GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.2 163 of a foreland tilting during the Messinian, eventually connected to the Apennine migration or to the compressional/transtensional tectonic on the Dinaric external chain. Generally, the MSC thinning can be related to the evidence or not of erosional truncation: i) Without erosion evidence: there are not evidences of MSC thinning (that means lower depositional rate) above the Apennine thrust. In some cases, the layer is thicker above or in a side (Fig. 3) of the structural highs, so testifying that its uplift developed after the MSC, during the Plio-Quaternary. Furthermore, we can observe that the MSC layer becomes thinner toward the deeper part of the interpreted foredeep: this also suggests that it originated later, that means during the Plio-Quaternary. All these observations suggest that the Apennine Chain had not reached the current Central Adriatic Sea in the Messinian. ii) With erosion evidence: erosional truncation is sometimes evident on the top of the structural highs, in particular the positive structures of the Mid-Adriatic Ridge. Geletti et al. (2008) interpreted this structure as due to halokinetic tectonics from the Burano Formation, originated in pre-MSC time and currently active. Other times the erosion is evident on the structural lows, generally due to canyon related turbidites that are partially driven by the pre-existing bathymetry. Interpretation of the seismic profiles was also focalized on the analysis of the Bolognano Formation and Marne a Fucoidi , both of them underlying the MSC marker. The Eocene/Miocene Bolognano Formation has been calibrated by 3 of the analyzed boreholes where it is characterized by open-ramp carbonate deposits. In the Italian onshore it is physically imaged by a characteristic and fairly continuous couple of strong reflectors (Patacca and Scandone, 2011). A number of 24 boreholes cross the Marne a Fucoidi Formation of Aptian/Albian age. It consists essentially of varicolored alternations of marl and marly clays, sometimes blackish, bituminous (anoxic episodes) and subordinately by limestone, marly limestone and clays. Its Fig. 2 - The NW-SE profile, approximately parallel to the Italian shoreline, is sited in coincidence with the B-443 seismic line (position in Fig.1) depicting the depth of the Messianian Top (pink line). Different depths of the Messinian are related to deformation of the Adria foreland and to the presence of the Mid-Adriatic Ridge. Moreover, two zoom of the Messinian seismic facies shows the characteristic of the gypsum deposits.