Dynamics of deep structures in the Tyrrhenian - Apennines area and its relation to neotectonics

Abstract

New data on the origin and dynamics of deep structures in the Apennines are presented and their possible effect on neotectonics is discussed. The crustal underplating of a thick (5÷20 km) "layer" of heavy magmatic melts beneath the western Apennines is shown as the most striking process that has occurred from Tortonian times to Present. It is the effect of hot plumes rising up from the deep mantle, the origin and evolution of the basin-chain system is assumed to be the consequence of the migration of such plumes. Magma types and their space-time evolution are suggestive of the plumes dynamics and of the related Tyrrhenian Sea spreading and chain formation. The various structural units of the Apennines would have moved from their original position in the Tyrrhenian area at the roof of the subcrustal magmatic accumulation along well-defined routes formed by deep-rooted transcurrent faults transverse to the Apennines main axis. DSS profiles corroborate this hypothesis. The tectonic blocks between transcurrent faults will possibly undergo a marked differential uplift both before and during the transcurrent slippage, and elongated basins may form due to the differential crustal dragging occurring above the underplated melt.