New challenges in archaeopalynology: Pollen analysis on Roman bivalve shells from south-western Europe and North Africa

The European flat oyster (Ostrea edulis) is a native species that was consumed as a luxurious product by the Romans. In the Strait of Gibraltar area, between southwest Iberia and North Africa, numerous oyster shells have been found in Roman archaeological sites located in both, the Atlantic Ocean and the Mediterranean Sea. The origin of these oysters is unknown, as so if they were farmed or harvested in the wild and/or even imported for consumption. This study presents the results of pollen analysis of oyster shells from six archaeological sites in the Strait of Gibraltar area dated between the 1st and 6th centuries AD. This is the first time that such research is undertaken in the Iberian Peninsula and North Africa; the second worldwide for a discipline rarely known until now: conchopalynology. Our study suggests that differences observed in pollen spectra could be used to identify the origin of the consumed specimens, i.e. where they were grown or harvested, discriminating whether oyster shells originated from the Mediterranean Sea or the Atlantic Ocean coastline. •We present the conchopalynology, the study of pollen content of fossil mollusc shells.•Pollen content of fossil oysters is valid for vegetation reconstruction.•Their Mediterranean or Atlantic provenance was elucidated by ordination analysis.•It have been also possible to discriminate between harvested or cultivated oysters.