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

Abstract

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) PO(4) domain of modern bones. This method was efficient for identifying mineral matter modifications during heating. In particular, the 961, 1022, 1061, and 1092 cm(-1) components show an important wavenumber shift between 120 and 700 degrees C, attributed to the decrease of the distortions induced by the removal of CO(3)(2-) and HPO(4)(2-) ions from the mineral lattice. The so-called 1030/1020 ratio was used to evaluate crystalline growth above 600 degrees 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(-1) 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.