The time and style of deglaciation has been investigated by analysis of in situ10Be in bedrock samples from three sites in Nordland, northern Norway. At the coast, 10Be data indicate rapid deglaciation of the island Åmøya at about 14.3 ± 0.4 10Be ka (n=9). In the fjord area, perched blocks and erratic boulders indicate that the summit of Helgelandsbukken was ice covered at some stage, yet little affected by glacial erosion as is evident from the 10Be data (>30 10Be ka, n=5). Further inland, 10Be data from Addjektind indicate that the Fennoscandian ice sheet was fragmented into valley glaciers by c. 10.2 ± 0.3 10Be ka (n=7). Preliminary 2D ice-flow modelling supports the degree of glacial erosion as inferred from the 10Be data; past ice cover has been ‘thick and erosive’ at the coast and partly in the inland, whereas ‘thin and preserving’ and probably cold-based at summits in the fjord zone. The 10Be ages presented here support and add detail to the regional 14C-based deglaciation chronology. Tentative rates of ice-surface lowering are >25 cm yr-1 at the coast (18-14 ka) and ~ 5 cm yr-1 inland (18-10 ka).
Lars Olsen, Geological Survey of Norway, Leiv Erikssons v. 39, N-7491 Trondheim, Norway;
Edward J. Brook, Department of Geosciences, Oregon State University, Corvallis, OR 97330, USA; Jessica R. Darter, David M. Mickelson, Department of Geology and Geophysics, University of Wisconsin, 1215 Dayton St., Madison, WI 53706, USA;
Grant M. Raisbeck, Françoise Yiou, Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, IN2P3-CNRS, Bâtiment 108, F-91405 Orsay, France.