Paul Budd

Differential diagenesis of strontium in archaeological human dental tissues

The investigation of prehistoric human migration from the measurement of Sr-isotope ratios within preserved tissue is critically dependent on the preservation of biogenic Sr. A number of recent studies have involved isotope ratio measurements on samples of archaeological tooth and bone, but doubt remains as to the extent of diagenesis in various skeletal tissues and the effectiveness of procedures designed to decontaminate them. The authors have compared Sr abundance and isotope ratios in enamel and dentine from archaeological teeth in order to assess the integrity of the biogenic Sr signal preserved within the respective tissues. It is concluded that enamel appears, in most cases, to be a reliable reservoir of biogenic Sr, but that dentine, and by implication bone, is not. The diagenesis of dentine is highly variable even between burials within a single site. For the majority of teeth, dentine diagenesis was not simply by addition of soil-derived Sr, but involved substantial, sometimes complete, turnover of the original biogenic material. It is suggested that, for most of the samples investigated, current decontamination techniques may not have been effective in isolating biogenic Sr from dentine. Similar considerations are likely to apply to archaeological and fossil bone, but the possibility arises to use dentine and enamel measurements to assess the effectiveness of decontamination procedures which may then be used for bone.

The distribution of lead within ancient and modern human teeth: Implications for long-term and historical exposure monitoring

The preservation of lead within human tissue makes it possible to monitor long-term exposure to the element and to model changing sources of lead pollution throughout the lifetime of an individual. Dental tissues have recently been shown to be particularly useful for this purpose. Enamel, for instance, forms at known stages of life and is chemically stable in vivo whereas dentine is remodelled in a predictable fashion. The relative stability of enamel is reflected in its excellent post-mortem preservation. This raises the possibility of using historical or archaeological material to reconstruct long-term trends and establish baseline data relating to exposure among pre-industrial or even prehistoric populations. The use of archaeological material is currently problematic, however, because of the site-specific nature of diagenesis and incomplete understanding of its chemistry, particularly in respect of lead uptake into dental tissue from the burial environment. A detailed study of lead distribution within both ancient and modern human teeth is presented. Conclusions are drawn on the pattern of lead distribution resulting from tissue formation and the manner of its alteration in the burial environment. In particular, attention is drawn to a consistent enrichment of lead within the outer 30 microns of the enamel of both ancient and modern teeth which appears to be unrelated to diagenesis. The implications for current approaches to long-term monitoring and for the reconstruction of historical and archaeological exposure patterns are discussed.

Reconstructing the Lifetime Movements of Ancient People: A Neolithic Case Study from Southern England:

A new procedure is described in which combined lead and strontium isotope analysis of archaeological human dental tissues can be used to comment on the lifetime movements of individuals. A case study is presented of four Neolithic burials – an adult female and three juveniles – from a shared burial pit excavated at Monkton-up-Wimbourne, Dorset. It is demonstrated that the adults place of origin was at least 80km to the north-west in the area of the Mendips. It is also shown that all three juveniles moved over significant distances during their lives.

Rethinking the quest for provenance

One of the larger — and more expensive — present programmes of study in archaeological science explores the provenance of prehistoric bronzes from the Mediterranean. What are the bases of research? What will the findings tell us about the real place of metal as it moved in the ancient world?

Zinc isotope fractionation in liquid brass (Cu-Zn) alloy: potential environmental and archaeological applications

Abstract A preliminary study of zinc isotope fractionation in brass melting suggests that the process can be modelled by simple Rayleigh fractionation. Brass melting experiments at 1100°C followed by quadrupole ICP-MS isotope ratio measurements of the resulting alloys suggest that the model is appropriate and that a useful approximation of the fractionation factor (α) is 1.0064. The data indicate that the change in isotope ratio of the residual liquid alloy would be measurable for zinc losses by evaporation of more than about 30 wt.%. It is unlikely that measurements at the precision of the current study (∼0.55‰amu−1) would be sufficient to distinguish between the two principal historical brass-making processes, although more precise measurement using a multi-collector ICP-MS probably would be. The experimental data also suggest that zinc vapour evolving during the evaporation of the first few per cent of the metal will be significantly fractionated (∼1.5‰amu−1) with respect to the liquid. This might provide a basis to distinguish between environmental zinc from high-temperature industrial processes and that derived from natural and manufactured product sources.

Tin sources for prehistoric bronze production in Ireland

Ireland is important in the early metallurgy of northwest Europe, for it has given us a large majority of the Early Bronze Age artefacts from the whole British Isles. Is there tinore to have been mined in early Ireland to produce this bronze or must it have come from elsewhere?