From Permian to Cretaceous: Adria as pivotal between extensions and rotations of Tethys and Atlantic Oceans

Maurizio Gaetani

During the latest Palaeozoic and Mesozoic, most of Italy was connected to the Gondwana assemblage of plates, representing the Adria Spur of Africa. After the Variscan collision and orogeny in the Carboniferous, Adria was situated in a peculiar position for several geodynamic major events. During the Permian, it was situated in the belt affected by the shear movements that led Pangea to its eventual Pangea A configuration. Studies of the volcanics of the Southern Alps give significant support to the palaeomagnetic evidence for these events. From the Late Permian to the Triassic, Adria mostly acted as a passive margin facing east towards the Palaeo-Tethys, even though regional rotations complicated this evolution, because Adria was in the pivotal position for the rotational movements that closed the Palaeo-Tethys and opened the Neo-Tethys. From the Late Triassic to the Jurassic, Adria started to be involved in the propagation of the ongoing rifting of the Central Atlantic Ocean, which eventually opened as a true ocean during Middle-Jurassic, forming the Ligurian-Piedmont Ocean or Alpine Tethys. In the Southern Alps and Apennines, large sections of the passive margin facing this new opening ocean are preserved, as well fragments of the oceanic crust and its sedimentary cover. The rifting and opening of the Southern Atlantic Ocean caused the anticlockwise rotation of Africa, with consequent convergence between Adria and Europe. This rotation led to the progressive closure of the Ligurian-Piedmont Ocean and formed the earliest reliefs of the future Alps.