Fault inversion vs. new thrust generation: A case study in the Malargüe fold-and-thrust belt, Andes of Argentina

The reverse reactivation of pre-existing normal faults has been documented in many orogens. In other cases, the lack of sub-surface information has allowed the construction of both inversion and non-inversion structural models. We will analyze the possibility of fault inversion in one such case, in the Malargüe fold-and-thrust belt in the Andes of Argentina. In order to address this issue, we modeled fault inversion vs. new thrust generation using the ReActiva 2.4 software, and varying the physical parameters for the pre-existing fault and the host rock. The results of modeling are compared to the possible sub-surface characteristics of faults in the Malargüe fold-and-thrust belt. We show that the orientation of these structures in the Andean stress field makes them likely to reactivate if the pre-existing fault planes present a low coefficient of friction and/or fluid overpressure. Both are expectable in the geological setting in which the structures are found. We conclude that fault inversion cannot be dismissed, and should be taken into account for structural models of the Malargüe fold-and-thrust belt. Our results can be extended to other orogens with similar characteristics.