Analyse critique du protocole de caractérisation des hématites oolithiques mis en place dans le cadre du projet collectif de recherche sur L’origine des hématites oolithiques exploitées durant la Préhistoire récente entre l’Eifel (DE) et la Normandie (FR)

The provenance of ferruginous coloring materials has long remained a poorly exploited research subject. However, as a result of various studies carried out at the end of the 19th century and in the past decade, different analytic approaches have enabled the reconstruction of the supply of these ferruginous rocks, in terms of management of the mineral resources, their mobility and the technological and cultural orientations underlying their implementation and further use. Different analytical protocols have been established, taking into account fundamental conservation constraints, e.g., whether it was possible or not to collect samples, to transport and alter archaeological remains or whether analyses should be exclusively non-invasive. Petrographical, mineralogical and chemical analyses, combined or separate, allowed the accurate identification of the raw materials and of their particularities within various chrono-cultural and geological contexts, subsequently leading to their differentiation. Only the links between the proved geological resources and the archaeological ferruginous artifacts still needed to be determined. Furthermore it had to be determined whether the supply, or even the extraction of the ferruginous materials reflected particular choices and whether the archaeological assemblages are representative of the outcrops or the result of an intentional selection. Moreover, if it is possible to demonstrate that such choices were made, research should focus on the reasons behind these choices: have these been triggered by the geological context or have they rather been driven by cultural (traditions, value of coloring materials), social (group organization) and economic (site function, trade networks and access to sources of raw materials) considerations ?

The combined approach used in the framework of the collective research project ‘The origin of hematitic oolitic ironstones exploited during the late prehistory (Belgium, Normandy, Eifel)’ has allowed a high-resolution analysis, over a vast geographic area, of the exclusive sources of hematitic oolitic ironstones (OIS) available along the northern, northwestern and northeastern borders of the Paris Basin that were exploited by latest Mesolithic and Early Neolithic populations. This study has also allowed to locate the economic mineral areas and the regions of influence, as well as to identify OIS supply strategies and to suggest reasons for changes or continuity in the supply patterns of the raw materials. In particular, the research presented here supports the conclusion that Early Neolithic groups in Normandy were more selective than their latest Mesolithic predecessors, probably favouring the less weathered OIS layers. The OIS fragments recovered from the Early Neolithic sites in the Hesbaye-Dendre-Netherlands area, reflect a vast trade network between these 3 different regions, centered around outcrops near the Meuse river in the province of Liège. Inferred transport distances exceed 100 km, showing a possible control of the access to the raw material sources. Finally, our study has shown that there was no trade of hematitic oolitic ironstones between Normandy and the Belgium-Netherlands group.