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Geochronology Advances in geochronological science
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https://doi.org/10.5194/gchron-2019-19
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2019-19
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 17 Dec 2019

Submitted as: research article | 17 Dec 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geochronology (GChron).

Miniature radiocarbon measurements (< 150 μg C) from sediments of Lake Żabińskie, Poland: effect of precision and dating density on age-depth models

Paul D. Zander1, Sönke Szidat2, Darrell S. Kaufman3, Maurycy Żarczyński4, Anna I. Poraj-Górska4, Petra Boltshauser-Kaltenrieder5, and Martin Grosjean1 Paul D. Zander et al.
  • 1Institute of Geography & Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland
  • 2Department of Chemistry and Biochemistry & Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland
  • 3School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA
  • 4Faculty of Oceanography and Geography, University of Gdańsk, Gdańsk, 80-309, Poland
  • 5Institute of Plant Sciences &Oeschger Centre for Climate Change Research, University of Bern, Bern, 3013, Switzerland

Abstract. The recent development of the MIni CArbon DAting System (MICADAS) allows researchers to obtain radiocarbon (14C) ages from a variety of samples with miniature amounts of carbon (< 150 μg C) by using a gas ion source input that bypasses the graphitization step used for conventional 14C dating with accelerator mass spectrometry (AMS). The ability to measure smaller samples, at reduced cost compared with graphitized samples, allows for greater dating density of sediments with low macrofossil concentrations. In this study, we use a section of varved sediments from Lake Żabińskie, NE Poland, as a case study to assess the usefulness of miniature samples from terrestrial plant macrofossils for dating lake sediments. Radiocarbon samples analyzed using gas-source techniques were measured from the same depths as larger graphitized samples to compare the reliability and precision of the two techniques directly. We find that the analytical precision of gas-source measurements decreases as sample mass decreases, but is comparable with graphitized samples of a similar size (approximately 150 μg C). The age uncertainty is consistently less than 150 years (uncalibrated 1σ) for samples larger than 40 μg C. The reliability of 14C ages from both techniques is assessed via comparison with a best-age estimate for the sediment sequence, which is the result of an OxCal V-sequence that integrates varve counts with 14C ages. No bias is evident in the ages produced by either gas-source input or graphitization. None of the 14C ages in our dataset are clear outliers; the 95 % confidence intervals of all 48 calibrated 14C ages overlap with the median best-age estimate. The effects of sample mass (which defines the expected analytical age uncertainty) and dating density on age-depth models are evaluated via simulated sets of 14C ages that are used as inputs for OxCal P-sequence age-depth models. Nine different sampling scenarios were simulated in which the mass of 14C samples and the number of samples were manipulated. The simulated age-depth model results suggest that the lower analytical precision associated with miniature samples can be compensated for by increased dating density. The data presented in this paper can improve sampling strategies and can inform expectations of age uncertainty from miniature radiocarbon samples as well as age-depth model outcomes for lacustrine sediments.

Paul D. Zander et al.
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Paul D. Zander et al.
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Data tables - Lake Zabinskie Geochronology P. D. Zander, S. Szidat, M. Grosjean, D. S. Kaufmann, P. Boltshauser-Kaltenrieder, M. Żarczyński, and A. Poraj-Górska https://doi.org/10.7892/boris.134606

Paul D. Zander et al.
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Short summary
Recent technologic advances allow researchers to obtain radiocarbon ages from smaller samples than previously possible. We investigate the reliability and precision of radiocarbon ages obtained from miniature (11–150 μg C) samples of terrestrial plant fragments taken from sediment cores from Lake Zabinskie, Poland. We further investigate how sampling density (the number of ages per 1000 years) and sample mass (which is related to age precision) influence the performance of age-depth models.
Recent technologic advances allow researchers to obtain radiocarbon ages from smaller samples...
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