Geological and geophysical evidences of the polyphase structural evolution of the Southern Precordillera (31
420S-69
240W), central western Argentina

ARIZA, J.P.; SÁNCHEZ, M.; BOEDO, F.L.; NACIF, S.; CONTRERA, J. ; CEBALLOS, J. ; LUDUEÑA, M.; PÉREZ LUJÁN, S.B.; VUJOVICH, G.I; MARTINEZ, P.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2018 vol. 87 p. 53 - 65

0895-9811

The evolution of the western margin of South America comprised different tectonic regimes responsibleof the present geological composition and structure of the Central Andes. Remote sensing, geological andgeophysical data (aeromagnetic and seismological data) have been processed to understand the polyphasestructural evolution of the Argentine Southern Precordillera. The outcrops exposed in the Sierra deBarreal (31420S-69240W) show evidences of a complex structural evolution related to the superpositionof three orogenies from the Early Paleozoic to nowadays. The Chanic orogeny (Late Devonian) is characterizedby two systems of non-coaxial ductile folds that affect Early Paleozoic rocks of the Cienaga delMedio Group. The recognized rotation in the shortening direction (from NW-SE to ENE-WSW) is interpretedhere as a result of a sinistral transpressive regime. The San Rafael orogeny (Early Permian) isrepresented by back-thrusts and blind faults associated to asymmetric folding that involves the deformationof Upper Carboniferous rocks (Majaditas Formation). Finally, the compressive Andean orogenyassociated to the Pampean flat-slab subduction segment has been locally controlled by inherited pre-Andean anisotropies. This is evidenced by: 1-the structural style of western-southern Argentine Precordillera,which in the study area is represented by faulted blocks and top-to-west vergent back-thrusts;2- NW-SE deflections and associated magnetic anomalies in the Argentine Precordillera fold-and-thrustbelt; 3-neotectonic structures developed in a sinistral transpressive system; 4-the crustal seismicityassociated to NW-SE trending structures with left-lateral component motion.