Readvance and retreat of the Late Weichselian Low Baltic ice stream in southernmost Sweden – a review

Abstract

The aim of this study was to review old and new evidence for the readvance and retreat of the Low Baltic ice stream. The review is based partly on new field observations from southernmost Sweden and new dates relating to the marginals of the ice stream. The diamicton deposited by the Low Baltic ice stream is mainly a subglacial till (Malmö till) rich in clay and chalk. In addition, there are clasts and microfossils in the till derived from the bedrock in the Baltic area. This suggests that they were transported up to 700 km. The likelihood is that the ice moved upon a subglacial bed of mainly fine-grained, deformable sediments. It is also possible to think that the ice shut-down of the deforming bed-driven ice stream, was the result of sediment exhaustion. The sharp limits and low level of the Malmö till, and the sharp limit between an area of low relief hummocky moraine and an area of high relief hummocky landscape, are indicative of deposition from a lowland ice stream. The dating of the deglaciation of the Low Baltic ice stream shows that the ice stream existed approximately 18 000 to 14600 calendar years BP. At the end of this period the first stage of the Baltic Ice Lake opened.

Keywords:

• Readvance
• retreat
• lowland ice stream
• southernmost Sweden
• deforming bed
• sediment exhaustion