Late Quaternary Biostratigraphy of Sediments of the Southeastern Baltic Sea

University dissertation from Uppsala : Acta Universitatis Upsaliensis

Abstract: This thesis presents Late Quaternary biostratigraphy in the SE Baltic Sea, based on palynological data from fifteen sediment cores.An objective subdivision of the cores has been achieved by numerical zonation. Ordination has revealed a succession of pollen spectra that can be used for biostratigraphic correlation across the region. Seven regional pollen assemblage zones have been identified and described. Their comparison with biostra6graphic units on adjacent land, confirmed by radiocarbon dates and supported by diatom composition, has provided a chronology.A consistent picture of the Late Quaternary biostratigraphy of the area has been constructed, despite the approximations and uncertainties involved. The relative position of most biostratigraphical and lithological limits within the cores has been determined.The most prominent change during postglacial time in the SE Baltic Sea occurred at the Boreal-Atlantic transition. It is evident in the results of pollen analysis and ordination, statistically significant in all studied cores, and supported by dating. This transition could be considered as a marker and used for correlation. The reliability of other transitions (Preboreal-Boreal, Younger Dryas-Preboreal and Atlantic-Subboreal) varies depending on the composition of pollen spectra and sedimentation conditions at individual sites. The oldest (Allerød) and youngest (Subatlantic) sediments in the cores from the study area can be delimited only tentatively.The obtained results are valid foremost for the SE Baltic Sea. However, they display the general trends and main features of postglacial history of the Baltic basin.Application of numerical zonation and principal components analysis to biostratigraphical investigations of sediments from the SE Baltic Sea has provided an effective tool for an integration of earlier palynological data with results of modem analysis and available chronology.

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