Late Santonian bioevents in the Schattau section, Gosau Group of Austria – implications for the Santonian–Campanian boundary stratigraphy

The Schattau section in the Gosau Group (Northern Calcareous Alps) records a late Santonian interval in the northwestern Tethys. The crinoid Marsupites laevigatus, which indicates the lower part of the latest Santonian Marsupites zone, has been found within a Micraster bed in the Bibereck Formation. Co-occurring ammonites, such as Boehmoceras arculus and Placenticeras maherndli, indicate a late Santonian age. The upper Santonian zonal markers Placenticeras paraplanum and Cordiceramus muelleri muelleri, which occur below the Micraster bed, in the Sandkalkbank Member (Hochmoos Formation), indicate the upper Santonian paraplanum Zone. Within the Micraster bed, the planktonic foraminifera Globotruncanita cf. elevata and Globotruncanita stuartiformis have their first (local) appearance. Dicarinella asymetrica is still present up to the top of the section, indicating the asymetrica–elevata Concurrent Range Zone. Nannofossils give evidence for the CC17 and UC12-13 standard zones. Strontium and carbon isotope data, albeit interpreted with caution, allow some further correlations of the section. This indicates that Globotruncanita elevata and Globotruncanita stuartiformis have their first occurrences in the late Santonian. The first occurrence of the nannofossil Broinsonia parca parca, which defines the base of the CC18/UC14 standard zones, was found in neighbouring sections and is an early Campanian event.