Geologic units in Saint John the Baptist Parish, Louisiana

Alluvium (Holocene) at surface, covers 60 % of this area

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

Natural Levees (Holocene) at surface, covers 27 % of this area

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

Delta Plain, Fresh Marsh (Holocene) at surface, covers 13 % of this area

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