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Coupling between climate, erosional processes, and orogenesis



This project, in collaboration with Manfred Strecker at the Institut für Geowissenschaften, Universität Potsdam, seeks to establish the potential role of climatically-moderated erosional processes in the development of the central Andean orogen. We have conducted field studies in central Argentina that document the relationship between uplift of the margin of the Puna Plateau and the establishment of internal drainage and fluvial network reintegration. Using processed-based models of fluvial incision and channel aggradation, we quantitatively test models of the establishment of internal drainage, and note that this may represent an important threshold that decouples erosional mass evacuation from tectonic processes under some geologic circumstances. Secondly, we developed models linking erosional processes to tectonic deformation in externally drained fold-and-thrust belts, and tested these models in the Aconcagua fold-and-thrust belt, central Argentina. Thirdly, we explored the possible linkages between erosion and deformation in basement-cored uplift provinces, such as the Sierras Pampeanas in central Argentina, and present a quantitative model for exploring these links. Finally, we are in the process of synthesizing our field and modeling work in the area to develop a consistent explanation of the topography, erosion, and tectonics of the central Andes.

Currently, we are creating analog and numerical models of the central Argentine Precordillera, where erosion of this fold-and-thrust belt may leave an important imprint on the deformation observed there. This project, in collaboration with Andy Take at Queen’s University in Canada, uses state-of-the-art analogue modeling techniques and finite element models under comparable boundary conditions to quantify the variability of wedge kinematics and understand its causes. In the physical models, our contractional experimental apparatus (sandbox) includes a load frame with a servo feedback system that allows for a variety of boundary conditions to be applied to the moving wall, including constant displacement rate, time-varying displacement rate, constant loading, and time-varying loading. This particular experimental design allows us to investigate feedbacks between shortening rates and surfaces processes (erosion) that have not been studied before in analogue modeling. We apply Particle Image Velocimetry (PIV) techniques to digital images from the experimental model to derive high-resolution kinematics and calculate strain, uplift and exhumation rates. We use granular materials with different frictional properties including cohesion, friction coefficient and density, which can be simulated in the numerical box. These materials include silica sand, glass beads and walnut shells, with various grain sizes. In the numerical models, we use the finite element code GALE that allows, among other things, the simulation of an experimental box under contraction, in 2D and 3D, and permits the modification of boundary conditions, mass fluxes, rheologies, and crustal shapes. Preliminary results indicate that high-resolution kinematics derived from PIV technique can be compared directly to 2D/3D numerical simulations. The photos show the principles of PIV and the kinematics of a deformed walnut-shell experimental wedge. These models will be crafted with the specific geologic initial and boundary conditions appropriate for the Argentine Precordillera. By varying factors such as erosion, plate boundary forces, and rheology in both types of models, we will investigate how erosion may have shaped this fold-and-thrust belt, and gauge how well analog models may reproduce geologically reasonable deformation conditions.