Lower Potomac Group, Eastern Coastal Plain (05)

Comments on Geologic Parameters

05 Percent Shale:

A number of studies present cross sections that include geophysical logs (gamma ray, spontaneous potential, resistivity) that can be used to derive a semiquantitative estimate percent shale within the lower Potomac aquifer (Hansen, 1968; Brown and others, 1972; Cushing and others, 1973; Trapp and others, 1984). Anderson (1948) and Benson and others (1985) provided grain-size analysis results from cores that can also be used to evaluate percent shale within the lower Potomac aquifer. Otton and Mandle (1984) and Hansen (1984) provided information regarding distribution of shale within the Potomac Group, but their maps cover only a portion of the area of interest. Brown and others (1972) provided a percent-shale map of the lower Potomac stratigraphic interval that covers the entire area of interest, and this map is used for the GIS.

05 Map:

05 Reference:

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.

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.

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.

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.