Applying lead (Pb) isotopes to explore mobility in humans and animals

Abstract

Lead (Pb) isotopes provide a complementary method to other provenance tools for tracking the origin and movement of humans and animals. The method is founded in the geographic distribution of Pb isotope ratios. However, unlike the Sr isotope method that is closely linked to the lithology of underlying rocks, Pb more closely reflects the tectonic regimes. This makes it particularly pertinent to use in Britain as there is major tectonic boundary (the Iapetus Suture) that runs between Berwick-upon-Tweed and the Solway Firth providing a compositional boundary in Pb isotope domains that approximates to the geographic areas of Scotland versus England and Wales. Modern pollution makes it difficult to use modern floral or faunal samples to characterize biosphere variation, and so we use geological datasets to define isoscape variation and present the first Pb isotope map of Britain. We have validated the use of these data form biosphere studies using well provenanced samples. Reference fields of diagnostic compositions, are created in μ-T space and these have been used in a test case to assess the geographic origins of Neolithic animals in Great Britain.

Combining isotope ratios for provenancing Viking Age iron artefacts in the British Isles: a pilot study

“…In a recent study, Evans and colleagues 33 explored the distribution of Pb isotopes throughout the British Isles, taking advantage of the fact that unlike for strontium isotopes whose distribution is affected by underlying rocks, for lead there is a tectonic boundary between the Solway Firth and Berwick on Tweed – the Iapetus Suture – with clear isotope signatures appearing to the north and south of the suture which closely maps the current boundary between Scotland and England. Fig.…”

“…Firstly, in terms of a bivariant plot of 208 Pb/ 204 Pb ( y -axis) versus 206 Pb/ 204 Pb (Fig. 5b); or equivalently following Albarède et al 36 and Evans et al 33 plotting μ ( y -axis) versus the ‘Model Age T ’ parameter (Fig. 6b).…”

“…The more extensive work on lead isotopes across the British Isles in particular, show clear differences in published data for Scotland due to the Iapetus Suture and the known uranium depletion of the old Laurentian basement which underlies much of Scotland. 33 This is particularly important in trying to address the question of whether any iron objects found at Bebington on Wirral are unequivocally associated with the lost Battle of Brunanburh. The current “test” object – WA10 of unknown antiquity clearly is not, and may not be Viking Age at all.…”

“…All Pb isotopes of interest were simultaneously measured using the Faraday (see, e.g. Evans et al 33 ) cup configuration detailed in Table 2(c).…”

“…A better picture comes from trace Pb isotope analysis of the iron objectsthis is primarily because, in contrast with the Fe and Sr isotope data, the databanks of Pb isotopes for the British Isles are much better populated, based on rock, ores and faunal sources. 32,33 Fig. 4 gives bivariant diagrams of 207 Pb/ 204 Pb versus 206 Pb/ 204 Pb minor isotope ratios for our 8 objects.…”