East-vergent thrusts and inversion structures: An updated tectonic model to understand the Domeyko Cordillera and the Salar de Atacama Basin transition in the western Central Andes

Abstract

The tectonic evolution of the Andean forearc in northern Chile has commonly been related to superimposed deformational events associated with different tectonic settings. The eastern Domeyko Cordillera and the Salar de Atacama Basin on the inner Andean forearc, have been widely investigated, and several alternative tectonic models including extensional and/or contractional deformation are proposed to explain its evolution. Nevertheless, when trying to determine the role of Paleozoic and Mesozoic inherited-basement extensional structures during the Andean orogeny an evolutionary model is still not clear. Therefore, the aim of this research is to improve the understanding of these aspects. Based on the interpretation of a regional 2-D seismic grid and new structural data from outcrops, we propose that the main mechanisms of contractional deformation and uplift are related to: (1) the propagation of east-vergent basement-involved thrust faults, (2) the tectonic inversion of pre-existing normal faults and (3) the activation of shallow thin-skinned thrusts. Additionally, the resultant geometry of the structural styles is frequently controlled by three factors: (i) the initial geometry of inherited major faults, (ii) the rheology of the deformed rocks, and (iii) the rate of accumulation of the Upper Cretaceous-Cenozoic syn-tectonic deposits. Finally, we interpreted that the tectonic transition between the Domeyko Cordillera and the Salar de Atacama Basin is marked by the interaction between east-vergent thick-skinned thrusts and west-vergent inverted normal faults.