In the Southern Alps a number of 3rd order depositional sequences have been observed, far more than previously known: of these 6 develop principally in the Scythian, 4 in the Anisian, 3 in the Ladinian, 4 in the Carnian, at least 2 in the Norian and finally 2 in the Rhaetian. Lower Anisian to Lower Carnian depositional sequences are best dated by ammonoids, while in the Scythian ammonoids and conodonts are scanty. In the Upper Carnian, Norian and Rhaetian of the Southern Alps very rare ammonoids and conodonts are available. Therefore Scythian, Upper Carnian, Norian and Rhaetian depositional sequences have throughout been defined on the basis of stratal patterns and the evolution of facies, being their chronostratigraphical position inferred from sections elsewhere in the world. The contemporaneous analysis of platforms and basins, and of carbonate, mixed and siliciclastic deposits, has made a good comprehension of facies migration possible. This approach was crucial in the definition of 3rd order depositional sequences. Moreover, on the basis of the previously defined 3rd order sequences and systems tracts, a number of 2nd order transgressive-regressive cycles have been pointed out. The sequence stratigraphic analysis compared with the tectonic history allowed the definition of the different phases of the basin evolution
