Geologic units in Alcorn county, Mississippi

Coffee sand (Upper Cretaceous) at surface, covers 39 % of this area

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

Demopolis chalk (Upper Cretaceous) at surface, covers 23 % of this area

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

Ripley formation (Upper Cretaceous) at surface, covers 19 % 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.

Ripley formation (McNairy sand member) (Upper Cretaceous) at surface, covers 16 % of this area

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

Eutaw formation (Tombigbee sand member) (Late Cretaceous) at surface, covers 2 % of this area

Massive fine glauconitic sand.

Coon Creek Formation (Cretaceous) at surface, covers 0.3 % 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.

Demopolis Formation (Cretaceous) at surface, covers 0.2 % 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.

Alluvial deposits (Quaternary) at surface, covers 0.2 % 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.

McNairy Sand (Cretaceous) at surface, covers 0.2 % 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.

Coffee Sand (Cretaceous) at surface, covers 0.2 % of this area

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

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.