Geologic units in Jenkins county, Georgia

Neogene undifferentiated (Neogene) at surface, covers 85 % of this area

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

Twiggs Clay (Eocene) at surface, covers 5 % of this area

Twiggs Clay

Stream alluvium (Quaternary) at surface, covers 5 % of this area

Stream alluvium and undifferentiated terrace deposits

Cooper Marl (Eocene) at surface, covers 4 % of this area

It is now recognized that this unit is not the precise lithologic or biostratigraphic equivalent of type Cooper Marl (Huddlestun, Marsalis & Pickering, 1974).

Irwinton Sand (Eocene) at surface, covers 0.2 % 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.