Étude technologique des gravures de Mané er Hroëk (Locmariaquer, Morbihan) : un nouveau cas de crosse transformée en hache dans l'art néolithique armoricain - article ; n°1 ; vol.101, pg 105-116

Bulletin de la Société préhistorique française - Année 2004 - Volume 101 - Numéro 1 - Pages 105-116
Un grand nombre de gravures armoricaines ont été réalisées par piquetage. Chaque impact du percuteur a provoqué un enlèvement de matière de quelques millimètres carrés en laissant un négatif d'éclat . Les négatifs d'éclats sont d'authentiques signatures de percussion qui renseignent sur les gestes employés par le graveur. La variation morphologique des négatifs d'éclats permet de restituer les différents gestes du graveur et de reconstituer ainsi la chaîne opératoire de taille. Enfin, l'étude des signatures de percussion permet d'identifier les cas de superpositions de gravures ou de démontrer des reprises, voire des transformations de signes jusqu 'à présent passées inaperçues. Par exemple, l'étude technologique des gravures de Mané er Hroëk (Locmariaquer, Morbihan) a montré l'exemple d'une crosse transformée en hache. Cette méthode constitue donc une nouvelle voie dans l'élaboration de la chronologie relative des représentations gravées du Néolithique armoricain.
A large number of Armorican engravings were made by pecking. Each hammerstone impact caused the removal of a few square millimetres of rock, leaving a distinctive groove called a flake negative . When erosion by weathering has not been too severe, these flake negatives can be reproduced almost perfectly with careful shading. The technique consists of dampening the engraved wall before flattening very fine tissue paper over it. The latter is pushed deeply into the engraving with a rag, in the same way as for a moulding. Shading can then begin, using carbon paper and varying the direction of the strokes. Separating the different flake negatives is carried out thanks to colour contrast: the carbon settles better at the edge of where the matter was removed than in the hollow part. The negative flakes then appear with a white body surrounded by black, and their outlines can be drawn, using tracing paper placed over the shading. On supports particularly exposed to weathering, a preliminary granulometric study is necessary, in order to avoid any confusion between the natural washing away of grains and flake negatives of anthropic origin. The flake negatives are an authentic percussion signature which informs us about the gestures employed by the engraver. Whatever the nature of the rock, the variation of the angle of the hammerstone on the engraved rock face results in a change of form of the flake negative. For example, if the angle of the hammerstone approaches 45° in relation to the plane of the surface being engraved, the negative takes on a lengthened form; on the other hand, if the hammerstone approaches an angle of 90°, the negatives become as wide as they are long. According to the form of negative, the following typology is used: when the length of the negative is identical to the width, it is described as punctiform; when the ratio of length to width is greater than 2, the negative is classified as longilineal; and between these two extremes, when the ratio lies between 1 and 2, the negative is qualified as slightly longilineal. The percussion signature allows us to reconstitute the sequence of operations. Thanks to the morphological variability of the flake negatives, from which we can deduce the engraver s gestures, the successive stages of making the design can be defined. Finally, this study of percussion signatures makes it possible for us to identify cases of superposition or to show previously unperceived repairs or transformations. For example, the technological study of the engravings at Mané er Hroëk (Locmariaquer, Morbihan) showed the case of a crook transformed into a hafted axe. This method thus represents a new approach in developing a relative chronology of Neolithic engravings in Brittany.
12 pages
Source : Persée ; Ministère de la jeunesse, de l’éducation nationale et de la recherche, Direction de l’enseignement supérieur, Sous-direction des bibliothèques et de la documentation.