GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 3.2 531 The Licosa morpho-structural high (Southern Campania continental margin, Tyrrhenian sea): geomorphologic hints of lowstand episodes based on high resolution seismic data G. Aiello CNR IAMC, Sede di Napoli, Naples, Italy Some geomorphologic evidence of the occurrence of lowstand episodes in the Licosa morpho-structural high, located on the southern Tyrrhenian continental margin off Campania has been found based on a densely-spaced grid of high resolution seismic reflection profiles (Subbottom Chirp) and is herein presented. This evidence is represented by terraced surfaces located at several water depths, incised in the rocky acoustic basement, widely cropping out in the seaward prolongation of the Licosa morpho-structural high. The geological structures and the related seismic sequences, unconformably overlying wide outcrops of the acoustic basement, have been studied and interpreted in detail. This has allowed to analyze the stratigraphic architecture of Quaternary marine deposits. These deposits have been detected in the depocentral areas located between the mouth of the Solofrone river and the town of Agropoli. In the Licosa morpho-structural high the rocky outcrops result from the seaward prolongation of the stratigraphic-structural units, widely cropping out onshore in the adjacent emerged sector of the Cilento Promontory (“Flysch del Cilento” Auct. : Ciampo et al. , 1984; Bonardi et al. , 1988). The Cilento Promontory represents a morpho-structural high, interposed between the coastal depressions of the Sele Plain-Salerno Gulf and of the Policastro Gulf. Its reliefs are composed of thick successions of turbidite siliciclastic and carbonatic sequences, dipping landwards into the main carbonatic reliefs of the Southern Apennines (“Alburno-Cervati” Unit). The terrains cropping out in the Cilento Promontory are formed by siliciclastic rocks, accumulated into deep basins during a time interval ranging from the Late Mesozoic to the Late Miocene. The oldest one of these formations is the North Calabrian Unit, the highest stratigraphic-structural unit in this sector of the Southern Apenninic chain. In the Cilento area it is represented by a formation ranging in age from the Malm to the Oligocene, composed of dark clays, marls and marly limestones, reaching a thickness of 1300 meters. The North Calabria unit is overlain by Early Miocene synorogenic units, showing a degree of deformation higher with respect to that one of the overlying tectonic units. The Cilento Flysch includes the Pollica, S. Mauro and Monte Sacro Formations, showing an overall thickness of about 1500 m (Bonardi et al. , 1988). In the western sector of the Cilento Promontory several morphological depressions filled by alluvial deposits, whose origin has been attributed to NNE-SSW (Plain of Alento) and NW- SE (Plains of S. Maria di Castellabate and S. Marco) trending structural elements, occur. The formation of these depressions has to be attributed to the Late-Middle Pleistocene (Brancaccio et al. , 1995). They include transgressive-regressive cycles referred to the glacio-eustatic oscillations of the isotopic stage 9, 7 and 5 (Shackleton and Opdyke, 1973), downthrown of several tens of meters with respect to their original altitude, between the end of the Middle Pleistocene and the beginning of the Late Pleistocene. The Cilento Promontory has been involved by a vertical uplift of more than 400 m during the Early Pleistocene and the Middle Pleistocene. Absolute estimates of the entity of the Pleistocene uplift which involved the Cilento Promontory have been obtained through the vertical distribution of the Pleistocene marine terraces along the Cilento coasts. In the Northern Cilento the oldest marine terraces (Middle Pleistocene) are located at a maximum altitude of 350 m a.s.l. (Cinque et al. , 1994). At the Bulgheria Mt (southern Cilento), the marine terraces of the Late Pliocene-Early Pleistocene are uplifted to heights of 450 m a.s.l. On the other side, the terraces of the Emilian are uplifted to heights of 350 m a.s.l. (Baggioni et al. , 1981; Lippmann- Provansal, 1987; Borrelli et al. , 1988). The morphological elements of the coastal areas relative to palaeo-stands of the sea level