Neogene structure of the Andean Precordillera, Argentina: insights from analogue models

Abstract

Analogue models combining different sets of preexisting structural weaknesses were developed to understand their evolution during regional ~ENE shortening. Strain analysis of simulations was performed with the GEODEF 1.1 software, a tool that allows to quantify deformation in plan view on the basis of displacement fields. Results showed up that regional NNE heterogeneities are reactivated as dextral reverse-slip structures, though NNE neoformed thrusts are also present. Likewise, dominant sinistral strike-slip motions have been obtained for reactivated second-order WNW structures whereas sinistral reverse-slip has been recorded for NW ones. Comparison of these results with structural, kinematic and paleomagnetic data supports partitioned dextral transpression for the northern Andean Precordillera since the Miocene. Moreover, models not only confirm sinistral strike-slip motions for WNW structures of the Precordillera but also suggest that they would represent preexisting crustal fabrics that were reactivated during the Andean orogeny. These cross-strike structures have played a significant role in the construction and evolution of the fold and thrust belt as they segmentate the activity of orogen-parallel structures.