1. Regional bedrock geology of the Bellefontaine, Ohio 30 x 60 minute quadrangle Yale Public content 1995. 2008-11-11T14:59:59Z. 2011-03-28T23:37:56Z. Swinford, E. Mac. Ohio Dept. of Natural Resources, Division of Geological Survey. English. Public. Ohio and Bellefontaine Region. Ordovician, Silurian, and Quaternary.