An alternative Weichselian glaciation model, with special reference to the glacial history of Skåne, South Sweden

A revised lithostratigraphy of Skane, South Sweden, constitutes the basis of an alternative Weichselian glaciation model for southern Scandinavia, progressively anchored to the stratigraphy. Skane was not glaciated during the Weichselian until 21,000 B.P. The concepts, outlet surge and marginal dome (the main tools of the model) are defined. The palaeogeography of the Baltic and Kattegatt basins during the Mid-Weichselian are reconstructed. Shorelines, during the advance stage, are calculated from an inferred proglacial depression. Outlet surges, which occurred in three basins of the Baltic, guided the ice sheet during its growth. The growth of marginal domes on the outlet surge lobes resulted in changes in the configuration of the ice sheet and in the lowering of its surface profile. The South Scandinavian ice divide became located over a former outlet surge lobe NNE-NE of the island of Gotland in the northern Baltic. This gave the main ice in South Sweden and Denmark a NE ice movement during the whole glaciation until the deglaciation of SE Sweden. The Kattegatt Ice Lake was formed due to damming in the Skagerack area. Surging ice tilled in the basin resulting in the formation of vast areas of stagnant ice in front of the advancing NE-ice. Marginal domes were formed on these giving rise to the early glacial episodes in the southwest of Sweden and Denmark. During the deglactanon, tnree pnases of marginal dome formation are recorded in the soutnern Baltic area and the growth of these domes resulted in the East Jylland advance, the Baelthav readvance and the Simrishamn readvance. The marginal domes were formed on vast fields of stagnant ice left behind by the receding main ice. Baltic erratics, englacially present in the main ice as well as in the stagnant ice in front of it, were transported (stepwise) towards the west and northwest, partly by the advancing marginal domes and partly by ice streams formed between the marginal domes and the main (NE-) ice. It is argued that the classical, so-called Low Baltic ice stream in the sense of a readvancing glacier lobe never existed. The first two marginal domes collapsed due to starvation and the ice movement returned gradually to the independent NE ice movement of the main ice. The third marginal dome collapsed due to a downdraw caused by a large transgression recorded in the Kattegatt and the Oresund regions. The transgression took place roughly around 13,300 B.P. and was possibly caused by damming of the Kattegatt basin in the north in connection with a marine downdraw. The collapse of the third marginal dome and the subsequent ‘ice lake downdraw’ of the dome centre NNE-NE of Gotland took place during a cold period of the deglaciation. This resulted in an extremely high recessional rate on the Swedish cast coast compared with the west coast and a contemporaneous westwards displacement of the South Scandinavian ice divide. After the downdraw, the recession rate on the east coast slowed down markedly and became more or less equal to that of the west coast. Pure dynamic causes for the extremely high recession rate in SE Sweden are expected because the decrease in this rate coincides with the onset of a recorded, marked climatic amelioration at around 12,600 B.P. Formation of the marginal domes during the deglaciation indicates periods of increased cyclon activity at the southwest margin of the Weichsclian Scandinavian ice sheet alternating with periods of ice sheet starvation. Detailed modelling of the marginal domes is therefore expected to have significant palaeoclimatic implications. The marginal dome concept is believed to he useful also in the reconstruction of earlier glaciations.