Dinoflagellate cysts of ODP Leg 101 holes

The Albian-Cenomanian sediments in Holes 627B and 635B contain diverse dinoflagellate-cyst assemblages, which show affinities with coeval assemblages from offshore Morocco and northwest Europe. A total of 34 samples were analyzed from the shallow-water platform sediments and neritic marly chalk of Hole 627B and from the argillaceous chalk and limestone of Hole 635B. Dinoflagellate cysts indicate that the top of the shallow-water platform drilled at Hole 627B must be attributed to the late Albian. Dinocysts also date the drowning of the carbonate platform of the Blake Plateau. This drowning started in the latest Albian (Vraconian) and continued into the Cenomanian. The site area changed from an inner to intermediate or outer(?) neritic environment. The area around Hole 635B from the late Albian appears to have been situated in a deeper environment than the area around Hole 627B during the same period. The new dinoflagellate-cyst species Compositosphaeridiuml bahamaensis n. sp., Maghrebinia breviornata n. sp., and Subtilisphaeral habibi n. sp. are described, and Pervosphaeridium truncatum is emended. Additional taxonomic remarks about other species are included.

Range chart for Tertiary ostracodes from ODP Hole 101-628A (Table 1)

The Oligocene to Pliocene section from Hole 628A supplied about 100 species of Tertiary ostracodes. Deep-sea psychrospheric? species (Bradleya cf. dictyon, Agrenocythere cf. gosnoldia, Cardobairdia spp., Henryhowella sp., Cytheropteron spp., etc.) are present throughout the section. Starting in the Miocene, neritic species (Hulingsina sp., Puriana spp., Caudites spp., Loxoconcha fischeri, Cytherelloidea sp., etc.) dominate. Redeposition of these species from the continental shelf seems to be penecontemporaneous with sedimentation. Variations in the assemblages indicate biostratigraphic position. Species having an ecologic or stratigraphic importance are discussed and illustrated.