1. Department of Environmental Sciences, Western Norway University of Applied Sciences, Røyrgata 6, 6856 Sogndal, Norway
2. Geological Survey of Norway, PO Box 6315, Torgarden, 7491 Trondheim, Norway
3. Department of Geosciences and CEED, University of Oslo, PO Box 1047, Blindern, 0316 Oslo, Norway