Central Nepal is a key natural laboratory for investigating crustal kinematics, exhumation, and thermochronometric records within a critically tapered orogenic wedge. In the High Himalayas, thermochronologic data record remarkably young cooling ages and rapid late Cenozoic exhumation rates, yet the kinematics driving these patterns remain actively debated. Most models aiming to explain the physiographic transition across the Himalayan range propose either predominantly in-sequence deformation focussed on the Main Himalayan Thrust (MHT), with underplating and the growth of a Lesser Himalayan duplex, or significant out-of-sequence (OOS) faulting in the Main Central Thrust (MCT) zone. Existing thermochronometric datasets allow for both end-member interpretations, highlighting the non-uniqueness of steady-state kinematic models based on traditional thermochronometers alone.

We address this issue by adding trapped-charge thermochronometers (luminescence and ESR thermochronometry), which, owing to their extremely low effective closure temperatures, are uniquely sensitive to <1–2 Myr transients in near‑surface thermal histories. These data provide unprecedented sensitivity to short-lived Quaternary pulses of exhumation, potentially associated with OOS fault reactivation. We present new luminescence and ESR thermochronometry data from bedrock samples collected across the four major valleys of the Narayani basin in central Nepal (from west to east: Kali Gandaki, Marsyangdi, Buri Gandaki, and Trisuli), spanning the MCT zone and the High Himalayan range.

Using the thermo-kinematic code PECUBE, we invert this multi-system thermochronometer dataset (including both traditional and trapped-charge thermochronometers) through neighbourhood-algorithm exploration of fault slip rates and activity timing. We test three kinematic scenarios: (i) purely steady-state, ramp-focused uplift along the MHT; (ii) stepwise acceleration linked to mid-crustal duplex initiation at ~10 Ma; and (iii) short-lived Quaternary pulses of exhumation associated with transient MCT reactivation superimposed on long-term MHT-driven uplift.

Our inversion results show that trapped-charge thermochronometers require transient Quaternary uplift pulses in the High Himalayas to reproduce the observed cooling patterns. We quantify the timing, magnitude, and spatial distribution of OOS slip, revealing lateral variations in reactivation activity among the four valleys and testing their correlation with variations in MHT coupling and orographic precipitation patterns. Overall, our results provide quantitative bounds on the timing, magnitude, and spatial variability of Quaternary uplift transients in the High Himalayas, and demonstrate that transient MCT reactivation is required to reconcile thermochronologic data with topography and structural constraints, refining the late Cenozoic kinematic evolution of the MHT–MCT system.

How to cite: Bouscary, C., Braun, J., Grujic, D., Lavé, J., Hetényi, G., Herman, F., King, G. E., Tsukamoto, S., and Gajurel, A. P.: Transient Quaternary fault activity in Central Nepal, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12643, https://doi.org/10.5194/egusphere-egu26-12643, 2026.

The arcuate tectonic belt at the northeastern margin of the Qinghai-Tibet Plateau is located at the farthest northern and eastern extension of the plateau, situated at the junction of the Qinghai-Tibet Block, the North China Craton, and the Alxa Block. This arcuate tectonic belt consists of four arcuate faults—the Haiyuan–Liupanshan Fault, the Xiangshan–Tianjingshan Fault, the Yantongsan Fault, and the Luoshan–Niushou Mountain Fault—along with the Cenozoic sedimentary basins sandwiched between them. While significant progress has been made in studies of its tectonic analysis and thermochronology, debates persist regarding the uplift and extension processes during the Paleogene to Neogene. This study focuses on three key sections: the Longde Section west of the Haiyuan Fault in the rear of the arcuate belt, the Sikouzi Section east of the Haiyuan Fault, and the Daruoshan West borehole section at the front of the arcuate belt. These sections, particularly the Sikouzi Section, exhibit well-preserved Cenozoic strata, making them critical for studying late Cenozoic sedimentary-tectonic evolution. Based on field surveys of geological sections, sedimentary structure observations, and stratigraphic division, this research employs experimental methods such as heavy and light mineral composition analysis, detrital zircon U-Pb geochronology, and carbon-oxygen isotope analysis to conduct systematic source-to-sink system studies. By examining sedimentary records in response to the tectonic evolution of adjacent orogenic belts, the study systematically reconstructs the late Cenozoic uplift and extension processes of the arcuate tectonic belt in the northeastern Qinghai-Tibet Plateau, delineates the initiation, development, and termination timelines of intense uplift and extension, and explores the uplift-extension model and its extent. Key findings include: During the deposition of the Sikouzi Formation (Paleogene), the northeastern uplift and extension of the Qinghai-Tibet Plateau only affected areas west of Liupanshan; by the end of the Qingshuiying Formation deposition (~17.8 Ma), the northward and eastward thrusting of the plateau began influencing areas east of Liupanshan; at the onset of the Ganhegou Formation deposition (~8 Ma), the northeastern margin of the plateau entered a phase of rapid uplift and extension; during the middle phase of Ganhegou Formation deposition (~5.0 Ma), the arcuate tectonic belt experienced intense uplift; and by the end of the Ganhegou Formation deposition (~2.5 Ma), the arcuate tectonic belt reached its peak uplift stage.

How to cite: Kou, L.: The late Cenozoic uplift of arcuate tectonic belt, northeastern margin of the Tibetan Plateau, based on the sedimentary restriction of the important geological section, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9979, https://doi.org/10.5194/egusphere-egu26-9979, 2026.

The north-eastern Himalaya display an early stage of tectonism since the disintegration of Gondwanaland. The Kameng watershed, situated in the westernmost part of the Arunachal Himalayas, represents a critical zone of active tectonic deformation. Its significance arises from its position at the triple junction of three major seismo-tectonic domains: the Eastern Himalayan Collision Zone (EHCZ) to the north, the Plate Boundary Zone of the Shillong Plateau Assam Valley Bengal Basin (PBZSPAVBB) to the southwest, and the Assam Gap (AG) to the southeast. Additionaly the region is traversed by four major fault and detachment systems: Main Frontal Thrust (MFT), Main Boundary Thrust (MBT), Main Central Thrust (MCT), and South Tibetan Detachment System (STDS) from south to north. Such geodynamic settings are expected to leave imprints on the spatial variability of tectonic activity across the region, making this an important aspect to investigate in understanding the differential tectonic response of the Kameng watershed. Concentrated earthquake events in the northwestern part of the watershed and a sudden debris flow in the recent past in Wapra-bung, a tributary located in the vicinity of the same region, drew significant attention and led to the hypothesis of a potential link among the ongoing stress accommodation along the older thrust and detachment systems (MCT and STDS) in the hinterland, the debris flow in the northwestern segment, and the concentrated distribution of seismic events in the northwest region of the Kameng watershed. Relative and Total Slope-extension Index (RDEs/RDEt), the Stream Length Gradient–Hotspot and Cluster Analysis (SL-HCA) using the Getis-Ord Gi statistic, Relative Tectonic Uplift (Ut) of the sub-watersheds, along with seismological analysis using the Gutenberg–Richter relationship, were conducted on seventeen sub-watersheds of the Kameng watershed to evaluate tectonic deformation within the region. Findings suggest that the heightened tectonic activity in the northwestern region is not coincidental but is likely linked to the Radial Expansion and the Oblique Convergence Model, with ongoing stress accommodation along the STDS and MCT in the hinterland. In contrast, the eastern side of the Kameng watershed exhibits lower seismic activity and reduced tectonic instability, possibly associated with the Assam Gap, where the stress release rate is relatively low compared to the Eastern Himalayan Collision Zone to the north and the Shillong Plateau to the southwest. In Arunachal Himalaya, approximately 6 mm/yr of total ~15 mm/yr plate convergence is being absorbed between Bomdila and Tezpur in the Lesser/Outer Himalaya; this fact could be the explanation of the heightened tectonic activities. In comparison, about 10 mm/yr is taken up between Bomdila and Tawang in the Greater/Tethyan Himalaya. Field evidence, including a 39°C hot water spring near Dirang along the Bichom River, further supports the inference of active deformation within the north-western side of the watershed.

How to cite: Das, S. and Biswas, M.: Active Tectonic Deformation of the Kameng watershed: Evidence from Geomorphic Indices and Seismological Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-725, https://doi.org/10.5194/egusphere-egu26-725, 2026.

Forebulge uplift plays a significant role in foreland-basin evolution; however, uplift history and stratigraphic expression are often difficult to resolve within continental interiors, where deformation is subtle and typically modelled over million-year timescales. A key question that remains unresolved is how slow forebulge uplift manifests itself in sedimentary facies architecture and geomorphic response at shorter (kiloyear) timescales.

Chambal River Basin, the largest cratonic tributary of the Ganga River and forming the western extent of the Southern Ganga Plains (SGP) in the Himalayan Foreland is characterized by extensive badland development that has resulted in exceptional sedimentary sections that preserve signatures of coupled forebulge dynamics and climatic fluctuations.

Through integrated sedimentary facies analysis and optically stimulated luminescence (OSL) dating, we identify a basin-wide stratigraphic framework comprising a laterally extensive paleosol/interfluve unit (~113 ka), overlain by channel deposits (60–40 ka), and capped by Holocene floodplain sediments (~7 ka). The spatial extent and age equivalence of the basal paleosols correlated with regional records from Kalpi (~119 ka), Dahelkhand (~120 ka), and Ganga–Yamuna interfluve boreholes indicate a region-wide phase of landscape stability during MIS-5. While younger incision–aggradation cycles are linked to late Quaternary climatic fluctuations, the lateral continuity, maturity, and thickness of the MIS-5 paleosols point to prolonged landscape stability and fluvial incision, which we interpret as the geomorphic response to Central Indian Forebulge (CIF) uplift.

Our results demonstrate that even low-magnitude forebulge movements can manifest in sediment routing, modulate base levels, and generate regionally consistent pedogenic surfaces over shorter timescales. These findings highlight the sensitivity of craton-draining rivers to subtle flexural forcing.

How to cite: Kasana, P., Singh, V., Tandon, S. K., Kumar, R., and Devrani, R.: Evidence of Forebulge Uplift in Late Quaternary Stratigraphy of the Southern Ganga Plains: Insights from the Chambal Basin, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-994, https://doi.org/10.5194/egusphere-egu26-994, 2026.

In response to the Indo-Asian collision, the eastward growth of Tibetan Plateau results into an extensive low-relief surface in the Yunnan-Guizhou area, i.e., the Yungui Plateau. Of which the paradoxical presence of extensive low-relief surface perched above deep valleys in the southeast Tibet Plateau is a long-standing challenge. Here, we apply 36 samples detrital zircon and apatite thermochronometry along the Yangtze and Nanpanjiang rivers, to provide the reginal-scale proxy for the unroofing and uplift history of the Yungui Plateau. The detrital zircon fission track data range in age from Permian to Cretaceous, with major peak-ages at 200 Ma, 160 Ma, 140 Ma, and 120 Ma along different rivers, indicating of a single phase of westwards unroofing along the Yungui Plateau occurred in ca. 160-120 Ma. Furthermore, detrital apatite fission track data shows major peak-ages at 60 Ma, 40 Ma and 20 Ma, with ages of various from 100~10 Ma. In particular, detrital apatite (U-Th)/He data shows major peak-ages around 10 Ma along the Xianshuihe-Xiaojiang area, with regional erosion more than 1500 m. The results confirm overall southwards unroofing process occurred in Late Cenozoic, from southeast margin of the Tibetan Plateau to the Yungui Plateau interiors. Thus, the Yungui Plateau surface uplift and incision result from two processes, expanding the Eastern Tibetan Plateau into its low-relief high-elevation surface along the Yungui Plateau. 

How to cite: Deng, B., Ye, Y., Zhang, Y., Zhao, G., and Liu, S.: Unroofing and uplift history of the Yungui Plateau at SE Tibetan Plateau, evidence from detrital zircon and apatite thermochronometry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6059, https://doi.org/10.5194/egusphere-egu26-6059, 2026.

The Cordillera Blanca Batholith (CBB) is a >160 km long, NW-oriented granodioritic body intruded along the western half of the Marañón fold-and-thrust belt (MFTB) in the Central Andes of northern Perú. This segment of the Andean orogen is characterized by a flat-slab, highly coupled, subduction zone controlled by the collision of the Nazca ridge since mid-Miocene times. The available U-Pb and Ar-Ar crystallization ages, in zircon and hornblende/biotite, respectively, indicate that the emplacement of the CBB took place between 4-8 Ma. Moreover, paleo-barometric studies in amphibole samples indicate emplacement depths ranging from 3.5 to 7 km, below the paleosurface of the MFTB. A major west-dipping, high-angle fault scarp that bounds the western side of the CBB has been used to support the interpretation of normal faulting (e.g., core-complex style) as the main tectonic driver for the 1.75-2.5 mm/a exhumation rates calculated from low-temperature (FT and U-Th/He in zircon and apatite) thermochronological modeling.

Recent field campaigns have demonstrated that normal faulting is confined to the boundary between the CBB and the Santa river valley, with no evidence of widespread associated extensional features throughout the region. Furthermore, the uppermost stratum of the CBB systematically corresponds to the regional décollement level of the MFTB (hornfelsed Jurassic mudstones), suggesting that the emplacement occurred at the interface between the MFTB and the regional basement. Furthermore, detailed kinematic analyses of the mylonitized contact of the granodioritic body reveal low-angle and normal sense of shearing towards SW and NE along the western and eastern margins of the CBB, respectively. New U-Th/He thermochronological dating in zircon (ZHe) of samples retrieved from complementary sectors of the CBB, but focusing on its less studied eastern sector, have been obtained showing cooling ages roughly ranging between 3-5 Ma. Remarkably, cooling of both sides of the CBB occurred almost synchronously, being just 1-1.5 Ma older on the eastern side.

Several thermo-kinematic scenarios for a segment in the central part of the CBB have been modeled with Pecube by combining the obtained ages with twelve available AFT ages from the literature. While the simplest, low-angle, normal faulting model fits better the obtained ages, it fails to explain the field observations and implies fault displacement of more than 12 km that would necessarily require development of widespread extensional features. A series of alternative models implying contractional tectonics (e.g., deep-seated, blind thrusting of the basement) aiming to explain both structural data and cooling ages are presented for discussion in this contribution.

How to cite: Garcia, V. H., Medina Córdova, M., Wapenhans, I., and van der Beek, P.: Exhumation of the Cordillera Blanca Batholith (Perú). New insights from thermo-kinematic modeling., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16999, https://doi.org/10.5194/egusphere-egu26-16999, 2026.

The Congo River system, located in Central Africa, drains a basin exceeding 3.5 million km² and with a course up to 4,000 km, ranking it among the world’s largest rivers. It spans from the western edge of the East African Rift to its offshore deep-sea fan which associated with oil and gas resources. This vast system is characterized by a high sediment load, positioning the Congo as the second-largest contributor to modern continent-to-ocean sediment flux, after the Amazon River. These observations raise several interconnected questions: i) what are the origin of this sediment? ii) does this high sediment load reflect a high erosion rate? (iii) how has this flux evolved throughout the Congo River’s history?

Moreover, the Congo River sediments– have recorded the vertical dynamics of the corresponding area (i.e. Central African Plate) which remain poorly constrained, except along the rift margins. These sedimentary archives have also recorded how Central Africa’s erosional dynamics have evolved over the past, and whether it has been impacted by climatic or tectonic changes. 

Applying a source-to-sink approach to the Congo River sediments may therefore provide critical information and data to better understand the dynamics and history of one of the world largest sedimentary systems of the world and help to better understand the uplift and erosional evolution of this vast region.

Recent studies have employed conventional source-to-sink methods (e.g., heavy mineral analysis and U-Pb zircon dating) on modern Congo sediments (Garzanti et al., 2021, 2019). However, these approaches faced challenges due to the homogeneity of source signals, particularly in the Cuvette Centrale and surrounding basement outcrops, which exhibit similar geochronological signatures. To overcome this limitation, we apply a recent method: double dating of zircons ((U-Th)/He and U-Pb) combine with REE determination. Applied to both modern and ancient sediments (up to 50 Ma), this technique enables more precise source reconstruction. We will present the newly generated results and discuss their implications for the Congo River’s sedimentary history and the broader understanding of Central Africa’s geological evolution.

Garzanti, E., Bayon, G., Dennielou, B., Barbarano, M., Limonta, M., Vezzoli, G., 2021. The Congo deep-sea fan: Mineralogical, REE, and Nd-isotope variability in quartzose passive-margin sand. Journal of Sedimentary Research 91, 433–450. https://doi.org/10.2110/jsr.2020.100

Garzanti, E., Vermeesch, P., Vezzoli, G., Andò, S., Botti, E., Limonta, M., Dinis, P., Hahn, A., Baudet, D., De Grave, J., Yaya, N.K., 2019. Congo River sand and the equatorial quartz factory. Earth-Science Reviews 197, 102918. https://doi.org/10.1016/j.earscirev.2019.102918

How to cite: Charreau, J., Derycke, A., Pik, R., Dall’Asta, M., and Garzanti, E.: Tracing the sedimentary provenance of the Congo River: A source-to-sink approach using double zircon dating ((U-Th)/He & U-Pb), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18941, https://doi.org/10.5194/egusphere-egu26-18941, 2026.

Constraints on vertical motions in subduction forearcs can improve understanding of the complex processes that govern the development and evolution of these subduction zones, particularly deep-earth processes that are difficult to directly observe. The Calabria region provides an exceptional natural laboratory for investigating the interplay between mantle dynamics, slab break-off, and forearc rock uplift. Previous geophysical studies show slab tears to the north and south of the ~200 km wide subducting Ionian slab, and the Calabrian forearc archives a history of rock uplift in well-preserved marine terraces. However, despite numerous studies on extensive sequences of deformed marine terraces across the region, the temporal and spatial variability of uplift rates, and their relationship to slab geometry, remain poorly constrained. Complications in using Calabrian terraces to understand the surface response to slab tearing and other subduction processes arise from (1) cross-cutting faults and augment the deeper earth signal of rock uplift, (2) preservation issues due to denudation of terrace sequences, and (3) sparse geochronology. Here, we overcome these challenges using detailed mapping, stratigraphic descriptions, and dating of marine terrace sequences along Calabria’s Ionian Coast, where few active surface-breaking events affect marine terraces, making it the location to image hypothesized signals of rock uplift due to slab tearing and mantle geodynamics. By targeting this tectonic setting, we aim to better resolve spatial variations in uplift rates across the entire plate boundary from slab edge to slab edge and beyond, across a transect extending >300 km. Within this area, 12 samples were collected: one for detrital sanidine ⁴⁰Ar/³⁹Ar dating and 11 for luminescence dating. Preliminary age control and correlations to a sea level curve indicate long-wavelength (100s of km) deformation of marine terraces. Marine terrace-derived rock uplift rates increase southward toward the Strait of Messina, reaching ~1.3 mm/yr near the Strait of Messina above the southern slab tear, decline to ~0.8 mm/yr above the subducting slab, and increase to ~2 mm/yr above the northern tear north of the Sila Massif. We are currently analyzing temporal changes in rock uplift rates over the past 200-500 kyr, as afforded by the terrace record, to assess changes in slab tear and subduction dynamics during the mid-to-late Quaternary. These results suggest the fingerprint of slab tearing is imprinted on the coastal geomorphology of the Calabria forearc and highlight the critical importance of geomorphology in aiding in studies of subduction zone geodynamics.

How to cite: Perez-Hincapie, A. and Gallen, S.: Long-Wavelength Quaternary Forearc Deformation Recorded by Marine Terraces in the Calabrian Arc, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6081, https://doi.org/10.5194/egusphere-egu26-6081, 2026.

Coral reef–mangrove systems record the coupled effects of relative sea-level change, sediment supply, and coastal surface processes, yet their long-term interactions remain poorly constrained. Here, we reconstruct the Holocene evolution of a reef–mangrove system on Belitung Island (Indonesia) by integrating sedimentary archives, geochronology, paleo–sea-level indicators, and numerical modeling. We document regressive coastal stratigraphy exposed in a drained tin mine and analyze a suite of ~3 m sediment cores collected along a nearshore-to-onshore transect. Radiocarbon dating of corals indicates nearshore reef initiation at ~2 m below present mean sea level between ~6.1 and 5.7 ka BP, followed by vertical reef accretion until ~4.3–3.8 ka BP. Fossil oysters provide independent paleo–sea-level constraints, recording a prolonged mid-Holocene relative sea-level highstand (~6.5–4 ka) at ~3 m elevation, followed by a relatively abrupt ~2 m fall and subsequent smaller-amplitude fluctuations. Optical stimulated luminescence (OSL) dating shows that mangrove colonization and terrestrial sedimentation initiated during Late Holocene shoreline progradation. We combine the coral radiocarbon and mangrove OSL ages within a Bayesian inversion framework coupled to a reef-growth model to reconstruct system evolution. We use model results to compare fluctuating mid-to-late Holocene relative sea-level scenarios with single-peaked highstand, and their respective effects on reef/mangrove architecture. These findings highlight how geological inheritance and non-monotonic boundary conditions govern sedimentary and ecological responses in tropical coastal systems, with implications for anticipating future landscape responses to sea-level change on the regional scale.

How to cite: de Gelder, G., Solihuddin, T., Utami, D. A., Sidik, F., Rachmayani, R., Hendrizan, M., Cahyarini, S. Y., Purnama, M. R., Erkan, D., Boucharat, Y., Widiawaty, M., Elliot, M., and Husson, L.: Geological inheritance controls reef–mangrove responses to Holocene sea-level change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14735, https://doi.org/10.5194/egusphere-egu26-14735, 2026.

Active fault influence landscape through both tectonic deformation and surface erosion. Although their role in generating rock uplift is well established, the global impact of fault-related rock damage on erosional efficiency remains poorly constrained. Using a compilation of 1,744 cosmogenic 10Be–derived erosion rates, we demonstrate that erosional efficiency is systematically enhanced within approximately 15 km of mapped fault traces and declines with increasing distance, following an inverse sigmoidal trend extending to roughly 100 km. The strongest responses are associated with reverse faults and faults exceeding 140 km in length. The observed decay length scale implies that tectonic damage extends well beyond fault-core pulverization, potentially reflecting grain-scale weakening, increased fracture density from seismic shaking, and distributed deformation within complex fault networks. Machine-learning analyses identify proximity to faults as a primary control on erosional efficiency, surpassing the influence of precipitation and lithology, with model performance further improved by incorporating metrics of seismic shaking. Together, these results indicate that active tectonics modulate erosion not only through uplift but also by enhancing erosional efficiency via widespread rock damage.

How to cite: Kuhasubpasin, B., Moon, S., and Lithgow-Bertelloni, C.: Global Influence of Tectonic Rock Damage on Erosional Efficiency, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1546, https://doi.org/10.5194/egusphere-egu26-1546, 2026.

The songs of the majestic landscapes are composed by the symphony of tectonic, climatic, and lithologic processes. For tectonically quiescent landscapes, landscape dynamics can be complicated by the tension between fluvial and glacial erosion and composite lithologic erodibility contrasts. We investigate these complications by focusing our study on the Southern Canadian Rocky Mountains, a late-stage tectonic fold and thrust belt with spatially uniform climate. These ranges comprise deformed carbonate and mixed carbonate-siliciclastic rock sequences. They have also experienced extensive glacial sculpting evidenced by steepened river valley walls and U-shaped channels. To address these complications, we produce the first basin average erosion rates, derived from 36Cl-cosmogenic isotopes, for 22 catchments across the Rockies. We then compare these erosion rates with climate, topographic, and litho-structural factors using bivariate and multivariate Bayesian regression modelling to infer the dominant controls of the landscape evolution of the Rockies. We begin our analysis with the common factors used in landscape evolution studies such as mean annual temperature (MAT), mean annual precipitation (MAP), normalised difference vegetation index (NDVI) for climate, relief, gradient, channel steepness index (k_sn) for topography, extracting summary statistics (minimum, 10^th, 25^th, 50^th, 75^th, 90^th, maximum, 90^th –10^th, 75t^h –25^th, mean, and median) for each catchment. Because of the stepped nature of the topography in the Rockies resulting from lithologic strength contrasts and glacial modifications, we also compute standard deviation in k_sn and terrain ruggedness index (TRI). Finally, constraining lithologic erodibility is especially challenged by the high variability in the depositional architecture of mixed carbonate-siliciclastic rocks and facies structure of carbonate rocks in passive margins. Therefore, we measure and employ direct intact rock strength measurements using a Schmidt hammer and fine-scale geologic mapping for all the geologic units in each catchment. We partially account for the impact of fault-related damage zones on lithologic erodibility by calculating fault density derived from mapped structures. Additionally, we develop a new method that accounts for landscape stability based on the TOBIA index that accounts for the relationship between the bedding orientation (primary plane of weakness) and hillslope angle. Our findings reveal that the standard deviation of k_sn is a much more important regressor for topography of transitional landscapes than k_sn. Interestingly, we find that climatic factors have significant influence despite their limited variability in the region. Although fully accounting for lithologic erodibility remains beyond the scope of our field, our TOBIA index-based method is a significant step in constraining litho-structural controls on landscape evolution. 

How to cite: Yadav, H., Schoenbohm, L., Akçar, N., Vockenhuber, C., Haag, M., Verma, S., Wolpert, J., and Siea, M.: Post-glacial and litho-structural controls on the fluvial erosion of Southern Canadian Rocky Mountains, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15586, https://doi.org/10.5194/egusphere-egu26-15586, 2026.

Valley networks in sandstone terrains are commonly interpreted as products of structurally-controlled fluvial incision, coupled with hillslope and denudational processes. However, the role of tectonic and subsurface controls in shaping valley morphology and drainage organisation remains insufficiently explored. This study addresses the interplay between surface and subsurface processes in a sandstone tableland, with particular emphasis on tectonic controls, lithological variability, and their influence on valley network geometry and morphological diversity of valleys.

The sandstone-dominated area of the Intra-Sudetic Trough (NE Bohemian Massif) was examined using geomorphometric methods applied to high-resolution airborne LiDAR-derived digital elevation models. A set of primary and secondary topographic indices was calculated to characterize drainage organisation, valley incision, and spatial patterns of erosional dissection. These indices were subsequently integrated using two types of cluster analysis to delineate areas with an enhanced erosional signal.

To complement the geomorphometric analysis, field investigations were conducted, including detailed landform mapping and geophysical surveys employing Electrical Resistivity Tomography (ERT). These data, supplemented by analyses of sandstone composition and petrographic characteristics, provided insights into the links between surface, near-surface, and subsurface processes and geological controls, enabling for the development of a conceptual framework for valley network evolution.

The results demonstrate that valley morphology in sandstone terrains reflects a complex interaction between tectonic structures, lithology, and surface–subsurface process coupling. Pre-existing fault systems and joint networks exert a strong influence on drainage orientation, valley spacing, and incision patterns, often preconditioning zones of enhanced erosion. These structural controls, combined with differential weathering and subsurface erosion, promote the development of a wide spectrum of valley forms, including narrow canyons, gorges, V-shaped valleys, broad troughs, and flat-bottomed valleys, occurring in varied morphological positions within the sandstone-dominated landscape.

The observed morphological diversity cannot be explained solely by rock control on surface fluvial processes. Instead, the study highlights the importance of subsurface processes such as dilation-driven rock mass disintegration, chemical weathering, and fracture-guided underground erosion. The integration of geomorphometric techniques with field-based and geophysical data provides a quantitative and process-oriented perspective on valley network evolution.

How to cite: Porębna, W., Duszyński, F., Kasprzak, M., Hartvich, F., Tábořík, P., Migoń, P., Bartz, W., Jancewicz, K., and Różycka, M.: Valley Network Evolution in Sandstone Terrains: Tectonic Controls and Surface–Subsurface Process Interactions Revealed by Geomorphometric Analyses and Field Surveys, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7063, https://doi.org/10.5194/egusphere-egu26-7063, 2026.

Glacier-induced damming of major Tibetan rivers has been hypothesized to reduce fluvial incision rates and modulate erosion processes, thereby influencing geomorphic stability along the margins of the Tibetan Plateau. The Yigong River, located in the Eastern Himalayan Syntaxis, serves as a critical test site for evaluating this hypothesis due to its documented history of episodic damming. We identify fve paleo-dam events from the last glacial period, focusing on one event at the confluence of the Xiaqu and Yigong Rivers through employing feld investigations, optically stimulated luminescence (OSL) dating, and geophysical surveys. Dam formation is dated to between 12.68 ± 1.17 ka and 10.48 ± 1.02 ka, linked to glacial moraine deposits from the Xiaqu River obstructing the Yigong River channel. Hydrodynamic modeling using HEC-RAS with a 30-m grid resolution and a Manning’s n of 0.045 indicates a maximum flow depth of approximately 60 m through the Tsangpo Gorge. Model results estimate a peak discharge of 4.36 × 104 m3/s following the dam breach, well below previously suggested high-magnitude flood thresholds (~106 m3/s). These fndings imply that the reconstructed paleoflood likely did not cause the extensive erosion noted in earlier geomorphic studies. However, similar paleoflood events likely played a signifcant role in downsteam transport of fne sediment through the Tsangpo Gorge.

How to cite: Liu, F.:  Hydrodynamics of late Quaternary outburst floods along the Yigong River,Eastern Himalayan Syntaxis , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16362, https://doi.org/10.5194/egusphere-egu26-16362, 2026.

Fluvial terraces are key archives of alluvial rivers responding through aggradation and incision to environmental signals. As a result, terraces are commonly attributed to regional climate, tectonic activity, base-level fall, or site-specific geomorphic events. However, if the effects of the different environmental drivers overlap spatially and/or temporally in the catchment, disentangling their impacts on terrace formation remains a significant challenge. Applicable to a variety of catchments, the same challenge applies to the semi-arid Naryn catchment in the Tien Shan, Central Asia: based on moraine, loess and speleothem records the high-elevation landscape reacts sensitively to global climate impacting very probably sediment and water supply to the channel. Additionally, the probably largest known landslide in Central Asia, the Beshkiol landslide, occurred 25 ky ago in the central Naryn valley, damming a lake that persisted for ~17 ky. Rapid drainage of this lake likely triggered a fluvial aggradation and incision response. Numerous fluvial terraces occur along the main stem and several tributaries. These features provide an excellent location to assess the relative, spatial contributions of regional Pleistocene climate and the Beshkiol landslide to terrace formation and to the long‑profile evolution of the Naryn River and its tributaries.

We first ran numerical models of long-profile river evolution to understand better terrace formation patterns in endmember (climate-only, landslide-dam only) and combined scenarios. Secondly, we combineed a set of 38 cosmogenic nuclide exposure samples (¹⁰Be) with 10 optically stimulated luminescence (OSL) samples to constrain fluvial aggradation and incision phases. Finally, we map terrace profiles along ~250 km of the main stem and its tributaries.

Our geochronology identifies aggradation and terrace abandonment phases matching (1) late‑Pleistocene cold phases and (2) the inverval between 20 and 15 ka (post‑LGM), during which the Beshkiol landslide‑dammed lake formed.

 The numerical models generate two contrasting terrace patterns: (1) limited downstream terrace extent associated with lake‑drainage incision, and (2) a basin‑wide suite of terraces produced by climate‑driven changes in sediment‑to‑water ratio. Fluvial terrace mapping reveals widespread terraces even in the tributaries. Terrace slopes are generally sub-parallel; only in the vicinity of the landslide, the main trunk and the tributaries show concave-up profiles.

We conclude that both the landslide‑dammed lake and regional Pleistocene climate influenced terrace formation. Lake drainage primarily affected the lowermost main stem and adjacent tributaries, whereas regional climate was the dominant driver of alluvial terrace formation throughout the catchment. Our study demonstrates that a multi‑method approach—combining numerical modeling, cosmogenic‑nuclide dating, OSL, and detailed terrace mapping—greatly improves the interpretation of alluvial river archives in complex settings. It also provides a framework for quantifying the relative contributions of competing landscape‑evolution drivers.

How to cite: Ruby, A., Schildgen, T., McNab, F., Mariotti, A., Wittmann, H., Moldobekov, B., Kolb, T., and Fuchs, M.: Impact of Climate and a large Landslide in the Tien Shan: Shaping the Naryn Alluvial Valley, Kyrgyzstan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21497, https://doi.org/10.5194/egusphere-egu26-21497, 2026.

Topographies along passive continental margins are shaped by escarpment erosion and dissection of ancient plateau surfaces. Thermochronology and cosmogenic nuclide studies from these settings indicate a near steady process of denudation and inland escarpment propagation since break-up. Yet, a discrepancy exists between measured erosion rates and the scale of observed topographic features, often implying a more complex denudation history. The Madagascar landscape preserves the imprint of two major rifting events, expressed in a remnant escarpment in the west, a deeply dissected central plateau, and a coherent steep escarpment on the east. While steady inland retreat explains the kinematics and position of the great eastern escarpment, the western margin records a more complex morphology, inconsistent with the model of stable retreat of a coastal escarpment. Here, we reconstruct Madagascar’s Cenozoic denudation history and landscape dynamics by combining topographic analysis, ¹⁰Be cosmogenic nuclide concentrations in sediment and numerical modelling of landscape evolution. Catchments draining the plateau–escarpment reveal escarpment retreat rates of several hundred to over a thousand m/Myr on the wet eastern margin, and a few hundred m/Myr along the smaller, drier remnants on the western margin. Retreat rates scale with plateau extent and divide position, which control stream power at the escarpment, while low-erodibility lithologies (granites, basalts) locally inhibit retreat and preserve inland relicts. Numerical models constrained by erosion rates and bedrock erodibilities from Madagascar reproduce observed patterns and demonstrate that eastward migration of the main divide after ~90 Ma triggered large-scale drainage reorganization and pulses of rapid retreat, up to 4 km/Myr, across the western margin. Our findings highlight the inherently dynamic nature of passive margin landscapes, where divide migration and spatial variations in fluvial erosional efficiency govern the long-term evolution of passive margins, with fundamental implications for hydrology, landscape transience, and biodiversity.

How to cite: Clementucci, R., Uchusov, E., Willett, S., Haghipour, N., Randriamananjara, L. H., and Wu, D.: Erosional history and topographic evolution of Madagascar rifted margins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21686, https://doi.org/10.5194/egusphere-egu26-21686, 2026.

How tectonic stress influences topographic evolution remains a central question in regions of active mountain building. The Diancang Mountains, located at the southeastern margin of the Tibetan Plateau, are characterized by steep topography, active fault systems, and highly dynamic river networks, making them an ideal natural laboratory for studying the coupling between tectonic activity and landscape evolution.We specifically investigate how major strike-slip faults locally perturb the regional stress field to govern uplift distribution, which, in concert with fluvial erosion, drives the topographic evolution of the Diancang Mountains.

To address this, we integrate three-dimensional near-surface stress modeling with standard topographic metrics derived from DEM-based terrain analysis. Using Abaqus, we simulate near-surface stress fields by applying boundary conditions consistent with regional tectonic stress field, explicitly accounting for major fault geometries and surface topography.

Preliminary results reveal a strong spatial correlation between zones of elevated differential stress and enhanced river incision. Specifically, we observe persistently high channel steepness (k_sn) along river segments associated with major fault zones and localized stress concentrations. Furthermore, c-mapping identifies pronounced asymmetric drainage divides (interpreted as across divide gradients in erosion rate) in regions of high stress gradients. The orientations of principal stress axes derived from our numerical models align with the preferred directions of divide migration inferred from c analysis.

These results demonstrate that the present-day fluvial morphology of the Diancang Mountains primarily reflects the influence of the shallow crustal stress field that is locally perturbed by major strike slip faulting. Our approach combining finite element stress modeling with quantitative morphometry provides a viable methodological framework for linking tectonic stress patterns to landscape evolution in active mountain ranges.

How to cite: Fan, J., Cao, S., and Robl, J.: Tectonic Stress Control on River Incision and Drainage Divide Migration in the Diancang Mountains, SE Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9972, https://doi.org/10.5194/egusphere-egu26-9972, 2026.

During the late Cenozoic, the outward growth of the Tibetan Plateau significantly influenced the tectonic, climatic, and geomorphic evolution of surrounding regions. The Qinling Mountains, at the eastern front of the Tibetan Plateau, have been involved in plateau expansion since the late Cenozoic, and the Hanzhong Basin, its unique late Cenozoic intermontane basin, preserves rich information on plateau growth. In this study, geomorphic indices, apatite fission track dating, and river-profile inversion were conducted on catchments around the Hanzhong Basin. Results reveal that drainages north of the Hanzhong Basin generally exhibit high steepness indices, especially those in the west, but southern drainages show greater variation. River-profile inversion documents two phases of accelerated relative rock-uplift at 15-10 Ma and 5-2 Ma on northern drainages. We interpret that high steepness indices and uplift rates in the west reflect tectonic forcing, expressed as pronounced relative rock uplift and enhanced subsidence of the western basin, whereas the heterogeneous steepness in the south indicates the differential uplift. Integrating tectonic and sedimentary evidence, we propose a new surface deformation model in which the outward expansion of the Tibetan Plateau since ~15 Ma has forced the rigid Bikou Terrane to wedge eastward, thus reactivating the Mianlue Fault and inducing extensional faulting within the Qinling Mountains and subsidence of the Hanzhong Basin. Synchronously, a series of transpressive faults formed in the Micang Shan and governed the landscape. 

How to cite: Ju, D., Yang, Z., Shi, X., Garzanti, E., You, J., Ma, Y., Ai, H., and Dong, Y.: Late Cenozoic eastward growth of the Tibetan Plateau: evidence from geomorphic indices and river-profile inversion around the Hanzhong Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8346, https://doi.org/10.5194/egusphere-egu26-8346, 2026.

Mountain ranges commonly exhibit asymmetric topography, with main drainage divides offset from the range center. These asymmetries are often attributed to differential rock uplift, but divide positions also respond to bedrock erodibility contrasts and base-level differences between opposing flanks. How these controls interact to determine divide position and whether base-level differences can rival tectonic forcing remain poorly constrained. Resolving these questions is fundamental to interpreting topographic asymmetry in active orogens and extracting reliable tectonic information from landscape morphology. Building on previous work, we present an analytical framework based on the stream power model that quantifies how uplift, erodibility, and base-level elevation jointly control divide positions. We derive dimensionless divide asymmetry numbers that quantify the tectonic-to-erosional forcing ratio controlling divide position, where values <1, ≈1, and >1 indicate tectonic dominance, comparable forcing, and erosional dominance, respectively.

Numerical landscape evolution experiments test our analytical predictions, demonstrating that base-level differences can influence divide position as strongly as differential uplift. The experiments test our analytical framework across a wide range of boundary conditions, confirming that the dimensionless parameters successfully capture divide behavior under diverse tectonic and erosional settings. Applying this framework to the Sub-Himalayan Mohand Range, we find that the observed divide position can be reproduced only when base-level differences between the Himalayan hinterland and Indo-Gangetic foreland are explicitly incorporated. Application to three additional Sub-Himalayan anticlines reveals dramatic variations in divide position across structurally similar fault-related folds, with divide asymmetry numbers ranging from 0.15 to 2.0. These variations correspond to base-level differences of 0-150 m between opposing flanks, demonstrating that base-level offsets of this magnitude control divide asymmetry more strongly than differential uplift in these actively deforming structures.

Our results demonstrate that base-level configuration can exert comparable or even stronger influence than differential uplift on divide position in certain settings. While the potential importance of base-level differences has been recognized, our dimensionless framework provides the first quantitative approach for systematically partitioning these competing controls. This advance enables more robust interpretation of divide asymmetry in active orogens, particularly in settings where topographic gradients naturally generate base-level contrasts between opposing drainage networks. The framework offers a valuable complement to existing approaches for extracting tectonic signals from mountain range morphology.

How to cite: Scherler, D., Kundu, S., and Mandal, S. K.: Quantifying Erosional vs. Tectonic Controls on Divide Asymmetry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21726, https://doi.org/10.5194/egusphere-egu26-21726, 2026.

The competing influence of climate and tectonics drive landscape change. However, separating the relative importance of tectonics and climatic control on the morphology and evolution of Earth’s present-day topography is challenging; climate and tectonics covary, their spatiotemporal scales differ, and geomorphic observations can be inconclusive. Longitudinal river profile analysis has long been used in geomorphology to evidence the influence of tectonics or climate on topography. However, such analysis often requires making limiting assumptions about the spatiotemporal variations in tectonic, climatic and geological conditions experienced by a river network. Here we present a novel river profile network analysis that is less dependent on limiting assumptions, and leverages different measures of river profile concavity. River profile concavity is the rate at which a river network’s slope decreases downstream. We acknowledge an apparent concavity, which reflects the present-day observed geometry, and an inherent concavity, which is the expected concavity of a river network under idealized conditions (all other forcing being equal). Results from numerical modelling show that the differences between the inherent and apparent concavity can be used to extract information about the relative importance of climate and tectonics in shaping river profiles. Applying these results to Taiwan, we demonstrate that the regional pattern of rock uplift, not precipitation, exerts the most significant influence on present-day river profiles. Taken together, these results overcome previous challenges in river profile analysis for deciphering climate vs. tectonic controls on landscape morphology and evolution.

How to cite: Smith, A. G. G., Hurst, M. D., and Ehlers, T. A.: Discerning the relative importance of Tectonic vs Climatic Controls on Topography from River Profile Analysis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9845, https://doi.org/10.5194/egusphere-egu26-9845, 2026.