Provenance studies using lead isotopy: contribution of the consideration of geological contexts in archaeological databases

Abstract

The identification of mineral supply sources and trade routes are at the heart of the archaeological issues. The tracing of sources of metal production via lead isotopy has been used since the 1980s to identify the deposits from which the metal constituting the archaeological objects came. Such studies are based on mineral signature repositories and archaeologists have thus built up databases containing thousands of ore deposit analyses. The databases, however, only very rarely include geological information and are limited to geographic information. But considering only geographical data leads to many limitations of studies, including the overlapping of signatures between remote regions. This problem could nevertheless be circumvented by taking into account precise ore deposit data that enables to think in terms of restricted mineralized subsets. We illustrate this through the example of data collected in the Alps by Marcoux (1986) and Nimis et al. (2012). Taking into account geological data (and more specifically, gitological data) could thus considerably improve the accuracy of provenance interpretations and enable multivariate statistical processing to be carried out (these statistical treatments are inconclusive if they are carried out on purely geographical data). However, remains the problem of the thousands of ore analyses carried out without having defined their mineralization context. Although still imperfect (some contexts are not individualized), the use of a statistical treatment could nevertheless be used to identify the gitological contexts.