GEOLEX

Summary of Citation: Ernst

Publication:
Maxwell, R.A. and Hazzard, R.T., 1967, Stratigraphy, IN Maxwell,
   R.A., and others, Geology of Big Bend National Park, Brewster
   County, Texas: University of Texas-Austin, Bureau of Economic
   Geology Publication, no. 6711, p. 23-156

Usage in Publication:
Ernst Member

Modifications:	Geologic Province:	Dominant Lithology:
Named	Permian basin	Limestone Siltstone Clay

Summary:
Named lower member of 2 in Boquillas Formation (revised) in Terlingua Group (revised) of Gulfian Series. Named from Ernst Tinaja about 2 mi east-northeast of old Boquillas PO, Brewster Co, TX (southern part of Permian basin). Type not designated. Three sections (measured by planetable) in San Vicente-Hot Springs area; complete section of Ernst about 1 1/2 mi north of Rio Grande (pl. VIII, no. 21) is 469 ft thick. Overlies Buda Limestone. Underlies San Vicente Member (new) of Boquillas; the two members separated by erosion surface difficult to distinguish unless units are fossiliferous. Ernst is approximately equivalent to Udden's (1907) Boquillas Flags. About 450 ft thick and consists of silty limestone flags, siltstone, and calcareous clay. Flagstones usually 2-5 in thick with some as thick as 10-18 in. Clay partings not prominent on fresh surfaces, but in vertical weathered surfaces they disintegrate like mortar in an old brick wall, leaving harder flagstones well exposed. Flagstone and clay are bluish gray of fresh surfaces; weather light yellowish gray or buff. Fossil ammonites, pelecypods, echinoids, and foraminifers identified. Ammonites establish at least a partial correlation with the Eagle Ford elsewhere in TX. Correlates (pl. VIII) with lower part of Sawmill Mountain Member of Boquillas Formation in Agua Fria area, northwest of the Park. Shown as Turonian and Coniacian on Table 2. Late Cretaceous age.

Summary of Citation: Ernst

Publication:
Barnes, V.E., 1979, Geologic atlas of Texas, Emory Peak-Presidio
   Sheet; Joshua William Beede memorial edition: University of
   Texas-Austin, Bureau of Economic Geology, 1 sheet, scale
   1:250,000

Usage in Publication:
Ernst Member

Modifications:	Geologic Province:	Dominant Lithology:
Overview	Permian basin

Summary:
Is lower member of two in the Upper Cretaceous Boquillas Formation as mapped in Presidio and Brewster Cos, TX in southern part of Permian basin. Ernst is not separately mapped. Overlies Buda Limestone (Lower Cretaceous). Overlain by San Vicente Member of Boquillas Formation. Is equivalent to Boquillas Flags in eastern part of map area. Consists of limestone, siltstone, and clay; limestone, silty ranging to siltstone, flaggy, beds mostly 2 to 5 in thick, some as thick as 18 in; clay, mostly as partings; bluish gray, weathers light yellowish gray to light brownish yellow, blocky from joints; marine megafossils and microfossils common. Thickness: 277 ft in Black Gap area, 450 ft in Big Bend National Park, 600+ ft in Tascotal Mesa quadrangle, and 1,000 ft in Terlingua area.

Summary of Citation: Ernst

Publication:
Barnes, V.E., 1982, Geologic atlas of Texas, Fort Stockton Sheet;
   Charles Laurence Baker memorial edition: University of
   Texas-Austin, Bureau of Economic Geology, 1 sheet, scale
   1:250,000

Usage in Publication:
Ernst Member

Modifications:	Geologic Province:	Dominant Lithology:
Overview	Permian basin

Summary:
Is lower member of two in Boquillas Formation as mapped south of Del Norte Mountains in Brewster Co, TX (southern part of Permian basin). Ernst Member not separately mapped. Overlies Buda Limestone. Overlain by San Vicente Member of Boquillas. Consists of limestone, siltstone, and clay; limestone, silty, ranging to siltstone, flaggy; clay mostly as partings, bluish gray, weathers light yellowish gray to light brownish gray, blocky from joints; marine megafossils and microfossils common. Is not recognized in southeastern part of map area (southern Terrell Co, TX). Age is Late Cretaceous.