Preliminary delineation of salty ground water in
the northern Atlantic Coastal Plain
Open-File
Report 81-71
By Harold Meisler
Abstract
Salty ground water underlies freshwater in the eastern part of
the northern Atlantic Coastal Plain. The transition zone between
freshwater and saltwater is represented in this report by a
series of maps showing the depths to chloride concentrations of
250, 1,000, 10,000, and 18,000 milligrams per liter. The maps
are based on chloride concentrations obtained from
self-potential logs as well as from water-quality analyses.
Depths to the designated chloride concentrations generally
increase inland from the coast except in New Jersey where they
are greatest along the coast and in North Carolina where depths
to the 10,000 and 18,000 milligrams per liter concentrations are
greatest beneath Pamlico Sound. The transition zone between 250
and 18,000 milligrams per liter of chloride is generally 1,500
to 2,300 feet thick except in part of North Carolina, where it
is less than 1,000 feet. Depths to 250 and 1,000 milligrams per
liter of chloride are probably controlled by the natural flow
pattern of fresh ground water. Areas where these concentrations
are relatively shallow generally coincide with areas of natural
ground-water discharge. Depths to 10,000 and 18,000 milligrams
per liter of chloride, and the occurrence offshore of ground
water that is fresher than seawater, is attributed to long-term
hydrologic conditions during which sea level fluctuations of a
few hundred feet recurred several times. The origin of ground
water that is saltier than seawater is attributed to the
leaching of evaporitic strata beneath the Continental Shelf and
Slope followed by westward movement of the brines during periods
of sea-level rise.
Citation:
Meisler, Harold, 1981, Preliminary delineation of salty ground water in the northern Atlantic Coastal Plain: U.S. Geological Survey Open-File Report 81-71, 37 p.
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