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| Titel |
Determining the controls on δ13C of sedimentary organic matter in Lake Tiefer See (NE Germany) – an integration of sediment cores and monitoring data |
| VerfasserIn |
Nadine Dräger, Ulrike Kienel, Miriam Groß-Schmölders, Birgit Plessen, Achim Brauer |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121725
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| Publikation (Nr.) |
 EGU/EGU2016-556.pdf |
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| Zusammenfassung |
| The carbon isotopic composition of sedimentary organic matter ($\delta$$^{13}$C$\textsubscript{org}$) is widely used in paleoenvironmental studies and commonly considered as proxy for lake productivity. In order to better understand the $\delta$$^{13}$C$\textsubscript{org}$ record of the partly annually laminated (varved) sediment profile of Lake Tiefer See, we complemented measurements from a long sediment core with analyses of short cores from different water depths and sediment trap data. \newline
The $\delta$$^{13}$C$\textsubscript{org}$ signature was determined (i) at 2 cm resolution from a 7.7 m-long continuous sediment record covering the last $\sim$6100 years retrieved from the deepest part of the lake (62 m), (ii) at 1 cm resolution from four short cores (0.5 to 0.9 m long) located at different water depths (20 -- 62 m) and covering at least the last 200 years and (iii) at bi-weekly to monthly resolution from sediment trap material collected at three water depths (5, 12 and 45 m) since march 2012. \newline
We observed that $\delta$$^{13}$C$\textsubscript{org}$ fluctuations are paralleled by changes in varve preservation, as well-varved sections show more negative $\delta$$^{13}$C$\textsubscript{org}$ values compared to non-varved intervals (1 -- 4\permil\ difference; analytical precision $\pm$0.2\permil\). In short cores the negative shift of $\delta$$^{13}$C$\textsubscript{org}$ always appears at the most recent transition from non-varved to well-varved sediments. Depending on the water depth the onset of varve preservation occurred at different times (e.g. AD 1924 in 62 m water depth; AD 1981 in 20 m water depth). Since sediment trap data exhibit similar $\delta$$^{13}$C$\textsubscript{org}$ values of -30\permil\ to -31\permil\ in the entire water column and in the uppermost varved parts of the sediment cores, it is unlikely that the shift in $\delta$$^{13}$C$\textsubscript{org}$ was caused by processes in the water column because this should be seen in all cores at the same time. \newline
Therefore, we suggest that the $\delta$$^{13}$C$\textsubscript{org}$ record of the long sediment core of Lake Tiefer See does not reflect processes in the water column (i.e.\ productivity), but different early diagenetic processes in varved and non-varved sediment. In this study, we discuss possible mechanisms influencing the $\delta$$^{13}$C$\textsubscript{org}$ signature at Lake Tiefer See including the effects of plant detritus, organic matter contents and oxic bottom water conditions. \newline
This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution Analysis --ICLEA-- of the Helmholtz Association; grant number VH-VI-415.\newline |
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