1. 1Department of Earth and Environmental Sciences, University of Michigan, 1100 North University Avenue, Ann Arbor, Michigan 48109-1005, USA
2. 2Department of Geosciences, Boise State University, 1910 University Drive, MS 1535, Boise, Idaho 83725-1535, USA
3. 3U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA