A New perspective on the depositional environment of the Montefino succession (Abruzzo Pliocene foredeep, central Italy)

The Montefino succession (MoS) consists of a lower Pliocene 300 m-thick stack of sandstones with minor pelitic intercalations, mappable over tens of km between the Vomano and Tavo valleys, in north-eastern Abruzzo. Since it was first described, the MoS was defined as a turbiditic channel-lobe transition deposit, usually considered as the top of the Cellino Formation. The ongoing field mapping carried out in the context of the CARG Project (350 - Penne Sheet), provides new evidence not relatable to the above interpretation. Particularly, the lenticular geometry of some arenaceous beds of the MoS, showing clear pinch-out closures, the occurrence of intervals with heterolithic bedding and the diffuse bioturbation traces referable to skolithos association, indicate littoral/paralic facies in the frame of a siliciclastic continental shelf. All these observations, together with the recognition of an unconformity in the pelites just below the lowermost sandstone beds, suggest that the studied succession should be separated from the underlying Cellino Fm, whose facies are clearly referred to a deep foredeep basin. We propose to define the Montefino Fm as a new informal unit ascribing its depositional environment to a deltaic system. If confirmed by further biostratigraphic and petrostratigraphic analyses, this hypothesis could open new tectono-stratigraphic constrains concerning the position of the leading edge of the Apennine compressional front, at the time of MoS deposition.