Alluvial fan development mirrors settlement dynamics in the peri-urban surroundings of ancient Pergamon, western Türkiye

Abstract The ancient metropolis of Pergamon in Asia Minor underwent profound transformations from the Hellenistic to the Roman Imperial period, affecting the peri-urban surroundings. This study aims to identify phases of landscape development in the Araplı alluvial fan and its peri-urbanized catchment. We examined seven sediment cores from the Araplı alluvial fan at the fringe of the Kozak horst and the Bakırçay graben using macroscopic and geochemical sediment analyses and radiocarbon dating. Our results show that the Araplı area was characterized by a floodplain with seasonal water bodies in the Early Holocene. Following a general climatic trend towards lower precipitation and the onset of human activities in the region during the Early Bronze Age, the deposition of overbank fines indicates dominant aggradation of the Bakırçay alluvial plain. Intensified human activities in the peri-urban surroundings of Pergamon during the Roman Imperial period likely increased soil erosion, triggering the burial of the Bakırçay alluvial plain by the prograding Araplı alluvial fan. This change in sediment dynamics is more pronounced in the Araplı area than in other rural areas in the Pergamon micro-region studied to date. In conclusion, our study emphasizes the local variability of sediment dynamics in a micro-region undergoing profound transformations during antiquity, where, as today, peri-urban areas were focal points of land degradation.