The dinocyst record across the Cretaceous/Palaeogene boundary of a bathyal mid-latitude Tethyan setting: Gosau Group, Gams Basin, Austria

A high-resolution palynological study carried out across the Cretaceous/Palaeogene (K/Pg) boundary in two sections (Knappengraben and Gamsbach) of the Gosau Group near Gams (Gams Basin, Northern Calcareous Alps, Austria) has identified over 178 dinoflagellate species and subspecies from 89 rock samples. In most samples, the dinocysts are moderately well to well preserved, but associated with reworked material. Some well-known marker species around the K/Pg boundary, such as Carpatella cornuta, Spongodinium delitiense, Trithyrodinium evittii, Palynodinium grallator, Manumiella druggii, Cordosphaeridium fibrospinosum, Membranilarnacia? tenella, Senoniasphaera inornata, Damassadinium californicum, and Dinogymnium acuminatum have been recorded from the samples studied. In addition to these, Trabeculidinium quinquetrum, Lejeunecysta izerzenensis, Batiacasphaera rifensis, Impagidinium maghribensis and Cyclonophelium compactum represent local markers. A Spongodinium delitiense acme is recorded in both sections above the K/Pg boundary and is interpreted to indicate a transient cooling event of oceanic surface waters. The stratigraphic distribution of the dinocyst species indicates that they were not seriously affected by the mass extinction event at the K/Pg boundary, but their diversity slightly increases above it. The composition of the assemblages, however, changes drastically. Six dinocyst assemblages and four palynofacies assemblages were identified by means of cluster analysis. Their distribution does not show any regular pattern. The increase of phytoclasts in the Danian clearly indicates enhanced terrestrially derived input into the basin. The palynological and sedimentological differences between the two sections can be explained by small scale local lateral variations.