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Mineral Resources > Online Spatial Data > Geology > by state > South Carolina Geology

Geologic units in Charleston county, South Carolina

Chenier plain and deltas of Suwannee & Chattahoochie Rivers (Holocene) at surface, covers 30 % of this area

Chenier plain and deltas of Suwannee & Chattahoochie Rivers

Lithology: unconsolidated deposit

Swamp (Quaternary) at surface, covers 10 % of this area

Swamp: Extensive cypress swamps occur in low-lying poorly-drained bay deposits. Limit of cypress is southern Delaware; from NJ south to Georgia. Atlantic white cedar is original species. Commonly extensive thick peat and buried wood.

Lithology: peat

Wando Formation (Pleistocene) at surface, covers 17 % of this area

Wando Formation: Another Carolina coastal terrace sequence like Penholoway . This is the youngest and lowest. Late Pleistocene

Lithology: clay or mud; sand

Tidal Marsh (Quaternary) at surface, covers 21 % of this area

Tidal Marsh: Peat and muck deposits along tidal margins of esturaries and back bays. Deposits range from a few feet to 60+ feet deep. Locally include silt and fine sand and clay as levees on tidal channels. At depth peaty material may be accumulated from fresh water plants. Peat at the surface dominated by spartina and other salt tolerant species.

Lithology: peat; silt; sand; clay or mud

Beach (Holocene) at surface, covers 4 % of this area

Beach: Holocene beach complex sediments. Sands and gravels of littoral zone, dune system, barrier system.

Lithology: sand; gravel

Penholoway Formation (Pleistocene) at surface, covers 1.0 % of this area

Penholoway Formation: 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.

Lithology: sand; clay or mud

Socastee Formation (Pleistocene) at surface, covers 14 % of this area

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

Lithology: sand; clay or mud

Alluvial Valley Swamp (Quaternary) at surface, covers 0.6 % of this area

Alluvial Valley Swamp: 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.

Lithology: sand; gravel; silt; peat