Evolución y construcción neógena de los Andes Centrales del Sur (34º-36º)

Abstract

In this contribution we present an update no the Neogene evolution of the Southern Central Andes based on field data and new geochronological ages of the sinorogenic deposits cropping out in Chile and Argentina. Between 20 and 16 Ma the deformation was located along the western and central belt of the Principal Cordillera. After that the deformation migrated to east developing the Malargüe fold and thrust belt during the 16 and 5 Ma. Out-sequence thrusting occured along the axial zone of the cordillera from 5 Ma. The evolution of the western-central and eastern slope of the principal Cordillera was diachronous indicating a west-east direction for the tectonic transport coherent with the east vergent crustal models proposed for this segment of the Andes. Moreover, the Neogene evolution of the Cordillera Principal could be explained by a critical Coulomb wedge model. In this sense, the deformation of the western and central slope of the cordillera would respond to a subcritical stage of the wedge. During the development of the Malargüe fold and thrust belt the taper achieved the taper and the wedge was blunt enough and strong enough to overcome the resistance to slip on the decollement. The geometry and deformation kinematic of this andean segment are consistent with a double-vergent wedge model where the deformation would be controlled by the subduction of the South America plate beneath the Andes producing tectonic shortening and crustal deformation.