This research was carried out to determine the changes to the coastline and to the natural environment that occurred during the Holocene Epoch around the ancient city of Teos. Alluvial core drilling method was used to determine the paleogeographic conditions of the ancient city and its geoarchaeological results. 11 core drillings were carried out on two lines in the K-G and B-D direction on the coastal plain of cayirarasi in the east of the city.The paleogeography and geoarchaeology evaluations were made based on the data obtained after the sedimentological, element and micropaleontological analyzes of the drilling samples. According to the first results, the layers of the coastal plain fillings of cayirarasi are marine sediments, coastal swamp environment, cayirarasi flood plain and Teos culture fillings. C14 dating from Teos-2019-01 drilling determined the year to be 3320 BP(Calibrated). Accordingly, it was found that the depression in the Cayirarasi plain was a strait-like sea extending towards the K-G direction in the Middle Holocene and that the Ekmeksiz hill where the ancient city of Teos was located was an island. Our findings determined that the section of Teos antique city and harbor extending towards the cayirarasi depression had been covered with floods of Yassicay and slope floods since the Bronze Age.