Constraints on Laramide shortening and Rio Grande rift extension in the Franklin Mountains, West Texas and southern New Mexico

Abstract

The Franklin Mountains in west Texas and southern New Mexico contain geologic structures associated with Laramide shortening and Rio Grande rift extension. Laramide shortening affected west Texas and southern New Mexico from late Cretaceous to early Tertiary time, while Rio Grande rift extension began in mid-Tertiary time. Thin-skinned, basement-cored folding, and transpressional tectonic models have been suggested for Laramide deformation, among others. However, a general agreement has not been reached on a single tectonic model. Micro-and macro-structural observations of fault system geometries, kinematics, and dynamics must be completed to provide constraints on tectonic and geologic models for Laramide shortening and Rio Grande Rift extension in west Texas and southern New Mexico. Detailed geologic mapping has been completed in the area of Tom Mays Park, Texas in order to refine the geologic structures and construct better cross-sections in the central Franklin Mountains. Measurements of fault orientations and associated lineations were also collected, which will be used for fault slip analysis of the faults in order to determine principle stress orientations for different periods of deformation present in the region.