Taphonomy of prehistoric bark in a salt environment at the archaeological site in Hallstatt, Upper Austria - An analytical approach based on FTIR spectroscopy

Taphonomy of subfossil bark was assessed in Hallstatt, Upper Austria. Samples from the Bronze Age were compared with recent corresponding material from the same site. Preservation of the prehistoric samples was caused by storage in a salt and clay mixture. FTIR spectroscopy was used to determine differences in material chemistry. Principal Component Analysis was applied to display the segregation of the data set according to the different factors and to display the strength of the effects. Results revealed that deacetylation processes dominated aging processes. Focusing on two band regions at around 1730 and 1230 cm−1 a clear separation was achieved. Additionally some samples were selected for further analyses to investigate the influence of the inorganic matrix. Thermal analyses demonstrated an ash content of more than 15%mass. X-ray diffractometry revealed the presence of salt (dominant), gypsum, pyrite, quartz, and calcite minerals.