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Simple, Rapid, and Cost Effective: A Screening Method for 14C Analysis of Small Carbonate Samples

Published online by Cambridge University Press:  09 February 2016

Shari L Bush ,
Guaciara M Santos ,
Xiaomei Xu ,
John R Southon ,
Nivedita Thiagarajan ,
Sophia K Hines  and
Jess F Adkins
Shari L Bush
Affiliation:
Department of Earth System Science, University of California, Irvine, California 92697–3100, USA
Guaciara M Santos*
Affiliation:
Department of Earth System Science, University of California, Irvine, California 92697–3100, USA
Xiaomei Xu
Affiliation:
Department of Earth System Science, University of California, Irvine, California 92697–3100, USA
John R Southon
Affiliation:
Department of Earth System Science, University of California, Irvine, California 92697–3100, USA
Nivedita Thiagarajan
Affiliation:
California Institute of Technology, Pasadena, California 91125, USA
Sophia K Hines
Affiliation:
California Institute of Technology, Pasadena, California 91125, USA
Jess F Adkins
Affiliation:
California Institute of Technology, Pasadena, California 91125, USA
*
2Corresponding author. Email: [email protected].
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Abstract

We have developed a simple, rapid method to screen carbonates for survey applications, which provides radiocarbon dates with decreased precision at lower cost. The method is based on previous work by Longworth et al. (2011) and involves mixing pulverized CaCO3 with Fe powder, followed by pressing into aluminum target holders for direct 14C accelerator mass spectrometry (AMS) measurements. An optimum beam current averaging ∼10% of those produced by >0.7 mg C graphite targets was obtained for carbonate samples of 0.3–0.5 mg (0.04–0.06 mg C). The precision of the method was evaluated by measuring triplicates of 14C reference materials, as well as by comparing results from this rapid method with results from high-precision AMS measurements on graphite (typically 0.2–0.3%). Measurement reproducibility was ∼1.8% (1σ) for samples <10 ka BP, and it increased drastically for older samples. However, t tests on paired samples resulted in p values greater than 0.05, indicating a good correlation between this survey method and the conventional one. An average blank (calcite) of 0.0075 Fm (∼39 ka BP) was achieved. The simplicity of the technique allowed us to process and measure 72 deep-sea coral samples in less than 25 hr.

Type
Articles
Information
Radiocarbon , Volume 55 , Issue 2: Proceedings of the 21st International Radiocarbon Conference (Part 1 of 2) , 2013 , pp. 631 - 640
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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References

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