The Sardinia-Corsica microplate and its role in the Northern Apennine Geodynamics: new insights from the Tertiary intraplate strike-slip tectonics of Sardinia

Giacomo Oggiano(*), Antonio Funedda(**), Luigi Carmignani(***) & Sandro Pasci(*)
(*) Istituto Policattedra di Scienze Geologico-Mineralogiche, Università di Sassari, C.so Angioy, 10 - 07100 Sassari. (**) Dipartimento di Scienze della Terra, Università di Cagliari, Via Trentino, 51 - 09127 Cagliari. (***) Dipartimento di Scienze della Terra, Università di Siena, Via Laterina, 8 - 53100 Siena; e Centro di GeoTecnologie, Università di Siena, Via dei Vetri Vecchi, 34 - 52027 San Giovanni Valdarno (AR). Corresponding author: tel. +390706757767; fax: +39070282236. Email: afunedda@unica.it

The behaviour of Sardinia and Corsica within the Alpine-Apennine orogenic events has not been considered in a univocal way; different hypotheses have been proposed, disregarding any eventual effect on the internal structuration of this piece of European crust. Identifying the mechanism and age of the prominent strike-slip tectonics in Sardinia and Corsica allows us to bear new insights on the relationships between the south European crust and Adria plate. Syntectonic Oligocene-Aquitanian deposits fill some intracratonic basins in Sardinia. They developed in correspondence with releasing bends that affect the sinistral strike-slip faults, constraining the time span during which this tectonic regime was active. Thrusts and folds involving the Mesozoic and Lower Cainozoic cover are not ubiquitous in Sardinia, they are mainly localised along deformed corridors in the NE part of the Island where deeply shortened Cainozoic conglomerates were involved in the wrench-thrust faults which, in some case, led the basement to override the Mesozoic cover. The association of these structures to restraining bends is documented, so that they are the coeval transpressive counterparts of the strike-slip basins. Confining most of the Tertiary strike-slip tectonics of Sardinia and Southern Corsica within an Oligocene-Aquitanian time interval involves the following consequences: i) no E-W extension, leading to a N-S trending rift (in present-day coordinates), was active in Sardinia and Corsica during Oligocene-Aquitanian times; ii) the so-called Sardinia Rift is an assemblage of shallow asymmetric basins, trending N150, which developed during the late Burdigalian-Langhian, i.e. contemporary to the onset of the collapse of the North Apennine and Alpine Corsica orogenic wedge and to the opening of the North Tyrrhenian Sea; iii) the Oligocene-Aquitanian strike-slip tectonics in Sardinia is consistent with the deformation of a hinterland involved in collision; this was the collision between Adria and Europe that led to the building of the North Apennines; iv) the collisional event predates the drifting of the Sardinia-Corsica crust and the opening of the Liguro-Provencal basin.

Sardinia, North Apennine, strike-slip tectonics, Oligocene-Aquitanian, Central-western Mediterranean.