An integrated stratigraphical approach to the Middle Pleistocene succession of the Sessano basin (Molise, Italy)

An integrated stratigraphical approach was applied to the Sessano sedimentary succession (Molise), investigated through an 80-m core and an 11-m trench section. The lithostratigraphical study allowed reconstruction of the palaeoenvironmental conditions during the existence of a palaeo-marsh. Based on tephrostratigraphical analysis, the significant volcanoclastic inputs recorded along the Sessano succession were correlated to the explosive activity of the nearby Roccamonfina volcano and in particular to the high-K series (HKS) period of activity, lasted from 546 to 364 ka. The 40Ar/39Ar age of 437.9 ± 1.9 ka obtained at the base of the trench section, which stratigraphically overlaps the core succession, confirms the tephrostratigraphical model and indicates that the marsh dried up during the glacial phase of Marine Isotope Stage (MIS) 12. On this basis, the glacial-interglacial cycle recognised in the core through pollen analysis was ascribed to MIS 14 and 13, while the interglacial phase identified at the core base was tentatively ascribed to MIS 15. The duration of the marshy phase was estimated between 130 and 150 ka. The floral composition of the pollen spectra shows a more modern character with respect to coeval pollen records from Campania, confirming that the heterochronous disappearance of the last subtropical elements from Italy had a latitudinal character.