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WEARY, David J.,
U.S. Geol Survey, MS 926A, Reston, VA 20192, dweary@usgs.gov, DOCTOR, Daniel
H., U.S. Geol. Survey, MS 926A, Reston, VA 20192, ORNDORFF, Randall C., U.S.
Geol. Survey, MS 908, Reston, VA 20192, and HARLOW, George E. Jr, U.S. Geol Survey, 1730 East Parham Road, Richmond, VA
23228
New and revised detailed geologic mapping by the U.S. Geological
Survey in the Paleozoic carbonate rocks of the northern Shenandoah Valley of
Virginia and West Virginia
is providing a geologic framework with sufficient spatial resolution for
testing correlation of ground-water flow paths to geologic setting. Thrust
faults, cross faults, and major folds in the valley serve as directional
controls on ground-water flow, and combined with lithologic
units produce physical compartments for ground-water storage and flow.
Strike-parallel ground-water flow is interrupted by compartment-bounding
cross faults that may either direct water across strike or force flow towards
the surface, often producing springs. Flow-paths are complex and the
compartments are leaky. Support for these ideas include: 1) results of
multidisciplinary hydrogeologic studies at the U.S. Geological Survey,
Leetown, WV Science Center which indicate strong anisotropy in ground-water
flow directions and correlation between test-well transmissivity and geologic
structures, including folds and faults; 2) New geologic mapping in the
Middletown, Winchester, Stephens City, Stephenson, Inwood, and White Hall
1:24,000 quadrangles suggests that spring location, magnitude, and geographic
spacing is positively correlated with the location of thrust, diagonal, and cross
faults; 3) the density of sinkholes and closed depressions located within
large (several km scale) synclines that indicate zones of focused
ground-water recharge. Two synclines of note are the Buffalo Marsh Run
syncline situated in the Middletown quadrangle
and the Welltown syncline situated in the Winchester, White Hall
and Inwood quadrangles.
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