Towards a stable and agreed nomenclature for North Sea Tertiary diatom floras — the ‘ Coscinodiscus ’ problem

Abstract

Abstract Diatoms are one of the most useful microfossil groups to be found in Tertiary (particularly Palaeogene) sequences of the North Sea subsurface for their biostratigraphic utility, especially where other mineralized-walled microfossil groups (e.g. foraminifera, calcareous nannoplankton, etc.) are absent. An example from one offshore borehole (Shell UK; 29/25-1) is given. However, their further use in biostratigraphic and sequence correlation is hampered by the lack of any stable nomenclature applied to their taxonomy. The numbers of so-called ‘in-house’ taxa are legion with duplication of forms almost inevitable. Few of these many and varied taxa are directly comparable between these schemes, and this leads to almost inevitable confusion for exploration, production and development geoscientists trying to correlate between the various schemes. One stratigraphically important and familiar diatom taxon ( Coscinodiscus sp. 1) is formally described in this paper as Fenestrella antiqua (Grunow) Swatman. In the example shown here it is demonstrated that four forms, previously identified as four independent taxa in open nomenclature (with distinctive stratigraphic ranges), are in fact separate manifestations of the life habitat of this one single species. It is hoped that through an awareness of the biological complexity of these forms, and their relationships to morphology, a stable taxonomy will eventually arise. It is furthermore hoped that this will lead to a stimulus in the study of the biostratigraphic and palaeoenvironmental applications of this important microfossil group to exploration, production and development geoscience.