Author	Schioler, P. and Wilson, G.J.
Year	1993
Journal	Review of Palaeobotany and Palynology, 78 (1993): 321-351
Title	Maastrichtian dinoflagellate zonation in the Dan Field, Danish North Sea

Abstract Schioler, P. and Wilson, G.J., 1993; Maastrichtian dinoflagellate zonation in the Dan Field, Danish North Sea. Review of Palaeobotany and Palynology, 78 (1993): 321-351 ABSTRACT: Core samples from the Maastrichtian oil reservoir chalks in the Dan Field (southern part of the Danish Central Trough) have yielded diverse dinoflagellate cyst assemblages which have been assessed in order to establish a high-resolution biostratigraphic framework. Eight successive downhole events occur in a relatively consistent pattern and have been used to subdivide the Late Maastrichtian and the late Early Maastrichtian in the Dan Field. The events are: (I) (Cretaceous/Tertiary boundary) Last occurrence datum (LOD) of several taxa: Palynodinium grallator, Spiniferites ramosus cavispinosus, "Chytroeisphaeridia everricula" and "Northidinium perforatum". (2) First appearance datum (FAD) of P. grallator. (3) FAD of Hystrichostrogylon borisii. (4) LOD of Isabelidinium cooksoniae. (5) The almost simultaneous FAD of Deflandrea galeata and LOD of Triblastula utinensis. (6) LOD of Alterbidinium acutulum. (7) LOD of Eatonicysta hapala sp. nov. (8) FAD of T. utinensis. Four new zones and three new subzones are established below the Palynodinium grallator Zone: Hystrichostrogylon borisii Zone; Palaeocystodinium denticulatum Zone; Isabelidinium cooksoniae Zone; Triblastula utinensis Zone; Cannosphaeropsis utinensis Subzone; Alterbidinium acutulum Subzone; Eatonicysta hapala Subzone. A new stratigraphically important dinoflagellate species, Eatonicysta hapala sp. nov., is formally described. The new subdivision of the oil reservoir chalks has added to the understanding of the extent of the thin high-porosity layers, which are important for oil production from the field.