Active deformation and volcanism offshore Campi Flegrei, Italy: new data from high-resolution seismic reflection profiles

The interpretation of high-resolution seismic reflection profiles permitted the identification of many geologic features in the inner shelf of Pozzuol i Bay. This area corresponds to the offshore of Campi Flegrei: a classicall y active volcanic area that experienced earthquakes and meter-scale vertica l ground uplift before the 1538 Monte Nuovo eruption and in the period from 1970 to 1985. The detected undersea features include two small debris flow s that are located in a submarine valley in the western part of Pozzuoli Ba y. They may be the result of a pyroclastic dow and a pyroclastic surge that entered the sea. The younger debris dow in the uppermost marine deposits o f Pozzuoli Bay formed during the 1538 Monte Nuovo eruption, and the older d ebris flow during the 3.8 ka-old Averno eruption. Other features detected b y our survey are an undersea 8 m-high and 1 km-wide cryptodome, correspondi ng to a near-surface intrusion, located off Pozzuoli, that warped post-4 ka marine deposits. The interpretation of the cryptodome is based on seismic facies analysis, deformation geometry and correspondence to a magnetic high . It is suggested that this undersea dome formed during the uplift phases a ssociated with the 1538 Monte Nuovo eruption and the two more recent bradys eismic crises of 1970-1972 and 1982-1984. Surface-breaking faults (with max imum vertical offset of 1 m) were recognized in very shallow waters near th e coast of Pozzuoli. It is suggested that some of these faults were active during the 1982-1984 bradyseismic earthquake sequence. (C) 2000 Elsevier Sc ience B.V. All rights reserved.