Permo-Triassic oblique extension in the Potrerillos-Uspallata area, western Argentina

The Permo-Triassic evolution of southwestern South America was characterized by the development of a great amount of volcanism under extensional conditions. Structural analyses of faults developed contemporaneously with this volcanism in the key area of Potrerillos-Uspallata suggest the existence of an oblique extensional setting controlled by the presence of a pre-existing lithospheric anisotropy. A clear parallelism between the trace of an inferred Devonian suture zone, the Late Paleozoic San Rafael orogenic belt and the Permo-Triassic rifting suggests that Early and Late Paleozoic tectonic inheritance permitted the reactivation of a NNW-trending zone of lithospheric weakness. The reactivation of this pre-existing weak zone during Late Permian to Early Triassic times has resulted in the generation of a new complex fault system, which concentrated the oblique-slip normal displacement related to a NNE–SSW stretching (N23°E).