Pg. 17 (table 1), 29-30, pl. 1. Box Canyon rhyolite tuff. Described as a typical ignimbrite or welded tuff. Structure is massive; color is cream, gray, or pink. Throughout its occurrence, it forms a plate 40 to 75 feet thick. Lies conformably on Mimbres Peak rhyolite, except in its northernmost exposures, where it lies on Kneeling Nun rhyolite. Age is Tertiary.
Found only in upper 4 mi of Box Canyon, Dwyer quadrangle, [Grant Co.], southwestern NM. Largest outcrop is on southeast slope of Mimbres Peak, where its thickness is about 75 feet.

Source: US geologic names lexicon (USGS Bull. 1200, p. 446).

In the Dwyer quad, southeast of Silver City, Grant Co, NM, Basin-and-Range province, Caballo Blanco Rhyolite and Box Canyon Rhyolite ash-flow tuffs are both reversely magnetized. The Caballo Blanco has been dated at 29.8 m.y. Beneath this is the very striking Mimbres Peak flow-banded rhyolite, which is normally magnetized. Magnetostratigraphic position of Caballo Blanco, Box Canyon, and Mimbres Peak units within a preliminary model of the middle Tertiary paleomagnetic reversal pattern is depicted on fig. 4.

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