Pg. 149. [/]Mariposa group. In Sierra Nevada, California, between Stanislaus River and Mariposa Creek, a distance of 45 miles, the Bedrock Complex is divided into 2 groups, Tuolumne group and Mariposa group. The latter unconformably overlies the former, and consists of over 3,000 feet of acid and intermediate volcanics, sandstones, and cherts and 2,000 to 2,500 feet of slates. On Merced River and southward into Indian Gulch quadrangle, [Mariposa group] is divided into Mariposa slates above, 2,000+/- feet thick, and Indian Gulch agglomerates, tuffs, sandstones, and conglomerates, 3,500 feet thick below. Age is Mesozoic.
[Name preempted by Mariposa slates (Mariposa beds of Becker, 1885). Not adopted by the USGS.]

Source: U.S. geologic names lexicon (USGS Bull. 896, p. 1302); GNU records (USGS DDS-6; Menlo GNULEX).

On road log map Mariposa Group divided into: Brushy Canyon Formation (new), unnamed "rhyolite", Mariposa Slate, Briceburg Formation (new), and unnamed "upper volcanics". Mariposa Slate overlies Brushy Canyon Formation (contact can be seen opposite Negro Hill) [no longer exists; now submerged beneath Folsom Lake]. Briceburg Formation apparently conformably overlies Penon Blanco Formation near summit of Bear Creek grade. Legend of generalized map of road log shows Mariposa Group overlies Amador Group and age of both groups as Late Jurassic. In text Brushy Canyon is referred to as "Brushy Canyon Member" of Mariposa Formation. Mariposa is referred to as "Mariposa Slate Member" of Mariposa Formation.

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