Introduction

The aim of this paper is to briefly review the most important events that affected Adria from the Permian - when the movements of the Variscan Orogeny were definitively over - to the onset of the first deformations in the Cretaceous, linked to the convergence that eventually led to the Alpine collision in the Cenozoic. A long list of references will enable interested readers to go more deeply into the subject.

Alpine deformations severely affected most of the margins of Adria. However, in the Southern Alps one segment is better preserved not far from the actual margins of Adria. The original relationships, especially in W-E alignment, allow stratigraphic, facies and paleogeographic reconstructions along a transect more than 300 km long. Therefore, emphasis will be put on the Southern Alps. The sedimentary cover on which the Permian-to-Mesozoic evolution is recorded is usually at least 3–4 km thick, with areas such as in eastern Lombardy where sediment accumulation from the Permian to the mid-Cretaceous may reach 10 km in thickness.

Geological research in the Southern Alps over the past 150 years, given the complexity of the sedimentary covers, has resulted in a large volume of literature, mostly in Italian and German. Only in the last few decades has the use of English spread. I will not enter into the details, but most of them will be described through drawings and pictures.

Southern Italy, from Basilicata to Sicily, preserves patchy fragments of sediments deposited on a seaway that evolved differently during the Permian and the Triassic. Attention will be paid also to this area. The remaining parts of the Apennines will not be considered here.

The concept of Adria is not unanimously agreed, even in the name. "Apulia" or "African Promontory" are often considered as synonyms. The main discussion is whether Adria was really a spur of the African Plate (Barrier and Vrielynck, 2008) or an independent microplate (Stampfli, 2005; Finetti, 2005). I assume in this paper that Adria was driven in its main movements by the movements of Africa because, even if Adria during part of the Mesozoic was a microplate independent from Africa, its behaviour would have been like the present Arabian Plate. There are no doubts that the Red Sea separated Arabia from Africa, but the general motions of Arabia are still the same as those of Africa, driven by the opening of the Atlantic Ocean, due to the small width of the Red Sea and hence the reduced rotation of Arabia.

I do not follow the model of Finetti (2005a) or the oft-repeated model of Stampfli (2005, and ref. therein) for at least two reasons. The anti-clockwise rotation of 40° before Anisian assumed by Finetti (2005) is not confirmed by the Lower Permian palaeomagnetic comparative data from the broadly coeval volcanic rocks from Morocco (Muttoni et al., 2003). Significant rotations also do not occurred after the Carnian, as indicated by data on Lybia and the Southern Alps (Muttoni et al., 2001). Palaeomagnetic data do not resolve minor rotations and therefore it is assumed that the width of the hypothetical oceanic seaway interposed between Adria and Africa was smaller than the resolution possible with that method (i.e., about 5° of rotation), while 40° of rotation should be clearly registered. The postulated final width of the Ionian of about 330 km (Catalano et al., 2001) is also less than the paleolatitude discriminant potential of the palaeomagnetic method. Secondly, the earlier rotation should have produced substantial deformations on the margin of Adria and/or of Europe during the Middle Triassic, which are presently unknown. As a matter of fact, Catalano et al. (2001) hypothesized an opening of the Ionian later, during the Mesozoic. Detailed discussion on his topic is beyond the scope of this paper.