Geologic units in Chester county, Tennessee

McNairy Sand (Cretaceous) at surface, covers 39 % 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.

Midway Group including Porters Creek Clay and Clayton Formation (Tertiary) at surface, covers 31 % 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.

Claiborne and Wilcox Formation (Tertiary) at surface, covers 16 % 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.

Coon Creek Formation (Cretaceous) at surface, covers 7 % of this area

Fossiliferous, micaceous sand, silty and glauconitic; locally fossiliferous sandy clay at base. Siderite concretions common in upper part. Thickness about 140 feet.

Alluvial deposits (Quaternary) at surface, covers 6 % 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.

Demopolis Formation (Cretaceous) at surface, covers 1 % of this area

Marl and calcareous clay, light-gray, fossiliferous, locally glauconitic and sandy. Merges northward into sands mapped as Kcc. Maximum thickness 180 feet.

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.

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

Quartz sand and glauconite sand, argillaceous and locally fossiliferous. (Mapped with Kcc north of Beech River.) Maximum thickness 70 feet.