On the mechanism of formation of the tyrrhenian sea

Abstract

We investigated some of the existing hypotheses on the formation of the Tyrrhenian Sea basin, and we found that none of them appears satisfactory. By quantitative considerations we show that proposed mechanisms, such as those based on oceanization or back-arc spreading, cannot explain the origin of this basin. We suggest an alternative mechanism, consisting on the gabbro-eclogite transition, which occurs in the basaltic layer of the continental crust when anomalous mantle contacts the crustal basement. This leads to the formation of eclogite, which tears off the crust, sinks into the astenosphere, and accumulates at its base. As a consequence of the destruction of the basaltic layer the crust is strongly reduced and a deep basin is formed. We also suggest that the processes of crustal thinning and subsidence developed as proposed here at different times in different regions.