This research used samples provided by the Ocean Drilling Program (ODP). ODP is sponsored by the U.S. National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI), Inc. We express sincere thanks to ODP for the important samples for our study. We also appreciate the shipboard and shore-based staff of ODP for handling and organizing the sampling. Kazumi Matsuoka and Martin J. Head reviewed the earlier manuscript and gave most helpful comments that improved the manuscript considerably. We also thank Isao Motoyama for useful information on the chronostratigraphy of the studied section. Japan Petroleum Exploration Co., Ltd. (JAPEX) generously offered laboratory assistance and granted the permission to publish. Ayoko Miura was responsible for the excellent sample preparation.