GEOLEX

Summary of Citation: Boquillas

Publication:
Udden, J.A., 1907, A sketch of the geology of the Chisos country,
   Brewster County, Texas: University of Texas Bulletin, no.
   93, 101 p.

Usage in Publication:
Boquillas flags

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

Summary:
Named as basal formation of Upper Cretaceous in vicinity of Boquillas PO, along west flank of Carmen Range, southeast Brewster Co, TX in Permian basin. Type not designated. Is thin-bedded (average 4-8 in thick), closely jointed, fossiliferous, flaggy limestone separated by delicate clayey seams that are most apparent when weathered. Thickness 285 ft; upper 150 ft contains considerable amount of less-indurated chalky ledges. Color variable, characteristically cream grayish white with faint ferruginous red stain common in Boquillas region; elsewhere some ledges are dark and almost black on fresh fractures. Is noted to occur around Mariscal Mountain; on south, east, and north sides of Christmas Mountain; west of Terlingua Creek from Cuesta Blanca to Reed Plateau; and south of Terlingua, still further west beyond Chisos region. Overlies Buda limestone (Lower Cretaceous); underlies and grades into Terlingua beds (new). Is considered western equivalent of Eagle Ford shales to the east. Foraminifer and mollusk fossils listed. Age is Late Cretaceous.

Summary of Citation: Boquillas

Publication:
Moon, C.G., 1953, Geology of Agua Fria quadrangle, Brewster
   County, Texas: Geological Society of America Bulletin, v.
   64, no. 2, p. 151-196

Usage in Publication:
Boquillas flags

Modifications:	Geologic Province:	Dominant Lithology:
Overview	Permian basin

Summary:
Is lowest formation of three in Gulf series in Agua Fria 15-minute quadrangle, southwestern Brewster Co, TX (in southern part of Permian basin). Unconformably overlies Buda limestone of Comanche series. Overlain by Terlingua beds of Udden (1907). Gradational contacts, insufficiently detailed paleontological work in the Trans-Pecos region, and vague definitions of formational boundaries result in many stratigraphic problems for Gulf series rocks in the area. For purposes of discussion and mapping, the Boquillas-Terlingua sequence is divided into lower and upper units: "lower Boquillas-Terlingua unit" (approximate equivalent of Udden's Boquillas flags) and "upper Boquillas-Terlingua unit" (approximate equivalent of Udden's Terlingua beds). Boquillas-Terlingua contact lies somewhere within 300 ft of gradational strata between the "CRIOCERAS" zone and the INOCERAMUS UNDULATOPLICATUS zone. Base of Fizzle Flat lentil (new) is arbitrarily selected as boundary between lower and upper units. Lower unit divided into a lower nodular (about 210 ft thick), a middle terraced member (about 205 ft thick), and an upper shaly member (about 100 ft thick). Measured sections described. Map scale 1:62,500. Stratigraphic distribution of molluscan fossils is discussed. Age is Late Cretaceous.

Summary of Citation: Boquillas

Publication:
Freeman, V.L., 1964, Geologic map of the Indian Wells quadrangle,
   Terrell and Brewster Counties, Texas: U.S. Geological Survey
   Miscellaneous Investigations Series Map, I-395, 1 sheet,
   scale 1:62,500

Usage in Publication:
Boquillas Flags*

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:62.5k	Permian basin	Limestone Claystone

Summary:
Is formation mapped in eastern Brewster and southwest Terrell Cos, TX in Permian basin. Overlies Buda Limestone with erosional unconformity; underlies Pleistocene gravel with angular unconformity. Map unit described as dark gray, olive-gray, brownish-gray and yellowish-gray, thin- to very thin-bedded limestone and clayey silty limestone, interbedded with black thinly laminated limy claystone. Beds in lower 25 ft are cross-laminated, lenticular, and more resistant than overlying beds. Remaining thickness beneath unconformity about 100 ft. Age is Late Cretaceous.

Summary of Citation: Boquillas

Publication:
Maxwell, R.A. and Dietrich, J.W., 1965, Geologic summary of the
   Big Bend region, IN Geology of the Big Bend area, Texas; with
   road log and papers on natural history of the area: West
   Texas Geological Society Special Publication, no. 65-51,
   October, 1965, p. 11-33

Usage in Publication:
Boquillas Formation

Modifications:	Geologic Province:	Dominant Lithology:
Revised	Permian basin

Summary:
Is revised to include both the Boquillas Flags of Udden (1907) and the lower member of his Terlingua Beds. Is divided into the Ernst Member (new, at base) and the San Vicente Member (new, above) in Big Bend National Park area, Brewster Co, TX in the Permian basin. Is basal formation (of two) in Terlingua Group (revised). Overlies Buda Limestone; underlies Pen Formation (new) of Terlingua Group. Is 805-875 ft thick in study area. [Table 2 shows Boquillas as Turonian and Coniacian (part); however, Table 5 clearly shows the Ernst Member as both Cenomanian (part) and Turonian on the basis of ammonites.] Age is Cenomanian (part), Turonian, and early Coniacian (Late Cretaceous).

Summary of Citation: Boquillas

Publication:
St. John, B.E., 1966, Geology of Black Gap area, Brewster County,
   Texas: University of Texas-Austin, Bureau of Economic Geology
   Geologic Quadrangle Map, 30, 1 sheet, scale 1:62,500

Usage in Publication:
Boquillas Formation

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:62.5k	Permian basin	Limestone Shale

Summary:
Is lower formation of two in Terlingua Group. Is mapped in the Black Gap area, Brewster Co, TX in southern part of Permian basin. Overlies Buda Limestone of Comanche Series. Overlain by Pen Clay. Consists of two members: Ernst Member, includes the lower flaggy beds, 277 ft thick; and overlying San Vicente Member, includes the chalky limestone and calcareous shale, 274 ft thick, above the flaggy beds and below the gypsiferous Pen Clay. Members are not separately mapped; composite thickness is 551 ft. Crops out in Black Gap area within northwest-trending structural and topographic low extending from Stillwell, Heath, and Horse Canyons northwest through Black Gap headquarters to State Hwy 385; broadest area of outcrop is between Black Gap and Maravillas Canyon. INOCERAMUS LABIATUS is common in Ernst Member and occurs in lower 125 ft of San Vicente Member. Concentration of INOCERAMUS UNDULATOPLICATUS that occurs 35 to 50 ft above base of San Vicente is considered to be the I. UNDULATOPLICATUS zone. Age is Cretaceous.

Summary of Citation: Boquillas

Publication:
Lovejoy, E.M.P., 1976, Geology of Cerro de Cristo Rey uplift,
   Chihuahua and New Mexico: New Mexico Bureau of Mines and
   Mineral Resources Memoir, no. 31

Usage in Publication:
Boquillas Formation

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Overview	Orogrande basin

Summary:
Mapped in Cerro de Cristo Rey, Dona Ana Co, NM, Orogrande basin and Chihuahua, MX. Small exposures form slopes on north and south sides of Cerro de Cristo Rey intrusion. Andesite sills have intruded shales of Boquillas. Unconformably overlies Buda Formation; unconformably underlies Fort Hancock Formation. Cross sections. Late Cretaceous (Gulfian) age.

Summary of Citation: Boquillas

Publication:
Barnes, V.E., 1977, Geologic atlas of Texas, Del Rio Sheet;
   Robert Thomas Hill memorial edition: University of Texas-Austin,
   Bureau of Economic Geology, 1 sheet, scale 1:250,000

Usage in Publication:
Boquillas Flags

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Mapped 1:250k	Permian basin	Shale Limestone Siltstone

Summary:
Is Upper Cretaceous formation mapped in southern Terrell and southern Val Verde Cos, TX (southern part of Permian basin). Facies change eastward is gradual from Boquillas Flags to Eagle Ford Group; nomenclature change arbitrarily placed at Devils River, Val Verde Co. Overlies Buda Limestone; overlain by Austin Chalk. Map unit consists of four units (not mapped separately): upper unit mostly shale, silty, medium-gray, interbedded with some limestone, nodular to laminar, granular, brownish-gray; followed downward by shale, silty, medium-gray, interbedded with limestone, granular, yellowish-gray; shale, silty, dark-gray, interbedded with siltstone, laminated, grading upward to silty limestone; and a basal unit of limestone, clastic, in thin mostly cross-laminated beds that pinch and swell along strike, interbedded with siltstone, light yellowish-gray to grayish-orange. Thickness 160-220 ft.

Summary of Citation: Boquillas

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:
Boquillas Formation, Boquillas Flags

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:250k	Permian basin	Shale Limestone Siltstone

Summary:
Is Upper Cretaceous formation mapped in Presidio, Brewster, and Terrell Cos, TX in southern part of Permian basin. Overlies Buda Limestone (Lower Cretaceous). Overlain by Pen Formation (Upper Cretaceous) in most of area; Boquillas Flags, in eastern part of area, overlain by Austin Chalk. Boquillas Formation consists of an upper unit, San Vicente Member, equivalent to lower part of Austin Chalk; and a lower unit, Ernst Member, equivalent to Boquillas Flags; members not separately mapped. Boquillas Flags, in eastern part of sheet, consists of four units: upper unit, shale, silty, medium gray, interbedded with limestone, nodular to laminar, granular, brownish gray; followed downward by shale, silty, medium gray, interbedded with limestone, granular, yellowish gray; shale, silty, dark gray, interbedded with siltstone, laminated, grading upward to silty limestone; and a lower unit of limestone, clastic, in thin mostly cross-laminated beds, interbedded with siltstone, light yellowish gray to grayish orange, and shale, black. Thickness 100-450 ft.

Summary of Citation: Boquillas

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:
Boquillas Formation

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:250k	Permian basin	Shale Limestone Siltstone

Summary:
Is Upper Cretaceous formation mapped in southern Terrell Co, TX and west-central Brewster Co, TX (both in southern part of Permian basin). Overlies Buda Limestone. Overlain by Gulfian rocks undivided. In southeastern map area (southern Terrell Co)--top part eroded, on adjacent sheets consists of four units: upper unit mostly shale, silty, medium gray, interbedded with some limestone, nodular to laminar, granular, brownish gray; followed downward by shale, silty, medium gray, interbedded with limestone, granular, yellowish gray; shale, silty, dark gray, interbedded with siltstone, laminated, grading upward to silty limestone; and a basal unit of granular limestone, in thin, mostly cross-laminated beds, interbedded with siltstone, light yellowish gray to grayish orange, and shale black; thickness remaining probably less than 100 ft. South of Del Norte Mountains (west-central Brewster Co), San Vicente (upper) and Ernst (lower) Members are recognized, but not separately mapped; thickness not stated. Age is Late Cretaceous.

Summary of Citation: Boquillas

Publication:
Cobban, W.A., 1988, Tarrantoceras Stephenson and related ammonoid
   genera from Cenomanian (Upper Cretaceous) rocks in Texas and
   the Western Interior of the United States: U.S. Geological
   Survey Professional Paper, 1473, 51 p.

Usage in Publication:
Boquillas Limestone*

Modifications:	Geologic Province:	Dominant Lithology:
Biostratigraphic dating	Permian basin

Summary:
Lower part of flaggy limestone member (6-12 ft above base of formation) is assigned a late middle Cenomanian (Late Cretaceous) age based on probable identification of the ammonite TARRANTOCERAS SELLARDSI from USGS Mesozoic locality D11320 on Gold Hill, northern Jeff Davis Co, TX in the Permian basin. Fauna places lower part of unit in CUNNINGTONICERAS AMPHIBOLUM AMPHIBOLUM subzone of AMPHIBOLUM zone.

Summary of Citation: Boquillas

Publication:
Cobban, W.A., 1988, The Late Cretaceous ammonite Spathites Kummel
   and Decker in New Mexico and Trans-Pecos Texas, IN Cobban,
   W.A., Kennedy, W.J., and Hook, S.C., Contributions to Late
   Cretaceous paleontology and stratigraphy of New Mexico; Part
   II: New Mexico Bureau of Mines and Mineral Resources Bulletin,
   no. 114, p. 5-21

Usage in Publication:
Boquillas Limestone*

Modifications:	Geologic Province:	Dominant Lithology:
Biostratigraphic dating	Permian basin

Summary:
Collection from a 20-cm-thick bed of chalky limestone 20 m above base is assigned a middle Turonian (Late Cretaceous) age based on presence of the ammonite SPATHITES RIOENSIS from USGS Mesozoic locality D11193 on Gold Hill, 2.15 km N 53 degrees E of Gomez Peak, Jeff Davis Co, TX in the Permian basin.