Compressional- and transpressional-stress pattern for Pliocene and Quaternary brittle deformation in fore arc and intra-arc zones (Andes of Central and Southern Chile)

Kinematic analysis of fault slip data for stress determination was carried out on Late Miocene to Quaternary rocks from the fore are and intra-are reg ions of the Chilean Andes, between 33 degrees and 46 degrees south latitude s. Studies of Neogene and Quaternary infilling (the Central Depression), as well as plutonic rocks of the North Patagonian Batholith along the Liquine -Ofqui Fault Zone, have revealed various compressional and/or transpression al states of stress. In the Pliocene, the maximum compressional stress (sig ma(1)) was generally oriented east-west. During the Quaternary, the deforma tion was partitioned into two coeval distinctive states of stress. In the f ore are zone, the slate of stress was compressional. with sigma(1) oriented in a N-S to NNE-SSW direction. In the intra-are zone the state of stress w as transpressional with sigma(1) striking NE-SW. Along the coast, in one si te (37 degrees 30'S) the Quaternary strain deformation is extensional, with an E-W direction, which can be explained by a co-seismic crustal bending r eadjustment. (C) 1999 Published by Elsevier Science Ltd. All rights reserve d.