Structural settings of the carbonatic "basement" in the Gulf of Naples and its relationship with magma uprising

The carbonatic «basement» of the Gulf of Naples, a peri-tyrrhenian basin located on the western side of the Southern Apenninic chain, was studied in detail by means of seismic reflection profiles both on the mainland and in the sea. The carbonatic «basement» dips toward the north-west with an angle of 10° and is affected by brittle extensional tectonics. This structural setting is related to the extension of the Tyrrhenian Sea, which caused the development of horst and graben-like structure along the western margin of the Apennines. Some normal faults with a regional relevance were recognised: 1) a N110° trending fault responsible for the sinking of the carbonatic «basement» below Mount Somma-Vesuvius; 2) a N10° trending fault, along which five submarine volcanoes are aligned; 3) a N70° fault, which separates the Gulf of Naples from the Gulf of Salemo. The first two faults, arranged radially with respect to the shallow magmatic chamber of Phlegraean Fields, are interpreted as the main uprising route for magma in this area. The carbonatic «basement» cannot be recognized in seismic profiles in the Phlegraean area; a tectonic feature responsible for this is hypothesized