The Development of the Baltic Sea Basin During the Last 130 ka - The Baltic Sea Basin - page 87

Fig. 4.7 Paleogeographic
map showing the Ancylus
Lake during the maximum
transgression at ca. 10.5 ka
BP
of pine forests around the coasts of the southern Baltic basin. In the very south-
ern Baltic is a transgression recorded as evident from submerged pine trees and
peat deposits dated between 11.0 and 10.5 ka BP (Andrén et al. 2007 ) . This gradual
updamming - the outlet areas were rising faster than sea level - had varying impacts.
While areas to the north experienced a more or less slowed-down regression, the
extent of the transgression in the south varied largely, altitudinally and aerially,
depending on if areas were isostatically rising or submerging (Fig. 4.7 ) . The end
of the transgression often shows up as a beautiful raised beach along the Swedish,
Latvian, and Estonian coasts as well as on the island of Gotland. By a large num-
ber of 14 C dates of underlying peat as well as tree remains (mainly pine) in the
beaches, the time span for this so-called Ancylus transgression can be estimated
to ca. 500 years. The pattern of the isobases over S Sweden for the time of the
Ancylus Lake/transgression shows that the level of Baltic was higher than the sea
in the west, showing that the Ancylus Lake was updammed. The final and total
updamming effect has been estimated to have raised the Baltic ca. 10 m above sea
level (Björck et al. 2008 ) , which means that (isostatically) submerging areas in the
southernmost Baltic experienced a larger transgression than that.
The transgression and flooding in the south as a consequence of a “tipping bath-
tub effect” would inevitably result in a new outlet in the south. Since Öresund had
been uplifted more than potential outlet/sill areas further south, these southern areas
were now lower than Öresund. What now might have followed is described in detail
by Björck et al. ( 2008 ) , but available data indicate that the Darss Sill area, between