Biostratigraphy of the lower red shale interval in the Rhenodanubian Flysch Zone of Austria Michael Wagreich a, * , Polina Pavlishina b , Ewa Malata c a Department of Geological Sciences, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria b Department of Geology and Palaeontology, Sofia University, 15 Tzar Osvoboditel Bd., 1000 Sofia, Bulgaria c Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, Krako ´w, Poland Received 6 January 2005; accepted in revised form 16 January 2006 Available online 30 June 2006 Abstract In the Rhenodanubian Flysch Zone of Austria, between the AptianeAlbian ‘‘Gault Flysch’’ and the CenomanianeTuronian Reiselsberg Formation, an interval with predominant red shales (‘‘Untere Bunte Schiefer’’) occurs. In the Oberaschau section near Attersee (Upper Austria) a ca. 18-m-thick interval of alternating red and grey shales and marlstones with minor sandstones is present. Thin sandstone intercalations are interpreted as distal turbidites. Dinoflagellate cyst assemblages indicate the Litosphaeridium siphoniphorum Zone. The concurrent presence of Litosphaeridium siphoniphorum and Ovoidinium verrucosum in all samples allows a correlation to the lower part of this zone, thus defining a Late AlbianeEarly Cenomanian age. Based on foraminifera, the red beds can be assigned to the topmost Rotalipora appenninica Zone and the Rotalipora globotruncanoides Zone due to the presence of small morphotypes of the index taxa. Nannofossils indicate standard zones CC9/UC0 throughout the red interval, defined by the first occurrence of Eiffellithus turriseiffelii, and UC1 above the red shales. Based on these multistratigraphic data, a latest AlbianeEarly Cenomanian age can be inferred. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Rhenodanubian Flysch Zone; Albian; Cenomanian; Dinoflagellates; Foraminifera; Nannofossils 1. Introduction The Rhenodanubian Flysch Zone (RFZ) of the Eastern Alps of Austria and Bavaria comprises several tectonic units of mainly deep-water turbidite and hemipelagic successions, deposited below the calcite compensation depth (CCD) as part of the Alpine flysch belt (Fig. 1). Three distinct intervals of var- iegated red shales or marlstones occur in the Cretaceous RFZ of Austria (e.g., Egger, 1992; see Fig. 2), in the AlbianeCenoma- nian (‘‘Untere Bunte Schiefer’’: Prey, 1950), the Coniacian/ Santonian (Seisenburg Formation), and the Late Campanian (Perneck Formation). These shales comprise mainly carbon- ate-free red clays with rare intercalations of sandstones. As these red sediments indicate oxic intervals in this part of the Tethys, their stratigraphy and relationship to Cretaceous anoxia is cur- rently under discussion (e.g., Hu et al., 2005). The facies of the red shales in the RFZ displays significant similarities to other Cretaceous Oceanic Red Beds (CORBs; Hu et al., 2005). Distinctive, red hemipelagic-pelagic intervals within otherwise turbidite-dominated successions of the RFZ have been interpreted primarily as the result of low sedimentation rates in a deep, silici- clastic flysch basin below the local CCD (Egger, 1993). This paper presents the results of our investigations of one of a few sections containing the lowermost red interval of the RFZ in Upper Austria. Multistratigraphic methods, including the use of dinoflagellates, foraminifera and calcareous nanno- fossils, have been applied to specify more precisely the chro- nostratigraphic age and significance of this interval. This gives a new basis for a better correlation with known occur- rences of mid-Cretaceous CORBs in other parts of the Tethys (e.g., Hu et al., 2003). * Corresponding author. E-mail address: michael.wagreich@univie.ac.at (M. Wagreich). 0195-6671/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2006.01.002 Cretaceous Research 27 (2006) 743e753 www.elsevier.com/locate/CretRes