Two sedimentary cycles were recognized in the Mesozoic successions of the Northern Apennines: a Middle Triassic and an "Alpine" post-Ladinian cycle. The first is related to the evolution of the northern branch of the Tethys, the second is related to the opening of the central Atlantic and to the further evolution of its Liguria-Piedmont branch. The Middle Triassic Cycle is documented in the La Spezia zone with transgressive conglomerates, followed by carbonates and by regressive deltaic to continental quartzarenites. The beginning of the "Alpine cycle" is documented by different successions in different areas. In the La Spezia zone, quartzarenites and stromatolitic carbonates (Carnian in age) are followed by basinal facies (limestones and marls from Norian to Sinemurian). In the Aquane zone, Norian-Rhaetian and Hettangian carbonate platforms developed on the Hercynian basement. In the Tuscany-Umbria Marche zone, coastal to shallow marine quarzarenites (Carnian in age) are followed by Norian evaporites. Climatic changes during the Rhaetian caused the end of the evaporitic sedimentation. At the beginning of the Jurassic, a carbonate platform (Calcare Massiccio) spread over the whole area. This platform began to drown at the end of the Hettangian, but some shallow water carbonate banks survived until the Carixian.