Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.   All Rights Reserved.

The foothills of the central Andes of northwestern Argentina hinder the interpretation of the complex structural rift system developed during late Mesozoic extension. Andean compressive deformation inverted the Salta rift system, resulting in a series of complex structures with trends oblique to the main Andes. The Lomas de Olmedo basin, a failed branch of the rift system located east of the Andean orogenic front, was selected to undertake deep reprocessing of the available industrial seismic lines. A 150-km-long seismic section of the basin, recorded with Vibroseis and dynamite sources, was reprocessed. Extended correlation applied to the Vibroseis seismic data yielded reliable results down to 9 sec two-way travel time. Acoustic horizons identified within this interval include the deepest synrift deposits in the axial part of the basin and a deep oblique discontinuity in the crust. On this basis, a complete cross section of the basin was made. This study documents the asymmetry of the rift, with a prominent zone of thermal uplift in the northern edge. Truncation of the Paleozoic beds and identification of a deep oblique discontinuity at 7-8 sec (18-21 km deep) suggest that a northward-dipping detachment controlled the asymmetry of the system. The rift structure is mildly modified by folding related to Cenozoic tectonic inversion in the southern sector of the basin. This inversion was controlled mainly by strike-slip displacements along the previous normal faults.