Late Weichselian environmental changes of the southern Kattegat, Scandinavia, inferred from diatom records

Abstract: The diatom stratigraphy ofa high-resolution sediment core, dated by the tandem accelerator mass pectrometry (AMS) 14C method, records the environmental changes of the Late Weichselian in the southern Kattegat. Five diatom assemblage zones, with two subzones, are distinguished during the Allerod and Younger Dryas chronozones. Fresh water diatoms dominate the assemblages throughout the core. Salinities, particular the surface water salinity during the whole period, were much lower than that of today. Between 11 500 and 11 300 years BP, the occurrence of abundant freshwater planktonic species with only a few brackish water and marine species suggests an environment s rongly affected by a great amount of meltwater discharged from the Baltic Ice Lake via the Oresund Strait. The period from the late Allerod to the early Younger Dryas between 11 300 and 10 600 years BP is characterized by an incursion of cold, saline water into the southern Kattegat with the strongest phase between 11 300 and 10 900 years BP, mirrored by increasing marine diatoms, especially sea ice species. Climatic amelioration took place at about 10 650years BP, which occurred synchronously with a hydrographic change in the southern Kattegat. Relatively warm marine water, mixed with cold marine water, flowed into the Kattegat, although it