1. Massachusetts Institute of Technology—Woods Hole Oceanographic Institution Joint Program in Oceanography, Cambridge, MA 02139
2. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
3. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
4. Department of Geological Sciences, University of Oregon, Eugene, OR 97403