Tab. 1: Radiocarbon ages for sediment core POS220_47-1

A study of organic-walled microfossils from sediment cores of the Central Baltic Sea (North Central Basin, Gotland Basin, Bornholm Basin) and the Kiel Bight was carried out to increase our knowledge of the environmental changes in the Baltic Sea. For this purpose, the absolute abundance of these microfossils were recorded. Quantitative measurements of morphological change of the dinoflagellate Operculodinium centrocarpum, which indicate salinity changes, were performed. The cores from the Central Baltic Sea are correlated ecostratigraphically. The cores from Gotland Basin and Kiel Bight are correlated chronostratigraphically, based on absolute age dating. The first marine influence, indicated by the first occurrence of marine dinoflagellate cysts, and the interval with rapid rising salinity, was dated for Kiel Bight to 8400-7400 yr BP (calendar years), and for the Gotland Basin to 7400-6500 yr BP. The first saline maximum of the early phase of the Littorina Transgression can be found around 6500 yr BP in the Gotland Basin as well as in the Kiel Bight. A significant drop in salinity of the Central Baltic Sea, which was more intense in the northern part, is at 2800 yr BP., whereas a slight increase in salinity took place in the Kiel Bight during this time