Rapid changes of the accommodation space in the Late Quaternary succession of Naples Bay, Italy: the influence of volcanism and tectonics

Naples Bay is an extensional basin that experienced an important reactivation of regional faults associated with the emplacement of thick volcanic units during the Late Quaternary. This paper is based on the interpretation of a strictly spaced seismic grid that permitted the reconstruction of the paleogeography of Naples Bay before the onset of volcanic activity and the paleogeographic changes following the voluminous volcanic unit's emplacement. Using the estimated paleo-water depth we calculated curves of space filled with volcanics and sediments, subsidence and accommodation space in order to understand the relationship between volcanic activity and tectonic subsidence at three selected sites (Penta Palummo, Pozzuoli Bay and offshore Vesuvius) of the Naples Bay basin. Repeated volcanic events and rapid basin infill were documented for the Penta Palummo area that underwent a dramatic physiographic change, changing from a slope-basin (in the Middle Pleistocene) to a shelf (during Late Quaternary). A more gradual physiographic change from a slope-basin to a shelf occurred in Pozzuoli Bay where the basin infill was caused by clastic vertical aggradation, later followed by a tectonic subsidence related to post-15 ka faulting and folding. Finally, the area offshore Vesuvius remained a shelf and did not experience any physiographic change as a rapid increase of accommodation space was balanced by the contemporaneous filling of the space due to the emplacement of Upper Pleistocene ignimbrites. These findings question the occurrence of a caldera offshore Campi Flegrei as reported by previous workers.