Silvana Maria GRILLO1 / Walter PROCHASKA2
(1Dipartimento di Geoingegneria e Tecnologie Ambientali, Facoltà di Ingegneria Cagliari University, Italy / 2Department of Applied Geological Sciences and Geophysics, University of Leoben, Austria)
The San Saturnino Basilica of Cagliari was built in the fifth century A. D. and is situated in the place where, according to tradition, St. Saturnino was beheaded in 304 AD. The early Christian Basilica is considered one of the most significant of the Mediterranean. It is surrounded by an archaeological park, where some excavations have revealed several Roman and Byzantine tombs.
During the centuries the Church underwent many restorations. In the late seventeenth century the building was partly demolished to recover materials for the restoration of the Cagliari Cathedral. After substantial air-raid damage during the Second World War, extensive renovations and partial rebuilding were necessary. The new Church was re-opened to the public not until 1996.
The main construction materials of the church are different local limestones – Pietra Forte and Pietra Cantone – from several quarries in the region. The decorative architectural elements preserved basically are red, grey and white marble columns. The preliminary identification of these coloured marbles so far is Cipollino Rosso from Iasos /Asia minor, and marbles from Lesbos and Carystum. Preliminary petrographic and geochemical studies showed that Carrara marble is the material of the white marble columns. Other fragments of white marbles as column bases, capitals and a sarcophagus are presently being analyzed for their provenance.
Especially the white Carrara marble columns are in an extremely bad condition due to weathering and the crystallization of different salts, resulting in sugary corrosion and sanding of the columns.
Both provenance studies of the marble inventory and also investigations on the mechanism of the salt deterioration will be presented.
Keywords: marble provenance analysis, weathing and restauration