This research used samples and/or data provided by the Ocean Drilling Program (ODP). ODP is sponsored by the National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI), Inc. Funding for this work was provided by NSF, JOI U.S. Science Support Program, and the American Chemical Society-Petroleum Research Fund. Additional support for this work was provided by the David and Lucile Packard Foundation through a postdoctoral fellowship (to Johnson) at the Monterey Bay Aquarium Research Institute (MBARI). We thank Gerhard Bohrmann, Lisa McNeill, and an anonymous reviewer for comments that greatly improved this manuscript.