Pg. 19-21, pl. 1. Apple Creek Phyllite of Belt Series [Supergroup]. In Lemhi quadrangle, three members of Belt Series, each more than 10,000 feet thick are Apple Creek Phyllite (oldest), Lemhi and Swauger Quartzites. Phyllite is in fault contact with Cheney Volcanics (new). Age is Precambrian.
Type area: in vicinity of Apple Creek and along Hayden Creek, [in R. 23 E., T. 17 N., approx. Lat. 44 deg. 46 min. N., Long. 113 deg. 42 min., in southwestern part of Lemhi quadrangle, Salmon National Forest, Custer Co., east-central ID]. Named from Apple Creek, a tributary of Hayden Creek.

Source: US geologic names lexicon (USGS Bull. 1350, p. 30); GNC index card files (USGS-Menlo); supplemental information from GNU records (USGS DDS-6; Denver GNULEX).

Pg. 10-11. Apple Creek Formation of Lemhi Group. Apple Creek Phyllite of Anderson (1961) adopted as Apple Creek Formation and assigned to Lemhi Group as one of its five formations. Chiefly varicolored siltite with a few lenses of ankeritic sandstone, and in lower part, a few beds of argillite. Interbedded with quartzite in upper and lower parts. The phyllitic character is a result of shearing and is not typical of same formation farther south. Thickness 2,500 to 3,000 feet (760 to 900 m). Overlies Big Creek Formation and underlies Gunsight Formation (both new names and both assigned to Lemhi). Age is Precambrian Y.
Principal reference section: along crest of ridge between Golden Trout Lake and head of Middle Fork of Little Timber Creek, in T. 14 N., R. 24 E., Patterson quadrangle, Challis and Salmon National Forests, Lemhi Co., east-central ID.

Source: Publication; Changes in stratigraphic nomenclature, 1975 (USGS Bull. 1422-A, p. A2-A3); GNC index card files (USGS-Menlo).