LAUSR

Abstract We have combined 2D seismic information with field data to interpret the structure underneath the Salar de Punta Negra Basin. The interpretation of NW-SE oriented seismic profiles along the basin shows that its structure consists of a doubly-verging contractional system composed of inverted and basement-involved structures. West-verging inversion anticlines and high-angle reactivated normal faults are preferentially located at the central and eastern parts of the basin. These commonly involve Upper Paleozoic to Mio-Pliocene volcanic and sedimentary stratigraphic wedges, indicating that these resulted from the tectonic inversion of ancient basement structures that acted as normal faults during extensional episodes in the Paleozoic and Mesozoic. East-verging, basement-cored anticlines and reverse faults are located at the western part of the basin and they are generally related to blind ramps, which form part of the eastern termination of the Domeyko Cordillera. The presence of unconformable Tertiary (Eocene, Oligocene and Mio-Pliocene) synorogenic deposits over the contractional structures (basement cored and inversion anticlines) suggest that these could have been developed progressively during this period. Finally, we show here as the shortening of ancient extensional system played a fundamental role in the Andean deformation of the Preandean Depression of northern Chile.