Usages de la pierre dans la construction du port romain de Saint-Lupien à Rezé/Ratiatum (Loire-Atlantique) : extraire, transformer, bâtir

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Les recherches menées sur le site portuaire antique de Saint-Lupien à Rezé/Ratiatum (Loire-Atlantique) ont livré de nombreux renseignements quant aux modes de construction de caissons mêlant bois et pierre, utilisés comme quais en bordure d’un bras de la Loire et découverts dans un état de conservation exceptionnel. Au sein de ce programme monumental de construction, réalisé entre la fin du ier s. et le début du iie s. apr. J.-C., puis de diverses réfections ultérieures, la pierre, élément indispensable à l’ensemble, a fait l’objet d’une étude tracéologique et architecturale intégrant des questionnements liés à l’acquisition, à la transformation et à la mise en œuvre des produits lithiques.

Research carried out into the Roman port site of Saint-Lupien at Rezé/Ratiatum (Loire-Atlantique) has made it possible to examine the construction methods of port facilities established in the upper part of the Loire estuary as early as the end of the 1st c. AD. Discovered in a remarkable state of preservation, they take the form of monumental quays, built on the caisson principle and characterised by a mixed architecture combining timber and stone. This latter material, which was later favoured during the various transformations the quays underwent from the mid-2nd c. AD on, is at the heart of a traceological analysis and an architectural study with the aim of better understanding the construction and restructuring logics of the artificial platforms that have been uncovered, by integrating questions related to the acquisition, transformation and use of stone materials. It draws attention to the use of mica-schist for these developments, a local metamorphic rock that is not very suitable for quarrying. This material, abundant in the subsoil of Rezé, was the main material used for the construction of the quays of the port of Rezé/Ratiatum. The traceological analysis also highlighted the various processes used by the builders, who were able to take advantage of the physical characteristics of mica-schist, associated with timber. The shaping and perfect interweaving in the structural network of the quays reveals an ingenious and reasoned design.