1. U.S. Geological Survey, 4210 University Drive, Anchorage, Alaska 99508, USA
2. U.S. Geological Survey, Spokane, Washington 99203, USA
3. U.S. Geological Survey, Denver, Colorado 80225, USA
4. U.S. Geological Survey (retired), Anchorage, Alaska 99508, USA
5. Department of Earth Science, University of California, Santa Barbara, California 93106, USA
6. Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T-1Z4, Canada
7. Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska 99775, USA