Dan Hammarlund

Stable oxygen and carbon isotope data from a lacustrine sequence at Graenge, southeast Denmark, revealed distinct environmental changes related to Late Weichselian climatic development in the region. Comparison of isotopic records obtained from sedimentary carbonates and freshwater molluscs enabled reconstruction of changes in the lacustrine environment. The degree of thermal and chemical stratification of the lake was evaluated and supported by pollen data from an earlier study of the site. During the Allerod interstadial, dimictic and stagnant conditions characterized the lake, whereas the stratification was disturbed during the Younger Dryas stadial probably as a result of deforestation and increased wind impact. The origin of sedimentary carbonates was examined by mineralogic and morphologic studies. A considerable input of clastics and detrital carbonates, associated with pronounced enrichment of O-18 and C-13, was recorded in the Younger Dryas sediments indicating soil degradation and increased erosion. A climatic warming preceding the Pleistocene/Holocene boundary is clearly reflected in the different stable isotope records and in the lithostratigraphy.