THE DATING OF DOLOMITIC MORTARS WITH UNCERTAIN CHRONOLOGY FROM MÜSTAIR MONASTERY: SAMPLE CHARACTERIZATION AND COMBINED INTERPRETATION OF RESULTS

Abstract

To obtain scientific data regarding the chronology of archaeological structures, lime mortar radiocarbon dating has often demonstrated to be a decisive method. However, knowing the specific chemical-mineralogical characteristics of mortars can help when preparing samples or interpreting results. Among other issues, the dating of magnesian mortars can be particularly difficult because of the combined slaking, setting and hardening reactions of the calcium and magnesium phases, typical of these mortars. The formation of numerous mineralogical phases depending on reaction conditions adds further complexity to the dating method, which deserves to be studied with further detail. During the project “Mortar technology and construction history at Müstair Monastery” the first experiments in this regard had yielded encouraging results. An additional 4 samples from buildings with controversial chronology, thought to belong approximately to the 9th, 12th, and 15th centuries, were selected, prepared and radiocarbon dated. The data obtained were discussed by integrating preliminary petrographic characterization analyses of the mortars with archaeological information and excavation records. The results opened up new questions about the chronology of the Monastery, clarified the dating of some buildings and provided a better understanding of the potential and limitations of dating dolomitic mortars coming from archaeological context.