A stratigraphic and tectonic review of the Italian Southern Alpine Permian

The South-Alpine Permian succession consists of continental and also, to the east of the Adige Valley, marine deposits. The former are made up of volcanic and siliciclastic rocks, while the latter, represented by the Bellerophon Formation of Late Permian age, include evaporites and shallow-marine sediments. However, in the Carnic Alps, marine deposition began earlier, from Carboniferous times. In this context, two major and well-differentiated tectono-stratigraphic units (TSUs) or cycles, separated by a marked regional unconformity and a gap of as-yet uncertain duration, are clearly evident. This paper aims at reviewing the current stratigraphic framework and correlating it to the most recent timescales. This research indicates that initial deposition of the Verrucano Lombardo/Val Gardena Sandstone red beds probably occurred in many places, such as in the Carnic Alps, during Middle Permian times. Consequently, this interpretation supports a reduction, at least locally, of the large time-gap suggested between the two above-mentioned cycles. Their respective evolution led to paleogeographic changes related to different structural and geodynamic settings. The Lower Permian stratigraphic sequencewas mainly deposited in transtensional pull-apart and strike-slip intracontinental basins during the onset of regional uplift, with unroofing, collapse and stretching of the Variscan orogen, upwelling of the asthenosphere and intrusion of granitic melts into the crust. This episode could be interpreted as the final act of the “Hercynian (Variscan) Cycle”. It was followed by a tectonic event (the so-called “Mid-Permian Episode” in the literature) as a prelude to general plate reorganization and the opening of new oceans (such as Meliata-Maliak and Neotethys). In contrast, the Middle pro parte—Upper Permian stratigraphic sequence marks the development of more generalized extensional tectonics, compatible with a rifting regime. According to many authors, it is regarded as the beginning of the “Alpine Cycle”.