Geology of Fort Burgwin Ridge, Taos County, New Mexico

A strip in Taos County, New Mexico, eight miles long and three miles wide along New Mexico Highway 3 from U.S. Hill to Talpa, Fort Burgwin Ridge, has outcrops of Precambrian metaquartzite (1800 my bp) and cataclastic granite (1760 my bp) overlain by Mississippian limestone and Pennsylvanian fan delta sediments of the western Taos Trough. Twelve cross sections are used to demonstrate (1) Pennsylvanian syndepositional vertical movements, (2) Laramide thrusting that folded the Mississippian and Pennsylvanian rocks along splay faults to the east of the Pecos-Picuris Fault (see Fig. 40), and (3) Late Miocene to present-day normal and strike slip faulting, which is related to Rio Grande Graben rifting and appears to have reactivated earlier fault zones. The north-trending structures appear to be subsidiary to the Pecos-Picuris Fault, a major geofracture that parallels the map area to the west.