OXYGEN ISOTOPIC COMPOSITION OF HARVESTED MOLLUSK ASSEMBLAGES FROM IFRI OUDADANE, NE MOROCCO

The timing and impact of climate change on the development of food production lifestyle in NW Africa is still poorly understood because of the limited number of depositional sites containing reliable, complete, and accessible archaeological records. The site of Ifri Oudadane, located in NE Morocco on the Alboran Sea, is one of the few continuous archeological records in the western Mediterranean that captures the transition from the Epipaleolithic (hunting-gathering) to the Neolithic (food-production). Archeological layers contain abundant and well-preserved marine mollusk shells of the topshell, Phorcus turbinatus (Gastropoda: Trocoidea), which offer a wealth of cultural and environmental information. We analyzed the oxygen isotopic composition of shells to reconstruct the sea surface temperature (SST) and assess whether the development of food production during the Neolithic phase coincided with warming conditions. Calculated SST from each individual shell indicate that Phorcus grew relatively continuous during both winter and summer seasons, and the magnitude of seasonality, i.e., the difference between the minimum and maximum temperature recorded in each shell, ranged between 8℃ and 12℃, coinciding with the degree of seasonality at present. The average annual SST for all measured Neolithic shells remained consistently warm ranging from 20℃ and 22℃. These results are on average, two-to-four degrees warmer than modern SST in the Alboran Sea (i.e., 18℃, on average). The data presented here supports the hypothesis that warmer temperatures during the Neolithic could have partially triggered the rise of food production in Morocco, and for extension, NW Africa.