1. Department of Earth Sciences University of Oxford South Parks Road Oxford OX1 3AN UK
2. Department of Earth Sciences Università degli Studi di Milano 20133 Milan Italy
3. Department of Geosciences Universität Tübingen Hölderlinstrasse 12 72074 Tübingen Germany
4. Organic Geochemistry Unit Cabot Institute and School of Chemistry University of Bristol Cantock's Close Bristol BS8 1TS UK
5. Shell Projects and Technology Kessler Park 1 2288 GS Rijswijk The Netherlands