FENNOSCANDIAN PALAEOGLACIOLOGY RECONSTRUCTED USING A GLACIAL GEOLOGICAL INVERSION MODEL

The evolution of ice-sheet configuration and flow pattern in Fennoscan dia through the last glacial cycle was reconstructed using a glacial g eological inversion model, i.e. a theoretical model that formalises th e procedure of using the landform record to reconstruct ice sheets. Th e model uses mapped flow traces and deglacial melt-water landforms, as well as relative chronologies derived from cross-cutting striae and t ill lineations, as input data. Flow-trace systems were classified into four types: (i) time-transgressive wet-bed deglacial fans, (ii) time- transgressive frozen-bed deglacial fans, (iii) surge fans, and (iv) sy nchronous non-deglacial (event) fans. Using relative chronologies and aggregation of fans into glaciologically plausible patterns, a series of ice-sheet configurations at different time slices was erected. A ch ronology was constructed through correlation with dated stratigraphica l records and proxy data reflecting global ice volume. Geological evid ence exists for several discrete ice-sheet configurations centred over the Scandinavian mountain range during the early Weichselian The buil d-up of the main Weichselian Fennoscandian ice sheet started at approx imately 70 ka, and our results indicate that it was characterised by a n ice sheet with a centre of mass located over southern Norway This co nfiguration had a flow pattern which is poorly reproduced by current n umerical models of the Fennoscandian ice sheet. At the Last Glacial Ma ximum the main ice divide was located over the Gulf of Bothnia. A majo r bend in the ice divide was caused by outflow of ice to the northwest over the lowest part of the Scandinavian mountain chain. Widespread a reas of preserved pre-late-Weichselian landscapes indicate that the ic e sheet had a frozen-bed core area, which was only partly diminished i n size by inward-transgressive wet-bed zones during the decay phase.