Potomac Group, including Raritan and Patapsco Formations, Arundel Clay, and Patuxent Formation

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
Lithologic constituents
Major
Unconsolidated > Coarse-detrital > Sand
Minor
Unconsolidated > Fine-detrital > Silt
Unconsolidated > Coarse-detrital > Gravel
Unconsolidated > Fine-detrital > Clay
References

Cleaves, E.T., Edwards, J., Jr., and Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.

In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at http://www.mgs.md.gov/.

NGMDB product
Counties Anne Arundel - Baltimore - Cecil - Charles - Harford - Howard - Kent - Montgomery - Prince George's - Baltimore