Les origines d’Ostie : quelles interactions avec la dynamique d’embouchure ? (Delta du Tibre, Italie)

The origins of Ostia have been the subject of numerous archaeological and historical studies. According to ancient authors, the foundation of Ostia is attributed to Ancus Martius who would have reigned between 646 and 616 BCE. However, archaeological data available at Ostia do not support the existence of the city before the 4th-3rd century BCE. In this article we propose to question this chronological disagreement through a geoarchaeological perspective. Based on geomorphological and chronostratigraphic data available for the Tiber delta, we observe that the timing of the foundation of Paleo-Ostia by Ancus Martius corresponds to the end of a period of strong progradation (9th – 6th BCE) and to the beginning of a long period of erosion of the river mouth promontory. During this same period, the lowermost channel of the Tiber migrated towards the south until the 4th – 3rd century BCE. Thus, it seems inevitable that any settlement founded at the mouth of the Tiber at the end of the 7th century BCE would have been eroded by the combined action of the river and the waves in the middle of the 1st millennium BCE.