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of the BIL and the sea gradually rose. It has been estimated that this difference at
This is thought to have been the consequence of ice recession north of the south
Swedish highlands and Mt. Billingen, situated between Lake Vättern and Lake
middle Swedish lowlands and opened up a contact between the sea in the west,
occupying, e.g., Lake Vänern, and the BIL. Due to a later ice readvance and erosion
of the deglaciated terrain, the proofs for this drainage are more of circumstantial
concrete drainage deposits. It may have been recorded in the Arkona basin as basin-
water entered the Baltic basin.
When the Younger Dryas cooling set in at ca. 12.8 ka BP, the ice sheet advanced
south over the previously deglaciated areas and once again blocked the northern
drainage of the BIL at Mt. Billingen. This ponding effect might have been a gradual
process but must have led to a more or less rapid transgression, depending on how
long the updamming took, until the Öresund outlet functioned again. Complex
less contact with the BIL during Younger Dryas, imply that the BIL experienced a
complex water level history during this time period. It has been shown that during
Fig. 4.4
Paleogeographic
map showing the Baltic Ice
Lake just prior to the
maximum extension and final
drainage at ca. 11.7 ka BP