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

Zander, Paul D.; Szidat, Sönke; Kaufmann, Darrell S.; Żarczyński, Maurycy; Poraj-Górska, Anna I.; Boltshauser-Kaltenrieder, Petra; Grosjean, Martin (2020). Miniature radiocarbon measurements (< 150 μg C) from sediments of Lake Żabińskie, Poland: effect of precision and dating density on age-depth models. Geochronology, 2(1), pp. 63-79. Copernicus Publications 10.5194/gchron-2-63-2020

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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). For samples larger than 40 µg C and younger than 6000 BP, the uncalibrated 1σ age uncertainty is consistently less than 150 years (±0.010 F14C). 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 models 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.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Paleolimnology
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Departement of Chemistry and Biochemistry
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Palaeoecology
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

Graduate School:

Graduate School of Climate Sciences

UniBE Contributor:

Zander, Paul David; Szidat, Sönke; Kaufmann, Darrell Scott; Boltshauser-Kaltenrieder, Petra and Grosjean, Martin

Subjects:

500 Science > 580 Plants (Botany)
500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry
500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel

ISSN:

2628-3719

Publisher:

Copernicus Publications

Funders:

[4] Swiss National Science Foundation
[UNSPECIFIED] Polish National Science Centre

Language:

English

Submitter:

Paul David Zander

Date Deposited:

29 Jan 2020 14:54

Last Modified:

26 May 2020 11:23

Publisher DOI:

10.5194/gchron-2-63-2020

Related URLs:

Uncontrolled Keywords:

radiocarbon, MICADAS, lake sediments, OxCal, age-depth modeling

BORIS DOI:

10.7892/boris.139543

URI:

https://boris.unibe.ch/id/eprint/139543

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