Mid-Holocene Littorina Sea transgressions based on stratigraphic studies in coastal lakes of NW Russia

Summary, in English

The mid-Holocene Littorina Sea transgression has been studied in sediment cores from four coastal lakes in NW Russia. The basins are situated in the same drainage system at elevations from 6.9 to 9.2 m a.s.l. Complementary parameters have been applied to identify water-level changes. Chronological models are based on AMS radiocarbon dating of bulk sediments but also wood remains and moss sedge peat has been dated in a few cases. All radiocarbon ages have been calibrated to calendar years BP (cal. BP). Between 8000 and 6000 cal. BP the present-day lakes were in contact with the Littorina Sea and brackish conditions prevailed. The water level was higher than 6 m a.s.l. clearly documented in all four basins. A peak reaching above the level of the uppermost lake (9.2 m a.s.l.) has been dated to ca. 7500 cal. BP. During the high level phase a short lived regress ion/transgression is recognized in all but the uppermost basin. This minor water level fluctuation lasted for a few hundred years around 7000 cal. BP. It is reflected in various parameters in the different basins. Correlations are made with recent studies from Blekinge in southeastern Sweden situated at the 10 m Littorina isobase as the present investigation area. The parallel Littorina Sea history in these two areas seems to confirm a multi-transgression pattern across the southern Baltic Sea.