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Abstract
The interpretation of the development of the ancient lake is based on macrofossil-analytical and stratigraphical investigations. The principal aim has been to establish the water level or groundwater level fluctuations that have occurred.
Two major lowerings of the water level have been established. An older lowering began during the later part of the Pre-Boreal period and must have culminated during either the Early or Late Boreal period — a more precise dating was unfortunately not possible. The lowering was preceded by a distinct but short rise of the water level during the earlier part of the Pre-Boreal period. A younger lowering culminated during the Early Sub-Boreal period.
Extensive parts of the ancient lake became overgrown already during the Pre-Boreal period, and the overgrowing was probably completed in connection with the lowering during the Early Sub-Boreal period.
Each lowering was succeeded by a rise of the water level. The rise after the older lowering culminated during the middle part of the Late Atlantic period, the rise after the younger one probably during the Early Sub-Atlantic period. The latter was so considerable that extensive parts of the overgrown ancient lake again became submerged.
