Le bois de l’Enfer à Saint-Sauveur- le-Vicomte (Manche, France) : un nouveau dépôt de lingots plano-convexes et quelques éléments de réflexion sur la présence d'indicateurs spatiaux au-dessus des dépôts métalliques
Résumé
At the beginning of 2014, a set of massive metal objects was fortuitously discovered in a wood north of Saint-Sauveur-le-Vicomte, Manche, Normandy. The find is located along the eastern edge of the bois de l'Enfer, on a small terrace just below a sandstone cliff along a north-south axis. The cliff is less than thirty meters away from the river Ouve that flows through the village. Two of the authors (H.G. & C.M.) received the recovered artefacts for identification. The artefacts were exclusively bun shaped ingots and fragments of ingots, probably from a hoard.
A small excavation undertaken in February 2015 aimed to check for other objects and to document the context of the deposit. The dating of the probable hoard remains difficult, as no other objects were found during the initial discovery and the purpose of the excavation was also to recover any other objects in order to ensure a reliable dating. The hoard was located just under a small standing stone with three detachment surfaces and a blocking device consisting of small stones at its base. The sandstone block originally a marker or a landmark probably came from the nearby cliff. However, because of the very numerous bioturbations (mainly roots), no pit limits were identified during the excavation. For the same reason, it was not possible to interpret the position of the remaining metal artifacts under the standing stone, as some underlying roots had very likely disturbed the objects.
Eighteen metal elements were discovered in this hoard, eleven in the first instance, the remaining objects during the excavation. A small element was found on the surface near the sandstone block, one in the field between the cliff and the river (most likely lost by the inventor), and finally five underneath the standing stone. Unfortunately, no other objects were unearthed, the entire hoard consisting only of ingots and ingot fragments. The size and weight of these objects vary as the heaviest ingot weighs 3,356 kg, and the lightest ingot fragment only 66 g. All the artifacts found in the hoard have common characteristics: irregular and wrinkled surfaces as well as a general appearance of great porosity, with many deep holes and hollows being visible on the complete ingots. These first observations clearly indicate that the objects come from the final stage of the extractive metallurgy chaîne opératoire, in other words: the smelting of copper ore. It should also be noted that there is no possible refitting between objects.
In order to support the hypothesis that these objects are the result of a smelting process and not alloys from a later stage of the metallurgy chaîne opératoire, all the elements were analyzed using the ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectroscopy) method at the University of Rennes 1 to determine their elemental composition. It was found that in all cases the artifacts were made of copper of between 98.09% and 99.74% purity, the proportions in trace elements varying from one object to another. The fact that all the artifacts are copper ore smelting products makes it possible to overcome all the difficulties associated with the combining of copper / copper alloys from different origins or with recycled metal. It is this type of artifact that is closest to the original copper ores and thus to the mines, an important factor when considering the metal artifacts of the Atlantic Bronze Age in France. As there were no other manufactured objects providing a clear typology, the dating of the hoard has not been straightforward. However, similar hoards containing only copper ingots or ingot fragments have been found elsewhere, mainly in the south of the Armorican peninsula, making the bois de l'Enfer hoard, the northernmost manifestation of the phenomenon. A recent excavation in a field in Kergaradec, Gouesnac'h, Finistère, Brittany, has led to the discovery of 3 hoards, one of them containing only ingots and ingot fragments. The other two hoards, as well as another found in the 19th century again in the same field also contained the same ingots and fragments as the ones from Normandy. The manufactured objects in these hoards date to the final stage of the Late Bronze Age, providing a dating for the ingots only hoards.
The hoard of the bois de l'Enfer is a particularly interesting set in more than one way. Firstly, with more than 13 kg of copper, it represents the largest set of "foundry remains" uncovered in the Manche department. The fact that it is a hoard made up solely of bun-shaped ingots and ingots fragments is also to be noted, this type of set being particularly are. Further analyses of the ingots that focus mainly on lead isotopes, could match their signature with known ores from ancient mining districts.
The hoard was located in a small isolated wood on a terrace between a sandstone cliff and a marshy field. The field had not been ploughed which helped to preserve the sandstone block marker in situ. These markers have been recorded from time to time; however, there is no diachronic overview for France. In a study undertaken for this paper, it seems that stones or other markers placed near the hoards are far from anecdotal, and visually mark the position of some hoards within the landscape. This in turn provides new data for considering the meaning of these hoards and for reexamining their taboo status.
Au début de l'année 2014 un ensemble d'objets métalliques a été découvert de manière fortuite dans un bois au nord de Saint-Sauveur-le-Vicomte dans la Manche. Une fouille de contrôle a été réalisée en février 2015 afin de vérifier s'il restait d'autres éléments métalliques mais également pour documenter le contexte d'enfouissement. Ce sont au total 18 lingots et fragments de lingots plano-convexes qui ont été mis au jour dans ce dépôt qui était situé au pied d'un bloc de grès offrant trois faces d'arrachement et dressé verticalement avec un dispositif de calage à son pied faisant ainsi clairement office de marqueur spatial. Les premières observations indiquent qu'il s'agit là d'éléments issus de la fin de la chaîne opératoire de la métallurgie extractive, c'est-à-dire la réduction de minerai de cuivre. Afin de confirmer l'hypothèse qu'il s'agit bien de produits de première réduction et non pas d'alliages, la totalité des éléments a été analysée via la méthode ICP-AES. Il s'agit dans tous les cas de cuivres assez purs, entre 98,09% et 99,74% avec des proportions variables des éléments en trace.
Malgré l'absence d'objets mis en forme, le dépôt du bois de l'Enfer a été attribué au Bronze final atlantique 3 (BFIIIb), par comparaison avec des ensembles équivalents. La localisation du dépôt dans un petit bois isolé a contribué à préserver in situ le bloc de grès au pied duquel le dépôt était enterré, et qui devait le marquer dans le paysage. De tels aménagements sont connus dans la littérature pour les dépôts de l'âge du Bronze, mais sans synthèse diachronique au niveau de la France. L'exercice a été tenté ici, et on constate que la présence de pierres ou d'autres marqueurs spatiaux au-dessus des dépôts de l'âge du Bronze n'est finalement pas anecdotique, marquant ainsi une volonté de signaler au moins certains dépôts visuellement dans le paysage. Ceci apporte en retour de nouveaux éléments de réflexion quant à la signification de ces dépôts et au concept de tabou qui leur était peut-être attaché.