Characterization of archaeological burnt bones: contribution of a new analytical protocol based on derivative FTIR spectroscopy and curve fitting of the ν 1 ν 3 PO4 domain

Derivative Fourier transform infrared (FTIR) spectroscopy and curve fitting have been used to investigate the effect of a thermal treatment on the nu 1 nu 3 PO4 domain of modern bones. This method was efficient for identifying mineral matter modifications during heating. In particular, the 961, 1022, 1061, and 1092 cm components show an important wavenumber shift between 120 and 700 deg C, attributed to the decrease of the distortions induced by the removal of CO3 and HPO4 ions from the mineral lattice. The so-called 1030/1020 ratio was used to evaluate crystalline growth above 600 deg C. The same analytical protocol was applied on Magdalenian fossil bones from the Bize-Tournal Cave (France). Although the band positions seem to have been affected by diagenetic processes, a wavenumber index-established by summing of the 961, 1022, and 1061 cm peak positions-discriminated heated bones better than the 1030/1020 ratio, and the splitting factor frequently used to identify burnt bones in an archaeological context. This study suggest that the combination of derivative and curve-fitting analysis may afford a sensitive evaluation of the maximum temperature reached, and thus contribute to the fossil-derived knowledge of human activities related to the use of fire.