Tectonic Framework of Cordilleran Foldbelt in Southwestern New Mexico

Abstract

The Cordilleran foldbelt trends west-northwest through the southwestern corner of New Mexico and is characterized mainly by flat thrust faults and subordinate, closely compressed, overturned folds of Laramide age. Postorogenic Cenozoic volcanic and sedimentary rocks cover much of the region, and only scattered areas of preorogenic and synorogenic rocks are exposed; this cover, in addition to superimposed Basin-Range deformation, makes regional structural synthesis difficult. Apparently, however, the contact of the foldbelt with the platform on the north is marked by thrust faults exposed in the Florida, Victorio, and central Peloncillo Mountains. Yielding on the thrust is northward toward the foreland, with displacement as much as several miles. Anomalous minor thrusts in the Big Hatchet Mountains that appear to have yielded toward the southwest are of unknown origin. The regional distribution of thrusts suggests that the entire foldbelt in this region is underlain by thrusts, even though considerable parts of the preorogenic sedimentary section may have escaped deformation in some localities. In southwestern New Mexico, the zone separating the area of the foldbelt from the less deformed foreland on the north appears to mark the Texas lineament.