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A Neogene radiolarian zonation using deep-living radiolarians has been developed. This zonation consists of 6 radiolarian zones with the nominant taxa of each zone first occurring at the base of its zone, and that nominant taxa running throughout its zone. These zones are the Eucyrtidium cienkowskii (22.5-19 Ma), Siphocampe arachnea (19-14 Ma), Oroscena with digitate spines (14-11 Ma), Botryostrobus bramlettei (11-6 Ma), Clathrocyclas bicornis (6-2.5 Ma), and Cycladophora davisiana davisiana (2.5-0 Ma) Zones. These zones were developed by using Antarctic, equatorial, and North Pacific Deep Sea Drilling Project holes, and are believed to be cosmopolitan zones due to their being based on deep-living radiolarians. These zones are dated by correlating the first occurrences of the nominant taxa with warm-water radiolarian datums that have been paleomagnetically dated. These zones are not designed for routine use, but rather for tying together other more provincial zonations, and for comparing oceanographic phenomena on global datum planes. To date, this zonation has been used to correlate Antarctic zonations intra- and inter-regionally and to study the evolution of radiolarian lineages.
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