BONE PRETREATMENTS FOR RADIOCARBON DATING - A STUDY INCORPORATING AMS DATING AND ION-BEAM ANALYSIS

Investigations have been carried out to determine whether ion beam analysis can be used to assess the reliability of alkali and gelatin methods used to remove contamination from ancient bone before radiocarbon dating. Organic fractions of moa bones at various stages of pretreatment were radiocarbon dated by AMS and examined by ion beam analysis with 2.5 MeV protons. The resulting X-ray spectra showed the presence of significant amounts of iron in fractions expected to contain humic contamination. AMS measurements confirmed the presence of exogenous carbon in these fractions. A gamma ray peak from N-15 was useful in showing a clear separation of protein from acid-insoluble humic contamination. The combined information from ion beam analysis and AMS dates leads us to conclude that the gelatin method is more effective at removing humic substances than the alkali pretreatment.