Lower Potomac Group, Eastern Coastal Plain

Maryland, Delaware, and New Jersey

General Setting

The north central Atlantic coastal plain, which includes eastern Maryland, Delaware, and New Jersey, consists of a seaward-dipping and seaward-thickening wedge of Cretaceous through Pleistocene sediments (Trapp and others, 1984; Olsson and others, 1988). Most stratigraphic units outcrop in belts generally parallel to the coast, where they receive precipitation, which then infiltrates and flows downdip to become ground water. Eastern Maryland, Delaware and New Jersey receive abundant rainfall, and a number of the shallow aquifers provide ample domestic and industrial water.

Information Search and Selection

The deeper portions of the eastern coastal plain are the focus of this investigation because this area contains strata that are sufficiently deep, porous and permeable, and hydraulically isolated from fresh-water aquifers to serve as potential CO2 sequestration targets. In addition, there are several major CO2 producers in this region (fig. 1). However, depth to basement in the region is variable and is generally shallow in northern New Jersey and becomes deep (>7,000 ft) in the Maryland coastal plain (Manheim and Horn, 1968; Brown and others, 1972). Hence, depth-to-basement limits areas within the north central Atlantic coastal plain where aquifers are sufficiently deep to be candidates for CO2 sequestration.

The deep subsurface of this area has only been moderately studied because shallow aquifers generally provide sufficient water. There is very little potential for hydrocarbon production along the northern Atlantic coastal plain, and the subsurface liquid waste disposal has been limited to shallow injection of secondarily treated wastewater (Maria Conicelli, U.S. Environmental Protection Agency, personal communication, 2000; Ching-Tzone Tienn, Maryland Department of the Environment, personal communication, 2000). However, a number of deep hydrocarbon exploration wells were drilled and analyzed, which provide valuable information on deep-aquifer properties (Anderson, 1948; Kasabach and Scudder, 1961; Maher and Applin, 1971; Trapp and others, 1984; Benson and others, 1985). A number of reports were generated to describe deep-aquifer properties as potential subsurface-waste disposal sites (Hansen, 1984). Regional aquifer analyses commonly include deeper horizons (Manheim and Horn, 1968; Brown and others, 1972; Trapp and Meisler, 1992).

Because the basement is relatively shallow in eastern New Jersey, Delaware and Maryland, the only regional candidate for CO2 sequestration is the Lower Cretaceous Group, which is widely recognized as a major aquifer system in the northern Atlantic coastal-plain horizons (Manheim and Horn, 1968; Brown and others, 1972; Trapp and Meisler, 1992). The Potomac Group directly overlies the igneous and metamorphic basement in most of the area of interest. However, there are some areas where the Potomac Group is underlain by sediments of Jurassic(?) age (Manheim and Horn, 1968; Brown and others, 1972). Several authors recognized an upper, middle, and lower Potomac aquifer (for example, Trapp and Meisler, 1992). The GIS is based on the lower Potomac aquifer. Although the GIS generally covers the eastern coastal plain of New Jersey, Delaware, and Maryland, eastern Maryland and southeasternmost Delaware appear to be especially suitable for CO2 sequestration: there are significant CO2 producers in the area (fig. 1), basement in that area is relatively deep, and there is a well-defined sandy unit, the Waste Gate Formation, in the lower Potomac Group (Hansen, 1984) that has good reservoir properties for sequestering CO2.


Anderson, J. L., 1948, Cretaceous and Tertiary subsurface geology: State of Maryland Board of Natural Resources, Bulletin 2, 456 p.

Benson, R. N., Jordan, R. R., and Spoljaric, N., 1985, Geological studies of Cretaceous and Tertiary section, test well Je32-04, central Delaware: Delaware Geological Survey Bulletin No. 17, 69 p., 3 plates.

Brown, P. M., Miller, J. A., and Swain, F. M., 1972, Structural and stratigraphic framework, and spatial distribution of permeability of the Atlantic coastal plain, North Carolina to New York: U.S. Geological Survey, Professional Paper 796, 79 p, 59 plates.

Cushing, E. M., Kantrowitz, I. H., and Taylor, K. R., 1973, Water resources of the Delmarva Peninsula: U.S. Geological Survey, Professional Paper 822, 58 p.

Gill, H. E., and Farlekas, G. M., 1969, Geohydrologic maps of the Potomac-Raritan-Magoth aquifer system in the New Jersey coastal plain: U.S. Geological Survey, Hydrologic Investigations Atlas HA-557, 2 sheets

Gill, H. E., Seabar, P. R., Vecchioli, J., and Anderson, H. R., 1963, Evaluation of geologic and hydrologic data from the test-drilling program at Island Beach State Park, N. J.: New Jersey Department of Conservation and Economic Development, Water Resources Circular 12, 25 p.

Hansen, H. J., 1968, Geophysical log cross-section network of the Cretaceous sediments of southern Maryland: Maryland Geological Survey Report of Investigation No. 7, 33 p.

___________ 1969, Depositional environments of subsurface Potomac Group in southern Maryland: American Association of Petroleum Geologists Bulletin, v. 53, p. 1923–1937.

___________ 1984, Hydrogeologic characteristics of the Waste Gate Formation, a new subsurface unit of the Potomac Group underlying the eastern Delmarva Peninsula: Maryland Geological Survey Information Circular 39, 22 p.

Kasabach, H. F., and Scudder, R. J., 1961, Deep wells of the New Jersey coastal plain: New Jersey Geological Survey Report GSR 3, 62 p.

Kinney, D. M., ed., 1976, Geothermal gradient map of North America: American Association of Petroleum Geologists and U.S. Geological Survey Publication G74014, 2 maps.

Leahy, P. P., and Martin, Mary, 1993, Geohydrology and simulation of ground-water flow in the Northern Atlantic Coastal Plain aquifer system: U.S. Geological Survey Professional Paper 1404-K, 81 p.

Leahy, P. P., Martin, M., and Meisler, H., 1986, Hydrogeologic definition of the northern Atlantic Coastal Plain Aquifer System based on regional simulation, in Vecchioli, J., and Johnson, A. I., eds., Regional aquifer systems of the United Stated aquifers of the Atlantic and Gulf Coastal Plain: American Water Resources Association, Monograph Series No. 9, Bethesda, MD, p. 7–24.

Maher, J. C., and Applin, E. R., 1971, Geologic framework and petroleum potential of the Atlantic coastal plain and continental shelf: U.S. Geological Survey Professional Paper 659, 98 p., 17 plates.

Manheim, F. T., and Horn, M. K., 1968, Composition of deeper subsurface waters along the Atlantic continental margin: Southeastern Geology, v. 9, p. 215–236.

Meisler, Harold, 1989, The occurrence and geochemistry of salty ground water in the northern Atlantic Coastal Plain: U.S. Geological Survey Professional Paper P 1404-D, p. D1–D51.

Meisler, H., Leahy, P. P., and Knobel, L. L., 1984, Effect of eustatic sea-level changes on salt-water-freshwater in the northern Atlantic coastal plain: U.S. Geological Survey Water-Supply Paper 2255, 28 p.

National Imagery and Mapping Agency, 2000, Digital terrain elevation data (DTED Level 0)

Olsson, R. K., Gibson, T. G., Hansen, J. J., and Owens, J. P., 1988, Geology of the Atlantic coastal plain: Long Island to Virginia, in The geology of North America, v. 1-2, the Atlantic continental margin: Geological Society of America, p. 87–105.

Otton, E. G., and Mandle, R. J., 1984, Hydrogeology of the upper Chesapeake Bay area, Maryland with emphasis on aquifers in the Potomac Group: Maryland Geological Survey Report of Investigations No. 39, 62 p.

Pope, D. A., and Gordon, A. D., 1999, Simulation of ground-water flow and movement of the freshwater-saltwater interface in the New Jersey coastal plain: U.S. Geological Survey Water-Resources Investigations Report 98-4216, 159 p.

Richards, H. G. 1974, Structural and stratigraphic framework of the Atlantic coastal plain, in Oaks, R. Q., Jr., and DuBar, J. R., eds., Post-Miocene stratigraphy, central and southern Atlantic coastal plain: Logan UT, Utah State University Press, p. 11–19.

Trapp, H., Jr., 1992, Hydrogeologic framework of the northern Atlantic coastal plain in parts of North Carolina, Virginia, Maryland, Delaware, New Jersey, and New York: U.S. Geological Survey Professional Paper 1404-G, 59 p., 13 plates.

Trapp, H., Jr., and Horn, M. A., 1997, Ground water atlas of the United States—segment 11, Delaware, Maryland, New Jersey, North Carolina, Pennsylvania, Virginia, West Virginia: U.S. Geological Survey Hydrologic Investigations, Atlas No. HA-730-L, 30 p.

Trapp, H., Jr., Knobel, L. L., Meisler, H., and Leahy, P. P., 1984, Test well DO-CE 88 at Cambridge, Dorchester County, Maryland: U.S. Geological Survey, Water-Supply Paper 2229, 48 p.

Trapp, H., Jr., and Meisler, H., 1992, The regional aquifer underlying the northern Atlantic coastal plain in parts of North Carolina, Virginia, Maryland, Delaware, New Jersey, and New York—summary: U.S. Geological Survey, Professional Paper 1404A, 33 p., 11 plates.

Prepared by Andrew Warne.

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