Compressional Pilocene and compressional-transpressional Pliocene states of stress, southern Chilean Andes (38-42º30'S).

Abstract

Miocene-Pliocene and Quaternary intrusive rocks and sedimentary deposits from the Central Depression and the Main Cordillera, between 38 and 42º30'S, have been affected by local and regional brittle deformation. Microfault geometry and kinematic analysis along with calculation of deviatoric tensors allowed to determine regional-seale states of stress. Two tectonic events were identified. A Pliocene event, prior to the Quaternary, affects the entire zone of study, and is characterized by a maximum compressional stress s₁ roughly oriented in an E-W direction. A Pleistocene event corresponds to an overall deformation partitioned into two coeval distinctive states of stress: a compressional stress s₁ oriented in a N-S to NNE-SSW direction in the fore arc zone, and a dextral transpressional state of stress with s₁ striking NE-SW, in the intra-arc zone.