Increasing the Temporal Resolution of Animal Movements: A Comparative Study of Laser Ablation and Microdrilling for Strontium Isotope Profiling of Herbivore Teeth

Abstract

Strontium isotope analysis is a widely used tool in archaeology to determine identify the providence and mobility of humans, animals and artefacts from the past. The strontium isotope ratio of a sample can be compared to other ratios from the same sample or the wider biosphere to identify an individual’s movements at various times during their lives. There are three main analytical techniques which are typically utilised to carry out these analyses: Thermal Ionisation Mass Spectrometry (TIMS), solution-Multi Collector Inductively Coupled Plasma Mass Spectrometry (solution-MC-ICP-MS) and Laser Ablation-Multi Collector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICP-MS). The first two require samples to be drilled and chemically purified before analysis while the latter does not. There are various advantages and disadvantages of each of these techniques. This thesis explores if it is possible to achieve high resolution LA-MC-ICP-MS analyses of archaeological herbivore tooth enamel from environments with low biosphere strontium isotope variation. It was determined that with current techniques it was not possible to achieve the compositional resolution and the required in these environments using high resolution LA-MC-ICP-MS analyses. A framework for determining how to select the most appropriate analytical method for a particular study is also presented.
This thesis also presents a case study utilising high resolution strontium isotope analysis using microsampling and TIMS on eight Bronze Age cattle from Cambridgeshire, while the range of bioavailable strontium in the region is narrow, it was possible to detect mobility in four of the cattle teeth, either the movement of the cow itself or the movement of the cow’s mother.