For over a century, geologists have vigorously debated the influence of mountains on global climate via links among rock uplift, erosion, chemical weathering, and the geological carbon cycle. For decades, the focus has been on the role of mountain building in drawing down atmospheric carbon dioxide (CO₂) via silicate weathering. However, it is now recognized that mountain building and the exhumation of sedimentary rocks can release CO₂ through the oxidation of organic carbon in rocks (rock OC). We quantify this flux at a global scale and show that over geological timescales this source is as important as CO₂ emissions from volcanism.

We explore the controls of mountain erosion on CO₂ release to the atmosphere with a spatially explicit global simulation model that uses empirical constraints on rock OC oxidation flux. We know that erosion is a major control on this flux: rock OC oxidation increases with erosion, up to and greater than erosion rates of ~ 2 mm yr^-1. This contrasts with silicate weathering, where rates are limited by reaction kinetics at high erosion rates. We here constrain the spatial distribution of high erosion rates and their overlap with OC-rich bedrock lithologies. The effect of erodibility of such lithologies means that these are predisposed to high rates of CO₂ release through weathering. Hence our model relies on lithological mapping to constrain the relationship between topography and exhumation rates, and global rock OC stock. We produce a probabilistic rock OC stock map by combining global lithological maps with the USGS Rock Geochemical Database, which includes over 167,000 samples for our analysis. We consider the role of erosion and chemical weathering by using a probabilistic approach that is built on catchment-scale ¹⁰Be denudation rates, while rhenium-based estimates of oxidative weathering intensity and flux from river catchments around the world are used to constrain patterns in rock OC oxidation. To extrapolate the major controls on erosion and weathering we use local slopes derived from 90 m resolution digital elevation model (DEM) data and lithological maps. We combine the erosion, rock chemistry data and weathering intensity estimates to simulate global rock OC weathering rates at a 1 km grid scale via a statistical probability ensemble (Monte Carlo).

We will present the results of our model compilation, including the effect of lithology on erosion, weathering and CO₂ emission rates. We demonstrate that the size of the organic carbon stock in the first 1 m of bedrock is of a similar magnitude to the carbon stock of global soils, and that the emissions of CO₂ from this geological source are as large as the emissions from volcanic degassing. We identify regions of the Earth’s surface where rock OC could emit substantial amounts of CO₂ and provide new constraints on a major natural CO₂ flux derived from the erosion of mountains.

How to cite: Zondervan, J., Hilton, R., Clubb, F., Dellinger, M., Roylands, T., and Ogrič, M.: Mountains as a source of CO2: a global model of erosion, weathering and fossil organic carbon oxidation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6376, https://doi.org/10.5194/egusphere-egu22-6376, 2022.

The topographic formation of large mountains and plateaus significantly impacts regional and global climate. Previous studies demonstrated that major mountain ranges can explain important aspects of synoptic scale climate dynamics and notable features of the climate system, such as the position of the intertropical convergence zone. Quantifying the synergistic climatic effects of the coeval evolution of major mountain ranges fosters a deeper understanding of climate and Earth system dynamics. Furthermore, it helps estimate where (and by how much) a regional climate signal recorded in a geological archive is affected by topographic changes in distant, off-site orogens. In this study, we use ECHAM5-wiso General Circulation Model (GCM) simulations to explore the synergistic global effects of systematically co-varying the height of the Andean and Himalaya-Tibet Plateaus. The simulations are conducted with different topographic evolution scenarios for these orogens, while environmental boundary conditions, such as global ice cover and greenhouse gas concentrations, are kept constant. More specifically, the topographies of the orogens are incrementally reduced by 25% of their current height. This results in 5 topographic scenarios for the Himalaya-Tibet by setting its elevation to 100%, 75%, 50%, 25% and 0% of current values. These are nested in the analogous 5 topographic scenarios for the Andes, resulting in a total of 25 scenarios and GCM simulations. We then conduct an empirical orthogonal functions (EOF) analysis on the pressure fields produced by each of the simulations to track changes in quasi stable pressure systems. Furthermore, we track changes in cross-equatorial atmospheric transport and synoptic scale atmospheric flow. While most of the regional impacts of evolving topographies can be explained by atmospheric lapse rates and physical air flow disruption, global impacts can be explained by changes in surface heat distribution and pressure centres affecting synoptic scale atmospheric flow. We also find that the height of Himalaya-Tibet modifies the impact of Andean topography on northern hemisphere climate, highlighting interhemisphere climate teleconnections between the two orogens. Our results suggest that robust interpretations of climate signals recorded in geological archives in many regions on Earth are only possible when the global climatic effects of the topography of distant, off-site orogens are considered.

How to cite: Mutz, S. G. and Ehlers, T. A.: How the co-evolution of major mountain ranges affects global climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-862, https://doi.org/10.5194/egusphere-egu22-862, 2022.

Normal fault linkage has significant impacts on uplift patterns and erosional processes in extensional regions. However, geomorphic process-based constraints on landscape response to normal fault linkage are still scarce. Here, we use landscape evolution models to examine how a landscape responds to the linkage of two normal faults. The results demonstrate that topography dynamically responds to the changes in uplift patterns that accompany fault linkage. Specifically, our results indicate that after fault linkage, (1) the steepest topography and the highest erosion rate shift from the center of each fault segment to the linkage zone; and (2) the main drainage divide evolves from an M-shape to a bow shape. We apply these findings to the Langshan Mountains in northern China, and suggest that the two piedmont fault segments have linked and that a high geohazard risk exists near the linkage zone, where the steep, transient topography is experiencing intense erosion.

How to cite: He, C., Yang, C.-J., Rao, G., Roda-Boluda, D. C., Yuan, X., Yang, R., Gao, L., and Zhang, L.: Landscape response to the linkage of two normal faults, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1311, https://doi.org/10.5194/egusphere-egu22-1311, 2022.

Despite decades of controversy, our understanding of the formation of the Tibetan Plateau remains limited. The role of competing mechanisms, such as distributed crustal thickening versus lateral propagation of thrust faulting at crustal or lithospheric scales, is still poorly understood. Conceptual models explaining observations at the continental scale are based on hypotheses that are hard to reconcile, on the one hand buoyancy forces dominating with low influence of upper crustal faulting, on the other hand faults dominating by favour discrete propagation of rigid upper crustal thickening since the onset of collision at ~50 Ma. However, in view of the 3D nature and temporal complexity of the involved deformation processes, no numerical model taking into account the role of strike-slip faults in accommodating stepwise evolution of thrust faulting, as well as the interaction between the deep crust and the surface, has yet been implemented. Therefore, it remains difficult to test the mechanical and rheological consistency, and the ability to explain observations, of end-member conceptual models at the scale of the Tibetan Plateau.

In order to generate new insights in deformation modes in Tibet, I will present models to study the mechanical behaviour in the lower crust of the upper crustal thrust faults observed along the Tibet eastern edge, which setup is based upon recent thermo-kinematic modelling of thermochronology data (Pitard et al., 2021). During the PhD of Paul Pitard, in collaboration with Cédric Thieulot and Marie-Pierre Doin, we made schematic 2-D viscous models of thrusts embedded in the crust, to study eastern Tibet thrust activity in the building of the topography through time. We show that both the high viscosity upper crust in which the fault is embedded and more surprisingly the low viscosity lower crust with no fault, are driven toward the surface by the fault. This generates along the fault a parallel zonation of the vertical velocity field, with high velocities close to the fault, decreasing away from it, fitting well the rejuvenation of cooling ages observed toward the thrust of SE Tibet.

In order to explore the influence of erosion during the building of the plateau, I will also present thermo-kinematic modelling of thermochronology data along the Mekong River at the eastern edge of Tibet, including schematic erosion process (Ou et al., 2020). During the PhD of Xiong Ou, in collaboration with Pieter van der Beek, we estimated that the Mekong River incision, locally more than 2000m, is 25-30% of the total exhumation since 10 Ma. Strong differences in elevation and relief on both sides of the Mekong River are linked to strongly differing tectonic imprint, with high elevation low relief surfaces observed when tectonic imprint is low, in part due to glacial “buzzsaw-like” processes, and high elevation high relief massif observed when tectonic imprint is high and when glacial processes are not sufficient to erase the topography created.

How to cite: Replumaz, A.: Building the Tibetan orogenic plateau : the role of thrust faults and the influence of erosion on the eastern edge., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2037, https://doi.org/10.5194/egusphere-egu22-2037, 2022.

Marine terraces are preserved along the coast when their uplift rate overcomes the rate of sea level increase. Generally, if the relative sea level history is known, elevation and age of marine terraces can be used to quantify the average uplift rate.

At subduction margins, large-scale topography of the fore-arc is the result of complex subduction mechanisms. The existence of uplifted marine terraces along fore-arc coastal areas indicates that the topography is subject to long-term permanent uplift. However, it is yet not known when this permanent uplift is accommodated. Geodetic observations show that, of the total deformation occurring during the megathrust earthquake cycle, only a minimal part (<10-20%) is translated into permanent vertical deformation of the topography. Additionally, particularly high uplift rates (~1 mm/yr) of fore-arcs observed geodetically, or geologically using uplifted marine terraces, suggest the existence of uplift transients or pulses that seem to reflect earthquake clustering on upper plate faults lasting 10 to 100 kyrs, while underplating cycles deduced from field observations and derived from numerical models occur at time scales from 0.5 to 6 Myrs.

We use numerical models to investigate whether different uplift styles are reflected in the geometry of the marine terraces sequences. In particular, we aim at spotting the occurrence of diagnostic patterns representative of different uplift ‘modes’: constant uplift rate, uplift by earthquake pulses (permanent uplift only), or uplift resulting from interseismic and coseismic vertical displacements. The results show that the variability of the terrace staircase morphology subject to different uplift modes increases with the earthquake recurrence time. Preliminary comparison with natural case studies displaying an analogue variability confirms our argument.

How to cite: Crosetto, S., de Montserrat, A., and Oncken, O.: Terraces response to different uplift modes at subduction margins: a forward modelling approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3592, https://doi.org/10.5194/egusphere-egu22-3592, 2022.

Active faults play a major role in relief building, partly through the accumulation of vertical co seismic displacement during major earthquakes. Triangular facets are geomorphic features recording normal fault cumulative displacements on relatively long time scales (10-100ka). To unravel the relationships between the rate at which slip accumulates on a fault scarp and the long-term evolution of triangular facets, we have to acquire quantitative datasets on normal fault slip rates at various timescales and rates of erosion of the facets.

Here we present a study on facet build-up over 10-100 ka time range in the central Apennines in Italy. The normal fault systems that control the present tectonic activity of the range are very well studied with numerous detailed paleoseismological records. We focus on the Magnola-Velino fault system which displays well preserved triangular facets and accurate chronological constraints on the 10-20m high fault scarp located at the base of the facets. We combine high resolution morphometric analysis (gullies steepness, facets slope and others), using Digital Elevation Models derived from Pléiades imagery and a new dataset for cosmogenic nuclides concentration (³⁶Cl) including 54 bedrock samples on 9 gullies and facets profiles above the scarps. Magnola-Velino fault system is 20-25km long, and morphometric parameters such as steepness index display a systematic evolution along strike. First measured ³⁶Cl concentrations, on Magnola, range from 6 to 50 x10⁴ at/g on gullies and 50 to 150 x10⁴ at/g on facets, with systematic variations along strike. We document the joint evolution of geochronological data and morphological parameters for this fault system and compare it with existing constraints on long-term slip rate.

How to cite: Desormeaux, C., Godard, V., Benedetti, L., and Fleury, J.: Comparison of normal fault slip to long-term landscape building. Insights from morphometry analysis and geochronological data on the Magnola-Velino fault system (central Apennines, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4793, https://doi.org/10.5194/egusphere-egu22-4793, 2022.

Drainage divide migration has drawn growing attention in recent years because it can induce changes in drainage areas and confound inference of spatial or temporal changes in tectonic or climatic forcing from river profiles. Recent studies have used different metrics of divide stability, such as cross-divide contrasts in topography, to quantify a divide’s susceptibility to migration. These metrics are based on expectations of cross-divide differences in fluvial or hillslope erosion rates, yet glacial erosion may be the primary driver of topographic evolution and drainage reorganization in many mid-latitude mountain ranges. Here we report a case study in the northeastern Qilian Shan, a northwest-southeast-trending mountain belt on the northeast margin of the Tibetan Plateau. The northeast-facing range front in Qilian Shan today receives less solar insolation but more summer monsoonal precipitation than the southwest-facing front and thus hosts more small, high elevation valley glaciers. We quantify cross-divide contrasts in topography using different metrics and find stronger glacial modification of topography on northeast-facing slopes than on southwest-facing slopes. The northeast-facing range front displays oversteepened U-shaped valleys and evidence of extensive Quaternary glaciation, whereas the southwest-facing front is incised by V-shaped valleys that hosted only small Quaternary glaciers. Near the drainage divide, valleys on the northeast-facing front have steeper headwalls and higher headwall relief than valleys on the southwest-facing front. Based on these observations, we proposed a conceptual model of divide migration in the northeastern Qilian Shan: during the last glacial period, strong glacial modification on the northeast-facing range front caused headward expansion of valleys and drove southwestward divide migration. Since the onset of the present interglacial period, faster postglacial hillslope processes in northeast-facing valleys have sustained this southwestward divide migration. We develop a numerical model to test this conceptual model and discuss the impact of Quaternary glaciation on drainage reorganization in the Qilian Shan. We suggest that Quaternary glaciation and following postglacial adjustment have important impacts on divide migration and drainage reorganization in mid-latitude mountain ranges.

How to cite: Lai, J. and Huppert, K.: Cross-divide topographic contrasts created by asymmetrical glaciation: A case study from the northeastern Qilian Shan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5535, https://doi.org/10.5194/egusphere-egu22-5535, 2022.

In many mountainous regions on Earth, strong spatial variations in uplift with a fault-bounded transition from uplift to subsidence drive the coevolution of high mountain topography and adjacent low-lying basins. In this study, we investigate which topographic patterns are characteristic for such a geodynamic setting where actively subsiding and uplifting regions in direct vicinity are tightly linked via dynamically evolving drainage systems. The Huashan Mountains, which is part of the Qinling Mountains range, and the adjacent Weihe Graben close to the city of Xi’an (China) are the perfect locations to investigate the formation of topography in an active basin and range system, and this area links directly to the uplift of the Tibet plateau. The Weihe Graben formed in an extensional environment and experienced significant subsidence with up to ∼7000m Cenozoic sediments. Contemporaneously, topography has formed in the Huashan Mountains bordering the Weihe Graben. Major earthquakes in this region (e.g. the M∼8.5 Huaxian earthquake in the year 1556), pristine fault scarps, bedrock fractures, and loess crevices are evidence for recent tectonic activity. The high relief between the Huashan Mountains and the Weihe Graben favors fluvial bedrock incision and related mass wasting at hillslopes as a response to local relief formation. Frequent landslides triggered by both seismic and storm events are distributed throughout the Huashan Mountains. To quantify the impact of gradients in uplift rate on topography and active tectonics, we applied several DEM-based morphological analyses and compared catchments that drain north to the low-lying Weihe Graben with those that drain south, which were not affected by tectonically induced base level lowering. We analyzed longitudinal channel profiles, channel steepness (k_sn), catchment hypsometry, and geophysical relief. To quantify the topographic state of the Huashan Mountains and detect drainage divides that are potentially mobile, we computed χ maps and χ-profiles of these drainage systems. We found that rivers at the northern steep slope of the Huashan Mountains, which is directed towards the Weihe Graben, are in general steeper with a higher valley relief, and feature lower χ value compared to rivers south of the drainage divide. Large across divide gradients in χ could indicate a southward migration of the watershed. Analyzing the drainage pattern close to the watershed, we found strong evidence for two river piracy events (wind gaps, beheaded rivers) suggesting that catchments north of the drainage divide indeed grow at the expense of those in the south. We conclude that the evolution of high, tectonically-driven relief in the Huashan - Weihe region with rising mountain ranges and subsiding basins in direct vicinity causes a state of morphological disequilibrium, where the observed reorganization of the drainage system represents the adjustment towards a morphological steady state. We suggest that strong gradients in uplift rate between Huashan Mountains and adjacent Weihe Graben, and their link via dynamic drainage systems control channel and hillslope morphology, the topology of the drainage system, eventually the overall architecture of the orogen, and to the creation of morphology related to the uplift of the Tibet plateau.

How to cite: Duan, M., Robl, J., Neubauer, F., Zhou, X., Liebl, M., and Argentin, A.-L.: River reorganization based on geomorphic indices in the Huashan Mountains, central China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5696, https://doi.org/10.5194/egusphere-egu22-5696, 2022.

In actively deforming regions, the geometry and evolution of fluvial systems are sensitive to surface uplift, style of deformation and erosion processes. The uplift influences drainages via base level changes, drainage reversals, and capture processes. Although drainage development and reorganization might be complex in some cases, it can be used to unravel the tectonic evolution of a region.

The Middle Atlas is an intracontinental fold-and-thrust belt that results from the tectonic inversion of a Triassic to Jurassic continental rift basin. The compressional regime leading to basin inversion has produced limited crustal shortening and thickening in association with the growth of mountain ridges with a wavelength of few km.  These topographic features have been superimposed by a long-wavelength, mantle-driven surface uplift, occurred since the late Cenozoic.

Here, we carry out a topographic and fluvial analysis to investigate at which extent the geomorphic features, mainly the drainage network, reflect the tectonic evolution of the Middle Atlas. Two main drainage divides can be defined in the Middle Atlas: 1) a longitudinal divide that separates an eastern flank draining into the Mediterranean Sea through the Moulouya river from a western flank draining into the Atlantic Ocean through the Sebou and Oum Rbia rivers; 2) a transverse divide that sets apart the catchments of the Sebou and Oum Rbia  rivers. In the eastern flank, where the slopes are steep, the tributaries of the Moulouya river show a parallel pattern and are transversal to the trend of the orogen, whereas in the western flank the rivers are longitudinal and controlled by the tectonic structures. Our results indicate that the topography and drainage are in a disequilibrium condition and in an early stage of evolution. The discrepancy in the rivers network between the two flanks, suggests an asymmetric tectonic uplift history. Specifically the eastern flank of the orogen appears to have accommodated a higher magnitude of late Cenozoic contractional deformation than the western flank

How to cite: Yaaqoub, A., Essaifi, A., Clementucci, R., Ballato, P., and Faccenna, C.: Drainage network as an indicator of tectonic evolution of mountain belts: insight from the Middle Atlas (Morocco)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6048, https://doi.org/10.5194/egusphere-egu22-6048, 2022.

Here we prove the usefulness of applying morphometric analyses, typically used in basin-border faults, to evaluate the geomorphic expression of an intrabasinal structure. The target fault of our study is the Galera Fault, a SW-NE, ca. 30 km-long fault located in the Guadix-Baza Basin (central Betic Cordillera, southern Spain). This fault is characterized by low displacement rates, with a major left-lateral (0.5±0.3 mm/yr) and minor (0.02-0.05 mm/yr) vertical slip components. Moreover, the Galera Fault cuts across the Plio-Quaternary basin infilling, so poorly-lithified sedimentary rocks crop out in both fault blocks.

Since the Guadix-Baza Basin was captured in the Middle Pleistocene, it has been dominated by extensive erosion, which has shaped a very young landscape influenced by the activity of the Galera Fault. To evaluate the imprint of the fault on the landscape, we carried out an analysis of the topography and the drainage network from high-resolution digital elevation models (DEMs). In addition, we apply different geomorphic indices, such as the profile relief ratio (PRR), the normalized channel steepness index (ksn), the asymmetry factor (AF), and the valley floor width-to height ratio (Vf).

Our study evidence that the combination of low slip rates and the high erodibility of the juxtaposed rocks favors a rapid landscape response to fault displacement that erases many landscape effects related to active tectonics. This masking is more effective on features generated by strike-slip displacement, leaving only subtle evidence, such as local stream deflections and upstream widening of catchments. In contrast, geomorphic effects related to vertical displacement are better preserved, including the control of the geometry of the main rivers and morphological differences in the drainage network between the two fault blocks. On the upthrown block, streams are generally shorter, steeper and valley incision is more accentuated. These differences between fault blocks are reflected in the development of an impressive badland landscape that is restricted to the upthrown block.

Slow intrabasinal faults can be difficult to detect in studies involving structural mapping, seismic hazard assessment, or exploration of resources, especially when they offset highly erodible deposits and do not present a marked uplift. However, here we demonstrate that the geomorphic anomalies that these structures can leave on the landscape can be identified by applying a proper morphometric analysis.

How to cite: Medina-Cascales, I., García-Tortosa, F. J., Martín-Rojas, I., Pérez-Peña, J. V., and Alfaro, P.: The usefulness of applying morphometric analyses in intrabasinal faults: the Galera Fault (central Betic Cordillera, S Spain), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6143, https://doi.org/10.5194/egusphere-egu22-6143, 2022.

The exhumation of bedrock is controlled by the interplay between tectonics, surface processes and climate. The highest exhumation rates of cm/yr are recorded in zones of highly active tectonic convergence such as the southern Alps of New Zealand or Himalayan syntaxes, where high rock uplift rates combine with very active surface processes. Here, we use a combination of different thermochronometric systems, and notably trapped-charge thermochronometery, to show that such rates also occur in the Hida Range, Japanese Alps. Our results imply that cm/yr rates of exhumation may be more common than previously thought.

The Hida Range is the most northern and most extensive of the Japanese Alps, and reaches elevations of up to 3000 m a.s.l. The Hida Range is thought to have uplifted in the last 3 Myr in response to E-W compression and magmatism. Our study focuses on samples from the Kurobe gorge, which is one of the steepest gorges in Japan. Previous work has shown that exhumation rates in this region are exceptionally high, as documented by the exposure of the ~0.8 Ma Kurobe granite (Ito et al., 2013) in the gorge. We combined 12 new zircon (U-Th/He) ages and 11 new OSL-thermochronometry ages together with existing thermochronometric data to investigate the late Pleistocene exhumation of this region.

We found that exhumation rates increased to ~10 mm/yr within the past 300 kyr, likely in response to river base-level fall that increased channel steepness due to climatically controlled eustatic changes. Our thermochronometry data allow the development of time-series of exhumation rate changes at the timescale of glacial-interglacial cycles and show a four-fold increase in baseline rates over the past ~65 kyr. This increase in exhumation rate is likely explained by knickpoint propagation due to a combination of very high precipitation rates, climatic change, sea-level fall, range-front faulting and moderate rock uplift. Our data show that in regions with horizontal convergence, coupling between climate, surface processes and tectonics can exert a significant effect on rates of exhumation.

References

Ito, H., Yamada, R., Tamura, A., Arai, S., Horie, K., Hokada T., 2013. Earth’s youngest exposed granite and its tectonic implications: the 10-0.8 Ma Kurobegawa Granite. Scientific Reports 3: 1306.

How to cite: King, G., Ahadi, F., Sueoka, S., Herman, F., Anderson, L., Gautheron, C., Tsukamoto, S., Stalder, N., Biswas, R., Fox, M., Delpech, G., Scharwtz, S., and Tagami, T.: Eustatic change modulates exhumation in the Japanese Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7337, https://doi.org/10.5194/egusphere-egu22-7337, 2022.

Landscape evolution models simulate erosional and depositional changes in terrain surface over time and have proven useful for studying surface processes at a variety of scales. These models rely on several input parameters such as a coefficient of hillslope diffusion (D), as well as stream power exponents of drainage basin area (m) and slope (n), a value of minimum drainage area (Ac) below which advective fluvial processes dominate over diffusive hillslope processes, and an effective stream power/advection coefficient of rock ‘erodibility’ (k). In spite of the widespread application of landscape evolution models, values of these input parameters and their variation through space and time are generally poorly constrained in large part due to the large number of processes and physical properties which are amalgamated into the advection-based SP equation. Several recent studies have looked at global controls on erosion rates using stream power parameters and other river metrics by making use of sophisticated stream profile analysis tools, and we aim to build on these past studies by using a landscape evolution modelling framework.  Here, we make use of a global catalog of basin-averaged cosmogenic 10Be-derived apparent erosion rates to tune several landscape evolution model parameters. We employ an Approximate Bayesian Computation (ABC) approach which is based on the performance of many combinations of randomly selected parameters with respect to a likelihood function that measures how well a model fits a sample of observations for a given set of parameter values. Prescribing the commonly observed stream concavity ratio (m/n) of 0.5, maximum agreement between LEM-predicted and 10Be apparent erosion rates is obtained when the free parameters of stream power slope coefficient (n) is approximately 2, the ratio of hillslope diffusivity (D) to effective stream power coefficient (K) is between 103 and 104 mn-1 yr-1 and when critical drainage area (Ac) is ~0.1 km2. Additionally, we find that models can be optimized to a greater degree when the diffusive component of the LEMs is squared, in line with recent studies. Finally, we perform a search for optimal parameters in the face of variable stream concavity, climate, and geology which are encompassed in k, D, m, and n,  all of which show considerable variability over different climatic, lithologic, and ecologic regimes. Ultimately, this demonstrates that globally optimal parameters may not be applicable at the local to regional scale, but continent to global scale analyses could benefit from understanding these optimal parameters.

How to cite: Ruetenik, G., Jansen, J., and Val, P.: Understanding landscape evolution parameters using global 10Be erosion rates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8123, https://doi.org/10.5194/egusphere-egu22-8123, 2022.

The tectosedimentary evolution of the Pyrenees is a well-known example of the interaction among growth strata, sediment routing, sequence stratigraphy and evolving depositional environments. During the Late Cretaceous a general tectonic inversion from rift to foreland basin is recorded. Such evolution is related to the Iberian plate kinematics and is evidenced by the substitution of carbonate systems by mixed and clastic ones, that will persist until Oligocene times.

The precise evolution and timing of the inversion stages is addressed by studying the Noguera Pallaresa river transect (composite Collegats -Font de la Plata section) which is further compared with other areas. This classical transect also permits to study successive structure reactivations after inversion started. Robust magnetostratigraphic results from several stratigraphic units (Font de les Bagasses marls, Riu Boix platform or Montsec sands) permit an accurate dating of the beginning of the inversion stage within the Santonian and also provide time constraints (together with absolute datings) for the rest of the Late Cretaceous. The role of the Montsec thrust as paleohigh controlling basin partitioning is also evidenced by a large paleocurrent database obtained from the Areny sandstone formation. Sedimentological data and carbonate microfacies determinations also provide refinements of the complex interaction between tectonic and climatic factors.

Finally, the combined biomagnetostratigraphic age model is compared with the peripheral areas of the foreland such as Serres Marginals, Eastern and Northern Pyrenees. It is strongly suggested that the formation of accommodation space for sedimentation due to the inversion was fully synchronous all over the orogen.

How to cite: Oms, O., Dinarès-Turell, J., Vicens, E., Boix, C., Gil-Gil, J., García-Hidalgo, J., and Ramírez-Pérez, P.: Sedimentary record of tectonic inversion and basin partitioning in the South-Central Pyrenees during the Late Cretaceous., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8794, https://doi.org/10.5194/egusphere-egu22-8794, 2022.

It is widely recognized that mountain belt topography is generated by crustal thickening and lowered by river incision, linking climate and tectonics. However, it remains enigmatic whether surface processes or lithospheric strength control mountain belt height, width, and longevity, reconciling high erosion rates observed for instance in Taiwan and New Zealand and low erosion rates in the Tibetan and Andean plateaus, as well as long-term survival of mountain belts for several 100s of million years as observed in the Urals and Appalachians. Here we use a tight coupling between a landscape evolution model (FastScape) and a thermo-mechanically coupled mantle-scale tectonic model (Fantom) to investigate mountain belt growth and decay. Using several end-member models and introducing the new non-dimensional Beaumont number, Bm, we quantify how surface processes and tectonics control mountain growth and define three end-member types of growing orogens: Type 1, non-steady state, strength controlled; Type 2, flux steady state, strength controlled; and Type 3, flux steady state, erosion controlled. Orogenic decay is determined by erosional efficiency and can be subdivided into two phases with variable isostatic rebound characteristics and associated timescales: First short-wavelength relief is removed within a few Myr, followed by removal of long-wavelength topography and effectively local isostatic rebound. Comparing model and scaling results to natural orogens explains why different orogens on Earth are rheology or erosion- (climate)-limited, and why long-term survival of topography seems to be the norm rather than the exception.

How to cite: Wolf, S. G., Huismans, R. S., Braun, J., and Yuan, X.: Quantifying the growth and decay of topography in collisional orogens , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8815, https://doi.org/10.5194/egusphere-egu22-8815, 2022.

The Eastern Alps hold an abundance of landscapes with noticeably low topographic gradients at higher elevations above much steeper slopes. Many of these elevated low-relief landscapes (ELRL) are organized in distinct surface levels. Sub-horizontal cave systems can often be found at similar elevations. Utilizing spatial statistics of these ELRL and over 15000 caves, we show that the formation of both the surface and sub-surface landscapes is connected and can help deciphering the landscape evolution of the Eastern Alps from the Late Neogene until today. New cosmogenic nuclide data (¹⁰Be, ²¹Ne, ²⁶Al) of allogenic quartzous sediments from caves and surfaces of distinct elevation levels in the Eastern Alps are used to quantify the incision and ultimately surface uplift history. Burial ages of cave sediments scatter between 0.5 and over 5 Ma. The preliminary data indicate a mean surface uplift of some 0.15 – 0.25 mm/year for much of the Pliocene. We also show that most ELRL in the Eastern Alps can be interpreted in terms of pre-Pleistocene relict landscapes, especially in the only minorly glaciated eastern part.  However, the data also show some impact of the Pleistocene glacial cycles on the ELRL and the mobilization of sediments associated with them.

How to cite: Gradwohl, G., Stüwe, K., Robl, J., Plan, L., Fabel, D., Stuart, F., Liebl, M., and Di Nicola, L.: Plio-/Pleistocene landscape evolution in the Eastern Alps: new insights from cosmogenic nuclide dating, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9531, https://doi.org/10.5194/egusphere-egu22-9531, 2022.

High-elevation, low-relief surfaces are widespread in many mountain belts. However, the origin of these surfaces has long been debated, with previous studies proposing that they either represent a relict low-relief surface, uplifted and eroded by a wave of upstream incision instigated by a Cenozoic increase in rock uplift, or that they formed by tectonic shortening and consequent drainage reorganization. In particular, the Southeast (SE) Tibetan Plateau has extensive low-relief surfaces perched above deep valleys and in the headwaters of three of the world’s largest rivers (Salween, Mekong and Yangtze). Various geologic data, synthesized low-temperature thermochronologic data, and geodynamic models show that many mountain belts grow first to a certain height and then laterally in an outward propagation sequence. By translating this information into a kinematic propagating uplift function in a landscape evolution model, we propose that the high-elevation, low-relief surfaces in the SE Tibetan Plateau are simply a consequence of mountain growth and do not require a special process to form. The propagating uplift forms an elongated river network geometry with broad high-elevation, low-relief headwaters and interfluves that persist for tens of millions of years, consistent with the observed geochronology. We suggest that the low-relief interfluves can be long-lived because of their unusually/unproportionally small drainage area in comparison with the large mainstem rivers. The propagating uplift also produces spatial and temporal exhumation patterns and river profile morphologies that match observations. Our modeling therefore reconciles geomorphic observations with geodynamic models of uplift of the SE Tibetan Plateau, and provides a simple mechanism to explain low-relief surfaces observed in several mountain belts on Earth.

How to cite: Yuan, X., Huppert, K., Braun, J., Shen, X., Liu-Zeng, J., Guerit, L., Wolf, S., Zhang, J., and Jolivet, M.: Propagating uplift controls on high-elevation, low-relief landscape formation in Southeast Tibetan Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11244, https://doi.org/10.5194/egusphere-egu22-11244, 2022.

The Tokaj Mountain in North eastern Hungary is part of the andesitic and dacitic volcanic arc of the inner Carpathians. The mountain is surrounded by first order strike-slip faults from the W and SE side respectively called as the Hernád Fault and Bodorg Fault. These faults are moderately active today, in the interior of the mountain range. However, there are few rock outcrops indicative of structural movement, but the morphology of the watercourses suggests that the area was more active in the recent past.

The present study aims to examine the link between the actual morphology of the mountain and the major tectonic factors affecting the region. In this regard, a morphometric analysis was performed adopting six indices in order to describ the relative active tectonism of the region based on the method of El Hamdouni et al.(2008). 

The method consists of the analyis of drainage basins and includes the evaluation of the morphometric indices namely: the stream-gradient index (SL), the asymmetry factor (AF), the basin shape ratio (Bs), the hypsometric integral (HI), the ratio of valley floor width to valley height (Vf) and the mountain front sinuosity (Smf). The combination of these parameters could be used to generate the relative tectonic activity index (Iat). A pre-processed SRTM DEM 30m resolution has been used for the watershed delineation, calibrated with open source real stream data. 

The study area covers the entire catchment area of the Hernád River the Tokaj and the Cserehát Mountains devided into six drainage basins. The evaluation result shows a moderate relative tectonic activity, except the eastern side of the mountain, where  the activity is low (flat area). However, there was also a slight difference in activity between the western and eastern sides of the lower Hernád River, and also a remarquable morphological  contrast could be noticed on the bordering areas of Hernád drainage basin. The results are in line with the relatively quiet structural activity currently observed, but further detailed data (well logs, interferometry analysis) and high resolution DEM are needed to reveal the structural characteristics of the Tokaj Mountains.

From the part of G.A. financial support was provided from the NRDI Fund of Hungary, Thematic Excellence Programme no. TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.

Reference:

El Hamdouni et al (2008). Assessment of relative active tectonics, southwest border of the Sierra Nevada (southern Spain), Geomorphology, 96(1-2), 150-173.

How to cite: Ammar, S. and Albert, G.: Tectonic activity assessment using morphometric indices - Tokaj Mountain (Hungary), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12510, https://doi.org/10.5194/egusphere-egu22-12510, 2022.

The strong gradients in climate and tectonics along the Chilean-Argentine Andes offer the perfect opportunity to study wider landscape controls on mountain topography.

Between 33 and 37^oS we observe the largest variability in mountain elevation and erosion rates. For this region, we isolate the tectonic contribution to topography by modelling the mechanical dislocation of the crustal scale faults in response to plate convergence. We then use this spatially variable uplift field to determine to what extent the existing topography records this tectonic signal. While local relief and channel steepness do record responses to faulting on the Chilean side of the cordillera, the broader areas of highest uplift in Argentina have the lowest local relief and channel steepness. We therefore explore how this relationship between tectonics and topography may have been modified by the spatial variability in bedrock lithology, sediment cover and mean annual precipitation. We find that channel steepness does not vary significantly with bedrock lithology but does map onto trends in precipitation and sediment cover. The lowest local relief and channel steepness regions have low precipitation rates and widespread sediment cover, suggesting sediment mobility, modulated by climate, maybe an important control on bedrock incision rates in this high uplift zone. We therefore highlight the importance of climate in the recovery of post-glacial landscapes and the modulatory effect sediment cover can have in the evolution of large scale topography.

How to cite: Harries, R. and Aron, F.: Climate and sediment mobility modulate topography-tectonic link in the Andes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13098, https://doi.org/10.5194/egusphere-egu22-13098, 2022.