Context The
Baltic Ice Lake, the Yoldia Sea, the
Ancylus Lake and the
Littorina Sea are four recognized stages in the postglacial progression of the Baltic basinthere are also transition periods which can be considered as substages. From earliest to most recent they run: • The Baltic Ice Lakefresh water
proglacial lake with level greater than sea leveldammed by glacial ice until the ice dam broke free at the north slope of
Billingen uplandsthe lake level then dropped about to sea levelat 9,670 years BCE. This was the Yoldia Sea. The Yoldia Sea existed from 11.7 ka BP, but it took about 400 years before the brackish phase that lasted from 11.3 to 11.1 ka BP. Geographically, the
Gulf of Bothnia remained under the ice. The
Gulf of Finland was open but most of Finland was an
archipelago, over which debris carried by glacial streams gradually spread. A land bridge joined Germany to southern Sweden through Denmark. Relieved of its weight of ice, Finland rose gradually and unevenly from the sea. Parts of the Yoldia shoreline are above sea level today while other parts remain below. The Yoldia Sea toward its end was about 30m below current sea level. A channel at the location of the
Neva River connected Yoldia Sea to
Lake Ladoga. The Yoldia Sea existed entirely within the
Boreal Blytt–Sernander period. The forests and species lining its shores were boreal.
Mesolithic cultures continued to occupy Denmark/south Sweden and the southern shores of the sea. The sea as an ecologic system came to an end when Scandinavia rose sufficiently to block the flow through the Stockholm area and the saline balance shifted toward a
lacustrine ecology once again. After formation, increased melting of ice provided additional fresh water and the sea became stratified (
meromictic), with salt water on the bottom and fresh on top. Over the life of the sea and from location to location the salinity was a variable. Whether it is possible to speak of stages of salinity that would apply uniformly to the whole sea is debatable.
Sea end The land uplift in south-central Sweden as the glaciers retreated, stopped the water inflow from the world sea by 10.7 ka BP. A rapid Ancylus Lake transgression started then about 10.7 ka BP, and reached its highstand about 10.3 ka BP. At 10.2 ka BP the lake/sea broke through Denmark creating the first
Great Belt channels and the Dana River along the new outlet. The total opening was less than wide and included two channels at the northern end. This likely led to an initial lowering of the Ancylus Lake by about . At about 9.8 ka BP, sea level became higher than the lake level, and saline water began to enter the lake to form the next sea phase, the
initial Littorina Sea. == Notes ==