Functional study of organic residues related to pottery vessels to explore exploitation of natural products during the Early Iron Age in Corsica
Résumé
The excavation of the site of Cuciurpula (South Corsica, France) revealed a significant amount of potsherds, often bearing visible surface crusts, sometimes very thick. This exceptional case in the Mediterranean region, suggesting a good preservation of organic substances, provided a unique opportunity to address questions related to natural organic substances exploited in Corsica during the first half of the 1st millennium BC.
Organic residues from three houses of the site, both preserved in pottery walls and in charred crusts adhering to the surface, have been examined macroscopically and studied by molecular analysis (GC and GC/MS) to investigate the function of both ceramic vessels and natural organic products.
Adhesive substances (birch bark tar and conifer resin sometimes mixed together or with beeswax) were mainly extracted from visible charred residues. The diversity of their appearance, adherence to the surface and distribution on the sherds suggests that these substances were not only contained and transformed in ceramics, but also used during pottery manufacture and maintenance. Their study provided thus exceptional data to understand the complex technical system related to adhesives, from their manufacture process (including heating and mixing of substances) to their various functions (repair of pottery, coating of inner or outer surfaces).
Invisible residues absorbed inside ceramic walls provided data to understand pottery use and highlighted the wide diversity of substances contained and processed in ceramic vessels: animal fats, plant oils and waxes, beeswax, and conifer resin. Pottery function was investigated using several proxies: (i) natural origin of the substances contained in ceramic vessels; (ii) macroscopic and molecular markers of heating; (iii) potential waterproofing of the walls; and (iv) spatial distribution inside the house. This study revealed a clear distinction between pottery used for culinary and technical activities, apparently employed in the same area of activities at the household scale.