1. Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403, U.S.A.,
2. Museum of Natural and Cultural History, University of Oregon, Eugene, Oregon 97403, U.S.A.,
3. Clark Honors College, University of Oregon, Eugene, Oregon 97403, U.S.A.,
4. Isotope Geology Laboratory, Department of Geosciences, Boise State University, Boise, Idaho 83725, U.S.A.,