1. Department of Geological Sciences, University of Oregon, Eugene, OR 97403, USA.
2. Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, CA 94720, USA.
3. Department of Geography, University of Oregon, Eugene, OR 97403, USA.
4. Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA.
5. Department of Geography, University of Alabama, Tuscaloosa, AL 35487, USA.
6. School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK.