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. The research was supported by JOI-USSAC (U.S. Science Advisory Committee) and NSF INT-0120120. We are grateful to John McArthur and an anonymous reviewer for helpful suggestions.