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A quantative study was made of silicoflagellates recovered from Sites 642 (lower Miocene-upper Pliocene), 643 (lower Miocene-upper Miocene), and 644 (upper Pliocene-Quaternary) on the Vdring Plateau. Although disconformities are present in these sequences, they represent a much more complete record of the Neogene than was recovered pre viously in the Norwegian Sea by DSDP Leg 38.Silicoflagellates are rare or absent for glacial sequences younger than 2.65 Ma, and generally sparse and poorly pre served in the lower upper Pliocene and upper Miocene. Lower and middle Miocene assemblages are diverse and gener ally well preserved. Temporal changes in the silicoflagellate assemblage are indicative of major paleoceanographic changes in the Norwegian Sea. A regional zonation for the Neogene of the Norwegian Sea is proposed, consisting of eleven zones: Naviculopsis lata Zone, N. quadrata Zone (emended), N. ponticula Zone (emended), Distephanus specu lum hemisphaericus Zone (new), Caryocha ernestinae Zone (new), Bachmannocena circulus var. apiculata/Caryocha Zone (new), Distephanus crux scutulatus Zone (new), Bachmannocena diodon nodosa Zone (new), Distephanus boliviensis Zone (new), Ds. jimlingii Zone (elevated from subzonal to zonal status) with Subzones a and b (new), and Ds. speculum Zone (new). The ranges and abundances of over 100 species and morphotypes are tabulated. INTRODUCTIONThe ODP Leg 104 drilling program was intended to examine the nature and origin of the Vdring marginal high and the Cenozoic paleoenvironment of the Norwegian-Greenland Sea, with eight holes drilled at three sites (Sites 642, 643, and 644; Fig. 1) along a short transect roughly perpendicular to the Vriring Pla teau margin (Eldholm, Thiede, Taylor, et al., 1987). Our major emphasis here is on the silicoflagellate biostratigraphy of the Neogene sedimentary sequences recovered by Leg 104. In a sep arate contribution Ciesielski and Case (this volume) present a paleoenvironmental interpretation of the silicoflagellate assem blages described herein.ODP Leg 104 drilled the first sedimentary sequences in the Norwegian Sea since the initial drilling in the region by Deep Sea Drilling Project Leg 38. Seventeen sites were drilled in the Norwegian-Greenland Sea by Leg 38; however, they were discontinuously rotary-cored, providing a sporadic record of the middle Eocene to Quaternary (Talwani, Udintsev, et al., 1976). In contrast, the three sites drilled by Leg 104 on the Wring Pla teau were continuously cored using nondisturbance coring tech niques (Advanced Piston Corer (APC) and Extended Core Bar rel Corer (XCB), providing the first undisturbed continuous sedimentary sequences from the Norwegian Sea.The silicoflagellate-bearing sedimentary sequences recovered by Leg 104 include the lowermost Miocene to upper Pliocene. Silicoflagellates were extremely rare or absent from the Eocene and Oligocene of Site 643 and from the uppermost Pliocene and Quaternary at all three sites. A quantitative study of these sili coflagellate-bearing sequences is the ...