DETERMINING STRAIN AXIS DIRECTION FROM RECENT TECTONIC EPISODES IN THE EL PASO TEXAS REGION BY COMPARING THE FRACTURE ORIENTATION OF MULTIPLE EOCENE INTRUSIONS

This project examined the orientation of fractures in rock outcrops in Hueco Tanks State Park and on the University of Texas El Paso (UTEP) campus in southwestern Texas and near Vado in southeastern New Mexico. The results were combined with the results of a previous study of fracture orientations at Three Sisters, near El Paso, TX. Measurements of the strike and dip of fractures at the Vado and UTEP campus sites were made using a Brunton compass, while for Hueco Tanks, measurements were taken from Google Earth images. Outcrops of very prominent fracture systems were photographed using a Gigapan Image System. Possible causes for the fractures occurring include the compressional forces related to the Laramide orogeny, extensional forces that formed the Basin and Range or the Rio Grande rift, or a combination event. Measurements show that if all the fractures are oriented the same way it would indicate a single tectonic event. If they are not all oriented the same way it will indicate multiple events. The preliminary results show fractures throughout the region with a dominant NW-SE orientation which is most likely related to the late stages of Rio Grande Rifting. Two locations also show a minor fracture pattern with a NE-SW orientation which is most likely related to the Laramide orogeny.