1. Preliminary digital geologic map of the Penokean (early Proterozoic) continental margin in northern Michigan and Wisconsin Author/Creator: Cannon, William F. Publication/Creation: [Reston, Va.] : U.S. Dept. of the Interior, U.S. Geological Survey, [2000] Resource Type: Map Access & Availability: Loading
2. Geologic map of Precambrian rocks, southern Lake Superior region, Wisconsin and northern Michigan Author/Creator: Geological Survey (U.S.) Publication/Creation: Reston, Va. : U.S. Geological Survey, 1992 Resource Type: Map Access & Availability: Loading