Abstract
After the last deglaciation, the Baltic Sea underwent a complex salinity history and dynamic shore-level development with several lacustrine and marine stages: the Baltic Ice Lake, the Yoldia Sea, the Ancylus Lake and the Littorina Sea (Björck 1995). In connection with shallow seismic profiling in the south-western Baltic Sea, two marked and widespread erosional unconformities have been identified (Jensen et al. 1997, 1999; Lemke et al. 1998; Larsen 2004). The older unconformity occurs within sediments deposited in the Baltic Ice Lake, whereas the younger one separates Baltic Ice Lake sediments from Holocene lake and mire deposits. The latter unconformity is dated to the transition between the Younger Dryas and the Holocene, corresponding to c. 11.7 cal. ka BP and formed due to a sudden drop in the level of the icedammed Baltic Ice Lake of around 25 m, caused by ice recession from Mt. Billingen in south central Sweden.
Highlights
After the last deglaciation, the Baltic Sea underwent a complex salinity history and dynamic shore-level development with several lacustrine and marine stages: the Baltic Ice Lake, the Yoldia Sea, the Ancylus Lake and the Littorina Sea (Björck 1995)
It has been suggested that the level of the Baltic Ice Lake experienced a sudden drop during the Allerød chronozone
Coring positions are selected from high-resolution, shallow seismic profiles, but in the deeper parts of the Arkona Basin, gas-bearing, organic-rich, Holocene marine sediments are widespread and hamper the use of seismic data
Summary
The Baltic Sea underwent a complex salinity history and dynamic shore-level development with several lacustrine and marine stages: the Baltic Ice Lake, the Yoldia Sea, the Ancylus Lake and the Littorina Sea (Björck 1995). The older unconformity occurs within sediments deposited in the Baltic Ice Lake, whereas the younger one separates Baltic Ice Lake sediments from Holocene lake and mire deposits. Ka BP and formed due to a sudden drop in the level of the icedammed Baltic Ice Lake of around 25 m, caused by ice recession from Mt. Billingen in south central Sweden. The older erosional unconformity may have formed in connection with an early drainage of the Baltic Ice Lake. The question about such an early lake-level fall was discussed by Björck (1995), who listed a number of arguments for and against it. The basin is up to m deep and the surface of the till is found at a depth of 30 to 70 m (Moros et al 2002)
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