A COASTAL SEDIMENT RECORD OF THE CONSTRUCTION OF ALEXANDER THE GREAT'S CAUSEWAY, CLAZOMENAE, TURKEY

In 334 BC, Alexander the Great built a 400 m long causeway connecting Karantina Island with the Turkish mainland to defend the city of Clazomenae against Persian attack. The causeway interrupted the dominant west-to-east long shore currents, creating a sheltered embayment on the leeward (eastern) side of the barrier. A detailed multi-proxy study was conducted on 6 sediment cores to document changes in the coastal environments resulting from the causeway construction. Three distinct depositional phases were recognized based on core lithofacies, grain-size and magnetic properties.

The pre-causeway environment is recorded by a lowermost sequence of coarse-grained sand with abundant shell fragments (Unit D) and laminated silt (Unit C). These sequences record deposition of sands in a high-energy shoreface environment followed by laminated muds in a shallow lagoonal setting. The onset of causeway construction is identified by a shift to finer mean grain size within an overlying organic-rich silty mud layer (Unit B), signaling the interruption of long shore transport. The transition is associated with the appearance of pottery fragments, masonry and abundant olive pits in Unit C. The uppermost unit (A) consists of bioturbated muddy silt and fine sand with abundant Poseidonia sp. fragments recording low energy sedimentation in the back-barrier. The results demonstrate that the building of the causeway dramatically altered the coastal sediment budget, contributing to accelerated sedimentation and progradation of the coastline to the east of the barrier.