Named for Mount Vernon Canyon, Golden quad, Jefferson Co, CO in the Southern Rocky Mountain region. No type locality designated. Best exposed in roadcuts in canyon. Forms low, rounded, grass-topped ridges elsewhere. Three distinct rock types in formation. Facies A: most common type is medium- to dark-gray, medium- to coarse-grained, hornblende, plagioclase gneiss. Facies B: light-gray to green, coarse-grained calcite, epidote tactite containing minor diopside, quartz, and mica. Facies C: medium- to coarse-grained, red stained quartz, plagioclase, biotite gneiss. Pink to light-red, coarse-grained quartz, plagioclase, biotite pegmatites intrude Mount Vernon Canyon. Pegmatites generally trend east-west and may be concordant or discordant. Thickness estimated about 2,000 ft. Considered younger than Clear Creek Canyon Formation (new) and older than Idledale Formation (new). Geologic map. Cross section. Precambrian age.

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

Is one of several units defined in a narrow belt along east-central Front Range, near Golden, Jefferson Co, CO in the Southern Rocky Mountain region. Of doubtful use elsewhere. Assumed direction of stratigraphic sequence is debatable. Belongs with pre-1,700 m.y. metamorphic complex, or of Precambrian X age.

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