Approche pluridisciplinaire d’un ensemble d’objets métalliques de l’Âge du bronze découvert à Soulac-sur-Mer (Gironde, France)

Abstract

This study concerns metallic objects discovered in 2002 on Amélie beach, Soulac-sur-Mer (Gironde ; Aquitaine). Many Bronze Age hoards have previously been discovered in this area. This find contains thirteen copper base alloy artefacts : eight massive bracelets (three of which present line decoration), a flanged axe, a broken palstave axe, an ingot, a sword fragment and a ring. The flanged axe is typical of production in the Médoc region. The other objects (bracelets, sword and ring) suggest the Duffaits culture. The present contribution concerns a technological study of all the objects : surface observations, metallographic examinations and elementary composition analysis. Fourteen metallographic sections were made according to a specific protocol which, after preparation of the samples, allows the polished sections to be examined before they are etched with a ferric chloride solution. Composition analyses were obtained with an EDXS device associated with a scanning electron microscope. The results enable us to understand the chaînes opératoires used for making these types of flanged axe and massive bracelets. The sequence of the flanged axe shaping processes can be described, and certain gestures and tools clarified. An assembled mould (made with stone or terracotta) was used. After the stripping, a grinding operation, using abrasive materials, was applied to the whole object. Then an annealing and finally a fettling operation – which leaves the metal in a partially hardened state – were applied to the object. No other thermal or mechanical treatment occurred later. This state can be qualified as rough. The technological reading of the set of bracelets confirms their morphological homogeneity by that of the manufacturing processes. The concordance of similar parameters in shape, decoration and shaping techniques allows us to suppose that all the objects were produced in the same workshop. These bracelets were manufactured by a plastic deformation, with the coiling of a bar whose thickness and section shape were certainly conceived from the very moulding. In the very last operation, the decoration was obtained by plastic deformation, on metal softened by annealing. The use of a scriber is very possible. The presence of finished objects and of a rough casting certifies that a local production existed in the area of Soulac-sur-Mer. This technological study allows us to discuss the question of the circulation of metallic objects. The case of the rough axe represents a stage in the chaîne opératoire. This would have been divided into two stages : moulding/ fusion and post-casting. A particular organization would have separated these two stages which would not then have been produced in continuity. We thus submit the hypothesis according to which several types of workshops could have existed, functioning on a «cascade » effect system. An important hierarchical organization of society would in that case be highlighted, with a strong power or authority importing the metallic raw material, centralizing it and, by doing so, being able to control a particular type of workshop making rough-standard axes : the Médoc type axes express rigorous morphometric rules.