Geologic units in Rapides Parish, Louisiana

Additional scientific data in this geographic area

Alluvium (Holocene) at surface, covers 28 % of this area

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

High Terraces (Pleistocene) at surface, covers 26 % of this area

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

Natural Levees (Holocene) at surface, covers 15 % of this area

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

Prairie Terraces (Pleistocene) at surface, covers 11 % of this area

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

Intermediate Terraces (Pleistocene) at surface, covers 9 % of this area

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

Carnahan Bayou Member (Miocene) at surface, covers 4 % of this area

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

Williamson Creek Member (Miocene) at surface, covers 2 % of this area

White to gray silts, siltstones, silty clays, and sand beds; some lenses of black chert gravel.

Intermediate Terraces (Pleistocene) at surface, covers 1 % of this area

Light gray to orange-brown clay, sandy clay, and silt; much sand and gravel locally. Overlain by 1-9 meters of loess.

Dough Hills Member (Miocene) at surface, covers 1 % of this area

Gray to yellow silty clays; light gray calcareous clays which may weather to black soil; some siliceous silt and volcanic ash beds.

Braided Stream Terraces (Pleistocene) at surface, covers 0.5 % of this area

Light gray, tan and brown fine to coarse sand; some clay silt and gravel.

High Terraces (Pleistocene) at surface, covers 0.3 % of this area

Tan to orange clay, silt, and sand with a large amount of basal gravels. Overlain by 1-9 meters of loess.

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

Gray to dark gray calcareous clays which may weather to black soil; lignitic clays and noncalcreous clayey silts

Blounts Creek Member (Pliocene to Miocene) at surface, covers 0.2 % of this area

Gray to green silty clays, siltstones, and silts with abundant sand beds; some lignite and lenses of black chert gravel.

Lena Member (Miocene) at surface, covers 0.2 % of this area

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

Catahoula Formation (Oligocene) at surface, covers 0.1 % of this area

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

Prairie Terraces (Pleistocene) at surface, covers < 0.1 % of this area

Light gray to light brown clay, sandy clay, silt, sand, and some gravels. Overlain by 1-9 meters of loess.