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One hundred twenty-seven samples from DSDP Cores 535-18 to 535-79 have been analyzed palynologically and dated using dinoflagellate cysts. The taxa recorded indicate the presence of sediments of late Berriasian/late Valanginian (Sections 535-79-1 to 535-55-6) and Hauterivian (Sections 535-55-4 to 535-47-1) age. These sediments are unconformably overlain by Aptian deposits (Sections 535-46-2 to 535-43-3). Sections 535-43-2 to 535-18-1 yielded palynofloras of Aptian to Albian age. Ammonite evidence (Young, this volume), however, suggests reworking of these assemblages into Cenomanian deposits. INTRODUCTION Leg 77 of the Glomar Challenger was located in the western straits of Florida, southeastern Gulf of Mexico. The drilling conducted during the Leg is part of an overall program to study the evolution of the western North Atlantic passive margin, and to investigate the Mesozoic and Cenozoic history of the area. PALYNOLOGIC RESULTS General Discussion The Cretaceous sequence (Berriasian-Cenomanian) at Site 535 yields rich palynofloras, containing varying proportions of dinoflagellate cysts, acritarchs, chlorophycean algae and miospores. These palynomorphs occur in association with relatively large numbers of microforaminiferal test-linings and tintinnid loricas. Marine microplankton dominate throughout the sequence, with terrestrially derived miospores making only minor contributions to the assemblages. Miospore assemblages are relatively homogeneous in composition and display low taxonomic diversity. Pollen of gymnosperm origin predominate, in particular longranging species of Callialasporites, Classopollis and bisaccates. Within the late Berriasian-Aptian interval Classopollis is the most numerous miospore, reticulate angiosperm pollen first appearing in the Cenomanian. Foraminiferal test-linings are encountered in very high numbers throughout the Cretaceous at Site 535, being especially prominant in the late Berriasian-early Valanginian and Aptian-Cenomanian intervals. Throughout the late Berriasian-Hauterivian, tintinnid loricas are consistently observed. They occasionally occur in large numbers, especially within the late Berriasian-early Valanginian. 1 Buffler, R. X, Schlager, W., et al., Init. Repts. DSDP, 77: Washington (U.S. Govt. Printing Office). 2 Present address: Gearhart Geoconsultants Limited, Dyce, Aberdeen, Scotland. Preservation of individual palynomorphs is generally good, and amorphous organic matter is the dominant kerogen throughout. Terrestrially derived kerogen components (structured vitrinite and inertinite, plant cuticles, and miospores) are present in only minor quantities. Stratigraphy Emphasis during the course of this study has been on palynomorphs of marine origin, especially dinoflagellate cysts. Dating is by comparison with known stratigraphic ranges established in accurately dated European onshore sections and local ranges established at previous DSDP sites in the North Atlantic. This information is to be found in the following publications which deal with various aspects of the onshore European and offshore Atlantic Lower Cretaceous: Davey [1978 (Aptian), 1979b (Portlandian-Barremian), 1979a (Aptian-Albian)]; Davey and Verdier [1971, 1973, 1974 (Aptian-Albian)]; Duxbury [1977 (Berriasian-Barremian)]; Fisher and Riley [1980 (Kimmeridgian-Valanginian)]; Habib [1972 (Oxfordian-Cenomanian), 1978 (Berriasian-Albian)]; Verdier [1975 (Barremian-Albian)]; Williams and Bujak [1979 (Berriasian-Hauterivian)]; and unpublished research by the authors on both onshore and offshore European Lower Cretaceous. The stratigraphic distribution and relative abundance of the marine palynomorphs recovered during this investigation are shown on Figs. 1-4. In addition, the stratigraphic ranges of 49 "key taxa," which have been chosen for their chronostratigraphic potential, are shown on Fig. 5. Late Berriasian-Late Valanginian (Sections 535-79-1 to 535-55-6) Assemblages are characterized by large percentages of Chytroeisphaeridia sp. A, Diacanthum hollisteri, Gonyaulacysta helicoidea, Hystrichodinium pulchrum, H. aff. pulchrum, Tanyosphaeridium boletum, and Polysphaeridium warrenii. Microforaminiferal test-linings and large leiospheres are also conspicuous components. Many of 675 L. A. RILEY, J. P. G. FENTON

Palynostratigraphy of the Berriasian to Cenomanian Sequence at Deep Sea Drilling Project Site 535, Leg 77, Southeastern Gulf of Mexico