GEOLEX

Summary of Citation: Del Rio

Publication:
Hill, R.T. and Vaughan, T.W., 1898, Geology of the Edwards
   Plateau and Rio Plain adjacent to Austin and San Antonio,
   Texas, with reference to the occurrence of underground waters:
   U.S. Geological Survey Annual Report, 18, pt. 2, p. 193-321

Usage in Publication:
Del Rio clays*

Modifications:	Geologic Province:	Dominant Lithology:
Named	Permian basin Ouachita folded belt province	Clay

Summary:
Named as middle formation of Washita division of Comanche series (Lower Cretaceous). Overlies Fort Worth limestone. Underlies Shoal Creek limestone [Buda Limestone]. Consists of greenish-blue laminated clays that weather dull brown or yellow; thickness 80 ft at Austin, Travis Co, TX in Ouachita tectonic belt province. Measured sections at Austin, Travis Co and Weymuller's Ranch, Kinney Co. Type not designated. Apparently named for Del Rio, TX. Formerly called Exogyra arietina Marl by Shumard (1860) and E. ARIETINA clays of others. Zone of abundant E. ARIETINA occurs in middle part. Near top, clay becomes arenaceous with fossiliferous limestone including GRYPHAEA MUCRONATA. Del Rio clays also noted in Edwards and Val Verde Cos in Permian basin; in Hays, Comal, Bexar, and Uvalde Cos in Ouachita tectonic belt province; and across Rio Grande in MX.

Summary of Citation: Del Rio

Publication:
Hill, R.T., 1901, Geography and geology of the Black and Grand
   Prairies, Texas: U.S. Geological Survey Annual Report, 21,
   pt. 7, 666 p.

Usage in Publication:
Del Rio clay*

Modifications:	Geologic Province:	Dominant Lithology:
Overview	Ouachita folded belt province

Summary:
Is middle formation of three of Washita division of Comanche series at Austin, Travis Co, TX in Ouachita tectonic belt province. Overlies Georgetown limestone; underlies Buda limestone. Is 80 ft thick. Is composed almost entirely of a peculiar greenish-blue, unctuous, laminated clay, gypsiferous in places; light-bluish-gray color when fresh, weathering dull yellow and making a black soil. Chief and most readily distinguishable feature of the clay is the presence, in enormous quantities, of the fossil EXOGYRA ARIETINA Roemer. Occurs south of the Brazos River, and may be considered as the southern extension of Main Street limestone of the northern section (Denison, TX), into which it passes by gradual and horizontal transition. North of the Brazos, in Johnson Co, it begins to assume the character of Main Street limestone. Identified fossils listed. Age is Early Cretaceous.

Summary of Citation: Del Rio

Publication:
Imlay, R.W., 1944, Correlation of Lower Cretaceous formations
   of the coastal plains of Texas, Louisiana, and Arkansas: U.S.
   Geological Survey Oil and Gas Investigations Chart, OC-3, 1
   sheet, scale 1:4,800

Usage in Publication:
Del Rio clay

Modifications:	Geologic Province:	Dominant Lithology:
Not used

Summary:
Grayson shale used in lithostratigraphic correlations of the Gulf Coastal Plain in TX, LA, AR, and northern MX. "Grayson shale (Del Rio)" used in south TX on fig. 4 in Bexar Co, Ouachita tectonic belt province and Frio Co, Gulf Coast basin. [This use of "Grayson shale" instead of "Del Rio clay" was misinterpreted as abandonment of the Del Rio by some subsequent workers.]

Summary of Citation: Del Rio

Publication:
Bullard, F.J., 1953, Polymorphinidae of the Cretaceous (Cenomanian)
   Del Rio shale: Journal of Paleontology, v. 27, no. 3, p.
   338-346

Usage in Publication:
Del Rio shale

Modifications:	Geologic Province:	Dominant Lithology:
Biostratigraphic dating Overview	Ouachita folded belt province

Summary:
Is formation at Austin, Travis Co, TX in the Ouachita tectonic belt province. Overlies Georgetown limestone of Albian (Early Cretaceous) age. Underlies Buda limestone of Cenomanian (Late Cretaceous) age with transitional contact. Main components are bedded calcareous clays and claystone with local sandstone lenses and thin limestones; clays and claystones contain gypsum, pyrite, ferruginous nodules, and bentonitic layers. Is estimated to be 80 ft thick. Tentative correlation of three measured sections is based on megafossils. Microfauna (foraminifers) is noted to be prolific and part is described in detail; it is interpreted to represent a neritic environment of relatively warm, shallow water. Is assigned a Cenomanian age. Albian-Cenomanian boundary is queried at base of formation (fig. 1). Diversity of the polymorphinid faunas supports the hypothesis of Stanton (1947, p. 2) that the base of Del Rio is synchronous with that of Grayson formation; however, doubtful that the two are exact time equivalents.

Summary of Citation: Del Rio

Publication:
Stephenson, L.W., 1953, Mollusks from the Pepper Shale Member
   of the Woodbine Formation, McLennan County, Texas, IN Shorter
   contributions to general geology, 1952: U.S. Geological Survey
   Professional Paper, 243-E, p. E57-E67

Usage in Publication:
Del Rio clay

Modifications:	Geologic Province:	Dominant Lithology:
Not used

Summary:
Not used in this report. "Grayson marl (formerly Del Rio clay)" of Comanche series reported to unconformably underlie Pepper shale member of Woodbine formation of Gulf series in section on Bird Creek, Bell Co, TX, Ouachita tectonic belt province. Age not stated. [Late Cretaceous.]

Summary of Citation: Del Rio

Publication:
Wiggins, P.N., III, 1954, Geology of the Ham Gossett oil field,
   Kaufman County, Texas: American Association of Petroleum
   Geologists Bulletin, v. 38, no. 2, p. 306-318

Usage in Publication:
Del Rio shale

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits	East Texas basin

Summary:
Considered equivalent to Grayson marl. Underlies Buda limestone of Washita group. Overlies Georgetown limestone of Washita group. Is middle formation of Washita group in Comanche series. Is extended in subsurface into southeastern Kaufman Co, TX in the East Texas basin. Thickness in the Ham Gossett field is 80 ft. Depth to top is 4,234 ft. Assigned to Comanche series.

Summary of Citation: Del Rio

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:
Del Rio Clay

Modifications:	Geologic Province:	Dominant Lithology:
Not used	Permian basin

Summary:
Is not used in this report. Grayson Formation (Del Rio Clay of former usage) is mapped in eastern Brewster and southwest Terrell Cos, TX in Permian basin. [No explanation given for choice of nomenclature; probably a result of Imlay's (1944) general use of the Grayson nomenclature, which was misinterpreted as abandonment of the Del Rio by some subsequent workers. Del Rio nomenclature is currently appropriate for south-central to west TX area.]

Summary of Citation: Del Rio

Publication:
Barnes, V.E., 1974, Geologic atlas of Texas, San Antonio Sheet;
   Robert Hamilton Cuyler memorial edition: University of
   Texas-Austin, Bureau of Economic Geology, 1 sheet, scale
   1:250,000

Usage in Publication:
Del Rio Clay

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:250k	Ouachita folded belt province Kerr basin	Clay Siltstone

Summary:
Is Lower Cretaceous formation mapped in discontinuous, highly faulted, northeast-southwest trend in Uvalde, Medina, Bexar, Comal, and Hays Cos, TX (Ouachita tectonic belt province). Overlies Salmon Peak Limestone (Lower Cretaceous) west of Dry Frio River, overlies Devils River Limestone (Lower Cretaceous) between Dry Frio River and Medina River, overlies Edwards Limestone (Lower Cretaceous) east of Medina River, and very small local areas of Del Rio are mapped in northwestern part of map sheet in Real and Kerr Cos, TX (Kerr basin) where Del Rio overlies Segovia Member of Edwards Limestone. Overlain by Buda Limestone (Lower Cretaceous). Del Rio, Buda, and overlying Eagle Ford (Upper Cretaceous) locally faulted-out entirely (e.g. eastern Medina and western Bexar Cos, TX). Map unit described as clay, calcareous and gypsiferous becoming less calcareous and more gypsiferous upward, pyrite common, blocky, medium gray, weathers light gray to yellowish gray; some thin lenticular beds of highly calcareous siltstone; marine megafossils include abundant Exogyra arietina and other pelecypods; thickness 60-120 ft, thickens westward. [Explanation on map sheet shows Buda and Del Rio as Upper Cretaceous, but pamphlet that accompanies map shows Buda and Del Rio as Lower Cretaceous.]

Summary of Citation: Del Rio

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:
Del Rio Formation

Modifications:	Geologic Province:	Dominant Lithology:
Redescribed Overview	Orogrande basin	Shale Limestone

Summary:
Mapped in Cerro de Cristo Rey, Dona Ana Co, NM, Orogrande basin and Chihuahua, MX. Consists of dark-gray shale with some limestone beds and nodules near top and bottom. Forms colluvium-covered slopes. Most extensive outcrops are on north, east, and south sides of Cerro de Cristo Rey intrusion. Thickness is 24-27 m. Conformably overlies Anapra Formation; conformably underlies Buda Formation. EXOGYRA abundant in lower part of unit. Cross sections. Early Cretaceous (Cenomanian, Comanchean) age. [Author places lower part of Cenomanian in Lower Cretaceous.]

Summary of Citation: Del Rio

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:
Del Rio Clay

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Mapped 1:250k	Permian basin Ouachita folded belt province	Clay Siltstone

Summary:
Is Upper Cretaceous formation mapped in southeastern Terrell and in central-southern and southeastern Val Verde Cos, TX (southern part of Permian basin) and central Kinney and central-western Uvalde Cos, TX (Ouachita tectonic belt province). Overlies Devils River Limestone or Santa Elena Limestone near northwestern limit of Del Rio; overlies Salmon Peak Limestone in eastern part of map area. Overlain by Buda Limestone. Is locally mapped with Buda where Del Rio outcrop is too narrow to map near feather edge. Del Rio described as clay; calcareous and gypsiferous becoming less calcareous and more gypsiferous upward, pyrite common, blocky, medium-gray, weathers light-gray to yellowish-gray; some thin lenticular beds of highly calcareous siltstone; marine megafossils include abundant EXOGYRA ARIETINA and other pelecypods; thickness up to 200 ft, feathers out northwestward.

Summary of Citation: Del Rio

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:
Del Rio Clay

Modifications:	Geologic Province:	Dominant Lithology:
Areal limits Mapped 1:250k	Permian basin	Clay

Summary:
Is Lower Cretaceous formation mapped undivided with Buda Limestone in southwestern Terrell, in Brewster, and in southeastern Presidio Cos, TX (southern part of Permian basin). Overlies Santa Elena Limestone (Lower Cretaceous). Overlain by Buda Limestone (Lower Cretaceous). Del Rio described as mostly clay, some interbedded, flaggy, siliceous limestone, friable sandstone, and thin beds of ferruginous clay; clay, soft, bluish to greenish gray, weathers yellow to light brown; thickness up to 180 ft in Terlingua district, 185 ft in western part of Black Gap area, feathers out eastward toward Rio Grande, 70 ft thick in Hood Spring, Santiago Peak, and Tascotal Mesa quadrangles.