The contribution of earth sciences to the preservation of underwater archaeological stone materials: An analytical approach

This work focuses on the study of alteration and degradation forms affecting underwater archaeological marble fragments mainly due to biological activity. The studied artefacts were recovered from the submerged archaeological park of Baia (Naples, Italy). It includes ruins of the ancient city of Baiae, which, since the 4th century AD, started to be submerged due to the bradyseism phenomenon. Diagnostic investigations were carried on 50 marbles specimens, collected from covering slabs of different pavements, from a specific area of the site called “Villa con ingresso a protiro”. Several techniques, including stereomicroscopy, polarizing optical microscopy, scanning electron microscopy and mineralogical analysis, were used to study the superficial weathering, as well as the bioerosion phenomena due to the action of marine organisms and their interaction with the substrate in relation to textural features. Results revealed that the main degradation processes can be attributable to endolithic activity, capable of excavating cavities and tunnels causing irreversible damage to the archaeological materials. In addition, samples revealed a different degree of bioerosion related to their specific intrinsic characteristics.