Contribution to the stratigraphy of the Oligocene-Miocene foredeep successions of the Emilia-Tuscany Northern Apennines, Italy

The Oligocene-Miocene turbidite successions of the Emilia-Tuscany Apennines represent one of the most intriguing topic of the Northern Apennines (NA), due to the complex relationships between tectonics and sedimentation in a migrating thrust wedge - foredeep system, to the not-well constrained differences between orogenic landslides (olistostrome) vs. tectonic chaotic complexes, to the significance of the associated marly deposits, to the emplacement timing and modalities of synsedimentary thrust sheets. In order to achieve some key points to this articulated framework, we have contributed with field-mapping and stratigraphic data on selected marly-turbidite sections of the most critical areas of this sector of NA, which are: Mt. Modino, Civago-Torre degli Amorotti, Gazzano, Gova, Mt. Cimone, Ozola- Ligonchio, Cerreto Pass, Pracchiola, Libro Aperto-Cima Tauffi sections. All these involve some of the most known and not well constrained turbidite units of the NA, as the Mt. Modino Sandstones, the Mt. Cervarola Sandstones and the Gova Sandstones, and the associated marly units as Marmoreto and Civago marlstone fms. These last are also massively involved in highly deformed stacks within chaoticized tectonic units and slices, particularly in the Sestola-Vidiciatico Unit. Our contribute on these sections regard a review of the geological and geometrical field-relationships with particular focus on biostratigraphic new data concerning nannofossil associations, allowing to redefine their age model. All this accompanied by a check for the compositional-petrographic data of the sandstone lithologies, has allowed to insert each section in a coherent basin-chain setting, obtaining an evolutionary model of the chain-foredeep of the NA during the late Oligoceneearly Miocene. The main conclusive remark is the consolidation of the eastward migrating depositional system model, where the foredeep basin, split in several minor sub-basins, due to the pulsating thrusts of the advancing orogenic wedge was structured through two main stages. A first stage during the Chattian-Aquitanian with the development of partially different inner turbidite systems (Mt. Modino Sandstones in a frontal thrust-top basin, Macigno, Torre degli Amorotti System of the Mt. Cervarola Sandstones, Gova Sandstones, etc.) and a second stage developing the wide Mt. Cervarola Sandstone Complex. The two stages result to be separated by the tectonic Tuscan Phase with a deformative acme during the earliest Burdigalian, leading to the development of the Sestola-Vidiciatico Unit and the following involvement of all the sequences in the unit stack.