Active deformation and volcanism offshore campi flegrei: new data from seismic reflection profiles

Abstract

The reprocessing of old seismic reflection profiles represents an useful and costeffective tool to constrain the geologic structure of a complex tectonic area such as the inner shelf of Bay of Naples. Bruno et al., 2002 reprocessed a seismic dataset collected by OGS (Osservatorio Geofisico Sperimentale-Trieste) during 1973, reducing some of the limiting effects of the acquisition phase to gain more information on the deep part of Bay of Naples and Campi Flegrei structure. In this study, the interpretation concerned 13 seismic lines reprocessed by Bruno et al., 2002 that spread over an area of about 2000 Km² extending from the northern coast of Ischia and Procida Island up Sorrento Peninsula. The interpretation of seismic profiles allowed to delineate a broad geo-volcanological and structural framework of the Campi Flegrei area and to reconstruct the Quaternary tectonic and stratigraphic evolution in the Campi Flegrei area presenting a five-stage scenario. Campi Flegrei area is well-know for its active volcanism but the crustal structure beneath the Campi Flegrei-Ischia ridge is still debated. Our study confirms previous investigations (Finetti et al., 1974; Bartole et al., 1984; Oldow et al., 1993; Hyppolite et al., 1994; Milia et al., 1999; Bruno, 2003; Aiello et al., 2005) on the structure of the Gulf of Naples basin, but bring new insights into the way magma is stored within the crust. In Campi Flegrei offshore area, seismic lines permitted to define two episodes of magma emplacement occurring during Lower Pleistocene and Middle-Upper Pleistocene, respectively. This permit to affirm that volcanism in the Neapolitan area is a long process operating episodically from the Lower Pleistocene onwards. Intrusive processes could have ultimately be responsible for the resurgent structure of Ischia; the interpretation of seismic lines permitted, in fact, to unravel the mechanics of uplift of Ischia Island Recently gathered high resolution multi channel reflection seismics were processed and interpreted to reconstruct the younger depositional history within Pozzuoli Bay. The already established stratigraphy for the last 15 kyrs from the submerged part of Campi Flegrei could be validated in the new seismic data, primarily by means of seismic reflector terminations. Moreover, the high vertical and lateral resolution in the range of one meter contributed to the published acoustic data in terms of a more detailed classification of single seismic units. Processing and interpretation of high resolution multi-channel seismic profiles acquired in Pozzuoli Bay allowed, in fact, to reconstruct the young depositional history in Campi Flegrei offshore area and permitted to recognize volcanic banks and buried volcanic structures which correspond to small laccolith-type magmatic intrusions. The data clearly shows that in some areas of the Gulf of Pozzuoli recent deformative processes are still present acting.