Extensional regime in the Northern Apennines: indications from the lithospheric behaviour

The aim of this work is to assess the conditions leading to extension during the tectonic evolution of the Northern Apennine chain, starting from the reconstruction of the rheological behaviour of the lithosphere underneath the chain. The temperature field and the strength of the lithosphere during the evolution of the belt in different sectors of the Northern Apennines, are calculated. A model, which assumes that the heat is transported by conduction and advection, is used to mimic a thermal perturbation migrating from west to east. The thermal regime is influenced by simultaneous crustal thickening in the easternmost sector and by advection due to extensional processes in the western sector of the chain. Rheological profiles and the strength of the lithosphere for different sectors of the chain at different times are obtained and compared with the difference in potential energy connected to the stress induced by compensated topography. The results show that, for homogeneous crustal thickening, the advection term moving form west to east would increase the tensile deviatoric stress in the area where the transition between the advection and thickening processes is located: in this area the strength is reduced in such a way as to trigger extension.