Assessing late quaternary shortening related to footwall splays at the southern section of Las Peñas thrust system , Southern Precordillera, Argentina

Abstract

At the southern Pampean flat-slab of the Central Andes, theactive deformation zone is located at the easternmost thrusts ofthe Southern Precordillera along the Las Higueras-Las Peñas range(32° 10’-32° 45’ S). This range is bounded by the Las Peñas ThrustSystem (LPTS), which juxtaposes Cenozoic sedimentary rocks overa suite of Quaternary alluvial deposits showcasing variable shorteningrates. This study is focused on the southern part of this range -LaEscondida Creek-, where the Quaternary thrust front migrationaffects Neogene and Pleistocene strata. We estimated shorteningvalues by retrodeforming trishear models constructed from alluvialsurfaces, which served as geometric markers of deformationfor propagating structures in the piedmont. Dip-slip rates wereestimated ranging from 0.90mm/yr and 1.79mm/yr for the last∼12 and 3 ka, respectively.