Tests for Diagenesis in Tooth Enamel: ESR Dating Signals and Carbonate Contents

We have tested whether tooth enamel might be altered during burial by focusing on the carbonate content and electron spin resonance (ESR) signals used for dating. Since oxidized carbon atoms (CO2or CO3moieties) in the apatite lattice give rise to the ESR dating signal as a function of absorbed radiation dose, inward or outward carbonate mobility would induce changes in the radiation sensitivity of the ESR dating signal. We used manometry and Fourier transform infra-red spectroscopy to study carbonate in 11 fossil and five modern tooth enamels from horse, cow, hippopotamus, rhinoceros and mammoth. We have shown that ungulate tooth enamel exhibits a narrow range of both carbonate content (4·5 to 5·1wt%) and ESR signal intensity (at 300Gy radiation dose). These characteristics are true both for modern and most fossil samples ranging in age up to several hundred thousand years old. Evidence for possible diagenesis was found only for two samples, consisting of fragments of enamel which exhibited anomalous high and low carbonate contents (and ESR signal sizes).