Graham Leslie (1), Maarten Krabbendam (1), Michael Kelly (2), Kathryn Goodenough (1), Stuart Clarke (2) & Graham Williams (2)
(1) British Geological Survey, Murchison House, Edinburgh, EH9 3LA, UK. E-mail: agle@bgs.ac.uk
(2) Department of Geography, Geology and the Environment, Keele Keele, Staffordshire, ST5 5BG, UK.