1. 1 Idaho Geological Survey, University of Idaho, Moscow, Idaho 83844-3012
2. *Present address: Wisconsin Geological and Natural History Survey, Madison, Wisconsin 53705-5100.
3. 2 Department of Geosciences, Boise State University, Boise, Idaho 83725-1535
4. **Present address: Division of Math, Science, & Tech Programs, Cloud County Community College, Concordia, Kansas 66901.
5. 3 U.S. Geological Survey, 904 W. Riverside Ave., Spokane, Washington 99201
6. 4 School of the Environment, Washington State University, Pullman, Washington 99164-2812