Holocene Palaeo-Geographical Evolution of the Sele River Alluvial-Coastal Plain: New Morpho-Sedimentary Data from Poseidonia-Paestum Area

The Sele river plain is located along the western Tyrrhenian margin of the southern Apennine Chain and is defined seawards by a straight sandy coast formed during the Last Interglacial (Tyrrhenian stage, OIS 5e) and the Holocene. It is characterized by the presence of beach-dune ridges which to the rear interfinger with lagoonal and fluvio-palustrine deposits. This belt was accreted progressively and represents the evolution of a barrier-lagoon system shifted alternatively landward and seaward. In this work, we summarize the main results relative to the Holocene evolution of the Sele river coastal plain along the coast in front of the archaeological area of Poseidonia-Paestum, where the knowledge has been improved by two new cores and by many collected archaeo-tephro-stratigraphical data. The area was affected by the Holocene marine transgression that formed cliffs that cut the travertine deposits. During the second part of the Holocene the shoreline shifted seaward and a lagoonal-beach bar system (Fossa Lupata) formed. The archaeological remains of Poseidonia (VI cent. B.C.) and the Agnano Monte Spina tephra layer (4.1 ky BP) confirm the presence of this morpho-sedimentary system during this time interval. After this period, and mostly after the deposition of the A.D. 79 tephra, the shoreline shifted seaward and an additional beach ridge was formed, while the flat area of Fossa Lupata, was rapidly aggraded and dried up.