A preliminary 10Be chronology of Scandinavian Ice Sheet retreat from southwestern Norway

Temporal and spatial patterns of Pleistocene ice sheet deglaciation provide targets for numerical ice sheet simulations, a basis for predicting contemporary ice sheet retreat, and insights into mechanisms that control the tempo of ice sheet retreat. To compliment existing chronologies for the Scandinavian Ice Sheet (SIS), we initiated a campaign to constrain the deglaciation of the SIS in southwestern Norway using 10Be dating. Our sample locations range from Utsira Island, off the southwestern Norwegian coast, to the central mountain plateaus of southern Norway. The samples include two Late Glacial moraine complexes, previously assigned to the Younger Dryas Period (YD) and the Preboreal Oscillation. Our chronology, which uses a 10Be production rate constrained nearby, currently consists of 20 10Be ages; an additional 33 ages are awaiting AMS analysis. The ages from Utsira (21.3±2.1 ka; n=5, more pending), the only site that lies within the Norwegian Channel Ice Stream, show an extremely fast break up of the ice stream. Additionally, we have thus far constrained the timing of deglaciation of coastal mainland Norway at Jæren (15.1±0.3 ka; n=3), the landscape beyond the mouth of Lysefjord (13.3±0.4 ka; n=3), which is immediately outboard the YD moraines, samples from up-fjord of the moraines (10.9±0.5 ka; n=3), and in the central uplands ~110 km from the coast (11.0±0.1 ka; n=2). When complete, we expect our final chronology to provide new constraints on several key episodes of the deglaciation of southern Norway. In particular, we will test the hypothesis that the maximum ice extent during the YD occurred at different times in different sectors of Scandinavia.