Centre de datation par le Radiocarbone

De façon régulière la communauté scientifique internationale du radiocarbone procède à une intercomparaison de résultats sur une série d’échantillons identiques.
Nous en sommes à la cinquième ( VIRI), la sixième sera publiée en 2016 ( SIRI)

A Report on Phase 1 of the 5th International Radiocarbon Intercomparison (VIRI)
E Marian Scott, Gordon T Cook, Philip Naysmith, Charlotte Bryant, David O’Donnell

Abstract

The Fifth International Radiocarbon Intercomparison (VIRI) continues the tradition of the TIRI (third) and FIRI (fourth) intercomparisons (Scott 2003) and operates as an independent check on laboratory procedures in addition to any within-laboratory procedures for quality assurance. VIRI is a 4-yr project, with the first suite of samples (grain) sent out in September 2004 and the second suite (bone) sent out in December 2005. Further stages will include samples of peat, wood, and shell with a range of ages. The 4 grain samples included 2 samples (A and C) of barley mash (20 g for radiometric analysis and 2 g for AMS), a grain (barley) byproduct from the manufacture of Glengoyne malt whiskey. The 2 remaining charred grain samples (B and D) were from excavations at Beth Saida and Tel Hadar, respectively (10 g for radiometric analysis and 4 seeds for AMS) and were provided by Elisabetta Boaretto of the Weizmann Institute. Consensus values for samples A and C are 109.2 (standard deviation [1 σ] = 2.73) and 110.6 pMC (1 σ = 2.48), and 2805 (1 σ = 162.7) and 2835 BP (1 σ = 190.8) for samples B and D, respectively. Sample A is a new sample that was collected in 2001, while sample C was used in the FIRI trial as samples G & J (consensus value 110.7 pMC) and was collected in 1998. The expected ages (on archaeological grounds) of samples B and D are 2800 BP and 28502900 BP, respectively. The second suite of samples comprises bone, ranging in age from Medieval to close to background, and was distributed in December 2005. Samples for both radiometric and AMS laboratories include E : mammoth bone (>5 half-lives) ; F : horse bone (from Siberia, excavated in 2001) ; and H, I : whalebone. Finally, sample G (human bone) was only for AMS laboratories. Some of the issues related to using bone in a laboratory intercomparison will be discussed.

A Report on Phase 2 of the Fifth International Radiocarbon Intercomparison (VIRI)
E Marian Scott, Gordon T Cook, Philip Naysmith

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 14C yr BP (standard deviation [1 σ] = 121 yr) ; Sample F = 2513 yr BP (1 σ = 5 yr) ; Sample G = 969 yr BP (1 σ = 5 yr) ; Sample H = 9528 yr BP (1 σ = 7 yr) ; and Sample I = 8331 yr BP (1 σ = 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.

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