GNGTS 2013 SES S IONE 3.3 MaRINE GEOLOGICAL MappING OF THE CaMpaNIA REGION at THE 1:10,000 SCALE: THE EXAMPLE OF THE GEOLOGICAL Map N. 465 “ISOLA DI PROCIDA” (NapLES BaY, SOUTHERN TYRRHENIAN SEA, ItaLY) G.Aiello Institute of Marine Environmental and Coastal Area (IAMC), National Research Council of Italy (CNR), Naples, Italy Introduction. Marine geological mapping of the Campania Region at the 1:10.000 scale is herein presented, focussing, in particular, on the geological map n. 465 “Isola di Procida” (Ispra, 2011). The geological map n. 465 “Isola di Procida” covers the Naples Bay from the Sorrento Peninsula up to the Procida island. In this geological map a total amount of 622 km2 of surface about 10 km2 are represented by emerged areas and 612 km2 by marine areas. The bathymetric belt 0/200 extends for 378 km2 and represents about the 60.8% of the total surface of the map. Sidescan sonar data have been calibrated by numerous sea bottom samples. The geological structures overlying the outcrop of acoustic basement, both carbonate (in correspondence to the Sorrento Peninsula) and volcanic (in correspondence to the Phlegrean Fields) have been investigated using Subbottom Chirp, Sparker and Watergun profiles. The interpretation of seismic data lends support for the reconstruction of the stratigraphic and structural setting of Quaternary continental shelf and slope successions and correlation to outcrops of acoustic basement, Mesozoic carbonate in the Sorrento Peninsula structural high and Quaternary volcanic in the Phlegrean Fields and Procida island. These areas result from the seaward prolongation of the stratigraphic and structural units widely cropping out in the surrounding emerged sector of the Sorrento Peninsula (Cinque et al., 1997), Naples town, Phlegrean Fields and Procida island (Scarpati et al., 1993; Perrotta et al., 2010; Ispra, 2011). Source data and methods of cartographic representation. Several geological and geophysical surveys on the continental shelf and slope of the Naples Bay have been carried out, particularly referring on the geological map n. 465 “Isola di Procida”. In particular, a high resolution Multibeam bathymetry of the Naples Bay allowed for the construction of a marine DEM (Digital Elevation Model) of the area, giving a detailed image of the morpho-structures at the sea bottom (D’Argenio et al., 2004). Moreover, Sidescan Sonar acoustic profiles covering the whole Naples Bay have been acquired for the construction of photomosaics of the sea bottom. The Sidescan Sonar photomosaics and the Multibeam bathymetry represented the base for the marine geological mapping. The integrated geological interpretation of seismic, bathymetric and Sidescan Sonar data has been tied by sea bottom samples and piston cores. The geological structures and the seismic sequences, both volcanic and sedimentary in nature, which characterize the Naples Bay at a regional scale have been the object of detailed studies carried out using multichannel and single channel seismics of various resolution and penetration, including the Sub-bottom Chirp profiles, often integrated with marine magnetics (Aiello et al., 2001; Secomandi et al., 2003; Aiello et al., 2004, 2005; D’Argenio et al., 2004; Ruggieri et al., 2007). The interpretation of high resolution seismic reflection profiles (Sub-bottom Chirp, Sparker and Watergun) has supported the reconstruction of stratigraphic and structural framework of the continental shelf and slope successions. The seismo-stratigraphic analysis allowed distinguishing the main volcanic and sedimentary seismic units, separated by regional unconformities, tectonically and eustatically controlled. The Dohrn and Magnaghi canyons, eroding the slope up to 1000 m of water depth, represent in the Naples Bay important morpho- structural lineaments, at the boundary between the sedimentary units of the eastern shelf of the Naples Bay and the volcanic units of the western shelf, in correspondence to the Ischia and Procida islands. The complex stratigraphic architecture of the Naples Bay has revealed, during the Late Quaternary, a strong control of the volcano-tectonic processes in triggering submarine gravity instabilities. This regional geological framework did not allow a simple application of principles 175 131218 - OGS.Atti.32_vol.3.27.indd 175 04/11/13 10.39 GNGTS 2013 SEssIONE 3.3 and techniques of seismic and sequence stratigraphy, as described in the guidelines for the redaction of marine geologic cartography (Catalano et al., 1996; Fabbri et al., 2002). Laterally coeval depositional systems, representing portions of system tracts of Late Quaternary depositional sequence have been recognized and their possible mapping has been taken into account for the cartographic representation. The seismic units have been later interpreted in terms of depositional sequences and corresponding unconformities have been interpreted as Type 1 or Type 2 sequence boundaries and/or as local unconformities, mainly at the top of relic volcanic edifices or at the top of volcanic seismic units (D’Argenio et al., 2004; Aiello et al., 2005; Ruggieri et al., 2007). The marine geological maps, realized based on the above mentioned criteria shows the distribution of several lithostratigraphic units cropping out at the sea bottom and of the main morphological lineaments, based on the CARG guidelines for the realization of marine cartography (Catalano et al., 1996; Fabbri et al., 2002). The main stratigraphic units individuated through the analysis of sea bottom sediments belong to the Late Quaternary Depositional Sequence; in this sequence, it is possible to recognize the space and time evolution and the lateral and vertical migration of marine coastal, continental shelf and slope depositional environments in the Late Pleistocene-Holocene glacio- eustatic cycle. The stratigraphic succession studied by geological survey has recorded the variations of the accommodation space of the Late Quaternary deposits during the last 4th order glacio-eustatic cycle, ranging between 128 ky B.P. (Tyrrhenian stage) and the present (isotopic stage 5e). One aim of the cartography has been the cartographic representation of the lithofacies associations, whose grouping form the depositional elements (which are portions of system tracts), in relation to the morpho-structural lineaments recognized through the geological interpretation of the geophysical data and the dynamics of depositional environments. In this way, we tried to realize an integration between classical stratigraphic approach, sequence stratigraphic approach and characterization of actual and recent depositional elements. The volcanic activity, which has mainly controlled the stratigraphic architecture of the Naples Bay prevented a classical stratigraphic approach in the marine geological mapping, which has been realized taking into account both the associations of depositional systems and the interstratified volcanic bodies (volcanites and volcanoclastites). Moreover, this stratigraphic approach allowed obtaining information comparable with other sectors of the Italian continental margins. The last Quaternary sea level rise, having an excursion of about 120 m and a maximum rate in the order of 10 m/1000 years has left a stratigraphic signature on the morphologic and stratigraphic framework of most continental margins of the world (Chappell and Shackleton, 1986). The deposits associated to this process are strongly different in the various areas, as a function of different sediment supply, morphological framework and oceanographic regimes; to map these deposits allows to correlate the unconformities (erosional and non-depositional) and to compare the facies, the internal geometries and the thickness of the deposits recording the sea level rise in a differential way on the several margins. The key to the geological maps. The key to the geological map n. 465 “Procida” includes the description of the geologic and morphologic elements. The areal geological elements are represented by two superimposed levels: the textural classes distinguished following the classification of Folk (1954), graphically distinguished with halftone screens; the depositional elements, distinguished with the full colour. The superimposition of the environmental information on the textural one allows for a more complete reading of the cartography, furnishing at the same time geological and environmental information. The morphological elements, both areal and linear represent another level of graphic superimposition to the geological information. 176 131218 - OGS.Atti.32_vol.3.27.indd 176 04/11/13 10.39 GNGTS 2013 SES S IONE 3.3 Marine geological units. Several volcanic units of substrate have been distinguished, cropping out between the Procida islands, the promontories of Monte di Procida and Capo Miseno and the coastal cliffs off Nisida and Posillipo (Naples town), of a carbonate unit of substrate, cropping out in the Sorrento Peninsula off Massalubrense and of undifferentiated carbonate and volcanic substrates, distinguished in the offshore area based on geophysics. The Late Quaternary marine geological units are herein described as it follows (Ispra, 2011). The littoral environment is characterized by different types of deposits, which characterize the high relief coasts and the low relief coasts. The toe of cliff deposits, representative of high relief coasts, represent the terms of passage among the sediments of the volcanic units representing the submerged cliffs and the sands and gravels of inner shelf,