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

Abstract

This paper presents a detailed investigation of the structure and evolution of the Precordillera southern sector (Argentina). 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 doubly vergent foldand-thrust belt of transpressive deformation, where strain was partitioned into two different types of deformation domains. The westvergent western domain was characterized by partitioned transpression with shortening dominating, and a strike-slip-dominated subdomain. The east-vergent eastern domain was characterized by pure contractional deformation. Our model for the Late Permian to Early Triassic evolution of the Pre cordillera involves a north-northwest-trending weakness zone affected by north-northeast- directed extension, generating an area with transtensional deformation during the Choiyoi volcanism development. Later, during the Triassic generation of the Cuyana rift basin, the northeast stretching direction was orthogonal to the rift trend, indicating pure extensional deformation. We propose a model where the clear parallelism between the distribution of an inferred early Paleozoic suture zone, a northnorthwest- trending late Paleozoic belt, and Permian-Triassic rift-related magmatism indicates the reactivation of a northnorthwest- trending long-lived lithospheric weakness zone. © 2011 Geological Society of America.