Used "informally" in several publications since 1981. Named as basal member of Jack Creek Quartzite (named) of Phantom Lake Metamorphic Suite, Sierra Madre. Named for exposures at Deep Gulch. Recognized also at Dexter Peak, Carrico Ranch, and northeast of Deep Gulch. Type section designated as near Carrico Ranch, NE1/4 sec 12, T15N, R88W, Carbon Co, WY, Northern Rocky Mountain region. Is as much as 110 m thick. Divided into: 1) lower unit or unit 1, a medium- to coarse-grained, poorly sorted arkose interbedded with muscovite-rich arkose, thin quartz-pebble conglomerate layers, and thin arkosic conglomerate layers--unit 1 characterized by large (excess of 10 mm) potassium-feldspar clasts; its conglomerates are poorly sorted; 2) middle unit or unit 2, a coarse-grained muscovite-rich arkose and subarkose which contains well-developed small-scale trough crossbeds and lenticular quartz-granule conglomerate, quartz-pebble conglomerate, and arkosic conglomerate beds; 3) upper unit or unit 3, pyritic and radioactive quartz pebble conglomerates that are interbedded with granular to pebbly subarkosic quartzites. Quartzite fragments more common in unit 3 than in other two. Thought to have been deposited in a braided river system. Unconformably above Vulcan Mountain Metavolcanics (new); underlies upper part of Jack Creek. Geologic map. Petrographic data. Stratigraphic charts. Of Late Archean age.

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