ISSN 1392-110X
ISSN 2029-056X (online)
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2007 m. Nr. 1
Environmental changes in the Fårö Deep (the Baltic
Sea): lithology of sediments and diatom flora
Egidijus TRIMONIS, GIEDRĖ VAIKUTIENĖ
The Fårö Deep is situated north-east of the Gotland Island dividing the central part of the Baltic Sea. The sediment record shows all main stages of the Baltic Sea evolution in the Late Glacial and Holocene. This is verified by lithostratigraphic data and results of diatom flora analysis in the bottom sediment core PSh-5129 from the Fårö Deep. The homogeneous brownish grey clay at the bottom of the core marks the end of the glaciation when the Fårö Deep was part of a deep periglacial lake. The subsequently deposited clays with black interlayers and patches of Fe monosulphides underlying grey and greenish grey mud reflect dramatic changes in the environmental conditions. Analysis of sediment composition and diatom complexes confirmed that the alternation of lacustrine and marine conditions in the Fårö Deep in the Holocene followed the general evolution patterns of the Baltic Sea, yet with certain specific features. Due to a sophisticated water mass circulation during the Yoldia Sea stage, the marine influence was inconspicuous. Contrary to many sediment cores analysed from other parts of the Baltic Sea, the study sediment core contains only sparse and untypical diatom flora of the Litorina Sea.
Keywords: bottom sediments, lithostratigraphy, diatom flora, lacustrine and marine environments, Baltic sea
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