Geological And Geophysical Evidences Of The Polyphase Structural Evolution Of The Southern Precordillera (31º42´S-69º24´W) In The Central-Western Argentina

ARIZA, JUAN PABLO; NACIF, SILVINA; LUDUEÑA, MARCOS; MARTINEZ, M PATRICIA; BOEDO FLORENCIA L; CEBALLOS, JUAN PABLO; VUJOVICH, GRACIELA; SANCHEZ, M.A; CONTRERAS, J.; PEREZ, SOFIA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 p. 1 - 13

0895-9811

The evolution ofthe western margin of South America comprised different tectonic regimesresponsible of the present geological composition and structure of the CentralAndes. Remote sensing, geological and geophysical data (aeromagnetic andseismological data) have been processed to understand the polyphase structuralevolution of the Argentine Southern Precordillera. The outcrops exposed in theSierra de Barreal (31 42 S-69 24 W) show evidences of a complex structuralevolution related to the superposition of three orogenies from the EarlyPaleozoic to nowadays. The Chanic orogeny (Late Devonian) is characterized by two systems ofnon-coaxial ductile folds that affect Early Paleozoic rocks of the Cienaga del MedioGroup. The recognized rotation in the shortening direction (from NW-SE toENE-WSW) is interpreted here as a result of a sinistral transpressive regime.The San Rafael orogeny (Early Permian) is represented by back-thrusts and blindfaults associated to asymmetric folding that involves the deformation of UpperCarboniferous rocks (Majaditas Formation). Finally, the compressive Andeanorogeny associated to the Pampean flat-slab subduction segment has been locally controlledby inherited pre- Andean anisotropies. This is evidenced by: 1-the structuralstyle of western-southern Argentine Precordillera, which in the study area isrepresented by faulted blocks and top-to-west vergent back-thrusts; 2- NW-SE deflections and associated magneticanomalies in the Argentine Precordillera fold-and-thrust belt; 3-neotectonicstructures developed in a sinistral transpressive system; 4-the crustalseismicity associated to NW-SE trending structures with left-lateral componentmotion.