We are grateful to Prof. Pinxian Wang for his suggestions and revision of the manuscript. We especially thank Prof. Warren Prell of Brown University and Dr. Robert Owen of the University of Michigan for helpfully reviewing the manuscript; their comments and constructive criticisms greatly improved our presentation. This research used samples and data 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. This project was supported by the NKBRSF (grant number G2000078500), and the National Natural Science Foundation of China (grant number 49946011 and 49999560), the National Foundation for the Authors of Excellent Doctoral Dissertations of the People's Republic of China (project number 200126), and the Foundation for University Key Teachers, Ministry of Education, China.