NEW DATA ON THE MID- TO UPPER CRETACEOUS SUCCESSION OF EASTERN SARDINIA IN THE FRAMEWORK OF THE GEOLOGICAL EVOLUTION OF THE TETHYAN REALM

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.