We thank Pinxian Wang for guidance and help and Zhimin Jian, Xin Su, and Lei Shao for their assistance in sampling. A careful review by Hui Jiang greatly improved this presentation. 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. Funding for this research was provided by the Natural Science Foundation of China (no. 49999560), the Knowledge Innovation Project of the Chinese Academy of Science (grant no. KZCX3-SW-220), and the National Key Project for Basic Research (no. 2000078500).