PALINSPASTIC RESTORATION AND PALEOGEOGRAPHIC RECONSTRUCTION OF THE PERI-TYRRHENIAN AREA DURING THE NEOGENE

This paper presents the results of research carried out on the paleogeographic and geodynamic post-collisional evolution of the peri-Tyrrhenian area from the Southern Alps to Sicily. During this post-collisional evolution a back arc area-thrust belt-foredeep system developed, in which the following tectono-sedimentary zones can be distinguished, from the external to the internal ones: the foreland zone, connected to the foredeep through a slope generally controlled by normal faults; the foredeep, an assymmetric depression with strong subsidence, related to the compressional activity of the thrust zone; the chain, whose outward migration from the late Oligocene onward was discontinuus, with important stages of crisis partially connected to the mechanical response of different crustal thicknesses existing in the foreland; the discontinuous satellite basins, developed within the thrust belt; the back arc basins, developed in the inner part of the chain, where the superposition of the extensional tectonics over previous compressional domains causes the fragmentation of the thrust belt, leading to its destruction. According to this model, seven palinspatic maps are discussed, regarding the following time intervals: late Oligocene (25-24 m.y.), Burdigalian (22-20 m.y.), Langhian (17-16 m.y.), Serravallin (15-13 m.y.), Tortonian (10-9 m.y.), late Messinian (5.5-5.3 m.y.) and early Pliocene (5.3-4.6 m.y.). During five of these time intervals significant geodynamic modifications occurred in the whole peri-Tyrrhenian area, leading to paleogeographic changes. In any case the geodynamic evolution of the whole area seems clearly controlled by the activity of important bundles of tectonic lines transversal to the chain which, in the same time interval, in the outermost part of the thrust belt separated areas with different values of shortening, and in tthe most internal zones separated segments having different amount of extension. These tectonic lines certainly have a crustal significance and have probably acted along previous formed discontinuities. © 1990.