Evidence of open-air late prehistoric occupation in the Trieste area (north-eastern Italy): dating, 3D clay plaster characterization and obsidian provenancing

Abundant clay burnt plaster remains and a few flaked tools, including an obsidian artefact, found on the ground surface not far from Trieste (north-eastern Italy) provide rare evidence of a possible prehistoric open-air occupation in the area. To confirm and detail their ancient origin, a plaster sample has been dated between 4000 and 2000 B.C. via thermoluminescence. Outer and inner structure of selected plaster samples has been characterized using several techniques, i.e. X-ray diffraction, scanning electron microscopy and X-ray computed micro-tomography, obtaining information about their production technology. The last technique has allowed to image and virtually extract vegetal remains and imprints. Their 3D morphological study has contributed to collect information about the ancient environment and has provided clues to define the plaster production season. The provenance of the obsidian artefact from Lipari Island, revealed by prompt gamma activation analysis, suggests that the finding site was part of long-distance connection systems and probably worked as intermediate point between the north-eastern Adriatic coastal areas and the inner Karst plateau.