Named for Green Creek on northeast side of Cache Peak, Albion Range, Cassia Co, ID in the Northern Rocky Mountain region. No type locality designated. Consists predominantly of porphyroblastic biotite-quartz-plagioclase-microcline gneiss. Porphyroblasts range from 1 cm to more than 6 m long. Plagioclase-quartz-biotite schist and lenses, pods, and sheets of quartz-plagioclase-hornblende-amphibolite are associated with the gneiss. Some green quartzite is part of the complex. Exposures on Mount Harrison suggests the gneiss intrudes the biotite schist. Many of the amphibolite bodies represent sills and dikes younger than the gneiss. Is equivalent to lower part of Harrison Group of Felix (1956), to entire Harrison Formation of Stringham (1962). Has a whole rock Rb-Sr isochron age of 2.4 b.y. for schist and gneiss. Unconformably underlies Elba Quartzite (new) of Cambrian? age of Dove Creek Group (new). Geologic map; mapped in the southern central, and northeast part of the Albion Range. Is the oldest unit mapped in the area.

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