The Triassic Buntsandstein sedimentary basins of Sardinia (Italy) and their transition to the Brianzonese ridge (Western Alps): crossroads through the Western Tethys areas

Abstract

Sardinia represented a key area during the Western Tethys opening in late Early-early Middle Triassic times since it was located at the nodal point of several paleogeographic domains. New and revised sedimentological data and petrographical investigations evidence that the Sardinian Buntsandstein Group formational units differ from each other and were deposited in different alluvial to transitional depositional systems related to Alpine rifting basins. Petrographic analysis revealed directional NS and EW compositional differences: they hint at morphotectonic rises separating the diverse depositional areas through lasting barriers related to paleoeuropean ridges in progressive dismantling. The data suggest that 1) the dominating environmental and (micro)climate conditions were diverse from area to area, 2) the sedimentary basins evolved differently through time, and 3) were diachronous in timing. Moreover, the sources of debris were variable, both in morphology and substrate composition, with reliefs from articulated to smoothed. A stratigraphic and sedimentological framework for the Sardinian Buntsandstein is suggested. Comparison analysis with close coeval successions of the Western Tethydian area, particularly regarding the Upper Permian? - Lower Middle Triassic deposits of the Brianconnais ridge have been attempted, as well as their palaeogeographic localization, to frame the Sardinian Buntsandstein Group with the coeval units of SW Europe.