Geologic units in Jefferson county, Georgia

Irwinton Sand (Eocene) at surface, covers 36 % 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.

Twiggs Clay (Eocene) at surface, covers 29 % of this area

Twiggs Clay

Neogene undifferentiated (Neogene) at surface, covers 28 % of this area

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

Lower Tertiary-Cretaceous undifferentiated (Lower Tertiary-Cretaceous) at surface, covers 7 % of this area

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