LATEGLACIAL AND HOLOCENE WATER-LEVEL CHANGES OF THE GOSCIAZ LAKE, CENTRAL POLAND, DERIVED FROM CARBON-ISOTOPE STUDIES OF LAMINATED SEDIMENT

Radiocarbon and stable carbon isotope ratios have been measured in org anic and carbonate fractions of laminated sediment of the Gosciaz Lake , Central Poland. Parallel varve counting in four cores taken from the deep central part of the lake have led to the development of an indep endent varve chronology which may be compared with results of radiocar bon dating. Comparison of measured C-14 activities in carbonate fracti ons of lake marl with varve ages allow for the accurate estimation of secular changes of the C-14 dilution factor of total dissolved inorgan ic carbon. Using the geochemical model developed by Broecker and Walto n (1959) and reconstructed changes of C-14 dilution it has been possib le to reconstruct mean lake level during the Lateglacial and Holocene. The results of model calculations are compared with an independent re cord of lake level changes deduced from C-14 dated lithological bounda ries marking low and high lake stands in numerous cores taken along la ke shores, as well as with lake level data available from southern Swe den and France. Obtained patterns of lake level fluctuations show rema rkable similarities with behaviour of Swedish lakes and general agreem ent with available records from European lakes. The behaviour of Gosci az Lake during the last 12 ka BP reflects global climatic changes fair ly well.