Sedimentology and geoarchaeology of the Yenikapi (Istanbul) excavation area: Investigate traces of catastrophic event (tsunami-storm-flooding) affecting the sequence, deposited in the area

During excavations of Marmaray Project which is carried out in the Yenikapi (İstanbul), Byzantine port (Port of Theodosius) was exposed. Port of Theodosius was built for the flourishing new capital of the Roman Empire between the years 379-395 AD. This study was performed in the field of archaeological excavations in Yenikapi. The sequences at Yenikapı excavation area are divided into nine separate units.The research is intended to investigate the traces of geological event in the Sea of Marmara (sea level changes, earthquakes, tsunamis) last 8500 years and identify the sedimentary processes (erosion, transport, storage, etc.). In this study, situation of archaeological artifacts investigated in relation with sedimentary sequence were established through benefit of sedimentological and geoarchaeological studies.Numerous observations and measured stratigraphic sections were prepared in the study area to investigate the detailed stratigraphy of the geological units. Within the scope of this study collected data evaluated and two cross sections have been prepared. C-14, OSL, clay (XRF, XRD) analysis were performed on the samples collected from the sedimentary sequences and archaeological artifacts in the excavation area. The results of C14 analyses shows that; the age of unit 1 is between 6080 - 5580 BC, the age of unit 4 is between 430-550 AD, the age of unit 6 is between 810-960 AD.The current direction is from west to east at the base of the swamp and from north to south in middle and upper section of the swamp. Depositional age interval of unit 1 is between 7500 - 8500 BP. There are evidence indicating tsunami in level of unit 4a and 4b. Level of unit 4a take place in the limited section but 4b located all over the place of excavation. The tsunami, which is occurred during deposition or last stage of unit 4a, is disturbed all pre-tsunami sediments including sections of unit 3 and change their initial- position, deformed sequences, caused soft deformation and mass movement, and re-deposited as chaotic debris. Because of tsunami effect the terrestrial and marine sediment is being extensively mixed in unit 4b.