Geologic units in Columbus county, North Carolina

Peedee Formation (Cretaceous) at surface, covers 65 % of this area

Sand, clayey sand, and clay, greenish gray to olive black, massive, glauconitic, locally fossiliferous and calcareous. Patches of sandy molluscan-mold limestone in upper part.

Yorktown Formation and Duplin Formation, Undivided (Tertiary) at surface, covers 25 % of this area

Yorktown Formation: fossiliferous clay with varying amounts of fine-grained sand, bluish gray, shell material commonly concentrated in lenses; mainly in area north of Neuse River. Duplin Formation: shelly, medium- to coarse-grained sand, sandy marl, and limestone, bluish gray; mainly in area south of Neuse River.

Waccamaw Formation (Tertiary) at surface, covers 10 % of this area

Fossiliferous sand with silt and clay, bluish-gray to tan, loosely consolidated. Straddles Pleistocene-Pliocene boundary.

Black Creek Formation (Cretaceous) at surface, covers 0.1 % of this area

Clay, gray to black, lignitic; contains thin beds and laminae of fine-grained micaceous sand and thick lenses of cross-bedded sand. Glauconitic, fossiliferous clayey sand lenses in upper part.

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.