1. Geological Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, California 94305, USA, and Kaiser-Francis Oil Company, 6733 South Yale Avenue, Tulsa, Oklahoma 74136, USA
2. Geological Sciences, Stanford University, 450 Serra Mall, Building 320, Stanford, California 94305, USA
3. The WiscSIMS Laboratory, Department of Geoscience, University of Wisconsin–Madison, Weeks Hall, 1215 West Dayton Street, Madison, Wisconsin 53706, USA
4. Radiogenic Isotope and Geochronology Laboratory, School of the Environment, Washington State University, 100 Dairy Road, Pullman, Washington 99164, USA, and School of Earth Sciences, The University of Western Australia (M004), 35 Stirling Highway, Perth, WA 6009, Australia
5. Radiogenic Isotope and Geochronology Laboratory, School of the Environment, Washington State University, 100 Dairy Road, Pullman, Washington 99164, USA