Plio-Quaternary sequences and tectonic events in the northern Adriatic Sea (northern Italy)

Abstract

The analysis of multichannel seismic profiles and their correlation with well data in the northern Adriatic Sea (Northern Italy) has allowed to document Plio-Quaternary episodes of tectonic subsidence and uplift. They affected the sedimentation above the Mesozoic to lower Eocene Friuli-Dinaric Carbonate Platform (FDCP) and the unit composed of the Eocene Trieste Flysch and the Miocene Molassa (TFM), as well as the sedimentary succession lying SW of the FDCP. In particular, the early Zanclean reflooding that postdated the Messinian Salinity Crisis, was followed by the SW-ward progradation of a highstand to forced regressive shelf-slope system (Sequence 1). Forced regression was controlled by a main episode of tectonic uplift that occurred at the end of the Zanclean. This tectonic event also led to the formation of the sequence boundary separating the two main sequences that compose the Plio-Quaternary succession. The lower part of Sequence 2 (Piacenzian to late Pleistocene) recorded a two-step subsidence phase, which led to drowning episodes during Piacenzian and in particular late Gelasian (transgressive systems tract of Sequence 2). They were associated with the partial flooding of the TFM and the Miocene deposits overlying the FDPC, and with a downward bending of the pre-Calabrian succession toward the Apennine chain. The accommodation created during the late Gelasian drowning event was filled in part by an Alpine-sourced, SW-ward prograding system, and in part by the NE-ward paleo-Po prograding system (highstand systems tract of Sequence 2). The most recent part of Sequence 2 documents the last glacio-eustatic cycles in a physiographic context characterized by a very low gradient.