Oligocene dinoflagellate cyst biostratigraphy of the southern North Sea Basin

The Rupelian (Lower Oligocene) and Chattian (Upper Oligocene) stratotype sections are both defined on the basis of the southern North Sea Basin sedimentary successions. The characterisation of biotic events occurring within the stratotypes (and equivalents) is vital for the recognition of these stages outside the North Sea Basin. Although the restricted marine setting of the North Sea Basin during most of the Paleogene clearly hampers 'traditional' calcareous microfossil calibration, organic-walled dinoflagellate cysts (dinocysts) are increasingly successful in the stratigraphic analysis and calibration of the marginal-marine North Sea Basin successions. Here we present a high-resolution Oligocene dinocyst biostratigraphic zonation scheme for the southern North Sea Basin based on previously published and new dinocyst studies from Belgium, northern Germany and The Netherlands. Eight (southern) North Sea Oligocene (NSO) dinocyst zones (biozones) and four subzones are here defined. Their application on a regional and inter-regional scale is discussed. The stratigraphic important Late Oligocene dinocyst taxon Triphragmadinium demaniae gen. and sp. nov. is formally described.