PALAEOGEOGRAPHY AND ENVIRONMENTAL CHANGE IN SW-SCANDINAVIA 40-15 KA BP

Stratigraphical evidence mainly from Denmark offers a unique possibility to synchronize climatically driven environmental changes and major glacio-dynamic events including former ice streams at the SW-rim of the Scandinavian Ice Sheet. Twelve palaeogeographic reconstructions illustrate the interaction between ice sheet behaviour, sea level change and the distribution of major lakes at 40-15 ka BP. Land, sea and glacier configurations are based on the lithostratigraphy of tills and inter-till sediments. Dating is provided by Optically Stimulated Luminescence and calibrated AMS radiocarbon. The evolution through the last glacial cycle falls in three sequences. The interstadial sequence c. 40-30 ka BP was characterized by a boreo-arctic fjord system controlled by the Norwegian Channel and subarctic treeless vegetation characterize surrounding terrestrial environments. The LGM sequence, c. 30-20 ka BP comprises the closure of former fjords and subsequent ice streams guided by glacial lake basins in the Kattegat depression and the Baltic. Steady flow of ice from Central Sweden towards Denmark probably bordered the Norwegian Channel Ice stream towards the northwest. The deglaciation sequence, c. 20-15 ka BP is characterized by transgression of arctic North Atlantic waters through the Norwegian Channel, retreat of the Swedish ice and advance of Baltic ice streams succeeded by a return to interstadial conditions. Our reconstruction predicts that while interstadial conditions governed by Atlantic climate amelioration prevailed in the eastern North Sea Region and adjacent landmasses, glaciers originating in the Scandinavian mountains were able to advance east and southward through the western Baltic. On the other hand, during interstadial regimes when subarctic conditions dominated in Denmark and the western Baltic glaciers expanded from southern Norway into the North Sea and Skagerrak. The largest glacier extent was reached in the North Sea around 29 ka BP, about 22 ka BP in Denmark and c.18 ka BP in the Baltic. Our model provides new data for future numerical and qualitative landform-based models, which ideally should be able to replicate the palaeogeographical settings presented here and at least they should address published stratigraphic frameworks.