Geologic units in Twiggs county, Georgia

Twiggs Clay (Eocene) at surface, covers 34 % of this area

Twiggs Clay

Lower Tertiary-Cretaceous undifferentiated (Lower Tertiary-Cretaceous) at surface, covers 15 % of this area

As mapped includes Middendorf Formation (Sloan, 1904); "Channel Sands" (LaMoreaux, 1946); Tuscaloosa Formation (Cooke, 1939); and "Huber beds" (Buie, informal terminology)

Irwinton Sand (Eocene) at surface, covers 14 % of this area

Up-dip equivalent of Twiggs Clay, Sandersville Limestone, and Cooper Marl. As mapped, also includes younger clastics of indefinite Late Tertiary age.

Suwannee Limestone and its residuum (Oligocene) at surface, covers 11 % of this area

As mapped, includes Chattahoochee Limestone in Seminole and Decatur Cos.; Flint River Formation, in part, (Cooke, 1939); Jacksonboro Limestone in Screven Co.; and Glendon and Marianna Limestones in Pulaski Co.

Ocala Limestone (Eocene) at surface, covers 11 % of this area

Generally covered with Oligocene and Eocene residuum (Flint River Formation of Cooke, 1939); includes up-dip area, Tivola Limestone of Connell (1955). (*)- outcrops of Ocala Limestone on Dougherty Plain.

Stream alluvium (Quaternary) at surface, covers 9 % of this area

Stream alluvium and undifferentiated terrace deposits

Neogene undifferentiated (Neogene) at surface, covers 5 % of this area

Includes Altamaha Grit (Dall, 1892); Citronelle Formation (Matson & Berry, 1916); and "Hawthorn Formation" (Cooke, 1939). (*) - outcrops of indurated sandstone and claystone

Providence Sand (Cretaceous) at surface, covers < 0.1 % of this area

Providence Sand, includes Perote Member