1. Geology Department; Pomona College; 185 E 6 St. Claremont CA 91711 USA
2. Department of Geosciences, Pennsylvania State University; University Park; Pennsylvania 16802 USA
3. Department of Geosciences; University of Tübingen; Wilhelmstraße 56 Tübingen 72076 Germany
4. W. M. Keck Science Department; Claremont McKenna, Pitzer, and Scripps Colleges; 925 N. Mills Ave Claremont CA 91711 USA
5. Department of Earth, Planetary, and Space Sciences; University of California Los Angeles; 595 Charles Young Drive East Los Angeles CA 90095 USA
6. Department of Geography; University of Sheffield; Winter Street Sheffield S10 2TN UK