Collaborative Research: Towards a Quaternary Spatial and Temporal Deformation History at the Central Andean Thrust Front

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This multidisciplinary research aims to measure deformation rates at the central Andean thrust front in Argentina in order to (1) better understand the kinematics and geometry of deformation at the intersection of the thin skinned Precordilleran and thick-skinned Pampean structural zones; and (2) assess the risk posed by blind-thrusts in this region for population centers such as the nearby cities of Mendoza and San Juan. By combining geologic data (seismic lines, dated stratigraphy, structural cross-sections) with geomorphic data (deformed and dated terraces and wind gaps, drainage patterns), the U.S. research team in collaboration with Argentine researchers will translate slip rates on thrust faults, uplift rates in the hanging wall of thrusts and blind-thrust anticlines, and rotation rates on the limbs of hanging wall anticlines on individual structures into an integrated spatial and temporal deformation history. Five structures - the Barrancas anticline, El Borbollon anticline, Las Penas thrust fault, Montecito anticline and Cerro Salinas thrust - are targeted for seismic interpretation, geomorphic mapping, cosmogenic dating, and drainage analysis. This study will address both tectonics and seismic hazards. The study region lies at the intersection between the thin-skinned, east-vergent Precordillera and the west-vergent, thick-skinned Sierras Pampeanas tectonic domains. The conditions that have led to the transferal of shortening far into the interior of the Andean plate and that simultaneously drive both thick- and thin-skinned deformation are poorly understood. A temporally and spatially constrained deformation history is of critical importance for answering questions such as: which structures are slipping fastest; is the deformation history uniform, or are rates temporally variable; if rates are variable, what is the relationship between adjacent structures, or between structures belonging to different structural provinces? The project will document three blind thrust structures in the Andean foreland. Blind-thrust faults pose a significant risk to the Mendoza-San Juan corridor as well as other parts of the world. This type of fault is of particular interest in seismic hazard analysis because the sometimes subtle geomorphic expression makes them difficult to identify, especially in areas that have been altered by urbanization. This region presents an opportunity to investigate changes in geomorphology associated with blind-thrusts in different stages of development, as well as regional changes in the drainage network which might indicate previously undetected deformation.