L’abbatiale carolingienne de Saint-Philbert-de-Grandlieu. Le chevet et ses aménagements

Abstract

The Carolingian abbatial church of Saint-Philbert-de-Grandlieu. The chevet and its reworkings At the end of the nineteenth century, when the question arose as to whether to restore the abbey church of Saint-Philbert-de-Grandlieu, it was decided to build a new parish church and to convert the old building into a covered market. At the time, Léon Maître, archivist for the lower Loire valley, studied the monument, which he dated to the Carolingian period on the basis of a text written in the ninth century by the monk Ermentaire recounting the transfer in 836 of the relics of St Philibert from Herio (Noirmoutier) to Deas (Saint-Philbert-de-Grandlieu), because of the Viking threat. In the Miracula Ermentaire briefly describes the placement of the sarcophagus in the transept of the abbey and the partial reconstruction of the chevet. The excavations made by Père de la Croix indicated the structure of the monument, but some of his interpretations were immediately contested, notably by Léon Maître and Robert de Lasteyrie. In 1960, Pierre Lebouteux made a close analysis of the masonry, but could not arrive at a conclusion concerning the structure and date of the building without further excavations. On the basis of soundings and a new reading of the construction in 1997, the chevet of the abbey church was attributed without any doubt to the Carolingian period. The nave, rebuilt in the eleventh century, preserves only a few earlier elements. Two Carolingian phases came to light. The first, probably in the early ninth century, concerns the transept and foundation works discovered in the excavations, which revealed a polygonal apse, enveloped by a narrow corridor for circulation that led to a small rectangular eastern oratory. In the second phase, after 836 and before 858 (abandonment of Deas), the chevet was enlarged, with a deep semicircular apse, on a raised platform ; underneath was a confessional crypt with the sarcophagus of Saint Philibert and a small cruciform oratory, all of which are preserved in large part. On the periphery was built an important exterior crypt with three chapels at the east end. Radio-carbon dating, analysis of architectural terracottas, archaeomagnetic and thermoluminescent datings all confirm an attribution to the Carolingian period for the two phases.