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

Abstract

Les origines d’Ostie ont fait l’objet de nombreuses études archéologiques et historiques. Selon les auteurs anciens, la fondation d’Ostie est attribuée à Ancus Martius qui aurait régné entre 646 et 616 av. J.-C. Cependant les données archéologiques disponibles à Ostie ne permettent pas de remonter avant le ive/iiie s. av. J.-C. Dans cet article nous nous proposons d’examiner ce désaccord chronologique dans une perspective géoarchéologique. À partir d’une synthèse géomorphologique et chronostratigraphique, on observe que l’éventuelle Paléo-Ostia d’Ancus Martius aurait été fondée à la fin d’une période de forte progradation (ixe et vie s. av. J.-C.) et au début d’une longue période d’érosion du lobe d’embouchure. Au cours de cette même période, le chenal d’embouchure du Tibre migre vers le sud jusqu’au ive/iiie s. av. J.-C. Il semble ainsi inévitable qu’un éventuel noyau de peuplement fondé à l’embouchure même du Tibre à la fin du viie s. av. J.-C. aurait été rapidement affecté par une érosion littorale et possiblement fluviale.

Natural and Cultural Lost Landscape during the Holocene along the Central Tyrrhenian Coast (Italy)

“…An evaporitic level, found in Le Cerquete-Fianello and datable to around 4000 yr BP [79], could be correlated with the 4.2 dry event, which would have temporarily reduced the width of these lakes. The Tiber mouth was probably just north of the current position [35,80,81].…”

“…The individual images illustrate the coastal landscape relating to the period shown on the abscissa of the sea level rise curve. The Tiber delta was an area locally subject to repeated changes (excavation of canals and ports and abandonment of meanders) so as to make it difficult to trace a single sea level rise curve [81]. It was, therefore, decided to draw the curve based on only 14 C datings coming from the peat levels of Maccarese Lake.…”

Palaeotsunami deposits at the Tiber River mouth (Ostia Antica, Italy): Do they really exist?

“…No sedimentological evidence alone should definitively proves a paleo-tsunami signature. Alternatively, we would suggest that the layer identified could be related to through/bar deposits near the palaeoriver mouth of the Tiber River (Salomon, 2013(Salomon, , 2020. Deposits similar to HEE-1 can be identified in almost all cores drilled between Ostia and Fiumicino in depths ranging between 4 to 9 m below the current sea level and related to different progradational phases (Salomon, 2013).…”

“…Sandy shoreface morphologies close to a river mouth are highly mobile and constantly exposed to floods and storms. Additionally, it has been demonstrated that the Tiber River mouth was particularly dynamic during the first part of the 1 st millennium BC: quick progradation shaping a large promontory and river channel migrating toward the south (Bellotti et al, 2011;Milli et al, 2013;Delile et al, 2018;Salomon et al, 2018;Salomon, 2020). Hadler et al (2015) hypothesise that "fluvial sediments were dislocated by a highenergy event within a near-shore deltaic marine environment", and attest to the difficulty in identifying the fluvial and coastal balance in such environments.…”