Affiliation: | Institute for Marine Resources and Environment, Geological Survey of Japan, AIST, Tsukuba 305-8567,;Japan. E-mail: Palaeomagnetic Laboratory 'Fort Hoofddijk', Faculty of Earth Sciences, Utrecht University, Budapestlaan 17, 3584;CD Utrecht, the Netherlands. E-mail: Department of Biosphere-Geosphere System Science, Okayama University of Science, Okayama 700-0005,;Japan |