1. British Geological Survey, The Lyell Centre, Research Avenue South, Riccarton, Edinburgh EH14 4AP, UK
2. School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland
3. Geological Survey of Denmark and Greenland, Øster Vøldgade 10, DK-1350 Copenhagen, Denmark
4. ÍSOR (Iceland Geosurvey), Deptartment of Energy Technology, Rangarvellir, PO Box 30, 602 Akureyri, Iceland
5. Department of Earth Sciences, University of Bergen, Allegaten 41, N-5007 Bergen, Norway
6. Centre for Earth Evolution and Dynamics, University of Oslo, Postbox 1028, Blindern, N-0135 Oslo, Norway
7. Present address: ION Geophysical, 1st Floor, Integra House, Vicarage Road, Egham TW20 9JZ, UK
8. Jarðfeingi, Brekkutín 1, PO Box 3059, FO-110 Tórshavn, Faroe Islands