Ground-penetrating radar imaging of twelfth century Romanesque foundations beneath the thirteenth century Gothic abbey church of Valmagne, France

摘要

Ground-penetrating radar surveys with closely spaced profiles using 500- and 800-MHz antennae were performed on the fine gravel floor of the Gothic abbey church of Valmagne, near Montpellier, in south-central France. The accessible floor area of the choir, transept and nave was surveyed to locate and preliminarily interpret the remains of the twelfth century Romanesque building beneath the existing building. Processed two-dimensional ground-penetrating radar profiles and constructed time-slice images show distinct reflection events associated with the twelfth century foundations. The GPR technique is calibrated against a known buried limestone pier belonging to the earlier Romanesque construction. It proved challenging to differentiate the remains of the twelfth century building from the existing building and the host geology because the dielectric contrasts between them is low. Preliminary interpretation of the results suggest that the Romanesque pier abuts and continues under a thirteenth century pier at the intersection of the ambulatory and transept of the existing church. In addition, the twelfth century building appears to have had a rectangular sanctuary flanked by chapels of unequal width opening off a transept comparable in width and length with the existing transept and a nave comparable in length with the existing nave. The results of this study are significant to medieval architectural history since they reveal new subsurface constraints on the nature of Cistercian construction in Languedoc.