Inversion tectonics and structural inheritance in collision mountain belts: An example from the Alps-Apennine system [Tettonica da inversione ed eredità strutturale nelle catene collisionali: un esempio dal sistema Alpi-Appennino]

The structure of continental lithosphere shows complex variety that is inherited into orogenic belts and influences the localization of contractional structures during mountain building. In the Alps- Apennine system the pre-orogenic template can include arrays of extensional faults. While in some areas of the outer orogenic zones these inherited features may simply reactivate under inversion, more commonly faults show complex, partial reactivation structures. In volumes of distributed strain, pre-orogenic faults may serve to nu- cleate large-scale buckle folds located along, or close to basement- cover interfaces. These different patterns of basement reactivation may reflect spatially-varying strength-depth profiles in continental lithosphere that are themselves inherited from spatially-distinct geo- logical histories. Even when not themselves reactivating, basement faults can control deformation in the overlying sedimentary cover by offsetting otherwise regionally-extensive detachment horizons. The 3D geometry of thrust systems can be strongly compartimentalized by pre-existing cross-faults, such as the oblique lineaments of the Apennines. A comparison between the outer, the intermediate and the inner orogenic zones, with examples from both the Alps and the Apennines, illustrates that the propensity for fault reactivation during mountain building depends on the rheological contrasts between the fault zone and surrounding rocks.