Assessment of geomaterials through geological inventory in ancient cities: the example of Tamuda arqueological site (NW Morocco)

Abstract

Effective conservation of archaeological sites demands systematic knowledge of construction geomaterials and their deterioration patterns. This study develops and validates a transferable methodological protocol for heritage geomaterial inventory and decay assessment, using the Tamuda site (Morocco) as an applied case study. The method integrates: (i) field mapping and quantitative stone-type quantification; (ii) standardized weathering diagnosis following the ICOMOS-ISCS glossary; (iii) correlation of decay mechanisms with petrographic properties; and (iv) provenance linkage to local geological formations. Applied to Tamuda, the protocol reveals a dominant assemblage of sandy limestone (37%), sandstone (25%), travertine (23%), and grey limestone (8%), alongside minor geomaterials (<2%) including basalt, bricks, and calcarenites, locally sourced from Cenozoic and Mesozoic formations around Tetouan. The approach demonstrates that heterogeneous petrography directly governs differential decay: carbonate rocks show high susceptibility to dissolution and biological colonization, whereas detrital stones are prone to granular disintegration, cracking, and scaling. Physical, chemical, and biological weathering act synergistically, amplified by the clay-rich Pliocene terrace and local hygrothermal dynamics. The quantitative assessment of stone deterioration at Tamuda reveals heterogeneous damage, with physical degradation reaching severe levels (between 50% and 75%), while chemical and biological alterations remain low to moderate. Crucially, beyond site-specific diagnosis, the protocol delivers actionable outputs: selection of compatible replacement stones, targeted mitigation strategies for each deterioration type (especially water-driven mechanisms), and a scientific baseline for restoration prioritization. The study further outlines methodological extensions (mineralogical fingerprinting, portable sensor monitoring, and petrographic provenance analysis) positioning this approach as a reference for heritage management across the Mediterranean. By demonstrating how systematic geomaterial inventory becomes an operational decision-making tool, this work shifts heritage conservation from reactive repair to predictive, material-based management, offering a replicable model for archaeological sites in Morocco and beyond.