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Faculty of Applied Sciences, Bath College of Higher Education, Newton Park, Newton St Loe, Bath BA2 9BN, UK
The Plio-Pleistocene radiolarian record of the North Atlantic differs considerably from that of the Pacific and Indian Oceans. The standard cosmopolitan low-latitude radiolarian zonal scheme can be applied to the tropical Atlantic, but a separate zonation has been developed for the endemic radiolarian faunas of the high latitude North Atlantic. A new (preliminary) radiolarian zonation for the Plio-Pleistocene is offered here for middle latitudes, consisting of five zones defined on Last Appearance Datum levels only: Cycladophora davisiana zone (0–0.5 Ma), Stylatractus universus zone (0.5–1.75 Ma), Antarctissa whitei zone (1.75–3 Ma), Sphaeropyle langii zone (3–4.75 Ma) and the Stichocorys peregrina zone (4.75 Ma to Late Miocene). This new zonation, being geographically transitional, contains elements of both the previous high- and low-latitude zonations.
Radiolaria also possess great potential for palaeoceanographical analysis in the North Atlantic. The recognition of subarctic, boreal, subtropical and tropical radiolarian assemblages may prove useful in tracking water masses at times of climatic and oceanographic change. Radiolarian species characteristic of Indo-Pacific upwelling areas, e.g. Pterocanium auritum Nigrini & Caulet, Lamprocyrtis nigriniae (Caulet), Acrosphaera murrayana (Haeckel), Pterocorys minythorax (Nigrini) and Lithostrobus hexagonalis Haeckel, have been found in the eastern tropical North Atlantic (ODP Hole 658C), and it may be possible, through future research, to develop an Upwelling Radiolarian Index for the Atlantic. This would be capable of documenting upwelling histories and help to interpret ocean-atmosphere interaction in the eastern tropical Atlantic during Plio-Pleistocene time.
