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During Deep Sea Drilling Project Leg 93, upper Miocene through Quaternary sediments were continuously cored in Hole 604, located on the upper continental rise of the New Jersey transect (western North Atlantic). A detailed biostratigraphic study of these strata has been made using the vertical distribution of planktonic foraminifers. The Quaternary climatic zonation of Ericson and Wollin (1968) has been tentatively delineated and all the Pliocene zones and subzones (sensu Berggren, 1977) have been recognized. The rate of sedimentation was slow during most of the Pliocene but underwent a significant acceleration in the early Pleistocene. Quantitative variations in the distribution of planktonic foraminifers appear to be influenced by various factors, such as hydrodynamic winnowing resulting from the action of bottom currents and surficial thermal conditions caused by climatic changes. Both dissolution intervals and brief increases in the coarser detrital input seem, most of the time, to be correlated with indications of climatic cooling and may correspond to glacial events or cycles. This chapter delineates a precursor stage in the inception of Northern Hemisphere glaciation at 3 Ma and wide-scale Quaternary glacial-interglacial cycles. Data from a detailed study of Hole 604 are briefly compared with the main sedimentary and microfaunal features of contemporaneous series previously drilled along the east American margin in the northwestern Atlantic. One of the striking observations appears to be the intense redistribution of sediments that affected this region in Neogene-Quaternary times. INTRODUCTION Neogene through Quaternary beds were penetrated in six holes at three sites during DSDP Leg 93. Site 604, the subject of this study, is located on the upper continental rise along the New Jersey transect (Figs. 1,2). Hole 604 was drilled at 38°42.79'N, 72°32.95'W, at a water depth of 2361 m, and penetrated 295 m of Quaternary, Pliocene, and upper Miocene sediments. Thirtyone rotary cores were taken. Hole 604A was offset about 1.2 km northwest, in a more proximal position along the transect, at 38°43.08'N, 72°33.64'W and at a water depth of 2328 m. This second hole was washed to 250 m, then continuously cored to a sub-bottom depth of 285 m, and finally abandoned after a difficult recovery of four upper Miocene cores. Quaternary and Neogene sediments drilled at Site 604 are composed predominantly of gray to dark greenish clays and silts, with glauconite-rich sandy intervals, becoming conglomeratic in the lowest (upper Miocene) part (Fig. 3). In Hole 604, 82 samples were investigated in detail for foraminifers. Eight of these samples appeared to be barren, and a few samples were contaminated by reworking of older (exclusively Eocene and/or Miocene) forms. Microfossiliferous samples yielded planktonic and benthic foraminifers, the abundance, preservation, and diversity of which appear to be very variable. van Hinte, J. E., Wise, S. W., Jr., et al., Init. Repts. DSDP, 93: Washington (U.S. Govt. Printing Office). 2 Address: Laboratoire de Micropaléontologie et de Géologie Marines, Université de Nice, Pare Valrose, 06034 Nice Cedex, France. METHODS Each of the samples (~ 15-20 g) was dried, weighed, boiled in a Calgon solution, arid wet-sieved with a minimum mesh size of 63 μm. The residue was occasionally submitted to ultrasonic treatment. The > 160 μm fraction obtained by dry-sieving was divided into two parts. One fraction was considered in the biostratigraphic study, the other was quantitatively analyzed after the residue was microsplit and at least 250 specimens had been counted. BIOSTRATIGRAPHY Planktonic Foraminiferal Zonation The vertical distribution of planktonic foraminifers in Cores 1 to 25 of Hole 604 is presented in Figure 4. Cores 26 to 31 (the deepest Miocene part of the hole), characterized by very poor core recovery and low foraminiferal content, are omitted. From a preliminary examination of planktonic foraminiferal distribution in Hole 604, it appears that the associations are generally dominated by three long-ranging, temperateto cold-water species, Globorotalia inflata, Globigerina bulloides, and Neogloboquadrina pachyderma. Compared with assemblages from the Atlantic tropical/subtropical province, warmer-water species such as keeled globorotaliids, Pulleniatina spp., and Globigerinoides spp. are clearly in a minority in Hole 604. Biostratigraphically these warmer-water forms often constitute the best markers. Their rarity or even, at times, their absence therefore generates serious difficulties for the foraminiferal biostratigraphic analysis of this sequence. It is never certain, for instance, that the lowest and highest occurrences of each species in the hole effectively coincide with the first and last appearance datums of the taxon. I have attempted to subdivide the

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Distribution of Neogene and Quaternary Planktonic Foraminifers from the Upper Continental Rise of the New Jersey Margin (Western North Atlantic), Deep Sea Drilling Project Leg 93, Site 604: Sedimentary and Paleoceanography Implications of the Biostratigraphy