1. Department of Geology and Environmental Science, James Madison University, MSC 7703, Harrisonburg, VA 22807
2. Indiana Geological Survey, Indiana University, 611 North Walnut Grove, Bloomington, IN 47405-2208
3. Department of Geological Sciences, Indiana University, Bloomington, IN 47405
4. U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, MI 48105