1. Department of Geology, Miami University, Oxford, Ohio 45056, Department of Geosciences, State University of New York, Stony Brook, New York 11794-2100, Department of Earth & Environmental Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180, and Chemistry Division and the Glenn T. Seaborg Institute for Transactinium Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545