New aspects of lake-level changes: Lake Balaton, Hungary

Abstract

Lake Balaton is the largest shallow-water lake in Central Europe. The main objective of the research on its Quaternary lacustrine sediments was to reconstruct the evolution of Lake Balaton from its formation until today. One of the key parameters in answering this question is to retrace lake-level changes. There is a lot of evidence, such as sedimentological, mineralogical, geochemical, archaeological, etc. to reveal these changes. Each type is of different reliability depending upon the sensitivity of the lake to level change and to preservation of the traces of those changes as a result of geologic, climatologic or human factors. The average thickness of Quaternary sediments accumulated in Lake Balaton is 5 m. From the lake bottom toward the surface lacustrine sediments are constituted by clastic deposits, peat and calcareous mud with upward-increasing carbonate content (calcite, dolomite, Mg-calcite, protodolomite and aragonite). Towards the end of Pleistocene, approximately 15,000-17,000 years BP, several shallow ponds with clean and cold water formed in the site of the present Lake Balaton. Inundation followed progressively from west to east. A warming climate and increasing precipitation brought about the rise of the water level. Moreover, abrasion progressively destroyed the dams separating the ponds and a uniform lake was formed. Later, as a function of changing climate the water level of the lake varied approximately between 103.0 and 108.0 m aASl. (above Adriatic Sea level). The average rate of total lacustrine sediment accumulation is 0.38 mm/year.