From Mesozoic rifting to Apennine orogeny: The Gran Sasso range (Italy)

The Apennines are a low-temperature accretionary prism generated by the west-directed subduction of the Adriatic-Ionian plate, whose structural origin is still to be fully understood. The highest and best-exposed segment of the Apennines, the Gran Sasso range is here documented to unravel the tectonic history of the northern tip of Gondwana. It is located along a NE-verging salient of thrust sheets decoupling the sedimentary cover of the subducting Adriatic lithosphere. Field mapping and structural analysis along the E-W trending left-lateral transpressive segment of the salient highlight the interplay of the inherited Mesozoic passive margin stratigraphic and tectonic framework with the Neogene contraction. The rheological differences between the massive carbonate platform and the well-bedded turbiditic and pelagic limestones determined along-strike undulations of the thrusts geometries and fold styles during shortening. Heterogeneities are due to inherited syn- and post-rift Mesozoic tectonics. The Gran Sasso overturned anticline shows a backlimb anomalously tilted toward the foreland and we infer this dip as being related to a deeper back-thrust of a triangle zone. The pinching out of the foredeep sequence on the growth anticline forelimb dates the contractional phases of the region to the late Messinian. From the late Pliocene to Present, the area has been uplifted and extended about 2. km by oblique normal faults cross-cutting the accretionary prism. Some of them are seismically active, as shown by the 2009 Mw 6.3 L'Aquila earthquake.