Study of geology at the University of Delaware, B.S. (1981) Geology, University of Delaware, M. A. (1983), M. Phil. (1987), and PhD (1989) Geochemistry, Columbia University. Post-doctoral Researcher, Center for Accelerator Mass Spectrometry, Lawrence Livermore Laboratory,  Lamont-Doherty Geological Observatory, and Swiss Federal Institute of Technology, Zurich/Switzerland (1989-1991). Assistant Professor (1991- 1996), Associate Professor (1996 -2000) and Full Professor of Earth System Science at the University of California, Irvine. Director and Scientific Member at the Max Planck Institute for Biogeochemistry (since 2009).