Francesco Massari

This study investigates the detrital record of the early orogenic evolution of the Sardinia‐Calabria system, preserved in Upper Cretaceous arenites exposed in eastern Sardinia. Sardinia and Corsica form a continental block that includes a segment of the Alpine orogen and of its former foreland basin. We investigate Upper Cretaceous arkosic turbidites from the Lanaittu Valley in eastern Sardinia. Biostratigraphy constrains the depositional age of the arenites to the middle‐late Campanian. Petrographic analyses confirmed the presence of rare glaucophane‐crossite combined with up to 13% kyanite and trace amounts of lawsonite. Using U‐Pb and (U‐Th)/He methods, double‐dated detrital zircons reveal a significant population (22%) that records mid‐to‐Late Cretaceous exhumation‐related cooling. Older zircon U‐Pb date populations, with a dominant Middle Permian peak and Proterozoic components, indicate a cratonic provenance consistent with the Sardinia/Calabria basement. A multi‐source area within an active orogenic belt is envisaged, supplying detritus to a basin located on the thinned Sardinian crust. These data indicate an episode of eo‐Alpine high‐pressure metamorphism and exhumation, likely related to the subduction of the Western Ligurian Ocean beneath a portion of the Alkapeca microplate, which is identified with the northern Calabria‐Peloritani subterrane. This metamorphic event is comparable to eo‐Alpine events recorded elsewhere in the Mediterranean region, such as in the Sesia zone of the Western Alps. Exhumation is inferred to have occurred during ongoing convergence, marking an early stage of Alpine subduction.

Aimed at integrating knowledge of the Mesozoic succession of eastern Sardinia, two sections of Cenomanian and Santonian ages are presented, and their lithostratigraphical, palaeontological, and biostratigraphical features are described in detail. The former section (Lanaittu, Oliena territory), is composed of upper Cenomanian pelagic limestones unconformably lying on Hauterivian shelf limestones through a fossiliferous conglomeratic hardground of middle Cenomanian age; the latter section (Orosei area), consists of Santonian chalk with basal encrinite that unconformably lies on a conglomeratic hardground of late Albian age, in turn erosively resting on a folded substratum of Lower Cretaceous limestones. The mid-Cretaceous and Santonian unconformities present in both sections and in other Cretaceous successions of Sardinia are significant for reconstructing the palaeotectonic history of the island within the geological evolution of the Tethyan domain. The mid-Cretaceous event is interpreted to be related to the SE-directed subduction of the W Ligurian Ocean, which was triggered by the sinistral motion of Iberia with respect to Europe. The Santonian event is attributed to the change to more orthogonal convergence, accompanied by the onset of forebulge development in Sardinia.