1. Canadian Museum of Nature, P.O. Box 3443, Station D, Ottawa, ON K1P 6P4, Canada.
2. Department of Geography, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
3. Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1 Canada.
4. Geological Survey of Canada, Ottawa, ON K1A 0E8, Canada.