Comparative14C and OSL dating of loess-paleosol sequences to evaluate post-depositional contamination ofn-alkane biomarkers

Authors Organisations
  • Michael Zech(Author)
    Martin-Luther-Universität Halle-Wittenberg
    University of Bayreuth
  • Sebastian Kreutzer(Author)
    University of Bayreuth
    Giessen University
  • Roland Zech(Author)
    ETH Zurich
  • Tomasz Goslar(Author)
    Poznan Radiocarbon Laboratory
  • Sascha Meszner(Author)
    TU Dresden
  • Cameron McIntyre(Author)
    ETH Zurich
  • Christoph Häggi(Author)
    ETH Zurich
  • Timothy Eglinton(Author)
    ETH Zurich
  • Dominik Faust(Author)
    TU Dresden
  • Markus Fuchs(Author)
    Giessen University
Type Article
Original languageEnglish
Pages (from-to)180-189
Number of pages10
JournalQuaternary Research
Volume87
Issue number1
DOI
Publication statusPublished - 01 Jan 2017
Externally publishedYes
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Abstract

There is an ongoing controversial discussion as to whether n-alkane lipid biomarkers—and organic matter of loess in general—reflect a synsedimentary paleoenvironmental/climate signal or whether they are significantly affected by postdepositional “contamination,” for example related to root and rhizomicrobial activity. In order to address this issue at our study site (the Middle to Late Weichselian loess-paleosol sequence Gleina in Saxony, Germany), we determined and compared radiocarbon ages of bulk n-alkanes and sedimentation ages, as assessed by optically stimulated luminescence (OSL) dating. The bulk n-alkanes of the four dated samples yielded calibrated 14C ages ranging from 24.1 to 49.7 cal ka BP (95.4% probability ranges). While the three uppermost n-alkane samples are well within the range or even slightly older than the OSL-inferred sedimentation ages, the lowermost n-alkane sample is slightly younger than the OSL ages. There is hence little or no evidence at our study site for n-alkanes in loess-paleosol sequences being significantly “contaminated” by deep subsoil rooting or microbial processes. We propose a 14C isotope mass balance calculation for estimating such contaminations quantitatively. Radiocarbon dating of bulk n-alkanes might have great potential for Quaternary research, and we encourage further comparative 14C and OSL studies