1. Badleys Ltd, North Beck House, North Beck Lane, Hundleby, Spilsby, Lincolnshire PE23 5NB, UK
2. Department of Geosciences, University of Oslo, Sem Sælands Vei 1, Oslo 0371, Norway
3. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
4. Petriva Ltd, University of Leeds, Leeds LS2 9JT, UK
5. British Geological Survey, The Lyell Centre, Edinburgh EH14 4AP, UK