A ¹⁰Be chronology of south-western Scandinavian Ice Sheet history during the Lateglacial period

We present 34 new cosmogenic ¹⁰Be exposure ages that constrain the Lateglacial (Bølling-Preboreal) history of the Scandinavian Ice Sheet in the Lysefjorden region, south-western Norway. We find that the classical Lysefjorden moraines, earlier thought to be entirely of Younger Dryas age, encompass three adjacent moraines attributed to at least two ice sheet advances of distinctly different ages. The ¹⁰Be age of the outermost moraine (14.0±0.6 ka; n=4) suggests that the first advance is of Older Dryas age. The innermost moraine is at least 2000 years younger and was deposited near the end of the Younger Dryas (11.4±0.4 ka; n=7). After abandonment of the innermost Lysefjorden Moraine, the ice front receded quickly towards the head of the fjord, where recession was interrupted by an advance that deposited the Trollgaren Moraine at 11.3±0.9 ka (n=5). ¹⁰Be ages from the inboard side of the Trollgaren Moraine suggest final retreat by 10.7±0.3 ka (n=7). The late culmination of the Younger Dryas advance contrasts with other sectors of the Scandinavian Ice Sheet where the margin appears to have culminated earlier during the Younger Dryas stadial, followed by retreat during the middle and late part of the Younger Dryas.