The Reconstruction of the Formation of Lakes and Wetlands and the Related Sedimentation Processes in the Russian Segment of the Vištytis Upland

The Vistytis Upland is a terminal moraine ridge featuring kame hills. There are numerous lakes and wetlands in its depressions. We collected the samples of bottom sediments from a number of lakes and wetlands located at different altitudes. Using the results of the lithological analysis and radiocarbon dating of the lakes’ bottom sediments and those of a loss-on-ignition test, we identified the main stages of sedimentation. We reconstructed the formation and development of the lakes of the Vistytis Upland from the moment of deglaciation to the present. Two groups of lakes were distinguished by genesis: (a) the lakes formed in the inter-moraine or inter-kame depressions flooded by melt water; (b) the lakes formed in the thermokarst processes. The lakes of the first type are located at altitudes over 170 m and date back to the Younger Dryas, whereas the lakes of the second type are located below 170 m and their formation occurred in the Younger Dryas—the Preboreal. We conclude that the wetlands located west of Lake Vistytis were the bays of the lake in the Late Pleistocene.