^a Department of Geology, University of Pretoria, Hillcrest, Pretoria 0002, South Africa

^b Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA

^c Maersk Oil and Gas AS, Esplanaden 50, DK-1263 Copenhagen, Denmark

^d Sciences de la Terre, Université du Québec à Chicoutimi, Chicoutimi, QU G7H 2B1, Canada

^e Institut für Allgemeine und Angewandte Geologie, Ludwig-Maximilians-Universität, Luisenstraße 37, D-80333 München, Germany

^f Department of Geology, University of Toronto, Toronto, ON M5S 3B1, Canada

^g 23 Newton Street, Ottawa, ON K1S 2S6, Canada

^h Department of Geology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa

ⁱ Environmental Research Center, State University of New York at Oswego, Oswego, N.Y. 13126, USA