I am grateful to John A. Barron, Itaru Koizumi, and Lona Dearmont for their critical reviews and suggestions for improving the manuscript. Funding for the research was partly supplied by the Grant-in-Aid for Scientific Research of the Ministry of Education, Science and Culture of Japan, No. 07640618, provided to T. Maruyama. I thank Mitch Lyle, Carl Richter, and the scientists and crew members of Leg 167 of the JOIDES Resolution for their support and encouragement.