First published use. Authors state unit was named in unpublished thesis (Bernt, J., 1982, Univ of ID) for small tributary to Black Leg Creek [presumably in Owyhee Co, ID]. No type locality designated in this report. Occurs at several localities in upper Sheep Creek drainage area, south-central Owyhee Co, ID, Snake River basin. Consists of gray rhyolite that is typically hard, dense, and completely devitrified; abundant rounded to elliptical vesicles up to 3 cm and larger irregular gas cavities containing yellow to orange jasper locally occur near top of flow. Maximum thickness is 90 m. Overlies at various localities Rough Mountain rhyolite (new), Browns Basin tuff (first used), and probably Johnstons Camp rhyolite (first used). Underlies Cougar Point Tuff. Geologic map. Not known if from a local volcanic center or if is early unit from Bruneau-Jarbidge eruptive center and therefore would be assigned to Cougar Point Tuff. Miocene? age.

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