1. Minnesota Isotope Laboratory, Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455
2. Department of Physics, National Science Foundation Accelerator Facility for Radioisotope Analysis, University of Arizona, Tucson, AZ 85721
3. Department of Biogeography and Geomorphology, Research School of Pacific Studies, Australian National University, Canberra, ACT 2601, Australia
4. Department of Geological Sciences, Cornell University, 2122 Snee Hall, Ithaca, NY 14853
5. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
6. Institute for Geophysics, University of Texas at Austin, Austin, TX 78759