A black tournai “marble” tombslab from Belgium imported to Trondheim (Norway) in the 12th century: Provenance determination based on geological, stylistic and historical evidence

Black Tournai “marble”, a fine-grained Lower Carboniferous (Tournaisian) limestone able to take a good polish has been widely used in the Flanders region (Belgium). Highly crafted baptismal fonts and tombslabs were also exported to England, France and elsewhere during the Middle Ages. Such objects are particularly valuable since their distribution aids the dating of historical events and the reconstruction of medieval trade. Similar black “marble” was extracted in the Meuse valley (Belgium) in the Middle Ages, and there are exploited sources in the UK, Ireland and elsewhere. Thus, it is not straightforward to determine the provenance of black “marble”. Based on geological, stylistic and historical evidence, this paper shows the likelihood that a black “marble” tombslab found in Nidaros Cathedral in Trondheim (Central Norway) was extracted and crafted in Tournai and shipped northwards around 1160, possibly for the grave of the first Norwegian archbishop, Jon Birgerson. The tombslab represents the first known crafted stone imported to Norway from the European continent/British Isles and is thus unique in a historical context. The properties of the Trondheim tombslab match those of black Tournai “marble”: It is a silicified, bioclastic packstone loaded with crinoids, featuring bryozoa and fragments of brachiopods and ostracods. The high silica content and absence of foraminifers distinguish the stone from the Viséan black “marble” quarried in the Meuse valley.