Das Rätsel des Ancylussees

Abstract

The Baltic basin within the circular Fennoscandian region of deglaciation updoming has a lenght axis that lies radially between the inner and outer hinge lines of the upwarped shore levels. Its first postglacial connection with the ocean, the Yoldia Sea stage, came into existence across Central Sweden in Närke in the beginning of the pre-Boreal time, Zone IV in forest history. The connection still prevailed during the Boreal Echineis Sea stage (earlier named by the author Rhabdonema Sea), because of the eustatic rise of the sea level, until the Subzone Vb in the forest history was reached. Thereafter, during the Subzone Vc, the threshold in Central Sweden was rapidly uplifted above sea level, as it happened to lie inside the younger inner hinge line at the very moment of its formation. Thus the Baltic water body converted into a lake, called the Ancylus Lake, which drained westward through an outlet channel at the place of the previous sound. After some 300 or 400 years the height of the lake already was so much as 13 m bis 14 m. Then, at the transition from Zone V to Zone VI in the forest history, this short-lived stage ended in a sudden drainage down to the level of the sea through the Belts in Denmark because of a crustal sinking in the outer part of the southwestern sector of the updoming area. A new transitional stage in the history of the Baltic, the Mastogloia Sea, set in to be followed, during the warm-climate maximum, by the Littorina Sea.