Open Discussions and Concluding Remarks

One of the unresolved questions in the stratigraphy of central Italy is the palaeogeographical distribution of the Triassic facies. In particular, the surface and subsurface Triassic database is not yet sufficient to relate the Triassic bituminous dolostones that crop out in the study area to the same pelagic sedimentary basin or to a different intra-platform trough. Additional facies investigations and palaeogeographical studies must be conducted both in surface (Ernici Mts and La Meta-Mainarde-Matese Mts) and in subsurface domains (well data correlation) to resolve this question.

In the more external areas of the central Apennines, the discussion about the structural setting and the kinematic evolution of the area between the Montagna Grande and the Maiella Mts remains open. More structural-kinematic data as well as time constraints from detailed stratigraphical analysis performed on syn-orogenic terrigenous deposits are needed to resolve these problems.

Due to the northward plunging of the outermost outcropping structures of the central Apennines (La Queglia and Maiella Mts), the knowledge of the stratigraphical-structural setting of these external units is critical to resolve the deep structure of the buried Apennine chain to the east of Montagna dei Fiori thrust.

• In central Italy the Mesozoic stratigraphical setting was characterized by a platform-basin system which developed starting from Late Triassic up to Late Cretaceous time as a consequence of the Neotethyan rifting stage.

• For exploration purposes, the presence of bituminous dolostones in the Vradda (Gran Sasso chain) and in the Filettino (Simbruini Mts.) successions suggests the existence of a potential Upper Triassic source rock in central Italy.

• In the Cretaceous basinal succession of central Italy, two more organic matter-rich horizons (black-shales) deserve emphasis as potential source rocks and important stratigraphic marker horizons (Livello Selli, Aptian and Livello Bonarelli, Cenomanian).

• The central Apennine chain consists of tectonic units derived from the deformation of both Meso-Cenozoic shallow-water limestones and Meso-Cenozoic deeper-water carbonates.

• The geometry of the chain, the diachronism of the eastward migrating foredeep basins in the area, and the different ages of the forethrusts are consistent with a regional foreland propagating model for the central Apennines.

• The biostratigraphical analysis performed on the terrigenous deposits related to the evolution of the central Apennine orogenic system allow for recognition of the tectono-sedimentary events that characterized the building of the central Apennine chain. The recognized events occurred during the late Burdigalian, Serravallian, late Tortonian, early Messinian, latest Messinian-Early Pliocene, and top Early Pliocene.

• The central Apennine chain, developed as a foreland migration of the main thrusts, was subsequently affected by out-of-sequence thrusting. Specifically, out-of-sequence activity of important thrust systems such as the Olevano-Antrodoco-Sibillini Mts and the thrust front of the Gran Sasso chain is superimposed on the former deformation due to the piggyback sequence migration of the Apennine active thrust front.

• Using a shortening value of about 50%, in the central Apennines the average propagation rate of the active front of the chain is about 40 mm/yr.

• The different migration rates recorded by the orogenic systems of the northern (10 mm/yr) and central Apennines (40 mm/yr) suggest the existence of a NNE-SSW lithosphere discontinuity that has allowed an independent kinematic evolution of these two segments of the Apennine chain.