Geologic units in Burke county, Georgia

Neogene undifferentiated (Neogene) at surface, covers 52 % of this area

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

Irwinton Sand (Eocene) at surface, covers 24 % 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 19 % of this area

Twiggs Clay

Stream alluvium (Quaternary) at surface, covers 1 % of this area

Stream alluvium and undifferentiated terrace deposits

McBean Formation (Eocene) at surface, covers 1 % of this area

McBean Formation

Cooper Marl (Eocene) at surface, covers 1 % 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).

Lower Tertiary-Cretaceous undifferentiated (Lower Tertiary-Cretaceous) at surface, covers 1 % of this area

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

Alluvial Valley Swamp (Quaternary) at surface, covers 0.1 % of this area

Unconformable on all underlying units, fluvial sand and gravel at base, grading upwards into fine sands and silts, local peat. May be overrun with recent sediments from forest cutting and agriculture.

Socastee Formation (Pleistocene) at surface, covers < 0.1 % of this area

Low coastal formation in Carolinas like Penholoway but younger and lower in altitude.

Penholoway Formation (Pleistocene) at surface, covers < 0.1 % of this area

Similar to Cape May, broad lateral extent underlying terraces in the Carolinas; swamps and ridges on terrace surface were originally barrier islands and back bays. Superimposed on these landforms are swarms of Carolina bays.