Examining the Potential for Isotope Analyses of Carbon, Nitrogen, and Sulphur in Burned Bone from Experimental and Archaeological Contexts.

Abstract

The aim of this project was to determine whether isotope analyses of carbon, nitrogen and sulphur can be conducted on collagen extracted from burned bone. This project was conducted in two phases: a controlled heating experiment and an archaeological application. The controlled heating experiment used cow (Bos taurus) bone to test the temperature thresholds for the conservation of δ13C, δ15N, and δ34S values. These samples were also used to test the efficacy of Fourier Transform Infrared spectroscopy (FTIR) and colour analysis, for determining the burning intensities experienced by bone burned in unknown conditions.

The experiment showed that δ13C values were relatively unchanged up to 400°C (<2‰ variation), while δ15N values were relatively stable up to 200°C (0.5‰ variation). Values of δ34S were also relatively stable up to 200°C (1.4‰ variation). Colour change and FTIR data were well correlated with the change in isotope ratios. Models estimating burning intensities were created from the FTIR data.

For the archaeological application, samples were selected from two early Anglo-Saxon cemetery sites: Elsham and Cleatham. Samples were selected from both inhumed and cremated individuals. Among the inhumed individuals δ13C values suggested a C3 terrestrial diet and δ15N values suggested protein derived largely from terrestrial herbivores, as expected for the early Anglo-Saxon period. However, δ34S values suggested the consumption of freshwater resources and that this consumption was related to both the age and sex of the individual.

The experimental data shows that there is potential for isotope analyses of cremated remains, as during the cremation process heat exposures are not uniform across the body. The samples selected for the archaeological application, however, were not successful. Bone samples heated in controlled conditions produced viable collagen for isotope analysis; however, there are several differences between experiments conducted in a muffle furnace and open-air pyre cremation that need to be investigated further. Additionally, the influence of taphonomy on collagen survival in burned bone needs to be quantified. Finally, methods of sample selection need to be improved to find bone samples from archaeologically cremated remains that are most likely to retain viable collagen. While there is significant research that must be conducted before this research can be widely applied there are a multitude of cultures that practised cremation throughout history and around the world that could be investigated through the analyses proposed in this project.