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| Titel |
Submerged terrestrial landscapes in the Baltic Sea: Evidence from multiproxy analyses of sediment cores from Fehmarnbelt |
| VerfasserIn |
Dirk Enters, Steffen Wolters, Katharina Blume, Martin Segschneider, Andreas Lücke, Martin Theuerkauf, Thomas Hübener |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133866
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| Publikation (Nr.) |
 EGU/EGU2016-14525.pdf |
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| Zusammenfassung |
| Five sediment cores were taken from the southern part of the Fehmarn Belt (Baltic Sea)
in the context of an environmental impact study for the intended fixed traverse
between Germany and Denmark. The lithologies of the 8m long cores reveal dramatic
changes in sedimentary environments which reflect the early Holocene history of the
southern Baltic Sea. A succession of terrestrial, semiterrestrial and limnic facies
from glacial sediments to peat, lacustrine/estuarine deposits and finally marine
sediments document the interplay of eustatic sea level rise and isostatic rebound,
which finally lead to the establishment of marine conditions during the Littorina
transgression. An age control of the observed changes was established by dating over 50
C-14 samples of different fractions. During the Lateglacial minerogenic varves
with thicknesses of several centimeters verify the existence of a proglacial lake in
the Fehmarnbelt. Peat development started around 11.250 cal. BP and terminated
ca. 10.600 cal. BP which is roughly contemporaneous with the end of the Yoldia
Phase in the central Baltic Sea. The oldest peat layers consist of undecomposed
sedges and reed. Woody remains of willows appear not before 10.700 cal BP and
indicate a stagnant or slowly decreasing water table. This semi-terrestrial phase is
followed by a shallow inland lake which existed until the Littorina transgression
around 8.300 cal. BP. Initially the lacustrine sediments exhibit high C/N ratios,
low low δ13Corg values and contain numerous wood fragments as well as other
botanical macro remains. This indicates shallow conditions close to the lake shore.
Later, the occurrence of planktonic diatom species such as Aulacoseira ambigua
suggest greater water depths. We did not find any indications of the often postulated
catastrophic outburst of the Ancylus Lake via Fehmarnbelt and the Great Belt into
the North Sea. Likewise, XRF scanning does not show conspicuous peaks in Ti
or K which would have been deposited during floods in old river channels of the
hypothesized Dana River. Instead diatom assemblages indicate rather calm conditions.
Between 9.850 and 8.900 cal. BP carbonate rich sediments were deposited under now
shallow water conditions consisting of autochthonous carbonates, mollusk shells
(especially Bithynia tentaculata) and oogonia of charophytes. The diatom record shows
first indications of slightly brackish conditions starting ca. 10.300 cal. BP with the
appearance of Mastogloia smithii which is about 2000 years older than the Littorina
transgression dated in our record to around 8.300 cal. BP. This marine transgression finally
inundated the inland lake and caused a rise of the water level of more than 20 m. |
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