Contribution to the chronological study of the Dubrovnik Cathedral using optically stimulated luminescence

Abstract

The 20th century brought unexpected archaeological discoveries under the Baroque Cathedral in Dubrovnik, the historic town of Ragusa (Ragusium) (the UNESCO World Heritage Site). In the 1980s, a church complex older than the historically recorded Romanesque Basilica was excavated. The study focuses on the use of Optically Stimulated Luminescence (OSL) dating to mortar samples collected from the internal layers of the key structures of this oldest church, plaster from the walls and sand layers under the masonry structures. The new data indicate a different chronological development of the edifice than previously suggested, while providing a more precise chronology of its early medieval refurbishments. Advanced building practices characteristic of the Late Roman eastern Mediterranean were detected, prompting a hypothesis that the early medieval masons adapted to default conditions near the town’s ancient port, while opening possibilities for future research into innovative building techniques aimed at achieving more flexible structures—potentially as a response to the region’s seismic vulnerability.