Pre-Andean deformation of the Precordillera southern sector, Southern Central Andes.

GIAMBIAGI, L., MESCUA, J., BECHIS, F., MARTÍNEZ, A. Y FOLGUERA, A.

GEOSPHERE

GEOLOGICAL SOC AMER, INC

Lugar: Tucson; Año: 2011 vol. 7 p. 1 - 21

1553-040X

This paper presents a detailed investigation of the structure and evolution of the Precordillera southern sector. We document the development and successive reactivation of regional and discrete structural grain through time, and discuss the existence of a large-scale mechanical anisotropy present in the lithosphere. Our kinematic studies indicate that the Permian orogeny generated a double-vergent fold-and-thrust belt of transpressive deformation, where strain was partitioned into two different types of deformation domain. The west-vergent western domain was characterised by partitioned transpression with shortening dominated and a strike-slip dominated subdomains. The east-vergent eastern domain was characterised by pure contractional deformation. Our model for the Late Permian to Early Triassic evolution of the Precordillera involves a NNW-trending weakness zone affected by a NNE-directed extension, generating an area with transtensional deformation during the Choiyoi volcanism development. Afterwards, during the Triassic generation of the Cuyana rift basin, the NE stretching direction was orthogonal to the rift trend, indicating a pure extensional deformation. We propose a model where the clear parallelism between the distributions of an inferred Lower Paleozoic suture zone, a NNW-trending Late Paleozoic belt, and Permo-Triassic rift-related magmatism, indicates the reactivation of a NNW-trending long-lived lithospheric weakness zone.