@article{CastinoBookhagenStrecker2016, author = {Castino, Fabiana and Bookhagen, Bodo and Strecker, Manfred}, title = {River-discharge dynamics in the Southern Central Andes and the 1976-77 global climate shift}, series = {Geophysical research letters}, volume = {43}, journal = {Geophysical research letters}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2016GL070868}, pages = {11679 -- 11687}, year = {2016}, abstract = {Recent studies have shown that the 1976-77 global climate shift strongly affected the South American climate. In our study, we observed a link between this climate shift and river-discharge variability in the subtropical Southern Central Andes. We analyzed the daily river-discharge time series between 1940 and 1999 from small to medium mountain drainage basins (10(2)-10(4) km(2) ) across a steep climatic and topographic gradient. We document that the discharge frequency distribution changed significantly, with higher percentiles exhibiting more pronounced trends. A change point between 1971 and 1977 marked an intensification of the hydrological cycle, which resulted in increased river discharge. In the upper Rio Bermejo basin of the northernmost Argentine Andes, the mean annual discharge increased by 40\% over 7 years. Our findings are important for flood risk management in areas impacted by the 1976-77 climate shift; discharge frequency distribution analysis provides important insights into the variability of the hydrological cycle in the Andean realm.}, language = {en} } @article{OlenBookhagenStrecker2016, author = {Olen, Stephanie M. and Bookhagen, Bodo and Strecker, Manfred}, title = {Role of climate and vegetation density in modulating denudation rates in the Himalaya}, series = {Earth \& planetary science letters}, volume = {445}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2016.03.047}, pages = {57 -- 67}, year = {2016}, abstract = {Vegetation has long been hypothesized to influence the nature and rates of surface processes. We test the possible impact of vegetation and climate on denudation rates at orogen scale by taking advantage of a pronounced along-strike gradient in rainfall and vegetation density in the Himalaya. We combine 12 new Be-10 denudation rates from the Sutlej Valley and 123 published denudation rates from fluvially-dominated catchments in the Himalaya with remotely-sensed measures of vegetation density and rainfall metrics, and with tectonic and lithologic constraints. In addition, we perform topographic analyses to assess the contribution of vegetation and climate in modulating denudation rates along strike. We observe variations in denudation rates and the relationship between denudation and topography along strike that are most strongly controlled by local rainfall amount and vegetation density, and cannot be explained by along-strike differences in tectonics or lithology. A W-E along-strike decrease in denudation rate variability positively correlates with the seasonality of vegetation density (R = 0.95, p < 0.05), and negatively correlates with mean vegetation density (R = -0.84, p < 0.05). Vegetation density modulates the topographic response to changing denudation rates, such that the functional relationship between denudation rate and topographic steepness becomes increasingly linear as vegetation density increases. We suggest that while tectonic processes locally control the pattern of denudation rates across strike of the Himalaya (i.e., S-N), along strike of the orogen (i.e., E-W) climate exerts a measurable influence on how denudation rates scatter around long-term, tectonically-controlled erosion, and on the functional relationship between topography and denudation. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{BernhardtHebbelnRegenbergetal.2016, author = {Bernhardt, Anne and Hebbeln, Dierk and Regenberg, Marcus and Lueckge, Andreas and Strecker, Manfred}, title = {Shelfal sediment transport by an undercurrent forces turbidity-current activity during high sea level along the Chile continental margin}, series = {Geology}, volume = {44}, journal = {Geology}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {0091-7613}, doi = {10.1130/G37594.1}, pages = {295 -- 298}, year = {2016}, abstract = {Terrigenous sediment supply, marine transport, and depositional processes along tectonically active margins are key to decoding turbidite successions as potential archives of climatic and seismic forcings. Sequence stratigraphic models predict coarse-grained sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine siliciclastic deposition during transgressions and highstands has been attributed to sustained connectivity between terrigenous sources and marine sinks facilitated by narrow shelves. To decipher the controls on Holocene highstand turbidite deposition, we analyzed 12 sediment cores from spatially discrete, coeval turbidite systems along the Chile margin (29 degrees-40 degrees S) with changing climatic and geomorphic characteristics but uniform changes in sea level. Sediment cores from intraslope basins in north-central Chile (29 degrees-33 degrees S) offshore a narrow to absent shelf record a shut-off of turbidite deposition during the Holocene due to postglacial aridification. In contrast, core sites in south-central Chile (36 degrees-40 degrees S) offshore a wide shelf record frequent turbidite deposition during highstand conditions. Two core sites are linked to the Biobio river-canyon system and receive sediment directly from the river mouth. However, intraslope basins are not connected via canyons to fluvial systems but yield even higher turbidite frequencies. High sediment supply combined with a wide shelf and an undercurrent moving sediment toward the shelf edge appear to control Holocene turbidite sedimentation and distribution. Shelf undercurrents may play an important role in lateral sediment transport and supply to the deep sea and need to be accounted for in sediment-mass balances.}, language = {en} } @article{MortimerKirsteinStuartetal.2016, author = {Mortimer, Estelle and Kirstein, Linda A. and Stuart, Finlay M. and Strecker, Manfred}, title = {Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System}, series = {Earth \& planetary science letters}, volume = {455}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2016.08.040}, pages = {62 -- 72}, year = {2016}, abstract = {The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes. lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (U-Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{RadaeffCosentinoCipollarietal.2016, author = {Radaeff, Giuditta and Cosentino, Domenico and Cipollari, Paola and Schildgen, Taylor F. and Iadanza, Annalisa and Strecker, Manfred and Darbas, Guldemin and G{\"u}rb{\"u}z, Kemal}, title = {Stratigraphic architecture of the upper Messinian deposits of the Adana Basin (southern Turkey): implications for the Messinian Salinity Crisis and the Taurus petroleum system}, series = {Italian journal of geosciences : bollettino della Societ{\~A}  Geologica Italiana e del Servizio Geologico d'Italia}, volume = {135}, journal = {Italian journal of geosciences : bollettino della Societ{\~A}  Geologica Italiana e del Servizio Geologico d'Italia}, publisher = {Societ{\~A}  Geologica Italiana}, address = {Roma}, issn = {2038-1719}, doi = {10.3301/IJG.2015.18}, pages = {408 -- 424}, year = {2016}, abstract = {This paper is mainly based on field work carried out on the Messinian deposits of the Adana Basin ( southern Turkey), as well as on the interpretation of seismic reflection profiles to understand 3D geometries of the basin fill. Chronostratigraphic constraints for the Messinian deposits are from micropaleontological studies on foraminifera, ostracods, and calcareous nannofossils, recently carried out on the Messinian deposits of the Adana Basin. Our results indicate that this basin developed in a marginal area strictly related to the Mediterranean realm. The Messinian deposits of the Adana Basin record all the main steps of the Messinian Salinity Crisis ( MSC) that affected the Mediterranean area at the end of the Miocene. The new stratigraphic model for the Messinian deposits of the Adana Basin provided in this work gives new insights into both the MSC and the Taurus petroleum system. Despite their complete correspondence with the MSC, the Messinian deposits of the Adana Basin show some differences with respect to the current conceptual model for the MSC. For example, in the current conceptual model for the MSC, only one regional erosional surface ( MES) characterizes the MSC deposits. In the Adana Basin, two regional erosional surfaces, named MES1 and MES2, separate the Messinian deposits related to the MSC in Lower Evaporites, Resedimented Lower Evaporites ( RLE), and upper Messinian continental deposits containing a late Lago-Mare ostracod assemblage ( mainly fluvial coarse-grained and fine-grained sediments). In some places, Brecciated Limestones lie just above the MES1 and beneath the RLE. In addition, the RLE are thought to be related to the same step that brought to the Messinian halite deposition throughout the Mediterranean, pointing to a hyperhaline environment. In contrast, the fine-grained deposits of the RLE of the Adana Basin show the occurrence of Parathetyan brackish ostracod fauna ( early Lago-Mare ostracod assemblages), which defines an oligohaline depositional environment for the RLE. In terms of hydrocarbon prospecting, the Messinian evaporites of the Adana Basin have been considered as a perfect seal for the active Taurus petroleum system. Our results show that due to the complex stratigraphic architecture of the basin fill and the occurrence of two regional erosional surfaces ( MES1 and MES2), the Messinian evaporites are discontinuously present both in surface and in the subsurface of the Adana Basin. However, seal properties in the Adana Basin could be found in the Lower Pliocene deep marine clays of the Avadan Formation. This work leads to suggest a new stratigraphical model for the Messinian deposits of the Adana Basin, allowing us to amend the classical scheme with respect to the Messinian, and to officially define some new formations within the stratigraphy of the Adana Basin.}, language = {en} } @article{PingelMulchAlonsoetal.2016, author = {Pingel, Heiko and Mulch, Andreas and Alonso, Ricardo N. and Cottle, John and Hynek, Scott A. and Poletti, Jacob and Rohrmann, Alexander and Schmitt, Axel K. and Stockli, Daniel F. and Strecker, Manfred}, title = {Surface uplift and convective rainfall along the southern Central Andes (Angastaco Basin, NW Argentina)}, series = {Earth \& planetary science letters}, volume = {440}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2016.02.009}, pages = {33 -- 42}, year = {2016}, abstract = {Stable-isotopic and sedimentary records from the orogenic Puna Plateau of NW Argentina and adjacent intermontane basins to the east furnish a unique late Cenozoic record of range uplift and ensuing paleoenvironmental change in the south-central Andes. Today, focused precipitation in this region occurs along the eastern, windward flanks of the Eastern Cordillera and Sierras Pampeanas ranges, while the orogen interior constitutes high-elevation regions with increasingly arid conditions in a westward direction. As in many mountain belts, such hydrologic and topographic gradients are commonly mirrored by a systematic relationship between the oxygen and hydrogen stable isotope ratios of meteoric water and elevation. The glass fraction of isotopically datable volcanic ash intercalated in sedimentary sequences constitutes an environmental proxy that retains a signal of the hydrogen-isotopic composition of ancient precipitation. This isotopic composition thus helps to elucidate the combined climatic and tectonic processes associated with topographic growth, which ultimately controls the spatial patterns of precipitation in mountain belts. However, between 25.5 and 27 degrees S present-day river-based hydrogen isotope lapse rates are very low, possibly due to deep-convective seasonal storms that dominate runoff. If not accounted for, the effects of such conditions on moisture availability in the past may lead to misinterpretations of proxy-records of rainfall. Here, we present hydrogen-isotope data of volcanic glass (delta Dg), extracted from 34 volcanic ash layers in different sedimentary basins of the Eastern Cordillera and the Sierras Pampeanas. Combined with previously published delta Dg records and our refined U-Pb and (U-Th)/He zircon geochronology on 17 tuff samples, we demonstrate hydrogen-isotope variations associated with paleoenvironmental change in the Angastaco Basin, which evolved from a contiguous foreland to a fault-bounded intermontane basin during the late Mio-Pliocene. We unravel the environmental impact of Mio-Pliocene topographic growth and associated orographic effects on long-term hydrogen-isotope records of rainfall in the south-central Andes, and potentially identify temporal variations in regional isotopic lapse rates that may also apply to other regions with similar topographic boundary conditions. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{GeorgievaMelnickSchildgenetal.2016, author = {Georgieva, Viktoria and Melnick, Daniel and Schildgen, Taylor F. and Ehlers, Todd and Lagabrielle, Yves and Enkelmann, Eva and Strecker, Manfred}, title = {Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47 degrees S), Chile}, series = {Tectonics}, volume = {35}, journal = {Tectonics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1002/2016TC004120}, pages = {1317 -- 1341}, year = {2016}, abstract = {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.}, language = {en} } @article{JaraMunozMelnickStrecker2016, author = {Jara Mu{\~n}oz, Julius and Melnick, Daniel and Strecker, Manfred}, title = {TerraceM: A MATLAB (R) tool to analyze marine and lacustrine terraces using high-resolution topography}, series = {Geosphere}, volume = {12}, journal = {Geosphere}, publisher = {American Institute of Physics}, address = {Boulder}, issn = {1553-040X}, doi = {10.1130/GES01208.1}, pages = {176 -- 195}, year = {2016}, abstract = {High-resolution topographic data greatly facilitate the remote identification of geomorphic features, furnishing valuable information concerning surface processes and characterization of reference markers for quantifying tectonic deformation. Marine terraces have been used as long baseline geodetic markers of relative past sea-level positions, reflecting the interplay between vertical crustal movements and sea-level oscillations. Uplift rates may be determined from the terrace age and the elevation of its shoreline angle, a geomorphic feature that can be correlated with past sea-levels positions. A precise definition of the shoreline angle in time and space is essential to obtain reliable uplift rates with coherent spatial correlation. To improve our ability to rapidly assess and map shoreline angles at regional and local scales, we have developed TerraceM, a MATLAB (R) graphical user interface that allows the shoreline angle and its associated error to be estimated using high-resolution topography. TerraceM uses topographic swath profiles oriented orthogonally to the terrace riser. Four functions are included to analyze the swath profiles and extract the shoreline angle, from both staircase sequences of multiple terraces and rough coasts characterized by eroded remnants of emerged terrace surfaces. The former are measured by outlining the paleocliffs and paieo-platforms and finding their intersection by extrapolating linear regressions, whereas the latter are assessed by automatically detecting peaks of sea-stack tops and back-projecting them to the modern sea cliff. In the absence of rigorous absolute age determinations of marine terraces, their geomorphic age may be estimated using previously published diffusion models. Postprocessing functions are included to obtain first-order statistics of shoreline-angle elevations and their spatial distribution. TerraceM has the ability to process series of profiles from several sites in an efficient and structured workflow. Results may be exported in Google Earth and ESRI shapefile formats. The precision and accuracy of the method have been estimated from a case study at Santa Cruz, California, by comparing TerraceM results with published field measurements. The repeatability was evaluated using multiple measurements made by inexperienced users. TerraceM will improve the efficiency and precision of estimating shoreline-angle elevations in wave-cut terraces in both marine and lacustrine environments.}, language = {en} }