Potomac Group, including Raritan and Patapsco Formations, Arundel Clay, and Patuxent Formation (MDKp;5)

Potomac Group - Interbedded quartzose gravels; protoquartzitic to orthoquartzitic argillaceous sands; and white, dark gray, and multicolored silts and clays; thickness 0 to 800 feet. Includes Raritan and Patapsco Formations - Gray, brown, and red variegated silts and clays; lenticular, cross-bedded, argillaceous, subrounded sands; minor gravels; thickness 0 to 400 feet; Arundel Clay - Dark gray and maroon lignitic clays; abundant siderite concretions; present only in Baltimore-Washington area; thickness 0 to 100 feet; and Patuxent Formation - White or light gray to orange-brown, moderately sorted, cross-bedded, argillaceous, angular sands and subrounded quartz gravels; silts and clays subordinate, predominantly pale gray; thickness 0 to 250 feet.

State	Maryland
Name	Potomac Group, including Raritan and Patapsco Formations, Arundel Clay, and Patuxent Formation
Geologic age	Cretaceous
Original map label	Kp
Primary rock type	gravel
Secondary rock type	sand
Other rock types	silt; clay or mud
Lithologic constituents	Major Unconsolidated > Coarse-detrital > Sand Minor Unconsolidated > Fine-detrital > Clay Unconsolidated > Fine-detrital > Silt Unconsolidated > Coarse-detrital > Gravel
Map references	Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.
Unit references	Cleaves, E.T., Edwards, J., Jr., Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000. Unpublished digital version of the Maryland state geologic map that was digitized by the USGS Water Resources Office in Towson, MD
Geographic coverage	Anne Arundel - Baltimore - Cecil - Charles - Harford - Howard - Kent - Montgomery - Prince George's - Baltimore