1. Illinois State Geological Survey, University of Illinois, 61820 Champaign, USA
2. School of Earth and Environmental Sciences, University of Manchester, M139PL, Manchester, United Kingdom
3. Biogeochemistry and Modelling of the Earth System, Université libre de Bruxelles, 1050 Brussels, Belgium
4. GeoCarb Consult, 56 Calle de Narvaez, 28009 Madrid, Spain
5. TOTAL Exploration and Production, 2 place Jean Millier, 92078 Paris La Défense Cedex, France