Laser ablation U-series analysis of fossil bones and teeth

Over the past decade, we have applied laser ablation ICP mass spectrometry U-series analysis to a large number of bones and teeth. The method is fast and provides high-resolution data of U-series isotopes, which give insights into the complexity of uranium migration into, within and out of bones. In this paper, we present our laser ablation approach in detail, from the experimental set up, to data reduction and uranium diffusion modelling. Laser ablation analysis can now be applied with minimum damage. Complete diffusion data sets can be obtained by laser drilling which leaves a hole of around 200 μm in diameter and 1–2 mm depth. If the natural U-diffusion follows a simple single-stage process, valuable age information can be obtained. In other cases, highly complex U-migrations have been observed, which make any age assessment impossible. Two examples from Wadjak and Callao illustrate the potential of nearly non-destructive laser ablation U-series analysis of human skeletal tissues. The results demonstrate the physical presence of modern humans in south-east Asia at a time when our species just started to migrate into Europe.