Content:
In strontium isotope ratio studies, strontium concentrations are routinely determined prior to the determination of the strontium stable isotope ratios themselves. During this initial step, concentrations of additional trace elements can easily be determined at little to no additional cost. Concentrations of barium in particular may be helpful to provide additional dietary information, provided the sampled enamel is sufficiently well-preserved.
This presentation provides a brief overview on the history and use of Ba, Sr and Ca concentrations and ratios as palaeodietary indicators, starting with initially inflated expectations, and followed by disillusionment in the face of diagenetic problems. Nevertheless, concentration ratios of Sr to Ba in tooth enamel may provide additional information on past diets: Using both present-day reference material and archaeological tooth enamel samples from the Orkney islands, this presentation gives a case-study on the use of Ba/Sr ratios to identify seaweed-consumption by sheep, with a comparison to the use of δ¹³C as a palaeodietary indicator. It was found that tooth enamel from present-day seaweed-eating sheep had significantly lower lg(Ba/Sr) values (−2.4 to −1.6; enamel δ¹³C of −6.7‰ to −3.3‰; n = 10) compared to terrestrial-feeding sheep (0.6 to −0.5; enamel δ¹³C of −15.5‰ to −14.7‰; n = 5). Comparisons between δ¹³C values and lg(Ba/Sr) values from several Neolithic archaeological sites showed similar trends, indicating that lg(Ba/Sr) may be useful as a dietary indicator, supplementary to δ¹³C.
Literature data indicates that Ba/Sr ratios may also be useful to study dietary uptake in other contexts, including trophic level, consumption of fish and seaweed-fertilised crops and differentiating between grazing and browsing. In conclusion, the inclusion of Ba and Ca concentration measurements in preparatory analyses of strontium concentrations for later strontium isotope ratio measurements is strongly advocated.
Keywords:
lg(Ba/Sr), palaeodietary analysis, trace element ratios, seaweed, sheep, barium
Affiliations:
1 Archaeology Institute, University of the Highlands and Islands, Orkney College UHI, Kirkwall, Orkney, KW15 1LX, Scotland, UK
2 Environmental Research Institute, University of the Highlands and Islands, Castle St, Thurso, Scotland, KW17 7JD, UK
3 Human Evolution and Archaeological Sciences (HEAS), University of Vienna, Austria
4 Institute for Chemistry, TESLA - Analytical Chemistry, University of Graz, Universitätsplatz 1/I, 8010, Graz, Austria
5 NEIF Radiocarbon Laboratory, Scottish Universities Environmental Research Centre, Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride, G75 0QF, UK
6 Université Paris-Saclay, CEA, List, F-91120 Palaiseau, France
7 Vienna Institute for Archaeological Science (VIAS), University of Vienna, Franz Klein-Gasse 1/III, 1190 Wien, Austria