1. Geological Survey of Canada, Natural Resources Canada, Bedford Institute of Oceanography, Box 1006, Dartmouth NS B2Y 4A2, Canada
2. Graduate School of Oceanography, University of Rhode Island, South Ferry Road, Narragansett RI 02882-1197, U.S.A.
3. Department of Earth Sciences, University of Waterloo, 200 University Avenue, Waterloo ON N2L 3G1, Canada
4. Department of Earth Sciences, Brock University, 500 Glenridge Avenue, St. Catharines ON L2S 3A1, Canada
5. Department of Geological Sciences, University of Michigan, C.C. Little Building, 1000 North University Street, Ann Arbor MI 48109-1005, U.S.A.