Miocene-Pliocene tectonic phases and migration of foredeep-thrust belt system in Northern Apennines.

In this paper a space-time evolution of the Northern Apennines during the Miocene-Lower Pliocene is proposed, following the migration of the foredeep-thrust belt system towards the foreland. Every tectonic phase is marked by the thrusting of an inner unit over an outer one and by the overriding of Ligurides on Tertiary units at the level of closure facies. The peak of tectonic activity is preceded by a period of instability marked by the deposition of submarine slides and of minor turbiditic bodies showing Alpine and Apennine sources supplied by both Ligurian and flysch nappes. During each tectonic phase, except the Tortonian and Early Messinian phases, an outward foredeep migration took place. The emplacement of Ligurian units, driven by horizontal compression, occurred by imbricate slices involving closure pelites via the formation of piggyback basins. A complex duplex formed, laterally bordered by transverse lines, which, in their turn, affected closure facies during thrust advancement.