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Mineral Resources > Online Spatial Data > Geology > by state > Maryland Geology

Geologic units in Caroline county, Maryland

Quaternary Deposits Undivided (Quaternary) at surface, covers 18 % of this area

Quaternary Deposits Undivided - Undifferentiated gray to buff sand and gravel, gray to brown lignitic silt and clay, occasional boulders, and rare shell beds. Surficial deposits occur as intercalated fluvial sands and marsh muds (e.g. in upstream floodplain of the Wicomico and Nanticoke Rivers), well-sorted, stablized dune sands (e.g. eastern Wicomico County), shell-bearing estuarine clays and silts (e.g. lower Dorchester County) and Pocomoke River basin of Worcester County), and beach zone sands (e.g. Fenwick and Assateague Islands). Wisconsin to Holocene in age. Subsurface deposits of pre-Wisconsin age consist of buff to reddish-brown sand and gravel locally incised into Miocene sediments (e.g. Salisbury area), estuarine to marine white to gray sands, and gray to blue, shell-bearing clays (e.g. Worcester County).

Lithology: sand; gravel; silt; clay or mud; dune sand; beach sand

Upland Deposits (Eastern Shore) (Quaternary) at surface, covers 63 % of this area

Upland Deposits (Eastern Shore) - Gravel, sand, silt, and clay. Mostly cross-bedded, poorly sorted, medium- to coarse-grained white to red sand and gravel; boulders near base; minor pink and yellow silts and clays; (Wicomico Formation of earlier reports); thickness 0 to 90 feet, locally thicker in paleochannels.

Lithology: gravel; sand; silt; clay or mud

Chesapeake Group; Choptank Formation (Miocene) at surface, covers 8 % of this area

Chesapeake Group; Choptank Formation - Interbedded brown to yellow very fine-grained to fine-grained sand and gray to dark bluish-green argillaceous silt; locally indurated to calcareous sandstone; prominent shell beds; thickness 0 to 50 feet.

Lithology: sand; silt; sandstone; coquina

Lowland Deposits (Quaternary) at surface, covers 9 % of this area

Lowland Deposits - Gravel, sand, silt, and clay. Medium- to coarse-grained sand and gravel; cobbles and boulders near base; commonly contains reworked Eocene glauconite; varicolored silts and clays; brown to dark gray lignitic silty clay; contains estuarine to marine fauna in some areas (includes in part Pamlico, Talbot, Wicomico and Sunderland Formations of earlier reports); thickness 0 to 150 feet.

Lithology: gravel; sand; silt; clay or mud

Chesapeake Group (Tertiary) at surface, covers 0.3 % of this area

Chesapeake Group - Bluish gray silt with quartz sand and some shell beds.

Lithology: silt; sand

Chesapeake Group; Calvert Formation (Miocene) at surface, covers 2 % of this area

Chesapeake Group; Calvert Formation - Plum Point Marls Member: Interbedded dark green to dark bluish-gray, fine-grained argillaceous sand and sandy clay; contains prominent shell beds and locally silica-cemented sandstones; and Fairhaven Member: Greenish-blue diatomaceous clay, weathers to pale gray; pale brown to white, fine-grained argillaceous sand; and greenish-blue sandy clay; total thickness 0 to 150 feet.

Lithology: sand; clay or mud; sandstone