1. Institute for Ecosystem Research; University of Kiel; Olshausenstrasse 75 24118 Kiel Germany
2. Leibniz Laboratory for Radiometric Dating and Isotope Research; University of Kiel; Max-Eyth-Str. 11-13 24118 Kiel Germany
3. McDonald Institute for Archaeological Research; University of Cambridge; Downing Street Cambridge CB2 3ER UK