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| Titel |
n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary? |
| VerfasserIn |
Michael Zech, Sebastian Kreutzer, Tomasz Goslar, Sascha Meszner, Tobias Krause, Dominik Faust  , Markus Fuchs |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250083692
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| Zusammenfassung |
| There is an ongoing discussion whether n-alkane biomarkers – and organic matter (OM) from loess in general – reflect a syn-sedimentary paleoenvironmental and paleoclimate signal or whether they are significantly a post-sedimentary feature contaminated by root-derived OM (Zech et al., 2012, 2013; Wiesenberg and Gocke, 2013). We present first radiocarbon data for the n-alkane fraction of lipid extracts and for the first time luminescence ages for the Middle to Late Weichselian loess-paleosol sequence of Gleina in Saxony, Germany. Comparison of these biomarker ages with sedimentation ages as assessed by optically stimulated luminescence (OSL) dating shows that one n-alkane sample features a syn-sedimentary age (14C: 29.2 ± 1.4 kyr calBP versus OSL: 27.3 ± 3.0 kyr). By contrast, the 14C ages derived from the other n-alkane samples are clearly younger (20.3 ± 0.7 kyr calBP, 22.1 ± 0.7 kyr calBP and 29.8 ± 1.4 kyr calBP) than the corresponding OSL ages (26.6 ± 3.1 kyr, 32.0 ± 3.5 kyr and 45.6 ± 5.3 kyr). This finding suggests that a post-sedimentary n-alkane contamination presumably by roots has occurred.
In order to estimate the post-sedimentary n-alkane contamination more quantitatively, we applied a 14C mass balance calculation based on the measured pMC (percent modern carbon) values, the calculated syn-sedimentary pMC values and pMC values suspected to reflect likely time points of post-sedimentary contamination (modern, last decades, 3 kyr, 6 kyr and 9 kyr). Accordingly, modern and last decadal root-contamination would account for up to 7%, a 3 kyr old root-contamination for up to 10%, and an Early and Middle Holocene root-contamination for up to 20% of the total sedimentary n-alkane pool.
We acknowledge and encourage that these first radiocarbon results need further confirmation both from other loess-paleosol sequences and for different biomarkers, e.g. carboxylic acids or alcohols as further lipid biomarkers.
Zech, M., Kreutzer, S., Goslar, T., Meszner, S., Krause, T., Faust, D. and Fuchs, M., 2012: Technical Note: n-Alkane lipid biomarkers in loess: post-sedimentary or syn-sedimentary? Biogeosciences Discussions 9, 9875-9896.
Wiesenberg, G. and Gocke, M., 2013. Comment of G. Wiesenberg and M. Gocke on “Reconstruction of the late Quaternary paleoenvironments of the Nussloch loess paleosol sequence, Germany, using n-alkane biomarkers. Quaternary Research, in press.
Zech, M., Rass, S., Buggle, B., Löscher, M. and Zöller, L.. 2013. Response to the comment of G. Wiesenberg and M. Gocke on “Reconstruction of the late Quaternary paleoenvironments of the Nussloch loess paleosol sequence, Germany, using n-alkane biomarkers”. Quaternary Research, in press. |
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