What lies behind radiocarbon intercomparisons and the design of the new intercomparison, GIRI?

Abstract

Given the complexity of the radiocarbon dating process, the diversity of materials being dated, the continued technical developments, GIRI (the Glasgow international radiocarbon intercomparison) is the next development of the series of intercomparisons to support continuing quality assurance. GIRI has been designed to continue this programme and to meet a number of objectives, including the most fundamental one, to provide an independent assessment of the analytical quality of the laboratory/measurement and an opportunity for a laboratory to participate and improve (if needed). The principles that we followed in the creation of GIRI are to provide. A) A series of unrelated individual samples, spanning the dating age range B) Some samples linked to earlier intercomparisons to allow traceability C) Some known age samples, to allow independent accuracy checks D) A small number of duplicates, to allow independent estimation of laboratory uncertainty E) Two categories of samples, bulk and individual to support laboratory investigation of variability. All of the GIRI samples are natural (wood, peat and grain), some are known age, and overall their age spans approx. >40,000 BP to modern. Ultimately, we wish to define consensus values for all the samples and a quantified uncertainty supporting a more in-depth evaluation of laboratory performance and variability.