Named for exposures near the San Miguel surface (Levings, W. S., 1951, Late Cenozoic erosional history of the Raton Mesa region: Colorado School of Mines Quarterly, v. 46, no. 3) but modified to San Miguel Creek to avoid confusion with other lithostratigraphic units named San Miguel. Type locality is a high pediment remnant at 7,120 to 7,200 ft (2,170 to 2,195 m) altitude in SW1/4 NW1/4 sec 1, T34S, R63W, Las Animas Co, CO in the Las Vegas-Raton basin. Is a bouldery, cobbly, pebbly alluvium covering pediments sloping northward toward the Purgatoire River. Most clasts are basalt, but some are sandstone. The pediments lie 200 to 400 ft (60 to 120 m) above major tributaries of the Purgatoire. Is 20 ft (5 m) thick. The few remnants that are preserved are on high pediments in Las Vegas-Raton basin. Assigned to the lower Pleistocene, Blancan? (1,300,000 to 1,700,000 years B.P.).

Source: GNU records (USGS DDS-6; Denver GNULEX).

A worn right mandible of EQUUS (DOLICHOHIPPUS) sp. cf. E. (D.) SIMPLICIDENS, a fossil horse of probable early Pleistocene Blancan age found in SW1/4 sec. 15, T 22 N, R 21 E, Mora Co., NM, Las Vegas-Raton basin. According to James Honey, written communication, 1992 "if the fossil is truly Blancan, then the age would extend into the Pliocene"; [Honey stated (oral communication, 1992), the Blancan ranges from about 4.8 to 1.8 m.y.].

Source: GNU records (USGS DDS-6; Denver GNULEX).