We thank M. Malone and two anonymous reviewers for comments that helped to improve the manuscript and D. Walizer for technical assistance. 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 research was partially funded by grants from NSF and JOI/U.S. Science Support Program. A.E. was supported by the Yoshida Scholarship Foundation, YKK Co., Tokyo.