GNGTS 2014 - Atti del 33° Convegno Nazionale

of the valley flanks has been reconstructed based on core data. The basal fluvial deposits are separated by the Early Holocene transgressive facies by a suite of estuarine deposits. These are separated from overlying transgressive barrier sands by a ravinement surface. Upwards, a distinctive shallowing upward succession of Middle-Late Holocene age is interpreted to reflect the beginning and the consequent progradation of a wave-dominated delta system, produced as a response to a reduced rate of sea level rise. A detailed tephrochronological study has been carried out in three deep sea cores drilled in the Tyrrhenian and Ionian seas (Paterne et al. , 2008). The age and the origin of the marine tephra were inferred from oxygen isotope records of foraminifera and frommajor element composition of glass fragments. Seventy-one eruptions have been detected during the time interval spanning from 90 to 200 ky B.P., during which the volcanoes of the Roman-Campanian comagmatic region were in activity. This evidence is confirmed by the geochemical compositions of marine and terrestrial deposits. The study tephra layers consist of trachytes and phonolites: several of them have been purposed as marker horizons for proximal and distal sediments (Paterne et al. , 2008). Eight tephra markers have been purposed within marine isotope stage 5 from MIS5.2 (87 ky B.P.) to sapropel S5 [122 ky B.P.; Paterne et al. (2008)]. Sixteen ash layers of trachytic composition have been purposed to be stratigraphic markers between the sapropel S5 and the MIS 6.6 (183 ky B.P.). In the Tyrrhenian sea five tephra layers, trachytic in composition, have been recognized between the MIS 6.6 and the MIS 7.2 [205 ky B.P.; Paterne et al. (2008)]. In addition, other five tephra layers have been distinguished due to their chemical composition and stratigraphic location. The tephrochronological analysis of three deep sea sediment cores collected in the Tyrrhenian sea and in the Ionian sea extends a stratigraphic record of the volcanic history of the southern Italy volcanology up to 200 ky B.P. The marine tephra layers are well representative of the volcanic activity of the central (Campanian and Roman provinces) and southern Italy (Aeolian and Pantelleria islands, Etna Mount), in agreement with the dating of the terrestrial proximal deposits (Paterne et al. , 2008). In the deep sea sediments the ash layers have mainly a trachytic and phonolitic composition, since they originate both the Campanian and Roman provinces. Moreover, the marine tephra layers originating from the Pantelleria island are better represented than those from the Aeolian islands. The activity of the Pantelleria island is well represented in the cores drilled in the northern Tyrrhenian sea. The marine tephrochronological study has pointed out that frequent explosive events occurred in Italy over the past 200 ky B.P., enhancing the important role of the tephra layers as chronological marker horizons. A sketch diagram of the stratigraphic relationships between the seismic units and the unconformities offshore Cuma (northern Campania) based on the geological interpretation of Subbottom Chirp profiles has been constructed. In this scheme three main seismic units have been indicated (A, B and C) in both continental shelf and slope domains. A detailed geologic interpretation has allowed to distinguish the sub-units in the continental shelf, coeval to seismic units pertaining to slope depositional environment. The A unit, i.e. the most recent one, is composed of two sub-units in the shelf (A1 sub-unit and A2 sub-unit) coeval with the AC unit on the continental slope. The A1 and A2 sub-units are bounded below by the R2 unconformity, while the AC unit is bounded below by the S2 unconformity. The B unit is composed of two sub-units in the continental shelf (B2 sub-unit and B1 sub-unit), separated among them by the R2a unconformity. The B2 and B1 sub-units are bounded at their base by the R1a unconformity, while the BC unit is bounded at its base by the S1a unconformity. Finally, the C unit, i.e. the oldest one, is composed by the C2 and C1 sub-units, separated by the R1 unconformity. These units, pertaining to the shelf, are coeval with two different sub-units on the continental slope, namely the Cc2 and Cc1 sub-units, separated by the S1 unconformity. GNGTS 2014 S essione 3.3 213