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to the Sheriden Cave ProjectThe geology of the study area involves the Lockport Dolomite with very shallow (generally less than 1 meter) soil. Numerous karst features are reported on this ridge. Anecdotal reports of water well drillers hitting 3 levels of caverns suggest the karst development is pervasive, but obvious surface manifestations are rare. Potential geophysical targets include sediment-filled sinkholes and caverns (sediments should exhibit electrical resistivities higher than those characteristic of dolomite, seismic wave velocities lower than those characteristic of dolomite, and a lower density than that of dolomite; open air-filled caverns should exhibit very high electrical resistivities and even lower densities; water-filled caverns may reveal themselves by their very low electrical resistivities but will probably not be of much interest to archaeology students).
We are limited to the tools available (see http://www.geology.utoledo.edu/geophysics/instrs.html for a list). Reconnaissance - using instruments that cover a lot of ground but lacking high resolution - is our first step. The Geonics EM34-3XL will be used to gather apparent ground conductivity (electrical conductivity) along profiles extending across known caves and into fields around the Hendricks Cave and Sheriden Cave. Electrical resistivity will be used to more closely examine locations selected based on EM34 results. Seismic fan shots are planned - delays should occur where seismic ray paths are interrupted by sinkholes. Precision gravity measurements (using a borrowed "G" meter) may yield information needed to calculate the size of a sediment-filled sinkhole. Magnetometer surveys will also be run in search of fire pits used by later prehistoric residents of the ridge. Current residents report finding numerous flakes and spear points in the area.
Archaeological applications of some geophysical methods will be the focus of a field methods class planned for May - June of 1998. Contact Dr. Don Stierman for details.