1. Biomarine Sciences, Institute of Environmental Biology, Faculty of Science, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
2. Department of Marine Organic Biogeochemistry, NIOZ Royal Netherlands Institute of Sea Research, Post Office Box 59, 1790 AB Den Burg, Texel, Netherlands.
3. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK.
4. Geochemistry, Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands.