Geologic units in Tishomingo county, Mississippi

Eutaw formation (Upper Cretaceous) at surface, covers 62 % of this area

More or less cross-bedded and thinly laminated glauconitic sand and clay; basal part includes the McShan formation, greenish-gray, micaceous, locally very glauconitic, very fine-grained sand and thin-bedded light-gray clay, small chert gravels may be present in basal beds, not recognized in northern Tishomingo County.

Tuscaloosa formation (Upper Cretaceous) at surface, covers 13 % of this area

Light and vari-colored irregularly bedded sand, clay, and gravel; gravel is mostly in lower portion.

Eutaw formation (Tombigbee sand member) (Late Cretaceous) at surface, covers 12 % of this area

Massive fine glauconitic sand.

Chester group (Mississippian) at surface, covers 6 % of this area

Limestone, chert, and shale of Meramec, Osage, and Kinderhook age.

Chester group (Mississippian) at surface, covers 4 % of this area

Sandstone, shale, and limestone.

Coffee sand (Upper Cretaceous) at surface, covers 3 % of this area

(Selma group), Light-gray cross-bedded to massive glauconitic sand and sandy clay and calcareous sandstone.

Chester group (Devonian) at surface, covers 0.6 % of this area

Chattanooga shale (Carboniferous or Devonian) and underlying limestones of Early Devonian age.

Alluvial deposits (Quaternary) at surface, covers 0.1 % of this area

Sand, silt, clay, and gravel. In flood plain of Mississippi River more than 100 feet thick; in smaller streams generally less than 20 feet thick.

Eutaw Formation (Cretaceous) at surface, covers 0.1 % of this area

Grayish-green sand, fine-grained, glauconitic, micaceous; interbedded with gray laminated clays which commonly contain carbonized or silicified wood. (Mapped with Coffee except in Hardin County and southeastern Decatur County.) Thickness 0 to 180 feet; thins northward.

High-level alluvial deposits (Quaternary-Tertiary) at surface, covers < 0.1 % of this area

Iron-stained gravel, sand, silt, and clay; variable in thickness but generally less then 60 feet thick.

Coffee Sand (Cretaceous) at surface, covers < 0.1 % of this area

Loose fine-grained sand, light-gray, sparsely glauconitic, locally interbedded with laminated lignitic clay. Thickness 25 to 200 feet; thins northward.

Fort Payne Formation and Chattanooga Shale (Mississippian) at surface, covers < 0.1 % of this area

Fort Payne Formation - Bedded chert and calcereous and dolomitic silicastone; minor coarse-grained limestone and shale. Thin green shale (Maury) at base. Thickness about 200 feet. Chattanooga Shale - Black carbonaceous shale, fissile. Thickness 0 to 70 feet.

Pride Mountain Formation (Mississippian) at surface, covers < 0.1 % of this area

Medium to dark-gray shale, containing one to three units of a variable combination of sandstone and limestone in the lower part; locally contains rare interbeds of dusky-red and greenish-gray mudstone.

Tuscaloosa Group; Gordo Formation (Cretaceous) at surface, covers < 0.1 % of this area

Massive beds of cross-bedded sand, gravelly sand, and lenticular beds of locally carbonaceous partly mottled moderate-red and pale-red-purple clay; lower part is predominantly a gravelly sand consisting chiefly of chert and quartz pebbles. Not mapped east of the Tallapooza River.

Tuscumbia Limestone (Mississippian) at surface, covers < 0.1 % of this area

Light-gray limestone, partly oolitic near top; fine to very coarse-grained bioclastic crinoidal limestone common; light-gray chert nodules and concretions are scattered throughout and are abundant locally. The apparent thickness of the formation in this province varies due to differential dissolution of the carbonate in the unit.

Eutaw Formation (Cretaceous) at surface, covers < 0.1 % of this area

Light-greenish-gray to yellowish-gray cross-bedded, well-sorted, micaceous, fine to medium quartz sand that is fossiliferous and glauconitic in part and contains beds of greenish-gray micaceous, silty clay and medium-dark-gray carbonaceous clay. Light-gray glauconitic fossiliferous sand, thin beds of sandstone, and massive accumulations of fossil oyster shells occur locally in the upper part of the formation in western AL (Tombigbee Sand Member). In eastern AL thin to thick-bedded accumulations of the fossil oyster Ostrea cretacea Morton occur throughout much of the formation.