin. In conclusion, the alternating stages of intensified and subdued orogenic activity, and the associated increases and decreases in sediment flux, ultimately controlled the infill processes. We also suggest that quantitative analysis of clinoform sets can effectively reveal the detailed infill processes of sedimentary basins through time and can be readily applied to basin analyses in other similar settings.
How to cite: Han, Z., Wu, N., and Gu, Z.: Sedimentary Evolution of the Cambrian Qiongzhusi Formation, Northwestern Sichuan Basin: Insights from Quantitative Clinoform Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6250, https://doi.org/10.5194/egusphere-egu26-6250, 2026.
Clinoforms are inclined depositional units formed by sedimentary processes, commonly developed in a wide range of subaqueous environments. They constitute key geomorphic elements within source-to-sink systems and play an important role in the transport of terrigenous clastic sediments and the evolution of sedimentary basins. Compared with marine settings, the architecture, evolution, and controlling processes of clinoforms in lacustrine basins remain comparatively underexplored, due to the limited availability of high-resolution 3D seismic data. In this study, we integrate sedimentary cores and well logs from 16 industry wells, along with a 3D seismic dataset covering c.1500 km2 to investigate the sedimentary evolution of lacustrine clinoforms within the Triassic Yanchang Formation on the southwestern margin of the Ordos Basin. Seismic interpretation interprets eight clinoforms (C1-C8). These clinoforms are characterized by sigmoidal and oblique geometries, with slope gradients ranging from 0.77° to 1.10° for the sigmoidal type and 0.55° to 0.93° for the oblique type. The eight clinoforms record a three-phase evolution. Stage I (C1-C2) is dominated by oblique clinoforms, Stage II (C3-C5) by aggradational to progradational sigmoidal clinoforms, and Stage III (C6-C8) by oblique clinoforms. The thickness of these clinoforms shifts from the topset to the foreset and ultimately to the bottomset, indicating a progressive progradation of the depocentre from the southwestern toward the central (northeastern) lacustrine basin. Well-log interpretation shows that the base of the topset is typically composed of 2.5-10 m thick sandstones overlain by 0.5-5 m thick mudstones, with sandstone content exceeding that of mudstone. Core observation indicates that cross bedding and parallel bedding are the dominant sedimentary structures. In the foreset, well-log interpretation indicates 3-15 m thick mudstones interbedded with thin (1-5 m) sandstone layers. Core observation shows deformed bedding, flaser bedding, and homogeneous mudstones. In the bottomset, well-log interpretation reveals thick (2-10 m) sandstone packages with minor (1-5 m) mudstone intercalations. Core observation documents massive to graded sandstones, slump-related deformation structures, and flame structures. Based on seismic interpretation, well-log analysis and core observation, we interpret that the topset is dominated by meandering fluvial depositional environments, including channel and point-bar settings. The foreset corresponds to slope environments associated with headwall scarps of mass-transport complexes and background muddy sedimentation, whereas the bottomset represents deep lacustrine environments dominated by gravity-flow deposits, including slumps, debris flows, and turbidity currents. In contrast to clinoforms developed in submarine settings, where large accommodation commonly prevents preservation of complete slope infill successions, the lacustrine clinoforms of the Yanchang Formation record a complete infilling evolution of lake basins. Understanding the infilling evolution of lacustrine clinoforms therefore provides a robust sedimentological framework for reconstructing basin evolution that is difficult to resolve in submarine settings.
How to cite: Peng, J., Wu, N., and Hui, X.: Clinoform Evolution in a Triassic Lacustrine Environment, Southwestern Ordos Basin: Insights from Core, Well-Log, and 3D Seismic Data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8701, https://doi.org/10.5194/egusphere-egu26-8701, 2026.
Rivers draining the Himalaya constitute major atmospheric CO2 sinks due to exceptionally high chemical weathering fluxes. However, the net CO2 drawdown depends on both the contribution of end members such as carbonate and silicate weathering, precipitation, and the extent of CO2 supersaturation and potential emission evasion. Here, we integrate a multi-endmember inverse mixing model with freshwater carbonate-system calculations (CO2SYS) for Brahmaputra main-channel river water samples, suspended particulate matter (SPM) and bed sediments from Assam, India. Size-fractionated silicate leaches (>63 µm, 63–10 µm, 10–2 µm, <2 µm) and SPM plotted on MIA–AF–CN–M ternary cluster toward Mg–Fe–Al–rich silicate fields, consistent with a notable freshly supplied mafic component in the sediment pool (Figure 1a). An inverse framework in charge-equivalent tracer space (χCa, χMg, χNa, χK, χCl, χSO₄; normalized by Σ⁺ = Ca2++Mg2++Na++K+) is used to apportion contributions from precipitation, carbonate, and silicate weathering. Model results indicate carbonate-dominated dissolved ion generation (f_carb ≈ 0.52–0.69) with a smaller, yet consistent silicate contribution (f_sil ≈ 0.21–0.33). An independent forward mass-balance, constrained by regional rain chemistry and published silicate ratios for trans Himalayan and Himalayan rocks, produces comparable silicate and carbonate fractions, thereby corroborating the inverse apportionment. CO2SYS calculations based on measured alkalinity and pH yield pCO2 ≈ 680–2420 µatm (pH ≈ 7.6–8.2), which indicates persistent CO2 supersaturation. The ratios of total alkanility to dissolved inorganic carbon (TA/DIC) are consistently less than 1 (TA/DIC ≈ 0.955–0.995). In contrast, a theoretical weathering-only TA/DIC, calculated by balancing sulphuric acid, carbonate, and silicate weathering in charge equivalent space, ranges from 2.0 to 2.9. This DIC excess (theoretical DIC – observed DIC) implies the presence of additional CO2 along the reach beyond that supplied by weathering. Subansiri, a tributary of the Brahmaputra, shows the highest pCO2 and DIC excess coupled with the lowest SPM load (0.0075 g/L). The theoretical weathering framework indicates these sediments as a net CO2 sink (Figure 1b). The persistently low TA/DIC ratios (<1) and excess DIC relative to theory suggest additional in-stream CO₂ sources, possibly from organic matter decomposition and sulphuric-acid–driven weathering.
How to cite: Ray, I., Das, R., Xie, H., He, S., and Wang, X.: Provenance of weathering-derived dissolved ions and CO2 balance in the upper Assam Brahmaputra Valley, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18732, https://doi.org/10.5194/egusphere-egu26-18732, 2026.
The elemental (major, trace, and rare-earth elements - REEs) distribution in sedimentary rocks provides an essential tool for basin-scale investigations, enabling the interpretation of geochemical characteristics within stratigraphic successions and thereby providing regional provenance and insights into the tectonic evolution of the basin. Here, numerous discrimination diagrams based on the major, trace, and rare earth element (REE) geochemistry were used to infer the sediment provenance, degree of weathering, and tectonic setting of the Permian Pranhita-Godavari (PG) Basin in South-Eastern India. Permian extensional basins are widely documented across the Gondwana basin in India, and the Chintalpudi sub-basin of the PG preserves a thick (~3000 m) and complete Gondwana sequence, spanning from the Permian Talchir diamictites to the Cretaceous Gangapur Formation. This research presents new geochemical results from the Barakar and Kamthi Formations within the Chintalpudi sub-basin, aiming to understand the sediment provenance, tectonic evolution, and weathering phenomena during the Late Permian. The distributions of major, trace, and rare-earth elements indicate that the clastic sediments are compositionally mature and derived predominantly from intensely weathered continental sources. The Post-Archean Average-Australian-Shale (PASS) normalized REE data shows enrichment of light rare earth elements (LREE) with relatively flat heavy rare earth elements (HREE), and a negative Europium (Eu) anomaly implies that the majority of contributing source rocks were felsic, with minor input from rocks of andesitic composition. Furthermore, multi-parameter discrimination plots using major (K2O/Na2O vs. SiO2/Al2O3), log (K2O/Na2O)/SiO2, and trace elements (La/Y vs. Sc/Cr) compositions reveal that the majority of the samples in the Chintalpudi sub-basin are part of a passive continental geotectonic setting. The ratio of Zr/Sc and Th/Sc is higher, corroborating the felsic origin without sediment recycling. Major oxide ratios indicate that the samples are highly mature and have a high chemical index of alteration (CIA), with a low index of compositional variability (ICV), suggesting that they were deposited in warm and humid climatic conditions, with intensive weathering during deposition.
Keywords: Permian Shale, Provenance, Weathering, tectonic setting, Chintalpudi sub-basin
How to cite: Prusty, D., Mani, D., Bhattacharya, S., and Krishna, A. K.: Geochemistry of the Permian shales in the Chintalpudi sub-Basin, Pranhita-Godavari Basin, India: Implications for Provenance, weathering, and tectonic setting, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21200, https://doi.org/10.5194/egusphere-egu26-21200, 2026.
The deep-time Cenozoic history (the last 60 Myr) of the Barents Sea shows complex interplay between tectonics, climatics and surface processes. What did the actual paleotopography look like back then? How did the climate perturbation control the sediment transfer from the source area to the sink? We use a coupled model of GPlates tectonic reconstruction software and Badlands – basin and landscape open-source codes to untangle these intricate processes. The model is calibrated using available seismic and well datasets, including biostratigraphy data. The outcome of this study is important to understand the impact of climate and how our Earth responded in the past, e.g. PETM (Paleocene–Eocene Thermal Maximum). The basin-landscape configuration along the Barents Seaway is also crucial for analysing the ocean circulation between the Atlantic and Arctic oceans during the Cenozoic, which is key for ocean/climate modelling and has also global climatic implications.
How to cite: Lasabuda, A. P. E., Shephard, G., Salles, T., and Zahirovic, S.: Sedimentary source-to-sink and landscape evolution in the northern Barents Sea during the Cenozoic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1558, https://doi.org/10.5194/egusphere-egu26-1558, 2026.
Northeastern Azerbaijan occupies a complex geodynamic setting at the convergence of the Scythian-Turanian (Epihercynian) Platform and the Meso-Tethyan accretionary prism, evolving along the Northern Gondwana margin. Functioning as a key segment of the regional North Crimea – Greater Caucasus – Kopetdagh Meso-Tethys marginal sea, the accretionary prism records a pivotal transition from Lower-Middle Jurassic shale-rich aspid facies to Cretaceous flysch sequences. Despite decades of research on Mesozoic source rocks formed within this complex geodynamic setting, the lack of a global realm-based framework has historically led to contradictory evaluations of the stratigraphic attribution of effective source rocks. This study resolves these inconsistencies by integrating geochemical and paleontological data, revealing that the Jurassic-Cretaceous succession reflects a distinct Boreal-Tethyan polarity. This polarity is interpreted to arise from contrasting source-to-sink configurations that controlled the accumulation and preservation of organic-rich sediments.
We identify the massive Middle Jurassic (Aalenian-Bajocian) shale succession as a regional gas-prone-dominated system (max. TOC 2.43%); its mixed Type II/III kerogen signature and paleoenvironmental context mirror those of European epicontinental basins. Consistent with global platformal trends, the Neocomian unconformity lies directly upon Middle Jurassic shales across the northern domain. This confirms the negligible regional role of the Upper Jurassic Callovian-Tithonian succession, globally recognized as the most prolific Mesozoic source rock interval, which is here constrained by uplift-driven erosion and low-latitude (~15°N) aridity, except in restricted zones where preserved biohermal limestones reflect warm Meso-Tethyan influence.
Consequently, the overlying Neocomian succession exhibits marked heterogeneity, with geochemical evidence aligning with regional paleontological records. While predominantly regressive and gas-prone in the Boreal northern sector, southern zones subject to intensive Meso-Tethyan influence record "pulse-like" Tethyan transgressions that deposited discrete, high-quality oil-prone shale intervals, mainly within the Hauterivian-Barremian (max. TOC 5.96%; HI up to 557 mg HC/g TOC). These pulse-like inflows created temporary anoxia in the southern flysch basin, favoring high-quality organic matter preservation comparable to that in the oil-prone Tethyan Zagros Basin (Garau Fm.), characterized by Type II kerogen and HI values reaching 600 mg HC/g TOC.
Crucially, the Upper Cretaceous Cenomanian-Coniacian shale succession (Kemishdagh and Kemchi Fms.) emerges as the region’s primary oil-prone system (TOC 2.92-6.02%; HI 406-479 mg HC/g TOC). Attributed to Oceanic Anoxic Event 2 (OAE 2), its exceptional productivity parallels that of the prolific Tethyan Zagros Basin to the south, while standing in sharp contrast to the organic-lean, Boreal-influenced Terek-Caspian Basin to the north, confirming that Tethyan oceanic events exerted limited influence on the Eurasian interior. Supported by the alternation of thick shale layers with tuff and bentonite interbeds within the Upper Albian-Coniacian succession of the accretionary prism, this OAE 2 signature correlates with the Late Albian-Late Turonian explosive volcanic phase documented in local reports and is biostratigraphically anchored by Tethyan radiolarian colonies. Furthermore, co-occurring cosmopolitan radiolarians, carbonate-shelled planktonic foraminifera, and benthic taxa north of the prism reveal that, despite dominant Tethyan control, the basin maintained biotic connectivity with the European epicontinental province.
How to cite: Abbasov, O. R., Khuduzade, A. I., Guliyev, I. S., J. Yolchuyeva, U., Baloglanov, E. E., Jafarova, R. A., Akhundov, R. R., Samadov, E. S., and Bashirov, O. Kh.: Mesozoic source rock systems at the junction between Eurasia and Gondwana: Tethyan vs Boreal controls in the Southeastern Caucasus, Northeastern Azerbaijan , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14353, https://doi.org/10.5194/egusphere-egu26-14353, 2026.
The Middle to Late Triassic Jilh Formation is a mixed siliciclastic-carbonate succession with complex stratigraphy. It is recognized across the Arabian Peninsula as hosting complete petroleum systems, including source rocks, reservoirs, and seals, as well as aquifers. Despite its economic significance, research on the Jilh Formation remains limited, largely due to its internal complexity and production challenges, such as overpressure zones. Furthermore, its depositional and ichnological characteristics remain poorly constrained.
This study investigates a 45-meter-thick outcrop of the Lower Jilh Formation in the Riyadh Region through an integrated sedimentological and ichnological approach. Field-based analyses were complemented by laboratory investigations, including thin section petrography and geochemical characterization.
Six siliciclastic facies were identified: (1) green, massive, fissile shale with sparse bioturbation; (2) yellow to reddish, massive to faintly laminated siltstone with limited Skolithos and Arenicolites; (3) horizontally laminated very fine-grained sandstone with sparse bioturbation and diverse ichnofauna; (4) heavily bioturbated, very fine- to fine-grained sandstone dominated by monospecific ichnogenera (e.g., Taenidium, Skolithos, and Rhyzoliths); (5) current-rippled, very fine- to fine-grained sandstone with moderate bioturbation (e.g. Skolithos and Lockeia); (6) low- to high-angle cross-bedded, fine- to medium-grained sandstone devoid of bioturbation.
These facies represent an estuarine to fluvial system, including channels, point bars, proximal estuarine settings, and a central estuarine basin. The dominance of monospecific ichnofacies, low bioturbation intensities, and absence of fully marine trace fossils suggest environmentally stressed conditions, likely related to salinity fluctuations, rapid sedimentation, and intermittent subaerial exposure.
Geochemical analysis of the outcrop reveals distinct vertical variations in elemental concentrations, delineating three distinct geochemical zones: from bottom to top (1 moderate Si and Al concentrations, indicative of mixed siliciclastic input, with minor peaks in Ca and Mg suggesting intermittent carbonate influence; (2) high Si content accompanied by a sharp decline in Al, Ca, and Mg, reflecting a dominance of coarse, quartz-rich terrigenous sediment; and (3) moderate Si and Al values with localized increases in Ca and Mg, pointing to a return of mixed siliciclastic–carbonate deposition. These geochemical trends can further be utilized to interpret paleoproxies, such as weathering intensity, paleoprovenance and fluctuating depositional conditions within the Jilh Formation.
Despite evidence supporting a fine-grained fluvial system, lateral facies correlation remains challenging due to the erosional nature of thick channel deposits and frequent pinch-outs of sedimentary units. Future studies should include multiple outcrop descriptions to address these limitations. Nonetheless, this study contributes to a deeper understanding of the heterogeneity and paleoenvironmental characteristics of the Lower Jilh Formation, offering valuable insights for improved reservoir characterization.
How to cite: Insuasti Iles, L. A. and Ayranci, K.: Triassic Facies Evolution of the Lower Jilh Formation: Integrated Sedimentological, Ichnological, and Geochemical Insights from Central Saudi Arabia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5066, https://doi.org/10.5194/egusphere-egu26-5066, 2026.
Sedimentary black carbon (BC), formed during incomplete combustion of biomass and fossil fuels, represents a chemically refractory carbon pool and an important long-term sink in the global carbon cycle. Coastal margins are major repositories of terrestrial organic carbon (OC) including BC, yet estimates of BC sequestration in these regions remain highly uncertain. Most existing datasets rely on the CTO-375 method, which isolates BC based on thermal resistance following acid pretreatment. However, this approach does not fully account for mineral-associated OC, particularly OC stabilized by clay minerals, potentially leading to systematic overestimation of BC.
Here, we investigate the extent and controls of this methodological bias by comparing BC contents obtained using the conventional CTO-375 protocol (HCl pretreatment only) and a modified protocol that includes HF treatment to remove clay minerals along a transect of Eurasian marginal seas. BC contents measured without HF treatment were consistently higher, with proportional overestimations (ΔBC) ranging from 39% to 94% and showing pronounced regional variability. ΔBC correlated positively with smectite content, but not with grain size, indicating that clay mineral composition, rather than total clay abundance, governs BC overestimation.
These findings indicate that the measurement of BC content in sediments should take the mineral composition into consideration, otherwise the climatic negative feedback associated with sedimentary BC burial would be overestimated.
How to cite: Yu, W., Du, J., Hu, L., Bai, Y., Wang, J., and Shi, X.: The impacts of clay minerals on the quantification of black carbon in marginal sediments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19594, https://doi.org/10.5194/egusphere-egu26-19594, 2026.
Coastal regions across Southeast Asia were drastically transformed during the post glacial period due to sea level rise, yet the paleoenvironmental development of eastern Thailand remains poorly understood compared to other regions. As peat swamp ecosystems are highly sensitive to climate variability and hydrological changes, they can serve as an important archive of past environmental shifts. This study presents a high-resolution 8,100-year multi-proxy record from three sediment sequences retrieved from the Tha Kum peat swamp located 15-km from the modern shoreline in eastern Thailand. We used elemental geochemistry (XRF), total organic carbon (TOC), stable isotopes (δ13C, δ15N, and C/N ratios), and n-alkane distributions to reconstruct the landscape development.
The stratigraphic sequence of the oldest core (NU4) is divided into four distinct units. The basal Unit 4 (~8100-7600 cal yr BP) exhibits highly variable organic matter provenance, with δ13C and C/N ratios spanning freshwater, marine, and terrestrial sources, reflecting a lake that was indirectly influenced by early Holocene sea-level rise and tidal back water effects. A significant shift occurs in Unit 3 (7600–7350 cal yr BP), characterized by peaks in Sulfur (S) and TOC, alongside lower aquatic proxy (Paq) values, representing the establishment of shallower lake or wetland system due to coastal progradation following the mid-Holocene sea-level highstand. Unit 2 (7350–2600 cal yr BP) exhibits prolonged geochemical stability following the highstand. High resolution radiocarbon dating indicates a hiatus between 2600 and 200 cal yr BP, which could be the result of relatively dry conditions. This hiatus is followed by the deposition of the most recent sediment (Unit 1), which is characterized by a sharp decrease in Ti and a maximum TOC, signaling a transition to a modern organic-dominated peat swamp system. This shift was likely driven by a stabilization of the local water table or sea level.
While the study area is currently managed by the Forest Industry Organization to balance plantation, industry, and conservation, the stability of this ecosystem is threatened by future sea-level rise and fluctuating precipitation patterns. These could potentially lead to ecosystem degradation through the modification of local hydrological and geochemical conditions.
How to cite: Wangritthikraikul, K., Ladd, S. N., Dubois, N., and Chawchai, S.: Multi-proxy Holocene paleoenvironmental reconstruction from Tha Kum Peat Swamp, Eastern Thailand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17544, https://doi.org/10.5194/egusphere-egu26-17544, 2026.
East Asia, including the Korean Peninsula, has been located along an active continental margin since the Mesozoic, where magmatism and fault activity have been primarily controlled by changes in subduction dynamics. In this region, numerous Cretaceous sedimentary basins of various scales developed along the eastern margin of the Eurasian Plate. In particular, from the mid-Cretaceous to the early Paleogene, intensive magmatic activity occurred along the subduction-related margin, forming the Gyeongsang Volcanic Arc that extended across the present-day Korean Peninsula and proto-Japan. The development of such a volcanic arc is expected to have exerted first-order control on the reorganization of source-to-sink systems in adjacent sedimentary basins.
The Gyeongsang Basin, the largest Cretaceous basin in Korea, is located in the southeastern part of the peninsula. The Seongpori Formation on Geoje Island in the southeastern part of the basin, was deposited adjacent to rocks related to the Gyeongsang Volcanic Arc. To constrain the depositional age and sediment provenance of the Seongpori Formation, we conducted detrital zircon U–Pb dating using LA–ICP–MS on six samples (four from the northwestern island and two from the southeastern island).
Maximum depositional ages were estimated using the maximum likelihood age (MLA) method. The resulting MLAs range from 98 to 93 Ma for the northwestern samples and from 106 to 105 Ma for the southeastern samples. Provenance analysis indicates that the common major sediment sources of the Seongpori Formation were Paleoproterozoic and Mesozoic rocks exposed in the Yeongnam Massif, which borders the western and northern parts of the Gyeongsang Basin. In addition, some northwestern samples contain Neoproterozoic and Paleozoic zircons, which are interpreted to have been derived from more distal sources, such as the Okcheon Belt located in the northwestern part of the Yeongnam Massif, or possibly from the Gyeonggi Massif farther to the northwest.
The Cretaceous detrital zircon age spectra show clear spatial variations. Northwestern samples are dominated by 100–90 Ma zircons, whereas southeastern samples are characterized by an older and broader age range of 115–100 Ma. These differences are interpreted to reflect spatial variations in magmatic activity within the Korean Peninsula and proto-Japan areas of the Gyeongsang Volcanic Arc, as well as a change in sediment provenance. We infer that the sediment sources of the Seongpori Formation varied spatially and that a shift in the source-to-sink system occurred at ~100 Ma. This timing coincides with the development of an andesitic stratovolcano at ~99 Ma in central Geoje Island, suggesting a possible reorganization of the drainage system induced by volcanic arc construction.
How to cite: Park, Y. J., Chae, Y.-U., and Lim, H. S.: Maximum depositional age and sediment provenance of the Cretaceous Seongpori Formation (Geoje Island, Korea) constrained by detrital zircon U–Pb geochronology., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16706, https://doi.org/10.5194/egusphere-egu26-16706, 2026.
The rivers draining towards the northeast into the southwestern South China Sea maybe derived from a number of potential sources both in mainland Asia, the Malay Peninsula, as well as the islands of Borneo and Sumatra. Reconstructing the evolution of drainage systems is important if we are to understand how the evolving patterns of rivers that emerged during each sea level low stand period changed through time since these may be important in increasing rates of biological speciation, at least during the Pleistocene. We investigated whether different areas yielded sediments that can be distinguished from one another and from the Mekong and Chao Phraya by analysing modern river sands. Major element compositions are rarely unique for given source areas, being strongly affected by grain size and degrees of chemical weathering. There is no single process that controls the intensity of chemical weathering across SE Asia and this likely reflects the combined influence of temperature, rainfall and tectonics in controlling transport speed and rates of alteration. The different tectonic provinces do however show coherent differences in Sr and Nd isotopes, although it is unclear if Sabah can be distinguished from Sarawak within Borneo. Detrital zircon U-Pb dating is even more effective at resolving these sources. All the samples differ from the relative similar Chao Phraya and Mekong rivers that are dominated by Indosinian, Inthanon Zone (200-300 Ma) grains and a significant “Caledonian" (440-600 Ma) population. In contrast, all samples from the Malay Peninsula are almost entirely Indosinian/Inthanon. All Sumatran rivers contain large proportions of <20 Ma grains, derived from the active arc, as well as 80-140 Ma grains from older Mesozoic arc basement, similar to that seen in the Schwaner Mountains of Borneo. As for the Sr-Nd isotopes the rivers of Borneo has similar populations in Sabah and Sarawak, with the largest being an Indosinian population, but also with large minority populations of Schwaner and Caledonian ages. Borneo is the only source area with a notable 800-1000 Ma “Gondwana” population that is otherwise restricted to the Mekong and Chao Phraya. Our work indicates that these tools can constrain sediment provenance on the Sunda Shelf. They also imply that the continental basement under southern Sumatra has similarity to that of Borneo, especially the Schwaner Mountains, in contrast to some older reconstructions.
How to cite: Clift, P., McGanity-Smith, B., Breitfeld, T., Gough, A., and Carter, A.: Deconvolving Sunda River Systems Using Multi-Proxy Provenance Tools, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4026, https://doi.org/10.5194/egusphere-egu26-4026, 2026.
The island of Sulawesi in eastern Indonesia has been shaped by multiple periods of complex tectonic interaction and volcanism, driving recent scientific interest in regional geohazards (e.g., earthquakes and landslide-drive tsunamis) and the formation of natural resources (e.g., natural hydrogen). Despite this, fundamental questions about the geological evolution of Sulawesi remain understudied, such as the timing and style of the collision between the Banggai-Sula Microcontinent and the East Sulawesi Ophiolite. This collision zone has been largely overlooked due to the remote and rugged terrain along the suture. Here, we present new fieldwork data from the Batui Fold-Thrust Belt of the East Arm of Sulawesi, along with remote sensing, petrographic, and biostratigraphic data to reveal the stratigraphic and structural features of this suture zone, highlighting the key depositional environments that developed before, during, and after collision.
Fieldwork, petrography, and biostratigraphy data reveal dismembered upper mantle and lower crustal rocks of the East Sulawesi Ophiolite in tectonic contact with Middle to Late Miocene shallow marine limestone of the Salodik Formation. These limestones interfinger with coeval siliciclastic rocks of the Poh Formation recording a transition from fore- and back-reef environments to a foreshore setting. These rocks are overlain by conglomerates of the Pliocene Bongka Formation that was deposited in a disconformable contact atop the East Sulawesi Ophiolite and marks final merging of the Banggai-Sula microcontinent. Crucially, the Middle to Late Miocene age of the Salodik Formation, together with reworked Eocene foraminifera, indicates uplift and progressive reef closure prior to renewed shallow-marine deposition. This has not been previously recognised from this formation elsewhere in Sulawesi during NW-directed Miocene collision. These interpretations are further supported by SE-verging structures in the hanging wall of the Batui Fold-Thrust Belt, which defines the main regional suture zone. By constraining the timing of uplift and reef shutdown, this study defines the source-to-sink boundary conditions for sediment generation, transport, and deposition during ophiolite collision in eastern Indonesia.
How to cite: Hikmy, I. G., Sapiie, B., Rudyawan, A., Gough, A., and Webb, M.: From uplift to deposition: Tectonic controls on source-to-sink evolution during ophiolite collision in East Sulawesi. Insights from the Batui Fold-Thrust Belt, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6958, https://doi.org/10.5194/egusphere-egu26-6958, 2026.
The Sunda Shelf is the most extensive tropical epicontinental shelf and is the second largest drowned continental shelf on Earth. Unlike much of the Sunda Shelf, where stratigraphic successions have been disrupted or removed by tectonic deformation, the eastern Sunda Shelf preserves a complete Cenozoic stratigraphic archive that records the evolution of regional tectonics, sea level change, and paleoenvironmental histories. However, the basin‐scale stratigraphic architecture and their links to tectonic and sea-level fluctuation are poorly constrained in the eastern Sunda Shelf. These gaps limit our ability to evaluate the role of the Sunda Shelf in global climate and carbon-cycle regulation. In this work, we integrate extensive 2D (~8,000 km) and 3D (~4,000 km²) high resolution seismic reflection data with lithologic and age information from wells to reconstruct the tectonic and sedimentary evolution of the eastern Sunda Shelf. We identified four basin‐scale stratigraphic evolution stages: (1) tectonically controlled syn-rift stage (Late Oligocene, ~28-23 Ma), dominated by alluvial-fan and lacustrine systems that developed under rapid fault-controlled subsidence and relatively arid climatic conditions. (2) Post-rift subsidence-dominated stage (latest Oligocene to Early Miocene, ~23-17 Ma), characterized by thermal sagging and a major transition from terrestrial to shallow-marine environments. (3) Mixed tectonic-eustatic stage (Middle to Late Miocene, ~17-11.6 Ma), during which mild basin-margin uplift, inversion, and rising and falling sea level jointly influenced accommodation, sediment supply, and depositional patterns. (4) Sea-level dominated stage (Late Miocene to Quaternary, ~11.6 Ma to present), when tectonic activity waned and sedimentation became primarily governed by glacial-interglacial sea-level fluctuations, resulting in widespread shelf-edge clinoform development, channel complexes, and incised-valley systems. Our results demonstrate that the eastern Sunda Shelf underwent terrestrial-lacustrine-marine transitions with cyclical climate change, revealing how the long-term effects of Indian-Eurasian plate interactions were progressively overprinted by ice-age sea-level fluctuations. The early rift-related structural confinement, mild Middle Miocene inversion, long-term tectonic stability since the Late Miocene, and the high-frequency sea-level fluctuations since the Pliocene collectively enabled the eastern Sunda Shelf to preserve a complete tropical stratigraphic archive. This framework provides a critical geological foundation for future International Ocean Discovery Program (IODP) drilling aimed at resolving low-latitude sea-level change, tropical carbon-cycle dynamics, and hydroclimate evolution across the Sunda Shelf region.
How to cite: Wu, N.: From Tectonic Influence to Sea-Level Dominance: Cenozoic Stratigraphic Evolution of the Tropical Eastern Sunda Shelf, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2869, https://doi.org/10.5194/egusphere-egu26-2869, 2026.
