The Il Torno collapsed basin-margin tract and rockfall deposits. The stunning snapshot of a preserved Jurassic submarine topography in the Longobucco Basin (Calabria, Italy)

The stratigraphic succession of the Longobucco Basin, exposed along the northeastern slopes of the Sila Mountains in northern Calabria, documents the evolution of a portion of the European/Iberian continental margin of the Tethys which is today part of the so-called Calabria-Peloritani Terrane. This is in contrast with the neighbouring Apennines and Maghrebides chains, which represent the deformed Africa/ Adria passive continental margin of the Tethys (Haccard et al. 1972; Bouillin 1984; Passeri et al. 2014; Santantonio et al. 2016). The present-day position of Calabria is the result of its southeastward drift from its original position attached to the Sardinia–Corsica Block, due to opening of the Tyrrhenian Sea back-arc basin (Carminati et al. 2012). One peculiar geological aspect of the Longobucco Basin is the occurrence of uncommon sedimentary facies, a product of the unusual juxtaposition of typical Tethyan carbonate and siliceous marine facies and the Paleozoic crystalline and metamorphic basement, which resulted in widespread carbonate/ siliciclastic mixing. Paleozoic crystalline rocks were exposed at the seafloor due to footwall unroofing, produced by Sinemurian to Toarcian synsedimentary extension. This generated a complex submarine topography, resulting in stratigraphic successions dominated by multiple unconformities and spectacular lateral thickness and facies changes. Along the basin-margins, preserved tracts of Jurassic submarine escarpments are spectacularly exposed, allowing to observe an intriguing set of associated paleomorphological, sedimentological, paleobiological, diagenetic, and structural features.