Affiliation: | Laboratoire de Géosciences Marines, Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252;Paris Cedex 5, France. E-mail: Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ,;UK Schlumberger Cambridge Research, High Cross, Madingley Road, Cambridge CB3 0EL,;UK Geoscience Research Centre, Elf UK, London, UK |