1. Department of Geology, University of Cincinnati, 500 Geology Physics Building, Cincinnati, Ohio 45221-0013, USA
2. Department of Geoscience, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, T2N 1N4, Canada
3. Department of Geology, Union College, 807 Union Street, Schenectady, New York 12308-2311, USA
4. Department of Geology, Carleton College, One North College Street, Northfield, Minnesota 55057, USA