Methodology for the sourcing of prehistoric coloring materials – COLOR-SOURCES

Beyond their role in artistic creation and symbolic expression of prehistoric societies, colouring materials were involved in different kind of activities related to technical and subsistence practices. The analytical developments of recent years, founded on the combination of naturalist (geology/ petrography) and archaeometric (mineralogical and elemental analysis) approaches, have provided a better understanding of the nature of these materials and allowed to investigate their geological origin. However, the application of these studies remains rare, even if colouring materials constitute an important potential of information for the understanding of technical and cultural behaviours, and the circulation of people and materials. There are several reasons for this scarcity of applications: 1/ the lack of knowledge about the evolutionary chains, i.e. the modifications of their characteristics due to bio-geochemical, anthropic and taphonomic transformations that occur from the deposit to their discovery: these modifications of their composition constitute biases that can limit the identification of the geological and geographical origin of the colouring materials; 2/ the diversity of the analytical protocols and the heterogeneity of data produced between laboratories and research teams: these biases limit the comparison of data between studies and limit the generalisation of these approaches; 3/ the difficulty of analysing and comparing the composition of blocks of colouring matter with that of residues on the surface of archaeological remains: while the protocols for analysing cohesive blocks are efficient and hardly invasive, the analysis of residues remains difficult and the analytical techniques used on the blocks do not provide the necessary spatial resolution for analysing these thin layers; 4/ the lack of robust geological references: the establishment of geological references at a regional or supra-regional scale requires considerable investment. The geological reference collections, established independently by researchers or teams as a result of projects centred on archaeological sites, are not easily accessible and reusable, notably because of standardisation issues. The objective of the Color-Sources project is to overcome these constraints in order to provide a new dynamic to the study of the origins of prehistoric colouring materials at a national and international scale, by developing and sharing knowledges and methodologies necessary to build geological reference collections and to compare them with archaeological collections. This objective will be achieved by developing an "open science" dynamic and the production of "FAIR" (Easy to Find, Accessible, Interoperable, Reusable) data.
To this aim, Color-Sources will be supported by an interdisciplinary consortium in order a) to share the experience acquired in our various archaeological fields in order to better understand the evolutionary chains, to develop a common methodology for studying colouring materials and to implement it in a common field: the Dordogne and its periphery; b) to develop interoperable data acquisition protocols, to improve the statistical processing protocols for the data produced (particularly elementary data), and to develop an elementary analysis methodology by LA-ICP-MS/MS that could be applied to both blocks and residues of colouring materials in order to limit the biases induced by the use of several different techniques, c) to design an information system to save, reuse and disseminate the data acquired by the French community on the sources of raw colouring materials used in the Palaeolithic period.