Geologic units in Tippah county, Mississippi

Porters Creek formation (Paleocene) at surface, covers 26 % of this area

(Midway group), Dark-gray clay, north of Clay County contains slightly glauconitic, micaceous sand lenses.

Ripley formation (McNairy sand member) (Upper Cretaceous) at surface, covers 21 % of this area

(Selma group), Red and white cross-bedded micaceous sand and white sandy clay.

Clayton formation (Paleocene) at surface, covers 19 % of this area

(Midway group), Upper part, greenish-gray coarsely glauconitic sandy clay and marl; lower part, crystalline sandy limestone and loose sand, represented south of Houston by a discontinuous bed of indurated calcareous sandstone.

Ripley formation (Upper Cretaceous) at surface, covers 18 % of this area

(Selma group), Gray to greenish-gray fine glauconitic sand, clay, and sandy limestone; south of Oktibbeha County is very sandy micaceous chalk.

Wilcox formation (Eocene) at surface, covers 8 % of this area

Irregularly bedded fine to coarse sand, more or less lignitic clay and lignite; includes bauxite bearing Fearn Springs sand member at base.

Prairie Bluff chalk and Owl Creek formation (Upper Cretaceous) at surface, covers 7 % of this area

(Selma group), Prairie Bluff chalk, compact brittle chalk, sandy chalk, and calcareous clay; at base contains many phosphatic molds of fossils; in Ponotoc and Union Counties merges northward into Owl Creek formation, tough blue glauconitic sandy clay.

Tallahatta formation and Neshoba sand (Eocene) at surface, covers 0.5 % of this area

(Claiborne group), Southeast of Pearl River predominantly more or less glauconitic claystone and clay with lenses of sand and some sandstone; highly cross-bedded sand at base; northwest of Pearl river predominantly sand, locally glauconitic, containing claystone and clay lenses and abundant clay stringers; Neshoba sand, sparingly glauconitic fairly coarse sand not recognized southeast of Newton County or north of Yalobusha River.

Claiborne and Wilcox Formation (Tertiary) at surface, covers 0.1 % of this area

Irregularly bedded sand, locally interbedded with lenses and beds of gray to white clay, silty clay, lignitic clay, and lignite. Thickness more than 400 feet.

Midway Group including Porters Creek Clay and Clayton Formation (Tertiary) at surface, covers < 0.1 % of this area

Midway Group - includes Porters Creek Clay - Pale-brown to brownish-gray, massive, blocky clay; locally contains glauconitic sand. Thickness 130 to 170 feet. Also includes Clayton Formation- Glauconitic sand, argillaceous and locally fossiliferous; at base in Hardeman County is an impure fossiliferous limestone. Thickness 30 to 70 feet.

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.

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.

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

Sandy clay, greenish gray, glauconitic, fossiliferous; merges northward into unfossiliferous clays and sands. Thickness 0 to about 40 feet.

Demopolis chalk (Upper Cretaceous) at surface, covers < 0.1 % of this area

(Selma group), Chalk and marly chalk containing fewer impurities than underlying and overlying formations.