Programmes > Par auteur > Ghaleb Bassam

The reconstruction of the unknown U-uptake history in the dental tissues has always been a source of uncertainty for ESR/U-Th dating and thus for dose rates reconstruction. Since the introduction of the US-ESR model by Grun et al. (1988), which takes into account 234U/238U and 230Th/234U activity ratios for the determination of an uptake parameter (the “p-value”), the accuracy of the age estimates was improved. However, the limit of the US-ESR model is reached when uranium leaching is evidenced in at least one of the dental tissues. In order to overcome this limit, Shao et al. (2012) proposed a new model, called Accelerating Uptake (AU-ESR), which allows to model the evolution of U-uptake as a function of time in tissues which underwent leaching processes.

We present ESR/U-Th age results obtained on Equus teeth from the Middle Palaeolithic cave site of Sainte-Anne I (Polignac, Haute-Loire, France) (Raynal, 2007). Results suggest that the dental tissues from five out of six teeth underwent U-leaching during burial, preventing the calculation of US-ESR ages. Minimum ages (Early Uptake, EU-ESR) were thus calculated and compared to AU-ESR modelled ages. The difference between mean EU and AU ages ranges from 2 to 22%, indicating that U-loss in some of the dental tissues can have a significant impact on the age estimates. Available biochronological and climatochronological data point out a MIS6 chronology. However, previous ESR ages (Rhodes, 2007) and all of the EU, US and AU ages obtained in this study fall within MIS5. ESR/U-Th ages range from 118 ± 14 ka (AU) to 80 ± 7 ka (US), spanning the entirety of MIS5, and allow to attribute the sequence to the beginning of the Upper Pleistocene.

References

Grün, R., Schwarcz, H.P., Chadam, J., 1988. ESR dating of tooth enamel: Coupled correction for U-uptake and U-series disequilibrium. International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 14, 237-241.

Raynal, J.-P. (dir), 2007. Sainte-Anne I, Sinzelles, Polignac, Haute-Loire. Le Paléolithique moyen de l'unité J1, CDERAD ed., Les dossiers de l'Archéo-Logis, 3, Goudet, 265 p.

Rhodes, E.J., 2007. Initial Electron Spin Resonance dating results, in: Raynal, J.P. (dir), Sainte-Anne 1, Sinzelles, Polignac, Haute-Loire. Le Paléolithique moyen de l'unité J1. CDERAD ed., Les dossiers de l'Archéo-Logis, 3, Goudet, pp. 43-46.

Shao, Q., Bahain, J.-J., Falguères, C., Dolo, J.-M., Garcia, T., 2012. A new U-uptake model for combined ESR/U-series dating of tooth enamel. Quaternary Geochronology 10, 406-411.