Sinestral Rotation and NNW Shortening of the Ambato Block induced by Cenozoic NE to E-W Transpression, Argentina

Abstract

South of 27° S, where the Nazca plate sinks with low angle below the South American plate, the mountain ranges that constitute the Sierras Pampeanas where uplifted by reverse faults, tilted to the east, during the Pliocene. The analysis and interpretation of satellite images and the systematic recording of fracture planes in outcrops of metamorphic basement rocks and Neogene sediments allow us to determine tectonic events that gave the region of the Ambato Block a NE shortening, a sinestral rotation and NNW shortening. As a result of these tectonic events, during the convergence of the Nazca and South American plates, reverse faults, gravitational faults and transcurrent faults were generated, and the division of the Ambato Block into smaller ranges and the development of intramontane basins ocurred. The Las Cañas normal fault, with E-W strike, was generated before the Andean tectonics, using the schistosity planes of the metamorphic basement; it constitutes a step in which the outcrops of the Santa Bárbara Subgroup of the Salta Group end.