10Be-based exploration of the timing of deglaciation in two selected areas of southern Norway

We present new Be-10 surface exposure ages from two selected locations in southern Norway. A total of five Be-10 samples allow a first assessment of local deglaciation dynamics of the Scandinavian Ice Sheet at Dalsnibba (1476 ma.s.l.) in southwestern Norway. The bedrock ages from the summit of Dalsnibba range from 13.3 +/- 0.6 to 12.7 +/- 0.5 ka and probably indicate the onset of deglaciation as a glacially transported boulder age (16.5 +/- 0.6 ka) from the same elevation likely shows inheritance. These ages indicate initial deglaciation commencing at the end of the Bolling-Allerod interstadial (similar to 14.7-12.9 kyr BP) and ice-free conditions at Dalsnibba's summit during the Younger Dryas. Bedrock samples at lower elevations imply vertical ice surface lowering down to 1334 ma.s.l. at 10.3 +/- 0.5 ka and a longer overall period of downwasting than previously assumed. Two further Be-10 samples add to the existing chronology at Blaho (1617 ma.s.l.) in south-central Norway. The Be-10 erratic boulder sample on the summit of Blaho sample yields 20.9 +/- 0.8 ka, whereas a Be-10 age of 46.4 +/- 1.7 ka for exposed summit bedrock predates the Late Weichselian Maximum. This anomalously old bedrock age infers inherited cosmogenic nuclide concentrations and suggests low erosive cold-based ice cover during the Last Glacial Maximum. However, due to possible effects of cryoturbation and frost heave processes affecting the erratic boulder age and insufficient numbers of Be-10 samples, the glaciation history on Blaho cannot conclusively be resolved. Comparing the different timing of deglaciation at both locations in a rather short west-east distance demonstrates the complex dynamics of deglaciation in relation to other areas in southern Norway.