Geologic units in Dunklin county, Missouri

Holocene series (Quaternary-Holocene Series) at surface, covers 95 % of this area

Alluvium - clay, silt, sand, and gravel.

Tertiary system (Tertiary-Late-Pliocene to Paleocene) at surface, covers 4 % of this area

Pliocene series - Mounds Gravel (Lafayette Formation) - ferruginous, chert gravel, max of 60 ft. Eocene series - Wilcox group - includes Holly Springs Formation - bedded sandstone, clay and gravel, max of 1200 ft.; Ackerman Formation - clay with lens of sand and gravel, max of 100ft. Paleocene series - Midway Group - includes Porters Creek Clay - bentonitic clay, max of 200 ft.; Clayton Formation - marl, fossiliferous, calcareous, limonitic, glauconitic sand and clay, max of 20 ft.

Alluvium - Alluvial deposits of local streams or of overbank flow of major streams (Holocene) at surface, covers 0.4 % of this area

Alluvial deposits of local streams or of overbank flow of major streams - In some areas includes deposits in abandoned meanders of major streams

Terrace deposits (Late Pleistocene) at surface, covers < 0.1 % of this area

Alluvial deposits on one or more terrace levels

Silt and sand (Early Pleistocene) at surface, covers < 0.1 % of this area

Contains lenses of gravel and clay