Thick-skinned tectonic style resulting from inversion of previous structures in the Southern Cordillera Oriental (NW Argentine Andes)

Abstract

Structures mapped in the southern Cordillera Oriental of the Andes show an unexpected geometry in an east-west cross-sectional view, with a remarkable predominance of west-directed thrusts. Although some of the Andean structures trend north-south perpendicular to the main east-west direction of Andean shortening, many of them clearly differ from this expected orientation. This peculiar structural style has been largely related to the inversion of the Cretaceous Salta Rift Basin; however, some of these anomalously trending Andean folds and faults do not result from the inversion of Cretaceous faults. This lack of inversion of some Cretaceous structures becomes evident where west-dipping extensional faults rest in the footwall of west-directed thrusts instead of developing east-directed thrusts, as would be expected. Detailed study of several structures and examination of the geometry and facies distribution of several basins highlight not only the role played by the inversion of Cretaceous extensional faults on the geometry of the Andean structures, but also that played by basement anisotropies on the development of both the Cretaceous extensional faults and the Andean contractional structures.