Late Paleozoic right-slip faults in the Ancestral Rocky Mountains
— Lee A. Woodward, Orin J. Anderson, and Spencer G. Lucas

Right-lateral separation of about 145 km, defined by offset magnetic anomalies along several northtrending fault zones in northern New Mexico, vastly exceeds the 5-20 km of right slip that can be accommodated by Laramide (Late Cretaceous–Paleogene) deformation. The dominance of brittle structures where these faults are exposed suggests that most of the 125 km of pre-Laramide offset occurred during the late Paleozoic rather than during the Precambrian, when ductile deformation was likely. Right slip along north-striking, late Paleozoic faults may support a tectonic model involving northeast–southwest crustal shortening related to a northwest-trending subduction zone along the southwestern margin of North America. The resultant regional stress field would have been similar to that of the Laramide orogeny in the Southern Rocky Mountains, when north-striking faults underwent right slip. Recognition of right slip along late Paleozoic, north-striking faults in the southern Rocky Mountains has implications for Laramide tectonics inasmuch as total offset of the magnetic anomalies cannot be attributed solely to Laramide deformation.