New data and hypothesis on the development of the Tyrrhenian basin

Abstract

Among those basins which developed during the Neogene and Quaternary at the rear of the perimenditerranean mountain chains, the Tyrrhenian basin is the most recently formed. Comparing the available geological and geophysical data, the Tyrrhenian domain and its neighbourhoods can be divided into more or less homogeneous sectors: namely Northern and Southern Tyrrhenian, Apenninic chain, Maghrebides chain, Apulian and Iblean-African foreland, Ionian foreland. For each sector the different phenomena involved and the crustal characteristics are discussed. The evolution of the domain has been explained by the application of a crustal stretching model developed for continental margins. This approach predicts the formation of basinal areas as a result of the Europe/Africa collisional movements within a plastic-rigid deformation model. Taking into account the mass redistribution after collision, the model explains both the distension developed within the collisional system and the penecontemporaneous development of compressive and distensive phases. As a consequence of the intraplate stresses, horizontal shearings affecting the whole lithosphere at different levels, occur, with delaminations, asthenosphere uprising and gradual collapse in the upper crust. E-W trending and strike-slip dextral faults played a primary role in the evolution of the Tyrrhenian basin inducing the largest tearings at the end of the major transcurrent systems. Such an evolution is complicated by the migrating motion of the shear zone from N to S and by the penecontemporaneous stop in the extension from the northern towards the southern domains. Of outstanding importance is the shear zone which borders the Southern Tyrrhenian enabling the opening of the basin and allowing the development of the major group of en-echelon sub-basins with a NW-SE trend.