Claibourne Group
(Middle Eocene) at surface, covers 74 % of this area Claibourne Group
Alluvium
(Holocene) at surface, covers 26 % of this area Alluvial deposits of present streams
Terrace deposits
(Late Pleistocene) at surface, covers 0.4 % of this area Alluvial deposits on one or more terrace levels
Cockfield Formation
(Eocene) at surface, covers < 0.1 % of this area Brown lignitic clays, silts and sands; some sideritic glauconite may weather to brown ironstone in lower part.
Alluvium
(Holocene) at surface, covers < 0.1 % of this area Gray to brownish gray clay and silty clay, reddish brown in the Red River Valley, some sand and gravel locally.
