Geologic units in Hardeman county, Tennessee

Claiborne and Wilcox Formation (Tertiary) at surface, covers 66 % 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.

Alluvial deposits (Quaternary) at surface, covers 17 % 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.

Midway Group including Porters Creek Clay and Clayton Formation (Tertiary) at surface, covers 10 % 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.

High-level alluvial deposits (Quaternary-Tertiary) at surface, covers 4 % of this area

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

McNairy Sand (Cretaceous) at surface, covers 2 % of this area

Predominantly sand, in places interbedded with silty light-gray clays. Fine-grained sand at base, locally contains heavy minerals. Thickness about 300 feet.

Owl Creek Formation (Cretaceous) at surface, covers 0.9 % of this area

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

Loess (Quaternary) at surface, covers < 0.1 % of this area

Clayey and sandy silt, gray to brown, massive. Maximum thickness about 100 feet along bluffs of Mississippi River; thins eastward. (Minimum mapped thickness 4 feet.)