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Fifty-nine samples from the basal 110 m of DSDP Hole 612 (United States Atlantic Margin) were analyzed for palynomorph content. In total, 84 species and subspecies of dinoflagellate cysts were recorded which, on comparison with published data and shipboard analyses, indicate a Campanian to Maestrichtian age for this part of the succession. The Campanian/Maestrichtian contact is taken to occur in the upper part of Core 612-69. INTRODUCTION Leg 95 of the Deep Sea Drilling Project (DSDP) drilled at two sites, 612 and 613, on the New Jersey middle slope and upper rise, respectively. Site 612 was selected to provide a stratigraphic section which would serve as a link between the COST B-3 Well on the upper slope and DSDP Site 605 on the upper rise (Fig. 1). One of the primary aims was to provide a complete Upper Cretaceous and Cenozoic section for biostratigraphic analysis of this part of the margin. This chapter deals only with Upper Cretaceous material. A full report on the Cenozoic part of the section will follow at a later date. There have been several previous studies of Campanian to Maestrichtian dinoflagellate cysts. In Europe, significant work was carried out by Deflandre (1935, 1936, 1937), Lejeune-Carpentier (1938, 1939), Alberti (1959, 1961), and, more recently, by Clarke and Verdier (1967), Kjellstrom (1973), Wilson (1971, 1974), and Hansen (1977). In Australia, there was a series of publications by Cookson and Eisenack (1958, 1960, 1962, 1968, 1970, 1974), and in New Zealand Wilson published a series (1976a, 1976b, 1983, 1984). Notable studies from the United States and Canada include those of Drugg (1967), Harland (1973), Williams (1975), Williams and Brideaux (1975), Mclntyre (1975), Benson (1976), Bujak and Williams (1978), May (1980), and Whitney (1984). In total, 59 samples were processed for this study using standard palynological techniques (Neves and Dale, 1963; Doher, 1980). Eighty-four species and subspecies of dinoflagellate cysts were recorded (see Appendix); their distribution is plotted in Figure 2. BIOSTRATIGRAPHY Site 612 The basal 25 to 26 m of the section (below Sample 612-69-2, 43-45 cm; Fig. 2) contains 48 species and subspecies of cysts, 19 of which are restricted to this inter1 Poag, C. W., Watts, A. B., et al., Init. Repts. DSDP, 95: Washington (U.S. Oovt. Printing Office). ^ Address: Department of Geological Sciences, Plymouth Polytechnic, Drake Circus, Plymouth, Devon PL4 8AA, UK. val. These include the last occurrences of Palaeohystrichophora infusorioides Deflandre, Odontochitina costata Alberti, Trichodinium castaneum (Deflandre) Clarke and Verdier, and Odontochitina operculata (O. Wetzel) Deflandre and Cookson. Also, Dinogymnium microgranulosum Clarke and Verdier, D. digitus (Deflandre) Evitt et al., D. cf. euclaense Cookson and Eisenack, Kleithriasphaeridium truncatum (Benson) Stover and Evitt, Cannosphaeropsis utinensis O. Wetzel, and Odontochitina porifera Cookson have their first occurrences in this part of the section. A number of those occurrences compare closely with the zonation proposed by Bujak and Williams (1978) on the basis of studies of offshore eastern Canada. In particular, the last occurrences of P. infusorioides, O. costata, O. operculata, and T. castaneum and the first occurrence of D. digitus are indicative of Bujak and Williams's (1978) O. operculata Assemblage Zone of Campanian age. Furthermore, Williams (1975) and Wilson (1984) suggest that C. utinensis and O. porifera, respectively, first occur in the Campanian. The record most similar to the cyst distribution at Site 612, however, is that from the Atlantic Highlands, New Jersey (May, 1980). May (1980) suggests that the last occurrences of P. infusorioides, O. costata, and Xenascus ceratioides (Deflandre) Lentin and Williams, coinciding with the first occurrences of Samlandia? angustivela (Deflandre and Cookson) Eisenack and C. utinensis, indicate a latest Campanian to earliest Maestrichtian age. The close agreement of Site 612 results with these records therefore strongly suggests that the sediments below Sample 612-69-2, 43-45 cm (Fig. 2) are of late Campanian age. The remaining 80 m of section examined here (from Sample 612-69-2, 43-45 cm to Sample 612-61-1, 40-42 cm; Fig. 2) contain 60 species and subspecies of cysts, 36 of these occurring for the first time. Stratigraphically significant occurrences include the last appearances of Cyclonephelium distinctum Deflandre and Cookson and X. ceratioides near the base of this interval, and the incoming of S. ? angustivela, Ceratiopsis diebelii (Alberti) Vozzhennikova, Cordosphaeridium fibrospinosum Davey and Williams, C. varians May, Spongodinium delitiense (Ehrenberg) Deflandre, and Dinogymnium westralium (Cookson and Eisenack) Evitt et al., and, high-

Campanian to Maestrichtian Dinoflagellate Cysts from the United States Atlantic Margin, Deep Sea Drilling Project Site 612