1. Geology and Environmental Science, James Madison University, 801 Carrier Drive, Harrisonburg, Virginia 22807, USA
2. Geological Survey of Canada–Atlantic Division, Natural Resources Canada/Government of Canada, 1 Challenger Drive, Dartmouth, Nova Scotia B2Y 4A2, Canada
3. Department of Geoscience, University of Wisconsin–Madison, Lewis G. Weeks Hall, 1215 West Dayton Street, Madison, Wisconsin 53706-1692, USA
4. Department of Geosciences, University of Massachusetts, 627 North Pleasant Street, Amherst, Massachusetts 01003, USA