Mobility and Stasis in the Bronze Age
Nov 27, 2012 02:30 PM
End: Nov 27, 2012 05:00 PM
Location: Room 609 (Staff Common Room), Institute of Archaeology
A half-day thematic workshop looking at mobility and stasis in the Bronze Age will be held at the Institute on 27 November and all are welcome.
- Zofia Anna Stos-Gale (Sussex): Lead isotope and chemical compositions of the Swedish Bronze Age copper-based artefacts as indicators of the origin of metal
Combined lead isotope and chemical analyses of ancient copper, lead and silver artefacts provide a powerful tool for identification of the geographical origin of the ores used for the metal extraction. The element lead in nature is formed of four isotopes named according to their atomic mass: 204Pb, 206Pb, 207Pb and 208Pb. The 204Pb isotope was originally present in the Earth crust; the other three isotopes are formed from the chains of radioactive decay of uranium and thorium. Lead, uranium and thorium have different solubility in rock-forming fluids, and for that reason lead present in them at the time of ore formation is separated from the other two elements. Therefore, at the time of the formation of an ore deposit the radioactive production of the three radiogenic isotopes in this mineral stops and lead isotope composition of the ore mineral remains unchanged, because no more atoms of 206Pb, 207Pb and 208Pb are created. Because of the different initial abundance ratios of all four lead isotopes, the concentrations of uranium and thorium in the ore forming fluids and different times of the ore formation, the final lead isotope ratios in ore deposits are different. The measurements of lead isotope ratios have been used in geosciences in the last 40 years for the age determination of ores and rocks and for mineral prospecting. In the last 30 years this method has been applied in archaeometallurgy for ‘fingerprinting’ of ore deposits used in ancient times and comparing them with the lead isotope compositions of ancient artefacts (see for example: Gale and Stos-Gale 2000).
The interpretation of lead isotope data needs to be combined with the knowledge of the chemical compositions of the artefacts and geochemistry of the ores, because even if by itself the chemistry of smelted metals is not an indication of origin, it is a very important component of comparisons between the sources of ores and man-made metals (see for example: Hauptmann et al. 1999, 9-10 and 2011, 68-70).
The successful use of the lead isotope ‘fingerprinting’ for finding provenance of ancient metals depends crucially on the availability of the lead isotope and chemical data for the widest range possible of ore deposits and groups of ancient metals of comparable date to the artefacts from unknown metal source. Currently a primary database of lead isotope data from the Isotrace Laboratory is being created on the website of the University of Oxford.
The OXALID database, combined with the extensive range of the data published by other researchers, was used for interpretation of the lead isotope compositions obtained in the Swedish Museum of Natural History in Stockholm for 71 copper-based artefacts from Bronze Age sites (1600-700 BC) in southern Sweden. The elemental analyses of these artefacts were performed in the Geoarchaeological Laboratory of the Swedish National Heritage Board in Uppsala.
The initial aim of this research was to test if the Swedish bronzes were made from copper ores found in Sweden. Due to a quite unique in the European context geochronology of Swedish copper mineralisations, and therefore quite unusual lead isotope ‘fingerprints’, the comparisons show clearly that the Swedish source for these metals is not possible (Ling et al. 2012). On the other hand, the comparisons with ores and metals from various European ore deposits and metal artefacts from Bronze Age sites show that the copper-based artefacts found in Sweden are consistent with the origin from metal deposits situated in the British Isles, the Iberian Peninsula and the Austrian Alps. Even the chronologically earliest artefacts are not uniform in the source of the copper, indicating sources of copper as diverse as Ireland, Tyrol and Cyprus. In the later periods high tin bronzes show also lead isotope ‘fingerprints’ of Sardinian and Spanish ore deposits. Lead isotope analyses of contemporary artefacts from the British Isles, Switzerland and the Aegean show that metal from the same sources can be found in distant regions of Europe.
This presentation will discuss in detail the lead isotope and elemental evidence for the origin of these 71 copper based Bronze Age objects from the Swedish sites and relevant groups of bronzes from other countries.
- Johan Ling (Gothenburg): Metals, Boundaries and flows
Ever since the work of Montelius and Childe, motion, interaction and mobility have been seen as central features for the" international system" that emerged in Europe during the Bronze Age. Thus on basis of diffusion of certain forms and objects most scholars have argued that copper was impored to Scandinavia from Central Europe during the Bronze Age and the ideas of Scandinavia's relations, alliances, networks and boundaries have been founded on these assumptions. However, recent lead isotopes on Nordic Bronze Age artefacts strongly challenge these notions and show instead a more complex picture of the interaction and of metal during the Bronze Age. We will further argue for the notion of maritime position and ambers as Nordic comparative advantage in the "international " metal trade networks. . Thus Bronze Age materials, boundaries, connectivities suggests 'worlds in creolisation' and the hybridity of practice.
- Michael Rowlands (UCL): Discussant: Stranger King or Sahlins in the Bronze Age