New seismo-stratigraphic and marine magnetic data of the Gulf of Pozzuoli (Naples Bay, Tyrrhenian sea, Italy): inferences for the tectonic and magmatic events of the Phlegrean Fields volcanic complex (Campania)

A detailed reconstruction of the stratigraphic and tectonic setting of the Gulf of Pozzuoli (Naples Bay) is provided on the basis of newly acquired single channel seismic profiles coupled with already recorded marine magnetics gathering the volcanic nature of some seismic units. Inferences for the tectonic and magmatic setting of the Phlegrean Fields volcanic complex, a volcanic district surrounding the western part of the Gulf of Naples, where volcanism has been active since at least 50 ka, are also discussed. The Gulf of Pozzuoli represents the submerged border of the Phlegrean caldera, resulting from the volcano-tectonic collapse induced from the pyroclastic flow deposits of the Campanian Ignimbrite (35 ka). Several morpho-depositional units have been identified, i.e. the inner continental shelf, the central basin, the submerged volcanic banks and the outer continental shelf. The stratigraphic relationships between the Quaternary volcanic units related to the offshore caldera border and the overlying deposits of the Late Quaternary Depositional Sequence in the Gulf of Pozzuoli have been highlighted. Fourteen main seismic units, both volcanic and sedimentary, tectonically controlled due to contemporaneous folding and normal faulting have been revealed by geologic interpretation. Volcanic dykes, characterized by acoustically transparent sub-vertical bodies, locally bounded by normal faults, testify the magma uprising in correspondence to extensional structures. A large field of tuff cones interlayered with marine deposits off the Nisida island, on the western rim of the gulf, is related with the emplacement of the Neapolitan Yellow Tuff deposits. A thick volcanic unit exposed over a large area off the Capo Miseno volcanic edifice is connected with the Bacoli-Isola Pennata-Capo Miseno yellow tuffs, cropping out in the adjacent onshore sector.