Geologic units in Webster Parish, Louisiana

Alluvium (Holocene) at surface, covers 27 % 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 25 % of this area

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

Cook Mountain Formation (Eocene) at surface, covers 22 % of this area

Greenish gray sideritic clay in upper part may weather to brown ironstone; yellow to brown clays and fossiliferous marl in lower part may weather to black soil. Ironstone concretions near base.

Prairie Terraces (Pleistocene) at surface, covers 12 % of this area

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

High Terraces (Pleistocene) at surface, covers 10 % of this area

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

Sparta Formation (Eocene) at surface, covers 3 % of this area

White to light gray massive sands with interbedded clays; some thin beds of lignite or lignitic sands and shales.

Cane River Formation (Eocene) at surface, covers 0.3 % of this area

Brown silty clay with basal glauconitic, fossiliferous silts which may weather to ironstone locally.

Cockfield Formation (Eocene) at surface, covers 0.2 % of this area

Brown lignitic clays, silts and sands; some sideritic glauconite may weather to brown ironstone in lower part.

Wilcox Group (undifferentiated) (Paleocene) at surface, covers 0.1 % of this area

Gray to brown lignitic sands and silty to sandy lignitic clays, many seams of lignite; some limestone and glauconite.

Claibourne Group (Middle Eocene) at surface, covers < 0.1 % of this area

Claibourne Group

Alluvium (Holocene) at surface, covers < 0.1 % of this area

Alluvial deposits of present streams

Terrace deposits (Late Pleistocene) at surface, covers < 0.1 % of this area

Alluvial deposits on one or more terrace levels