Tree stumps from the bottom of the Vistula Lagoon as indicators of water level changes in the Southern Baltic during the Late Holocene

The Vistula Lagoon is situated along the south-eastern shore of the Gulf of Gdańsk and is linked with the gulf through the Strait of Baltiysk. Separated from the open sea by the Vistula Spit, the Vistula Lagoon is a shallow body of water with a mean depth of 3 m; the bottom is covered with a layer of mud several metres thick. This article presents a unique, newly discovered locality of tree stumps occurring in situ at the bottom of the Vistula Lagoon. The radiocarbon age of the alder stumps and the top of the peat in which they are rooted is Subboreal. The alder wood was dated to 4770±35 and 3295±35 years BP. The top layers of peat were dated to 4670±40, 4410±35 and 3690±35 years BP. The considerable scatter of the dates indicates the significance of erosional processes during marine transgressions. Radiocarbon dates and pollen analyses indicate that in the late Atlantic – early Subboreal periods, the water level of the Vistula Lagoon was about 3 m lower than it is today. The −2 m level was passed no earlier than c. 3500 years ago; the −1 m level was reached around 2000 years ago.