1Earth Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
2Centre Européen de Recherche et d’Enseignement en Géosciences de l’Environnement (CEREGE), Europôle de l’Arbois, BP 80, 13545 Aix en Provence Cedex 04, France
3Department of Integrative Biology and Human Evolution Research Center, The University of California, Berkeley, CA 94720, United States
4Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, United States
5Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, United States
6Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, United States
7Rift Valley Research Service, P.O. Box 5717, Addis Ababa, Ethiopia