Black Mingo/Clayton Formations: Poorly to well sorted sand and clay deposited in delta-dominated fluvial- and shallow marine environments. Older parts of unit are characterized by an abundance of feldspar and local sillimanite. Unit is generally delta plain and lagoon deposits in South Carolina becoming open marine calcareous sand and clay in western Georgia. In central Georgia, unit contains an abundance of commercial kaolin deposits formed in lower delta plain environments.
Huber/Lisbon/Barnwell Formations, undivided: Poorly to well sorted sand, clay and carbonates deposited in delta-dominated fluvial- and open-marine environments. Unit is characterized by commercial kaolin bodies in older strata from westernmost South Carolina to central Georgia. Younger strata are cyclic marine deposits which deeper water facies exposed in western Georgia. Carbonate facies are locally mined in western Georgia for agricultural lime.