TY - JOUR A1 - Falkowski, Sarah A1 - Ehlers, Todd A1 - Madella, Andrea A1 - Glotzbach, Christoph A1 - Georgieva, Viktoria A1 - Strecker, Manfred T1 - Glacial catchment erosion from detrital zircon (U-Th)/He thermochronology BT - Patagonian Andes JF - GR / AGU, American Geophysical Union: Earth surface N2 - Alpine glacial erosion exerts a first-order control on mountain topography and sediment production, but its mechanisms are poorly understood. Observational data capable of testing glacial erosion and transport laws in glacial models are mostly lacking. New insights, however, can be gained from detrital tracer thermochronology. Detrital tracer thermochronology works on the premise that thermochronometer bedrock ages vary systematically with elevation, and that detrital downstream samples can be used to infer the source elevation sectors of sediments. We analyze six new detrital samples of different grain sizes (sand and pebbles) from glacial deposits and the modern river channel integrated with data from 18 previously analyzed bedrock samples from an elevation transect in the Leones Valley, Northern Patagonian Icefield, Chile (46.7 degrees S). We present 622 new detrital zircon (U-Th)/He (ZHe) single-grain analyses and 22 new bedrock ZHe analyses for two of the bedrock samples to determine age reproducibility. Results suggest that glacial erosion was focused at and below the Last Glacial Maximum and neoglacial equilibrium line altitudes, supporting previous modeling studies. Furthermore, grain age distributions from different grain sizes (sand, pebbles) might indicate differences in erosion mechanisms, including mass movements at steep glacial valley walls. Finally, our results highlight complications and opportunities in assessing glacigenic environments, such as dynamics of sediment production, transport, transient storage, and final deposition, that arise from settings with large glacio-fluvial catchments. KW - ZHe tracer thermochronology KW - glacial erosion KW - sediment production KW - grain KW - size fractions KW - Leones Glacier KW - Northern Patagonian Icefield Y1 - 2021 U6 - https://doi.org/10.1029/2021JF006141 SN - 2169-9003 SN - 2169-9011 VL - 126 IS - 10 PB - Wiley CY - Hoboken, NJ ER - TY - JOUR A1 - Freisleben, Roland A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Miguel Martinez, Jose A1 - Strecker, Manfred T1 - Marine terraces of the last interglacial period along the Pacific coast of South America (1 degrees N-40 degrees S) JF - Earth system science data : ESSD N2 - Tectonically active coasts are dynamic environments characterized by the presence of multiple marine terraces formed by the combined effects of wave erosion, tectonic uplift, and sea-level oscillations at glacialcycle timescales. Well-preserved erosional terraces from the last interglacial sea-level highstand are ideal marker horizons for reconstructing past sea-level positions and calculating vertical displacement rates. We carried out an almost continuous mapping of the last interglacial marine terrace along similar to 5000 km of the western coast of South America between 1 degrees N and 40 degrees S. We used quantitatively replicable approaches constrained by published terrace-age estimates to ultimately compare elevations and patterns of uplifted terraces with tectonic and climatic parameters in order to evaluate the controlling mechanisms for the formation and preservation of marine terraces and crustal deformation. Uncertainties were estimated on the basis of measurement errors and the distance from referencing points. Overall, our results indicate a median elevation of 30.1 m, which would imply a median uplift rate of 0.22 m kyr(-1) averaged over the past similar to 125 kyr. The patterns of terrace elevation and uplift rate display high-amplitude (similar to 100-200 m) and long-wavelength (similar to 10(2) km) structures at the Manta Peninsula (Ecuador), the San Juan de Marcona area (central Peru), and the Arauco Peninsula (south-central Chile). Medium-wavelength structures occur at the Mejillones Peninsula and Topocalma in Chile, while short-wavelength (< 10 km) features are for instance located near Los Vilos, Valparaiso, and Carranza, Chile. We interpret the long-wavelength deformation to be controlled by deep-seated processes at the plate interface such as the subduction of major bathymetric anomalies like the Nazca and Carnegie ridges. In contrast, short-wavelength deformation may be primarily controlled by sources in the upper plate such as crustal faulting, which, however, may also be associated with the subduction of topographically less pronounced bathymetric anomalies. Latitudinal differences in climate additionally control the formation and preservation of marine terraces. Based on our synopsis we propose that increasing wave height and tidal range result in enhanced erosion and morphologically well-defined marine terraces in south-central Chile. Our study emphasizes the importance of using systematic measurements and uniform, quantitative methodologies to characterize and correctly interpret marine terraces at regional scales, especially if they are used to unravel the tectonic and climatic forcing mechanisms of their formation. This database is an integral part of the World Atlas of Last Interglacial Shorelines (WALIS), published online at https://doi.org/10.5281/zenodo.4309748 (Freisleben et al., 2020). Y1 - 2021 U6 - https://doi.org/10.5194/essd-13-2487-2021 SN - 1866-3508 SN - 1866-3516 VL - 13 IS - 6 SP - 2487 EP - 2513 PB - Copernics Publications CY - Katlenburg-Lindau ER - TY - JOUR A1 - Richter, Maximilian A1 - Brune, Sascha A1 - Riedl, Simon A1 - Glerum, Anne A1 - Neuharth, Derek A1 - Strecker, Manfred T1 - Controls on asymmetric rift dynamics BT - Numerical modeling of strain localization and fault evolution in the Kenya Rift JF - Tectonics / American Geophysical Union, AGU ; European Geophysical Society, EGS N2 - Complex, time-dependent, and asymmetric rift geometries are observed throughout the East African Rift System (EARS) and are well documented, for instance, in the Kenya Rift. To unravel asymmetric rifting processes in this region, we conduct 2D geodynamic models. We use the finite element software ASPECT employing visco-plastic rheologies, mesh-refinement, distributed random noise seeding, and a free surface. In contrast to many previous numerical modeling studies that aimed at understanding final rifted margin symmetry, we explicitly focus on initial rifting stages to assess geodynamic controls on strain localization and fault evolution. We thereby link to geological and geophysical observations from the Southern and Central Kenya Rift. Our models suggest a three-stage early rift evolution that dynamically bridges previously inferred fault-configuration phases of the eastern EARS branch: (1) accommodation of initial strain localization by a single border fault and flexure of the hanging-wall crust, (2) faulting in the hanging-wall and increasing upper-crustal faulting in the rift-basin center, and (3) loss of pronounced early stage asymmetry prior to basinward localization of deformation. This evolution may provide a template for understanding early extensional faulting in other branches of the East African Rift and in asymmetric rifts worldwide. By modifying the initial random noise distribution that approximates small-scale tectonic inheritance, we show that a spectrum of first-order fault configurations with variable symmetry can be produced in models with an otherwise identical setup. This approach sheds new light on along-strike rift variability controls in active asymmetric rifts and proximal rifted margins. KW - asymmetric rifting KW - rift variability KW - numerical model KW - structural KW - inheritance KW - Kenya Rift Y1 - 2021 U6 - https://doi.org/10.1029/2020TC006553 SN - 0278-7407 SN - 1944-9194 VL - 40 IS - 5 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Riller, Ulrich A1 - Giambiagi, Laura A1 - Strecker, Manfred T1 - From proterozoic tectonics to quaternary climate variability BT - earth system science studies in Latin America JF - International journal of earth sciences Y1 - 2021 U6 - https://doi.org/10.1007/s00531-021-02095-9 SN - 1437-3254 SN - 1437-3262 VL - 110 IS - 7 SP - 2269 EP - 2271 PB - Springer CY - Berlin ; Heidelberg ER - TY - JOUR A1 - Müting, Friederike Ariane A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Identification of debris-flow channels using high-resolution topographic data BT - a case study in the Quebrada del Toro, NW Argentina JF - Journal of geophysical research : JGR, Earth surface N2 - Resolving Earth's surface at the meter scale is essential for an improved understanding of the dynamics of mass-movement processes. In this study, we explore the applicability and potential of digital elevation models (DEMs) derived from stereophotogrammetry to detect debris-flow channels in the Quebrada del Toro in the northwestern Argentine Andes. Our analysis relies on a high-resolution (3 m) DEM created from SPOT-7 tri-stereo satellite data. We carefully validated DEM quality with ∼6,000 differential GPS points and identified optimal parameters for DEM generation in high-relief terrain. After multiple processing steps, we achieved an accuracy of 0.051 ± 1.915 m (1σ) using n = 3,139 control points with cm precision. Previous studies have used the drainage area and slope framework to identify topographic signatures of debris flows within a catchment. We built upon this and investigated individual river-channel segments using connected-component (CC) analysis on meter-scale topographic data. We define CC as segments of similar slope along the channel profile. Based on seven manually identified debris-flow catchments, we developed a debris-flow similarity index using component length and mean channel-segment slope and identified channel segments that have likely been shaped by debris flows. The presented approach has the potential to resolve intra-catchment variability of transport processes, allows to constrain the extent of debris-flow channels more precisely than slope-area analysis, and highlights the versatility of combined space- and field-based observations for natural-hazard assessments. Y1 - 2021 U6 - https://doi.org/10.1029/2021JF006330 SN - 2169-9003 SN - 2169-9011 VL - 126 IS - 12 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Savi, Sara A1 - Comiti, Francesco A1 - Strecker, Manfred T1 - Pronounced increase in slope instability linked to global warming BT - a case study from the eastern European Alps JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - In recent decades, slope instability in high-mountain regions has often been linked to increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small- to medium-sized mass movements in a high-elevation catchment of the Italian Alps (Sulden/Solda basin). We found that slope-failure events (mostly in the form of rockfalls) have increased since the 2000s, whereas the occurrence of debris flows has increased only since 2010. The current climate-warming trend registered in the study area apparently increases the elevation of rockfall-detachment areas by approximately 300 m, mostly controlled by the combined effects of frost-cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity-duration rainfall distribution. Potential debris-flow events in this environment may additionally be influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden/Solda basin (above ca. 2500 m above sea level [a.s.l.]), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 2000s, and that an increase in rockfalls and debris flows during spring and summer can be inferred. Our study thus confirms that "forward-looking" hazard mapping should be undertaken in these increasingly frequented, high-elevation areas of the Alps, as environmental change has elevated the overall hazard level in these regions. KW - debris flows KW - frost‐ cracking KW - multi‐ temporal analyses KW - permafrost KW - rainfall events KW - rockfalls KW - temperature extremes Y1 - 2021 U6 - https://doi.org/10.1002/esp.5100 SN - 0197-9337 SN - 1096-9837 VL - 46 IS - 7 SP - 1328 EP - 1347 PB - Wiley CY - New York ER -