A collaborative bedrock/surficial deposit mapping project between Miami University and the Ohio Department of Natural Resources (ODNR), Division of Geological Survey has resulted in the generation of a revised bedrock topography map for the Oxford and College Corner 7.5-minute quadrangles, Butler and Preble counties, southwest Ohio. The study area consists of glaciated uplands dissected by filled valleys of the Indian Creek, Four-Mile Creek, and Seven-Mile Creek drainages. The primary objective of the study was to better delineate the thickness of Quaternary deposits in the study area. These deposits, which range in thickness from 0 to >200 ft, serve as the primary municipal and private drinking water resource for northern Butler County and southern Preble counties.
Building on mapping conducted by ODNR in the 1990s, the present study utilized water-well and borehole log data available on-line through the ODNR Division of Water Resources and the Ohio Department of Transportation. Additional Quaternary thickness and depth-to-bedrock data were derived from municipal water-supply and monitoring well logs drilled by the City of Oxford and Miami University. The study also incorporated field mapping of exposures of the Quaternary-Paleozoic contact as well as horizontal-to-vertical spectral ratio (HVSR) passive seismic analysis. HVSR data were calibrated at recording stations adjacent to wells with bedrock penetrations.
Study results generated over 1550 individual elevation points of the Quaternary-Paleozoic contact, more than 3x the number used in earlier mapping efforts. The resulting higher resolution contour map of the bedrock topography indicates valley-fill deposits in some parts of the study area are narrower but deeper than previously mapped, and thus likely contain steeper basal contacts with underlying Paleozoic rocks. As valley-fill deposits serve as the primary municipal aquifers in the study area, these findings may have important implications for the future development and utilization of local groundwater resources.
Authors: Blake Stubbins, Emma Palko, Rosamiel Ries, Ellie Knutson
Faculty Advisor: Brian Currie, Department of Geology & Environmental Earth Science
Additional: Haley Thoresen, Seth Swearingen, Emmanuel Adedugbe, Jonathan Levy, Thomas A. Nash, and Daniel Blake
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