Synrift geometry of the Neuquén Basin in northeastern Neuquén Province, Argentina

Abstract

A map of the principal grabens and half-grabens of the Neuquén Basin in the northeastern part of Neuquén Province, Argentina, was constructed based on twodimensional (2-D) and three-dimensional (3-D) seismic information. The synrift structure of the region is characterized by high angle NW-trending normal faults. Two populations can be distinguished: one with an azimuth of 140° and the other one with an azimuth of 105°. The principal half-grabens are accommodated by NEdipping normal faults. The principal NW-trending faults are less than 20 km long and are either crosscut by or terminate in transfer zones trending to the NE. The transfer zones are either faults or zones where the principal NW-trending faults loose slip or terminate. The principal normal faults were active until the deposition of the Lower Upper Jurassic Tordillo Formation. Subsequently, only a few faults related to differential subsidence over the half-grabens remained active. The typical structures of the region are smooth anticlines and synclines that affect the sag facies of Neuquén Basin. The anticlines developed over basement highs and the synclines over graben basins. The synclines are explained in this study as resulting from differential subsidence over the half-grabens. This differential subsidence could have been a continuous process that began in the synrift stage of the basin. A distinct element model was created to analyze the differential subsidence process and geometry. No evidence was found to support the hypothesis that tectonic inversion is an important process in this region. The main unconformities can be explained by the differential subsidence process.