GNGTS 2014 - Atti del 33° Convegno Nazionale

26 GNGTS 2014 S essione 3.1 to Meso-Cenozoic carbonates have been recognized. The regional geological setting and the seismic interpretation have confirmed that the Banco di Fuori represents a major morpho- structure high, separating the Dohrn canyon from the Magnaghi canyon. It is formed by a Mesozoic carbonate block resulting from the uplift and tilting of the carbonate basement. The carbonatic nature of the structural high is confirmed by its location along the Capri-Sorrento structural alignment and by the lack of significant magnetic anomalies (Aiello et al. , 2005). The interpreted seismic data have been compared with previous structural interpretations on the Banco di Fuori area (Milia and Torrente, 1999). The Banco di Fuori high is bounded southwards by a set of normal faults, N to NE trending, down throwing the Meso-Cenozoic substratum many hundred of meters to the SE and characterized by variable cross-section geometries. The top of the acoustic substratum is downthrown towards SE. The appraisal of the corresponding fault varies from 1300 to 1000 m, while on the eastern profile is 600 m. The variations in the displacement have been interpreted according to the model of Walsh and Watterson (1988), evidencing the fault displacement changes along the strike. It is commonly greatest at the centre of the fault, decreasing to zero at the eastern fault tip in the central part of the Naples Bay, where this structure is buried by younger sediments. One of the main morpho-structures of the Naples Bay is represented by the Dohrn canyon, separating the eastern gulf, where sedimentary seismic units crop out from the western gulf, where the volcanic seismic units prevail. The canyon is articulated into two main branches, the eastern one and the western one, merging in a thalweg having a NE-SW (counter-Apenninic) direction, bounded southwards by the Capri basin. It erodes the Pleistocene relict marine units of the prograding wedges (A and C in the interpreted seismic sections) overlying the Meso- Cenozoic carbonates. Our seismostratigraphic data suggest the occurrence of Meso-Cenozoic carbonates under the canyon thalweg, in the bathyal plain westwards of the Capri island. The carbonatic unit below the Banco di Fuori – Dohrn canyon – Salerno Valley alignment has not been previously pointed out by seismostratigraphic papers on the Naples Bay, suggesting its distribution only in the eastern continental shelf of the Naples Bay, as offshore prolongation of the NW dipping Capri-Sorrento monoclinalic structure (Fusi, 1996). Another main structure is represented by the Capri structural high, whose southern flank is deeply downthrown by the Capri-Sorrento master fault. Its stratigraphic setting is composed of two relict prograding wedges, the A and C seismic units. The Capri structural high is bounded by the Dohrn canyon structure to the NW and by the Salerno Valley to the SE. The regional structure of the Capri structural high is related to the Capri-Sorrento Peninsula structural alignment (D’Argenio et al. , 1973; Perrone, 1988). The southern flank of the structural high is controlled by the Capri-Sorrento master fault. The following structure is represented by the Magnaghi canyon, draining the volcanic and volcaniclastic input coming from the eruptive activity of the Ischia and Procida islands during the Late Quaternary. The canyon erodes the deposits of the Mg unit, characterized by seismic reflectors having a chaotic distribution. A volcanic nature of the Mg unit, genetically related to the Procida volcanic complex, may be assumed. The Magnaghi canyon basin is a sedimentary basin adjacent to the Magnaghi canyon and representing a depositional area, where Pleistocene-Holocene deposits drained by the canyon in its initial thalweg have accumulated. This depositional area, previously unknown, has not been mentioned by previous papers dealing on the seismic stratigraphy of the area (Fusi et al. , 1991; Milia and Torrente, 1999). Another main structure is the Capri Basin, which is a deep basin localized in the Tyrrhenian bathyal plain southwards of the Dohrn canyon. It is filled by Pleistocene-Holocene sediments, thick about 0.7 s (twt), unconformably overlying Meso-Cenozoic carbonates. The basin filling is characterized by parallel and laterally continuous seismic reflectors, overlying an acoustically-transparent seismic facies, interpreted as the Meso-Cenozoic carbonates. The seismic stratigraphy of the Capri Basin is relatively unknown, excluding the paper of Milia and Torrente (1999), identifying seven depositional sequences in the basin filling. Two lowstand