1. Institute of Geology and Mineralogy, Universität zu Köln, Zülpicher Strasse 49a, D-50674 Cologne, Germany
2. Department of Earth and Environmental Sciences, GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Strasse 10, D-80333 Munich, Germany
3. Center for Integrative Geosciences, University of Connecticut, Storrs, CT 06269, U.S.A.
4. Department of Geology, Kent State University, Kent, OH 44242, U.S.A.