This project was funded by the United States Science Support Program of the Joint Oceanographic Institutions. The manuscript benefitted from the many useful suggestions that were provided by Gren Draper, Katerina Petronotis, and two anonymous reviewers, as well as from the effort of the entire Shipboard Scientific Party during Leg 165. We also thank John Geissman for use of the paleomagnetism laboratory at the University of New Mexico.