Geologic units in Richmond county, Georgia

Irwinton Sand (Eocene) at surface, covers 33 % 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.

Lower Tertiary-Cretaceous undifferentiated (Lower Tertiary-Cretaceous) at surface, covers 31 % 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 15 % of this area

Stream alluvium and undifferentiated terrace deposits

Twiggs Clay (Eocene) at surface, covers 15 % of this area

Twiggs Clay

Meta-argillite/ Phyllite (Precambrian-Paleozoic) at surface, covers 4 % of this area

Meta-argillite/ Phyllite

McBean Formation (Eocene) at surface, covers 0.6 % of this area

McBean Formation

Alluvial Valley Swamp (Quaternary) at surface, covers 0.3 % 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.

Felsic Metavolcanics (Precambrian-Paleozoic) at surface, covers 0.2 % of this area

Felsic Metavolcanics

Black Creek/Cusseta/Blufftown Formations (Cretaceous) at surface, covers < 0.1 % of this area

Moderately to poorly sorted sand and clay deposited in delta-dominated shallow marine environments. Unit is characterized by sands containing locally abundant (F-VC grained) tourmaline and (F-VC grained) muscovite with some monazite and garnet. Clay layers are also common and some lower delta plain deposits form commercial kaolin bodies. Generally very restricted marine in eastern Georgia becoming more open marine to the east and west.

Metavolcanic and metasedimentary rocks of Bel Air Belt (Ordovician to Neoproterozoic) at surface, covers < 0.1 % of this area

Metavolcanic and metasedimentary rocks of Bel Air Belt

Chenier plain and deltas of Suwannee & Chattahoochie Rivers (Holocene) at surface, covers < 0.1 % of this area

Chenier plain and deltas of Suwannee & Chattahoochie Rivers

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

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