Geology of the Truth or Consequences area
Russell E. Clemons and Glenn R. Osburn


Rocks exposed in the T or C area range from Precambrian to Recent, with all the systems except Triassic and Jurassic represented. Triassic and possibly Jurassic rocks crop out southeast of Socorro just north of the conference area. Maximum thickness of 5,260 m has been estimated for the Cambrian–Quaternary sedimentary section in the T or C area.

The area has been affected by Precambrian, late Paleozoic, Laramide, and middle to late Tertiary deformations. The Precambrian and Laramide deformations were compressional events involving folding and uplift. The Paleozoic event is evidenced by regional wedging out of units and by small unconformities or missing stratigraphic intervals. Mid- to late Tertiary deformation has been largely normal faulting related to extension along the Rio Grande rift.

The region is dominated physiographically and structurally by basins and ranges created by late Tertiary normal faulting. Alluvium was shed from mountain ranges into closed basins or into the more deeply subsided, en-echelon sequence of basins forming the axis of the Rio Grande rift. Aggradation dominated until about 0.5 my ago, forming the broad, coalesced fan surfaces (bajadas) which are prominent high geomorphic surfaces today. Since capture of the ancestral Rio Grande near El Paso about 0.5 my ago, base level has episodically lowered, causing entrenchment of the river and its tributaries into the deeply incised valleys they now occupy. Man has been a dominant geomorphic agent (especially in 1916 and 1938), creating the Elephant Butte and Caballo reservoirs that have at least temporarily altered the landscape and have become so important to the economy of the area.

Most of the mining districts of Sierra County were discovered and developed  following the construction of railroads through New Mexico in the late 19th century. Early prospecting concentrated on silver and gold. Base metals, especially copper, lead, and zinc, were produced in significant quantities in the early 1900's. Tin was discovered in 1918 along Taylor Creek. Beryllium and tungsten were produced in the Iron Mountain district. Iron and manganese ores were also produced on a small scale. More recently, copper, silver, and gold from the St. Cloud mine, and fluorite and barite, have been produced, but mining exploration and development are dormant at this time.


  1. Clemons, Russell E.; Osburn, Glenn R., 1986, Geology of the Truth or Consequences area, in: Truth or Consequences region, Clemons, R. E.; King, W. E.; Mack, G. H., New Mexico Geological Society, Guidebook, 37th Field Conference, pp. 69-81.

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