A Report on Phase 2 of the Fifth International Radiocarbon Intercomparison (VIRI)

Abstract

ABSTRACT. The Fifth International Radiocarbon Intercomparison (VIRI) continues the tradition of the TIRI (third) and FIRI (fourth) (Scott 2003) intercomparisons and operates in addition to any within-laboratory quality assurance measures as an independent check on laboratory procedures. VIRI is a phased intercomparison; results for the first phase, which employed grain samples, were reported in Scott et al. (2007). The second phase, involving bone samples, is reported here. The third and final phase, which includes samples of peat, wood, and shell, has also been completed and a companion paper appears in these proceedings.Five bone samples were made available and included Sample E: mammoth bone (>5 half-lives); Sample F: horse bone (from Siberia, excavated in 2001; and Samples H and I: whale bones (approximately 2 half-lives). Sample G (human bone) was accessible only to accelerator mass spectrometry (AMS) laboratories because of the limited amount of sample available. More than 40 laboratories participated in Phase 2 and consensus values for the ages were as follows: Sample E = 39,305 14 C yr BP (standard deviation [1 ] = 121 yr); Sample F = 2513 yr BP (1  = 5 yr); Sample G = 969 yr BP (1  = 5 yr); Sample H = 9528 yr BP (1  = 7 yr); and Sample I = 8331 yr BP (1  = 6 yr). Sample G had previously been dated by 4 laboratories and a weighted mean of 934 ± 12 yr BP had been quoted. Sample I had previously been dated at 8335 ± 25 yr BP and Sample H had been dated at 9565 ± 130 yr BP. Results for Sample H and Sample I are in good agreement with the previous results; Sample G results, however, give a value that is significantly older than the previously reported results.

Comparative Decalcification Methods, Radiocarbon Dates, and Stable Isotopes of the VIRI Bones

“…The 14 C dates reported in this paper were produced as part of the VIRI intercomparison. These dates and the consensus dates derived from that study (Scott et al 2010) are reported in Table 1 and Figure 1.…”

“…As with many tests of methods development, the question of the "correct" answer has been at issue, and the publication of the VIRI data (Scott et al 2010) provides a robust comparator to assess decalcification methods. Additional isotopic and elemental data (ô 13 C, δ 15 Ν, and δ 18 0) from the VIRI bone samples provide additional information on the condition of the extracted collagen.…”

“…The method of collagen preparation was not prescribed in the VIRI comparison; thus, the VIRI results stand as a comparison of laboratory methods used in isolating collagen as well as post-isolation measurement of 14 C content in the samples. More than 60 sets of 14 C dates from 42 laboratories, as well as consensus values, were published by Scott et al (2010).…”

“…The Fifth International Radiocarbon Comparison (VIRI) provided a suite of 5 bone samples with consensus ages ranging from 969 to 39,305 14 C yr BP (Scott et al 2010). These bones were used herein in a comparison of decalcification methods using either HCl or EDTA to produce collagen, and the results demonstrate age concordance between both preparation methods and the VIRI consensus values.…”

Selection and Treatment of Data for Radiocarbon Calibration: An Update to the International Calibration (IntCal) Criteria

“…These standards and reference materials span both the applied 14 C age range and the chemical and biological composition range of typical samples. A summary of the intercomparisons organized within the 14 C dating community can be found in Scott (2003) and Scott et al (2010a). The results from the most recent intercomparisons have indicated that laboratories are in general providing accurate results, but have pointed to variation in the results beyond that described by the quoted errors.…”