Neogene Radiolarians in Neogene sediments of the Norwegian Sea

Radiolaria are present in frequencies ranging from rare to abundant and with generally moderate to good preservation quality in Leg 104 sediments younger than 22 Ma. Preservation degrades in progressively younger sediments, and upper Pliocene to mid-Pleistocene radiolaria were found only at Site 644, where sporadic assemblages of moderate to poorly preserved specimens persist to approximately 0.75 Ma. Radiolaria are essentially absent in Leg 104 recovery older than basal Miocene. The stratigraphic ranges of 55 taxa of radiolaria are documented in 451 samples from the biosiliceous recoveries of Holes 642B, 642C, 642D, 643A, and 644A. The stratigraphic ranges of 25 of these species are used as boundary criteria for a new system of 28 Neogene zones and subzones that are used to characterize approximately 72% of the past 22 m.y. of sedimentation on the Vriring Plateau. This new scheme is intended to supercede the NRS zones provisionally proposed in the Leg 104 Initial Reports. The applicability of this regional biozonation beyond the Wring and Iceland Plateaus is not presently known. The radiolaria biostratigraphy serves as a basis for inferring a sequence of hiatuses and faunal overturns that may be associated with sea-level low stands and consequent cold-water isolation of the Norwegian Sea. Twenty-one new taxa are described as follows: Actinomma henningsmoeni, Actinomma livae, Actinomma mirabile, Actinomma plasticum, Ceratocyrtis broeggeri, Ceratocyrtis manumi, Ceratocyrtis stoermeri, Clathrospyris vogti, Corythospyris hispida, Corythospyris jubata sverdrupi, Corythospyris reuschi, Crytocapsella ampullacea, Cyrocapsella kladaros, Gondwanaria japonica kiaeri, Hexalonche esmarki, Larcospira bulbosa, Phormospyris thespios, Pseudodicytophimus amundseni, Spongotrochus vitabilis, Spongurus cauleti, and Tessarastrum thiedei.