Next to Tibet, the Andean Altiplano/Puna Plateau is the second largest plateau province on Earth. Processes linked with the development of the plateau have had a sustained influence on the tectonic evolution of the plateau margins and adjacent regions in the broken foreland of the Andes and the Subandean foreland fold-and-thrust belt. In our studies we (1) analyze the role of long-term climatic change on plateau formation in the southern central Andes of Bolivia and Argentina; (2) determine the onset of humid vs. arid climate conditions along the eastern flanks of the Andean plateau margin; (3) assess the role of tectonic versus climatic forcing in the filling and evacuation of intermontane sedimentary basin fills; and (4) strive to determine paleo-elevations using O isotopes measured on paleosols and volcanic glass in Tertiary volcanic ash layers.
One of the most conspicuous effects of recent climate change is the widespread melting and retreat of glaciers. Changes in glacial and snow-covered areas affects the generation of meltwaters and mountainous runoff. This has consequences for densely populated areas of south and central Asia, where snow and glacial meltwaters are an important source for drinking water, irrigation, and hydropower. However, any type of ground-based data (e.g., glaciological, hydrological, meteorological) from these regions is scarce, which makes quantitative assessments of recent trends and predictions of future evolutions notoriously difficult. In an effort to bridge these data gaps and to investigate glacial and hydrological systems in this region, our research group is using a combination of field work, analysis of remote-sensing data, and modeling. This includes (1) regional, large-scale monitoring of recent glacier dynamics, as well as more detailed studies on specific glaciers, (2) ground-based studies in the western Himalaya, which focus on erosion and sediment transport on various time scales, and (3) hydrological modeling based on calibrated satellite data. Ongoing projects are embedded in the PROGRESS research cluster, the DFG Graduateschool GK1364, and closely connected with research foci at Deutsches GeoForschungsZentrum.
While important advances have been made in understanding the evoultion of the Tibetan and Andean plateau regions, large gaps exist regarding the Anatolian plateau. The neotectonic evolution of this region, its impact on atmospheric circulation patterns, and its relationship with coeval tectonic and magmatic processes, are still not adequately understood. In this project we seek to unravel the evolution of the plateau and assess its influence regarding climate and climate-driven surface processes through detailed low-temperature thermochronologic and geomorphic studies. In particular, we are analyzing the exhumation history of the plateau flanks using (U-Th)/He thermochronolgy, geomorphic and structural mapping as well as cosmogenic nuclide dating of incised pediment and fluvial terrace systems. In addition it is our goal to better understand the evolution of normal faulting in the plateau interior using field observation, radiometric dating, and DGPS surveys.
Forearc regions are among the most tectonically active settings worldwide, often subject to pronounced tectonic uplift and subsidence. Surface uplift, subsidence history, and the composite landscapes that evolve in such regions may thus provide important insight into the factors that govern the geodynamic and structural evolution of these dynamic environments. The forearc of South-Central Chile is characterized by different seismotectonic and geomorphic segments, documenting a distinct spatiotemporal tectonic evolution that may encapsulate important information concerning crustal behavior during the seismic cycle. In this study our goals are focused on (1) defining the long-term style and chronology of tectonic processes in the forearc region; (2) estimating deformation rates over the seismic cycle and the Quaternary Period in the southern sector of the Valdivia 1960 earthquake segment; (3) obtaining a paleoseismic record of subduction earthquakes in this region; and (4) integrating deformation rates and paleoseismic records to obtain a strain partitioning budget and explore its influence on modulating earthquake recurrence and magnitude.
Specific organic compounds in sediments are sometimes termed "molecular fossils" or biomarkers, because their presence can be used to infer the relative contributions of, for instance, algae, bacteria or land plants into the sedimentary record (1, 2). Through advances in analytical methods, it has become possible to measure the stable isotopic composition (the ratio of carbon 13 and carbon 12, d13C; and the ratio of deuterium and protium, dD or D/H) of these biomarkers from which additional source and climatic information about the time of deposition can be derived. Especially the D/H composition of lipids has developed into a promising new proxy for paleohydrology, as every photosynthetic organism uses (environmental) water as their hydrogen source. In this study we strive to identify the environmental and physiological forcing parameters determining the D/H composition of higher plant lipids, to be able to use their D/H ratio as a paleo-evaporation proxy. Furthermore, we are applying lipid D/H measurements to reconstruct changes in the hydrology in the catchments of European lakes throughout the Holocene, to determine the response of the hydrological cylcle to climatic changes.
Sedimentary organic matter constitutes the largest reactive carbon pool on Earth. During burial it becomes increasingly recalcitrant, thereby reducing its bio-availability and limiting metabolic activity in the deep biosphere. However, at greater depths dissolved gases of either biogenic or thermogenic origin play important roles as energy and food sources for microbial communities. Subsurface environments are characterized by high pressure, which allows for much higher solubility of gases compared to the surface. Theses gases usually are lost upon sample retrieval. The Geomicrobiology group focuses on the development of incubation devices which allow for the recreation of true in-situ conditions, including gas saturation as well as novel detection and quantification techniques. These efforts will help elucidate the reaction of microbial communities to varying gas concentrations and compositions. To date, such studies have been typically carried out in natural marine systems. Being part of the GeoEnergy Project funded by the German Federal Ministry of Science and Technology, we aree also focusing on the influence of anthropogenic storage of CO2 in subsurface reservoirs.
The process of fault propagation and the possible interaction between faults through stress triggering in continental settings remains a major challenge for geoscientists. A better knowledge of this issue is not only important in order to characterize fault behavior on long timescales, but it is crucial on different timescales that span the Quaternary and may ultimately mitigate seismic and related natural hazards. The Alborz Mountains in the Tehran region of north-central Iran offer an excellent opportunity to study the geometric and kinematic evolution of fault segments and fault interaction. Here, we find evidence for thrusts, strike-slip faults, and obliquely slipping thrust faults that have been active at varying timescales, indicating a transpressional environment characterized by dip-slip thrusting and left-lateral strike slip faulting. The two major fault systems bounding the Alborz Mountains to the south are the North Tehran Thrust (NTT) and the Mosha Fasham Fault (MFF). Despite numerous Quaternary fault-offsets and destructive historical earthquake records it is not known, however, how these faults are linked and how they interact. We are studying the Quaternary history of these faults and characterize their kinematic evolution and their possible interaction through time trough detailed structural mapping, fault-kinematic analysis, and cosmogenic nuclide dating. On geologic time scales, spanning the Cenozoic evolution of this region, we are analyzing the exhumation history using (U-Th)/He thermochronology, perform sandstone petrology and conglomerate provenance analysis, and magnetostratigraphy to develop spatiotemporal scenarios of the tectono-sedimentary evolution of this region in light of the dynamics of the Arabia-Eurasia collision.
The topography reflects tectonism at variuos length and time scales and the overprint of multiple climate-driven processes and related effects in changes of erosional efficiency. On long time scales, focused precipitation and mass removal may even introduce changes to the tectonic stresses in the orogen and affect the locus of tectonic activity. While many of these issues are beginning to be understood now, numerous open questions remain. For example, it is still not very well known what the necessary time scales are to generate topographic changes that develop into efficient orographic barriers. Importantly, it has not been been very well established, which kind of processes of erosion are most efficient, and which climatic and erosional thresholds exist to significantly alter a tectonically active system. Furthermore, it is poorly known, which role transient sediment storage in intermontane basins plays in triggering or abandoning fault activity, how such sediment fills are stored in such basins, and how they influence foreland sedimentation, once connectivity with the foreland has been re-established. Feedbacks between these processes apparently exist, but the time scales at which changes may be efficiently introduced into the system are vaguely known. Therefore, the recognition of positive feedback mechanisms between the effects of sustained precipitation patterns, vegetative cover, weathering, and tectonic activity in a mountain belt are first-order research topics that merit further consideration. In our projects in the Himalaya, Tien Shan, and Pamir we address these issues and strive to unravel the complex relationships between various surface processes and tectonic evolution.
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 glacial-cycle 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 ~5,000 km of the western coast of South America between 1° N and 40° 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/ka averaged over the past ~125 ka. The patterns of terrace elevation and uplift rate display high-amplitude (~100–200 m) and long-wavelength (~102 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, Valparaíso, 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 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 http://doi.org/10.5281/zenodo.4309748 (Freisleben et al., 2020).