Detection of active fluid emissions in the Naples bay (Sourthern Italy): first hydroacustic evidences

The Naples Bay is a Neogene-Quaternary basin located between the southern Apennines fold and thrust belt and the Tyrrhenian basin. This marine sector is characterised by significant Quaternary extension and intense volcanism at the Ischia and Procida islands, the Campi Flegrei and Somma-Vesuvius volcanic complexes started in the latest Pliocene-Early Pleistocene (1.87 MA; Vezzoli, 1988) controlled by regional NE-SW and subordinately NW-SE fracture systems. The whole Campanian fluid vent system has been localised through the major structural discontinuities and mainly consists in typical hydrothermal degassing (Chiodini et al., 2001). High resolution hydroacoustic profilers were used by Passaro et al., (2014) to identify and localize the presence of active fluid vents (AFV) from the seafloor, coupled to Remote Operative Vehicle (ROV) direct observations and analyses of CTD profiles that showing no significant gradients in temperature but decrease of pH near the seafloor. The study includes the mapping of several (>50) fluid emissions located in the -71/-158 m depth range, and spatially distributed into four main clusters. Three of the described clusters are located along the margin of the Somma-Vesuvius volcanic complex. The fourth AFV cluster was detected at the morphological - high, located about 8 km south of Naples (Banco della Montagna - volcanoclastic diapiric structure; Sacchi et al., 2001). The occurrence of AFV suggests a genetic linkage between seafloor morphologies and the main lithospheric tectonic lineaments.