Late-Quaternary volcanism and transtensional tectonics in the Bay of Naples, Campanian continental margin, Italy

The Campanian continental margin is characterised by asymmetric half grabens and large-volume volcanic deposits. Vesuvius and Campi Flegrei are active volcanoes located along the coast of Naples Bay along one of these half grabens. The interpretation of an extensive set of seismic reflection data allowed to reconstruct the stratigraphy and structural pattern in Naples Bay and their relationships with volcanism. The stratigraphic succession is characterised by a complex architecture due to the presence of 157 Ka old submarine and subaerial vents, pyroclastic flow units associated to the Campanian Ignimbrite and the Neapolitan Yellow Tuff, and numerous tuff cones younger than 12 Ka. These volcanic units occur within marine sediments deposited during the late Quaternary sea level oscillations. The structural pattern is characterised by late Quaternary NE- trending normal faults, NW-trending transtensional faults, E-W trending left-lateral faults and WNW-ESE directed folds. The overall fault kinematics and the evaluated very high displacement rates are consistent with an E-trending left-lateral transtensional shear zone located between 41degrees and 40degrees N latitude. The relationship between volcanism and tectonics in the Bay of Naples is explained with block rotation associated with this shear zone. Finally, tectonic and stratigraphic data argue against the occurrence of a caldera in the Bay of Naples.