Geologic units in Saint Tammany Parish, Louisiana

Prairie Terraces (Pleistocene) at surface, covers 49 % of this area

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

Alluvium (Holocene) at surface, covers 24 % 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 17 % of this area

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

Delta Plain, Saline Marsh (Holocene) at surface, covers 4 % of this area

Gray to black clay of very high organic content, some peat.

Delta Plain, Fresh Marsh (Holocene) at surface, covers 4 % of this area

Gray to black clay of very high organic content, some peat.

Deweyville Terrace (Pleistocene) at surface, covers 0.7 % of this area

Gray mixed with brown-to-red clay and silty clay; some sand and gravel locally.

Coastal deposits (Holocene) at surface, covers 0.2 % of this area

Loam, sand, gravel and clay.