Thumb Member of Horse Spring Formation

Usage of Geologic Unit Name:
Thumb Member* of Horse Spring Formation
Miocene, middle*
Great Basin province*
Type Locality:
Type section: Thumb valley north of Lake Mead, Clark Co, NV (Longwell, 1963). Principal reference section: lat 36 37'30", long 114 56'45" (Bohannon, 1984).
Unit Name History
First used (Longwell, 1952). Named Thumb Formation (Longwell, 1963). Assigned as one of four members of Horse Spring Formation (Bohannon, 1984). Isotopic dating (Bohannon, 1984). Age modified (Bohannon, 1984; Beard, 1993).

Longwell, C.R., 1952, Basin and Range geology west of the St. George Basin, Utah, IN Cedar City, Utah to Las Vegas, Nevada: Utah Geological Society, Guidebook to the geology of Utah, no. 7, p. 27-44, Prepared in cooperation with the Intermountain Association of Petroleum Geologists.

Longwell, C.R., 1963, Reconnaissance geology between Lake Mead and Davis dam, Arizona-Nevada, IN Shorter contributions to general geology, 1960-1964: U.S. Geological Survey Professional Paper, 374-E, p. E1-E51, (incl. geologic map, scale 1:125,000).

Bohannon, R.G., 1984, Nonmarine sedimentary rocks of Tertiary age in the Lake Mead region, southeastern Nevada and northwestern Arizona: U.S. Geological Survey Professional Paper, 1259, 72 p., (incl. geologic map, scale approx. 1:790,000) .

Beard, S.C., 1993, Tertiary stratigraphy of the south Virgin Mountains, southeast Nevada, and the Grand Wash Trough, northeast Arizona, IN Sherrod, D.R., and Neilson, J.E., editors, Tertiary stratigraphy of the highly extended terranes, California: U.S. Geological Survey Bulletin, 2053, p. 29-32 .

Beard, L.S., 1996, Paleogeography of the Horse Spring Formation in relation to the Lake Mead fault system, Virgin Mountains, Nevada and Arizona,in Reconstructing the History of Basin and Range Extension using sedimentology and stratigraphy, Beratan, K.K., ed., Geological Society of America Special Paper 303, p. 27-60.

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Last modified:8/10/2006