The subsurface of Campo de Talampaya: Stratigra phy and Tectonic Evolu- tion. Ischigualasto ? Ischichuca Basin, La Rioja. A rgentina?. T

Acta geológica lilloana 21 (2): 2009

Abstract

The subsurface stratigraphy and tectonism of the southern part of Ischigualasto - Ischichuca Basin was performed using six seismic lines from Campo de Talampaya, La Rioja Province (Argentina). Four Supersequences or 2nd Order Sedimentary Cycles were defined and the location of the main depocenters for the Upper Paleozoic to Neogene strata were stablished. The thickness of the Supersequences varies from 2.000 m for the Carboniferous - Permian, 3.500m for the Upper Permian - Upper Triassic, 50-400 m for the Cretaceous, and up to 6.000 m for the Tertiary rocks. The main depocenters changed through geological time. The Upper Paleozoic depocenter was located near Esquina Colorada (west side of Campo de Talampaya); the Triassic depocenters were located in the northwest and southeast corners and, finally, the Tertiary depocenter was located near Pagancillo, in the northern side of Campo de Talampaya. The sedimentary sequences are related to four tecto nic episodes from the Upper Carboniferous to the Pliocene ? Pleistocene (?). The first tectonic episode is an extensional phase or rifting; the second episode is a compressive phase, which caused folding and faulting; the third episode is related to a new extensional phase (and volcanism); the last tectonic episode changed the fault movement and formed a set of reverse faults. The possible areas for hydrocarbon exploration are related with Supersequence II (Triassic of the Agua de la Peña Group) at the northwestern corner of Campo de Talampaya and the eastern side of Cerro Rajado, where the stratigraph y and anticline structures present a promising development.