Subject: Ordovician Geologic Period - Yale University Library GeoBlacklight Search Results

1. Sections and maps of Lower Ordovician and Cambrian rocks in the Michigan Basin, Michigan and adjoining areas

1945. 2018-02-20T15:02:08Z. 2018-02-20T15:02:08Z. Cohee, George Vincent, 1907-. U.S. Geological Survey. English. cartographic image. Public. Michigan Basin (Mich. and Ont.), North America, and Michigan Basin. Ordovician, Cambrian, and From 425 to 570 million years ago.

2. The Maquoketa Formation (Upper Ordovician) in Iowa [cartographic material]

1971. 2018-04-20T18:43:31Z. 2021-05-04T22:29:48Z. Parker, Mary Combs. Iowa Geological Survey. English. cartographic image. Public. Iowa and Iowa. Ordovician and From 425 to 500 million years ago.

3. Thickness and lithology of Upper Ordovician and Lower and Middle Silurian rocks in the Michigan Basin

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.