1. Dept of Physical Geography and Quaternary; University of Liege; Sart Tilman, B11 4000 Liege Belgium
2. FRIA; 1000 Brussels Belgium
3. GIRPAS, Dept of Physics; University of Liege; Sart Tilman, B5 4000 Liege Belgium
4. Fund for Scientific Research - FNRS; 1000 Brussels Belgium