Geology of southwestern New Mexico
Russell E. Clemons and Greg H. Mack
Rocks exposed in southwestern New Mexico range from Precambrian to Recent, with all systems except Triassic and Jurassic represented. Maximum thicknesses of the Cambrian-Quaternary sedimentary sections range from about 3700 m near Deming to 11,000 m in the extreme southwestern corner of the state. The majority of the section in the northeast part of this area is of Cenozoic age; upper Paleozoic and Mesozoic sections thicken southwestward into the Pedregosa basin.
Precambrian, Paleozoic, Laramide and middle to late Tertiary deformations are documented in the region. The Precambrian and Laramide episodes were compressional involving folding and uplift. The Laramide event may have had associated wrench faulting. Cambro-Ordovician alkalic plutonism probably had contemporaneous regional uplift. Subsequent Paleozoic deformational events are evidenced by regional wedging out of units and unconformities or missing stratigraphic units on the Burro-Florida uplift. Middle to late Tertiary deformation has been large scale cauldron volcanism followed by Basin and Range extensional faulting.
Southwestern New Mexico is part of the Mexican Highland Section of the Basin and Range Physiographic Province. The region is dominated physiographically and structurally by north-trending basins and ranges formed by late Tertiary normal faulting. The Gila Conglomerate is composed of alluvium shed from the uplifted fault blocks into closed or nearly closed basins since early Miocene time. Relatively large, shallow lakes occupied parts of the Animas and Playas Valleys and possibly the Hachita Valley during the Pleistocene.
Most of the mining districts of southwestern New Mexico were discovered and developed following the Civil War in the late 1800s. Just about every mountain range has at least one mining district or group of prospects. Early prospecting concentrated on gold and silver, but when the railroads came in the 1880s interest increased in prospecting for other materials. Copper, lead, zinc and manganese have been produced in significant quantities. Minor production of fluorite, barite, tungsten and bismuth are recorded. Most mining and development are dormant at this time but exploration continues sporadically, especially for the precious metals. Oil and gas exploration has been intermittent with the most recent activity ending in 1985.
- Clemons, Russell E.; Mack, Greg H., 1988, Geology of southwestern New Mexico, in: Cretaceous and Laramide tectonic evolution of southwestern New Mexico, Mack, G. H.; Lawton, T. F.; Lucas, S. G., New Mexico Geological Society, Guidebook, 39th Field Conference, pp. 45-57.