Pg. 296, 298-299 (pl. 1), 301-302. Osceola Argillite. Name proposed for 1 of 6 formations of the McCoy Creek Group (new). Is a highly distinctive formation. Most rocks of formation are slate gray in medium to more rarely dark shales, commonly with bluish or purplish hues. Greenish colors common but restricted to laminae in strikingly banded varieties. Ranges from argillaceous to silty; breaks into blocky, platy slabs. Locally, exhibits graded-bedding and cross-bedding. Thickness 800 feet. Conformably overlies Shingle Creek Conglomeratic Quartzite (new) of McCoy Creek Group; underlies Stella Lake Quartzite (new) of McCoy Creek Group. South of Shingle Creek, Drewes (1958, GSA Bull., v. 69, no. 2) mapped unit as "unnamed slate member" within lower part of Prospect Mountain Quartzite and gave thickness of about 300 feet. Also previously mapped as Lower Cambrian "unnamed purple argillite." Age is late Precambrian. Report includes geologic map.
Type locality: slightly northwest of Strawberry Peak in the southern Snake Range, Windy Peak 7.5-min quadrangle, White Pine Co., NV. Complete section exposed on northern slope of Strawberry Peak and also about 2 mi east of Osceola, on east side of range crest, northern part of southern Snake Range. Origin of name not stated, but probably named from town of Osceola, on east side of southern Snake Range in White Pine Co., NV (Great Basin region).

Source: US geologic names lexicon (USGS Bull. 1350, p. 545); GNU records (USGS DDS-6; Denver GNULEX).

Age of the Osceola Argillite is Precambrian Z.

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