Geologic units in Saint Helena Parish, Louisiana

High Terraces (Pleistocene) at surface, covers 65 % of this area

Tan to orange clay, silt, and sand with a large amount of basal gravels.

Alluvium (Holocene) at surface, covers 26 % of this area

Gray to brownish gray clay and silty clay, reddish brown in the Red River Valley, some sand and gravel locally.

Intermediate Terraces (Pleistocene) at surface, covers 6 % of this area

Light gray to orange-brown clay, sandy clay, and silt; much sand and gravel locally.

Prairie Terraces (Pleistocene) at surface, covers 3 % of this area

Light gray to light brown clay, sandy clay, silt, sand, and some gravels.

Citronelle formation (Pleistocene) at surface, covers < 0.1 % of this area

Red sand and gravel and white clay; may be of Pliocene age; the formation mapped is equivalent to the Willis sand and does not include the terrace deposits, colluvium, and residuum commonly considered "Citronelle".