New Constraints on the Metallurgical Activity at the Morimond Abbey (Haute-Marne) from the Archeomagnetic Analysis of two Excavated Brick Fireplaces

This paper presents the archeomagnetic dating results obtained from two brick fireplaces excavated inside the ancient cistercian abbey of Morimond (Haute-Marne). Complete thermal demagnetization of the collected samples allowed us to define a precise mean archeomagnetic direction acquired during the last cooling of each of the two structures. The dating of the last use of the two fireplaces was derived from the statistical comparison between a reference geomagnetic field directional variation curve constructed using the available French data set together with other data from nearby countries and the two directions obtained in this study. The two dating results lie, with a 95% confidence level between 1585 and 1615 AD and between 1525 and 1605 AD. Although these dates partially overlap, the two mean archeomagnetic directions are not compatible at the 95 % confidence level indicating a chronology in the abandonment of the two structures. These archeomagnetic results therefore confirm the existence of two metallurgical phases, which were independently observed during the excavations. They further refine the radiocarbon dating unable to discriminate the two phases. The two time intervals defined by archeomagnetism pre-date the abandonment of the building due to severe damages mentioned in written sources.