Middle Triassic (Muschelkalk) transgression in the West Tethys: biostratigraphic evidence from Sardinia (Italy)

Abstract

Stratigraphic and palaeontological analyses of the Middle Triassic (latest Anisian–Ladinian) in Muschelkalk facies are performed here to further unravel the palaeogeographic evolution of Sardinia in this time-frame. These shallow marine successions reveal a significant palaeontological record comprising facies and marker fossils (ammonoids, bivalves, conodonts, foraminifera etc.) reflecting a regional transgressive episode recorded throughout the West Mediterranean, after the Permian–Triassic biotic crisis. Particularly rich in the Nurra and Sarcidano-Gerrei areas, the facies/fossil record indicates the progressive westward settling of carbonate platforms, and consequently the development of new migration and irradiation routes for Sephardic faunas from the southeast (Palaeotethys) and Alpine faunas (Neotethys) from the northeast. Based on new findings and the revision of palaeontological associations previously reported, comparisons were made with associations of adjacent domains (Balearic Islands, Levantine area), thus refining their palaeoecological distribution and better framing Sardinia as a key area in the palaeogeographic evolution of the West Tethys during the Ladinian.