John Foster, a former graduate student at Purdue University, played a key role in the detailed demagnetization and analysis of the hundreds of paleomagnetic minicores. We thank Buffy McClelland (University of Oxford) and Rob Van der Voo (University of Michigan) for providing generous access to their laboratories for extended intervals. This project was supported by grants from USSAC and NERC. Our shipboard colleagues, especially the paleontology teams and the ODP curatorial staff, tolerated our extensive minicore sampling and eagerly worked with us on the biomagnetostratigraphic framework. Jim Channell performed a thorough review of the manuscript, and the ODP editorial office fine-tuned the presentation.