Orals: Thu, 7 May, 10:45–12:25 | Room 0.31/32
The striking contrast between deeply incised large rivers and low-relief interfluve surfaces in Southeast Tibet presents a compelling geomorphic enigma. The onset of rapid river incision in this region, inferred from low-temperature thermochronometric data, has often been interpreted as indicative of the timing of regional surface uplift; however, these findings contradict those derived from paleo-altimetric studies. The origins of the low-relief, high-elevation interfluve surfaces have likewise been the subject of prolonged debate. These controversies underscore the difficulty of unraveling the intricate relationships between drainage evolution, climate, local tectonics, and regional surface uplift in Southeast Tibet. This challenge is further complicated by the fact that most available low-temperature thermochronometric datasets are sourced from isolated transects separated by tens to hundreds of kilometers or from roadside sampling within this rugged and often inaccessible terrain. In this study, we present low-temperature thermochronometric data collected from two adjacent tributary catchments of the upper Mekong River, which provide fresh insights into the timing and mechanisms underlying river incision in this area. Thermal history modeling indicates that accelerated denudation driven by river incision began at the Oligocene-Miocene transition (22-26 Ma). This timing postdates the principal phase of Eocene regional surface uplift but coincides with an intensification of the Southeast Asian monsoon. While one tributary catchment shows relatively stable denudation rates of approximately 250 m/Myr throughout the Neogene, the neighboring catchment experienced a higher rate of about 350 m/Myr from 26 to 8 Ma, followed by a order-of-magnitude decline in denudation rate after approximately 8 Ma. This heterogeneous denudation history reflects dynamic post-orogenic drainage integration, with the decrease in denudation rate attributed to upstream tributary capture. Our findings elucidate a two-stage evolution model of drainage and topographic relief, highlighting the decoupling between surface uplift and exhumation. This model presents an alternative perspective to previous conflicting interpretations regarding the formation and dissection of low-relief surfaces in Southeast Tibet.
How to cite: Liu, J., Wang, W., van der Beek, P., Ge, Y., Oskin, M., Jiao, R., Zhang, J., Zeng, L., and Lin, X.: Surface uplift, drainage integration and river incision in SE Tibet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15834, https://doi.org/10.5194/egusphere-egu26-15834, 2026.
It has long been hypothesized that the Cenozoic climate change in Asia was primary driven by uplift of the Tibetan Plateau through increased rock weathering, although it may also result from global cooling, yet deconvolving Tibet uplift versus global climate signals is notoriously challenging. Therefore, paleoenvironmental and paleoaltimetric records with precise age constraints are essential. The Mangkang Basin from Eastern Tibet preserves continuous sediments spanning the late Eocene-Oligocene and contains abundant plant fossils which show significant climate change, providing the best archive to test the interplay between Tibet uplift and global climate change, however, remains poorly dated. In this manuscript, we precisely dated the Mangkang Basin by radiometrically anchored magnetostratigraphy. With the new age, we recalculate the paleoelevation of the Mangkang area and reconstruct the paleoclimate via plant fossils and palynologic data. Our results show that the Eastern Tibet experienced rapid uplift and has attained its current elevation, associated with significant climate cooling prior to the Eocene-Oligocene climate transition (EOT), suggesting that this cooling is mainly driven by uplift. This uplift is also temporally coincident with increased regional rainfall, increased sediment flux to the marginal seas, and an uptick in oceanic strontium isotope signatures. We conclude that the late Eocene uplift and erosion of Eastern Tibet—rather than the later Miocene Himalaya uplift or plateau-wide rise—initiated the long-term decline in atmospheric CO₂ and global cooling that ultimately culminated in the EOT.
How to cite: Li, S., Shen, Z., Liu, J., Su, T., Spicer, R., Zhou, Z., and Deng, C.: Late Eocene uplift and erosion of Eastern Tibet initiated long-term Cenozoic global cooling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18566, https://doi.org/10.5194/egusphere-egu26-18566, 2026.
The continental sea that used to extend from the Mediterranean to China, here referred to as the Eurasian Sea, fluctuated across Eurasia during the warm Paleogene times before its major retreat at the Eocene-Oligocene Transition (EOT) leaving behind the landlocked Paratethys sea. The drivers of the Eurasian sea evolution and its role on Eurasian ecosystems remain poorly understood. This lack of understanding is in large part due to the too fragmentary information currently available on Central Asian sedimentary marine and continental records, in particular in Kazakhstan where existing records remains very poorly dated and correlated. We report new chronostratigraphic data from key sedimentary marine and continental records from westernmost to easternmost Kazakhstan covering the period from the Middle Eocene Climate Optimum when the Eurasian sea reached its largest extent, until its final retreat at the Eocene-Oligocene Transition. These are combined with a compilation of paleoclimate proxies, depositional environments including palaeontological assemblages in a regional stratigraphic framework encompassing the region from the Caspian Sea to Eastern China. Initial results compared to numerical climate simulations enable to discuss potential links between sea fluctuations and geodynamic drivers, climate events, carbon sinks, basin to ocean connections, biome distributions and faunal dispersal routes.
How to cite: Dupont-Nivet, G., Jamikeshev, N., Voigt, S., Kaya, M., Nigmatova, S., Aminov, J., and Tardif, D.: Eurasian Sea fluctuations linked to Cenozoic geodynamic, climate and life; a view from marine to continental records of Kazakhstan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22163, https://doi.org/10.5194/egusphere-egu26-22163, 2026.
Changes in Indian Ocean sea surface temperature (SST) gradients play an important role in determining the strength of the South Asian summer monsoon (SASM). We show that, during a past warm climate interval—the middle Miocene—the Arabian Sea exhibited a zonal SST gradient that was reversed compared to today. Meridional SST gradients across the Indian Ocean were also greatly reduced. These patterns are not typically reproduced in Miocene climate simulations, raising the possibility that systematic regional SST biases hinder the models' ability to simulate the SASM. We assess the impact of these SST gradient changes on the SASM, by conducting three prescribed-SST experiments using early-to-middle Miocene boundary conditions along with the paleoclimate-calibrated Community Earth System Model version 2. The control experiment uses SSTs from our published coupled Miocene simulation. The second and third experiments modify Indian Ocean SSTs based on proxy-derived data from 14 to 12 million years ago. Specifically, the second simulation imposes a reversed zonal SST gradient; the third imposes warmer southern subtropical Indian Ocean SSTS, leading to reduced meridional SST gradients. The reversed zonal gradient experiment shows decreased SASM rainfall and reduced western Arabian Sea wind-driven upwelling, whereas the reduced meridional gradient experiment shows little impact on the SASM. We find that most Miocene climate simulations overestimate Indian precipitation, supporting our hypothesis that accurately simulating the reversed zonal Arabian Sea SST gradients will reduce model-data discrepancies. This study implies that these gradient changes, likely related to high‑latitude cooling in the late Middle Miocene, were an important precursor to the modern SASM. Thus, paleoclimate models may struggle to accurately simulate Miocene monsoon transitions, largely due to their persistent inability to reproduce the pattern of polar amplification characteristic of the Miocene and other warm climates.
How to cite: Liu, X. and Huber, M.: Altered Ocean Temperature Gradients Are Key to Miocene South Asian Monsoon Evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-299, https://doi.org/10.5194/egusphere-egu26-299, 2026.
Interactions between the midlatitude westerlies and the East Asian monsoon exert first-order control on hydroclimate and sediment transport across Central and East Asia, yet their long-term coupling and migration remain debated. Here we reconstruct post–Middle Miocene atmospheric dynamics and eolian source-to-sink pathways using plant-wax n-alkane hydrogen isotope ratios (δDwax) from IODP/ODP Sites U1430, 886, and 1208, spanning marginal to open-ocean depositional settings. These records are integrated with published Nd–Sr provenance constraints and regional environmental reconstructions and evaluated against simulations from the HadCM3L general circulation model.
We identify five distinct phases since ~13 Ma: (1) 13–9.6 Ma, characterized by relatively warm, stable conditions and dominant sediment input from northern Tibet and the Gobi region; (2) 9.6–6.0 Ma, marked by Late Miocene cooling, increasing Gobi contributions, and strengthening of the East Asian winter monsoon; (3) 6.0–3.6 Ma, an interval of early Pliocene warming associated with enhanced arid-interior influence and weakened monsoonal circulation; (4) 3.6–0.7 Ma, defined by a pronounced decline in δDwax, intensified Northern Hemisphere glaciation, southward migration of the westerly jet, strong winter monsoon conditions, and major erosion from the Qaidam Basin; and (5) 0.7–0 Ma, reflecting renewed dominance of arid-interior sources and reduced monsoonal influence. The results demonstrate phased migration and dynamic coupling of the westerlies and East Asian monsoon over the past ~13 Myr, driven by evolving regional topography and high-latitude glacial forcing, and highlight the utility of plant-wax n-alkanes for reconstructing long-term Asian hydroclimate and sediment source-to-sink evolution.
How to cite: Traphagan, J. and Zhuang, G.: Reconstructing Post–Middle Miocene Asian Hydroclimate and Eolian Source-to-Sink Pathways Using Plant-Wax n-Alkane δD, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7142, https://doi.org/10.5194/egusphere-egu26-7142, 2026.
The Pliocene-Pleistocene interval (5.3–0.01 Ma) is an important timeframe for understanding the interplay among tectonics, monsoon variability, and global climate transitions. Marine sediments from IODP Sites U1499A and U1501C in the northern South China Sea (NSCS) provide an excellent record for reconstructing these links. This study integrates bulk geochemistry, stable isotope, and biomarker records to determine the evolution of the Asian monsoon and its controlling mechanisms. During the Early Pliocene (~5.3-4.3 Ma), CaCO₃ concentrations were moderately low (5-12%); however, site U1501C maintained consistently higher carbonate deposition due to its outer margin high setting, which favoured carbonate preservation and reduced clastic dilution. Lower TOC (0.1-0.25%), relatively enriched δ¹³Ccarb (0.5-1.2‰) and δ¹⁸Ocarb values of -2.2 to -0.8‰, signifying warm surface waters and reduced global ice. Enriched δ¹³Ccarb further supports high marine productivity under higher sea levels. While δ¹³Corg (-24 to -26‰) and elevated C/N ratios (~10-25), CPI (~0.70-0.85) and Pr/Ph (~1.5-2.0), indicate predominantly marine organic matter (OM). Thus, δ¹³Corg, C/N, biomarker patterns, and Chemical Index Alteration (CIA) collectively indicate humid conditions with enhanced monsoon runoff. Geochemical proxies (Si/Al, Ca/Ti, Rb/Sr, Ti/Zr, Fe/K) suggest moderate to high chemical weathering, suboxic to oxic bottom-water conditions and relatively stable tectonic settings. Transitioning into the Mid-Pliocene Warm Period (MPWP) (~4.3-3.6 Ma), strengthened East Asian Summer Monsoon (EASM) activity enhanced terrigenous supply. Carbonate content remained high at U1501C, unlike U1499A, where dissolution and sea-level fluctuations reduced carbonate preservation under suboxic bottom-water conditions. Positive δ¹³Ccarb (0.3-1.5‰) and more negative δ¹⁸Ocarb (-2.4 to -1.2‰) records warm, high-productivity conditions consistent with the MPWP. δ¹³Corg (-25 to -27‰), C/N (~10-20), CPI (~0.75-0.90) and Pr/Ph (~1.2-1.8) indicate a mixed marine-terrestrial OM source owing to intensified monsoon. A slight decline in CIA (~64) and higher TOC (0.2-0.6%) signals the onset of cooler, and less humid conditions toward the late Pliocene. Between ~3.6-3.0 Ma, increased δ¹³Ccarb (0.4-1.3‰), depleted δ¹⁸Ocarb (-2.0 to -1.0‰), increased TOC (0.1-0.6%), and fluctuating CaCO₃ (5-20%) reflect a cooling trend accompanied by strengthening of the East Asian Winter Monsoon (EAWM). The δ¹⁸Ocarb enrichment marks progressive global cooling associated with early Northern Hemisphere Glaciation. Since the Early Pleistocene (~2.5 Ma), obliquity and eccentricity-driven glacial-interglacial cycles reorganised the monsoon system. Increased CaCO₃ (5-25%), enriched δ¹³Ccarb (0.5-2.2‰) and stable TOC (0.3-1.2%) reflect intensified terrestrial input during wetter interglacial phases, while δ¹⁸Ocarb values (-1.8 to -0.5‰) follow global cooling and expanding ice volume. Since ~0.8 Ma, the Himalayan-Tibetan uplift was responsible for enhanced physical erosion and reduced CIA (<28). An increased TOC (0.4-1.2%), strong carbonate preservation (15-45%) and enhanced marine productivity reflect colder glacial climates and a strengthened EAWM.
How to cite: Prabaharan, D. and Tiwari, D. M.: Climate-Tectonic Forcing of East Asian Monsoon Variability and Sedimentary Processes in the Northern South China Sea between the Pliocene–Pleistocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-922, https://doi.org/10.5194/egusphere-egu26-922, 2026.
Variations in Northern Hemisphere summer insolation are thought to drive northward expansions of the East Asian monsoon (EAM); however, the magnitude of these shifts and the monsoons' sensitivity to external forcings are poorly constrained. To evaluate the magnitude and timing of extreme northward EAM expansions, we reconstructed the lake-level history of Lake Khukh, a closed-basin lake located at 50°N in the East Mongolian Steppe. The results show that over the past 125 ka, Lake Khukh experienced pronounced highstands during northern hemisphere summer insolation maxima, indicating extreme northward incursions of the EAM into the Mongolian Steppe. The highstands are synchronous with depleted δ18O periods in the Chinese Caves record, indicating that orbital-scale northward expansions accompany EAM intensifications. We compiled lake-level data from closed-basin lakes across East Asia and compared them with the CCSM3 transient climate simulation. The results demonstrate that the model reproduces both the spatial distribution of moisture and the northern expansion of the EAM. Our results indicate that extreme shifts of the EAM into the high latitudes during insolation maxima are reliably reproduced by the CCSM3 climate simulation, thereby providing evidence of the model's skill and strengthening the fidelity of its future projections of EAM variability.
How to cite: Goldsmith, Y., Tserendash, N., Chahal, P., Porat, N., Keinan, J., Rosen, S., Brall, N., Xu, H., and Shelach-Lavi, G.: Expansion of the Asian Monsoon into the Mongolian Steppe at Insolation Maxima, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16095, https://doi.org/10.5194/egusphere-egu26-16095, 2026.
The scarcity of high-resolution paleoclimate records from the northwestern Tibetan Plateau (TP) limits our understanding the magnitude, extent, timing and drivers of the Indian Summer Monsoon (ISM) variability in this climatically sentisive region. Here we present a high-resolution sedimentary multi-proxy geochemical (Sr, Rb, Ca/Zr, Ti/Al, and TOC) lacustrine record from Lake Changmu Co over the northwestern WTP to infer monsoon changes spanning from 12 to 3.6 ka BP, when the lake has experienced highstands. Our results indicate that the lake productivity was lowered at the onset of Holocene (~12-10.5 ka BP), probably owing to relative none-influenced by ISM. However, the early Holocene climate optimum (~10.5-8 ka BP) was characterized by enhanced lake productivity and relative stable hydroclimate condition, corresponding to the strongest ISM driven by higher Northern Hemisphere summer insolation. The record further documented a pronounced dry event ~8 ka, expressed by reduced precipitation and diminished vegetation, which aligns temporally with the 8.2 ka cooling event. Since the middle Holocene, a trend toward colder and drier conditions would be linked to weakening ISM. Comparison of our record and North Atlantic climate change further revealed significant coherence within a dominant ~900-1000-year periodicity during the early to middle Holocene, suggesting persistent millennial-scale pacing of the northwestern TP hydroclimate by high-latitude climate variability. These results demonstrate that the Holocene hydroclimate evolution in the northwestern TP involved a transition from ISM-dominated humid early Holocene to Westerlies-influenced aridity late-Holocene.
How to cite: Hayat, K., Lan, J., Liu, X., Sun, Y., Wu, X., Wang, L., Pan, L., Li, H., Li, J., Cheng, P., Sarim, M., and Gan, D.: Holocene hydroclimate evolution of northwestern Tibet Plateau in response to interaction between Indian summer monsoon and mid-latitude Westerlies circulation., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3234, https://doi.org/10.5194/egusphere-egu26-3234, 2026.
The Red River Fault Zone (RRFZ) is a large-scale dextral strike-sip fault formed by the India-Eurasia collision, playing a crucial role in the tectonic evolution of the Southeastern Tibetan Plateau. As a deep-seated structure, the RRFZ acts not only as a pathway for deep material migration but also controls the geothermal activity and earthquake genesis. In this study, we utilize continuous hydrogeochemical data from eight hot springs along the fault over a two-year period to investigate the interplay between tectonic activity and fluid geochemical processes.
Isotopic signatures (δD, δ¹⁸O) identify meteoric recharge as the primary fluid source, with solute acquisition governed by water-rock interactions at depth. Hydrochemical facies analysis reveals a distinct zonation: the seismically active northern segment is characterized by Na-HCO3·SO4 waters, whereas the central-southern segments are dominated by Na-HCO3 and Na·Ca-HCO3 waters. Geothermometry estimates show that reservoir temperatures in the northern segment (308.6–329.7°C) are significantly higher than those in the central-southern segments (207.3–290.4°C). This thermal anomaly correlates spatially with the locus of maximum tectonic strain and elevated seismicity (M>5), suggesting a strong coupling between crustal deformation and deep fluid circulation.
Time-series analyses further elucidate the permeability dynamics of the fault system. Significant hydrogeochemical anomalies and shifts in estimated circulation depths were documented prior to the Myanmar and Eryuan earthquakes. Pre-seismic variations in the northern segment were dominated by Na+ and SO42− fluxes, indicative of enhanced crustal permeability facilitating the upward migration of deep-derived components. In contrast, the southern segment exhibited more pronounced responses in HCO3− . These spatio-temporal discrepancies highlight that segment-specific lithological and structural controls modulate fluid pathways and mixing processes. Our findings demonstrate that hydrogeochemical proxies are robust tools for deciphering the active tectonics of crustal-scale fault systems, offering critical insights into mass and energy transfer within the SE Tibetan orogen.
How to cite: Guo, F. and Zhou, Z.: Tectonic Controls on Hydrothermal Activity and Fluid Geochemistry along the Honghe Fault, SE Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8867, https://doi.org/10.5194/egusphere-egu26-8867, 2026.
This study examines the structural geology, uplift history, and tectonic evolution of the eastern Tibetan Plateau, a crucial natural laboratory for assessing how continents deform in response to the far-field effects of the Cenozoic India–Asia collision. Although this plateau margin is central to models of collisional orogenesis, the mechanisms and partitioning of deformation that drive uplift remain debated, in part because surface constraints have been limited by the scarcity of systematic geologic mapping—an issue underscored by recent large earthquakes that ruptured previously unmapped faults. To address these gaps, we integrate new geologic mapping across ~30,000 km² with interpretations of seismic reflection profiles to build balanced cross sections, kinematic reconstructions, and tectonic maps that quantify shortening and fault architecture in the Longmen Shan, Min Shan, and the adjacent Songpan–Ganzi terrane. These data reveal (1) pronounced along‑strike variability in the style, timing, and magnitude of shortening within the Longmen Shan; (2) a previously unrecognized, crustal‑scale tectonic wedge beneath the Min Shan that provides a viable mechanism for uplift not explained by range‑bounding structures alone; and (3) a regionally distributed conjugate strike‑slip fault system that helps accommodate and partition deformation across eastern Tibet. Together, these results are synthesized into a three-dimensional tectonic framework that links active deformation, surface uplift, and basin evolution, and they help resolve long-standing regional puzzles, including high topography despite low geodetic slip rates and limited Cenozoic foreland basin development along the plateau margin. In parallel, we combine detailed field observations with systematic low‑temperature thermochronology to reconstruct tempo-spatially variable uplift and erosion histories along the eastern plateau margin. Thermochronologic patterns indicate that the central Longmen Shan has experienced persistently rapid uplift and erosion since ca. 40 Ma, defining a NE–SW‑oriented rapid exhumation zone consistent with long‑lived, channel‑flow–influenced deformation. The northern Longmen Shan records more regional cooling compatible with fault‑controlled uplift from ca. 40-20 Ma. Since ca. 10 Ma, pronounced regional cooling in the middle segment between the Longriba and Anxian–Guanxian faults indicates episodes of accelerated uplift and denudation, whereas the northern segment shows mainly localized uplift near specific faults. Overall, the results favor a modified thrust‑dominated model incorporating wedge and duplex development, while also documenting pre‑Cenozoic shortening and along‑strike structural transitions not captured by prior end-member hypotheses. By synthesizing newly mapped and previously identified active faults, this work also improves seismic hazard characterization in a region where damaging earthquakes have repeatedly occurred on unmapped structures.
How to cite: Wu, C., Simon, A., and Li, J.: Structural geology, deformation history, and tectonic evolution of the Eastern Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2230, https://doi.org/10.5194/egusphere-egu26-2230, 2026.
How the depositional setting efficiently governs the characteristic sandwiched continental shale units remains uncertain, which restricts an integrated assessment of organic-rich fluvio-lacustrine shale reservoirs, and accurate estimation of potential natural gas resources. Here, we present new results from petrological observations, element geochemical fingerprinting, and integrated analyses of heavy mineral, basinal subsidence history, and sandstone / stratum ratio on typical and terrigenous sandwiched-like depositional systems of the targeted Upper Triassic Xujiahe Formation in the western Sichuan subsiding Bain, Southwest China. In view of the representative and environment-sensitive indices, we suggest that passive continental margin and continental island arc dominated by granite to granodiorite source are the major tectonic settings of the provenance, and both a more warm-humid climate characterized by intensified chemical weathering conditions and a calm tectonically quiescent setting are identified as two major drivers forcing the accumulation and preservation of organic matter in organic-rich continental shale units. Finally, a comprehensive depositional model is established for providing new insights into the linkage between palaeoclimatic conditions, tectonic pulses and terrigenous clastic sedimentation. Both the cyclic palaeoclimate fluctuations and episodic tectonic activities are believed to have exerted a very considerable force on development of the unique sandwiched-like stratigraphic framework, and the coupling interactions between the tectono-climatic evolution and fine-grained sedimentation are thus also stressed.
How to cite: Yang, W., Song, Y., Jiang, Z., Chen, R., and Bao, S.: Climate and tectonic-driven deposition of sandwiched continental shale units: New insights from petrology, geochemistry, and integrated provenance analyses (the western Sichuan subsiding Basin, Southwest China), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15768, https://doi.org/10.5194/egusphere-egu26-15768, 2026.
The past decades have been rich in field-based discoveries, substantially expanding both the range and resolution of geological records documenting Cenozoic Asian tectonic evolution, climate, and landscapes. Geological evidence from sedimentary, fluvial, lacustrine, and paleobotanical archives indicates that monsoon-like precipitation seasonality was likely already established during the Paleogene greenhouse period, thereby challenging the traditional view of monsoon climate emergence. Syntheses of these proxy records, combined with paleoclimate simulations spanning 40-8 Ma and testing a range of paleogeographic configurations, have enabled the evaluation of multiple working hypotheses and provided new perspectives on the drivers of South and East Asian monsoon onset. Model results suggest that summer and winter monsoons may have evolved diachronously in response to distinct forcings, and highlight the importance of paleogeographic evolution in shaping Asian climate. Increasing continentality, due to sea level drop, the retreat of the Paratethys Sea and the emergence of the Arabian Plate, appears to have enhanced summer ITCZ migration, while East African, Anatolian-Iranian, and Tibetan-Himalayan landforms contribute to the channelling of these moisture-laden winds toward Southeast Asia. In contrast, by blocking and deflecting westerly fluxes northward, the uplift of the Tian Shan-Pamir ranges and the Mongolian Plateau likely contributed to strengthening the winter monsoon. Together, these results highlight the need for integrated multi-proxy and modeling approaches to robustly constrain the timing and drivers of Asian monsoon establishment.
How to cite: Tardif, D., Sarr, A.-C., Fluteau, F., Licht, A., Kaya, M., Ladant, J.-B., Meijer, N., Donnadieu, Y., Dupont-Nivet, G., Bolton, C. T., Le Hir, G., Pillot, Q., Poblete, F., Sepulchre, P., and Toumoulin, A.: Towards a better understanding of the impact of topography evolution on Asian climate over the past 50 Ma, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15129, https://doi.org/10.5194/egusphere-egu26-15129, 2026.
In the present-day context, South Asian monsoon has a characteristic core monsoon zone that is defined to lie along the NW Indian subcontinent and Indo-Gangetic Plain while the fringe monsoon zone lies in the NW Indian subcontinent. The spatial divergence of monsoon evolution in these regions is currently understudied. Our work is aimed at investigating the development of South Asian monsoon in these regions during the Miocene. We analyzed the variation in clay mineral assemblages and major element composition as weathering proxies together with grain size distribution to create a continental chemical weathering record from two Ocean Drilling Program (ODP) sites, ODP Site 717 in the distal Bengal Fan and ODP Site 730 in the western Arabian Sea. Our results indicate that at ODP Site 730 the chemical index of alteration (CIA) values range between 40 to 60 and at ODP Site 717 they range between 60 to 70, suggesting that overall chemical alteration is higher in NE Indian subcontinent. At ODP Site 730, between 14.5 Ma and 9.5 Ma there is a decreasing trend in CIA values. Similarly a trend of decreasing smectite/ illite+chlorite values is observed during this period which indicates a reduced seasonality effect. This suggests that in the NW Indian subcontinent at the end of Mid-Miocene Climatic Optimum (MMCO), monsoon was stronger and had significant seasonal variations. As cooling progressed, the monsoon became weaker and more tropical. Since 9.5 Ma, this weak, tropical monsoon has persisted in the region. At ODP site 717, from 9 Ma to 7 Ma, smectite/illite+chlorite values are close to zero and CIA values are between 60 and 65, implying that the monsoon precipitation was not very seasonal yet wetter causing significant chemical alteration in the northeastern Indian subcontinent. However, after 7 Ma, the CIA values show large fluctuations at a sub-million year timescale and smectite production rises significantly suggesting a transition to more seasonal monsoon. The results demonstrate that during the late Miocene, a distinct development of South Asian monsoon is seen in these two regions where the NW region became arid and experienced less seasonal variability in rainfall intensity and the NE region that transitioned from tropical wet monsoon to more seasonal precipitation with variability in monsoon strength. Our study provides a systematic understanding of variability within the South Asian monsoon system and is useful for assessing other paleoenvironment proxies from the region.
How to cite: Sardar, S., Clift, P., and Zhuang, G.: Distinct development of South Asian monsoon in the northwestern and the north-northeastern Indian subcontinent since the Miocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14825, https://doi.org/10.5194/egusphere-egu26-14825, 2026.
As the largest elevated plateau on Earth, the Tibetan Plateau has played a pivotal role in shaping both global and regional climate as well as mammalian dispersal. Yet how paleoclimate and biome shift in and around the Plateau responded to Plio–Pleistocene cooling, marked by a ~3–4 °C global temperature drop at ~2.7 million years ago (Ma) and the intensification of Northern Hemisphere glaciation, remains to be further investigated. Here we integrate novel climate and biome simulations with new carbonate stable and dual clumped isotope analyses to reconstruct past climate and ecosystems across the Tibetan Plateau and its surroundings. Our clumped-isotope temperatures indicate warmer mean annual air temperatures prior to 2.7 Ma, supporting a permafrost-free northern Plateau under climates warmer than today. Combined with climate modeling and global permafrost distribution, these results suggest that under conditions similar to the mid-Pliocene Warm Period (3.3–3.0 Ma), ~60% of alpine permafrost, containing ~85 petagrams of carbon—may have been vulnerable to thaw, compared to only ~20% of circumarctic permafrost. This implies that up to ~25% of global permafrost carbon, and associated permafrost–climate feedbacks, could originate in alpine regions. In addition, our results show the emergence of cold steppe–tundra habitats suitable for woolly rhinoceroses during Plio–Pleistocene cooling, forming plateau–circumarctic dispersal corridors. The ~3–4 °C cooling around 3.0–2.7 Ma along these corridors coincided with ~8 °C cooling on the Plateau. A >30% decline in plateau habitat suitability, alongside a ~23-fold corridor expansion, points to temperature decline as the primary driver of poleward megafaunal dispersal. Taken together, our findings highlight the amplified temperature sensitivity of high-elevation regions and underscore the central role of global temperature change in shaping the past, present, and future dynamics of cold-adapted mammals across the cryosphere.
How to cite: Cheng, F., Mulch, A., Xiao, W., Meijer, N., Haywood, A., Wang, L., Li, X., Tindall, J., Garzione, C., Fiebig, J., Zuza, A., Hill, D., Dolan, A., Hunter, S., Dupont-Nivet, G., Jolivet, M., Bernecker, M., Salzmann, U., Lu, H., and Nie, J.: Plio–Pleistocene Paleoclimate Insights into Alpine Permafrost Stability and Ice-Age Megafaunal Dispersal in Asia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21415, https://doi.org/10.5194/egusphere-egu26-21415, 2026.
This study assesses near-future extreme climate change in East Asia using ERA5, GSOD, and 35 CMIP6 models under SSP245 and SSP585 for 1995–2050. Results show that although recent warming is strongest in the Arctic, East Asia will experience more rapid annual and seasonal warming than both the Arctic and mid-latitudes by 2050, especially under SSP585. An energy-budget analysis attributes this enhanced warming to increased net surface radiation driven by reduced clouds and aerosols, higher SSTs, and greenhouse-gas forcing, with latent and sensible heat fluxes modulating but not offsetting the warming. Observations combined with Niño 3.4 and AO indices reveal that El Niño strongly amplifies summer heat waves, while persistent La Niña and negative AO phases intensify winter cold waves in continental East Asia. These findings highlight East Asia as a hotspot of extreme regional amplification, where anthropogenic forcing and large-scale internal variability jointly increase the risk of severe heat and cold extremes in the near future.
Acknowledgment: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) [RS–2025-24683148].
How to cite: Zo, I.-S., Lee, K., and Jo, E.-S.: Near-future Climate Change in East Asia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1343, https://doi.org/10.5194/egusphere-egu26-1343, 2026.
The Central Ganga Plain hosts many lakes that serve as archives for high-resolution palaeoclimatic reconstruction. However, climate cycles on millennial and shorter timescales remain poorly constrained in terrestrial records from the Indian subcontinent, especially in the wetlands of the CGP. Some previous research on these lakes has examined the regional Holocene climate variability, but these studies have been limited by the scarcity of high-resolution data. To better understand local and regional climate forcings and identify the main driver(s) of past C3/C4 vegetation shifts, Kanwar Wetland in the Central Ganga Plain was studied using various proxies, including mineral magnetism, sediment textural parameters, and stable carbon isotope (δ13C values), with chronological control provided by six AMS 14C ages. A ~3-meter-long sediment core retrieved from the Kanwar wetland allows for reconstructing millennial-scale climate variations over the past 15,000 cal yrs BP. The record reveals significant palaeoclimatic events, including the Bølling–Allerød (B/A), Younger Dryas, and shorter Holocene fluctuations. The B/A period aligns with a phase of strengthened Indian Summer Monsoon (ISM) over the CGP. Furthermore, the prolonged periods of weaker monsoon are evident in the Holocene, mainly around 10600, 8200, 6000, 4200, 2800, and between 1400 and 600 cal yrs BP. These episodes temporally coincide with reduced upwelling intensity in the western Arabian Sea, suggesting weaker ISM winds. Superimposed on these trends are notable short-term cycles of roughly 172–344 and 172–688 years around 12,000 and 14,000 cal yrs BP, as well as 86–344‑year cycles between 2,000 and 6,000 cal yrs BP, which suggest a significant role of external forcing, especially solar variability. A ~1,492‑year ISM cycle during the Holocene is also observed in this record, which is speculated to be linked to combined external (solar) and internal (AMOC) forcings. Comparisons with marine, ice-core, and other published records from the Central Ganga Plain reveal both consistencies and differences in millennial‑scale climate signals, underscoring the strong ocean–atmosphere influence on the ISM. The reconstructed monsoon–vegetation coupling indicates that shifts in the relative abundance of C3 and C4 plants were predominantly governed by changes in ISM intensity. For much of the record, C3 and mixed C3–C4 vegetation dominated in the CGP, followed by a shift to C4-dominated vegetation in the late Holocene (Meghalayan stage).
How to cite: tiwari, A., phartiyal, B., kawsar, M., m c, M., agrawal, S., and sharma, A.: Coupled Climate–Vegetation Dynamics over the last 15 ka in the Central Ganga Plain: A Multi‑Proxy Record from Kanwar Wetland, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16361, https://doi.org/10.5194/egusphere-egu26-16361, 2026.
Posters virtual: Fri, 8 May, 14:00–18:00 | vPoster spot 4
EGU26-1046 | ECS | Posters virtual | VPS7
Multi-Proxy Reconstruction of Late Quaternary Monsoon Variability and Fluvial Response in the Central Ganga Plain, India: Insights from magnetic, CHNS and geochemistry records.Fri, 08 May, 15:15–15:18 (CEST) vPoster spot 4
The Central Ganga Plain (CGP), a key sector of the Indo-Gangetic foreland basin, contains thick, continuous Quaternary alluvial sequences. Its rapidly subsiding basins preserve a high-resolution terrestrial archive, ideal for reconstructing Indian Summer Monsoon (ISM). This study examines sedimentary profiles from distinct river systems in the Central Ganga Plain (CGP) using a multi-proxy framework. A Late Quaternary trench from the Gomti river (26°52′ N, 80°56′ E, Lucknow) and a Holocene section from the Betwa river (25°28′ N, 79°5′ E, Hamirpur). Sediment sample from Lucknow profile were analysed for CHNS, AMS ¹⁴C dating, mineral magnetism, and bulk geochemistry (major, trace, and REE), while those from Hamirpur were analysed using OSL and AMS ¹⁴C dating, alongside CHNS. The established chronology or Lucknow trench, record from ~24 to 3 kyr BP. The CHNS data shows a significant shift at ~20 kyr, marked by high TOC (3.97%) and C/S ratio (~ 300) indicating enhanced organic productivity and freshwater conditions. Concurrent mineral magnetic signatures (χlf, SIRM and ꭓARM) suggest strong detrital input linked to weaker monsoon. This evolving climatic condition is further investigated through bulk geochemistry, (major, trace and REE), which provide critical insights into sediment provenance, weathering regimes, and paleo-hydrological conditions. The chronology for the Hamirpur trench covers from ~800-12000 years BP and the CHNS data provide distinct environmental phases, marked by a sharp peak in TC (3.31%), TOC (1.56%) and C/N ratio (~439), indicating a enhanced terrestrial organic matter preservation in a low-energy, waterlogged setting around ~3000 kyr BP. This integrated high-resolution multiproxy record from the two distinct river systems provides new insights into monsoon variability and sedimentary responses in the Central Ganga Plain during the late Quaternary.
How to cite: Jayakumar, J., ms, A., phartiyal, B., sharma, A., Kumar, P., D. Chauhan, G., and kannan, P.: Multi-Proxy Reconstruction of Late Quaternary Monsoon Variability and Fluvial Response in the Central Ganga Plain, India: Insights from magnetic, CHNS and geochemistry records., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1046, https://doi.org/10.5194/egusphere-egu26-1046, 2026.
