Palaeoenvironmental evolution and decline of the harbours of the Roman and Early Byzantine city of Elaiussa Sebaste (southeastern Turkey): natural and anthropic causes

The ancient city of Elaiussa Sebaste, currently Ayaş, is located on the southeastern coast of Turkey. It was one of the main trading Mediterranean harbours from the Augustan period until the early Byzantine era. The Arab invasion in the 7th century ce marked its definitive abandonment. A significant historical topic concerns the palaeoenvironmental evolution of the northern and southern harbours of Elaiussa Sebaste, including their decline and burial. An interdisciplinary study analysed six cores drilled in the current plains corresponding to the former harbour basins. A geoelectrical study, integrated with borehole stratigraphy, reconstructed the geometry of the carbonate bedrock that forms the accumulation base of the marine sediments. Sediments deposited from the 8th century bce to the 6th century ce include the development phases of the ancient city from the 3rd century bce onwards. Sedimentology, micropalaeontology (foraminifers, ostracods), palaeobotany (pollen, non-pollen palynomorphs, microcharcoals, plant macroremains) and Pb isotopes provided a model of the environmental evolution in both harbour basins. The main harbour expansion phase, marked by a change in Pb concentration, is hypothesized to have occurred between 140 and 220 ce, which is consistent with the historical sources indicating the development of the city during the mid-Roman Imperial period.