Stratigraphic and tectonic evolution of the Pliocene Abruzzi basin (Central Apennines, Italy)

The Abruzzi Pliocene Basin occupies the outer part of the present Central Apennines chain-foredeep-foreland system and records the last deformation phases associated with the migration of the Apenninic orogen. This basin is divided into four main sectors characterized by successions with different stratigraphic evolution in time and modes. From the innermost to the external ones, they are: Villadegna-Cellino Anticline, Atri Basin, Coastal Structure and Adriatic Foreland. Facies stacking pattern, geometric relations and type of processes associated to the formation of unconformities have concurred to subdivide the sedimentary infilling into eight depositional sequences, detectable along the whole basin and recognizable with different features along different sectors. These sequences represent the response of the main evolution stages of the Pliocene Abruzzi Basin, referable to Foreland, Foredeep and Piggy-back stages. The Foreland stage characterizes the area at the base of the Pliocene, forcing phisiographic changes, increasing tectonic subsidence rates and deposition of condensed successions. The Foredeep stage develops diachronously from Lower Pliocene p.p. to Upper Pliocene, moving from internal sectors to the Adriatic Foreland; it is characterized by the maximum development of the depocenter with the highest rates of tectonic subsidence and with the deposition of huge turbiditic successions. The Piggy-back stage involves the internal sectors of the Pliocene Abruzzi basin starting from Lower Pliocene p.p. and develops diachronously in the main depocenter; it is characterized by the decrease of subsidence rates and by the progressive shallowing upward signature of successions. The framework resulting from this research shows the migrating behaviour of major and minor stratigraphic-structural elements; this is realized through the progressive involvement of different sectors in the evolution phases and with different modes controlled by the presence of pre-existing paleogeographic elements and by transversal and longitudinal propagation of thrusts.