On the origin of low angle normal faulting in the southern rio grande rift

Abstract

We reconstruct the stress regime in the East Potrillo and Franklin Mountains. Using modern numerical techniques the stress field and the tectonic history of this region is discussed and extensional veins were compared with the general stress field. The majority of faults were reactivated during the first Rio Grande rift extensional event and occurrence of extensive tilting and rotations occurred. In the East Potrillo Mountains, back tilting by W25°SE and W45°SE oriented along strikes of N30°W are required in order to obtain two homogeneous stress fields. The corrected fault plane shows a significant oblique component in both stress fields. The first stress field corresponds to a fault reactivation with al and a3 oriented N78°E and N69°E respectively, whereas the second stress field is related to the youngest fault oriented N64°W and N61°E respectively. In the Franklin Mountains, tilting is less significant; however two stress fields with similar orientations but different phi values are recognized. The post -Laramide stress history of the region is controlled by different extensional events that influenced the preexisting structures and generated other young fault systems.