A multi-analytical study of bone diagenesis: the Neolithic site of Bercy (Paris, France)

Bone remains play an important role in archaeology as a source of information about the past. However, they alter over time. Alteration occurs at all scales from the macroscopic to nanoscopic level. The evaluation of information extracted on palaeodiets, ages and palaeoclimates from their chemical and isotopic composition requires the study of diagenetic modifications by means of different complementary analytical methods. Diagenetic parameters that quantify the post-mortem alteration of bone are bone histology, porosity, protein content, crystallinity of bone apatite, carbonate content, enrichment and leaching of chemical species in general. The investigation of these features can be performed by a combination of complementary elemental and structural analyses (particle-induced x-ray emission, particle-induced gamma-ray emission, scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDX), electron microprobe, x-ray diffraction, infrared spectroscopy, transmission electron microscopy (TEM) with EDX), microscopic observations (optical, SEM, TEM) and porosity measurements. The study of animal bones from the Neolithic site of Bercy, France (4000 BC) from the same archaeological layer within different local depositional, hydrological and redox environments illustrates the possible information that can be extracted from the diagenetic study on the processes affecting the state of bone preservation. The main characteristic of the bone buried in the waterlogged zone is a high level of preservation of the organic matter and a low level of porosity inhibiting major structural or chemical modifications. The bone sample from the zone with a fluctuating hydrological regime shows a low level of organic matter and high porosity. Knowledge of the diagenetic patterns enables an estimation of the reliability of information obtained from bone analyses.