GEOLEX

Summary of Citation: Grayson

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:
Grayson marl*

Modifications:	Geologic Province:	Dominant Lithology:
Overview	S. Oklahoma folded belt province Fort Worth syncline

Summary:
Is top formation of Pottsboro subgroup of Denison beds of Washita division (group) at top of Comanche series in Grayson Co, TX, South Oklahoma folded belt province, and Denton Co, TX, Fort Worth syncline. Overlies Main Street limestone; underlies Woodbine formation. Nature of upper contact is uncertain. Is mapped (Plate LXVI) as part of Denison formation. Consists of light-colored, fossiliferous clays with many small lumps of lime and much iron pyrite. Identified fossils listed. Thickness is 15-60 ft. Ceases to be recognizable by lithologic character south of the Brazos River. Is considered stratigraphically equivalent to Buda limestone of the northern (Austin) section. Age is Early Cretaceous.

Summary of Citation: Grayson

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:
Grayson Formation*

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

Summary:
Is formation mapped in eastern Brewster and southwest Terrell Cos, TX in Permian basin. Del Rio Clay, of former usage, not used in this report. [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.] Overlies Georgetown Limestone; underlies erosional unconformity below Buda Limestone. Map unit described as mostly claystone, poorly exposed, with subordinate sandstone and siltstone. Claystone has some silty beds, is yellowish gray and greenish gray weathering to dark reddish brown, laminated, and contains seams of gypsum and nodules of iron oxides. Sandstone and siltstone is light yellowish gray weathering to dark yellowish orange, well-sorted; glauconitic; friable to firmly cemented with calcite; thin bedded; sparsely fossiliferous. Thickens southwestward from 30 ft to 80 ft. Age is Late Cretaceous.

Summary of Citation: Grayson

Publication:
Barnes, V.E., 1967, Geologic atlas of Texas, Sherman Sheet;
   Walter Scott Adkins memorial edition: University of Texas-Austin,
   Bureau of Economic Geology, 1 sheet, scale 1:250,000

Usage in Publication:
Grayson Marl

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:250k	Fort Worth syncline S. Oklahoma folded belt province Ouachita folded belt province	Marl Limestone

Summary:
Is uppermost Lower Cretaceous formation mapped undivided with Main Street Limestone (Lower Cretaceous) in Denton Co, TX (Fort Worth syncline); eastern Cooke and northern Grayson Cos, TX and southeastern Marshall Co, OK (South Oklahoma folded belt province); and Bryan Co, OK (Ouachita tectonic belt province). Overlies Main Street Limestone; underlies Upper Cretaceous Woodbine Formation (Dexter Member mapped at base of Woodbine locally in TX and unnamed lower member mapped at base of Woodbine locally in OK). Grayson described as mostly marl, light greenish gray to medium gray, near top some thin interbeds of limestone, nodular, slightly sandy, gray, fossiliferous; weathers grayish yellow. Thickness 15-60 ft.

Summary of Citation: Grayson

Publication:
Barnes, V.E., 1972, Geologic atlas of Texas, Dallas Sheet; Gayle
   Scott memorial edition: University of Texas-Austin, Bureau
   of Economic Geology, 1 sheet, scale 1:250,000

Usage in Publication:
Grayson Marl

Modifications:	Geologic Province:	Dominant Lithology:
Mapped 1:250k	Fort Worth syncline Strawn basin Ouachita folded belt province	Clay Marl Limestone

Summary:
Is uppermost Lower Cretaceous formation mapped undivided with underlying Main Street Limestone in mostly continuous, north-south trending belt in west-central part of map sheet. Is mapped in southern Denton Co, TX (Fort Worth syncline); central Tarrant and central Johnson Cos, TX (Strawn basin); and in northwestern Hill Co, TX (Ouachita tectonic belt province). Overlies Main Street Limestone (Lower Cretaceous); overlain by Woodbine Formation (Upper Cretaceous). Grayson Marl described as mostly calcareous clay and marl, blocky, yellowish gray and medium gray; some 0.25-1.0 ft limestone beds in upper one-third, very fine grained, fossiliferous; weathers yellowish brown, forms gentle slope; thickness 60-100 ft, thins northward.

Summary of Citation: Grayson

Publication:
Mancini, E.A., 1982, Early Cenomanian cephalopods from the
   Grayson Formation of north-central Texas: Cretaceous Research,
   v. 3, no. 3, p. 241-259

Usage in Publication:
Grayson Formation

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

Summary:
Is uppermost formation of Washita Group present at Waco Dam Spillway exposure, McLennan Co, TX, Ouachita tectonic belt province. Conformably overlies Main Street Member of Georgetown Limestone; contact is gradational, from wackestone below through interbedded nodular wackestone and argillaceous marl to calcareous claystone. Contact with overlying Buda Limestone (where present) is conformable, grading upward from calcareous claystone interbedded with nodular wackestone to wackestone. Where Buda is eroded (as at this locality), Grayson is disconformably overlain by Pepper Shale. 24 m thick in outcrop--consists of gray, calcareous claystone that weathers brown, interbedded with white nodular wackestone, brown thin-bedded calcareous siltstone, and red-weathering laminated or massive mudstone. Can be divided into a lower calcareous claystone interbedded with mudstone, a middle claystone interlaminated with pyritic or limonitic seams, and an upper calcareous claystone interbedded with siltstone and nodular wackestone. Claystone consists of about 96 percent clay to medium silt. Lowest beds contain late Albian (Early Cretaceous) ammonite fauna. Ammonites MANTELLICERAS cf. CANTIANUM, M. SAXBII, SHARPEICERAS MEXICANUM, and (?)PARACALYCOCERAS sp. indicate early Cenomanian age for Grayson at this locality. These ammonites have previously been recorded from Buda Limestone interval that overlies Grayson elsewhere in north-central TX.