Unit is named the Mount Hyatt Member of the Gabbs Formation (revised) of the Volcano Peak Group (new). Formerly the middle member of Muller and Ferguson (1939, GSA Bull., v. 50, no. 10, p. 1573-1624) of the Gabbs Formation. Exposed in the Gabbs Valley Range, west-central Nevada. Consists of grayish-brown to medium- and dark-gray, brownish-gray- to orange-brown-weathering, medium- to thick-bedded, bioclastic, silty to sandy limestone containing interbeds of calcareous siltstone. Conformably overlies the Nun Mine Member (new) and sharply and conformably underlies the Muller Canyon Member (new), both of the Gabbs Formation; contact is drawn above the highest limestone bed of the Mount Hyatt Member. Thickness is 30 m. Age is Late Triassic (Norian), based on fossils.
Type locality: exposures east of Mount Hyatt, New York Canyon, Gabbs Valley Range, Mineral Co., NV.

Source: US geologic names lexicon (USGS Bull. 1565, p. 208); GNU records (USGS DDS-6; Menlo GNULEX).