The aquifers underlying a 44,000-square-mile area in western Ohio, eastern and north-central Indiana, and parts of Illinois and Michigan consist of carbonate bedrock of Silurian and Devonian age and glacial deposits of Quaternary age. Regionally, the top of the bedrock aquifer can be defined by the altitude of the bedrock-surface in areas where the aquifer units crop out. The bedrock-surface altitude ranges from 400 feet above sea level within the main stem of the Miami River Valley system in southwest Ohio to 1400 feet above sea level near Indian Lake in central Ohio. A major contributor to the features of the bedrock-surface was the pre-Pleistocene Teays-Mahomet River system.
Additional publication details
USGS Numbered Series
Bedrock-surface altitude in the midwestern basins and arches region of Indiana, Ohio, Michigan, and Illinois
Water-Resources Investigations Report
1 map ; 69 x 82 cm., on sheet 105 x 135 cm., folded in envelope 30 x 24 cm.