GNGTS 2013 - Atti del 32° Convegno Nazionale

associations are localized in the Ischia Channel in proximity to the lower boundary of the grasses at Posidonia Oceanica . The distal inner shelf and the outer shelf are characterized by sandy pelites and shales, pyroclastic in nature, which characterize the depositional areas of the inner shelf. These deposits represent the passage seawards and occur on flat sea bottoms and characterize areas linked to processes of decantation. Above the 30 m of water depth the continental shelf is characterized by the occurrence of bioclastic deposits, which grade laterally to lithoclastic gravels. The bioclastic deposits are represented by heterometric gravels, gravel sands and bioclastic gravels, which grade laterally to the coarse-grained lithoclastic deposits. The bioclastic deposits are composed of heterometric gravels, gravelly sands and bioclastic sands in a scarce or absent pelitic matrix. They represent the typical maerl facies (Peres and Picard, 1964), where are mainly abundant fragments of Gastropods, Echinoderms, Bryozoans, Serpulids, benthic foraminifers and Corals (Cladocora coespitosa). These bioclastic deposits are often localized in the surroundings of the Posidonia oceanica mattes and in the inter-mattes areas (Corricella and Punta dei Monaci, Procida). Marine geomorphology. The Procida and Vivara islands, together with the Ischia Island (Phlegrean islands) bound westwards the Naples Bay. They represent volcanic morpho- structural highs uplifted on the continental shelf, constituting the insular portion of the Phlegrean Fields (Figs. 1 and 2). Wide sectors of continental shelf and slope occur in the Naples Bay, characterized by an articulated morphology for the occurrence of relict volcanic edifices (Aiello et al. , 2004, 2005), more than the Dohrn and Magnaghi canyons, representing pathways for sediment transport towards the continental slope (D’Argenio et al. , 2004; Ruggieri et al. , 2007; Di Fiore et al. , 2011). Geological structures due to recent fragile deformation occur, sometimes responsible for the tectonic dislocation of the above mentioned elements. The continental portion of the Phlegrean Fields is bounded seawards by the Monte di Procida and the Posillipo promontories (Naples town), among which the Pozzuoli bay occur. The Phlegrean islands are interposed among sectors of continental shelf having different morpho-structures, Fig. 1 – Sketch map showing the framework of the geological maps carried out in the Campania region by the CNR-IAMC Institute. Shaded relief bathymetry up to the 200 m isobaths has also been reported. 178 GNGTS 2013 S essione 3.3