EPR Dating of Hydroxyapatite from Fossil Bones. Transient Effects, after γ and UV Irradiation

M. Wenckaa, S.K. Hoffmanna and H. Hercmanb aInstitute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland bInstitute of Geological Sciences, Polish Academy of Sciences, Twarda 51, 00-818 Warszawa, Poland

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Received: 24 04 2005;

ESR measurements at room temperature have been performed on fossil bones of cave bear (from Magurska Cave of the Tatra Mountains) and mammoth (from Dniestr River). Various paramagnetic centres related to defects in hydroxyapatite were identified. The ESR spectrum is dominated by Mn2+ lines and free radical centres CO2-, and CO3-. Suitability of various EPR lines for the dating was evaluated. The spectra are affected by γ-ray and UV irradiation which produce new relatively unstable (transient) radical centres. From their decay curves we determined the delay period (waiting time) between irradiation and ESR dating measurements. For γ-rays the period is about 15 days and depends on the chosen ESR line. UV generates mainly surface O- centres which decay practically after a few days. The ESR dating of the bear bones using an additive dose method given the age t = 21.7 kiloyears (ky), whereas from radionuclide Th/U method t= 34 ky and from radiocarbon 14C method t>33.1 ky.

DOI: 10.12693/APhysPolA.108.331 PACS numbers:76.30.-v, 65.90.+i