Bone diagenesis in the loess deposits of Central Europe: the Celtic site of Radovesice in Bohemia

The diagenetic modifications of archaeological bones from the Celtic site of Radovesice (Czech Republic) were described combining histological and instrumental analysis with infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The post-mortem changes in microstructure, mineral and organic fraction of human bones were related to seasonal fluctuations in water saturation and temperature, reflecting the Atlantic influence on the continental climate system of this transitional area of Eastern-Central Europe. The effects of a burial environment characterised by a well-oxygenated soil with good hydraulic conductivity, which evolved from the Quaternary loess deposits of the Bohemian massif, led to a common diagenetic pathway, which comprised micro-fissuring, mineral dissolution and degradation of collagen by microbial activity, followed by secondary calcite deposition under mildly alkaline conditions. Observed intra-site variations reflected changes in the early taphonomic history or in microenvironmental conditions, such as prolonged acidic conditions hindering apatite reprecipitation, as well as secondary calcite crystallisation. Diffuse effects of surface abrasion by sediments and absence of brown staining did not support the hypothesis of extensive use of wooden coffins. New indexes obtained from(31)P and(1)H NMR, respectively, were employed to describe diagenesis. They were found to correlate with FT-IR indexes, although reflecting distinct structural characteristics of bone which are not accessible to FT-IR.