Structure of the southern end of the Subandean System (Salta, Santiago del Estero and Tucumán provinces).

Abstract

The southernmost segment of the Santa Barbara System extending along 100 km in the Andean foreland, represents an east-verging anticlinorium, where each sierra coincides with an axial culmination of this major fold. The map view curves exhibited by the structure are related to NE striking dextral strike- slip faults, which coincide with reactivated normal faults. One of them, located at the south end of Cerro Colorado, marks the southern boundary of the Cretaceous rift. Therefore this belt shows two segments: the northern one with thick Cretaceous sequences and the southern one, where there are no Cretaceous beds and the Tertiary sequence is lying directly on Palaeozoic rocks. The evolution of this part of Santa Bárbara System started in Middle Eocene in coincidence with a horst, which was already uplifted at this time. The Cretaceous synrift sedimentation was controlled by the NE striking faults and a NW-SE extension which was more significant that the EW extension recognized in other parts of the basin. The Andean shortening in the last 5 Ma, induced in the NE striking faults with rightlateral displacements generated complex structures.