The Co-evolution of Thin- and Thick-skinned Deformation Associated with Flat Subduction, Western Argentina

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Researchers at Cornell University and their Argentine colleagues are studying the relationship between thin- and thick-skinned deformation due to flat slab subduction of oceanic crust beneath the Precordillera-Sierras Pampeanas region of western Argentina. The goal of this study is to produce a suite of maps that showing comprehensive velocity fields at 5 million year intervals from 20 million years ago to the present. These maps record the kinematic changes from thin-skinned thrusting and active magmatism to the cessation of arc magmatism and beginning of foreland block uplifts (thick-skinned thrusting) coeval with thin-skinned thrusting. The work involves a combination of fieldwork to measure fault slip in growth strata, construction of balanced cross sections, and kinematic modeling of the velocity field for each time increment. The research is providing insight into the mechanisms and driving forces of foreland deformation during flat slab subduction. Additionally, the research is accumulating critical data on the relationship of instantaneous deformation rates determined by geodetic methods (Global Positioning System) and geological deformation rates measured over millions of years. The data will also be useful to those evaluating seismic hazard in the region.