2006. 2012-01-13T19:48:51Z. 2012-03-05T17:33:06Z. Ryder, Robert T. U.S. Geological Survey ; For sale by U.S. Geological Survey, Information Services. English. Public. Appalachian Basin, Ohio, West Virginia, Appalachian Basin., Ohio., and West Virginia. Silurian.
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1948. 2018-01-30T14:30:37Z. 2018-01-30T14:30:37Z. Cohee, George Vincent, 1907-. U.S. Geological Survey. English. cartographic image. Public. Michigan Basin (Mich. and Ont.), North America, and Michigan Basin. Ordovician, Silurian, and From 405 to 500 million years ago.