Type section of Pedernales dolomite member, upper member of Wilberns formation is in the Johnson City area, Blanco Co., TX on the Llano uplift. Consists mostly of fine-grained minutely to coarsely quartzose, compact to very porous, brown, gray and white dolomite and porous chert at the type where it is 187 ft thick; the bottom 86 ft is fine grained, evenly bedded, a contrast with overlying massive part; entire unit is speckled to mottled purple. Glauconite present only in basal few ft in Johnson City where member overlies Morgan Creek limestone member of Wilberns. Overlies San Saba limestone member in San Saba Co., TX on the Llano uplift. Lower contact is gradational. Thickness is variable; is nowhere less than 70 ft thick nor more than 150 ft thick in San Saba Co., where the dolomite is fine- to medium-grained, gray with spots of glauconite slightly cherty; fragments of fossils found in chert. Overlain by Threadgill member of Tanyard formation (new) of Ellenburger group (rank raised). Late Cambrian age. Geologic maps.

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

Pg. 148, 150, 155-156, pl. 4. Pedernales dolomite member of Wilberns Formation. Uppermost member of formation; lies between San Saba limestone member below and Tanyard formation of Ellenburger group above. Grades downward and laterally into San Saba, an essentially equivalent facies if considered in regional sense. In type area, lower 86 feet is fine-grained and evenly bedded, contrasting sharply with overlying massive coarse-grained part; coarse-grained dolomites are predominantly light-gray and silvery gray with occasional intervals of yellowish-gray or nutria; fine-grained dolomite is yellowish-gray to beige; entire section speckled to mottled with dull dark reddish-purple in varying degrees; glauconite, common elsewhere, is present only in basal few feet of member; some chert present, mostly near top of fine-grained part. Thickness in type area 187 feet; in Cherokee area 70 to 150 feet. Dolomites here named Pedernales were formerly included in Ellenburger limestone. Age is Cambrian.
Type section: along Pedernales River from 1.5 to 3 mi up stream from bridge on Johnson City-Marble Falls Highway, 1 mi north of Johnson City, Blanco Co., central TX.

Source: US geologic names lexicon (USGS Bull. 1200, p. 2964-2965).