1. J. C. Brannon, S. C. Cole, F. A. Podosek, Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130-4889, USA.
2. V. M. Ragan and R. M. Coveney Jr., Department of Geosciences, University of Missouri, Kansas City, MO 64110-2499, USA.
3. M. W. Wallace and A. J. Bradley, School of Earth Sciences, University of Melbourne, Parkville, Victoria 3052, Australia.