1. U.S. Geological Survey, Flagstaff, Arizona 86001, USA
2. School of Geosciences, University of Oklahoma, Norman, Oklahoma 73019, USA
3. Department of Earth and Planetary Science, University of New Mexico, Albuquerque, New Mexico 87106, USA
4. New Mexico Bureau of Geology and Mineral Resources, Socorro, New Mexico 87801, USA
5. Arizona Geological Survey, University of Arizona, Tucson, Arizona 85721, USA
6. Geosciences Department, Utah State University, Logan, Utah 84322, USA
7. U.S. Geological Survey, Menlo Park, California 94025, USA