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 organic 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 independent varve chronology which may be compared with results of radiocarbon dating. Comparison of measured C-14 activities in carbonate fractions of lake marl with varve ages allow for the accurate estimation of secular changes of the C-14 dilution factor of total dissolved inorganic carbon. Using the geochemical model developed by Broecker and Walton (1959) and reconstructed changes of C-14 dilution it has been possible to reconstruct mean lake level during the Lateglacial and Holocene. The results of model calculations are compared with an independent record of lake level changes deduced from C-14 dated lithological boundaries marking low and high lake stands in numerous cores taken along lake shores, as well as with lake level data available from southern Sweden and France. Obtained patterns of lake level fluctuations show remarkable similarities with behaviour of Swedish lakes and general agreement with available records from European lakes. The behaviour of Gosciaz Lake during the last 12 ka BP reflects global climatic changes fairly well.