ASPECTS OF CALCIFICATION IN PLANKTONIC FORAMINIFERA (SARCODINA)*

Climatic modelling in the Cretaceous using the distribution of planktonic Foraminiferida

During the Cretaceous, planktonic Foraminiferida underwent a major diversification, colonizing a wider range of water depths and geographical regions. Orville Bandy, over 30 years ago, was the first to recognize the potential of using this regional distribution to reconstruct different palaeoceanographic regimes. Using new data from the South Atlantic Ocean, Antarctic Ocean and the Indian Ocean it is possible to show the poleward migration of warm-water taxa during the Cretaceous and compare it with data already available from the Northern Hemisphere. Instead of the present-day nine latitudinal zones based on planktonic taxa it is only possible to identify five with any degree of reliability. These are from north to south, the Boreal, Transition, Tropical (= Tethyan), Transition and Austral. In some of the developing oceans during the Cretaceous (e.g. the Eastern Indian Ocean, South Atlantic Ocean) there are local biogeoprovinces with quite distinctive local assemblages and morphotypes. While these do not reflect on the climatic zonation they provide an interesting insight into the development of the plankton. The foraminiferal distributions are compared with climatic maps produced by the assessment of other data sources.