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