[First edition, 1961, Geologic history of the Bright Angel quadrangle, Grand Canyon National Park, Arizona (printed on reverse side of geologic map).] Brahma schist. Consists of bluish-green hornblende with small amounts of quartz, albite, calcite, and pyrite. Interbeds of quartzite and quartz mica schist. Thickness over 15,000 feet. Overlies Vishnu schist. Stands nearly vertical everywhere. Occurs in inner gorge of Grand Canyon, northwestern Arizona. Age is Precambrian (Archean).
[Notable exposures in Granite Gorge of Colorado River and Bright Angel Canyon, Bright Angel 15-min quadrangle, eastern Grand Canyon, Grand Canyon National Park, Coconino Co., northern AZ. See also J.H. Maxson, 1967, Preliminary geologic map of the Grand Canyon and vicinity, Arizona; Eastern section: Grand Canyon Nat. Hist. Assoc., scale 1:62,500.]
[Origin of name not stated. Probably named from Brahma Temple, about 2 mi east of Bright Angel Canyon, Bright Angel Point 7.5-min quadrangle, eastern Grand Canyon, Grand Canyon National Park, Coconino Co., northern AZ.]
[Additional locality information from USGS GNIS database and USGS historical topographic map collection TopoView, accessed on October 9, 2024.]

Source: US geologic names lexicon (USGS Bull. 1350, p. 88).

Pg. 56. Potassium-argon dating gives apparent age of Brahma Schist (Vishnu series) muscovite 1,410 Ma and biotite 1,240 Ma.

Source: US geologic names lexicon (USGS Bull. 1350, p. 88).