Screening in situ bone and teeth preservation by ATR-FTIR mapping

Abstract

Bones and teeth are highly hierarchically structured and hererogeneous materials, and post mortem processes can reinforce this heterogeneity. It is therefore important to consider this heterogeneity to better understand diagenetic processes. In this study, ATR-FTIR mapping was applied to several heated and un-heated archaeological samples, and to similar modern references in order to test the potential of this method. ATR-FTIR mapping can provide spatially resolved information on alteration state of mineral and organic matter. This technique allowed to describe the spatial distribution of organic and mineral matter preservation in unheated Palaeolithic bones (Bize-Tournal, France) characterized by a better preservation in the centre of the cortical bone. Spatial variations in the chemical composition of an archaeological heated bone (Abri Pataud, France) compared to a modern reference suggested taphonomical uptake of carbonate in the most external part. This pattern could correspond to a process of re-carbonatation of the calcined mineral matter in the outermost part of the sample due to combustion in a CO2 rich atmosphere. FTIR-ATR is a powerful tool that allows for identifying and characterizing local heterogeneities in bone preservation. This technique open new prospects to reconstruct the taphonomical history of ancient samples.