Towards a Better Understanding of Alteration Phenomena of Archaeological Bone by a Closer Look at the Organic/Mineral Association at Micro- and Nanoscale. Preliminary Results on Neolithic Samples from Chalain Lake Site 19, Jura, France

Abstract

In this paper we present the extension of existing analytical schemes for the precise evaluation of archaeological bone preservation states. The new methodological developments concerning the study of the morphological and structural features of archaeological bones at micro- and nanoscale are emphasized in order to elucidate fine diagenetic modifications and to better understand the underlying alteration mechanisms. A combination of synchrotron X-ray microtomography, infrared micro-spectroscopy imaging and quantitative scanning small-angle X-ray scattering (sSAXS) imaging allowed studying micromorphological changes and the distribution of the organic and mineral components of bone at a histological level. Transmission electron microscopy gives precise information on changes of apatite crystal dimensions, orientations, periodicity of collagen fiber arrangement and crystal distributions within the fibers in archaeological bone. It allows establishing criteria to evaluate more precisely the preservation state of archaeological bone material with respect to modern references. The potential of these methods is highlighted on the basis of the study of some macroscopically well preserved archaeological bone samples from the Chalain lake station 19, Neolithic period, Jura, France. The investigations allowed a differentiation in preservation state between these samples and the postulation of an alteration sequence in such humid chalk-rich burial environments.