Geologic units in Washington county, Georgia

Irwinton Sand (Eocene) at surface, covers 34 % 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.

Neogene undifferentiated (Neogene) at surface, covers 34 % 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 17 % of this area

Twiggs Clay

Lower Tertiary-Cretaceous undifferentiated (Lower Tertiary-Cretaceous) at surface, covers 11 % of this area

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

Stream alluvium (Quaternary) at surface, covers 3 % of this area

Stream alluvium and undifferentiated terrace deposits

Undifferentiated Metavolcanics/ Sericite phyllite/ Meta-argillite/ Quartz mica schist (Precambrian-Paleozoic) at surface, covers 0.6 % of this area

Undifferentiated Metavolcanics/ Sericite phyllite/ Meta-argillite/ Quartz mica schist

Sandersville Limestone (Eocene) at surface, covers 0.2 % of this area

Sandersville Limestone

Granite undifferentiated (Precambrian-Paleozoic) at surface, covers < 0.1 % of this area

Granite undifferentiated