Alluvial geoarchaeology of a small drainage basin in western Anatolia: Late Holocene landscape development and the question of the mouth of the Paleo-Bakırçay

Late Holocene landscape evolution in the Geyikli basin, a sub-catchment of the Bakırçay basin on the West Anatolian Coast, and its implications for the plaeogeography of the environs of ancient Pergamon (modern Bergama), were studied by a combination of archaeological and geographical investigations. The study aims to investigate whether the “Dörpfeld Scenario” of the paleogeographical situation in the Lower Bakırçay Valley is true or not. The scenario postulates that during the Late Holocene, an alluvial fan, fed from the Geyikli valley, progressively closed a topographical constriction between the Aegean Sea and a supposed paleo-gulf that occupied the Lower Bakırçay Valley. Initially, this caused the development of an inland lake, and finally the shift of the mouth of the Paleo-Bakırçay from a northern position to its modern southern position.The lithostratigraphy of four sediment outcrops in the Lower Geyikli Basin and in the topographical constriction between the Aegean Coastal Plain and the Bakırçay Valley shows that during the past ca. 1950 years, the Lower Geyikli Valley was inhabited by a braided river with a highly dynamic depositional system. Sedimentation totalled about 4–6 m in the past 1950 years, indicating a “drowning” of the landscape in terrestrial sediments. In recent times, gravel mining has led to a deformation of the valley floor, and the Geyikli's fluvial terrace has become inactive. The lack of any sediment related to a Paleo-Gulf or a Paleo-Lake inside the Bakırçay Basin, as well as the lack of any sediments of a northern Paleo-Bakırçay, documents that the “Dörpfeld Scenario” does not apply for the past 1950 years. Archaeological findings show that the Geyikli Basin was intensively settled in historic times, but there is no evidence that the Geyikli Basin was anthropogenically deformed in a way that could have contributed to the “Dörpfeld Scenario”.