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 - Rodriguez Piceda, Constanza A1 - Scheck-Wenderoth, Magdalena A1 - Bott, Judith A1 - Gomez Dacal, Maria Laura A1 - Cacace, Mauro A1 - Pons, Michael A1 - Prezzi, Claudia A1 - Strecker, Manfred T1 - Controls of the Lithospheric Thermal Field of an Ocean-Continent Subduction Zone BT - the Southern Central Andes JF - Lithosphere / Geological Society of America N2 - In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate (i.e., thickness and composition of the rock units) and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29 degrees-39 degrees S). Here, the subduction angle increases from subhorizontal (5 degrees) north of 33 degrees S to steep (similar to 30 degrees) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive thermal modeling. We found that the orogen is overall warmer than the forearc and the foreland and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (<50km depth). Specific conditions are present where the oceanic slab is relatively shallow (<85 km depth) and the radiogenic crust is thin. This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening. Y1 - 2022 U6 - https://doi.org/10.2113/2022/2237272 SN - 1941-8264 SN - 1947-4253 VL - 2022 IS - 1 PB - GeoScienceWorld CY - McLean ER - TY - JOUR A1 - Olen, Stephanie M. A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Corrigendum to: Olen, Stephanie M.; Bookhagen, Bodo; Strecker, Manfred R. : Role of climate and vegetation density in modulating denudation rates in the Himalaya. - Earth and planetary science letters. - 445 (2016), S. 57 - 67. - doi: https://doi.org/10.1016/j.epsl.2016.03.047 JF - Earth and planetary science letters N2 - Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new 10Be denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially- dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W–E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = −0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S–N), along strike of the orogen (i.e., E–W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation Y1 - 2020 U6 - https://doi.org/10.1016/j.epsl.2020.116252 SN - 0012-821X SN - 1385-013X VL - 540 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Erbello Doelesso, Asfaw A1 - Melnick, Daniel A1 - Zeilinger, Gerold A1 - Bookhagen, Bodo A1 - Pingel, Heiko A1 - Strecker, Manfred T1 - Geomorphic expression of a tectonically active rift-transfer zone in southern Ethiopia JF - Geomorphology : an international journal on pure and applied geomorphology N2 - The Gofa Province and the Chew Bahir Basin of southern Ethiopia constitute tectonically active regions, where the Southern Main Ethiopian Rift converges with the Northern Kenya Rift through a wide zone of extensional deformation with several north to northeast-trending, left-stepping en-e & PRIME;chelon basins. This sector of the Southern Main Ethiopian Rift is characterized by a semi-arid climate and a largely uniform lithology, and thus provides ideal conditions for studying the different parameters that define the tectonic and geomorphic features of this complex kinematic transfer zone. In this study, the degree of tectonic activity, spatiotemporal variations in extension, and the nature of kinematic linkage between different fault systems of the transfer zone are constrained by detailed quantitative geomorphic analysis of river catchments and focused field work. We analyzed fluvial and landscape morphometric characteristics in combination with structural, seismicity, and climatic data to better evaluate the tectono-geomorphic history of this transfer zone. Our data reveal significant north-south variations in the degree of extension from the Sawula Basin in the north (mature) to the Chew Bahir Basin in the south (juvenile). First, normalized channel-steepness indices and the spatial arrangement of knickpoints in footwall-draining streams suggest a gradual, southward shift in extensional deformation and recent tectonic activity. Second, based on 1-k(m) radius local relief and mean-hillslope maximum values that are consistent with ksn anomalies, we confirm strain localization within zones of fault interaction. Third, morphometric indices such as hypsometry, basin asymmetry factor, and valley floor width to valley height ratio also indicate a north to south gradient in tectonic activity, highlighting the importance of such a wide transfer zone with diffuse extension linking different rift segments during the break-up of continental crust. KW - rift transfer zone KW - Ethiopia rift KW - renya Rift KW - morphometric indices KW - knickpoints Y1 - 2022 U6 - https://doi.org/10.1016/j.geomorph.2022.108162 SN - 0169-555X SN - 1872-695X VL - 403 PB - Elsevier Science CY - Amsterdam [u.a.] 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 - Riedl, Simon A1 - Melnick, Daniel A1 - Njue, Lucy A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Mid-Pleistocene to recent crustal extension in the inner graben of the Northern Kenya Rift JF - Geochemistry, geophysics, geosystems N2 - Magmatic continental rifts often constitute nascent plate boundaries, yet long-term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time-averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM-X science digital elevation model to evaluate fault-scarp geometries and determine fault throws across the volcano-tectonic axis of the inner graben of the NKR. Along rift-perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new Ar-40/Ar-39 radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time-averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long-term extension rate based on mid-Pleistocene to recent brittle deformation has minimum values of 1.0-1.6 mm yr(-1), locally with values up to 2.0 mm yr(-1). A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20-km-wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano-tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR. KW - extensional tectonics KW - Kenya Rift KW - TanDEM-X DEM KW - DEM analysis KW - geochronology KW - normal faults Y1 - 2022 U6 - https://doi.org/10.1029/2021GC010123 SN - 1525-2027 VL - 23 IS - 3 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Rodriguez Piceda, Constanza A1 - Scheck-Wenderoth, Magdalena A1 - Cacace, Mauro A1 - Bott, Judith A1 - Strecker, Manfred T1 - Long-Term Lithospheric Strength and Upper-Plate Seismicity in the Southern Central Andes, 29 degrees-39 degrees S JF - Geochemistry, geophysics, geosystems N2 - We examined the relationship between the mechanical strength of the lithosphere and the distribution of seismicity within the overriding continental plate of the southern Central Andes (SCA, 29 degrees-39 degrees S), where the oceanic Nazca Plate changes its subduction angle between 33 degrees S and 35 degrees S, from subhorizontal in the north (<5 degrees) to steep in the south (similar to 30 degrees). We computed the long-term lithospheric strength based on an existing 3D model describing variations in thickness, density, and temperature of the main geological units forming the lithosphere of the SCA and adjacent forearc and foreland regions. The comparison between our results and seismicity within the overriding plate (upper-plate seismicity) shows that most of the events occur within the modeled brittle domain of the lithosphere. The depth where the deformation mode switches from brittle frictional to thermally activated ductile creep provides a conservative lower bound to the seismogenic zone in the overriding plate of the study area. We also found that the majority of upper-plate earthquakes occurs within the realm of first-order contrasts in integrated strength (12.7-13.3 log Pam in the Andean orogen vs. 13.5-13.9 log Pam in the forearc and the foreland). Specific conditions characterize the mechanically strong northern foreland of the Andes, where seismicity is likely explained by the effects of slab steepening. KW - subduction zone KW - Andes KW - rheology KW - seismicity KW - flat-slab Y1 - 2022 U6 - https://doi.org/10.1029/2021GC010171 SN - 1525-2027 VL - 23 IS - 3 PB - American Geophysical Union CY - Washington 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 - Montero-Lopez, Carolina A1 - Hongn, Fernando D. A1 - Lopez Steinmetz, Romina L. A1 - Aramayo, Alejandro A1 - Pingel, Heiko A1 - Strecker, Manfred A1 - Cottle, John A1 - Bianchi, Carlos T1 - Development of an incipient Paleogene topography between the present-day Eastern Andean Plateau (Puna) and the Eastern Cordillera, southern Central Andes, NW Argentina JF - Basin research / publ. in conjunction with the European Association of Geoscientists & Engineers and the International Association of Sedimentologists N2 - The structural and topographic evolution of orogenic plateaus is an important research topic because of its impact on atmospheric circulation patterns, the amount and distribution of rainfall, and resulting changes in surface processes. The Puna region in the north-western Argentina (between 13 degrees S and 27 degrees S) is part of the Andean Plateau, which is the world's second largest orogenic plateau. In order to investigate the deformational events responsible for the initial growth of this part of the Andean plateau, we carried out structural and stratigraphic investigations within the present-day transition zone between the northern Puna and the adjacent Eastern Cordillera to the east. This transition zone is characterized by ubiquitous exposures of continental middle Eocene redbeds of the Casa Grande Formation. Our structural mapping, together with a sedimentological analysis of these units and their relationships with the adjacent mountain ranges, has revealed growth structures and unconformities that are indicative of syntectonic deposition. These findings support the notion that tectonic shortening in this part of the Central Andes was already active during the middle Paleogene, and that early Cenozoic deformation in the region that now constitutes the Puna occurred in a spatially irregular manner. The patterns of Paleogene deformation and uplift along the eastern margin of the present-day plateau correspond to an approximately north-south oriented swath of reactivated basement heterogeneities (i.e. zones of mechanical weakness) stemming from regional Paleozoic mountain building that may have led to local concentration of deformation belts. KW - Andean Plateau KW - Eastern Cordillera KW - Eocene deformation KW - growth structures KW - northern Puna KW - north-western Argentina KW - southern Central Andes Y1 - 2020 U6 - https://doi.org/10.1111/bre.12510 SN - 0950-091X SN - 1365-2117 VL - 33 IS - 2 SP - 1194 EP - 1217 PB - Wiley-Blackwell CY - Oxford ER - TY - JOUR A1 - Glerum, Anne A1 - Brune, Sascha A1 - Stamps, D. Sarah A1 - Strecker, Manfred T1 - Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift JF - Nature Communications N2 - The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria's rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria's GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress. One of the largest continental microplates on Earth is situated in the center of the East African Rift System, and oddly, the Victoria microplate rotates counterclockwise with respect to the neighboring African tectonic plate. Here, the authors' modelling results suggest that Victoria microplate rotation is caused by edge-driven lithospheric processes related to the specific geometry of rheologically weak and strong regions. Y1 - 2020 U6 - https://doi.org/10.1038/s41467-020-16176-x SN - 2041-1723 VL - 11 IS - 1 PB - Nature Publishing Group CY - London ER - TY - JOUR A1 - Figueroa Villegas, Sara A1 - Weiss, Jonathan R. A1 - Hongn, Fernando D. A1 - Pingel, Heiko A1 - Escalante, Leonardo A1 - Elías, Leonardo A1 - Aranda-Viana, R. Germán A1 - Strecker, Manfred T1 - Late pleistocene to recent deformation in the thick-skinned fold-and-thrust belt of Northwestern Argentina (Central Calchaqui Valley, 26 degrees S) JF - Tectonics / American Geophysical Union, AGU ; European Geophysical Society, EGS N2 - The thick-skinned fold-and-thrust belt on the eastern flank of the Andean Plateau in northwestern Argentina (NWA) is a zone of active contractional deformation characterized by fault-bounded mountain ranges with no systematic spatiotemporal pattern of tectonic activity. In contrast, the thin-skinned Subandean fold-and-thrust belt of northern Argentina and southern Bolivia is characterized primarily by in-sequence (i.e., west to east) fault progression, with a narrow zone of Quaternary deformation focused at the front of the orogenic wedge. To better understand how recent deformation is accommodated across these mountain ranges and the Argentinian portion of the orogen in particular, estimating and comparing deformation rates and patterns across different timescales is essential. We present Late Pleistocene shortening rates for the central Calchaqui intermontane valley in NWA associated with at least three episodes of deformation. Global Positioning System data for the same region reveal a gradual decrease in horizontal surface velocities from the Eastern Cordillera toward the foreland, which contrasts with the rapid velocity gradient associated with a locked decollement in the Subandean Ranges of southern Bolivia. Our new results represent a small view of regional deformation that, when considered in combination with the shallow crustal seismicity and decadal-scale surface velocities, support the notion that strain release in NWA is associated with numerous slowly deforming structures that are distributed throughout the orogen. Y1 - 2020 U6 - https://doi.org/10.1029/2020TC006394 SN - 0278-7407 SN - 1944-9194 VL - 40 IS - 1 PB - American Geophysical Union CY - Washington, DC 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 - TY - JOUR A1 - Riedl, Simon A1 - Melnick, Daniel A1 - Mibei, Geoffrey K. A1 - Njue, Lucy A1 - Strecker, Manfred T1 - Continental rifting at magmatic centres BT - structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift JF - Journal of the geological society N2 - The structural evolution of calderas in rifts helps to characterize the spatiotemporal relationships between magmatism, long wavelength crustal deformation and the formation of tectonic deformation zones along the rift axis. We document the structural characteristics of the c. 36 ka old Menengai Caldera located within a young zone of extension in the central Kenya Rift. Field mapping and high-resolution digital surface models show that NNE-striking Holocene normal faults perpendicular to the regional ESE-WNWextension direction dominate the interior sectors of the rift. Inside the caldera, these structures are overprinted by post-collapse doming and faulting of the magmatic centre, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the palaeo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin indicate that volcanism and fault activity inside and in the vicinity of Menengai must have been sustained during the Holocene. Our analysis confirms that the caldera is located at the centre of an extending rift segment and suggests that other magmatic centres and young zones of faulting along the volcano-tectonic axis of the Kenya Rift may constitute nucleation points of faulting that ultimately foster future continental break-up. Y1 - 2020 U6 - https://doi.org/10.1144/jgs2019-021 SN - 0016-7649 SN - 2041-479X VL - 177 IS - 1 SP - 153 EP - 169 PB - Geological Soc. Publ. House CY - Bath ER - TY - JOUR A1 - Jara-Muñoz, Julius A1 - Melnick, Daniel A1 - Li, Shaoyang A1 - Socquet, Anne A1 - Cortés-Aranda, Joaquín A1 - Brill, Dominik A1 - Strecker, Manfred T1 - The cryptic seismic potential of the Pichilemu blind fault in Chile revealed by off-fault geomorphology JF - Nature Communications N2 - The first step towards assessing hazards in seismically active regions involves mapping capable faults and estimating their recurrence times. While the mapping of active faults is commonly based on distinct geologic and geomorphic features evident at the surface, mapping blind seismogenic faults is complicated by the absence of on-fault diagnostic features. Here we investigated the Pichilemu Fault in coastal Chile, unknown until it generated a Mw 7.0 earthquake in 2010. The lack of evident surface faulting suggests activity along a partly-hidden blind fault. We used off-fault deformed marine terraces to estimate a fault-slip rate of 0.52 ± 0.04 m/ka, which, when integrated with satellite geodesy suggests a 2.12 ± 0.2 ka recurrence time for Mw~7.0 normal-faulting earthquakes. We propose that extension in the Pichilemu region is associated with stress changes during megathrust earthquakes and accommodated by sporadic slip during upper-plate earthquakes, which has implications for assessing the seismic potential of cryptic faults along convergent margins and elsewhere. Y1 - 2022 U6 - https://doi.org/10.1038/s41467-022-30754-1 SN - 2041-1723 VL - 13 PB - Springer Nature CY - London 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 - Kübler, Simon A1 - Streich, R. A1 - Lück, Erika A1 - Hoffmann, M. A1 - Friedrich, A. M. A1 - Strecker, Manfred T1 - Active faulting in a populated low-strain setting (Lower Rhine Graben, Central Europe) identified by geomorphic, geophysical and geological analysis JF - Seismicity, fault rupture and earthquake hazards in slowly deforming regions N2 - The Lower Rhine Graben (Central Europe) is a prime example of a seismically active low-strain rift zone characterized by pronounced anthropogenic and climatic overprint of structures, and long recurrence intervals of large earthquakes. These factors render the identification of active faults and surface ruptures difficult. We investigated two fault scarps in the Lower Rhine Graben, to decipher their structural character, offset and potential seismogenic origin. Both scarps were modified by anthropogenic activity. The Hemmerich site lies c. 20 km SW of Cologne, along the Erft Fault. The Untermaubach site lies SW of Duren, where the Schafberg Fault projects into the Rur River valley. At the Hemmerich site, geomorphic and geophysical data, as well as exploratory coring reveal evidence of repeated normal faulting. Geophysical analysis and palaeoseismological excavation at the Untermaubach site reveal a complex fault zone in Holocene gravels characterized by subtle gravel deformation. Differentiation of tectonic and fluvial features was only possible with trenching, because fault structures and grain sizes of the sediments were below the resolution of the geophysical data. Despite these issues, our investigation demonstrates that valuable insight into past earthquakes and seismogenic deformation in a low-strain environment can be revealed using a multidisciplinary approach. Y1 - 2017 SN - 978-1-86239-745-3 SN - 978-1-86239-964-8 U6 - https://doi.org/10.1144/SP432.11 SN - 0305-8719 VL - 432 SP - 127 EP - 146 PB - The Geological Society CY - London ER - TY - JOUR A1 - Rodriguez Piceda, Constanza A1 - Scheck Wenderoth, Magdalena A1 - Gomez Dacal, Maria Laura A1 - Bott, Judith A1 - Prezzi, Claudia Beatriz A1 - Strecker, Manfred T1 - Lithospheric density structure of the southern Central Andes constrained by 3D data-integrative gravity modelling JF - International journal of earth sciences N2 - The southern Central Andes (SCA) (between 27 degrees S and 40 degrees S) is bordered to the west by the convergent margin between the continental South American Plate and the oceanic Nazca Plate. The subduction angle along this margin is variable, as is the deformation of the upper plate. Between 33 degrees S and 35 degrees S, the subduction angle of the Nazca plate increases from sub-horizontal (< 5 degrees) in the north to relatively steep (similar to 30 degrees) in the south. The SCA contain inherited lithological and structural heterogeneities within the crust that have been reactivated and overprinted since the onset of subduction and associated Cenozoic deformation within the Andean orogen. The distribution of the deformation within the SCA has often been attributed to the variations in the subduction angle and the reactivation of these inherited heterogeneities. However, the possible influence that the thickness and composition of the continental crust have had on both short-term and long-term deformation of the SCA is yet to be thoroughly investigated. For our investigations, we have derived density distributions and thicknesses for various layers that make up the lithosphere and evaluated their relationships with tectonic events that occurred over the history of the Andean orogeny and, in particular, investigated the short- and long-term nature of the present-day deformation processes. We established a 3D model of lithosphere beneath the orogen and its foreland (29 degrees S-39 degrees S) that is consistent with currently available geological and geophysical data, including the gravity data. The modelled crustal configuration and density distribution reveal spatial relationships with different tectonic domains: the crystalline crust in the orogen (the magmatic arc and the main orogenic wedge) is thicker (similar to 55 km) and less dense (similar to 2900 kg/m(3)) than in the forearc (similar to 35 km, similar to 2975 kg/m(3)) and foreland (similar to 30 km, similar to 3000 kg/m(3)). Crustal thickening in the orogen probably occurred as a result of stacking of low-density domains, while density and thickness variations beneath the forearc and foreland most likely reflect differences in the tectonic evolution of each area following crustal accretion. No clear spatial relationship exists between the density distribution within the lithosphere and previously proposed boundaries of crustal terranes accreted during the early Paleozoic. Areas with ongoing deformation show a spatial correlation with those areas that have the highest topographic gradients and where there are abrupt changes in the average crustal-density contrast. This suggests that the short-term deformation within the interior of the Andean orogen and its foreland is fundamentally influenced by the crustal composition and the relative thickness of different crustal layers. A thicker, denser, and potentially stronger lithosphere beneath the northern part of the SCA foreland is interpreted to have favoured a strong coupling between the Nazca and South American plates, facilitating the development of a sub-horizontal slab. KW - Central andes KW - Lithospheric structure KW - Crustal density KW - Gravity KW - modelling KW - Subduction Y1 - 2020 U6 - https://doi.org/10.1007/s00531-020-01962-1 SN - 1437-3254 SN - 1437-3262 VL - 110 IS - 7 SP - 2333 EP - 2359 PB - Springer CY - New York ER - TY - JOUR A1 - Sippel, Judith A1 - Meessen, Christian A1 - Cacace, Mauro A1 - Mechie, James A1 - Fishwick, Stewart A1 - Heine, Christian A1 - Scheck-Wenderoth, Magdalena A1 - Strecker, Manfred T1 - The Kenya rift revisited BT - insights into lithospheric strength through data-driven 3-D gravity and thermal modelling JF - Solid earth N2 - We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume-lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting. Y1 - 2017 U6 - https://doi.org/10.5194/se-8-45-2017 SN - 1869-9510 SN - 1869-9529 VL - 8 SP - 45 EP - 81 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Garcin, Yannick A1 - Schildgen, Taylor F. A1 - Acosta, Veronica Torres A1 - Melnick, Daniel A1 - Guillemoteau, Julien A1 - Willenbring, Jane A1 - Strecker, Manfred T1 - Short-lived increase in erosion during the African Humid Period BT - evidence from the northern Kenya Rift JF - Earth & planetary science letters N2 - The African Humid Period (AHP) between similar to 15 and 5.5 cal. kyr BP caused major environmental change in East Africa, including filling of the Suguta Valley in the northern Kenya Rift with an extensive (similar to 2150 km(2)), deep (similar to 300 m) lake. Interfingering fluvio-lacustrine deposits of the Baragoi paleo-delta provide insights into the lake-level history and how erosion rates changed during this time, as revealed by delta-volume estimates and the concentration of cosmogenic Be-10 in fluvial sand. Erosion rates derived from delta-volume estimates range from 0.019 to 0.03 mm yr(-1). Be-10-derived paleo-erosion rates at similar to 11.8 cal. kyr BP ranged from 0.035 to 0.086 mm yr(-1), and were 2.7 to 6.6 times faster than at present. In contrast, at similar to 8.7 cal. kyr BP, erosion rates were only 1.8 times faster than at present. Because Be-10-derived erosion rates integrate over several millennia; we modeled the erosion-rate history that best explains the 10Be data using established non-linear equations that describe in situ cosmogenic isotope production and decay. Two models with different temporal constraints (15-6.7 and 12-6.7 kyr) suggest erosion rates that were 25 to 300 times higher than the initial erosion rate (pre-delta formation). That pulse of high erosion rates was short (similar to 4 kyr or less) and must have been followed by a rapid decrease in rates while climate remained humid to reach the modern Be-10-based erosion rate of,similar to 0.013 mm yr(-1). Our simulations also flag the two highest Be-10-derived erosion rates at 11.8 kyr BP related to nonuniform catchment erosion. These changes in erosion rates and processes during the AHP may reflect a strong increase in precipitation, runoff, and erosivity at the arid-to-humid transition either at 15 or similar to 12 cal. kyr BP, before the landscape stabilized again, possibly due to increased soil production and denser vegetation. KW - northern Kenya Rift KW - Baragoi KW - paleo-delta KW - African Humid Period KW - erosion KW - Be-10 Y1 - 2017 U6 - https://doi.org/10.1016/j.epsl.2016.11.017 SN - 0012-821X SN - 1385-013X VL - 459 SP - 58 EP - 69 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Castino, Fabiana A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Rainfall variability and trends of the past six decades (1950-2014) in the subtropical NW Argentine Andes JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - The eastern flanks of the Central Andes are characterized by deep convection, exposing them to hydrometeorological extreme events, often resulting in floods and a variety of mass movements. We assessed the spatiotemporal pattern of rainfall trends and the changes in the magnitude and frequency of extreme events (ae95th percentile) along an E-W traverse across the southern Central Andes using rain-gauge and high-resolution gridded datasets (CPC-uni and TRMM 3B42 V7). We generated different climate indices and made three key observations: (1) an increase of the annual rainfall has occurred at the transition between low (< 0.5 km) and intermediate (0.5-3 km) elevations between 1950 and 2014. Also, rainfall increases during the wet season and, to a lesser degree, decreases during the dry season. Increasing trends in annual total amounts characterize the period 1979-2014 in the arid, high-elevation southern Andean Plateau, whereas trend reversals with decreasing annual total amounts were found at low elevations. (2) For all analyzed periods, we observed small or no changes in the median values of the rainfall-frequency distribution, but significant trends with intensification or attenuation in the 95th percentile. (3) In the southern Andean Plateau, extreme rainfall events exhibit trends towards increasing magnitude and, to a lesser degree, frequency during the wet season, at least since 1979. Our analysis revealed that low (< 0.5 km), intermediate (0.5-3 km), and high-elevation (> 3 km) areas respond differently to changing climate conditions, and the transition zone between low and intermediate elevations is characterized by the most significant changes. KW - Extreme rainfall KW - South American Monsoon System KW - Central Andes KW - Quantile regression KW - Rain gauges KW - CPC-uni KW - TRMM KW - Orographic barrier Y1 - 2017 U6 - https://doi.org/10.1007/s00382-016-3127-2 SN - 0930-7575 SN - 1432-0894 VL - 48 SP - 1049 EP - 1067 PB - Springer CY - New York ER - TY - JOUR A1 - Meessen, Christian A1 - Sippel, Judith A1 - Scheck-Wenderoth, Magdalena A1 - Heine, C. A1 - Strecker, Manfred T1 - Crustal structure of the andean foreland in Northern Argentina BT - results from data-integrative three-dimensional density modeling JF - Journal of geophysical research : Solid earth N2 - Previous thermomechanical modeling studies indicated that variations in the temperature and strength of the crystalline crust might be responsible for the juxtaposition of domains with thin-skinned and thick-skinned crustal deformation along strike the foreland of the central Andes. However, there is no evidence supporting this hypothesis from data-integrative models. We aim to derive the density structure of the lithosphere by means of integrated 3-D density modeling, in order to provide a new basis for discussions of compositional variations within the crust and for future thermal and rheological modeling studies. Therefore, we utilize available geological and geophysical data to obtain a structural and density model of the uppermost 200km of the Earth. The derived model is consistent with the observed Bouguer gravity field. Our results indicate that the crystalline crust in northern Argentina can be represented by a lighter upper crust (2,800kg/m(3)) and a denser lower crust (3,100kg/m(3)). We find new evidence for high bulk crustal densities >3,000kg/m(3) in the northern Pampia terrane. These could originate from subducted Puncoviscana wackes or pelites that ponded to the base of the crystalline crust in the late Proterozoic or indicate increasing bulk content of mafic material. The precise composition of the northern foreland crust, whether mafic or felsic, has significant implications for further thermomechanical models and the rheological behavior of the lithosphere. A detailed sensitivity analysis of the input parameters indicates that the model results are robust with respect to the given uncertainties of the input data. KW - central Andean foreland KW - gravity modeling KW - crustal density structure Y1 - 2018 U6 - https://doi.org/10.1002/2017JB014296 SN - 2169-9313 SN - 2169-9356 VL - 123 IS - 2 SP - 1875 EP - 1903 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Kübler, Simon A1 - Friedrich, Anke M. A1 - Gold, Ryan D. A1 - Strecker, Manfred T1 - Historical coseismic surface deformation of fluvial gravel deposits, Schafberg fault, Lower Rhine Graben, Germany JF - International journal of earth sciences N2 - Intraplate earthquakes pose a significant seismic hazard in densely populated rift systems like the Lower Rhine Graben in Central Europe. While the locations of most faults in this region are well known, constraints on their seismogenic potential and earthquake recurrence are limited. In particular, the Holocene deformation history of active faults remains enigmatic. In an exposure excavated across the Schafberg fault in the southwestern Lower Rhine Graben, south of Untermaubach, in the epicentral region of the 1756 Duren earthquake (M (L) 6.2), we mapped a complex deformation zone in Holocene fluvial sediments. We document evidence for at least one paleoearthquake that resulted in vertical surface displacement of 1.2 +/- 0.2 m. The most recent earthquake is constrained to have occurred after 815 AD, and we have modeled three possible earthquake scenarios constraining the timing of the latest event. Coseismic deformation is characterized by vertical offset of sedimentary contacts distributed over a 10-m-wide central damage zone. Faults were identified where they fracture and offset pebbles in the vertically displaced gravel layers and fracture orientation is consistent with the orientation of the Schafberg fault. This study provides the first constraint on the most recent surface-rupturing earthquake on the Schafberg fault. We cannot rule out that this fault acted as the source of the 1756 Duren earthquake. Our study emphasizes the importance of, and the need for, paleoseismic studies in this and other intracontinental regions, in particular on faults with subtle geomorphic expression that would not typically be recognized as being potentially seismically active. Our study documents textural features in unconsolidated sediment that formed in response to coseismic rupturing of the underlying bedrock fault. We suggest that these features, e.g., abundant oriented transgranular fractures in their context, should be added to the list of criteria used to identify a fault as potentially active. Such information would result in an increase of the number of potentially active faults that contribute to seismic hazards of intracontinental regions. KW - Paleoseismology KW - Intraplate earthquakes KW - Earthquake hazards KW - Coseismic rupture KW - Central Europe Y1 - 2018 U6 - https://doi.org/10.1007/s00531-017-1510-9 SN - 1437-3254 SN - 1437-3262 VL - 107 IS - 2 SP - 571 EP - 585 PB - Springer CY - New York ER - TY - JOUR A1 - Garcin, Yannick A1 - Deschamps, Pierre A1 - Menot, Guillemette A1 - de Saulieu, Geoffroy A1 - Schefuss, Enno A1 - Sebag, David A1 - Dupont, Lydie M. A1 - Oslisly, Richard A1 - Brademann, Brian A1 - Mbusnum, Kevin G. A1 - Onana, Jean-Michel A1 - Ako, Andrew A. A1 - Epp, Laura Saskia A1 - Tjallingii, Rik A1 - Strecker, Manfred A1 - Brauer, Achim A1 - Sachse, Dirk T1 - Early anthropogenic impact on Western Central African rainforests 2,600 y ago JF - Proceedings of the National Academy of Sciences of the United States of America N2 - A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. delta D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era. KW - Western Central Africa KW - late Holocene KW - rainforest crisis KW - paleohydrology KW - human activity Y1 - 2018 U6 - https://doi.org/10.1073/pnas.1715336115 SN - 0027-8424 VL - 115 IS - 13 SP - 3261 EP - 3266 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Ballato, Paolo A1 - Parra, Mauricio A1 - Schildgen, Taylor F. A1 - Dunkl, I. A1 - Yildirim, C. A1 - Özsayin, Erman A1 - Sobel, Edward A1 - Echtler, H. A1 - Strecker, Manfred T1 - Multiple exhumation phases in the Central Pontides (N Turkey) BT - new temporal constraints on Major geodynamic changes associated with the closure of the Neo-Tethys Ocean JF - Tectonics N2 - The Central Pontides of N Turkey represents a mobile orogenic belt of the southern Eurasian margin that experienced several phases of exhumation associated with the consumption of different branches of the Neo-Tethys Ocean and the amalgamation of continental domains. Our new low-temperature thermochronology data help to constrain the timing of these episodes, providing new insights into associated geodynamic processes. In particular, our data suggest that exhumation occurred at (1) similar to 110 to 90Ma, most likely during tectonic accretion and exhumation of metamorphic rocks from the subduction zone; (2) from similar to 60 to 40Ma, during the collision of the Kirehir and Anatolide-Tauride microcontinental domains with the Eurasian margin; (3) from similar to 0 to 25Ma, either during the early stages of the Arabia-Eurasia collision (soft collision) when the Arabian passive margin reached the trench, implying 70 to 530km of subduction of the Arabian passive margin, or during a phase of trench advance predating hard collision at similar to 20Ma; and (4) similar to 11Ma to the present, during transpression associated with the westward motion of Anatolia. Our findings document the punctuated nature of fault-related exhumation, with episodes of fast cooling followed by periods of slow cooling or subsidence, the role of inverted normal faults in controlling the Paleogene exhumation pattern, and of the North Anatolian Fault in dictating the most recent pattern of exhumation. KW - thermal modeling KW - Central Pontides KW - Arabia-Eurasia collision KW - trench advance KW - Anatolia westward motion KW - inversion tectonics Y1 - 2018 U6 - https://doi.org/10.1029/2017TC004808 SN - 0278-7407 SN - 1944-9194 VL - 37 IS - 6 SP - 1831 EP - 1857 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Eugster, Patricia A1 - Thiede, Rasmus Christoph A1 - Scherler, Dirk A1 - Stübner, Konstanze A1 - Sobel, Edward A1 - Strecker, Manfred T1 - Segmentation of the Main Himalayan Thrust Revealed by Low-Temperature Thermochronometry in the Western Indian Himalaya JF - Tectonics N2 - Despite remarkable tectonostratigraphic similarities along the Himalayan arc, pronounced topographic and exhumational variability exists in different morphotectonic segments. The processes responsible for this segmentation are debated. Of particular interest is a 30- to 40-km-wide orogen-parallel belt of rapid exhumation that extends from central Nepal to the western Himalaya and its possible linkage to a midcrustal ramp in the basal decollement, and the related growth of Lesser Himalayan duplex structures. Here we present 26 new apatite fission track cooling ages from the Beas-Lahul region, at the transition from the Central to the Western Himalaya (77 degrees-78 degrees E) to investigate segmentation in the Himalayan arc from a thermochronologic perspective. Together with previously published data from this part of the orogen, we document significant lateral changes in exhumation between the Dhauladar Range to the west, the Beas-Lahul region, and the Sutlej area to the east of the study area. In contrast to the Himalayan front farther east, exhumation in the far western sectors is focused at the frontal parts of the mountain range and associated with the hanging wall of the Main Boundary Thrust fault ramp. Our results allow us to spatially correlate the termination of the rapid exhumation belt with a midcrustal ramp to the west. We suggest that a plunging anticline at the northwestern edge of the Larji-Kullu-Rampur window represents the termination of the Central Himalayan segment, which is related to the evolution of the Lesser Himalayan duplex. Key Points KW - exhumation KW - Himalaya KW - duplex KW - fission track thermochronology KW - MHT Y1 - 2018 U6 - https://doi.org/10.1029/2017TC004752 SN - 0278-7407 SN - 1944-9194 VL - 37 IS - 8 SP - 2710 EP - 2726 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Tofelde, Stefanie A1 - Duesing, Walter A1 - Schildgen, Taylor F. A1 - Wickert, Andrew D. A1 - Wittmann, Hella A1 - Alonso, Ricardo N. A1 - Strecker, Manfred T1 - Effects of deep-seated versus shallow hillslope processes on cosmogenic Be-10 concentrations in fluvial sand and gravel JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - Terrestrial cosmogenic nuclide (TCN) concentrations in fluvial sediment, from which denudation rates are commonly inferred, can be affected by hillslope processes. TCN concentrations in gravel and sand may differ if localized, deep-excavation processes (e.g. landslides, debris flows) affect the contributing catchment, whereas the TCN concentrations of sand and gravel tend to be more similar when diffusional processes like soil creep and sheetwash are dominant. To date, however, no study has systematically compared TCN concentrations in different detrital grain-size fractions with a detailed inventory of hillslope processes from the entire catchment. Here we compare concentrations of the TCN Be-10 in 20 detrital sand samples from the Quebrada del Toro (southern Central Andes, Argentina) to a hillslope-process inventory from each contributing catchment. Our comparison reveals a shift from low-slope gullying and scree production in slowly denuding, low-slope areas to steep-slope gullying and landsliding in fast-denuding, steep areas. To investigate whether the nature of hillslope processes (locally excavating or more uniformly denuding) may be reflected in a comparison of the Be-10 concentrations of sand and gravel, we define the normalized sand-gravel index (NSGI) as the Be-10-concentration difference between sand and gravel divided by their summed concentrations. We find a positive, linear relationship between the NSGI and median slope, such that our NSGI values broadly reflect the shift in hillslope processes from low-slope gullying and scree production to steep-slope gullying and landsliding. Higher NSGI values characterize regions affected by steep-slope gullying or landsliding. We relate the large scatter in the relationship, which is exhibited particularly in low-slope areas, to reduced hillslope-channel connectivity and associated transient sediment storage within those catchments. While high NSGI values in well-connected catchments are a reliable signal of deep-excavation processes, hillslope excavation processes may not be reliably recorded by NSGI values where sediment experiences transient storage. (c) 2018 John Wiley & Sons, Ltd. Y1 - 2018 U6 - https://doi.org/10.1002/esp.4471 SN - 0197-9337 SN - 1096-9837 VL - 43 IS - 15 SP - 3086 EP - 3098 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Berndt, Christopher A1 - Yildirim, Cengiz A1 - Ciner, Attila A1 - Strecker, Manfred A1 - Ertunc, Gulgun A1 - Sarikaya, M. Akif A1 - Özcan, Orkan A1 - Ozturk, Tugba A1 - Kiyak, Nafiye Gunec T1 - Quaternary uplift of the northern margin of the Central Anatolian Plateau BT - New OSL dates of fluvial and delta-terrace deposits of the Kizilirmak River, Black Sea coast, Turkey JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - We analysed the interplay between coastal uplift, sea level change in the Black Sea, and incision of the Kizilirmak River in northern Turkey. These processes have created multiple co-genetic fluvial and marine terrace sequences that serve as excellent strain markers to assess the ongoing evolution of the Pontide orogenic wedge and the growth of the northern margin of the Central Anatolian Plateau. We used high-resolution topographic data, OSL ages, and published information on past sea levels to analyse the spatiotemporal evolution of these terraces; we derived a regional uplift model for the northward advancing orogenic wedge that supports the notion of laterally variable uplift rates along the flanks of the Pontides. The best-fit uplift model defines a constant long-term uplift rate of 0.28 +/- 0.07 m/ka for the last 545 ka. This model explains the evolution of the terrace sequence in light of active tectonic processes and superposed cycles of climate-controlled sea-level change. Our new data reveal regional uplift characteristics that are comparable to the inner sectors of the Central Pontides; accordingly, the rate of uplift diminishes with increasing distance from the main strand of the restraining bend of the North Anatolian Fault Zone (NAFZ). This spatial relationship between the regional impact of the restraining bend of the NAFZ and uplift of the Pontide wedge thus suggests a strong link between the activity of the NAFZ, deformation and uplift in the Pontide orogenic wedge, and the sustained lateral growth of the Central Anatolian Plateau flank. (C) 2018 Elsevier Ltd. All rights reserved. KW - Quaternary KW - OSL dating KW - Black Sea KW - Pontides KW - North Anatolian Fault Zone KW - Orogenic wedge KW - Kizilirmak River KW - MIS KW - Turkey Y1 - 2018 U6 - https://doi.org/10.1016/j.quascirev.2018.10.029 SN - 0277-3791 VL - 201 SP - 446 EP - 469 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ballato, Paolo A1 - Brune, Sascha A1 - Strecker, Manfred T1 - Sedimentary loading–unloading cycles and faulting in intermontane basins BT - Insights from numerical modeling and field observations in the NW Argentine Andes JF - Earth & planetary science letters N2 - The removal, redistribution, and transient storage of sediments in tectonically active mountain belts is thought to exert a first-order control on shallow crustal stresses, fault activity, and hence on the spatiotemporal pattern of regional deformation processes. Accordingly, sediment loading and unloading cycles in intermontane sedimentary basins may inhibit or promote intrabasinal faulting, respectively, but unambiguous evidence for this potential link has been elusive so far. Here we combine 2D numerical experiments that simulate contractional deformation in a broken-foreland setting (i.e., a foreland where shortening is diachronously absorbed by spatially disparate, reverse faults uplifting basement blocks) with field data from intermontane basins in the NW Argentine Andes. Our modeling results suggest that thicker sedimentary fills (>0.7-1.0 km) may suppress basinal faulting processes, while thinner fills (<0.7 km) tend to delay faulting. Conversely, the removal of sedimentary loads via fluvial incision and basin excavation promotes renewed intrabasinal faulting. These results help to better understand the tectono-sedimentary history of intermontane basins that straddle the eastern border of the Andean Plateau in northwestern Argentina. For example, the Santa Maria and the Humahuaca basins record intrabasinal deformation during or after sediment unloading, while the Quebrada del Toro Basin reflects the suppression of intrabasinal faulting due to loading by coarse conglomerates. We conclude that sedimentary loading and unloading cycles may exert a fundamental control on spatiotemporal deformation patterns in intermontane basins of tectonically active broken forelands. (C) 2018 Elsevier B.V. All rights reserved. KW - sedimentary loading and unloading cycles KW - intermontane basins KW - intrabasinal faulting KW - Argentinean broken foreland KW - 2D numerical experiments KW - Andes Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2018.10.043 SN - 0012-821X SN - 1385-013X VL - 506 SP - 388 EP - 396 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Georgieva, Viktoria A1 - Gallagher, Kerry A1 - Sobczyk, Artur A1 - Sobel, Edward A1 - Schildgen, Taylor F. A1 - Ehlers, Todd A1 - Strecker, Manfred T1 - Effects of slab-window, alkaline volcanism, and glaciation on thermochronometer cooling histories, Patagonian Andes JF - Earth & planetary science letters N2 - Southern Patagonia is a prime example of ongoing oceanic ridge collision and slab-window formation sustained over several million years. The impact of these phenomena on the thermal structure and exhumation of the crust have been mainly assessed with low-temperature thermochronology of bedrock samples. Here, we infer thermal histories from new and existing thermochronological data from the region of most recent ridge collision. In particular, we evaluate the potential far-reaching thermal effects of the evolving slab window, which have previously been considered responsible for patterns of late Miocene reheating associated with back-arc alkaline volcanism. Our model results define protracted cooling since similar to 15 Ma and stepwise exhumation since the late Miocene. The pattern of stepwise exhumation closely matches the onset of Patagonian glaciation at 7 Ma and the successive pulse of glacial incision coeval with neotectonic activity since 3-4 Ma that are also documented by independent geological and geomorphological evidence in the region. Importantly, our findings challenge the recently suggested lack of glacial erosion and incision since 5 Ma in this region. Furthermore, in contrast to previous modelling studies, we find that the available data do not evidence a previously proposed northward-propagating heating event associated with alkaline volcanism. We hypothesize that the anomalous alkaline volcanism in the Patagonian back-arc might be related to trench-orthogonal tears aligned with transform faults in the subducting plate. The substantial differences from the previous modelling procedure on some of the same samples is demonstrated to result from an important lack of convergence in model runs. (C) 2019 Elsevier B.V. All rights reserved. KW - inverse thermal modelling KW - thermochronology KW - apatite (U-Th)/He KW - apatite fission track KW - Patagonian Andes KW - slab window Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2019.01.030 SN - 0012-821X SN - 1385-013X VL - 511 SP - 164 EP - 176 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pingel, Heiko A1 - Schildgen, Taylor F. A1 - Strecker, Manfred A1 - Wittmann, Hella T1 - Pliocene-Pleistocene orographic control on denudation in northwest Argentina JF - Geology N2 - The intermontane Humahuaca Basin in the Eastern Cordillera of the northwest Argentine Andes lies leeward of an orographic barrier to easterly derived moisture. An average of >2000 mm/yr of rainfall along the eastern flanks of the barrier contrasts with <200 mm/yr in the orogen interior. Paleoenvironmental reconstructions suggest that the basin became disconnected from the foreland during the Miocene-Pliocene by the growth of fault-bounded mountain ranges. Fossil records, sedimentology, and stable isotope data imply that rerouting of the fluvial network by 4.2 Ma and reduced rainfall by ca. 3 Ma were consequences of that range uplift. Here, we present cosmogenic nuclide-derived (Be-10) paleodenudation rates from 6 to 2 Ma fluvial deposits collected from the Humahuaca Basin. Despite increased tectonic activity, our Be-10 data show a tenfold decrease in denudation rates at ca. 3 Ma, documenting a link between uplift-induced semiarid conditions and decreasing hillslope denudation rates. This new data set thus demonstrates the influence of hydrological change on spatiotemporal denudation patterns in tectonically active mountain areas. Y1 - 2019 U6 - https://doi.org/10.1130/G45800.1 SN - 0091-7613 SN - 1943-2682 VL - 47 IS - 4 SP - 359 EP - 362 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Melnick, Daniel A1 - Hillemann, Christian A1 - Jara Muñoz, Julius A1 - Garrett, Ed A1 - Cortes-Aranda, Joaquin A1 - Molina, Diego A1 - Tassara, Andrés A1 - Strecker, Manfred T1 - Hidden Holocene Slip Along the Coastal El Yolki Fault in Central Chile and Its Possible Link With Megathrust Earthquakes JF - Journal of geophysical research : Solid earth N2 - Megathrust earthquakes are commonly accompanied by increased upper-plate seismicity and occasionally triggered fault slip. In Chile, crustal faults slipped during and after the 2010 Maule (M8.8) earthquake. We studied the El Yolki fault (EYOF), a transtensional structure midways the Maule rupture not triggered in 2010. We mapped a Holocene coastal plain using light detection and ranging, which did not reveal surface ruptures. However, the inner-edge and shoreline angles along the coastal plain as well as 4.3- to 4.0-ka intertidal sediments are back-tilted on the EYOF footwall block, documenting 10 m of vertical displacement. These deformed markers imply similar to 2-mm/year throw rate, and dislocation models a slip rate of 5.6 mm/year for the EYOF. In a 5-m-deep trench, the Holocene intertidal sediments onlap to five erosive steps, interpreted as staircase wave-cut landforms formed by discrete events of relative sea level drop. We tentatively associated these steps with coseismic uplift during EYOF earthquakes between 4.3 and 4.0 ka. The Maule earthquake rupture may be subdivided into three subsegments based on coseismic slip and gravity anomalies. Coulomb stress transfer models predict neutral stress changes at the EYOF during the Maule earthquake but positive changes for a synthetic slip distribution at the central subsegment. If EYOF earthquakes were triggered by megathrust events, their slip distribution was probably focused in the central subsegment. Our study highlights the millennial variability of crustal faulting and the megathrust earthquake cycle in Chile, with global implications for assessing the hazards posed by hidden but potentially seismogenic coastal faults along subduction zones. KW - Central Chile KW - megathrust earthquake KW - crustal fault KW - seismotectonic segmentation KW - Middle Holocene KW - sea level change Y1 - 2019 U6 - https://doi.org/10.1029/2018JB017188 SN - 2169-9313 SN - 2169-9356 VL - 124 IS - 7 SP - 7280 EP - 7302 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Pingel, Heiko A1 - Alonso, Ricardo N. A1 - Altenberger, Uwe A1 - Cottle, John A1 - Strecker, Manfred T1 - Miocene to Quaternary basin evolution at the southeastern Andean Plateau (Puna) margin (ca. 24°S lat, Northwestern Argentina) JF - Basin research N2 - The Andean Plateau of NW Argentina is a prominent example of a high-elevation orogenic plateau characterized by internal drainage, arid to hyper-arid climatic conditions and a compressional basin-and-range morphology comprising thick sedimentary basins. However, the development of the plateau as a geomorphic entity is not well understood. Enhanced orographic rainout along the eastern, windward plateau flank causes reduced fluvial run-off and thus subdued surface-process rates in the arid hinterland. Despite this, many Puna basins document a complex history of fluvial processes that have transformed the landscape from aggrading basins with coalescing alluvial fans to the formation of multiple fluvial terraces that are now abandoned. Here, we present data from the San Antonio de los Cobres (SAC) area, a sub-catchment of the Salinas Grandes Basin located on the eastern Puna Plateau bordering the externally drained Eastern Cordillera. Our data include: (a) new radiometric U-Pb zircon data from intercalated volcanic ash layers and detrital zircons from sedimentary key horizons; (b) sedimentary and geochemical provenance indicators; (c) river profile analysis; and (d) palaeo-landscape reconstruction to assess aggradation, incision and basin connectivity. Our results suggest that the eastern Puna margin evolved from a structurally controlled intermontane basin during the Middle Miocene, similar to intermontane basins in the Mio-Pliocene Eastern Cordillera and the broken Andean foreland. Our refined basin stratigraphy implies that sedimentation continued during the Late Mio-Pliocene and the Quaternary, after which the SAC area was subjected to basin incision and excavation of the sedimentary fill. Because this incision is unrelated to baselevel changes and tectonic processes, and is similar in timing to the onset of basin fill and excavation cycles of intermontane basins in the adjacent Eastern Cordillera, we suspect a regional climatic driver, triggered by the Mid-Pleistocene Climate Transition, caused the present-day morphology. Our observations suggest that lateral orogenic growth, aridification of orogenic interiors, and protracted plateau sedimentation are all part of a complex process chain necessary to establish and maintain geomorphic characteristics of orogenic plateaus in tectonically active mountain belts. KW - Andean Plateau KW - NW Argentina KW - Puna KW - river incision KW - sediment routing KW - surface processes Y1 - 2019 U6 - https://doi.org/10.1111/bre.12346 SN - 0950-091X SN - 1365-2117 VL - 31 IS - 4 SP - 808 EP - 826 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Ibarra, Federico A1 - Liu, Sibiao A1 - Meeßen, Christian A1 - Prezzi, Claudia Beatriz A1 - Bott, Judith A1 - Scheck-Wenderoth, Magdalena A1 - Sobolev, Stephan Vladimir A1 - Strecker, Manfred T1 - 3D data-derived lithospheric structure of the Central Andes and its implications for deformation: Insights from gravity and geodynamic modelling JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - We present a new three-dimensional density model of the Central Andes characterizing the structure and composition of the lithosphere together with a geodynamic simulation subjected to continental intraplate shortening. The principal aim of this study is to assess the link between heterogeneities in the lithosphere and different deformation patterns and styles along the orogen-foreland system of the Central Andes. First, we performed a 3D integration of new geological and geophysical data with previous models through forward modelling of Bouguer anomalies. Subsequently, a geodynamic model was set-up and parametrized from the previously obtained 3D structure and composition. We do not find a unambigous correlation between the resulting density configuration and terrane boundaries proposed by other authors. Our models reproduce the observed Bouguer anomaly and deformation patterns in the foreland. We find that thin-skinned deformation in the Subandean fold-and thrust belt is controlled by a thick sedimentary layer and coeval underthrusting of thin crust of the foreland beneath the thick crust of the Andean Plateau. In the adjacent thick-skinned deformation province of the inverted Cretaceous extensional Santa Barbara System sedimentary strata are much thinner and crustal thickness transitions from greater values in the Andean to a more reduced thickness in the foreland. Our results show that deformation processes occur where the highest gradients of lithospheric strength are present between the orogen and the foreland, thus suggesting a spatial correlation between deformation and lithospheric strength. KW - Central Andes KW - Lithospheric structure KW - Gravity modelling KW - Geodynamic modelling KW - Deformation Y1 - 2019 U6 - https://doi.org/10.1016/j.tecto.2019.06.025 SN - 0040-1951 SN - 1879-3266 VL - 766 SP - 453 EP - 468 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Teshebaeva, Kanayim A1 - Echtler, Helmut A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Deep-seated gravitational slope deformation (DSGSD) and slow-moving landslides in the southern Tien Shan Mountains: new insights from InSAR, tectonic and geomorphic analysis JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - We investigated deep-seated gravitational slope deformation (DSGSD) and slow mass movements in the southern Tien Shan Mountains front using synthetic aperture radar (SAR) time-series data obtained by the ALOS/PALSAR satellite. DSGSD evolves with a variety of geomorphological changes (e.g. valley erosion, incision of slope drainage networks) over time that affect earth surfaces and, therefore, often remain unexplored. We analysed 118 interferograms generated from 20 SAR images that covered about 900 km(2). To understand the spatial pattern of the slope movements and to identify triggering parameters, we correlated surface dynamics with the tectono-geomorphic processes and lithologic conditions of the active front of the Alai Range. We observed spatially continuous, constant hillslope movements with a downslope speed of approximately 71 mm year(-1) velocity. Our findings suggest that the lithological and structural framework defined by protracted deformation was the main controlling factor for sustained relief and, consequently, downslope mass movements. The analysed structures revealed integration of a geological/structural setting with the superposition of Cretaceous-Paleogene alternating carbonatic and clastic sedimentary structures as the substratum for younger, less consolidated sediments. This type of structural setting causes the development of large-scale, gravity-driven DSGSD and slow mass movement. Surface deformations with clear scarps and multiple crest lines triggered planes for large-scale deep mass creeps, and these were related directly to active faults and folds in the geologic structures. Our study offers a new combination of InSAR techniques and structural field observations, along with morphometric and seismologic correlations, to identify and quantify slope instability phenomena along a tectonically active mountain front. These results contribute to an improved natural risk assessment in these structures. KW - interferometric SAR (InSAR) KW - small baseline subset (SBAS) KW - gravity-driven slope deformation KW - landslide KW - tectonic geomorphology KW - Tien Shan Mountains Y1 - 2019 U6 - https://doi.org/10.1002/esp.4648 SN - 0197-9337 SN - 1096-9837 VL - 44 IS - 12 SP - 2333 EP - 2348 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Pedoja, Kevin A1 - Strecker, Manfred T1 - TerraceM-2: A MatlabR (R) Interface for Mapping and Modeling Marine and Lacustrine Terraces JF - Frontiers in Earth Science N2 - The morphology of marine and lacustrine terraces has been largely used to measure past sea- and lake-level positions and estimate vertical deformation in a wealth of studies focused on climate and tectonic processes. To obtain accurate morphometric assessments of terrace morphology we present TerraceM-2, an improved version of our MatlabR (R) graphic-user interface that provides new methodologies for morphometric analyses as well as landscape evolution and fault-dislocation modeling. The new version includes novel routines to map the elevation and spatial distribution of terraces, to model their formation and evolution, and to estimate fault-slip rates from terrace deformation patterns. TerraceM-2 has significantly improves its processing speed and mapping capabilities, and includes separate functions for developing customized workflows beyond the graphic-user interface. We illustrate these new mapping and modeling capabilities with three examples: mapping lacustrine shorelines in the Dead Sea to estimate deformation across the Dead Sea Fault, landscape evolution modeling to estimate a history of uplift rates in southern Peru, and dislocation modeling of deformed marine terraces in California. These examples also illustrate the need to use topographic data of different resolutions. The new modeling and mapping routines of TerraceM-2 highlight the advantages of an integrated joint mapping and modeling approach to improve the efficiency and precision of coastal terrace metrics in both marine and lacustrine environments. KW - TerraceM KW - marine terraces KW - tectonic geomorphology KW - geomorphic markers KW - LiDAR KW - coastal geomorphology KW - neotectonics KW - morphometry Y1 - 2019 U6 - https://doi.org/10.3389/feart.2019.00255 SN - 2296-6463 VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Arnous, Ahmad A1 - Zeckra, Martin A1 - Venerdini, Agostina A1 - Alvarado, Patricia A1 - Arrowsmith, Ramón A1 - Guillemoteau, Julien A1 - Landgraf, Angela A1 - Gutiérrez, Adolfo Antonio A1 - Strecker, Manfred T1 - Neotectonic Activity in the Low-Strain Broken Foreland (Santa Bárbara System) of the North-Western Argentinean Andes (26°S) JF - Lithosphere N2 - Uplift in the broken Andean foreland of the Argentine Santa Bárbara System (SBS) is associated with the contractional reactivation of basement anisotropies, similar to those reported from the thick-skinned Cretaceous-Eocene Laramide province of North America. Fault scarps, deformed Quaternary deposits and landforms, disrupted drainage patterns, and medium-sized earthquakes within the SBS suggest that movement along these structures may be a recurring phenomenon, with yet to be defined repeat intervals and rupture lengths. In contrast to the Subandes thrust belt farther north, where eastward-migrating deformation has generated a well-defined thrust front, the SBS records spatiotemporally disparate deformation along structures that are only known to the first order. We present herein the results of geomorphic desktop analyses, structural field observations, and 2D electrical resistivity tomography and seismic-refraction tomography surveys and an interpretation of seismic reflection profiles across suspected fault scarps in the sedimentary basins adjacent to the Candelaria Range (CR) basement uplift, in the south-central part of the SBS. Our analysis in the CR piedmont areas reveals consistency between the results of near-surface electrical resistivity and seismic-refraction tomography surveys, the locations of prominent fault scarps, and structural geometries at greater depth imaged by seismic reflection data. We suggest that this deformation is driven by deep-seated blind thrusting beneath the CR and associated regional warping, while shortening involving Mesozoic and Cenozoic sedimentary strata in the adjacent basins was accommodated by layer-parallel folding and flexural-slip faults that cut through Quaternary landforms and deposits at the surface. Y1 - 2019 U6 - https://doi.org/10.2113/2020/8888588 SN - 1947-4253 SN - 1941-8264 VL - 2020 IS - 1 SP - 1 EP - 25 PB - GSA CY - Boulder, Colo. ER - TY - JOUR A1 - Garcia, Victor H. A1 - Hongn, Fernando D. A1 - Yagupsky, Daniel A1 - Pingel, Heiko A1 - Kinnaird, Timothy A1 - Winocur, Diego A1 - Cristallini, Ernesto A1 - Robinson, Ruth Aj A1 - Strecker, Manfred T1 - Late Quaternary tectonics controlled by fault reactivation. Insights from a local transpressional system in the intermontane Lerma valley, Cordillera Oriental, NW Argentina JF - Journal of structural geology N2 - We analyzed the Lomas de Carabajal area in the intermontane Lerma valley of the Cordillera Oriental to assess the level of neotectonic activity in a densely populated region of northwestern Argentina. In this region, Plio-Pleistocene synorogenic conglomerates are deformed, locally associated with high-angle faults, and NNW-SSE oriented en-echelon folds characterized by wavelengths of < 1 km. The deformed Quaternary units follow the same pattern of deformation as observed in the underlying Neogene deposits; growth-strata geometries are observed near faults. This configuration is compatible with local left-lateral transpressional tectonism driven by ENE-WSW buttressing against the NW-oriented border of a Cretaceous extensional basin (Alemania sub-basin). Optically Stimulated Luminescence analysis of sandy-silty layers interbedded within the folded late Pleistocene conglomeratic sequence helps to determine uplift rates of 0.83-0.87 mm/a during the last 30-40 ka. Nearby the Lomas de Carabajal, a WNW-striking, 3-m-high fault scarp disrupts radiocarbon dated, 10-ka-old loessic deposits providing a Holocene mean uplift rate of 0.30 mm/a. Our data unambiguously show that shallow crustal deformation in the intermontane Lerma valley is ongoing; some of this deformation may be associated with seismicity. Our findings support the notion of temporally and spatially disparate deformation processes in the broken foreland of the northwestern Argentinean Andes. KW - Structural geology KW - Neotectonics KW - OSL and C-14 geochronology KW - Syntectonic sedimentation KW - Seismogenic sources Y1 - 2019 U6 - https://doi.org/10.1016/j.jsg.2019.103875 SN - 0191-8141 VL - 128 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Hetzel, Ralf A1 - Niedermann, Samuel A1 - Tao, Mingxin A1 - Kubik, Peter W. A1 - Strecker, Manfred T1 - Climatic versus tectonic control on river incision at the margin of NE Tibet: Be-10 exposure dating of river terraces at the mountain front of the Qilian Shan JF - Journal of geophysical research : Earth surface N2 - [1] We document late Pleistocene - Holocene aggradation and incision processes at the mountain front of the Qilian Shan, an active intracontinental fold-and-thrust belt accommodating a significant portion of the India-Asia convergence. The Shiyou River cuts through a NNE vergent fault propagation fold with Miocene red beds in the core and Pliocene - Quaternary growth strata on the northern forelimb. South of the anticline, Miocene strata dip 20 degrees SSW, suggesting a similar orientation for the basal decollement. After aggradation of an similar to 150-m-thick, late Pleistocene valley fill, the Shiyou River formed three terraces. The highest terrace, located 170 m above the river, constitutes the top of the fill. The other terraces are fill cut terraces: their treads are located 130 - 105 m and 37 m above the river, respectively. The 10 Be exposure dating of the terraces suggests that river incision accelerated from 0.8 +/- 0.2 mm yr(-1) to similar to 10 mm yr(-1) at 10 - 15 kyr. We interpret fast Holocene river incision as largely unrelated to tectonic forcing. The late Pleistocene incision rate of 0.8 +/- 0.2 mm yr(-1) places an upper limit of 2.2 +/- 0.5 mm yr(-1) on the horizontal shortening rate, assuming that incision is solely caused by rock uplift above a decollement dipping 20 degrees. However, the actual shortening rate may lie between similar to 2.2 mm yr(-1) and zero because deformation of the terraces and the valley fill cannot be unequivocally demonstrated. Our estimate is consistent with the bulk shortening rate of similar to 5 - 10 mm yr(-1) across several faults in NE Tibet derived from neotectonic and GPS data, although in case of the Shiyou River, Holocene deformation is barely discernible owing to intense climate-induced river incision. Y1 - 2006 U6 - https://doi.org/10.1029/2005JF000352 SN - 2169-9003 SN - 2169-9011 VL - 111 PB - Union CY - Washington ER - TY - JOUR A1 - Deeken, Anke A1 - Sobel, Edward A1 - Coutand, Isabelle A1 - Haschke, Michael A1 - Riller, Ulrich A1 - Strecker, Manfred T1 - Development of the southern Eastern Cordillera, NW Argentina, constrained by apatite fission track thermochronology: From early Cretaceous extension to middle Miocene shortening JF - Tectonics N2 - [ 1] For the Puna Plateau and Eastern Cordillera of NW Argentina, the temporal and spatial pattern of deformation and surface uplift remain poorly constrained. Analysis of completely and partially reset apatite fission track samples collected from vertical profiles along an ESE trending transect extending from the plateau interior across the southern Eastern Cordillera at similar to 25 degrees S reveals important constraints on the deformation and exhumation history of this part of the Andes. The data constrain the Neogene Andean development of the Eastern Cordillera as well as rift-related exhumation for some of the sampled locations in the Late Jurassic/Early Cretaceous. An intervening Eocene-Oligocene exhumation episode in the southern Eastern Cordillera was probably related to crustal shortening. Subsequent reburial of the area by Andean foreland basin strata commenced between 30 and 25 Myr. Magnitude and duration of sedimentation, revealed by thermal modeling, differ between the sample locations, pointing to an eastward propagating basin system. In the southern Eastern Cordillera, Andean deformation commenced at 22.5 - 21 Myr, predating both the inferred formation of significant topography by 5 - 7.5 Myr and preservation of sediments in the adjacent Cenozoic basins by 6.5 - 8 Myr. Comparing the calculated structural depth of partially reset samples suggests that newly formed west dipping reverse faults along the former Salta Rift margin accommodated most of the Neogene tectonic movement. Late Cenozoic deformation at the southern Eastern Cordillera began earlier in the west and subsequently propagated eastward. The lateral growth of the orogen is coupled with a foreland basin system developing in front of the range and then becomes subsequently compartmentalized by later emergent topography. Y1 - 2006 U6 - https://doi.org/10.1029/2005TC001894 SN - 0278-7407 VL - 25 IS - 6 PB - Union CY - Washington ER - TY - JOUR A1 - Guzman, Silvina A1 - Strecker, Manfred A1 - Marti, Joan A1 - Petrinovic, Ivan A. A1 - Schildgen, Taylor F. A1 - Grosse, Pablo A1 - Montero-Lopez, Carolina A1 - Neri, Marco A1 - Carniel, Roberto A1 - D. Hongn, Fernando A1 - Muruaga, Claudia A1 - Sudo, Masafumi T1 - Construction and degradation of a broad volcanic massif: The Vicuna Pampa volcanic complex, southern Central Andes, NW Argentina JF - Geological Society of America bulletin N2 - The Vicuna Pampa volcanic complex, at the SE edge of the arid Puna Plateau of the Central Andes, records the interplay between volcanic construction and degra-dational processes. The low-sloping Vicuna Pampa volcanic complex, with a 1200-m-deep, southeastward-opening depression, was previously interpreted as a collapse caldera based on morphological considerations. However, characteristic features associated with collapse calderas do not exist, and close inspection instead suggests that the Vicuna Pampa volcanic complex is a strongly eroded, broad, massif-type composite volcano of mainly basaltic to trachyandesitic composition. Construction of the Vicuna Pampa volcanic complex occurred during two distinct cycles separated by the development of the depression. The first and main cycle took place at ca. 12 Ma and was dominated by lava flows and subordinate scoria cones and domes. The second cycle, possibly late Miocene in age, affected the SW portion of the depression with the emplacement of domes. We interpret the central depression as the result of a possible sector collapse and subsequent intense fluvial erosion during middle to late Miocene time, facilitated by faulting, steepened topography, and wetter climate conditions compared to today. We estimate that similar to 65% of the initial edifice of similar to 240 km(3) was degraded. The efficiency of degradation processes for removing mass from the Vicuna Pampa volcanic complex is surprising, considering that today the region is arid, and the stream channels within the complex are predominantly transport limited, forming a series of coalesced, aggraded alluvial fans and eolian infill. Hence, the Vicuna Pampa volcanic complex records the effects of past degradation efficiency that differs substantially from that of today. Y1 - 2017 U6 - https://doi.org/10.1130/B31631.1 SN - 0016-7606 SN - 1943-2674 VL - 129 SP - 750 EP - 766 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Zambrano, Patricio A1 - Rietbrock, Andreas A1 - Gonzalez, Javiera A1 - Argandona, Boris A1 - Strecker, Manfred T1 - Quantifying offshore fore-arc deformation and splay-fault slip using drowned Pleistocene shorelines, Arauco Bay, Chile JF - Journal of geophysical research : Solid earth N2 - Most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial timescales. Here we study millennial deformation associated with an active splay-fault system in the Arauco Bay area off south central Chile. We describe hitherto unrecognized drowned shorelines using high-resolution multibeam bathymetry, geomorphic, sedimentologic, and paleontologic observations and quantify uplift rates using a Landscape Evolution Model. Along a margin-normal profile, uplift rates are 1.3m/ka near the edge of the continental shelf, 1.5m/ka at the emerged Santa Maria Island, -0.1m/ka at the center of the Arauco Bay, and 0.3m/ka in the mainland. The bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal-scale Santa Maria splay-fault system. We modeled surface deformation using two different structural scenarios: deep-reaching normal faults and deep-reaching reverse faults with shallow extensional structures. Our preferred model comprises a blind reverse fault extending from 3km depth down to the plate interface at 16km that slips at a rate between 3.0 and 3.7m/ka. If all the splay-fault slip occurs during every great megathrust earthquake, with a recurrence of similar to 150-200years, the fault would slip similar to 0.5m per event, equivalent to a magnitude similar to 6.4 earthquake. However, if the splay-fault slips only with a megathrust earthquake every similar to 1000years, the fault would slip similar to 3.7m per event, equivalent to a magnitude similar to 7.5 earthquake. KW - splay fault KW - marine terraces KW - Arauco Bay KW - TerraceM KW - fore arc KW - earthquake Y1 - 2017 U6 - https://doi.org/10.1002/2016JB013339 SN - 2169-9313 SN - 2169-9356 VL - 122 SP - 4529 EP - 4558 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Melnick, Daniel A1 - Yildirim, Cengiz A1 - Hillemann, Christian A1 - Garcin, Yannick A1 - Ciner, T. Attila A1 - Perez-Gussinye, Marta A1 - Strecker, Manfred T1 - Slip along the Sultanhani Fault in Central Anatolia from deformed Pleistocene shorelines of palaeo-lake Konya and implications for seismic hazards in low-strain regions JF - Geophysical journal international N2 - Central Anatolia is a low-relief, high-elevation region where decadal-scale deformation rates estimated from space geodesy suggest low strain rates within a stiff microplate. However, numerous Quaternary faults have been mapped within this low-strain region and estimating their slip rate and seismic potential is important for hazard assessments in an area of increasing infrastructural development. Here we focus on the Sultanhani Fault (SF), which constitutes an integral part of the Eskisehir-Cihanbeyli Fault System, and use deformed maximum highstand shorelines of palaeo-lake Konya to estimate tectonic slip rates at millennial scale. Some of these shorelines were previously interpreted as fault scarps, but we provide conclusive evidence for their erosional origin. We found that shoreline-angle elevations estimated from differential GPS profiles record vertical displacements of 10.2 m across the SF. New radiocarbon ages of lacustrine molluscs suggest 22.4 m of relative lake-level fall between 22.1 +/- 0.3 and 21.7 +/- 0.4 cal. kaBP, constraining the timing of abrupt abandonment of the highstand shoreline. Models of lithospheric rebound associated with regressions of the Tuz Golu and Konya palaeolakes predict only similar to 1 m of regional-scale uplift across the Konya Basin. Dislocation models of displaced shorelines suggest fault-slip rates of 1.5 and 1.8 mm yr(-1) for planar and listric fault geometries, respectively, providing reasonable results for the latter. We found fault scarps in the Nasuhpinar mudflat that likely represent the most recent ground-breaking rupture of the SF, with an average vertical displacement of 1.2 +/- 0.5 m estimated from 54 topographic profiles, equivalent to a M similar to 6.5-6.9 earthquake based on empirical scaling laws. If such events were characteristic during the ultimate 21 ka, a relatively short recurrence time of similar to 800-900 yr would be needed to account for the millennial slip rate. Alternatively, the fault scarp at Nasuhpinar might represent a larger earthquake requiring more frequent smaller events to account for the millennial rate. The relatively fast slip rate of the SF over the past 21 ka is unlikely to have persisted over longer timescales and might reflect spatiotemporal variations in deformation rates within kinematically-linked fault systems within Central Anatolia, or a transient perturbation to the local stress field or fault strength. Such perturbation might have been related to climatically controlled changes in surface and near-surface loads and by interactions among the different tectonic processes that have been proposed to drive the overall slow uplift and associated extension in the Central Anatolian Plateau. KW - Seismic cycle KW - Geomorphology KW - Continental neotectonics KW - Earthquake hazards KW - Tectonics and climatic interactions Y1 - 2017 U6 - https://doi.org/10.1093/gji/ggx074 SN - 0956-540X SN - 1365-246X VL - 209 SP - 1431 EP - 1454 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Heidarzadeh, Ghasem A1 - Ballato, Paolo A1 - Hassanzadeh, Jamshid A1 - Ghassemi, Mohammad R. A1 - Strecker, Manfred T1 - Lake overspill and onset of fluvial incision in the Iranian Plateau: Insights from the Mianeh Basin JF - Earth & planetary science letters N2 - Orogenic plateaus represent a prime example of the interplay between surface processes, climate, and tectonics. This kind of an interplay is thought to be responsible for the formation, preservation, and, ultimately, the destruction of a typical elevated, low-internal relief plateau landscape. Here, we document the timing of intermontane basin filling associated with the formation of a low-relief plateau morphology, followed by basin opening and plateau-flank incision in the northwestern Iranian Plateau of the Arabia Eurasia collision zone. Our new U-Pb zircon ages from intercalated volcanic ashes in exposed plateau basin-fill sediments from the most external plateau basin (Mianeh Basin) document that the basin was internally drained at least between similar to 7 and 4 Ma, and that from similar to 5 to 4 Ma it was characterized by an similar to 2-km-high and similar to 0.5-km-deep lake (Mianeh paleolake), most likely as a result of wetter climatic conditions. At the same time, the eastern margin of the Mianeh Basin (and, therefore, of the Iranian Plateau) experienced limited tectonic activity, as documented by onlapping sediments and smoothed topography. The combination of high lake level and subdued topography at the plateau margin led to lake overspill, which resulted in the cutting of an similar to 1-km-deep bedrock gorge (Amardos) by the Qezel-Owzan River (QOR) beginning at similar to 4 Ma. This was associated with the incision of the plateau landscape and the establishment of fluvial connectivity with the Caspian Sea. Overall, our study emphasizes the interplay between surface and tectonic processes in forming, maintaining, and destroying orogenic plateau morphology, the transitional nature of orogenic plateau landscapes on timescales of 10(6) yr, and, finally, the role played by overspilling in integrating endorheic basins. (C) 2017 Elsevier B.V. All rights reserved. KW - Iranian Plateau KW - basin evolution KW - overspill KW - incision KW - geomorphic analysis KW - climate Y1 - 2017 U6 - https://doi.org/10.1016/j.epsl.2017.04.019 SN - 0012-821X SN - 1385-013X VL - 469 SP - 135 EP - 147 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Cifelli, Francesca A1 - Heidarzadeh, Ghasem A1 - Ghassemi, Mohammad R. A1 - Wickert, Andrew D. A1 - Hassanzadeh, Jamshid A1 - Dupont-Nivet, Guillaume A1 - Balling, Philipp A1 - Sudo, Masafumi A1 - Zeilinger, Gerold A1 - Schmitt, Axel K. A1 - Mattei, Massimo A1 - Strecker, Manfred T1 - Tectono-sedimentary evolution of the northern Iranian Plateau: insights from middle-late Miocene foreland-basin deposits JF - Basin research N2 - Sedimentary basins in the interior of orogenic plateaus can provide unique insights into the early history of plateau evolution and related geodynamic processes. The northern sectors of the Iranian Plateau of the Arabia-Eurasia collision zone offer the unique possibility to study middle-late Miocene terrestrial clastic and volcaniclastic sediments that allow assessing the nascent stages of collisional plateau formation. In particular, these sedimentary archives allow investigating several debated and poorly understood issues associated with the long-term evolution of the Iranian Plateau, including the regional spatio-temporal characteristics of sedimentation and deformation and the mechanisms of plateau growth. We document that middle-late Miocene crustal shortening and thickening processes led to the growth of a basement-cored range (Takab Range Complex) in the interior of the plateau. This triggered the development of a foreland-basin (Great Pari Basin) to the east between 16.5 and 10.7Ma. By 10.7Ma, a fast progradation of conglomerates over the foreland strata occurred, most likely during a decrease in flexural subsidence triggered by rock uplift along an intraforeland basement-cored range (Mahneshan Range Complex). This was in turn followed by the final incorporation of the foreland deposits into the orogenic system and ensuing compartmentalization of the formerly contiguous foreland into several intermontane basins. Overall, our data suggest that shortening and thickening processes led to the outward and vertical growth of the northern sectors of the Iranian Plateau starting from the middle Miocene. This implies that mantle-flow processes may have had a limited contribution toward building the Iranian Plateau in NW Iran. Y1 - 2017 U6 - https://doi.org/10.1111/bre.12180 SN - 0950-091X SN - 1365-2117 VL - 29 SP - 417 EP - 446 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Bernhardt, Anne A1 - Schwanghart, Wolfgang A1 - Hebbeln, Dierk A1 - Stuut, Jan-Berend W. A1 - Strecker, Manfred T1 - Immediate propagation of deglacial environmental change to deep-marine turbidite systems along the Chile convergent margin JF - Earth & planetary science letters N2 - Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment "uxes. Sedimentary records provide the archives for inferring these processes, but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments. These sites allowed us to study event related depositional processes in different climatic and geomorphic settings from the Last Glacial Maximum to the present day. The three sites reveal a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise postdate the decline in turbidite deposition. Comparison with paleoclimate proxies documents that the spatio-temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times. Our results let us infer that declining deglacial humidity decreased "uvial sediment supply. This signal propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chile, connectivity between the Andean erosional zone and the "uvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation, resulting in a sudden decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss. (C) 2017 Elsevier B.V. All rights reserved. KW - signal propagation KW - turbidity currents KW - Chile KW - sediment-routing system connectivity KW - Last Glacial Maximum Y1 - 2017 U6 - https://doi.org/10.1016/j.epsl.2017.05.017 SN - 0012-821X SN - 1385-013X VL - 473 SP - 190 EP - 204 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Tofelde, Stefanie A1 - Schildgen, Taylor F. A1 - Savi, Sara A1 - Pingel, Heiko A1 - Wickert, Andrew D. A1 - Bookhagen, Bodo A1 - Wittmann, Hella A1 - Alonso, Ricardo N. A1 - Cottle, John A1 - Strecker, Manfred T1 - 100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina JF - Earth & planetary science letters N2 - Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic Be-10 depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 +/- 7 and 487 +/- 34 ka. Depositional ages of the conglomerates, determined by four Al-26/Be-10 burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 +/- 141 to 936 +/- 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at similar to 1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two nearby basins that record precessional (21-kyr) and long-eccentricity (400-kyr) forcing within sedimentary and geomorphic archives, the recorded cyclicity scales with the square of the drainage basin length. (C) 2017 Elsevier B.V. All rights reserved. KW - Be-10 depth-profiles KW - surface inflation KW - aggradation-incision cycles KW - glacial-interglacial cycles KW - landscape response to climate change KW - Eastern Cordillera Y1 - 2017 U6 - https://doi.org/10.1016/j.epsl.2017.06.001 SN - 0012-821X SN - 1385-013X VL - 473 SP - 141 EP - 153 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Patyniak, Magda A1 - Landgraf, Angela A1 - Dzhumabaeva, Atyrgul A1 - Abdrakhmatov, Kanatbek E. A1 - Rosenwinkel, Swenja A1 - Korup, Oliver A1 - Preusser, Frank A1 - Fohlmeister, Jens Bernd A1 - Arrowsmith, J. Ramon A1 - Strecker, Manfred T1 - Paleoseismic Record of Three Holocene Earthquakes Rupturing the Issyk-Ata Fault near Bishkek, North Kyrgyzstan JF - Bulletin of the Seismological Society of America N2 - The northern edge of the western central Tien Shan range is bounded by the Issyk-Ata fault situated south of Bishkek, the capital of Kyrgyzstan. Contraction in this thick-skinned orogen occurs with low-strain accumulation and long earthquake recurrence intervals. In the nineteenth to twentieth centuries, a sequence of large earthquakes with magnitudes between 6.9 and 8 affected the northern Tien Shan but left nearly the entire extent of the Issyk-Ata fault unruptured. Here, the only known historic earthquake ruptured in A.D. 1885 (M6.9) along the western end of the Issyk-Ata fault. Because earthquakes in low-strain regions often tend to cluster in time and may promote failure along nearby structures, the earthquake history of the northern Tien Shan represents an exceptional structural setting for studying fault behavior affected by an intraplate earthquake sequence. We present a paleoseismological study from one site (Belek) along the Issyk-Ata fault located east of the A.D. 1885 epicentral area. Our analysis combines a range of tools, including photogrammetry, differential Global Positioning System, 3D visualization, and age modeling with different dating methods (infrared stimulated luminescence, radiocarbon, U-series) to improve the reliability of an event chronology for the trench stratigraphy and fault geometry. We were able to distinguish three different surfacerupturing paleoearthquakes; these affected the area before 10.5 +/- 1.1 cal ka B.P., at similar to 5.6 +/- 1.0 cal ka B.P., and at similar to 630 +/- 100 cal B.P., respectively. Associated paleomagnitudes for the last two earthquakes range between M6.7 and 7.4, with a cumulative slip rate of 0.7 +/- 0.32 mm/yr. We did not find evidence for the A.D. 1885 event at Belek. Our study yielded two main overall results: first, it extends the regional historic and paleoseismic record; second, the documented rupture events along the Issyk-Ata fault suggest that this fault was not affected in its entirety; instead, these events indicate segmented rupture behavior. Y1 - 2017 U6 - https://doi.org/10.1785/0120170083 SN - 0037-1106 SN - 1943-3573 VL - 107 SP - 2721 EP - 2737 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Castino, Fabiana A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Oscillations and trends of river discharge in the southern Central Andes and linkages with climate variability JF - Journal of hydrology N2 - This study analyzes the discharge variability of small to medium drainage basins (10(2)-10(4) km(2)) in the southern Central Andes of NW Argentina. The Hilbert-Huang Transform (HHT) was applied to evaluate non-stationary oscillatory modes of variability and trends, based on four time series of monthly normalized discharge anomaly between 1940 and 2015. Statistically significant trends reveal increasing discharge during the past decades and document an intensification of the hydrological cycle during this period. An Ensemble Empirical Mode Decomposition (EEMD) analysis revealed that discharge variability in this region can be best described by five quasi-periodic statistically significant oscillatory modes, with mean periods varying from 1 to 20 y. Moreover, we show that discharge variability is most likely linked to the phases of the Pacific Decadal Oscillation (PDO) at multi-decadal timescales (similar to 20 y) and, to a lesser degree, to the Tropical South Atlantic SST anomaly (TSA) variability at shorter timescales (similar to 2-5 y). Previous studies highlighted a rapid increase in discharge in the southern Central Andes during the 1970s, inferred to have been associated with the global 1976-77 climate shift. Our results suggest that the rapid discharge increase in the NW Argentine Andes coincides with the periodic enhancement of discharge, which is mainly linked to a negative to positive transition of the PDO phase and TSA variability associated with a long-term increasing trend. We therefore suggest that variations in discharge in this region are largely driven by both natural variability and the effects of global climate change. We furthermore posit that the links between atmospheric and hydrologic processes result from a combination of forcings that operate on different spatiotemporal scales. (C) 2017 Elsevier B.V. All rights reserved. KW - River discharge KW - Central Andes KW - Empirical Mode Decomposition KW - PDO KW - Climate variability KW - Global climate change Y1 - 2017 U6 - https://doi.org/10.1016/j.jhydrol.2017.10.001 SN - 0022-1694 SN - 1879-2707 VL - 555 SP - 108 EP - 124 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Strecker, Manfred T1 - TerraceM: A MATLAB (R) tool to analyze marine and lacustrine terraces using high-resolution topography JF - Geosphere N2 - High-resolution topographic data greatly facilitate the remote identification of geomorphic features, furnishing valuable information concerning surface processes and characterization of reference markers for quantifying tectonic deformation. Marine terraces have been used as long baseline geodetic markers of relative past sea-level positions, reflecting the interplay between vertical crustal movements and sea-level oscillations. Uplift rates may be determined from the terrace age and the elevation of its shoreline angle, a geomorphic feature that can be correlated with past sea-levels positions. A precise definition of the shoreline angle in time and space is essential to obtain reliable uplift rates with coherent spatial correlation. To improve our ability to rapidly assess and map shoreline angles at regional and local scales, we have developed TerraceM, a MATLAB (R) graphical user interface that allows the shoreline angle and its associated error to be estimated using high-resolution topography. TerraceM uses topographic swath profiles oriented orthogonally to the terrace riser. Four functions are included to analyze the swath profiles and extract the shoreline angle, from both staircase sequences of multiple terraces and rough coasts characterized by eroded remnants of emerged terrace surfaces. The former are measured by outlining the paleocliffs and paieo-platforms and finding their intersection by extrapolating linear regressions, whereas the latter are assessed by automatically detecting peaks of sea-stack tops and back-projecting them to the modern sea cliff. In the absence of rigorous absolute age determinations of marine terraces, their geomorphic age may be estimated using previously published diffusion models. Postprocessing functions are included to obtain first-order statistics of shoreline-angle elevations and their spatial distribution. TerraceM has the ability to process series of profiles from several sites in an efficient and structured workflow. Results may be exported in Google Earth and ESRI shapefile formats. The precision and accuracy of the method have been estimated from a case study at Santa Cruz, California, by comparing TerraceM results with published field measurements. The repeatability was evaluated using multiple measurements made by inexperienced users. TerraceM will improve the efficiency and precision of estimating shoreline-angle elevations in wave-cut terraces in both marine and lacustrine environments. Y1 - 2016 U6 - https://doi.org/10.1130/GES01208.1 SN - 1553-040X VL - 12 SP - 176 EP - 195 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Schildgen, Taylor F. A1 - Robinson, Ruth A. J. A1 - Savi, Sara A1 - Phillips, William M. A1 - Spencer, Joel Q. G. A1 - Bookhagen, Bodo A1 - Scherler, Dirk A1 - Tofelde, Stefanie A1 - Alonso, Ricardo N. A1 - Kubik, Peter W. A1 - Binnie, Steven A. A1 - Strecker, Manfred T1 - Landscape response to late Pleistocene climate change in NW Argentina: Sediment flux modulated by basin geometry and connectivity JF - Journal of geophysical research : Earth surface N2 - Fluvial fill terraces preserve sedimentary archives of landscape responses to climate change, typically over millennial timescales. In the Humahuaca Basin of NW Argentina (Eastern Cordillera, southern Central Andes), our 29 new optically stimulated luminescence ages of late Pleistocene fill terrace sediments demonstrate that the timing of past river aggradation occurred over different intervals on the western and eastern sides of the valley, despite their similar bedrock lithology, mean slopes, and precipitation. In the west, aggradation coincided with periods of increasing precipitation, while in the east, aggradation coincided with decreasing precipitation or more variable conditions. Erosion rates and grain size dependencies in our cosmogenic Be-10 analyses of modern and fill terrace sediments reveal an increased importance of landsliding compared to today on the west side during aggradation, but of similar importance during aggradation on the east side. Differences in the timing of aggradation and the Be-10 data likely result from differences in valley geometry, which causes sediment to be temporarily stored in perched basins on the east side. It appears as if periods of increasing precipitation triggered landslides throughout the region, which induced aggradation in the west, but blockage of the narrow bedrock gorges downstream from the perched basins in the east. As such, basin geometry and fluvial connectivity appear to strongly influence the timing of sediment movement through the system. For larger basins that integrate subbasins with differing geometries or degrees of connectivity (like Humahuaca), sedimentary responses to climate forcing are likely attenuated. KW - berylium-10 KW - optically stimulated luminescence KW - Humahuaca Basin KW - South American Monsoon System KW - fluvial terraces KW - landscape connectivity Y1 - 2016 U6 - https://doi.org/10.1002/2015JF003607 SN - 2169-9003 SN - 2169-9011 VL - 121 SP - 392 EP - 414 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Eugster, Patricia A1 - Scherler, Dirk A1 - Thiede, Rasmus Christoph A1 - Codilean, Alexandru T. A1 - Strecker, Manfred T1 - Rapid Last Glacial Maximum deglaciation in the Indian Himalaya coeval with midlatitude glaciers: New insights from Be-10-dating of ice-polished bedrock surfaces in the Chandra Valley, NW Himalaya JF - Geophysical research letters N2 - Despite a large number of dated glacial landforms in the Himalaya, the ice extent during the global Last Glacial Maximum (LGM) from 19 to 23 ka is only known to first order. New cosmogenic Be-10 exposure ages from well-preserved glacially polished surfaces, combined with published data, and an improved production rate scaling model allow reconstruction of the LGM ice extent and subsequent deglaciation in the Chandra Valley of NW India. We show that a >1000 m thick valley glacier retreated >150 km within a few thousand years after the onset of LGM deglaciation. By comparing the recession of the Chandra Valley Glacier and other Himalayan glaciers with those of Northern and Southern Hemisphere glaciers, we demonstrate that post-LGM deglaciation was similar and nearly finished prior to the Bolling/Allerod interstadial. Our study supports the view that many Himalayan glaciers advanced during the LGM, likely in response to global variations in temperature. Y1 - 2016 U6 - https://doi.org/10.1002/2015GL066077 SN - 0094-8276 SN - 1944-8007 VL - 43 SP - 1589 EP - 1597 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Bernhardt, Anne A1 - Hebbeln, Dierk A1 - Regenberg, Marcus A1 - Lueckge, Andreas A1 - Strecker, Manfred T1 - Shelfal sediment transport by an undercurrent forces turbidity-current activity during high sea level along the Chile continental margin JF - Geology N2 - Terrigenous sediment supply, marine transport, and depositional processes along tectonically active margins are key to decoding turbidite successions as potential archives of climatic and seismic forcings. Sequence stratigraphic models predict coarse-grained sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine siliciclastic deposition during transgressions and highstands has been attributed to sustained connectivity between terrigenous sources and marine sinks facilitated by narrow shelves. To decipher the controls on Holocene highstand turbidite deposition, we analyzed 12 sediment cores from spatially discrete, coeval turbidite systems along the Chile margin (29 degrees-40 degrees S) with changing climatic and geomorphic characteristics but uniform changes in sea level. Sediment cores from intraslope basins in north-central Chile (29 degrees-33 degrees S) offshore a narrow to absent shelf record a shut-off of turbidite deposition during the Holocene due to postglacial aridification. In contrast, core sites in south-central Chile (36 degrees-40 degrees S) offshore a wide shelf record frequent turbidite deposition during highstand conditions. Two core sites are linked to the Biobio river-canyon system and receive sediment directly from the river mouth. However, intraslope basins are not connected via canyons to fluvial systems but yield even higher turbidite frequencies. High sediment supply combined with a wide shelf and an undercurrent moving sediment toward the shelf edge appear to control Holocene turbidite sedimentation and distribution. Shelf undercurrents may play an important role in lateral sediment transport and supply to the deep sea and need to be accounted for in sediment-mass balances. Y1 - 2016 U6 - https://doi.org/10.1130/G37594.1 SN - 0091-7613 SN - 1943-2682 VL - 44 SP - 295 EP - 298 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Mortimer, E. J. A1 - Paton, D. A. A1 - Scholz, C. A. A1 - Strecker, Manfred T1 - Implications of structural inheritance in oblique rift zones for basin compartmentalization: Nkhata Basin, Malawi Rift (EARS) JF - Marine and petroleum geology N2 - The Cenozoic East African Rift System (EARS) is an exceptional example of active continental extension, providing opportunities for furthering our understanding of hydrocarbon plays within rifts. It is divided into structurally distinct western and eastern branches. The western branch comprises deep rift basins separated by transfer zones, commonly localised onto pre-existing structures, offering good regional scale hydrocarbon traps. At a basin-scale, local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution. Here, we consider the evolution of the Central basin of the Malawi Rift, in particular the influence of pre-existing structural fabrics. Integrating basin-scale multichannel 2D, and high resolution seismic datasets we constrain the border, Mlowe-Nkhata, fault system (MNF) to the west of the basin and smaller Mbamba fault (MF) to the east and document their evolution. Intra basin structures define a series of horsts, which initiated as convergent transfers, along the basin axis. The horsts are offset along a NE SW striking transfer fault parallel to and along strike of the onshore Karoo (Permo-Triassic) Ruhuhu graben. Discrete pre-existing structures probably determined its location and, oriented obliquely to the extension orientation it accommodated predominantly strike-slip deformation, with more slowly accrued dip-slip. To the north of this transfer fault, the overall basin architecture is asymmetric, thickening to the west throughout; while to the south, an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western MNF. The presence of the axial horst increasingly focussed sediment supply to the west. As the transfer fault increased its displacement, so this axial supply was interrupted, effectively starving the south-east while ponding sediments between the western horst margin and the transfer fault. This asymmetric bathymetry and partitioned sedimentation continues to the present-day, overprinting the early basin symmetry and configuration. Sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small (10-100 m) scale. The observed influence of basin-scale transfer faults on sediment dispersal and fault compartmentalization due to pre-existing structures oblique to the extension orientation is relevant to analogous exploration settings. (C) 2016 Elsevier Ltd. All rights reserved. KW - East African rift system KW - Structural inheritance KW - Normal fault evolution KW - Sediment distribution Y1 - 2016 U6 - https://doi.org/10.1016/j.marpetgeo.2015.12.018 SN - 0264-8172 SN - 1873-4073 VL - 72 SP - 110 EP - 121 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Pingel, Heiko A1 - Mulch, Andreas A1 - Alonso, Ricardo N. A1 - Cottle, John A1 - Hynek, Scott A. A1 - Poletti, Jacob A1 - Rohrmann, Alexander A1 - Schmitt, Axel K. A1 - Stockli, Daniel F. A1 - Strecker, Manfred T1 - Surface uplift and convective rainfall along the southern Central Andes (Angastaco Basin, NW Argentina) JF - Earth & planetary science letters N2 - Stable-isotopic and sedimentary records from the orogenic Puna Plateau of NW Argentina and adjacent intermontane basins to the east furnish a unique late Cenozoic record of range uplift and ensuing paleoenvironmental change in the south-central Andes. Today, focused precipitation in this region occurs along the eastern, windward flanks of the Eastern Cordillera and Sierras Pampeanas ranges, while the orogen interior constitutes high-elevation regions with increasingly arid conditions in a westward direction. As in many mountain belts, such hydrologic and topographic gradients are commonly mirrored by a systematic relationship between the oxygen and hydrogen stable isotope ratios of meteoric water and elevation. The glass fraction of isotopically datable volcanic ash intercalated in sedimentary sequences constitutes an environmental proxy that retains a signal of the hydrogen-isotopic composition of ancient precipitation. This isotopic composition thus helps to elucidate the combined climatic and tectonic processes associated with topographic growth, which ultimately controls the spatial patterns of precipitation in mountain belts. However, between 25.5 and 27 degrees S present-day river-based hydrogen isotope lapse rates are very low, possibly due to deep-convective seasonal storms that dominate runoff. If not accounted for, the effects of such conditions on moisture availability in the past may lead to misinterpretations of proxy-records of rainfall. Here, we present hydrogen-isotope data of volcanic glass (delta Dg), extracted from 34 volcanic ash layers in different sedimentary basins of the Eastern Cordillera and the Sierras Pampeanas. Combined with previously published delta Dg records and our refined U-Pb and (U-Th)/He zircon geochronology on 17 tuff samples, we demonstrate hydrogen-isotope variations associated with paleoenvironmental change in the Angastaco Basin, which evolved from a contiguous foreland to a fault-bounded intermontane basin during the late Mio-Pliocene. We unravel the environmental impact of Mio-Pliocene topographic growth and associated orographic effects on long-term hydrogen-isotope records of rainfall in the south-central Andes, and potentially identify temporal variations in regional isotopic lapse rates that may also apply to other regions with similar topographic boundary conditions. (C) 2016 Elsevier B.V. All rights reserved. KW - hydrogen stable isotopes KW - volcanic glass KW - paleoaltimetry KW - NW-Argentine Andes KW - orographic barrier uplift KW - convective rainfall Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.02.009 SN - 0012-821X SN - 1385-013X VL - 440 SP - 33 EP - 42 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Landgraf, Angela A1 - Dzhumabaeva, A. A1 - Abdrakhmatov, Kanatbek E. A1 - Strecker, Manfred A1 - Macaulay, E. A. A1 - Arrowsmith, J. Ramón A1 - Sudhaus, Henriette A1 - Preusser, F. A1 - Rugel, Georg A1 - Merchel, Silke T1 - Repeated large-magnitude earthquakes in a tectonically active, low-strain continental interior: The northern Tien Shan, Kyrgyzstan JF - Journal of geophysical research : Solid earth N2 - The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries. To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismological investigations at two geomorphically distinct sites (Panfilovkoe and Rot Front) near the Kyrgyz capital Bishkek. Although located near the historic epicenters, both sites were not affected by these earthquakes. Trenching was accompanied by dating stratigraphy and offset surfaces using luminescence, radiocarbon, and Be-10 terrestrial cosmogenic nuclide methods. At Rot Front, trenching of a small scarp did not reveal evidence for surface rupture during the last 5000 years. The scarp rather resembles an extensive debris-flow lobe. At Panfilovkoe, we estimate a Late Pleistocene minimum slip rate of 0.2 +/- 0.1 mm/a, averaged over at least two, probably three earthquake cycles. Dip-slip reverse motion along segmented, moderately steep faults resulted in hanging wall collapse scarps during different events. The most recent earthquake occurred around 3.6 +/- 1.3 kyr ago (1 sigma), with dip-slip offsets between 1.2 and 1.4 m. We calculate a probabilistic paleomagnitude to be between 6.7 and 7.2, which is in agreement with regional data from the Kyrgyz range. The morphotectonic signals in the northern Tien Shan are a prime example of deformation in a tectonically active intracontinental mountain belt and as such can help understand the longer-term coevolution of topography and seismogenic processes in similar structural settings worldwide. Y1 - 2016 U6 - https://doi.org/10.1002/2015JB012714 SN - 2169-9313 SN - 2169-9356 VL - 121 SP - 3888 EP - 3910 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Georgieva, Viktoria A1 - Melnick, Daniel A1 - Schildgen, Taylor F. A1 - Ehlers, Todd A1 - Lagabrielle, Yves A1 - Enkelmann, Eva A1 - Strecker, Manfred T1 - Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47 degrees S), Chile JF - Tectonics N2 - The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at similar to 47 degrees S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an similar to 140 km long fore-arc sliver-the NPI block-results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquine-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape. Y1 - 2016 U6 - https://doi.org/10.1002/2016TC004120 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 1317 EP - 1341 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Olen, Stephanie M. A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Role of climate and vegetation density in modulating denudation rates in the Himalaya JF - Earth & planetary science letters N2 - Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new Be-10 denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially-dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W-E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = -0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S-N), along strike of the orogen (i.e., E-W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation. (C) 2016 Elsevier B.V. All rights reserved. KW - geomorphology KW - erosion KW - vegetation KW - rainfall KW - Himalaya KW - 10-Be terrestrial cosmogenic nuclides Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.03.047 SN - 0012-821X SN - 1385-013X VL - 445 SP - 57 EP - 67 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Dey, Saptarshi A1 - Thiede, Rasmus Christoph A1 - Schildgen, Taylor F. A1 - Wittmann, Hella A1 - Bookhagen, Bodo A1 - Scherler, Dirk A1 - Jain, Vikrant A1 - Strecker, Manfred T1 - Climate-driven sediment aggradation and incision since the late Pleistocene in the NW Himalaya, India JF - Earth & planetary science letters N2 - Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 10(3) to 10(5) yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic Be-10 indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 +/- 3.2 ka and 43.0 +/- 2.7 ka (1 sigma). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 +/- 1.2 ka and 15.3 +/- 0.9 ka, while terraces sculpted into the upper Pleistocene-Holocene fan (AF2) provide ages of 9.3 +/- 0.4 ka (T3), 7.1 +/- 0.4 ka (T4), 5.2 +/- 0.4 ka (T5) and 3.6 +/- 0.2 ka (T6). Together with previously published OSL ages yielding the timing of aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision. (C) 2016 Elsevier B.V. All rights reserved. KW - alluvial-fan sedimentation KW - terrestrial cosmogenic nuclides KW - Indian Summer Monsoon KW - Last Glacial Maximum KW - paleo-erosion rate Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.05.050 SN - 0012-821X SN - 1385-013X VL - 449 SP - 321 EP - 331 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Radaeff, Giuditta A1 - Cosentino, Domenico A1 - Cipollari, Paola A1 - Schildgen, Taylor F. A1 - Iadanza, Annalisa A1 - Strecker, Manfred A1 - Darbas, Guldemin A1 - Gürbüz, Kemal T1 - Stratigraphic architecture of the upper Messinian deposits of the Adana Basin (southern Turkey): implications for the Messinian Salinity Crisis and the Taurus petroleum system JF - Italian journal of geosciences : bollettino della Società Geologica Italiana e del Servizio Geologico d'Italia N2 - This paper is mainly based on field work carried out on the Messinian deposits of the Adana Basin ( southern Turkey), as well as on the interpretation of seismic reflection profiles to understand 3D geometries of the basin fill. Chronostratigraphic constraints for the Messinian deposits are from micropaleontological studies on foraminifera, ostracods, and calcareous nannofossils, recently carried out on the Messinian deposits of the Adana Basin. Our results indicate that this basin developed in a marginal area strictly related to the Mediterranean realm. The Messinian deposits of the Adana Basin record all the main steps of the Messinian Salinity Crisis ( MSC) that affected the Mediterranean area at the end of the Miocene. The new stratigraphic model for the Messinian deposits of the Adana Basin provided in this work gives new insights into both the MSC and the Taurus petroleum system. Despite their complete correspondence with the MSC, the Messinian deposits of the Adana Basin show some differences with respect to the current conceptual model for the MSC. For example, in the current conceptual model for the MSC, only one regional erosional surface ( MES) characterizes the MSC deposits. In the Adana Basin, two regional erosional surfaces, named MES1 and MES2, separate the Messinian deposits related to the MSC in Lower Evaporites, Resedimented Lower Evaporites ( RLE), and upper Messinian continental deposits containing a late Lago-Mare ostracod assemblage ( mainly fluvial coarse-grained and fine-grained sediments). In some places, Brecciated Limestones lie just above the MES1 and beneath the RLE. In addition, the RLE are thought to be related to the same step that brought to the Messinian halite deposition throughout the Mediterranean, pointing to a hyperhaline environment. In contrast, the fine-grained deposits of the RLE of the Adana Basin show the occurrence of Parathetyan brackish ostracod fauna ( early Lago-Mare ostracod assemblages), which defines an oligohaline depositional environment for the RLE. In terms of hydrocarbon prospecting, the Messinian evaporites of the Adana Basin have been considered as a perfect seal for the active Taurus petroleum system. Our results show that due to the complex stratigraphic architecture of the basin fill and the occurrence of two regional erosional surfaces ( MES1 and MES2), the Messinian evaporites are discontinuously present both in surface and in the subsurface of the Adana Basin. However, seal properties in the Adana Basin could be found in the Lower Pliocene deep marine clays of the Avadan Formation. This work leads to suggest a new stratigraphical model for the Messinian deposits of the Adana Basin, allowing us to amend the classical scheme with respect to the Messinian, and to officially define some new formations within the stratigraphy of the Adana Basin. KW - eastern Mediterranean KW - Adana Basin KW - Messinian Salinity Crisis KW - physical stratigraphy KW - Messinian Erosional Surface KW - Taurus petroleum system Y1 - 2016 U6 - https://doi.org/10.3301/IJG.2015.18 SN - 2038-1719 SN - 2038-1727 VL - 135 SP - 408 EP - 424 PB - Società Geologica Italiana CY - Roma ER - TY - JOUR A1 - Rohrmann, Alexander A1 - Sachse, Dirk A1 - Mulch, Andreas A1 - Pingel, Heiko A1 - Tofelde, Stefanie A1 - Alonso, Ricardo N. A1 - Strecker, Manfred T1 - Miocene orographic uplift forces rapid hydrological change in the southern central Andes JF - Scientific reports N2 - Rainfall in the central Andes associated with the South American Monsoon and the South American Low-Level Jet results from orographic effects on atmospheric circulation exerted by the Andean Plateau and the Eastern Cordillera. However, despite its importance for South American climate, no reliable records exist that allow decoding the evolution of thresholds and interactions between Andean topography and atmospheric circulation, especially regarding the onset of humid conditions in the inherently dry southern central Andes. Here, we employ multi-proxy isotope data of lipid biomarkers, pedogenic carbonates and volcanic glass from the Eastern Cordillera of NW Argentina and present the first long-term evapotranspiration record. We find that regional eco-hydrology and vegetation changes are associated with initiation of moisture transport via the South American Low-Level Jet at 7.6 Ma, and subsequent lateral growth of the orogen at 6.5 Ma. Our results highlight that topographically induced changes in atmospheric circulation patterns, not global climate change, were responsible for late Miocene environmental change in this part of the southern hemisphere. This suggests that mountain building over time fundamentally controlled habitat evolution along the central Andes. Y1 - 2016 U6 - https://doi.org/10.1038/srep35678 SN - 2045-2322 VL - 6 SP - 4283 EP - 4306 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Nieto-Moreno, Vanesa A1 - Rohrmann, Alexander A1 - van der Meer, Marcel T. J. A1 - Damste, Jaap S. Sinninghe A1 - Sachse, Dirk A1 - Tofelde, Stefanie A1 - Niedermeyer, Eva M. A1 - Strecker, Manfred A1 - Mulch, Andreas T1 - Elevation-dependent changes in n-alkane delta D and soil GDGTs across the South Central Andes JF - Earth & planetary science letters N2 - Surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature, sometimes complicating paleoaltimetry interpretations. Thus, understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions. Lipid biomarker-based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials, in particular outside semi-arid climate zones where soil carbonates are not abundant but (soil) organic matter has a high preservation potential. Here we present delta D values of soil-derived n-alkanes and mean annual air temperature (MAT) estimates based on branched glycerol dialkyl glycerol tetraether (brGDGT) distributions to assess their potential for paleoelevation reconstructions in the southern central Andes. We analyzed soil samples across two environmental and hydrological gradients that include a hillslope (26-28 degrees S) and a valley (22-24 degrees S) transect on the windward flanks of Central Andean Eastern Cordillera in NW Argentina. Our results show that present-day n-alkane delta D values and brGDGT-based MAT estimates are both linearly related with elevation and in good agreement with present-day climate conditions. Soil n-alkanes show a delta D lapse rate (A(delta D)) of -1.64 parts per thousand/100 m (R-2 = 0.91, p < 0.01) at the hillslope transect, within the range of delta D lapse rates from precipitation and surface waters in other tropical regions in the Andes like the Eastern Cordillera in Colombia and Bolivia and the Equatorial and Peruvian Andes. BrGDGT-derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of Delta T = -0.51 degrees C/100 m (R-2 = 0.91, p < 0.01), comparable with lapse rates from in situ soil temperature measurements, satellite derived land-surface temperatures at this transect, and weather stations from the Eastern Cordillera at similar latitude. As a result of an increasing leeward sampling position along the valley transect lapse rates are biased towards lower values and display higher scatter (Delta(delta D) = -0.9 parts per thousand/100 m, R-2 = 0.76, p < 0.01 and Delta T = -0.19 degrees C/100 m, R-2 = 0.48, p < 0.05). Despite this higher complexity, they are in line with lapse rates from stream-water samples and in situ soil temperature measurements along the same transect. Our results demonstrate that both soil n-alkane delta D values and MAT reconstructions based on brGDGTs distributions from the hillslope transect (Delta(delta D) = -1.64 parts per thousand/100 m, R-2 = 0.91, p < 0.01 and Delta T = -0.51 degrees C/100 m, R-2 = 0.91, p < 0.01) track the direct effects of orography on precipitation and temperature and hence the combined effects of local and regional hydrology as well as elevation. (C) 2016 Elsevier B.V. All rights reserved. KW - South Central Andes KW - leaf-wax n-alkane delta D KW - branched GDGTs KW - MAT(mr) paleothermometer KW - paleoaltimetry proxies KW - attitudinal transects Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.07.049 SN - 0012-821X SN - 1385-013X VL - 453 SP - 234 EP - 242 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Dey, Saptarshi A1 - Thiede, Rasmus Christoph A1 - Schildgen, Taylor F. A1 - Wittmann, Hella A1 - Bookhagen, Bodo A1 - Scherler, Dirk A1 - Strecker, Manfred T1 - Holocene internal shortening within the northwest Sub-Himalaya: Out-of-sequence faulting of the Jwalamukhi Thrust, India JF - Tectonics N2 - The southernmost thrust of the Himalayan orogenic wedge that separates the foreland from the orogen, the Main Frontal Thrust, is thought to accommodate most of the ongoing crustal shortening in the Sub-Himalaya. Steepened longitudinal river profile segments, terrace offsets, and back-tilted fluvial terraces within the Kangra reentrant of the NW Sub-Himalaya suggest Holocene activity of the Jwalamukhi Thrust (JMT) and other thrust faults that may be associated with strain partitioning along the toe of the Himalayan wedge. To assess the shortening accommodated by the JMT, we combine morphometric terrain analyses with in situ Be-10-based surface-exposure dating of the deformed terraces. Incision into upper Pleistocene sediments within the Kangra Basin created two late Pleistocene terrace levels (T1 and T2). Subsequent early Holocene aggradation shortly before similar to 10ka was followed by episodic reincision, which created four cut-and-fill terrace levels, the oldest of which (T3) was formed at 10.10.9ka. A vertical offset of 445m of terrace T3 across the JMT indicates a shortening rate of 5.60.8 to 7.51.1mma(-1) over the last similar to 10ka. This result suggests that thrusting along the JMT accommodates 40-60% of the total Sub-Himalayan shortening in the Kangra reentrant over the Holocene. We speculate that this out-of-sequence shortening may have been triggered or at least enhanced by late Pleistocene and Holocene erosion of sediments from the Kangra Basin. KW - fluvial terrace KW - cosmogenic nuclides KW - steepness index KW - Jwalamukhi Thrust KW - shortening KW - orogenic wedge Y1 - 2016 U6 - https://doi.org/10.1002/2015TC004002 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 2677 EP - 2697 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mey, Jürgen A1 - Scherler, Dirk A1 - Wickert, Andrew D. A1 - Egholm, David L. A1 - Tesauro, Magdala A1 - Schildgen, Taylor F. A1 - Strecker, Manfred T1 - Glacial isostatic uplift of the European Alps JF - Nature Communications Y1 - 2016 U6 - https://doi.org/10.1038/ncomms13382 SN - 2041-1723 VL - 7 SP - 2357 EP - 2371 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Castino, Fabiana A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - River-discharge dynamics in the Southern Central Andes and the 1976-77 global climate shift JF - Geophysical research letters N2 - Recent studies have shown that the 1976-77 global climate shift strongly affected the South American climate. In our study, we observed a link between this climate shift and river-discharge variability in the subtropical Southern Central Andes. We analyzed the daily river-discharge time series between 1940 and 1999 from small to medium mountain drainage basins (10(2)-10(4) km(2) ) across a steep climatic and topographic gradient. We document that the discharge frequency distribution changed significantly, with higher percentiles exhibiting more pronounced trends. A change point between 1971 and 1977 marked an intensification of the hydrological cycle, which resulted in increased river discharge. In the upper Rio Bermejo basin of the northernmost Argentine Andes, the mean annual discharge increased by 40% over 7 years. Our findings are important for flood risk management in areas impacted by the 1976-77 climate shift; discharge frequency distribution analysis provides important insights into the variability of the hydrological cycle in the Andean realm. Y1 - 2016 U6 - https://doi.org/10.1002/2016GL070868 SN - 0094-8276 SN - 1944-8007 VL - 43 SP - 11679 EP - 11687 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Mortimer, Estelle A1 - Kirstein, Linda A. A1 - Stuart, Finlay M. A1 - Strecker, Manfred T1 - Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System JF - Earth & planetary science letters N2 - The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes. lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U-Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations. (C) 2016 Elsevier B.V. All rights reserved. KW - apatite helium thermochronology KW - normal-fault evolution KW - fault linkage KW - East African Rift System Y1 - 2016 U6 - https://doi.org/10.1016/j.epsl.2016.08.040 SN - 0012-821X SN - 1385-013X VL - 455 SP - 62 EP - 72 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Savi, Sara A1 - Schildgen, Taylor F. A1 - Tofelde, Stefanie A1 - Wittmann, Hella A1 - Scherler, Dirk A1 - Mey, Jürgen A1 - Alonso, Ricardo N. A1 - Strecker, Manfred T1 - Climatic controls on debris-flow activity and sediment aggradation: The Del Medio fan, NW Argentina JF - Journal of geophysical research : Earth surface N2 - In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentina) is located within a transition zone between subhumid and arid climates and hosts the only active debris-flow fan within this intermontane valley. By combining Be-10 analyses of boulder and sediment samples within the Del Medio catchment, with regional morphometric measurements of nearby catchments, we identify the surface processes responsible for aggradation in the Del Medio fan and their likely triggers. We find that the fan surface has been shaped by debris flows and channel avulsions during the last 400 years. Among potential tectonic, climatic, and autogenic factors that might influence deposition, our analyses point to a combination of several favorable factors that drive aggradation. These are in particular the impact of occasional abundant rainfall on steep slopes in rock types prone to failure, located in a region characterized by relatively low rainfall amounts and limited transport capacity. These characteristics are primarily associated with the climatic transition zone between the humid foreland and the arid orogen interior, which creates an imbalance between sediment supply and sediment transfer. The conditions and processes that drive aggradation in the Del Medio catchment today may provide a modern analog for the conditions and processes that drove aggradation in other nearby tributaries in the past. Y1 - 2016 U6 - https://doi.org/10.1002/2016JF003912 SN - 2169-9003 SN - 2169-9011 VL - 121 SP - 2424 EP - 2445 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Gholamrezaie, Ershad A1 - Scheck-Wenderoth, Magdalena A1 - Bott, Judith A1 - Heidbach, Oliver A1 - Strecker, Manfred T1 - 3-D crustal density model of the Sea of Marmara JF - Solid Earth N2 - Abstract. The Sea of Marmara, in northwestern Turkey, is a transition zone where the dextral North Anatolian Fault zone (NAFZ) propagates westward from the Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context of seismic hazard of Istanbul, a metropolitan area with about 15 million inhabitants. Geophysical observations indicate that the crust is heterogeneous beneath the Marmara basin, but a detailed characterization of the crustal heterogeneities is still missing. To assess if and how crustal heterogeneities are related to the NAFZ segmentation below the Sea of Marmara, we develop new crustal-scale 3-D density models which integrate geological and seismological data and that are additionally constrained by 3-D gravity modeling. For the latter, we use two different gravity datasets including global satellite data and local marine gravity observation. Considering the two different datasets and the general non-uniqueness in potential field modeling, we suggest three possible “end-member” solutions that are all consistent with the observed gravity field and illustrate the spectrum of possible solutions. These models indicate that the observed gravitational anomalies originate from significant density heterogeneities within the crust. Two layers of sediments, one syn-kinematic and one pre-kinematic with respect to the Sea of Marmara formation are underlain by a heterogeneous crystalline crust. A felsic upper crystalline crust (average density of 2720 kgm⁻³) and an intermediate to mafic lower crystalline crust (average density of 2890 kgm⁻³) appear to be cross-cut by two large, dome-shaped mafic highdensity bodies (density of 2890 to 3150 kgm⁻³) of considerable thickness above a rather uniform lithospheric mantle (3300 kgm⁻³). The spatial correlation between two major bends of the main Marmara fault and the location of the highdensity bodies suggests that the distribution of lithological heterogeneities within the crust controls the rheological behavior along the NAFZ and, consequently, maybe influences fault segmentation and thus the seismic hazard assessment in the region. KW - North Anatolian Fault KW - Shear Zone KW - Northwestern Anatolia KW - Geomechanical Model KW - Tectonic Evolution KW - Slip Distribution KW - Middle Strand KW - Pull-Apart KW - Long-Term KW - NW Turkey Y1 - 2019 U6 - https://doi.org/10.5194/se-10-785-2019 SN - 1869-9510 SN - 1869-9529 VL - 10 SP - 785 EP - 807 PB - Copernicus Publ. CY - Göttingen ER - TY - JOUR A1 - Gholamrezaie, Ershad A1 - Scheck-Wenderoth, Magdalena A1 - Sippel, Judith A1 - Strecker, Manfred T1 - Variability of the geothermal gradient across two differently aged magma-rich continental rifted margins of the Atlantic Ocean BT - the Southwest African and the Norwegian margins JF - Solid Earth N2 - Abstract. The aim of this study is to investigate the shallow thermal field differences for two differently aged passive continental margins by analyzing regional variations in geothermal gradient and exploring the controlling factors for these variations. Hence, we analyzed two previously published 3-D conductive and lithospheric-scale thermal models of the Southwest African and the Norwegian passive margins. These 3-D models differentiate various sedimentary, crustal, and mantle units and integrate different geophysical data such as seismic observations and the gravity field. We extracted the temperature–depth distributions in 1 km intervals down to 6 km below the upper thermal boundary condition. The geothermal gradient was then calculated for these intervals between the upper thermal boundary condition and the respective depth levels (1, 2, 3, 4, 5, and 6 km below the upper thermal boundary condition). According to our results, the geothermal gradient decreases with increasing depth and shows varying lateral trends and values for these two different margins. We compare the 3-D geological structural models and the geothermal gradient variations for both thermal models and show how radiogenic heat production, sediment insulating effect, and thermal lithosphere–asthenosphere boundary (LAB) depth influence the shallow thermal field pattern. The results indicate an ongoing process of oceanic mantle cooling at the young Norwegian margin compared with the old SW African passive margin that seems to be thermally equilibrated in the present day. KW - radiogenic heat-production KW - European basin system KW - lower crustal bodies KW - north-atlantic KW - subsidence analysis KW - sedimentary basins KW - tectonic evolution KW - Argentine margine KW - thermal field KW - voring basin Y1 - 2018 U6 - https://doi.org/10.5194/se-9-139-2018 SN - 1869-9529 SN - 1869-9510 VL - 9 IS - 1 SP - 139 EP - 158 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Wichura, Henry A1 - Jacobs, Louis L. A1 - Lin, Andrew A1 - Polcyn, Michael J. A1 - Manthi, Fredrick K. A1 - Winkler, Dale A. A1 - Strecker, Manfred A1 - Clemens, Matthew T1 - A 17-My-old whale constrains onset of uplift and climate change in east Africa JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is similar to 17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern straptoothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates. KW - east Africa KW - Ziphiidae KW - uplift KW - drainage KW - paleoenvironment Y1 - 2015 U6 - https://doi.org/10.1073/pnas.1421502112 SN - 0027-8424 VL - 112 IS - 13 SP - 3910 EP - 3915 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Jara-Munoz, Julius A1 - Melnick, Daniel A1 - Brill, Dominik A1 - Strecker, Manfred T1 - Segmentation of the 2010 Maule Chile earthquake rupture from a joint analysis of uplifted marine terraces and seismic-cycle deformation patterns JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - The segmentation of major fault systems in subduction zones controls earthquake magnitude and location, but the causes for the existence of segment boundaries and the relationships between long-term deformation and the extent of earthquake rupture, are poorly understood. We compare permanent and seismic-cycle deformation patterns along the rupture zone of the 2010 Maule earthquake (M8.8), which ruptured 500 km of the Chile subduction margin. We analyzed the morphology of MIS-5 marine terraces using LiDAR topography and established their chronology and coeval origin with twelve luminescence ages, stratigraphy and geomorphic correlation, obtaining a virtually continuous distribution of uplift rates along the entire rupture zone. The mean uplift rate for these terraces is 0.5 m/ka. This value is exceeded in three areas, which have experienced rapid emergence of up to 1.6 m/ka; they are located at the northern, central, and southern sectors of the rupture zone, referred to as Topocalma, Carranza and Arauco, respectively. The three sectors correlate with boundaries of eight great earthquakes dating back to 1730. The Topocalma and Arauco sectors, located at the boundaries of the 2010 rupture, consist of broad zones of crustal warping with wavelengths of 60 and 90 km, respectively. These two regions coincide with the axes of oroclinal bending of the entire Andean margin and correlate with changes in curvature of the plate interface. Rapid uplift at Carranza, in turn, is of shorter wavelength and associated with footwall flexure of three crustal-scale normal faults. The uplift rate at Carranza is inversely correlated with plate coupling as well as with coseismic slip, suggesting permanent deformation may accumulate interseismically. We propose that the zones of upwarping at Arauco and Topocalma reflect changes in frictional properties of the megathrust resulting in barriers to the propagation of great earthquakes. Slip during the 1960 (M9.5) and 2010 events overlapped with the similar to 90-km-long zone of rapid uplift at Arauco; similarly, slip in 2010 and 1906 extended across the similar to 60-km-long section of the megathrust at Topocalma, but this area was completely breached by the 1730 (M similar to 9) event, which propagated southward until Carranza. Both Arauco and Topocalma show evidence of sustained rapid uplift since at least the middle Pleistocene. These two sectors might thus constitute discrete seismotectonic boundaries restraining most, but not all great earthquake ruptures. Based on our observations, such barriers might be breached during multi-segment super-cycle events. (C) 2015 Elsevier Ltd. All rights reserved. KW - LiDAR KW - Subduction earthquakes KW - Marine terraces KW - Seismotectonic segmentation KW - Permanent uplift KW - Maule earthquake KW - Coastal uplift KW - TerraceM Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.01.005 SN - 0277-3791 VL - 113 SP - 171 EP - 192 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Mey, Jürgen A1 - Scherler, Dirk A1 - Zeilinger, Gerold A1 - Strecker, Manfred T1 - Estimating the fill thickness and bedrock topography in intermontane valleys using artificial neural networks JF - Journal of geophysical research : Earth surface N2 - Thick sedimentary fills in intermontane valleys are common in formerly glaciated mountain ranges but difficult to quantify. Yet knowledge of the fill thickness distribution could help to estimate sediment budgets of mountain belts and to decipher the role of stored material in modulating sediment flux from the orogen to the foreland. Here we present a new approach to estimate valley fill thickness and bedrock topography based on the geometric properties of a landscape using artificial neural networks. We test the potential of this approach following a four-tiered procedure. First, experiments with synthetic, idealized landscapes show that increasing variability in surface slopes requires successively more complex network configurations. Second, in experiments with artificially filled natural landscapes, we find that fill volumes can be estimated with an error below 20%. Third, in natural examples with valley fill surfaces that have steeply inclined slopes, such as the Unteraar and the Rhone Glaciers in the Swiss Alps, for example, the average deviation of cross-sectional area between the measured and the modeled valley fill is 26% and 27%, respectively. Finally, application of the method to the Rhone Valley, an overdeepened glacial valley in the Swiss Alps, yields a total estimated sediment volume of 9711km(3) and an average deviation of cross-sectional area between measurements and model estimates of 21.5%. Our new method allows for rapid assessment of sediment volumes in intermontane valleys while eliminating most of the subjectivity that is typically inherent in other methods where bedrock reconstructions are based on digital elevation models. KW - sediment storage KW - sediment thickness KW - intermontane valleys KW - geomorphometry KW - artificial neural networks Y1 - 2015 U6 - https://doi.org/10.1002/2014JF003270 SN - 2169-9003 SN - 2169-9011 VL - 120 IS - 7 SP - 1301 EP - 1320 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Acosta, Veronica Torres A1 - Schildgen, Taylor F. A1 - Clarke, Brian A. A1 - Scherler, Dirk A1 - Bookhagen, Bodo A1 - Wittmann, Hella A1 - von Blanckenburg, Friedhelm A1 - Strecker, Manfred T1 - Effect of vegetation cover on millennial-scale landscape denudation rates in East Africa JF - Lithosphere N2 - The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating this concept over long time scales and across landscapes has proven to be difficult, especially in settings complicated by tectonic forcing and variable slopes. We investigate this problem by measuring cosmogenic Be-10-derived catchment-mean denudation rates across a range of climate zones and hillslope gradients in the Kenya Rift, and by comparing our results with those published from the Rwenzori Mountains of Uganda. We find that denudation rates from sparsely vegetated parts of the Kenya Rift are up to 0.13 mm/yr, while those from humid and more densely vegetated parts of the Kenya Rift flanks and the Rwenzori Mountains reach a maximum of 0.08 mm/yr, despite higher median hillslope gradients. While differences in lithology and recent land-use changes likely affect the denudation rates and vegetation cover values in some of our studied catchments, hillslope gradient and vegetation cover appear to explain most of the variation in denudation rates across the study area. Our results support the idea that changing vegetation cover can contribute to complex erosional responses to climate or land-use change and that vegetation cover can play an important role in determining the steady-state slopes of mountain belts through its stabilizing effects on the land surface. Y1 - 2015 U6 - https://doi.org/10.1130/L402.1 SN - 1941-8264 SN - 1947-4253 VL - 7 IS - 4 SP - 408 EP - 420 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Bernhardt, Anne A1 - Melnick, Daniel A1 - Jara-Munoz, Julius A1 - Argandona, Boris A1 - Gonzalez, Javiera A1 - Strecker, Manfred T1 - Controls on submarine canyon activity during sea-level highstands: The Biobio canyon system offshore Chile JF - Geosphere N2 - Newly acquired high-resolution bathymetric data (with 5 m and 2 m grid sizes) from the continental shelf off Concepcion (Chile), in combination with seismic reflection profiles, reveal a distinctly different evolution for the Biobio submarine canyon compared to that of one of its tributaries. Both canyons are incised into the shelf of the active margin. Whereas the inner shelf appears to be mantled with unconsolidated sediment, the outer shelf shows the influence of strong bottom currents that form drifts of loose sediment and transport -material into the Biobio submarine canyon and onto the continental slope. The main stem of the Biobio Canyon is connected to the mouth of the Biobio River and currently provides a conduit for terrestrial sediment from the continental shelf to the deep seafloor. In contrast, the head of its tributary closest to the coast is located similar to 24 km offshore of the present-day coastline at 120 m water depth, and it is subject to passive sedimentation. However, canyon activity within the study area is interpreted to be controlled not only by the direct input of fluvial sediments into the canyon head facilitated by the river-mouth to canyon-head connection, but also by input from southward-directed bottom currents and possibly longshore drift. In addition, about 24 km offshore of the present-day coastline, the main stem of the Biobio Canyon has steep canyon walls next to sites of active tectonic deformation that are prone to wall failure. Mass-failure events may also foster turbidity currents and contribute to canyon feeding. In contrast, the tributary has less steep canyon walls with limited evidence of canyon-wall failure and is located down-system of bottom currents from the Biobio Canyon. It consequently receives neither fluvial nor longshore sediments. Therefore, the canyon's connectivity to fluvial or longshore sediment delivery pathways is affected by the distance of the canyon head from the coastline and the orientation of the canyon axis relative to the direction of bottom currents. The ability of a submarine canyon to act as an active conduit for large quantities of terrestrial sediment toward the deep sea during sea-level highstands may be controlled by several different conditions simultaneously. These include bottom current direction, structural deformation of the seafloor affecting canyon location and orientation as well as canyon-wall failure, shelf gradient and associated distance from the canyon head to the coast, and fluvial networks. The complex interplay between these factors may vary even within an individual canyon system, resulting in distinct levels of canyon activity on a regional scale. Y1 - 2015 U6 - https://doi.org/10.1130/GES01063.1 SN - 1553-040X VL - 11 IS - 4 SP - 1226 EP - 1255 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Ballato, Paolo A1 - Landgraf, Angela A1 - Schildgen, Taylor F. A1 - Stockli, Daniel F. A1 - Fox, Matthew A1 - Ghassemi, Mohammad R. A1 - Kirby, Eric A1 - Strecker, Manfred T1 - The growth of a mountain belt forced by base-level fall: Tectonics and surface processes during the evolution of the Alborz Mountains, N Iran JF - Earth & planetary science letters N2 - The idea that climatically modulated erosion may impact orogenic processes has challenged geoscientists for decades. Although modeling studies and physical calculations have provided a solid theoretical basis supporting this interaction, to date, field-based work has produced inconclusive results. The central-western Alborz Mountains in the northern sectors of the Arabia-Eurasia collision zone constitute a promising area to explore these potential feedbacks. This region is characterized by asymmetric precipitation superimposed on an orogen with a history of spatiotemporal changes in exhumation rates, deformation patterns, and prolonged, km-scale base-level changes. Our analysis suggests that despite the existence of a strong climatic gradient at least since 17.5 Ma, the early orogenic evolution (from similar to 36 to 9-6 Ma) was characterized by decoupled orographic precipitation and tectonics. In particular, faster exhumation and sedimentation along the more arid southern orogenic flank point to a north-directed accretionary flux and underthrusting of Central Iran. Conversely, from 6 to 3 Ma, erosion rates along the northern orogenic flank became higher than those in the south, where they dropped to minimum values. This change occurred during a similar to 3-Myr-long, km-scale base-level lowering event in the Caspian Sea. We speculate that mass redistribution processes along the northern flank of the Alborz and presumably across all mountain belts adjacent to the South Caspian Basin and more stable areas of the Eurasian plate increased the sediment load in the basin and ultimately led to the underthrusting of the Caspian Basin beneath the Alborz Mountains. This underthrusting in turn triggered a new phase of northward orogenic expansion, transformed the wetter northern flank into a new pro-wedge, and led to the establishment of apparent steady-state conditions along the northern orogenic flank (i.e., rock uplift equal to erosion rates). Conversely, the southern mountain front became the retro-wedge and experienced limited tectonic activity. These observations overall raise the possibility that mass-distribution processes during a pronounced erosion phase driven by base-level changes may have contributed to the inferred regional plate-tectonic reorganization of the northern Arabia-Eurasia collision during the last similar to 5 Ma. (C) 2015 Elsevier B.V. All rights reserved. KW - orogenic processes KW - surface processes KW - base-level fall KW - erosion KW - rock uplift KW - knickpoints Y1 - 2015 U6 - https://doi.org/10.1016/j.epsl.2015.05.051 SN - 0012-821X SN - 1385-013X VL - 425 SP - 204 EP - 218 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Olen, Stephanie M. A1 - Bookhagen, Bodo A1 - Hoffmann, Bernd A1 - Sachse, Dirk A1 - Adhikari, Danda P. A1 - Strecker, Manfred T1 - Understanding erosion rates in the Himalayan orogen: A case study from the Arun Valley JF - Journal of geophysical research : Earth surface N2 - Understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution. Denudation rates derived from terrestrial cosmogenic nuclides (TCNs) are commonly used to quantify erosion and bridge tectonic (Myr) and climatic (up to several kiloyears) time scales. However, how the processes of erosion in active orogens are ultimately reflected in Be-10 TCN samples remains a topic of discussion. We investigate this problem in the Arun Valley of eastern Nepal with 34 new Be-10-derived catchment-mean denudation rates. The Arun Valley is characterized by steep north-south gradients in topography and climate. Locally, denudation rates increase northward, from <0.2mmyr(-1) to similar to 1.5mmyr(-1) in tributary samples, while main stem samples appear to increase downstream from similar to 0.2mmyr(-1) at the border with Tibet to 0.91mmyr(-1) in the foreland. Denudation rates most strongly correlate with normalized channel steepness (R-2=0.67), which has been commonly interpreted to indicate tectonic activity. Significant downstream decrease of Be-10 concentration in the main stem Arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample. This results in Be-10 concentrations and denudation rates that do not uniformly represent the upstream catchment area. We observe strong impacts on Be-10 concentrations from local, nonfluvial geomorphic processes, such as glaciation and landsliding coinciding with areas of peak rainfall rates, pointing toward climatic modulation of predominantly tectonically driven denudation rates. Y1 - 2015 U6 - https://doi.org/10.1002/2014JF003410 SN - 2169-9003 SN - 2169-9011 VL - 120 IS - 10 SP - 2080 EP - 2102 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Scherler, Dirk A1 - Bookhagen, Bodo A1 - Wulf, Hendrik A1 - Preusser, Frank A1 - Strecker, Manfred T1 - Increased late Pleistocene erosion rates during fluvial aggradation in the Garhwal Himalaya, northern India JF - Earth & planetary science letters N2 - The response of surface processes to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Himalaya, most large rivers feature prominent fill terraces that record an imbalance between sediment supply and transport capacity, presumably due to past fluctuations in monsoon precipitation and/or effects of glaciation at high elevation. Here, we present volume estimates, chronological constraints, and Be-10-derived paleo-erosion rates from a prominent valley fill in the Yamuna catchment, Garhwal Himalaya, to elucidate the coupled response of rivers and hillslopes to Pleistocene climate change. Although precise age control is complicated due to methodological problems, the new data support formation of the valley fill during the late Pleistocene and its incision during the Holocene. We interpret this timing to indicate that changes in discharge and river-transport capacity were major controls. Compared to the present day, late Pleistocene hillslope erosion rates were higher by a factor of similar to 2-4, but appear to have decreased during valley aggradation. The higher late Pleistocene erosion rates are largely unrelated to glacial erosion and could be explained by enhanced sediment production on steep hillslopes due to increased periglacial activity that declined as temperatures increased. Alternatively, erosion rates that decrease during valley aggradation are also consistent with reduced landsliding from threshold hillslopes as a result of rising base levels. In that case, the similarity of paleo-erosion rates near the end of the aggradation period with modern erosion rates might imply that channels and hillslopes are not yet fully coupled everywhere and that present-day hillslope erosion rates may underrepresent long-term incision rates. (C) 2015 Elsevier B.V. All rights reserved. KW - paleo-erosion rates KW - climate change KW - river terraces KW - landscape evolution KW - hillslopes KW - Himalaya Y1 - 2015 U6 - https://doi.org/10.1016/j.epsl.2015.06.034 SN - 0012-821X SN - 1385-013X VL - 428 SP - 255 EP - 266 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Strecker, Manfred T1 - Assessing tectonic and climatic causal mechanisms in foreland-basin stratal architecture: insights from the Alborz Mountains, northern Iran JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - The southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3-km-thick sequence of Miocene sedimentary rocks, constituting three basin-wde coarsening-upward units spanning a period of 10(6)years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment-provenance data to characterize the relationships between tectonically-generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S>1, typical of each basal unit (17.5-16.0, 13.8-13.1 and 10.3-9.6Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S<1 (13.8 and 13.8-11Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra-basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S<1, at 11-10.3Ma and 9-6-7.6Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically-induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. KW - sediment supply KW - climatic and tectonic forcing KW - accommodation-space KW - sediment-supply ratio (A /S) KW - foreland-basin stratigraphy KW - Alborz Mountains Y1 - 2014 U6 - https://doi.org/10.1002/esp.3480 SN - 0197-9337 SN - 1096-9837 VL - 39 IS - 1 SP - 110 EP - 125 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Schildgen, Taylor F. A1 - Yildirim, C. A1 - Cosentino, Domenico A1 - Strecker, Manfred T1 - Linking slab break-off, Hellenic trench retreat, and uplift of the Central and Eastern Anatolian plateaus JF - Earth science reviews : the international geological journal bridging the gap between research articles and textbooks KW - Anatolian plateau KW - Surface uplift KW - North Anatolian Fault KW - Slab break-off KW - Eratosthenes Seamount KW - Hellenic trench Y1 - 2014 U6 - https://doi.org/10.1016/j.earscirev.2013.11.006 SN - 0012-8252 SN - 1872-6828 VL - 128 SP - 147 EP - 168 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Scherler, Dirk A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Tectonic control on Be-10-derived erosion rates in the Garhwal Himalaya, India JF - Journal of geophysical research : Earth surface N2 - Erosion in the Himalaya is responsible for one of the greatest mass redistributions on Earth and has fueled models of feedback loops between climate and tectonics. Although the general trends of erosion across the Himalaya are reasonably well known, the relative importance of factors controlling erosion is less well constrained. Here we present 25 Be-10-derived catchment-averaged erosion rates from the Yamuna catchment in the Garhwal Himalaya, northern India. Tributary erosion rates range between similar to 0.1 and 0.5mmyr(-1) in the Lesser Himalaya and similar to 1 and 2mmyr(-1) in the High Himalaya, despite uniform hillslope angles. The erosion-rate data correlate with catchment-averaged values of 5 km radius relief, channel steepness indices, and specific stream power but to varying degrees of nonlinearity. Similar nonlinear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion and that twofold to threefold differences in annual runoff are of minor importance in this area. Instead, the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock uplift pattern is largely controlled by the shortening rate and the geometry of the Main Himalayan Thrust fault (MHT). Our data support a shallow dip of the MHT underneath the Lesser Himalaya, followed by a midcrustal ramp underneath the High Himalaya, as indicated by geophysical data. Finally, analysis of sample results from larger main stem rivers indicates significant variability of Be-10-derived erosion rates, possibly related to nonproportional sediment supply from different tributaries and incomplete mixing in main stem channels. KW - Himalaya KW - erosion KW - tectonics KW - cosmogenic nuclides KW - channel steepness KW - stream power Y1 - 2014 U6 - https://doi.org/10.1002/2013JF002955 SN - 2169-9003 SN - 2169-9011 VL - 119 IS - 2 SP - 83 EP - 105 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Scherler, Dirk A1 - Munack, Henry A1 - Mey, Jürgen A1 - Eugster, Patricia A1 - Wittmann, Hella A1 - Codilean, Alexandru T. A1 - Kubik, Peter A1 - Strecker, Manfred T1 - Ice dams, outburst floods, and glacial incision at the western margin of the Tibetan Plateau: A > 100 k.y. chronology from the Shyok Valley, Karakoram JF - Geological Society of America bulletin N2 - Some of the largest and most erosive floods on Earth result from the failure of glacial dams. While potentially cataclysmic ice dams are recognized to have repeatedly formed along ice-sheet margins, much less is known about the frequency and longevity of ice dams caused by mountain glaciers, and their impact on landscape evolution. Here we present field observations and results from cosmogenic nuclide dating that allow reconstructing a > 100-k.y.-long history of glacial damming in the Shyok Valley, eastern Karakoram (South Asia). Our field observations provide evidence that Asia's second-longest glacier, the Siachen, once extended for over 180 km and blocked the Shyok River during the penultimate glacial period, leading to upstream deposition of a more than 400-m-thick fluvio-lacustrine valley fill. Be-10-depth profile modeling indicates that glacial damming ended with the onset of the Eemian interglacial and that the Shyok River subsequently incised the valley fill at an average rate of similar to 4-7 m k.y.(-1). Comparison with contemporary ice-dammed lakes in the Karakoram and elsewhere suggests recurring outburst floods during the aggradation period, while over 25 cycles of fining-upward lake deposits within the valley fill indicate impounding of floods from farther upstream. Despite prolonged damming, the net effect of this and probably earlier damming episodes by the Siachen Glacier is dominated by glacial erosion in excess of fluvial incision, as evidenced by a pronounced overdeepening that follows the glaciated valley reach. Strikingly similar overdeepened valleys at all major confluences of the Shyok and Indus Rivers with Karakoram tributaries indicate that glacial dams and subsequent outburst floods have been widespread and frequent in this region during the Quaternary. Our study suggests that the interaction of Karakoram glaciers with the Shyok and Indus Rivers promoted valley incision and headward erosion into the western margin of the Tibetan Plateau. Y1 - 2014 U6 - https://doi.org/10.1130/B30942.1 SN - 0016-7606 SN - 1943-2674 VL - 126 IS - 5-6 SP - 738 EP - 758 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Schildgen, Taylor F. A1 - Cosentino, D. A1 - Frijia, Gianluca A1 - Castorina, F. A1 - Dudas, F. Oe. A1 - Iadanza, A. A1 - Sampalmieri, G. A1 - Cipollari, Paola A1 - Caruso, A. A1 - Bowring, S. A. A1 - Strecker, Manfred T1 - Sea level and climate forcing of the Sr isotope composition of late Miocene Mediterranean marine basins JF - Geochemistry, geophysics, geosystems N2 - Sr isotope records from marginal marine basins track the mixing between seawater and local continental runoff, potentially recording the effects of sea level, tectonic, and climate forcing in marine fossils and sediments. Our 110 new Sr-87/Sr-86 analyses on oyster and foraminifera samples from six late Miocene stratigraphic sections in southern Turkey, Crete, and Sicily show that Sr-87/Sr-86 fell below global seawater values in the basins several million years before the Messinian Salinity Crisis, coinciding with tectonic uplift and basin shallowing. 87Sr/86Sr from more centrally located basins (away from the Mediterranean coast) drop below global seawater values only during the Messinian Salinity Crisis. In addition to this general trend, 55 new Sr-87/Sr-86 analyses from the astronomically tuned Lower Evaporites in the central Apennines (Italy) allow us to explore the effect of glacio-eustatic sea level and precipitation changes on Sr-87/Sr-86. Most variation in our data can be explained by changes in sea level, with greatest negative excursions from global seawater values occurring during relative sea level lowstands, which generally coincided with arid conditions in the Mediterranean realm. We suggest that this greater sensitivity to lowered sea level compared with higher runoff could relate to the inverse relationship between Sr concentration and river discharge. Variations in the residence time of groundwater within the karst terrain of the circum-Mediterranean region during arid and wet phases may help to explain the single (robust) occurrence of a negative excursion during a sea level highstand, but this explanation remains speculative without more detailed paleoclimatic data for the region. Y1 - 2014 U6 - https://doi.org/10.1002/2014GC005332 SN - 1525-2027 VL - 15 IS - 7 SP - 2964 EP - 2983 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Pingel, Heiko A1 - Alonso, Ricardo N. A1 - Mulch, Andreas A1 - Rohrmann, Alexander A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Pliocene orographic barrier uplift in the southern Central Andes JF - Geology N2 - Sedimentary basin fills along the windward flanks of orogenic plateaus are valuable archives of paleoenvironmental change with the potential to resolve the history of surface uplift and orographic barrier formation. The intermontane basins of the southern Central Andes contain thick successions of sedimentary material that are commonly interbedded with datable volcanic ashes. We relate variations in the hydrogen isotopic composition of hydrated volcanic glass (delta D-g) of Neogene to Quaternary fills in the semiarid intermontane Humahuaca Basin (Eastern Cordillera, northwest Argentina) to spatiotemporal changes in topography and associated orographic effects. delta D values from volcanic glass in the basin strata (-117 parts per thousand to -98 parts per thousand) show two main trends that accompany observed tectonosedimentary events in the study area. Between 6.0 and 3.5 Ma, delta D-g values decrease by similar to 17 parts per thousand; this is associated with surface uplift in the catchment area. After 3.5 Ma, delta D-g values show abrupt deuterium enrichment, which we associate with (1) the attainment of threshold elevations for blocking moisture transport in the basin-bounding ranges to the east, and (2) the onset of semiarid conditions in the basin. Such orographic barriers throughout the eastern flanks of the Central Andes have impeded moisture transport into the orogen interior; this has likely helped maintain aridity and internal drainage conditions on the adjacent Andean Plateau. Y1 - 2014 U6 - https://doi.org/10.1130/G35538.1 SN - 0091-7613 SN - 1943-2682 VL - 42 IS - 8 SP - 691 EP - 694 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Schoenbohm, Lindsay M. A1 - Chen, Jie A1 - Stutz, Jamey A1 - Sobel, Edward A1 - Thiede, Rasmus Christoph A1 - Kirby, Benjamin A1 - Strecker, Manfred T1 - Glacial morphology in the Chinese Pamir: Connections among climate, erosion, topography, lithology and exhumation JF - Geomorphology : an international journal on pure and applied geomorphology N2 - Modification of the landscape by glacial erosion reflects the dynamic interplay of climate through temperature, precipitation, and prevailing wind direction, and tectonics through rock uplift and exhumation rate, lithology, and range and fault geometry. We investigate these relationships in the northeast Pamir Mountains using mapping and dating of moraines and terraces to determine the glacial history. We analyze modem glacial morphology to determine glacier area, spacing, headwall relief, debris cover, and equilibrium line altitude (ELA) using the area x altitude balance ratio (AABR), toe-to-headwall altitude ratio (THAR) and toe-to-summit altitude method (TSAM) for 156 glaciers and compare this to lithologic, tectonic, and climatic data We observe a pronounced asymmetry in glacial ELA, area, debris cover, and headwall relief that we interpret to reflect both structural and climatic control: glaciers on the downwind (eastern) side of the range are larger, more debris covered, have steeper headwalls, and tend to erode headward, truncating the smaller glaciers of the upwind, fault-controlled side of the range. We explain this by the transfer of moisture deep into the range as wind-blown or avalanched snow and by limitations imposed on glacial area on the upwind side of the range by the geometry of the Kongur extensional system (KES). The correspondence between rapid exhumation along the KES and maxima in glacier debris cover and headwall relief and minimums in all measures of ELA suggest that taller glacier headwalls develop in a response to more rapid exhumation rates. However, we find that glaciers in the Muji valley did not extend beyond the range front until at least 43 ka, in contrast to extensive glaciation since 300 ka in the south around the high peaks, a pattern which does not clearly reflect uplift rate. Instead, the difference in glacial history and the presence of large peaks (Muztagh Ata and Kongur Shan) with flanking glaciers likely reflects lithologic control (i.e., the location of crustal gneiss domes) and the formation of peaks that rise above the ELA and escape the glacial buzzsaw. (C) 2014 Elsevier B.V. All rights reserved. KW - Pamir KW - ELA KW - Cosmogenic nuclides KW - Glaciation KW - Glacial buzzsaw KW - Tectonic-climate coupling Y1 - 2014 U6 - https://doi.org/10.1016/j.geomorph.2014.05.023 SN - 0169-555X SN - 1872-695X VL - 221 SP - 1 EP - 17 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hoke, Gregory D. A1 - Giambiagi, Laura B. A1 - Garzione, Carmala N. A1 - Mahoney, J. Brian A1 - Strecker, Manfred T1 - Neogene paleoelevation of intermontane basins in a narrow, compressional mountain range, southern Central Andes of Argentina JF - Earth & planetary science letters KW - Neogene KW - Andes KW - surface uplift KW - tectonics KW - paleoelevation Y1 - 2014 U6 - https://doi.org/10.1016/j.epsl.2014.08.032 SN - 0012-821X SN - 1385-013X VL - 406 SP - 153 EP - 164 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Montero-Lopez, Carolina A1 - Strecker, Manfred A1 - Schildgen, Taylor F. A1 - Hongn, Fernando D. A1 - Guzman, Silvina A1 - Bookhagen, Bodo A1 - Sudo, Masafumi T1 - Local high relief at the southern margin of the Andean plateau by 9 Ma: evidence from ignimbritic valley fills and river incision JF - Terra nova N2 - A valley-filling ignimbrite re-exposed through subsequent river incision at the southern margin of the Andean (Puna) plateau preserves pristine geological evidence of pre-late Miocene palaeotopography in the north western Argentine Andes. Our new Ar-40/(39) Ar dating of the Las Papas Ignimbrites yields a plateau age of 9.24 +/- 0.03 Ma, indicating valley-relief and orographic-barrier conditions comparable to the present-day. A later infill of Plio-Pleistocene coarse conglomerates has been linked to wetter conditions, but resulted in no additional net incision of the Las Papas valley, considering that the base of the ignimbrite remains unexposed in the valley bottom. Our observations indicate that at least 550 m of local plateau margin relief (and likely > 2 km) existed by 9 Ma at the southern Puna margin, which likely aided the efficiency of the orographic barrier to rainfall along the eastern and south eastern flanks of the Puna and causes aridity in the plateau interior. Y1 - 2014 U6 - https://doi.org/10.1111/ter.12120 SN - 0954-4879 SN - 1365-3121 VL - 26 IS - 6 SP - 454 EP - 460 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Rohrmann, Alexander A1 - Strecker, Manfred A1 - Bookhagen, Bodo A1 - Mulch, Andreas A1 - Sachse, Dirk A1 - Pingel, Heiko A1 - Alonso, Ricardo N. A1 - Schildgen, Taylor F. A1 - Montero, Carolina T1 - Can stable isotopes ride out the storms? The role of convection for water isotopes in models, records, and paleoaltimetry studies in the central Andes JF - Earth & planetary science letters KW - stable isotopes KW - Andes KW - precipitation KW - convection KW - paleoaltimetry KW - TRMM satellite data Y1 - 2014 U6 - https://doi.org/10.1016/j.epsl.2014.09.021 SN - 0012-821X SN - 1385-013X VL - 407 SP - 187 EP - 195 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Uba, Cornelius Eji A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Sudo, Masafumi A1 - Stockli, Daniel F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran JF - Geological Society of America bulletin N2 - A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone. Y1 - 2011 U6 - https://doi.org/10.1130/B30091.1 SN - 0016-7606 VL - 123 IS - 1-2 SP - 106 EP - 131 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Scherler, Dirk A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Spatially variable response of Himalayan glaciers to climate change affected by debris cover JF - Nature geoscience N2 - Controversy about the current state and future evolution of Himalayan glaciers has been stirred up by erroneous statements in the fourth report by the Intergovernmental Panel on Climate Change(1,2). Variable retreat rates(3-6) and a paucity of glacial mass-balance data(7,8) make it difficult to develop a coherent picture of regional climate-change impacts in the region. Here, we report remotely-sensed frontal changes and surface velocities from glaciers in the greater Himalaya between 2000 and 2008 that provide evidence for strong spatial variations in glacier behaviour which are linked to topography and climate. More than 65% of the monsoon-influenced glaciers that we observed are retreating, but heavily debris-covered glaciers with stagnant low-gradient terminus regions typically have stable fronts. Debris-covered glaciers are common in the rugged central Himalaya, but they are almost absent in subdued landscapes on the Tibetan Plateau, where retreat rates are higher. In contrast, more than 50% of observed glaciers in the westerlies-influenced Karakoram region in the northwestern Himalaya are advancing or stable. Our study shows that there is no uniform response of Himalayan glaciers to climate change and highlights the importance of debris cover for understanding glacier retreat, an effect that has so far been neglected in predictions of future water availability(9,10) or global sea level(11). Y1 - 2011 U6 - https://doi.org/10.1038/NGEO1068 SN - 1752-0894 VL - 4 IS - 3 SP - 156 EP - 159 PB - Nature Publ. Group CY - New York ER - TY - JOUR A1 - Hain, Mathis P. A1 - Strecker, Manfred A1 - Bookhagen, Bodo A1 - Alonso, Ricardo N. A1 - Pingel, H. A1 - Schmitt, Axel K. T1 - Neogene to quaternary broken foreland formation and sedimentation dynamics in the Andes of NW Argentina (25 degrees S) JF - Tectonics N2 - The northwest Argentine Andes constitute a premier natural laboratory to assess the complex interactions between isolated uplifts, orographic precipitation gradients, and related erosion and sedimentation patterns. Here we present new stratigraphic observations and age information from intermontane basin sediments to elucidate the Neogene to Quaternary shortening history and associated sediment dynamics of the broken Salta foreland. This part of the Andean orogen, which comprises an array of basement-cored range uplifts, is located at similar to 25 degrees S and lies to the east of the arid intraorogenic Altiplano/Puna plateau. In the Salta foreland, spatially and temporally disparate range uplift along steeply dipping inherited faults has resulted in foreland compartmentalization with steep basin-tobasin precipitation gradients. Sediment architecture and facies associations record a three-phase (similar to 10, similar to 5, and <2 Ma), east directed, yet unsystematic evolution of shortening, foreland fragmentation, and ensuing changes in precipitation and sediment transport. The provenance signatures of these deposits reflect the trapping of sediments in the intermontane basins of the Andean hinterland, as well as the evolution of a severed fluvial network. Present-day moisture supply to the hinterland is determined by range relief and basin elevation. The conspiring effects of range uplift and low rainfall help the entrapment and long-term storage of sediments, ultimately raising basin elevation in the hinterland, which may amplify aridification in the orogen interior. Y1 - 2011 U6 - https://doi.org/10.1029/2010TC002703 SN - 0278-7407 VL - 30 IS - 11 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Sobel, Edward A1 - Schoenbohm, Lindsay M. A1 - Chen, Jie A1 - Thiede, Rasmus Christoph A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Late Miocene-Pliocene deceleration of dextral slip between Pamir and Tarim: Implications for Pamir orogenesis JF - EARTH AND PLANETARY SCIENCE LETTERS N2 - The timing of the late Cenozoic collision between the Pamir salient and the Tien Shan as well as changes in the relative motion between the Pamir and Tarim are poorly constrained. The northern margin of the Pamir salient indented northward by similar to 300 km during the late Cenozoic, accommodated by south-dipping intracontinental subduction along the Main Pamir Thrust (MPT) coupled to strike-slip faults on the eastern flank of the orogen and both strike-slip and thrust faults on the western margin. The Kashgar-Yecheng transfer system (KYTS) is the main dextral slip shear zone separating Tarim from the Eastern Pamir, with an estimated cumulative offset of similar to 280 km at an average late Cenozoic dextral slip rate of 11-15 mm/a (Cowgill, 2010). In order to better constrain the slip history of the KYTS, we collected thermochronologic samples along the eastward-flowing, deeply incised, antecedent Tashkorgan-Yarkand River, which crosses the fault system on the eastern flank of the orogen. We present 29 new biotite (40)Ar/(39)Ar ages, apatite and zircon (U-Th-Sm)/He ages, and apatite fission track (AFT) analysis, combined with published muscovite and biotite (40)Ar/(39)Ar and AFT data, to create a unique thermochronologic dataset in this poorly studied and remote region. We constrain the timing of four major N-trending faults: the latter three are strands of the KYTS. The westernmost, the Kuke fault, experienced significant dip-slip, west-side-up displacement between > 12 and 6 Ma. To the east, within the KYTS, our new thermochronologic data and geomorphic observations suggest that the Kumtag and Kusilaf dextral slip faults have been inactive since at least 3-5 Ma. Long-term incision rates across the Aertashi dextral slip fault, the easternmost strand of the KYTS, are compatible with slow horizontal slip rates of 1.7-5.3 mm/a over the past 3 to 5 Ma. In summary, these data show that the slip rate of the KYTS decreased substantially during the late Miocene or Pliocene. Furthermore, Miocene-present regional kinematic reconstructions suggest that this deceleration reflects the substantial increase of northward motion of Tarim rather than a significant decrease of the northward velocity of the Pamir. (C) 2011 Elsevier B.V. All rights reserved. KW - thermochronology KW - neotectonics KW - Pamir KW - Tien Shan KW - strike-slip fault KW - intracontinental subduction Y1 - 2011 U6 - https://doi.org/10.1016/j.epsl.2011.02.012 SN - 0012-821X VL - 304 IS - 3-4 SP - 369 EP - 378 PB - ELSEVIER SCIENCE BV CY - AMSTERDAM ER - TY - JOUR A1 - Deeken, Anke A1 - Thiede, Rasmus Christoph A1 - Sobel, Edward A1 - Hourigan, J. K. A1 - Strecker, Manfred T1 - Exhumational variability within the Himalaya of northwest India JF - Earth & planetary science letters N2 - In the Himalaya of Chamba, NW India, a major orographic barrier in front of the Greater Himalayan Range extracts a high proportion of the monsoonal rainfall along its southern slopes and effectively shields the orogen interior from moisture-bearing winds. Along a similar to 100-km-long orogen perpendicular transect, 28 new apatite fission track (AFT) and 30 new zircon (U-Th)/He (ZHe) cooling ages reveal marked variations in age distributions and long-term exhumation rates between the humid frontal range and the semi-arid orogen interior. On the southern topographic front, very young, elevation-invariant AFT ages of <4 Ma have been obtained that are concentrated in a similar to 30-km-wide zone; 1-D-thermal modeling suggests a Plio-Pleistocene mean erosion rate of 0.8-1.9 mm yr(-1). In contrast, AFT and ZHe ages within the orogen interior are older (4-9 and 7-18 Ma, respectively), are positively correlated with sample elevation, and yield lower mean erosion rates (0.3-0.9 mm yr(-1)). Protracted low exhumation rates within the orogen interior over the last similar to 15 Myr prevailed contemporaneously with overall humid conditions and an effective erosional regime within the southern Himalaya. This suggests that the frontal Dhauladar Range was sufficiently high during this time to form an orographic barrier, focusing climatically enhanced erosional processes and tectonic deformation there. Thrusting along the two frontal range-bounding thrust, the Main Central Thrust and the Main Boundary Thrusts, was initiated at least similar to 15 Ma ago and has remained localized since then. The lack of evidence for localized uplift farther north indicates either a rather flat decollement with no ramp or the absence of active duplex systems beneath the interior of Chamba. Exhumational variability within Chamba is best explained as the result of continuous thrusting along a major basal decollement, with a flat beneath the slowly exhuming internal compartments and a steep frontal ramp at the rapidly exhuming frontal range. The pattern in Chamba contrasts with what is observed elsewhere along the Himalaya, where exhumation is focused in a zone similar to 150 km north of the orogenic front. In the NW Himalaya, preserved High Himalayan Crystalline nappes and Lesser Himalayan windows alternate on a relatively small scale of <100 km; these alternations are closely correlated with the pattern of exhumation. Although the spatial distribution of high-exhumation zones varies considerably between individual Himalayan sectors, all of these zones are closely correlated with locally higher rock-uplift rates, sharp topographic discontinuities, and focused orographic precipitation, suggesting strong feedbacks between tectonically driven rock uplift, orographically enhanced precipitation, and erosional processes. KW - apatite fission-track KW - zircon uranium-thorium-helium KW - thermochronology KW - exhumation KW - Himalaya KW - Haimantas Y1 - 2011 U6 - https://doi.org/10.1016/j.epsl.2011.02.045 SN - 0012-821X VL - 305 IS - 1-2 SP - 103 EP - 114 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Scherler, Dirk A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Hillslope-glacier coupling the interplay of topography and glacial dynamics in High Asia JF - Journal of geophysical research : Earth surface N2 - High Asian glacial landscapes have large variations in topographic relief and the size and steepness of snow accumulation areas. Associated differences in glacial cover and dynamics allow a first-order determination of the dominant processes shaping these landscapes. Here we provide a regional synthesis of the topography and flow characteristics of 287 glaciers across High Asia using digital elevation analysis and remotely sensed glacier surface velocities. Glaciers situated in low-relief areas on the Tibetan Plateau are mainly nourished by direct snowfall, have little or no debris cover, and have a relatively symmetrical distribution of velocities along their length. In contrast, avalanche-fed glaciers with steep accumulation areas, which occur at the deeply incised edges of the Tibetan Plateau, are heavily covered with supraglacial debris, and flow velocities are highest along short segments near their headwalls but greatly reduced along their debris-mantled lower parts. The downstream distribution of flow velocities suggests that the glacial erosion potential is progressively shifted upstream as accumulation areas get steeper and hillslope debris fluxes increase. Our data suggest that the coupling of hillslopes and glacial dynamics increases with topographic steepness and debris cover. The melt-lowering effect of thick debris cover allows the existence of glaciers even when they are located entirely below the snow line. However, slow velocities limit the erosion potential of such glaciers, and their main landscape-shaping contribution may simply be the evacuation of debris from the base of glacial headwalls, which inhibits the formation of scree slopes and thereby allows ongoing headwall retreat by periglacial hillslope processes. We propose a conceptual model in which glacially influenced plateau margins evolve from low-relief to high-relief landscapes with distinctive contributions of hillslope processes and glaciers to relief production and decay. Y1 - 2011 U6 - https://doi.org/10.1029/2010JF001751 SN - 0148-0227 VL - 116 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Hintersberger, Esther A1 - Thiede, Rasmus Christoph A1 - Strecker, Manfred T1 - The role of extension during brittle deformation within the NW Indian Himalaya JF - Tectonics N2 - Synorogenic extension has been recognized as an integral structural constituent of mountain belts and high-elevation plateaus during their evolution. In the Himalaya, both orogen-parallel and orogen-normal extension has been recognized. However, the underlying driving forces for extension and their timing are still a matter of debate. Here we present new fault kinematic data based on systematic measurements of hundreds of outcrop-scale brittle fault planes in the NW Indian Himalaya. This new data set, as well as field observations including crosscutting relationships, mineral fibers on fault planes, and correlations with deformation structures in lake sediments, allows us to distinguish different deformation styles. The overall strain pattern derived from our data reflects the large regional contractional deformation pattern very well but also reveals significant extensional deformation in a region, which is dominated by shortening. In total, we were able to identify six deformation styles, most of which are temporally and spatially linked, representing protracted shortening. Our observations also furnish the basis for a detailed overview of the younger deformation history in the NW Himalaya, which has been characterized by extension overprinting previously generated structures related to shortening. The four dominant deformation styles are (1) shortening parallel to the regional convergence direction; (2) arc-normal extension; (3) arc-parallel extension; and finally, (4) E-W extension. This is the first data set where a succession of both arc-normal and E-W extension has been documented in the Himalaya. Importantly, our observations help differentiate E-W extension triggered by processes within the Tibetan Plateau from arc-parallel and arc-normal extension originating from the curvature of the Himalayan orogen. Y1 - 2011 U6 - https://doi.org/10.1029/2010TC002822 SN - 0278-7407 VL - 30 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Yildirim, Cengiz A1 - Schildgen, Taylor F. A1 - Echtler, Helmut Peter A1 - Melnick, Daniel A1 - Strecker, Manfred T1 - Late Neogene and active orogenic uplift in the Central Pontides associated with the North Anatolian Fault implications for the northern margin of the Central Anatolian Plateau, Turkey JF - Tectonics N2 - Surface uplift at the northern margin of the Central Anatolian Plateau (CAP) is integrally tied to the evolution of the Central Pontides (CP), between the North Anatolian Fault (NAF) and the Black Sea. Our regional morphometric and plate kinematic analyses reveal topographic anomalies, steep channel gradients, and local high relief areas as indicators of ongoing differential surface uplift, which is higher in the western CP compared to the eastern CP and fault-normal components of geodetic slip vectors and the character of tectonic activity of the NAF suggest that stress is accumulated in its broad restraining bend. Seismic reflection and structural field data show evidence for a deep structural detachment horizon responsible for the formation of an actively northward growing orogenic wedge with a positive flower-structure geometry across the CP and the NAF. Taken together, the tectonic, plate kinematic, and geomorphic observations imply that the NAF is the main driving mechanism for wedge tectonics and uplift in the CP. In addition, the NAF Zone defines the boundary between the extensional CAP and the contractional CP. The syntectonic deposits within inverted intermontane basins and deeply incised gorges suggest that the formation of relief, changes in sedimentary dynamics, and > 1 km fluvial incision resulted from accelerated uplift starting in the early Pliocene. The Central Pontides thus provide an example of an accretionary wedge with surface-breaking faults that play a critical role in mountain building processes, sedimentary basin development, and ensuing lateral growth of a continental plateau since the end of the Miocene. Y1 - 2011 U6 - https://doi.org/10.1029/2010TC002756 SN - 0278-7407 VL - 30 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Cosentino, Domenico A1 - Schildgen, Taylor F. A1 - Cipollari, Paola A1 - Faranda, Costanza A1 - Gliozzi, Elsa A1 - Hudackova, Natalia A1 - Lucifora, Stella A1 - Strecker, Manfred T1 - Late Miocene surface uplift of the southern margin of the Central Anatolian Plateau, Central Taurides, Turkey JF - Geological Society of America bulletin N2 - The timing and pattern of surface uplift of Miocene marine sediments capping the southern margin of the Central Anatolian Plateau in southern Turkey provide a first-order constraint on possible mechanisms of regional uplift. Nannofossil, ostracod, and planktic foraminifera biostratigraphy of the Basyayla section (Mut-Ermenek Basin) within the Mut and Kfiselerli Formations suggests a Tortonian age for marine sediments unconformably capping basement rocks at 2 km elevation. The identification of biozone MMi 12a (7.81-8.35 Ma) from planktic foraminifera in the upper part of the section provides the tightest constraint on the age, which is further limited to 8.35-8.108 Ma as a result of the reverse polarity of the collected samples (chron 4r.1 r or 4r.2r). This provides a limiting age for the onset of surface uplift at the margin of one of the world's major orogenic plateaus, from which an average uplift rate of 0.24-0.25 mm/yr can be calculated. Subhorizontal beds of the uppermost marine sediments exposed throughout the Mut-Ermenek Basin suggest minimal localized deformation, with just minor faulting at the basin margin and broad antiformal deformation across the basin. This implies that the post-8 Ma uplift mechanism must be rooted deep within the crust or in the upper mantle. Published Pn-wave velocity data for the region are compatible with topography compensated by asthenosphere across the southern margin of the plateau, showing a close match to the highest topography when elevations are filtered with a 100-km-wide smoothing window. Uplift along the southern margin of the Central Anatolian Plateau is also reflected by the pattern of Miocene marine sediments capping the margin, which form an asymmetric drape fold over the topography. These observations, together with tomographic evidence for slab steepening and break-off beneath the Eastern Anatolian Plateau, suggest that at least some of the 2 km of post-8 Ma uplift of the southern Central Anatolian Plateau margin is compensated by low-density asthenospheric mantle that upwelled following slab break-off. Y1 - 2012 U6 - https://doi.org/10.1130/B30466.1 SN - 0016-7606 VL - 124 IS - 1-2 SP - 133 EP - 145 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Scherler, Dirk A1 - Strecker, Manfred T1 - Large surface velocity fluctuations of Biafo Glacier, central Karakoram, at high spatial and temporal resolution from optical satellite images JF - Journal of glaciology N2 - Despite global warming and unlike their Himalayan neighbours, glaciers in the Karakoram mountains do not show signs of significant retreat. Here we report high velocity variations of Biafo Glacier, central Karakoram, which occurred between 2001 and 2009 and which indicate considerable dynamics in its flow behaviour. We have generated a dense time series of glacier surface velocities, based on cross-correlation of optical satellite images, which clearly shows seasonal and interannual velocity variations, reaching 50% in some places. The interannual velocity variations resemble the passing of a broad wave of high velocities, with peak velocities during 2005 and some diffusion down-glacier over a period of at least 4 years. High interannual velocity variations are also observed at other glaciers in the vicinity, suggesting a common cause, although these appear to partly comprise longer acceleration phases. Analysis of weather station data provides some indications of meteorological conditions that could have promoted sustained sliding events during this period, but this does not explain the wave-like nature of the acceleration at Biafo Glacier, and the regular, protracted velocity changes. Y1 - 2012 U6 - https://doi.org/10.3189/2012JoG11J096 SN - 0022-1430 SN - 1727-5652 VL - 58 IS - 209 SP - 569 EP - 580 PB - International Glaciological Society CY - Cambridge ER - TY - JOUR A1 - Schildgen, Taylor F. A1 - Cosentino, D. A1 - Bookhagen, Bodo A1 - Niedermann, Samuel A1 - Yildirim, C. A1 - Echtler, Helmut Peter A1 - Wittmann, Hella A1 - Strecker, Manfred T1 - Multi-phased uplift of the southern margin of the Central Anatolian plateau, Turkey a record of tectonic and upper mantle processes JF - Earth & planetary science letters N2 - Uplifted Neogene marine sediments and Quaternary fluvial terraces in the Mut Basin, southern Turkey, reveal a detailed history of surface uplift along the southern margin of the Central Anatolian plateau from the Late Miocene to the present. New surface exposure ages (Be-10, Al-26, and Ne-21) of gravels capping fluvial strath terraces located between 28 and 135 m above the Goksu River in the Mut Basin yield ages ranging from ca. 25 to 130 ka, corresponding to an average incision rate of 0.52 to 0.67 mm/yr. Published biostratigraphic data combined with new interpretations of the fossil assemblages from uplifted marine sediments reveal average uplift rates of 0.25 to 0.37 mm/yr since Late Miocene time (starting between 8 and 5.45 Ma), and 0.72 to 0.74 mm/yr after 1.66 to 1.62 Ma. Together with the terrace abandonment ages, the data imply 0.6 to 0.7 mm/yr uplift rates from 1.6 Ma to the present. The different post-Late Miocene and post-1.6 Ma uplift rates can imply increasing uplift rates through time, or multi-phased uplift with slow uplift or subsidence in between. Longitudinal profiles of rivers in the upper catchment of the Mut and Ermenek basins show no apparent lithologic or fault control on some knickpoints that occur at 1.2 to 1.5 km elevation, implying a transient response to a change in uplift rates. Projections of graded upper relict channel segments to the modern outlet, together with constraints from uplifted marine sediments, show that a slower incision/uplift rate of 0.1 to 0.2 mm/yr preceded the 0.7 mm/yr uplift rate. The river morphology and profile projections therefore reflect multi-phased uplift of the plateau margin, rather than steadily increasing uplift rates. Multi-phased uplift can be explained by lithospheric slab break-off and possibly also the arrival of the Eratosthenes Seamount at the collision zone south of Cyprus. KW - Central Anatolian plateau KW - uplift KW - fluvial strath terraces KW - cosmogenic nuclides KW - biostratigraphy KW - channel projection Y1 - 2012 U6 - https://doi.org/10.1016/j.epsl.2011.12.003 SN - 0012-821X VL - 317 SP - 85 EP - 95 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schildgen, Taylor F. A1 - Cosentino, D. A1 - Caruso, A. A1 - Buchwaldt, Robert A1 - Yildirim, C. A1 - Bowring, S. A. A1 - Rojay, B. A1 - Echtler, Helmut Peter A1 - Strecker, Manfred T1 - Surface expression of eastern Mediterranean slab dynamics: Neogene topographic and structural evolution of the southwest margin of the Central Anatolian Plateau, Turkey JF - TECTONICS N2 - The southwest margin of the Central Anatolian Plateau has experienced multiple phases of topographic growth, including the formation of localized highs prior to the Late Miocene that were later affected by wholesale uplift of the plateau margin. Our new biostratigraphic data limit the age of uplifted marine sediments at the southwest plateau margin at 1.5 km elevation to <7.17 Ma, and regional lithostratigraphic correlations imply that the age is <6.7 Ma. Single-grain CA-TIMS U-Pb zircon analyses from a reworked ash within the marine sediments yield dates as young as 10.6 Ma, indicating a maximum age that is consistent with the biostratigraphy. Our structural measurements within the uplifted region and fault inversion modeling agree with previous findings in surrounding regions, with early contraction followed by strike-slip and extensional deformation during uplift. Focal mechanisms from shallow earthquakes show that the extensional phase has continued to the present. Broad similarities in the change in the tectonic stress regime (after 8 Ma) and the onset of surface uplift (after 7 Ma) imply that deep-seated process(es) caused post-7 Ma uplift. The geometry of lithospheric slabs beneath the plateau margin, Pliocene to recent alkaline volcanism, and the uplift pattern with accompanying normal faulting point toward slab tearing and localized heating at the base of the lithosphere as a probable mechanism for post-7 Ma uplift of the southwest margin. Considering previous work in the region, there appears to be an important link between slab dynamics and surface uplift throughout the Anatolian Plateau’s southern margin. Y1 - 2012 U6 - https://doi.org/10.1029/2011TC003021 SN - 0278-7407 SN - 1944-9194 VL - 31 PB - AMER GEOPHYSICAL UNION CY - WASHINGTON ER - TY - JOUR A1 - Bookhagen, Bodo A1 - Strecker, Manfred T1 - Spatiotemporal trends in erosion rates across a pronounced rainfall gradient: Examples from the southern Central Andes JF - Earth & planetary science letters N2 - The tectonic and climatic boundary conditions of the broken foreland and the orogen interior of the southern Central Andes of northwestern Argentina cause strong contrasts in elevation, rainfall, and surface-process regimes. The climatic gradient in this region ranges from the wet, windward eastern flanks (similar to 2 m/yr rainfall) to progressively drier western basins and ranges (similar to 0.1 m/yr) bordering the arid Altiplano-Puna Plateau. In this study, we analyze the impact of spatiotemporal climatic gradients on surface erosion: First, we present 41 new catchment-mean erosion rates derived from cosmogenic nuclide inventories to document spatial erosion patterns. Second, we re-evaluate paleoclimatic records from the Calchaquies basin (66 W, 26 S), a large intermontane basin bordered by high (> 4.5 km) mountain ranges, to demonstrate temporal variations in erosion rates associated with changing climatic boundary conditions during the late Pleistocene and Holocene. Three key observations in this region emphasize the importance of climatic parameters on the efficiency of surface processes in space and time: (1) First-order spatial patterns of erosion rates can be explained by a simple specific stream power (SSP) approach. We explicitly account for discharge by routing high-resolution, satellite derived rainfall. This is important as the steep climatic gradient results in a highly non-linear relation between drainage area and discharge. This relation indicates that erosion rates (ER) scale with ER similar to SSP1.4 on cosmogenic-nuclide time scales. (2) We identify an intrinsic channel-slope behavior in different climatic compartments. Channel slopes in dry areas (< 0.25 m/yr rainfall) are slightly steeper than in wet areas (> 0.75 m/yr) with equal drainage areas, thus compensating lower amounts of discharge with steeper slopes. (3) Erosion rates can vary by an order of magnitude between presently dry (similar to 0.05 mm/yr) and well-defined late Pleistocene humid (similar to 0.5 mm/yr) conditions within an intemontane basin. Overall, we document a strong climatic impact on erosion rates and channel slopes. We suggest that rainfall reaching areas with steeper channel slopes in the orogen interior during wetter climate periods results in intensified sediment mass transport, which is primarily responsible for maintaining the balance between surface uplift, erosion, sediment routing and transient storage in the orogen. KW - erosion KW - landscape evolution KW - specific stream power KW - cosmogenic radionuclides KW - paleoclimate KW - climate-tectonic feedback processes Y1 - 2012 U6 - https://doi.org/10.1016/j.epsl.2012.02.005 SN - 0012-821X VL - 327 IS - 8 SP - 97 EP - 110 PB - Elsevier CY - Amsterdam ER -