This study explores the formation, preservation, and uplift of relict low-relief surfaces in the Barkol Mountains, coupled with sedimentological and geochemical insights from the Hami Basin. By integrating digital geomorphic analysis, structural mapping, thermochronology, and sedimentary data, the research reconstructs the tectonic and geomorphic evolution of this region.

Using Shuttle Radar Topography Mission (SRTM) data (3-arc-second resolution), relict low-relief surfaces in the Barkol Mountains were identified based on slope thresholds (<14°) and hydrological analysis in ArcGIS. Cross-sectional profiles and slope-aspect analyses highlight tectonic influences, including fault-induced tilting and segmentation, with boundary faults playing a significant role in surface deformation.

Apatite fission track (AFT) analyses from granitic samples reveal prolonged slow cooling during the Late Cretaceous (124.6–63.5 Ma), indicating minimal exhumation and surface preservation. Younger AFT ages (50–55 Ma) near the southern boundary fault suggest Paleogene fault reactivation and accelerated cooling. Single-grain AFT ages from modern river sands on the southern slope are dispersed, with peaks at 135.7 ± 9 Ma, 86.4 ± 5.3 Ma, and 50.4 ± 4.7 Ma, corresponding to bedrock ages. Apatite (U-Th)/He (AHe) data corroborate these findings, with younger ages (~30 Ma) in faulted regions, reflecting enhanced exhumation due to tectonic activity. These results underscore the structural control of exhumation processes, contrasting slow hinterland cooling with rapid fault-zone cooling.

In the Hami Basin, sedimentological and geochemical analyses of Cretaceous and Cenozoic deposits link sediment provenance to tectonic uplift. Detrital AFT ages from basin sediments show peaks at ~170 Ma and ~100 Ma, aligning with erosion events in the Bogda and Harlik-Barkol Mountains. Geochemical analysis reveals that apatite ages from mafic rocks cluster in the Middle Jurassic, while those from granitic rocks concentrate in the Early Cretaceous, corresponding to sources in the Bogda and Harlik-Barkol Mountains, respectively. This pattern likely reflects the sequential uplift and exhumation of the Bogda and Harlik-Barkol Mountains.

In conclusion, the Barkol Mountains exhibit relict surfaces formed during slow Late Cretaceous cooling, disrupted by Paleogene fault reactivation and accelerated exhumation. Additionally, the Hami Basin archives sedimentary records of tectonic-driven erosion, offering insights into the interplay between tectonics, geomorphology, and basin evolution in the Eastern Tianshan.

How to cite: Zhao, Z., Wang, G., Shen, T., and Ma, C.: Meso-Cenozoic Tectonic and Geomorphic Evolution of the Eastern Tianshan: Insights from the Barkol Mountains and Hami Basin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2555, https://doi.org/10.5194/egusphere-egu25-2555, 2025.

The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay among river incision, glacial movement and rock uplift is important for understanding tectonic deformation in this region. We report here the discovery of a deeply incised canyon of the Yarlung Tsangpo River, at the eastern end of the Himalaya, which is now buried under more than 500 meters of sediments. By reconstructing the former valley bottom, analyzing sedimentary phase and dating sediments at the base of the valley fill, we show that fluvial sediment accumulation started at about 2 million 2.5 million of years ago, and extensive glacial advances occurred after ~0.75 million of years. Our findings reveal that rapid rock uplift is the direct cause of the high erosion rates within the gorge, which began to steepen about 2-2.5 million years ago. Notably, the earliest extensive glacial advance (~0.75 million of years) is considerably younger than the formation of the Tsangpo Gorge (>2.5 million of years). Following the initiation of this glacial advance, the Eastern Himalayan Syntaxis experienced rapid exhumation of approximately 1.3-1.6 kilometers. Such geomorphological processes and exhumation history suggest that rock uplift, rather than glacial damming, played a pivotal role in maintaining the stability of the knickpoints on the southeastern margins of the Tibetan Plateau.

How to cite: Wang, P., Hu, G., Wang, H., and Ge, Y.: Tectonic and climatic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3509, https://doi.org/10.5194/egusphere-egu25-3509, 2025.

A major challenge in magma-rich continental rifts, such as Afar, is to understand the evolution of fault networks in space and time. This is due to the lack of subsurface seismic reflection data and the presence of complex, variable-age lava flows at the surface. Most past studies have focussed on establishing tectonic history and fault evolution of onshore continental rift systems, with the help of geodynamic and analogue models. The dynamic response of fluvial landscapes to tectonic activity is an additional tool that can be used to better understand fault network evolution. However, little to no work has been done to date using quantitative geomorphology to understand the evolution of normal faults in magma-rich continental rift systems.

To deepen our understanding of fault evolution in these tectonic settings, this study focusses on the graben systems in the Central Afar region in Ethiopia, and small-scale streams that crosscut the graben fault systems. This study uses a combination of GIS DEM analysis, river long profiles, integrated with available ages of the lava deposits on the surface, to quantify landscape and geomorphic responses of river systems to extension in the Afar Region. The work done in this study provides new insights into the timing and magnitude of fault growth and interaction associated with normal faulting over timescales of 100,000 years.

How to cite: Chandresh, R., Keir, D., C. Whittaker, A., Corti, G., E. Bell, R., Sani, F., Pagli, C., La Rosa, A., and Tortelli, G.: Fault Evolution in Magma-Rich Rifts using Quantitative Geomorphology: Insights from Central Afar, Ethiopia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4765, https://doi.org/10.5194/egusphere-egu25-4765, 2025.

It is well understood that landscapes do not immediately adjust to changes in tectonic boundary conditions but instead undergo transient adjustments over time. Few studies have documented this transient adjustment by collectively examining fluvial, hillslope, erosional, and chemical weathering responses to tectonic perturbations. Here, we address this knowledge gap by investigating the Fiumara Allaro drainage basin, a ~98 km² catchment located in the Serre Massif of Calabria, Italy. The Fiumara Allaro is well-suited for such a study because it is predominantly underlain by granitic rock, has experienced a well-constrained order-of-magnitude increase in rock uplift rate at ~1.5 Ma, and benefits from high-resolution digital topographic data. Using a nested sampling approach, we collected data on channel width and grain size, and measured major element water chemistry as well as ¹⁰Be cosmogenic radionuclide concentrations along a transect from the steep lower reaches of the Fiumara Allaro to its high-elevation, low-relief upland. These data, combined with detailed topographic analysis, provide a holistic understanding of the landscape’s response to a step change in rock uplift rate. Geomorphic metric analysis reveals distinct contrasts between relict topography and actively incising regions, highlighting the transient nature of the landscape. Knickpoints are consistently observed at elevations between ~800 and ~1,000 m, separating the relict landscape from actively incising domains. Above the knickpoints, in the relict landscape, lower normalized steepness index (k_sn) values (~10–30 m⁰.⁸) reflect slow fluvial incision and a limited response to tectonic forcing. In contrast, the actively incising landscape below the knickpoints shows elevated k_sn values (~50–70 m⁰.⁸), indicating rapid incision and dynamic adjustment to increased uplift rates. Estimates of channel width, cast as the normalized wideness index, drop by more than a factor of 2 below the knickpoints, indicating channel narrowing after accounting for downstream increases in drainage area. Erosion rates in the relict landscape remain low, ~0.06–0.27 m/Myr, while rates downstream increase significantly to ~0.40–0.50 m/Myr, reflecting active incision driven by uplift. Grain size distributions further corroborate these trends: coarse material (D₈₄ ~731 mm) is concentrated in actively incising zones, while finer material (D₈₄ ~43–64 mm) dominates the relict landscape upstream. Preliminary water chemistry data indicate that cation concentrations generally increase below the knickpoints before declining further downstream, suggesting a potential coupling between physical and chemical weathering processes. Hillslope curvature analysis indicates that hilltops sharpen in response to active incision, reflecting ongoing transient adjustment to increased uplift rates. The Fiumara Allaro basin clearly exhibits geomorphic evidence of transient adjustment to uplift, with knickpoints and marked differences in erosion rates, k_sn values, grain size distributions, and water chemistry trends between relict and incising domains, highlighting a delayed response to tectonic forcing. More detailed findings, along with an assessment of fluvial and hillslope response times and a discussion of the implications for physical and chemical weathering in transient landscapes, will be presented at the meeting.

How to cite: Ghamedi, O., Gallen, S., and Perez Hincapie, A.: Holistic quantification of transient landscape response to rock uplift changes in the Fiumara Allaro catchment, Calabria, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9329, https://doi.org/10.5194/egusphere-egu25-9329, 2025.

Neogene tectonics and geomorphic processes in response to Quaternary climate change drive landscape evolution in western Mongolia's Basin of Great Lakes (BGL). The endorheic Khyargas Nuur (Nuur=lake) in the BGL is the ultimate sink of a sequential water and sediment cascade from the adjacent Mongolian Altai and Khangai Mountains. Several intercalated lakes repeatedly joined as one major paleolake controlled by changes in atmospheric moisture supply and glacial meltwater influx throughout the Late Quaternary. Relict shoreline features up to +188 m above the modern lake (aml) provide direct geomorphic evidence of a mega (>13x modern area) paleolake Khyargas. Terrestrial cosmogenic nuclide (TCN) exposure dating of the highest observed shoreline of the Khyargas Nuur at +188 m aml, using a ¹⁰Be depth profile, provides a maximum temporal framework for the investigated paleoshoreline sequence. Notably, local offsets exist between expected and mapped/measured absolute beach ridge elevations. For example, absolute elevations for beach ridges associated with a +15 m aml lake level vary by up to 6.8 m with a standard deviation of 0.9 m (n=2760). Reconstructed beach ridge elevations vary by 10.9 ± 1.6 m for the prominent +118 m aml paleoshoreline (n = 2962). Luminescence dating of associated shoreline features yielded ages of ~2.1 ka and ~14 ka for the +15 and +118 m shorelines, respectively. Comparative statistical differences in the offset values of these two shorelines and concurrent spatial similarities of displacement hotspots suggest a time-dependent, cumulative paleoshoreline displacement mechanism. We hypothesize that observed shoreline offsets are induced by either (a) local tectonically active fault displacements, (b) hydro-isostatic adjustments similar to those observed around the margins of paleo-lake Bonneville in the U.S. Great Basin (¹) and paleo Lake Chad (²) in north-central Africa, or (3) reactivation of zones of crustal weakness (old faults) caused by water loading and unloading. To evaluate the potential driving mechanisms on these displacements, we constructed a three-dimensional flexural isostatic model that utilizes paleoshoreline observations to determine rates and magnitudes of deflection and to test for robust constraints of the lithospheric effective elastic thickness (T_e).

(¹) Adams, K. D. & Bills, B. G. Isostatic Rebound and Palinspastic Restoration of the Bonneville and Provo Shorelines in the Bonneville Basin, UT, NV, and ID. in Developments in Earth Surface Processes vol. 20 145–164 (Elsevier, 2016).

(²) Mémin, A., Ghienne, J.-F., Hinderer, J., Roquin, C. & Schuster, M. The Hydro-Isostatic Rebound Related to Megalake Chad (Holocene, Africa): First Numerical Modelling and Significance for Paleo-Shorelines Elevation. Water 12, 3180 (2020).

How to cite: Wolf, D., Gelman, S., Wegmann, K., Ellis Curry, M., Marques Figueiredo, P., and Lehmkuhl, F.: Using paleolake shorelines to estimate lithospheric strength and response rates: Field observations and flexural isostatic modeling of Lake Khyargas, western Mongolia., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18945, https://doi.org/10.5194/egusphere-egu25-18945, 2025.

Extensive marine terraces preserved along the Cantabrian coast have been pointed out as good markers to understand the recent tectonic evolution of the Cantabrian margin in north Iberia. These landforms are interpreted as a single, kilometric-wide abrasion platform eroded during the Pliocene marine transgression (Mary 1983) which were later uplifted and faulted due to recent tectonic activity (Álvarez-Marrón et al., 2008). A recent study also points to continuous rising in response to lateral gradient in crustal thickness as a mechanism to explain the subtle variations in surface tilt observed only in the marine terraces of the western coastal areas (López-Fernández et al., 2020).

This contribution provides the first catchment-wide erosion rate estimates based on cosmogenic ¹⁰Be-²⁶Al measured in two sediment samples retrieved from a 3.1 km² extent fluvial basin incised in the marine terrace. The river basin is entirely composed by quartz-bearing rocks belonging to the Serie de los Cabos formation, which comprises alternating slate, sandstone and quartzite. Total incision since terrace formation reaches 80 m along the main river stream, while 21.2 m is the average incision achieved considering the total volume of material removed (ca. 60 Hm³) since the terrace uplift from an area of 283.3 Ha. Using the code Riversand v. 1.3.1 by Stübner et al. (2023), we computed catchment-wide erosion rates of 11.5 to 12.1 mm/ka based on ¹⁰Be and 17.3 to 18 mm/ka based on ²⁶Al. These rates involved that at least 1.2 to 1.9 Ma are required to achieve ~21 m of averaged incision, which is in good agreement with previous minimum surface exposure ages of 1-2 Ma estimated combining ¹⁰Be-²⁶Al-²¹Ne (Álvarez-Marrón et al., 2008). Similar analysis in other catchments might help to expand our current knowledge on the erosion patterns of these landforms, improving our understanding on competing mechanisms involved in the origin and dismantle of marine terraces.

Research funding: RETROCLIFF (PID2021-122472NB-100, MCIN/AEI/FEDER, UE) and GEOCANTABRICAE (SV-PA-21-AYUD/2021/51766, FICYT, Principality of Asturias, UE, ERDF).

 References:

• Álvarez-Marrón, J., Hetzel, R., Niedermann, S., Menéndez-Duarte, R., Marquínez, J. (2008). Origin, structure and exposure history of a wave-cut platform more than 1 Ma in age at the coast of northern Spain: A multiple cosmogenic nuclide approach. Geomorphology 93, 316-334. https://doi.org/10.1016/j.geomorph.2007.03.005
• Mary, G. (1983). Evolución del margen costero de la Cordillera Cantábrica en Asturias desde el Mioceno. Trabajos de Geología 13, 3-35.
• López-Fernández, C., Llana-Fúnez, S., Fernández-Viejo, G., Domínguez-Cuesta, M.J., Díaz-Díaz, L.M. (2020). Comprehensive characterization of elevated coastal platforms in the north Iberian margin: A new template to quantify uplift rates and tectonic patterns. Geomorphology 364, 107242. https://doi.org/10.1016/j.geomorph.2020.107242
• Stübner, K., Balco, G., Schmeisser, N. (2023). Riversand: a new tool for efficient computation of catchmentwide erosion rates. Radiocarbon. https://doi.org/10.1017/RDC.2023.74

How to cite: Rodríguez-Rodríguez, L., Domínguez-Cuesta, M. J., Braucher, R., Cuervas-Mons, J., Aumaître, G., Keddadouche, K., Zaidi, F., and Jiménez-Sánchez, M.: Catchment-wide erosion rates relying on cosmogenic nuclides provide new clues on the evolution of marine terraces along the Cantabrian margin, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6339, https://doi.org/10.5194/egusphere-egu25-6339, 2025.

The evolution of landscapes over time is governed by autogenic processes, such as sediment dynamics and landslides, and allogenic processes and factors, such as tectonics and lithology. The style of tectonic deformation governs the spatiotemporal distribution of rock types exposed at Earth’s surface, controlling how surface processes shape the landscape. The evolution of lithologically complex landscapes like fold-and-thrust belts remains incompletely understood because it is not clear how lithology affects the interactions between, and relative dominance of, different surface processes. The Appalachian Valley and Ridge physiographic province, an ancient fold-and-thrust belt, provides a unique natural laboratory for studying the interplay among tectonics, lithology, and surface processes. The region's diverse lithology is vividly displayed in exposed, breached anticlines, where resistant sandstones form ridges, and more erodible or weatherable carbonates and shales form valley bottoms in anticline cores. Breaching occurs when the crest is eroded, exposing deeper, often weaker layers. The mechanisms behind anticline breaching and breach expansion are not well understood and could be triggered by large episodic events, such as landslides, more gradual processes such as fluvial incision, or a combination of the two. In this study, we set up a landscape evolution model mimicking the evolution of Appalachian landscapes to investigate how autogenic interactions among fluvial incision, sediment dynamics, and landsliding respond to the lithological and structural variability found in ancient fold-and-thrust belts like the Appalachian Valley and Ridge province. We explore landscape evolution through a series of modeling experiments and develop new metrics to capture the dynamics of breached-anticline systems. By comparing metrics between modeled and real landscapes, we quantify the role of episodic landsliding in controlling anticline breaching and the dynamic evolution of tectonically inactive landscapes where the spatial distribution of different rock types governs landscape evolution. 

How to cite: Campforts, B., Shobe, C., and Prince, P.: The influence of landslides on anticline breaching and landscape evolution in the Appalachian Valley and Ridge, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6992, https://doi.org/10.5194/egusphere-egu25-6992, 2025.

The central South Tian Shan, marked by high elevation, high relief, an uplifted relict landscape and interspersed intermontane basins, offers an ideal setting to study the far-field tectonic response to Indian-Asian convergence, and the interplay of topographic growth, erosion and climatic aridification since the late Cenozoic. Previous thermochronology studies from the highest massifs of the central South Tian Shan - the Khan Tengri and Pobedi massifs - reported accelerated exhumation since the Late Miocene (~ 10 Ma), linked to the reactivation of inherited structures propagating towards the Tarim Basin to the south. Little is known about the spatial distribution, timing and rates of erosion along the main fault structures in this region. To better address this question, we study exhumation associated with the Pobedi Thrust, a major Paleozoic fault with significant inferred Late Cenozoic reactivation. New apatite and zircon (U-Th-Sm)/He (AHe and ZHe) as well as apatite fission-track (AFT) data was collected along an elevation profile from both the hanging wall and footwall of the western branch of the Pobedi Thrust to quantify the low-temperature thermal history. 
In contrast to enhanced Late-Miocene exhumation recorded in the Khan Tengri and Pobedi massifs, our samples from approximately 100 km to the west indicate dominant Mesozoic cooling and minimal Cenozoic exhumation, despite the region’s high (> 4 km) topography and significant (> 2 km) relief. Our southernmost sample provides a hint of exhumation associated with the South Tian Shan thrust (i.e., Maidan Fault), showing Late Paleogene AHe ages. 1D thermal history modeling suggests a phase of accelerated cooling of valley-bottom samples during the Late Miocene. Consistent with thermochronology data, mapping and interpolation of low-relief surfaces indicate Cenozoic tilting and deformation of the pre-Oligocene relict topography. These findings highlight spatially variable exhumation along the Pobedi Thrust and Maidan Fault and provide new insights into the complex Cenozoic tectonic activity of the central South Tian Shan and long-term landscape evolution processes.

How to cite: Gong, L., van der Beek, P., Sobel, E., Schildgen, T., Mariotti, A., Glodny, J., Kyiazbek, A., and Nurbek, S.: Cenozoic uplift and exhumation of the central South Tian Shan, Kyrgyzstan , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11719, https://doi.org/10.5194/egusphere-egu25-11719, 2025.

On January 1st, 2024, the Mw 7.5 Noto Peninsula earthquake ruptured on a series of coastal offshore reverse faults in the back arc of central Japan. Closest to the rupture, in the northwest, the coastal rocks uplifted as much as 4.4 m (Fukushima Yo et al., 2024). The coastline accordingly moved seaward by up to 200 m creating new wide bedrock platforms. Recent Holocene terraces mapped along the northern coast (Shishikura et al., 2020), where coseismic uplift was greatest on January 1st 2024, suggest similar past ruptures. Many of the ruptured faults follow the coast at a depth of ca. 60 m below modern sea level. This is the average elevation of sea level over the last 500 kyr, and strongly suggests that these faults define the extent of the continental domain.

The Peninsula itself hosts 4767 unique mapped terraces ranging in age from Holocene to 1.02 Ma (Ota and Hirakawa, 1979, Koike and Machida, 2001). The terraces associated with the last two interglacial high stands (ca. 120 and 234 ka) record a tectonic SE-tilting similar to that of the Mw 7.5 earthquake. Older terraces all record a spatially uniform rate of uplift across the Peninsula. The landscape itself does not appear to be equilibrated to this gradient in uplift, with a seemingly disconnected fluvial geometry. We conclude that the faults that caused the most recent earthquake became the dominant structures on the Peninsula around 250 ka and that the Peninsula is in a state of transient equilibration.

80 km northeast of the Noto Peninsula lies the Island of Sado. The Island is made of two mountain ranges oriented SW-NE along the main tectonic lineation of the back arc, roughly parallel to the northern coast of Noto Peninsula. The marine terraces of the northern range, Oosado, record a strong southeast tilting synchronous and similar to that observed on the Noto Peninsula. The landscape morphology is not equilibrated to this pattern of deformation either. Earlier work by Ota et al., (1992) suggested that the tilt is driven by a fault lying just offshore of the Oosado coast. Closer inspection of the bathymetry reveals a ramp at around -60 m reflecting a geometry similar to the Noto Peninsula. The lessons from the Noto Peninsula earthquake can be applied to Sado Island where information about the seismic cycle is lacking. It confirms the hypothesis of Ota et al. (1992) and highlights a potential seismogenic source close to the shore.

Koike, K., & Machida, H. (2001). Atlas of Quaternary… Tokyo: University of Tokyo Press.

Ota, Y., & Hirakawa, K. (1979). Marine terraces and… Geographical Review of Japan, 52(4), 169–189.

Ota, Y., Miyawaki, A., & Shiomi, M. (1992). Active Faults on Sado Island… Journal of Geography (Chigaku Zasshi), 101(3), 205–224.

Shishikura, M., Echigo, T., & Namegaya, Y. (2020). Activity of the off-shore… Active Fault Research, 53, 33–49.

How to cite: Malatesta, L. C., Sueoka, S., Weiss, N.-M., Gailleton, B., Tsukamoto, S., Ishimura, D., Nishimura, T., Takahashi, N., Kataoka, K., Komatsu, T., and Iwasa, Y.: Active faults and coastal landscapes in the back arc of Central Japan, lessons from the Mw 7.5 Noto Peninsula earthquake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11196, https://doi.org/10.5194/egusphere-egu25-11196, 2025.

The combined record of past sea levels and crustal deformation can be found in the landscapes of tectonically active coastlines. Marine terraces, sea cliffs, or intertidal platforms all reflect the work of multiple geomorphic processes sculpting the coast. Researchers have investigated the key erosional mechanisms responsible for shaping the coasts. Field observations suggest that platform formation is driven by three primary processes: (1) mechanical erosion from the kinetic energy of marine waves, (2) physical or chemical weathering driven by wetting-drying cycles, and (3) biochemical weathering, which may amplify or even sometimes dominate the other two processes. However, determining the dominant process remains challenging, as each mechanism is interacting with other processes, making it is hard to disentangle their relative contribution. Numerical models for coastal evolution exist but we are not able to properly evaluate their accuracy, or to convincingly simulate the respective roles of different processes over 100s of kyr.

In this study, we compare and assess the outputs of models that emphasize different processes by simulating the shoreline evolution trajectories under identical (or varying) wave conditions and sea level scenarios. The results reveal that the shape of coastal topography, including intertidal platform, varies significantly depending on the dominant process or assumptions, such as the rate of debris removal from failed cliffs. Notably, these differences become more pronounced when considering the direction of sea level change. Additionally, we build a framework that enables the simulation of process combinations by selectively activating or deactivating specific modules within the system. By systematically comparing models and their combinations, we aim to develop a comprehensive framework for coastal erosion that can be adapted to specific sites and conditions.

Looking ahead, we seek to link these distinct platform development trends to long-term coastal morphological features, such as marine terraces. Over geological timescales characterized by glacial sea level fluctuations, prolonged platform formation may produce distinct marine terraces. Understanding these trends in coastal erosion can provide valuable insights into the generation and preservation of coastal geomorphology.

How to cite: Keum, D., Malatesta, L., Tsukamoto, S., Huppert, K., Bovy, B., and Braun, J.: From Short-Term Erosion to Long-Term Landforms: Linking Different Coastal Erosion Models to Marine Terrace Formation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12302, https://doi.org/10.5194/egusphere-egu25-12302, 2025.

Over recent decades, innovative quantitative methods have been developed to study the internal dynamics of river basins. Most of these approaches assume stable or minimally drainage divide mobility (DDM), based on the premise that the rate of river network evolution is significantly faster—by several orders of magnitude—than the mobility of drainage divides. However, recent studies challenge this assumption, showing that the Gilbert metrics can effectively measure DDM and reveal scenarios where drainage divides shift more rapidly than river network adjustments. This dynamic complicates the interpretation of river profiles. In particular, χ-values near headwaters have been identified as indicators of DDM, with low χ-value catchments tending to migrate towards those with higher χ-values. Yet, this interpretation hinges on the premise that mean rock uplift rates, erodibility, and base level heights are consistent across the system. Over geologic timescales, such uniformity is improbable across entire mountain ranges, thereby limiting the universal applicability of this tool. Therefore, thoughtful evaluation of potential DDM is crucial for understanding landscape evolution and also how drainage divide contains information on past climatic and tectonic forcings itself. In this study, we focus on an endorheic watershed in the hyperarid core of the Atacama Desert, northern Chile. The hyperarid conditions present in the Atacama Desert provides a unique opportunity to capture geomorphic signatures as far back as the Paleogene evolutionary stages. We propose a downscaling analysis of DDM applied to three local-scale watershed divides. By integrating geomorphological mapping, morphometric indices, and existing geochronological data, we aim to evaluate DDM across representative sections at a local scale. Furthermore, these results will be validated using forward landscape evolution modeling in Landlab 2.0. Our findings are expected to provide quantitative estimates by comparing widely recognized metrics. We also emphasize the utility of χ-values and Gilbert metrics in sub-catchments to decipher local-scale landscape changes within a basin characterized by multiple evolutionary stages. This downscaling approach refines our capacity to interpret and forecast landscape evolution with exceptional spatial precision, even within the context of an extreme climatic environment, offering profound insights into the complex interactions among tectonic, climatic, and geomorphic processes.

How to cite: Cisternas, R., Olivares, L., López, C., Riquelme, R., Baltazar, I., Espinoza, S., Rebolledo, M. C., Herrera, B., and Ríos-Contesse, J.: Extending the limits of divide migration criteria: A downscale approximation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14831, https://doi.org/10.5194/egusphere-egu25-14831, 2025.

In the northern Andes of Colombia, seismic and tomographic studies evidence a slab relay between the gently dipping northern Bucaramanga segment and the southern steeply inclined Cauca segment. These studies indicate a clear-cut change in the sub-continental slab constellation and evidence of a lithospheric tear. Superficial structural and geomorphic changes above this relay zone depend on the observation scale and are best developed in the Eastern Cordillera of Colombia, a bi-vergent mountain belt decoupled from the Andean main trunk, which evolved by the inversion of an Early Cretaceous foreland basin. At the transition from steep to flat slab segments, this mountain belt doubles its width and attains considerable heights by a combination of exhumation and surface uplift. The external part of the tear coincides with the cratonward-oriented deformation front of the Eastern Cordillera. Here, faults are related to tight, basement-involved folding, suggesting a high geothermal gradient for this ductile deformation style. The youngest structures are represented by domes aligned parallel to the structural trend. These domes overprint existing folds and suggest by their size and association to circular normal faults growing and decaying evolutionary stages, demonstrating a southward propagation of a thermal mantle anomaly. In the western Central Cordillera, transversely oriented monogenetic volcanic fields similarly show a recent southward propagation of volcanic activity. A southward shift of the slab tear is further evidenced by transversely oriented fold trains. This scenario of a southward migrating slab tear encourages us to undertake a morphological study to evaluate the maturity of drainage and landscape evolution and to corroborate an N-S younging of recent tectonic activity. A reference for recent tectonic activity is the volcanic center of Paipa, centered along a fissure-like caldera and aligned transversely to the regional fold trend, indicating axial extension. Additionally, a subvolcanic rhyolitic stock has refolded a flank of an existing fold diapirically. These crustal mobilizations occurred during and after the late Miocene folding (implying NW-SE shortening) and before a second fold phase related to E-W shortening during the Cordillera’s final uplift stage. We use a novel analysis to identify the degree of directional organization of small river segments compared to the local structural trend. The reorganization of drainage indicates ongoing folding and tilting of hanging wall blocks related to major reverse faults and regional tilting of the cordillera’s axial depression. The capture of previously established longitudinal river valleys of the high plains documents the dynamics of transverse drainage during the final uplift and exhumation of the Cordillera’s eastern flank. The deviation of transverse rivers along frontal folds helps identify actively forming structures. Conversely, the weakly preferred drainage orientation in the axial depression north of the tear suggests a more mature landscape. With these geomorphological criteria, we aim to discuss the dynamics of the Caldas Tear and its southward propagation. Did the shallowing of the subducting plate occur gradually, involving lithospheric bending, or was it caused by the migration of a tear that swept through the Cordilleran realm until reaching its present southern position?

How to cite: Kammer, A., Zeilinger, G., and Saavedra Serrano, J. S.: New structural and geomorphological observations at the transition from shallow to steep subducting plate along the Caldas Tear in the Colombian Cordilleras, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16921, https://doi.org/10.5194/egusphere-egu25-16921, 2025.

The impact of Quaternary glaciations on denudation rates has long been debated and the proposition of the instability of climate as a driver of higher denudation rates since the Pliocene has yet to be proven. Most denudation rate reconstructions have focused on areas either tectonically active or glaciated, or both during that period, leading to difficulty in quantifying the impact of climate cyclicity on denudation, as the deciphering of climatic over tectonic control on denudation can be challenging, and glacial erosion appears to be non-linear, and overprints any other forcing. Furthermore, these studies have mainly concentrated on northern hemisphere or high latitude regions. A global increase of denudation implies other regions should be equally impacted but a large gap in data and knowledge exists in low latitude Tropical regions. Therefore, key regions to better understand the impact of climate on denudation should be free of tectonic activity or glacial processes and located under the Tropics.

In this work, we propose to quantify paleo-denudation rates of the Ogowé catchment (Gabon) over Plio-Pleistocene times by measuring ¹⁰Be in quartz grains collected from turbidite samples of three cores and one probe collected 30 km to 200 km offshore the mouth of the Ogowé river. To better constrain transport times of these sediments and quantify their ages of burial, we also measure both radiocarbon ages of vegetal debris contained in the turbidites and ²⁶Al/¹⁰Be ratios.

Our results show near constant denudation rates over the Pliocene, leading to two possible conclusions. Either the Quaternary climatic cycles did not affect local tropical climate of the Ogowé region, or denudation rates remain unaffected by climatic variability, at the scale of 10 ka to 100 ka.

How to cite: Large, E., Charreau, J., and Blard, P.-H.: Limited effect of Quaternary climatic cycles on tropical denudation from10Be paleo-denudation rates of the Ogowé catchment (Gabon), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17366, https://doi.org/10.5194/egusphere-egu25-17366, 2025.

The Mid-Pleistocene Transition (MPT; ~1.2–0.9 Ma) marked a shift in global climate cycles, amplifying glacial-interglacial oscillations and lengthening their periodicity. In the Patagonian Andes, intensified erosion due to late-Miocene glaciation is well documented, but geomorphic evidence also suggests accelerated exhumation after the MPT. The Southern Patagonian Icefield, draining into Argentino Lake and the Santa Cruz River, provides a direct link between glacial erosion and downstream fluvial systems. To quantify these impacts, we combine Apatite (U-Th)/He thermochronology and cosmogenic ¹⁰Be dating. Single-grain apatite (U-Th)/He ages from bedrock bordering Argentino Lake, and an 1175 m elevation profile, range from ~4–8 Ma, with apparent exhumation rates of ~0.28 km Ma⁻¹. Coupled thermal and landscape modeling suggests an acceleration of erosion post-4 Ma. Downstream, ¹⁰Be-dated fluvial terraces of the Santa Cruz River reveal incision rates of ~0.13–0.18 km Ma⁻¹ over the last 1 Ma, with transient acceleration (~0.66 km Ma⁻¹) between 1.03–0.93 Ma, coinciding with intensified glaciation after the MPT. Terrace ages also show a shift from shorter periodicities to 100-kyr cycles. Our results suggest the MPT triggered enhanced glacial erosion in the Andes, influencing sediment discharge and downstream channel-bed elevation. This study highlights the MPT’s measurable impact on both glacial source areas and downstream depositional systems.

How to cite: Milanez Fernandes, V., Schildgen, T., van der Beek, P., Wittmann, H., Sobel, E., Friedrichs, B., Ruby, A., McNab, F., and Georgieva, V.: Linking Glacial Exhumation and Fluvial Incision During the Mid-Pleistocene Transition, Southern Patagonia, Argentina, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19506, https://doi.org/10.5194/egusphere-egu25-19506, 2025.

A significant portion of Zrinska Gora mountain in Croatia is covered by Paleogene siliciclastic deposits. These deposits are thought to have formed in a flexural foreland basin that developed during the Late Cretaceous and Paleogene along the northwestern segment of the Sava Zone, a tectonic unit formed by the continental collision of the Adria plate and the Tisza Mega-Unit (Ustaszewski et al., 2010).

This study investigates the sedimentological and petrological characteristics of Paleogene sedimentary deposits, focusing on conglomerates, to reconstruct their provenance and depositional history. Our methodology included sedimentological logging and sampling, optical microscopy and heavy mineral analysis. Detailed petrographic investigation of conglomerate pebbles resulted in the determination of 12 lithotypes, comprising various magmatic, volcaniclastic, cataclastic, and metamorphic rock types, based on their mineralogical and structural-textural characteristics. Associated sandstones classify as litharenites with phyllosilicate and hematite cement, containing rock fragments similar to the lithologies observed in the conglomerate pebbles.

Provenance analysis suggests that the clastic material primarily originated from units of the Sava Zone, as indicated by granophyre, syenite, and monzonite clasts. Volcanic pebbles point to mixed sources from various Mesozoic complexes, while metamorphic clasts reflect contributions from pre-Eocene formations across the broader area, exhibiting medium- to high-grade regional metamorphism. Notably, a slight shift in heavy mineral composition across the studied localities suggests a relocation of the primary sediment source, possibly from the Western Vardar Ophiolitic Unit to the Sava Zone and Tisza Mega-Unit, reflecting tectonically driven sedimentary reorganization in the foreland basin. These findings provide new and preliminary insights into the development of clastic sediments in syncollisional basins along the northwestern part of the Sava Zone during the Paleogene. The presented work is supported by the Croatian Science Foundation project SECret (HRZZ IPS-2023-02-2683).

References:

Ustaszewski, K., Kounov, A., Schmid, S.M., Schaltegger, Fügenschuh, B. et al. (2010): Evolution of the Adria‐Europe plate boundary in the northern Dinarides: From continent‐continent collision to back‐arc extension. Tectonics, 29(6), 34.

How to cite: Plavac, M., Lužar-Oberiter, B., and Petrinec, Z.: Indications of Provenance and Source Rock Contributions in Paleogene Deposits from Zrinska Gora, Croatia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18576, https://doi.org/10.5194/egusphere-egu25-18576, 2025.

The extent that climate impacts erosion has long been debated and is difficult to decipher, as climate signals are often obscured by tectonic signals. The Hawaiian Islands are excellent settings to test these relationships, as they have no tectonic uplift, well-known base level histories, uniform lithology, and dramatic climate gradients. On Kauai, previous work shows a correlation between rainfall and total canyon incision; however, geologic evidence shows that river incision could not have been constant throughout time: ~2 Ma inset lava flows sit at river level in several canyons on the ~4.5-million-year-old island, indicating that canyon incision has been negligible over the last 2 Myr. One explanation is that boulders and/or sediment flux in streambeds block further incision, acting as thresholds. Channel gradients on the Hawaiian Islands decrease with increasing precipitation and appear to be in equilibrium (uniform k_sn below knickpoints), indicating that channel gradient is set by the threshold of boulder or sediment mobility. Therefore, climate appears to be recorded in threshold channel slope and total incision depth instead of time averaged incision rate as previously assumed (Ferrier et al., 2013). We traveled to Kaui and West Maui to test the hypotheses that (a) boulders and/or (b) sediment act as thresholds for fluvial incision, by (a) quantifying channel morphology and boulder size using structure from motion photogrammetry, drone photography and pebble counts, and (b) collecting catchment-average samples for cosmogenic radionuclide analysis (³⁶Cl in magnetite), in catchments across gradients of precipitation rate and channel slope. Preliminary data suggests that boulder size scales with channel gradient within climate zones, indicating that boulders are an important threshold for channel incision. However, if channel gradient is correlated with upcoming denudation rates, sediment flux may be an additional important threshold. Next steps include quantifying basal and critical shear stress for boulder transport and combining data into a landscape evolution model. Ultimately, we aim to answer long-standing questions regarding the roles of climate and fluvial thresholds in landscape evolution, applicable in both tectonically inactive and active landscapes.

How to cite: Lodes, E., Colaianne, N., Raming, L. W., Whipple, K. X., Yager, E., Granger, D. E., and Strauch, A. M.: Controls of climate and fluvial thresholds on stream incision on the Hawaiian Islands  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20636, https://doi.org/10.5194/egusphere-egu25-20636, 2025.

For tens of millions of years, up until the late Eocene, Afro-Arabia was subjected to intense chemical weathering under warm and wet climatic conditions. Geodynamic quiescence promoted the development of a widespread carapace of etchplains that capped the stable continent. Starting in the late Eocene, the impingement of the Afar mantle plume on the base of the Afro-Arabian lithosphere resulted in domal uplift across large areas surrounding the Red Sea. The carapace of deeply weathered rocks flexed, eroded, and eventually became incised, facilitating the erosion of underlying pristine rocks. Since at least the early Oligocene, the Afro-Arabian dome has been draining into the Levant Basin of the Eastern Mediterranean, providing the basin with an outstanding sedimentary record of the large-scale uplift. In this study, we evaluate stages in the rise of Afro-Arabia by probing the mineralogical and geochemical properties of Oligocene-Miocene clay recovered from the Levant Basin boreholes. The lower part of the siliciclastic section in the Levant Basin, dating back to 33 Ma, is composed of kaolinite-rich sediments sourced from the weathering and erosion of Neoproterozoic crystalline rocks of the Arabian-Nubian Shield. We interpret them as erosion products of the etchplains that once capped Afro-Arabia and were dismantled during the early stages of mantle-induced domal uplift. Higher up in the siliciclastic section, illite-smectite gradually becomes more prominent at the expense of kaolinite, reflecting further uplift and downcutting into the pristine bedrock. Since the early Miocene, fluvial incision was enhanced by the superimposed effects of regional doming and flexural uplift along the Red Sea Rift margins. By 20-15 Ma, the proportion of illite-smectite surpassed that of kaolinite in the Levant Basin sediments, signifying the substantial elevation of Afro-Arabia and the establishment of high topography. The sedimentary fill of the Levant Basin allows tracking the peeling of the rising continent and offers unique, independent constraints on the uplift process.

How to cite: Glazer, A., Avigad, D., and Morag, N.: Timing the Oligocene-Miocene uplift of Afro-Arabia: Insights from clay mineralogy and geochemistry, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9832, https://doi.org/10.5194/egusphere-egu25-9832, 2025.

Species range limits are typically constrained by their tolerance to abiotic factors such as climate, as well as by dispersal limitations due to geographic barriers like mountain ridges and river valleys. Montane regions, which are hyperdiverse in many different clades, and characterised by high turnover, and complex topography, provide ideal systems for investigating the drivers of range limits. In this study, we collected 30 environmental DNA (eDNA) samples from the tributaries of the Salween, Mekong, and Yangtze rivers and employed ITS2 primers to analyse the species composition of plant and fungal communities. We then quantified and partitioned the relative contributions of geographic and climatic isolation to the assembly of these communities. Our analyses revealed a congruent distribution pattern between plant and fungal groups, with distinct segregation across different river valleys and along latitudes. Habitat preference analyses indicated that our eDNA samples predominantly captured mid-to-low elevation species. The taxonomic composition of plant and fungal communities was jointly influenced by geographic and climatic isolation, although the strength of these influences varied across different groups. Fungal communities were more strongly affected by geographic isolation, while plant communities were more influenced by the combined constraints of geography and climate. These findings underscore the joint influence of topographic and climatic isolation in shaping community composition, highlighting the importance of environmental filtering and dispersal limitation processes. We conclude that the high biodiversity in montane regions depends on both complex climate and topography and, secondarily, note that riverine environmental DNA provides an efficient approach to understand geological and climatic mechanisms in driving biodiversity patterns in terrestrial clades.

How to cite: Chang, Y., Wang, Y., Zhong, W., Zhang, X., Albouy, C., Zimmermann, N., Willett, S., and Pellissier, L.: Environmental DNA reveals geologic and climatic isolation effects on plant and fungal Communities in the Hengduan Mountains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16343, https://doi.org/10.5194/egusphere-egu25-16343, 2025.

River terraces are common features in landscapes around the world, created through the interaction of erosion and sedimentation processes. Although these terraces are widespread, many aspects of their formation and development remain unclear, especially regarding the mechanisms and conditions that control their evolution. The Guadix/Baza Basin in Andalusia, situated within the Granada UNESCO Geopark, offers a unique natural laboratory for studying these questions. Over time, this basin has undergone substantial geological transformations. Initially, it was a closed depression where sediments from the surrounding mountains accumulated. During the Middle to Late Pleistocene, a river capture event caused the basin to transform into an open river system, leading to the development of several generations of river terraces. These terraces are often associated with calcareous sinter formations found in deeply incised valleys. A key factor in the basin's evolution is its dynamic neotectonic activity. The area is characterized by a complex system of faults, with the Baza Fault acting as a major fault system dividing the research area into two distinct sub-basins.

The aim of our DFG-funded research project is to study the processes that influenced the evolution of the fluvial system after the river capture, with a particular focus on fluvial erosion dynamics. To reconstruct the development of terrace formation, luminescence dating is applied to terrace sediments, while U/Th dating is used for associated calcareous sinter formations. This combination allows the establishment of a chronostratigraphy, providing insights into the rates of erosion and the incision patterns of local rivers.

Our contribution will present an overview of the project’s objectives, outline the applied methods, and discuss initial results, including the first chronostratigraphy of the eastern Baza sub-basin. A key focus will be placed on the influence of tectonic activity on terrace formation and how these forces shaped the development of the regional river network. Preliminary findings suggest that tectonics played a significant role in terrace formation, influencing both the thickness and depositional patterns of sedimentary layers. This, in turn, has implications for the interpretation of dating results, as the tectonic setting directly affects the stratigraphic context and preservation of terrace sequences.

The study highlights the importance of integrating numerical laboratory results with empirical fieldwork. A comprehensive understanding of terrace evolution and sedimentary processes is only achievable when the specific tectonic framework of the study area is carefully considered.

How to cite: Kögler, L., Wolf, D., García Tortosa, F. J., Faust, D., Fuchs, M., and Kolb, T.: The influence of tectonics on river terrace evolution in the Guadix/Baza Basin, Spain, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4398, https://doi.org/10.5194/egusphere-egu25-4398, 2025.

Regions dominated by active fold and thrust belts are prone to the development of new, unstable slopes as deformation progresses. However, studies examining the spatial distribution and behavior of landslides within the Himalayas—one of the world’s most dynamic mountain systems—remain limited. This study presents a detailed landslide inventory for the Sikkim Himalayas, an area marked by vigorous tectonic activity and steep, rugged landscapes. By analyzing satellite imagery, we compiled over 100 large-scale landslides (each exceeding an area of 10⁶ m²), with many of these still exhibiting active movement. We utilized tools such as TopoToolbox to analyze topographic steepness and concavity indices, as well as factors like proximity to rivers and active faults. Additionally, geomorphic indices of active tectonics, lithological variations, and rainfall patterns were integrated to investigate the relationship between landslide distribution and these variables within sub-basins as well as across major thrust zones. In Sikkim, landslides show a pronounced tendency to cluster at higher elevations, specifically in the zone between the Main Central Thrust (MCT) and the South Tibetan Detachment (STD). These events are predominantly concentrated in areas with significant local relief and are closely linked to regions experiencing higher rates of relative tectonic uplift. Moreover, extreme rainfall driven by orographic effects amplifies landslide activity, particularly in regions with steep terrain. The most affected areas include the uppermost, steepest areas of active thrusts (MCT and Main Boundary Thrust) and inclined escarps of deeply incised valleys.

How to cite: Das, S. and Scaringi, G.: Tectonic, lithologic and climate controls on landslide distribution in the Eastern Himalayas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5241, https://doi.org/10.5194/egusphere-egu25-5241, 2025.