Geologic units in Grant Parish, Louisiana

Additional scientific data in this geographic area

High Terraces (Pleistocene) at surface, covers 35 % of this area

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

Alluvium (Holocene) at surface, covers 20 % of this area

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

Prairie Terraces (Pleistocene) at surface, covers 13 % of this area

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

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

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

Natural Levees (Holocene) at surface, covers 8 % of this area

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

Catahoula Formation (Oligocene) at surface, covers 5 % of this area

Gray to white sandstones; loose quartz sand, tuffaceous sandstone, volcanic ash, and brown sandy clays; petrified wood locally.

Jackson Group (undifferentiated) (Eocene) at surface, covers 4 % 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.

Vicksburg Group (undifferentiated) (Oligocene) at surface, covers 4 % of this area

Brown to gray liginitic clays with thin interbeds of lignite or micaceous sands; calcareous shale, petrified wood, and bluish fossilferous clay locally.

Carnahan Bayou Member (Miocene) at surface, covers 0.8 % of this area

Yellow to gray siltstones, sandstones, and clays with thin tuffaceous beds; some lenses of black chert gravel; petrified wood locally.

Lena Member (Miocene) at surface, covers 0.3 % of this area

Gray calcareous clays which may weather to black soil; siltstone, taffaceous clays and some volcanic ash beds

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.