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

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 sigma] = 121 yr); Sample F = 2513 yr BP (1 sigma = 5 yr); Sample G = 969 yr BP (1 sigma = 5 yr); Sample H = 9528 yr BP (1 sigma = 7 yr); and Sample I = 8331 yr BP (1 sigma = 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.