A Foraminiferal Biostratigraphy of the Campanian and Maastrichtian Chalks of the United Kingdom.

Abstract

The foraminiferal fauna from twenty-seven sections of Campanian and Maastrichtian chalk from both the onshore and offshore United Kingdom have been studied. In total, 160 species and subspecies belonging to 54 genera have been recorded and a complete revision of their systematics, with full synonomies and descriptions, has been given. The detailed stratigraphic distribution of these species has been studied, and 65 species and subspecies of prime stratigraphic importance have been recognised and employed in the definition of a tripartite biozonal scheme based on planktonic foraminifera, Bolivinoides lineages and faunal assemblages respectively. This biozonal scheme has been accurately related to local rock units as well as to current macrofossil zonations. Correlation of all sections studied has been achieved by use of the proposed biozonal scheme. Broad similarities have been noted between the British foraminiferal faunas of the Upper Cretaceous and those of wide areas of northern Europe, clearly placing Britain within the Transitional biogeoprovince. Palaeoecological study has indicated that marine conditions with normal salinities prevailed throughout the Campanian and Maastrichtian. Palaeotemperatures appear to have gradually declined throughout this time, with a short-lived warm phase in the latest Maastrichtian. Depths of deposition of the chalk are interpreted as having been between 150 - 250m., though greater depths probably prevailed in the North Sea basins. A transgressive phase is indicated for the Upper Campanian and a regressive phase for the Maastrichtian.