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Eocene siliceous and calcareous phytoplankton, with emphasis on silicoflagellates, were studied in 62 samples from DSDP Sites 612 and 613 on the continental slope and rise off New Jersey. The mid-latitude assemblages correlate well with assemblages from California, Peru, and offshore of southern Brazil, but are distinctly different from high-latitude cold-water assemblages of the Falkland Plateau off southern Argentina. Coccoliths and silicoflagellates provide evidence for the presence of a fairly complete middle and upper Eocene sequence, represented by a composite of Sites 612 and 613. A major unconformity occurs at the middle Eocene to upper Eocene contact at Site 612. The genus Bachmannocena Locker is emended and proposed as a replacement for genus Mesocena Ehrenberg for ring silicoflagellates. Six new silicoflagellates and one new diatom are described: Bachmannocena apiculata monolineata Bukry, n. subsp., Corbisema amicula Bukry, n. sp., C. bimucronata elegans Bukry, n. subsp., C. hastata incohata Bukry, n. subsp., C. jerseyensis Bukry, n. sp., Dictyocha acuta Bukry, n. sp., and Coscinodiscus eomonoculus Bukry, n. sp. Also, one new replacement name, B. paulschulzn Bukry, nom. nov., and 24 new combinations are proposed for genus Bachmannocena. INTRODUCTION Coring on Leg 95, off the coast of New Jersey, recovered a thick section of Eocene biosilica-rich sediment. Silicoflagellates from 62 samples taken from a 160-mthick section at DSDP Site 612 and a 120-m-thick section at DSDP Site 613 were studied for biostratigraphy, paleobiogeography, and taxonomy. Coccolith stratigraphy at these sites provides a check on silicoflagellate zonal correlation with the recently described Eocene sections in California (Barron et al., 1984), the Rio Grande Rise (Bukry, 1977), and the Falkland Plateau (Shaw and Ciesielski, 1983). The extensive biosilica-rich stratigraphic sections of Sites 612 and 613 cover the major parts of the middle and upper Eocene in a mid-latitude setting. Lower Eocene strata lack siliceous phytoplankton. The main goals of this study were to identify the similarity and contrasts between the Leg 95 assemblages and assemblages of other areas (Fig. 1). Owing to the diverse assemblages, biostratigraphic correlation by key warmand temperate-water species ranges {Bachmannocena apiculata apiculata, Dictyocha hexacantha, D. spinosa, Macrora najaé) was straightforward. Relative paleotemperature correlation through the Corbisema/Naviculopsis ratio was less satisfactory, as it appeared that strong dissolution (Site 613) might differentially remove more Corbisema than Naviculopsis. Taxonomically, use of the genus Bachmannocena Locker is instituted for ring silicoflagellates previously referred to Mesocena, and several other new taxa from the Leg 95 assemblages are described. The main taxonomic highlight is the close reiteration of form and composition bePoag, C. W., Watts, A. B., et al., Init. Repts. DSDP, 95: Washington (U.S. Govt. Printing Office). 2 Address: U.S. Minerals Management Service (A-015), Scripps Institution of Oceanography, La Jolla, CA 92093. tween the assemblages of Leg 95 and those in California and on the Rio Grande Rise. The coeval assemblages of the Falkland Plateau represent a different cold-water province where the relative abundance of N. foliacea (warm) is small compared with that of N. constricta (cool). METHODS AND MATERIALS Acid-residue slides (silicoflagellates) and whole-sediment smear slides (coccoliths) were prepared for 62 samples from Cores 16 to 37 from Site 612 and Cores 21 to 38 from Site 613. Light-microscope study and counts were done at magnifications from 200 × to 500 × . Silicoflagellate abundance was variable, and up to three slides per sample were used to obtain counts for some sparse samples. To meet time constraints, counts of 100 specimens per sample were used as the general goal to establish quantitative trends. Fragmented silicoflagellates were mentally accumulated until they could be tallied as whole specimens. Tilted, obscured, and taxonomically ambiguous specimens were tallied as indeterminate spp. to provide fair generic numbers. Coccolith determinations were made from light-microscope smear slides of original sediment for the same samples used for silicoflagellates. Assemblages were studied at magnifications of 500 × to 1000 × . Coccolith zonation is based on the low-latitude zonation developed for DSDP core material (Bukry, 1973b, 1975a; Okada and Bukry, 1980). Silicoflagellates are also zoned and correlated according to the stratigraphic relations synthesized for low-latitude DSDP cores (Bukry, 1981a) and expanded for the Kellogg Shale of California (Barron et al., 1984). SUMMARIES OF PHYTOPLANKTON OBSERVATIONS AT LEG 95 SITES 612 AND 613 Site 612 (38°49.21'N, 72°46.43'W; water depth 1404 m) Site 612 was drilled on the New Jersey Continental Slope to provide a relatively uninterrupted section for a stratigraphic framework. The hemipelagic sediment of the middle and upper Eocene is especially rich in biosilica. Silicoflagellates are generally common to abundant through Cores 612-17 to 612-33. The associated coccoliths are abundant and diverse, with primary guide fossils, such as Chiasmolithus gigas, C. grandis, Discoaster

Eocene Siliceous and Calcareous Phytoplankton, Deep Sea Drilling Project Leg 95