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Geology topics

Gary M. Fleeger

Publications and source records attributed to Gary M. Fleeger.

2 recordsLinked to original sources

A multiagency and multijurisdictional approach to mapping the glacial deposits of the Great Lakes region in three dimensions

The Great Lakes Geologic Mapping Coalition (GLGMC), consisting of state geological surveys from all eight Great Lakes states, the Ontario Geological Survey, and the U.S. Geological Survey, was conceived out of a societal need for unbiased and scientifically defensible geologic information on the shallow subsurface, particularly the delineation, interpretation, and viability of groundwater resources. Only a small percentage (<10%) of the region had been mapped in the subsurface, and there was recognition that no single agency had the financial, intellectual, or physical resources to conduct such a massive geologic mapping effort at a detailed scale over a wide jurisdiction. The GLGMC provides a strategy for generating financial and stakeholder support for three-dimensional (3-D) geologic mapping, pooling of physical and personnel resources, and sharing of mapping and technological expertise to characterize the thick cover of glacial sediments. Since its inception in 1997, the GLGMC partners have conducted detailed surficial and 3-D geologic mapping within all jurisdictions, and concurrent significant scientific advancements have been made to increase understanding of the history and framework of geologic processes. More importantly, scientific information has been provided to public policymakers in understandable formats, emphasis has been placed on training early-career scientists in new mapping techniques and emerging technologies, and a successful model has been developed of state/provincial and federal collaboration focused on geologic mapping, as evidenced by this program's unprecedented and long-term successful experiment of 10 geological surveys working together to address common issues.

GSA Special Papers

Hydrologic effects of the Pymatuning earthquake of September 25, 1998, in northwestern Pennsylvania

Within hours after the Pymatuning earthquake of September 25, 1998, in northwestern Pennsylvania, local residents reported wells becoming dry, wells beginning to flow, and the formation of new springs. About 120 household-supply wells reportedly went dry within 3 months after the earthquake. About 80 of these wells were on a ridge between Jamestown and Greenville, where water-level declines of as much as 100 feet were documented. Accompanying the decline in water levels beneath the ridge was an increase in water levels in valley wells of as much as 62 feet. One possible explanation of the observed hydrologic effects is that the earthquake increased the vertical hydraulic conductivity of shales beneath the ridge, which allowed ground water to drain from the hilltops. Computer simulations of ground-water flow beneath the ridge between Jamestown and Greenville indicate that increasing the vertical hydraulic conductivity of shale confining beds about 10 to 60 times from their pre-quake values could cause the general pattern of decreased water levels on hilltops and increased levels in valleys.

Pennsylvania