Keywords:bone, carbonate hydroxyapatite, radiocarbon dating
Bones are one of the most important materials for archaeological and paleo-environmental dating because they can directly provide absolute dates themselves. Bone collagen, which contains bone protein that is less susceptible to chemical weathering, is commonly used for 14C dating, but it sometimes has lost organic protein due to post-depositional chemical alternation and diagenesis, resulting in impossibility of 14C dating. For the bones remaining no organic component, carbonate hydroxyapatite, an inorganic component, is useful for 14C-measurement. However, the inorganic component in bones can easily be altered by acidic soil, and it has been considered to be unsuitable for 14C dating. Recently, meanwhile, it is reported that 14C dating using carbonate hydroxyapatite is possible for cremation bones heated at a high temperature (>600℃). The objective of this study is to examine the possibility of 14C dating using carbonate hydroxyapatite in cremated bones. The samples used were cremated bones in a funerary urn, which are considered to be remains of Jokei, a Buddhist monk (AD 1155-1213). The bones had been confirmed to be burned at high temperature, judged from the IR spectra and XRD patterns. The carbonate hydroxyapatite in six bone fragments showed 14C dates of 1155-1280 cal AD, which is similar with the supposed age. The result indicates that 14C dating using carbonate hydroxyapatite is effective when the bone sample was enough heated and well-preserved after deposition.