This research used samples and/or data supplied by the Ocean Drilling Program (ODP). ODP is supported by the U.S. National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI), Inc. The technical support from Leg 200 crew, staff, and scientists aboard the JOIDES Resolution is acknowledged. This research was supported by a U.S. National Science Foundation JOI/U.S. Science Advisory Committee grant. We thank the anonymous reviewers for their comments. We also thank Gary Acton for his helpful review.