Multi-method dating of Grimaldi castle foundations in Antibes, France

The foundations of Grimaldi castle in Antibes belonged originally to a vast monumental edifice of an unknown origin. No historical records that would allow establishing precise chronological framework of this building exist. Therefore, four approaches were combined in order to date its construction: relative chronology from archaeology with “physical” dating methods applied on building materials, e.g. archaeomagnetic dating of bricks and dating of mortars by optically stimulated luminescence using both the single grain and the multigrain technique. Whereas archaeomagnetic dating followed a well-established, reliable measurement protocol, dating of archaeological mortar by optically stimulated luminescence using the single grain technique represents quite new, exploratory approach that allows direct dating of the moment of edification. Luminescence dating showed that mortars were well bleached. Variations of the dose rate due to the heterogeneous distribution of radioelements in the matrix were observed. In the given context, none of the four approaches used would succeed to date the construction of the remains with certainty if they were used separately. Nevertheless, thanks to the mutual comparison of dating results, a reliable chronology have been established. The obtained results are in agreement and suggest the Grimaldi castle foundations were built between the second half of the first century and the second century A.D. Our interdisciplinary approach thus proves ancientness of the standing masonry and attests cultural and historical significance of the monument.