Date of Graduation

1980

Document Type

Thesis

Abstract

The study area covers approximately 80 square miles of the outcrop extent of the Middle Mississippian Greenbrier Group in central Greenbrier County, West Virginia. This sequence of sedimentary rocks, primarily limestones, is approximately 800 feet thick, strikes about N25(DEGREES)E, and generally dips less than 10 degrees to the northwest. The study area is predominated by broad, asymmetric, and northeast-trending folds of low plunge, and several roughly en echelon reverse faulty-fold complexes. A major photolineament trend exists at N30(DEGREES)E to N45(DEGREES)E. Areas of high photolineament density roughly correspond to mapped structures. Three major aquifers were identified in the Greenbrier Group by way of inventorying and sampling 74 water wells during the period from September 1977 to July 1978. The Maccrady-Hillsdale aquifer, confined at the base of the Greenbrier Group, is ordinarily an adequate and reliable supplier of ground water. However, wells pumping from this aquifer are somewhat expensive because of the great depth to this zone. The Taggard aquifer is associated with the red shales of the Taggard Formation near the center of the carbonate stratigraphic column. It is the least reliable and lowest yielding aquifer. Where the Pickaway-Union aquifer exists, it is the highest-producing of the three. The water in this aquifer is associated with the shaley strata of the upper Pickaway Limestone and is not confined. Flow movement within the aquifers is believed to parallel stratigraphic strike. Ground-water discharge occurs at large baselevel springs and from well springs. Wells with a high-yield-to-depth ratio are in an area of high photolineament density, although eight wells located within 100 feet of photolineaments did not show significantly higher yields than other wells. Statistical tests also show that well yield increases with increasing stratigraphic dip (up to 30 degrees) as well as away from the axial traces of folds or faults. Well yield is not significantly influenced by surface topography in the study area. Well waters of the study area are of a very hard calcium-magnesium-bicarbonate type, although in some well waters, sulfate, chloride, or sodium are also important. In eight wells, water containing unusually high sulfate concentrations are believed to be contaminated from dissolution of gypsum and pyrite in the strata. Slight increases in pH, saturation indices for calcite and dolomite, conductivity, chloride concentration, and a decrease of temperature and carbon dioxide partial pressure were found to occur in well waters during the winter of 1977-1978. Compared to the other aquifers, well waters of the Maccrady-Hillsdale aquifer seem to be most influenced by the presence of dolomite, sulfur-bearing minerals, and the cation-exchange properties of the shales in the Maccrady Formation. The Maccrady-Hillsdale well waters are also least influenced by contamination from surface pollution sources, such as road salts or septic tanks. Comparison of the chemical qualities of the well water to that of Davis Spring showed the well water to be much more concentrated in many ions, probably because of its slower, diffuse flow. R-mode factor analysis of the water chemistry variables showed the importance of carbon dioxide partial pressure to the degree of carbonate saturation. The factor analysis showed the existence of conductivity, dolomite dissolution, water pollution, and water temperature factors.

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