11-2018, tome 115, 2, p. 327-360 - Anne-Françoise Cherel et Bernard Gratuze, avec la collaboration de Patrick Simon - Les perles en faïence et en verre de l'âge du Bronze découvertes en Bretagne : nouvelles données, nouvelles approches. Étu

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11-2018, tome 115, 2, p. 327-360 - Anne-Françoise Cherel et Bernard Gratuze, avec la collaboration de Patrick Simon - Les perles en faïence et en verre de l'âge du Bronze découvertes en Bretagne : nouvelles données, nouvelles approches. Étu

Résumé : L???essor de l???archéologie préventive, corrélé aux progrès notables des méthodes d???analyses chimiques, a permis de reconsidérer notre approche analytique de la parure en faïence et en verre. D???importants programmes de recherche portant sur la circulation de ces éléments de parure, associant les études typo-chronologiques aux analyses chimiques, ont été développés. L???un d???eux est en cours de réalisation, pour les périodes de l???âge du Bronze et de l???âge du Fer en France (Billaud et Gratuze, 2002). L???étude des perles en faïence et en verre découvertes en Bretagne à l???âge du Bronze s???inscrit dans cette démarche, et vient compléter la synthèse réalisée sur les perles du premier âge du Fer et du début du second âge du Fer (Cherel et Gratuze, 2018). Depuis l???étude de J. Briard (1984) sur les perles en faïence, aucune synthèse consacrée aux perles en verre bretonnes de l???âge du Bronze n???avait été menée. Au total, 9 perles en faïence (dont 8 analysées) et 15 perles en verre (dont 13 analysées) ont été étudiées, soit un total de 24 perles de l???âge du Bronze. Les perles en faïence du Bronze ancien proviennent majoritairement de sépultures. Leur étude typo-chronologique corrélée à celle de leur composition indique l???origine nord-italique de plusieurs d???entre elles. Au Bronze final, cette tendance se confirme puisque 9 perles en verre proviennent d???ateliers nord-italiques auxquelles il faut ajouter, au Bonze moyen/final, 5 perles en verre égyptien et 1 perle en verre mésopotamien. Les découvertes sont fréquentes en prospections, on les trouve ponctuellement sur des sites gaulois ou antiques attestant de leur valeur. Peu d???entre elles ont été mises en jour en contexte d???habitat. Sur ces deniers (Brandivy, Cesson-Sévigné), de la céramique du Bronze final de tradition continentale était présente, aux côtés de perles originaires d???ateliers nord-italiques. Au Bronze final, la Bretagne se situe au c?ur de relations profondes entre le monde méditerranéen (complexe nord-italien) et, via les circuits d???échanges, le domaine continental (complexe nord-alpin), puis le complexe atlantique (Irlande et Grande-Bretagne ?). La circulation des objets de parure en verre illustre bien l???itinéraire emprunté par la fameuse « route de l???étain ».

Mots-clés : perles en faïence et en verre, âge du Bronze, Bretagne, inventaire, typo-chronologie, analyses chimiques, composition, ateliers de verriers nord-italiques, verre brut mésopotamien et égyptien, échanges commerciaux.



Abstract: During the last decades, with the rise of preventive archaeology, the discovery of protohistoric glass beads has increased in different regions of France. In the same time, advances in analytical methods gave the possibility to characterize these ornaments, which are fragile and often badly altered, while respecting their integrity. This combination of factors has led to undertake major research programmes on the circulation of these objects by combining typo-chronological approaches with chemical analyses.

It is within this context of research that an exhaustive inventory of protohistoric faïence and glass beads (Bronze Age and Iron Age) discovered in France has been carried out (Billaud and Gratuze, 2002; Plouin et al., 2012; Gratuze and Billaud, 2014). Thanks to a fruitful collaboration, with both museums and preventive archaeology operators a corpus of more than two thousand objects from several hundred archaeological sites (habitats and burials) has been collected.

For Brittany, more than a hundred objects, beads and bracelets were analysed among approximatively 200 protohistorical ornaments recorded.

Up to now, for this area, the only available synthetic study on the subject was that of J. Briard, published in 1984, which dealt exclusively with earthenware beads from the Bronze Age.

The aim of this paper is therefore to draw up an updated assessment of the data available for the Bronze Age in Brittany. It completes the publication of the beads found in the Hallstattian context (Cherel and Gratuze, 2018) and the research carried out for the La Tène period (Cherel and Gratuze, in progress).

The approach developed in this study consists, when possible, to ascertain a critical comparison of the contexts of origin of these objects with their typological and chemical parameters. While most of the studied objects come from well-dated sites, from the Early Bronze Age to the Late Iron Age, some of them come from uncertain contexts or consist of surface findings. The chemical and typological characteristics of the latter have, however, sometimes allowed us to associate them with the Bronze Age or the Iron Age productions.

The analysed corpus consists of eight faïence beads and thirteen glass beads.

Since the works of J. Briard initiated in 1984, only one additional discovery has been added to the corpus of Brittany faïence beads. As for the 15 glass beads, it has never been published before. Part of them originates from recent operations carried out in preventive archaeology, notably by Inrap (Quimper, Kergolvez in Finistère; Cesson-Sévigné, La Salmondière in Ille-et-Vilaine) and in programmed archaeological surveys (Le Quiou). These finds contribute to considerably increasing our data. The study of their contexts of provenance, correlated with their typology and chemical groups, therefore makes it possible to undertake new approaches.

Recent studies have shown that the chemical analyses of this type of material make it possible to go beyond a simple inventory and that they offer new perspectives. These new tools are particularly useful for determining the origin of the glass used to make these ornaments, locating the production workshops and identifying networks of exchanges through a cartographic approach.

Sixteen other objects can also be added to that corpus: one bead from Brandivy (Morbihan), two from Saint-Nicolas-du-Pélem (Côtes-d???Armor), one from the Island of Groix (Morbihan), and thirteen from the Ushantin site of Mez Notariou in Finistère. Two of them were lost but can be assigned to Late Bronze Age productions according to their published drawing, the others will be either published separately (Le Bihan et al., forthcoming) or their analysis has not been possible. It should also be noted that many beads were discovered during surface surveys at the protohistoric sites of Saint-Nicolas-du-Pélem (Colledic plateaus). Most of these objects have typological and/or chemical characteristics which do not allow relating them to the Bronze Age productions. Only two of them, one in earthenware (analysed) and one in glass (not analysed), show strong similarities with Bronze Age objects.

Some other beads were deliberately excluded from the corpus due to a lack of reliable information about their discovery and dating. However, the results obtained on four glass beads from Saint-Nicolas-du-Pélem (Côtes-d???Armor) and one from Pléchâtel (Ille-et-Vilaine) which belong probably to the modern period, will be discussed.

The first part of that paper offers a detailed description of the different sites and objects. Each beads of our corpus is confronted with the latest information available from recent publications.

The second part is devoted to the typo-chronological study. The simplified typology presented in this paper (fig. 3 and 4) makes the descriptions of these objects easier to understand.

The third part develops the chemical results obtained on these objects and their interpretation.

Two main compositional groups were found for the earthenware beads. The glass phase of the first one (five beads) has not been preserved or is highly corroded and it is therefore not possible to provide any information on the recipes used for the manufacture of these objects.

For the second group (three beads) a thick and well-preserved blue glass phase is present on a large part of the surface of these objects. This vitreous phase is made of a soda-potash glass coloured by copper oxides. Its characteristics are similar to that of the glass made by the northern Italian workshops of the Frattesina area.

If we except the presence of six modern glass beads, the thirteen remaining glass ornaments form two main compositional groups. The objects of the first one (six beads) are made from a plant ash soda glass which chemical characteristics correspond to those of the near-eastern glass productions. It is further possible to relate the glass used for five of them to Egyptian raw glass production while the glass of the remaining bead can be associated with Mesopotamian raw glass.

The glass used to make the seven other beads is a soda-potash glass (LMHK type, low magnesia high potash) similar to the one produced by the northern Italian glass workshops of the Late Bronze Age (Frattesina).

One of these beads (Toul-Goulic no 2 from Tremargat in Côtes-d???Armor) presents a unique decoration made up of an opaque white equatorial line with probably three eyes consisting of a central spot of opaque reddish glass circled which a thin ring of pale opaque turquoise glass. To date, only one other such bead has been described in Rathgall, Ireland (Raftery and Henderson, 1987).

Our results show that Brittany was, as soon as Early Bronze Age (with faïence beads), at the crossroads of important exchanges. During the Middle or the Late Bronze ages, the chemical analysis of glass beads highlights the presence of both Egyptian and Mesopotamian glass.

The example of faïence and glass beads originating from the North Italian workshops is also evocative. In the Late Bronze Age, Brittany lies at the heart of complex exchange network between the Mediterranean world (Northern Italy) and the North Atlantic (Ireland and Great Britain?).

The distribution of these glass ornaments may illustrate the itineraries taken by the famous ???tin roads???. Some of the inland sites where the beads were discovered could constitute an area of ???markets??? between maritime and continental domains. The important protohistoric route of Central Brittany may have serves active mining and metallurgical centres where Italian beads are present, up to Ushant.

In the future, it would be desirable to apply this work to the regions bordering Brittany in order to better characterise the trade routes used (e. g. the role of the Loire axis?).

Keywords: faïence and glass beads, Bronze Age, Brittany, inventory, typo-chronological study, chemical analyses, compositional groups, north Italian glass workshops, Egyptian and Mesopotamian raw glass, trade.