Geologic units in Saint John the Baptist Parish, Louisiana

Natural Levees (Phanerozoic | Cenozoic | Quaternary | Holocene) at surface, covers 17 % of this area: gray and brown silt, silty clay, some very fine sand, reddish brown along the Red River.
Lithology: silt; clay or mud; sand
Alluvium (Phanerozoic | Cenozoic | Quaternary | Holocene) at surface, covers 38 % of this area: gray to brownish gray clay and silty clay, reddish brown in the Red River Valley, some sand and gravel locally.
Lithology: clay or mud; sand; gravel
Delta Plain, Fresh Marsh (Phanerozoic | Cenozoic | Quaternary | Holocene) at surface, covers 8 % of this area: gray to black clay of very high organic content, some peat.
Lithology: clay or mud; peat