Multifactorial approach to describe early diagenesis of bones: The case study of the Merovingian cemetery of Saint-Linaire (France)

Abstract

The excavation of the Merovingian cemetery of Saint-Linaire (France) was an opportunity to describe the completeness of the tombs preserved from soil erosion. An anthropobiological study was carried out on the osteological material and the different categories of graves. On the basis of a complete archaeo-anthropological corpus we have undertaken an analysis of the differential preservation of the bones according to the different archaeobiological parameters such as the type of bone, the individual age but also the type of grave such as earthen graves, coffin, or sarcophagus.In order to establish whether and how funerary practices had impacted the early diagenesis of the bones, FTIR was used to investigate the carbonate and fluoride content of the bones, and the infra-red splitting factor (SF), while XRD analysis was performed to estimate the crystallinity index (CI). In addition, the micro, macro and total porosity of the bones were measured by water adsorption, and bone carbon and nitrogen amounts were obtained by EA-IRMS. These diagenetic variables were analysed with regards to environmental (grave filling: humus, calcareous, clay), cultural (type of grave) and biological (mature versus immature individuals) factors. While there is a tendency of a better preservation of the skeletons in humus, and of juvenile bones to show less post-mortem alteration than the adult skeletons, the most important factor which determines the fate of the skeleton is the type of bone, with a preferential preservation of the ribs at Saint-Linaire.