Geologic units in Madison county, Mississippi

Jackson group (Eocene) at surface, covers 59 % of this area

Yazoo clay, green and gray calcareous clay containing some sand and marl; Moodys Branch formation at base, shells embedded in glauconitic clayey quartz sand.

Cockfield (Eocene) at surface, covers 39 % of this area

(Claiborne group), Irregularly bedded, more or less laminated liginitic clay, sand, and lignite; sparingly glauconitic.

Forest Hill formation and Red Bluff clay (Oligocene) at surface, covers 2 % of this area

Forest Hill sand, cross-bedded fine gray sand, laminated fine sand and clay, and a little lignite; in Wayne and Clarke Counties lower part merges eastward into Red Bluff clay, blue-green glauconitic, gypsiferous, fossiliferous clay and thin limestone beds.

Cook Mountain formation (Eocene) at surface, covers 0.7 % of this area

(Claiborne group), Southeast of Pearl River, marl, limestone, glauconitic sand, and chocolate-colored clay; northwest of Pearl River, predominantly chocolate-colored clay with some glauconitic sand.

Vicksburg group and Chickasawhay limestone (Oligocene) at surface, covers 0.3 % of this area

Chickasawhay limestone, sandy limestone, and sand, present only in eastern MS (mapped with it is the overlying Paynes Hammock sand of Miocene age); Vicksburg group, predominantly limestone and marl, but contains some bentonite and near the top, chocolate-colored clay and some sand.