1. Faculty of Chemical Engineering and Materials Science, Organic Geochemistry Unit, Delft University of Technology, De Vries van Heystplantsoen 2, 2628 RZ Delft, Netherlands
2. Department of Geology, University of Oslo, P.O. Box 1047, Blindern, N—0316, Oslo 3, Norway
3. Current address: Fye Laboratory, Department of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
4. BP Research Centre, Sunbury-on-Thames, TW16 7LN, United Kingdom