Wyoming Geological Association: 1982 Luncheon Meetings Casper, Wyoming: Abstracts of Papers

The Burro Mountains are the largest exposure of Precambrian rocks in southwestern New Mexico. This mountain range represents the core of the Burro Uplift which was named in 1958 by Wolfgang E. Elston. The Uplift, centered 16 miles southwest of Silver City, New Mexico, was initiated during Late Mississippian and Early Pennsylvanian time and intensified at the end of the Pennsylvanian.

From its southeast end near the Florida Mountains, the Burro Uplift continues 110 mi northwest to the Clifton-Morenci Mining District of Arizona. The width varies from 40 to 60 mi. The entire region of southwestern New Mexico and the adjacent part of southeastern Arizona has been affected by the Burro Uplift. Evidence for this positive feature is demonstrated on its northeast flank by progressive downcutting into Permian sediments. Southwestward, the truncation is continued down through the remaining Paleozic section to Precambrian granite. Detailed mapping in the Treasure Mountain area, on the northeast flank of the Burro Uplift, was combined with regional reconnaissance to illustrate this angular unconformity. Lower Cretaceous detritus has been identified on its southwestern flank as having been derived from the uplifted structure.

The northwest trend of the Burro Uplift closely follows the prediction for second-order drag folds which are formed by primary left-lateral wrench faults. The southeast end of the Burro Uplift terminates near the Texas Lineament which has been described as a major wrench fault. Paleozoic plate-tectonic relationships are uncertain. The Burro Uplift lies 300 mi northwest of the Appalachian-Quachita-Marathon orogenic belt and 500 mi east of the Antler-Sonoma orogenic belt. Both of these distant orogens were active during the late Paleozoic.