The submerged structure and stratal architecture of the Neapolitan Yellow Tuff(NYT) caldera, offshore the Campi Flegrei, (Eastern Tyrrhenian Margin):new insights from high resolution seismics and gravity core data

The Campi Flegrei is an active volcanic area defined by aquasi-circular depression that covers some 200 km2 of the coastalzone of SW Italy, a large part of which develops off the Naples(Pozzuoli) Bay (Fig. 1). The area has been active at least since 60ka BP ( Pappalardo et al., 1999), and is structurally dominated by acaldera, 6 km in diameter, associated with the eruption of theNeapolitan Yellow Tuff (NYT), a 40 km3 Dense Rock Equivalent(DRE) ignimbrite (Scarpati et al., 1993) dated at ca 15 ka BP(Deino et al., 2004), that covered the district now occupied by thecity of Naples, the Campi Flegrei and a large area of thecontinental shelf off the Pozzuoli Bay.The volcanological evolution of the NYT caldera as been longdescribed on the basis of outcrop and subsurface studies onland(Rosi & Sbrana, 1987; Orsi et al., 1996, 2004 and referencestherein; Di Vito et al., 1999; Perrotta et al., 2006; Fedele et al.,2011), but its offshore morphology, detailed structure and recentstratigraphic setting are still poorly understood.In this study we integrate geological and geophysical data ofdifferent resolution/penetration obtained from high-resolutionreflection seismic profiles (Sparker and Chirp source) with gravitycore and swath bathymetry to better constrain the shallowstructure, stratigraphic architecture and latest Quaternary toHolocene evolution of the submerged sector of the NYT calderaoff the Pozzuoli Bay.Our data clearly image, for the first time, the offshore geometryof the NYT caldera ring-fault zone, as well as the style and timingof volcano-tectonic deformation associated with the late stageevolution of the NYT inner caldera resurgence. Our interpretationsuggests that since 15 ka the offshore sector of NYT inner calderaunderwent significant deformation and uplift (with minorsubsidence episodes) that occurred at almost the same rate as thepost-glacial sea-level rise. Particularly, the inner Pozzuoli Baystarted to deform soon after 15 ka BP, when sea-level rise wasinitially faster than uplift. This caused a general increase of theaccommodation space that was progressively filled up byvolcaniclastic sediments. Since ca. 8 ka BP, along with the midHolocene decrease in the rate of the sea-level rise, the early NYTresurgent structure was then uplifted up to the sea-level or even topartial subaerial exposure. From ca. 8 to 5 ka BP two distinctlayers of volcaniclastic resediments, mostly represented by gravityflow deposits, formed throughout the Bay. A significant post-Roman (post 2 ka BP) subsidence phase of ca 10 m is thenrecorded offshore Pozzuoli by the drowning of the infralittoralprograding wedge below the present-day fair-weather wave base.REFERENCESDeino AL, Orsi G, de Vita S, Piochi M (2004) The age of the Neapolitan YellowTuff caldera-forming eruption (Campi Flegrei caldera—Italy) assessed by40Ar/39Ar dating method. J. Volcanol. Geotherm. Res. 133, 157–170.Di Vito M., Isaia R., Orsi G., Southon J., de Vita S., D’Antonio M., PappalardoL., Piochi M., 1999. Volcanism and deformation since 12,000 years at theCampi Flegrei caldera (Italy), J. Volcanol. Geotherm. Res. 91 (2-4), 221-246.Fedele L., Insinga D.D., Calvert A.T., Morra V., Perrotta A., Scarpati C., 2011.40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy):toward a new chronostratigraphic reconstruction of the Holocene volcanicactivity. Bull. Volcanol. 73, 1323-1336.Orsi G, de Vita S, Di Vito M, 1996. The restless, resurgent Campi Flegrei nestedcaldera (Italy): constraints on its evolution and configuration. J. Volcanol.Geotherm. Res. 74, 179–214.Orsi G.,