GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 3.1 25 by the Magnaghi canyon. The third domain is represented by the Ischia offshore and the Volturno Basin. While in correspondence to the Sorrento Peninsula and the Volturno river a good reflectivity of the seismic signal has been observed, on the contrary, the central sectors of the profile, where the Magnaghi canyon and the Ischia volcanic complex occur, are characterized by a poor reflectivity of the seismic signal, due to the occurrence of levels of volcanites and buried seismic units. An area of poor penetration of the seismic signal, related to the occurrence of Meso- Cenozoic carbonates (MC unit) has been recognized at the south-eastern corner of the seismic line. This area represents the offshore prolongation of the Capri structural high. In the corresponding emerged sector, Meso-Cenozoic carbonate rocks, related to the western margin of the Campania-Lucania carbonate platform extensively crops out (D’Argenio et al. , 1973; Barattolo and Pugliese, 1987). Two seismic units have been identified in the Capri structural high, unconformably overlying Meso-Cenozoic carbonates. They are interpreted as two relict prograding wedges. The oldest prograding wedge (A seismic unit), probably Early-Middle Pleistocene in age, is characterized by continuous and strongly inclined reflectors, truncated close to the sea bottom by an erosional unconformity. The youngest prograding wedge (C seismic unit) is characterized by continuous seismic reflectors, probably dating back to the Late Pleistocene. Along the continental slope it is incised by the Dohrn canyon branches. The continental slope between the Magnaghi canyon and the structural high of the Ischia volcanic complex shows an acoustically transparent seismic facies, genetically related to the volcanites and to the volcaniclastites of the Ischia volcanic complex (Isch seismic unit). The southern Procida offshore is characterized by volcanic deposits, lacking of internal reflectivity and deeply incised by the Magnaghi canyon. A volcanic edifice, mounded-shaped, corresponds to a buried volcanic edifice, previously unknown and interstratified with the volcanites of the Mg unit under the canyon itself. The Volturno Basin is characterized by four main seismic units. The lithologies of the seismic units have been qualitatively calibrated using the lithostratigraphic data of the Castelvolturno 2 exploration well (Ippolito et al. , 1973) and the onshore seismic section of Mariani and Prato (1988). The oldest unit of the basin fill (D1 unit) is characterized by parallel and continuous seismic reflectors, interpreted as Pleistocene coastal shales alternating with volcaniclastic sediments. The D1 unit overlies the Ff seismic unit showing discontinuous chaotic reflectors and correlating with Miocene flysch deposits, composed of alternating sands and shales and widely cropping out in Central Apennines (“Flysch di Frosinone” Auct.; Parotto and Praturlon, 1975). The overlying seismic unit (D2 seismic unit) is characterized by moderate amplitudes and marked reflectors with high lateral continuity. It has been interpreted as Pleistocene and marine deltaic sediments. This geological interpretation has been supported by the lithostratigraphic data of the Castelvolturno 2 deep borehole and by the onshore seismic sections in the Volturno plain (Mariani and Prato, 1988). The onshore sections suggest the occurrence of a seismic unit composed of discontinuous reflectors with high amplitude and sigmoidal pattern, composed of alternating sands and shales, Pleistocene in age. This unit is genetically related to the D2 unit in the Volturno Basin. In the Volturno Plain lithostratigraphic well data show a thick sequence (about 1000 m) of Pleistocene alternating deltaic sands and shales, interlayered with pyroclastites and lavas. The D3 seismic unit shows parallel to sub-parallel seismic reflectors having a high amplitude. It is formed by alternating sands and shales of deltaic environments, Pleistocene in age, similar to the onshore section (Mariani and Prato, 1988). The main regional morpho-structures of the Ischia-Capri alignment of the Campania continental margin are here discussed based on seismic interpretation. The Banco di Fuori is a morpho-structural high of the Meso-Cenozoic carbonate substratum, bounding the southern sector of the Naples Bay. Its flanks and top are overlain by the Pleistocene deposits of the Late Quaternary depositional sequence. Acoustically transparent seismic facies, genetically related