Geologic units in Winn Parish, Louisiana

Additional scientific data in this geographic area

Cockfield Formation (Eocene) at surface, covers 32 % of this area

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

Prairie Terraces (Pleistocene) at surface, covers 20 % of this area

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

Alluvium (Holocene) at surface, covers 19 % of this area

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

Cook Mountain Formation (Eocene) at surface, covers 7 % 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.

High Terraces (Pleistocene) at surface, covers 7 % of this area

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

Sparta Formation (Eocene) at surface, covers 7 % of this area

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

Intermediate Terraces (Pleistocene) at surface, covers 5 % of this area

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

Jackson Group (undifferentiated) (Eocene) at surface, covers 2 % of this area

Light gray to brown liginitic clays with thin interbeds of limonitic sands or lignite; near base,calcareous, glauconitic, and fossiliferous beds may weather to black soil.

Natural Levees (Holocene) at surface, covers 0.7 % of this area

Gray and brown silt, silty clay, some very fine sand, reddish brown along the Red River.