Name applied in an informal sense to one of several small to medium-sized granite and quartz monzonite bodies in the area of the Mullen Creek mafic complex (first used). Is located in central part of T13N, R81W, northeast and west of Big Creek, Carbon Co, WY in the Northern Rocky Mountain region. No type locality designated. Is in contact with hornblende gneiss in south. Cuts metagabbro of the Mullen Creek mafic complex on the north. Is cut by small dikes and sills. May be one granite body or a series of closely spaced sills or dikes. Geologic map. Ranges in composition from granite to quartz monzonite. Has been dated by Rb/Sr whole rock method; lies on two isochrons indicating age of 1,470 +/-160 and 1,715 +/-50 m.y.

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

Named for rocks exposed along Banks of Big Creek and the margins of Big Creek Park, southeast Sierra Madre, Carbon Co, WY in the Northern Rocky Mountain region. No type locality designated. Composed of banded hornblende and feldspathic gneisses of variable composition. Most common type is moderately foliated to granoblastic hornblende gneiss. Has the following mineral assemblage: hornblende, andesine +/-labradorite, +/-quartz, +/-microcline, +/-biotite, +/-garnet, and accessory sphene, idocrase, and epidote. Detailed description of lithology. Geologic map. Is probably overlain by and intertongues with Green Mountain Formation (new). Overlies Archean quartz-biotite gneiss. Three whole-rock samples of hornblendic, feldspathic, and pegmatitic phases yielded an isochron age of 1880 +/-50 m.y, a metamorphic age for the gneiss. Chemical and isotopic data. Considered Proterozoic.

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