1. Department of Geosciences, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
2. School of Natural Resources and the Environment, Lake Superior State University, Sault Ste. Marie, Michigan 49783, USA
3. Department of Earth and Environmental Sciences, University of Minnesota–Twin Cities, Minneapolis, Minnesota 55455, USA
4. Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts–Lowell, Lowell, Massachusetts 01854, USA
5. Department of Geological Science, University of Florida, Gainesville, Florida 32611, USA
6. School of Earth and Environmental Sciences, Washington State University, Pullman, Washington 99164, USA