RADIOCARBON AGE ASSESSMENT OF A NEW, NEAR BACKGROUND IAEA C-14 QUALITY ASSURANCE MATERIAL

The C-14 Quality Assurance Programme coordinated by the IAEA (Rozanski et al. 1992) prepared a set of five new intercomparison materials, in cluding 40-50 ka old subfossil wood excavated from New Zealand peat bo gs (IAEA C-4 standard). Statistical analysis of 79 C-14 measurements m ade on the wood indicated considerable variation in the results, with a marked skewness toward more modern values. The wide range of results and the possibility of inhomogeneity within the standard prompted the recovery and analysis of replacement material. The new subfossil wood sample is kauri (Agathis australis), at least 50 ka old, excavated fr om a swamp in Northland. It is in the form of a single plank, 6 m long , weighing 80 kg. It will be forwarded to the IAEA in Vienna for milli ng and distribution. Subsamples were obtained from both ends of the pl ank and analyzed by six laboratories. We present here the results of t hese analyses and compare them with the previous IAEA intercalibration results for the C-4 standard.