Application of a mechanical model to the Northern Apennines, with special reference to the effect of sea level changes

Abstract

The mechanics and geometry of thin-skinned tectonic wedges are a function of the parameters top and basal slope, strength of wedge and basal layer, pore-fluid pressure and sea level. An analysis of a mechanical model, that takes these parameters into account, shows that alternating submarine and subaerial conditions can have important consequences for the stability of such a wedge. The model is applied to the Northern Apennines. It can explain multiple phases of gravitational sliding in the Ligurian scaly clay melanges. The contrasting style of deformation of different tectonic units, and temporary suppression of synsedimentary thrusting in the Romagnan sequences can also be explained by this model. It is shown that gravity spreading, induced by brittle-ductile transition, provides a mechanism which can explain the metamorphic gap at the tectonic boundary between the doubled Tuscan sequences in the Alpi Apuane, as well as the simultaneous spreading at the rear and the shortening at the front of the Northern Apennine foldbelt.