The Gran Sasso d'Italia thrust system within the axial culmination of the Pliocene-Quaternary Central Apennines Chain [Il sistema a pieghe e sovrascorrimenti del Gran Sasso d'Italia nella culminazione assiale della catena pliocenico-quaternaria centro-appenninica]

The Gran Sasso thrust system forms a spectacular salient struc- ture in the Central Apennines, juxtaposing the Triassic-Miocene car- bonate succession (Gran Sasso unit) on the siliciclastic Miocene deposits belonging to the Laga Unit. In the analysed area, the Gran Sasso thrust front is represented by two main thrust planes, trending approximately E-W, that isolate an intermediate tectonic body, and related N-verging recumbent folds tightening to the east. To the west of the Corno Grande, the above mentioned thrusts progressively lose displacement, assuming the character of blind-thrust and tips at the periclinal termination of the Monte Corvo anticline. The integrated analysis of the geological and structural data allowed us to point out: a) The control of the Adria paleomargin architecture on the salient geometry of the Gran Sasso thrust ramps and related folds; b) The reconstruction of an piggy-back sequence of deformation for the Gran Sasso thrust system development, char- acterised by the Pliocene reactivation of the thrusts and their syn- chronous activity respect to the N-S trending thrusts of the Mon- tagna dei Fiori-Montagnone structure; c) The gradient of thrust shortening with the maximum value in the apex zone of the salient (about 15 km) and the transpressive deformation along E-W and N-S lateral/oblique ramps, in agreement with the pattern of the rotations evidenced by paleomagnetic studies.