Holocene natural evolution and anthropic influence in the mouth of Ribeira de Alcântara, Tagus Estuary (Lisbon)

Abstract

This work aims to characterize the environmental and morphological evolution of the estuarine margin at the mouth of the Ribeira de Alcântara (Tagus Estuary, Lisbon) during the Middle and Late Holocene, through the sedimentological study of sediments collected in Alcântara during the archaeological excavations that took place at Lote 9 – Loteamento Alcântara Poente. Five sedimentological units with different characteristics were identified (US1 to US5), reflecting the evolution of this estuarine margin. Radiocarbon dating performed on a Panopea glycimeris shell found 4.6 meters below the current mean sea level in life position produced a date between 6254 and 5920 cal BP. At the top, archaeological findings in the area allow the dating of several occupation events of the margin from at least the 13^th century. Since the beginning of the Holocene to the present day, the estuarine margin has advanced over the Tagus Estuary by about 500 meters.