Harbor geoarchaeology and urban change in the ancient Knidia (SW Türkiye)

The relationship between the two major centers on the Datça Peninsula at Burgaz and Knidos—and the potential shift in population and centrality from one to the other around the 4 th c. BCE—casts a long shadow over the history of the region known in antiquity as the Knidia. What prompted the shift remains unclear in the historical records, but it must have represented a strategic collective decision and major civic investment. Underwater archaeological excavations revealed a 3-m stratigraphic section in the earliest harbor basin of Burgaz, offering a window into the environmental context in which Burgaz flourished and gave way to Knidos at the tip of the peninsula. This study investigates whether socio-environmental systems contributed to this shift, focusing on changes in natural conditions and lead contamination. Anthropogenic lead excesses reveal a first isotopic fingerprint of exogenous lead, linked to central Greece and the Cyclades before the 2 nd c. BCE. Knidos, strategically located at the intersection of Aegean and eastern Mediterranean and Levantine maritime routes, served as a pivotal hub in these networks. During the Roman centuries that followed, though, the source of lead reoriented towards the northern Aegean, offering a new window into potential changes in Knidos's function as an intermediary hub in the emerging imperial trade system. Following the foundation of the city, the basin was excavated around 2600 cal BP, after which it experienced a twofold increase in seafloor aggradation due to the creation of new accommodation space and increased terrigenous inputs driven by Burgaz's pivotal role in the region's agricultural economy. Despite the development of other facilities at Burgaz, Knidos, and elsewhere along the coast, the maintenance of this original harbor continued, with a second dredging phase in Late Antiquity. This may reflect a deliberate effort to sustain a multi-scale harbor system across the peninsula. • First sediment record from Knidos harbor provides new insights into coastal and urban change on the Datça Peninsula. • Geoarchaeological data show anthropogenic impacts dating back to the 8 th c. BCE. • Pb isotopic data support steady Cycladic/Greek lead sourcing until the 2 nd c. BCE, then a Roman shift to the northern Aegean. • Evidence supports a long-lived multi-basin harbor system fostering regional integration from Archaic to Late Antiquity.