Is one of two "informally designated members of the Michigamme Slate, a formation in the Baraga Group of the Middle Precambrian Animikie Series of northern Michigan." Crops out west and southwest of Florence, Florence Co, WI (Lake Superior region) in the vicinity of Keyes Lake; apparently anomalous local quartz-rich body within thick sequence of typically "eugeosynclinal" chloritic slates, graywackes, and basic volcanic rocks. "The Keyes Lake member consists of parallel-stratified quartzite, profusely cross-stratified quartzites, and finer quartzose slates that can be traced parallel to strike for different distances. Thin persistent conglomeratic zones are found containing pebbles of rounded red and white strained vitreous quartz, with lesser amounts of quartzite, chert and very rare interlaminated chert and specularite pebbles. The quartzite is compositionally mature (more than 90 percent quartz) but texturally immature (more than 10 percent fine matrix), thus representing sandstone intermediate between quartz wacke and quartz arenite." Paleocurrent flow for both members is toward the southeast; both are thought to have been deposited in a shallow marine environment and derived from somewhat similar source rocks, but they cannot be correlated on a stratigraphic basis.

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