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Titel |
A multi-proxy record of Lateglacial climatic and environmental changes from Lake Mondsee (Upper Austria) |
VerfasserIn |
S. Lauterbach, A. Brauer, P. Dulski, G. Schettler, K. Milecka, M. Hüls, N. Andersen, T. Namiotko, D. L. Danielopol, U. v. Grafenstein |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250026555
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Zusammenfassung |
Within the frame of the ESF EuroCLIMATE project DecLakes (Decadal Holocene and
Lateglacial variability of the oxygen isotopic composition in precipitation over Europe
reconstructed from deep-lake sediments), the sediment record of pre-alpine Lake Mondsee
(Upper Austria) has been investigated with a special focus on the Lateglacial. The use of a
multi-proxy approach, including microfacies analysis, high-resolution μ-XRF element
scanning, stable isotope analyses on valves of benthic ostracods, carbon geochemistry and
analysis of pollen and ostracods enables the identification of major climatic fluctuations
during this period. Furthermore, the parallel sampling strategy allows direct comparison of
sensitivity of different proxies to climatic and environmental changes. The basal
clastic-detrital facies of the profile is dominated by proglacial varves. The gradual onset of
biochemical calcite precipitation is paralleled by a rapid shift in oxygen isotope ratios of
benthic ostracod valves which marks the abrupt warming at the onset of the Lateglacial
Interstadial. However, the allochthonous sediment input from the catchment shows no
rapid shift but a gradual decrease. During the Allerød biozone sedimentation is
dominated by homogeneous endogenic calcite with a very low detrital component. At the
onset of the Younger Dryas cold period a marked decrease in oxygen isotope ratios
within ca. 100 years occurs, followed by a reduction in the amount of endogenic
calcite and the increase of detrital flux with a lag of about 100 years. The clear
vegetational shift towards higher proportions of herbs and Juniperus and the frequency
increase of detrital event layers lag the δ18O signal by about 250 years. In contrast, the
rapid Holocene warming within 20–30 years is well reflected by the parallel δ18O
rise and the establishment of a vegetation adapted to a warmer climate with the
onset of massive calcite precipitation and the cessation of detrital input lagging by
only few decades. The Holocene climatic amelioration is also well reflected by
changes in the ostracod assemblage of the profundal zone from an oligotrophic and
psychrophilic fauna to one which favours benthic substrates with higher organic
input.
This study has been made possible thanks to the support from the European Science
Foundation (EUROCORES Programme EuroCLIMATE, ESF project DecLakes no.
04-ECLIM-FP29) and the National Agencies FWF (Austria, project no. I35-B06), DFG
(Germany) and CNRS (France). |
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