We thank Tim Bralower, Debbie Thomas, and Dave Rea, who provided helpful suggestions on early versions of this paper that were incorporated into this final version. This research used samples, data, and funding 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countries under management of Joint Oceanographic Institutions (JOI), Inc. Helen Evans graciously allowed us access to unpublished magnetostratigraphic data.