1. Geology Department, University of Puget Sound, 1500 North Warner Avenue, Tacoma, Washington 98416-1048, USA
2. Department of Geosciences, Princeton University, Guyot Hall, Princeton, New Jersey 08544, USA
3. Department of Earth and Space Sciences, University of Washington, Box 351310, 4000 15th Avenue NE, Seattle, Washington 98195-1310, USA