Circular 146—Structural geology of Big Hatchet Peak Quadrangle, Hidalgo County, New Mexico

By R. A. Zeller, Jr. (with commentary by S. Thompson III), 1975, 23 pp., 3 figs., 2 sheet.

Supplement to Zeller's Memoir 16 (1965). In the Big Hatchet Peak quadrangle, field evidence indicates three general episodes of deformation. Prior to the deposition of Lower Cretaceous rocks, a deformation in the Precambrian was followed by epeirogenic movements during the Paleozoic and Mesozoic. Differential subsidence beginning in Desmoinesian time formed the Alamo Hueco Basin; reefs developed on the margin between the basin and shelf. Only epeirogenic movements are indicated in the Lower Cretaceous sequence. The episode of greatest structural deformation in the are occurred later than Early Cretaceous deposition and earlier than Tertiary deposition. This orogeny produced large folds, reverse, thrust, and overthrust faults, and probably some high-angle faults. Thrusting in the Big Hatchet Mountains was generally toward the west and southwest, but that in the Sierra Rica apparently was toward the northeast, similar to the general direction indicated on other areas of the region. The Tertiary-Recent deformation produced the Basin and Range topography. In addition to the normal faults bounding the ranges, broad open folds, two systems of high-angle faults, and minor thrust faults were formed.

This report on the structural geology on the Big Hatchet Peak quadrangle is a supplement to the memoir on the stratigraphic geology. Much of the discussion in the introduction to that work is pertinent here and should be reviewed. An index map shows the location of the Big Hatchet Peak quadrangle in Hidalgo County, New Mexico, and the chief geographic features of the region. This oversized 15-min quadrangle covers 296 mi² of typical basin-and-range country. The highest point is Big Hatchet Peak at 8,366 ft above sea level, and the lowest point is at 4,129 ft near Artesian Well in the Hachita Valley. The average elevation in the Big Hatchet Mountains is about 6,000 ft, and that of the Sierra Rica is about 5,000 ft. The most prominent ridges and valleys in the ranges trend northwest and reflect structural control, but faults show little topographic expression. However, exposures of bedrock generally are good.