Exhumed eo-Alpine High-Pressure Rocks Fed Campanian Turbidites in Eastern Sardinia

Abstract

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.