Integrated methodologies for assessing the provenance of building materials from the Roman pier of San Cataldo (Adriatic coast, southern Italy)

A multidisciplinary and multiparametric approach is proposed with the purpose of establishing the original quarries of the building materials used in a monumental pier of the Roman age located in San Cataldo (Lecce, Apulia Region), the main harbour of the Roman town of Lupiae. The pier, dug up after a three years long archaeological campaign, shows a massive structure and consists of two outer curtains made up by large squared limestone blocks and a core in opus caementicium. In the manufacture of the outer curtains, three different calcarenite varieties have been recognized, all belonging to the Pietra Leccese Fm., a Miocene calcarenite, greenish-straw or yellow-whitish in colour, which crops out in a broad geographical area of the Salento Peninsula. About 50% of the rock blocks, used mainly in the upper part of the structure, generally presents a greenish colour and is very rich in glauconite and phosphatic nodules. These are limestone blocks belonging to the “Piromafo” variety, a well-known rock type of Pietra Leccese which lies in the higher stratgraphic level of the formation. Micropalaeontological content allows to classify the material as a biomicrite rich in planktonic Foraminifera of the Miocene (Tortonian-Messinian). In addition, the biostratigraphical characteristics are very similar to some outcrops at Acaya-Strudà, a locality some 10 km south of the ancient harbour. Comparative analyses, biostratigraphical and physical (density and micropore structure) in types, have been performed, supporting a clear identification of the geological origin of the limestone blocks. In respect of the hydraulic concrete used in the opus caementicium, different lithic materials have been used and mixed with a strong mortar. Macroscopic field observations clearly define that the limestone clasts, very heterogeneous in size, derive from the Uggiano la Chiesa Fm. (Pliocene) that widely crops out locally at San Cataldo; the granular fractions of the mortar probably derive from beaches and/or sandy dunes, available in the surrounding area, as well.