New data about Late Glacial diatoms in Southeastern Baltic

The sediments of shallow basins formed along the coast of the Baltic Ice Lake about 14 500-14 000 cal BP provide a valuable data to reconstruct environmental changes in the Bølling-Allerød Interstadial. Radiocarbon dating and complex lithological and diatom analyzes were performed for the deposits of one of these paleoreservoirs exposed in the Kulikovo section (northern part of the Sambian Peninsula). As a result of studying the deposits aged 14 000 – 13 400 cal BP the total of number of 117 diatom species were identified, oligohalobic indifferent eutrophic benthic species predominated. The most typical species are Pseudostaurosira brevistriata, Staurosirella ovata, Gyrosigma attenuatum, G. acuminatum, Amphora affinis, Epithemia adnata. The obtained data on diatom communities were compared with existing ideas about the Late Glacial diatom flora for this region. This comparison made it possible not only to reconstruct the changes in the ecological conditions of the studied paleoreservoir, but also to identify general and local patterns of diatom communities formed at that time. Thus, in most paleoreservoirs pioneer cosmopolitic epiphytic diatoms of the Fragilariaceae dominate in the Allerød sediments. This indicates fairly calm hydrodynamic conditions. At the same time, in deep paleoreservoirs, despite the Allerød warming, oligotrophic planktonic species dominate in diatom communities and in some sedimentary archives, benthic diatoms capable of living in running water (Gyrosigma spp.) become significant or predominating species.