Le unità piroclastiche tardo-quaternarie nel Golfo di Napoli

Late Quaternary pyroclastic units in the Bay of Naples (Italy)

Abstract

The interpretation of high resolution seismic reflection data permitted the recognition of two units characterized by reflection-free seismic fades in the peri-Tyrrhenian Bay of Naples. On the basis of their map distribution, physical continuity and thickness, these seismo-stratigraphic units are correlated to the two largest Late-Quaternary pyroclastic units outcropping in the Campanian Plain: Campanian Ignimbrite Auct. (35 ka BP) and Neapolitan Yellow Tuff Auct. (11.5 ka BP). The Campanian Ignimbrite is spread around the present shelf of the Bay of Naples (from Naples to Sorrento) and its top is 100-150 meter deep. It displays a cross-sectional wedge shape due to an asymmetric subsidence pene-contemporaneous to the activity of a NW-trending growth normal fault close to the Vesuvius coast. It is suggested that during the eruption of the Campanian Ignimbrite about 35 ka BP the present central shelf of the Bay of Naples was a transitional to sub aerial environment because of: i) progradational geometry of the underlying stratigraphic units, ii) high subsidence rates, ill) position of the sea level 35 ka BP. The Neapolitan Yellow Tuff is documented in the shelf of the Northwest Bay of Naples and is suggested that it was emplaced below the sea-level at the depth of about -70 m. This pyroclastic unit is affected fay post-11.5 ka BP NE-trending normal faults located south of the Posillipo coast. The Campanian Ignimbrite (35 ka BP) end the Neapolitan Yellow Tuff (11.5 ka BP) are affected by NW- and NE-trending faults which are linked to the regional fault systems that controlled the Quaternary tectonic evolution of the peri-Tyrrhenian Campanian margin.