Dinoflagellate cysts and other marine palynomorphs from Lower Eocene through Lower Pliocene sediments of the Labrador Sea and Baffin Bay
Cenozoic sediments recovered during Leg 105 of the Ocean Drilling Program in Baffin Bay (Site 645) and the Labrador Sea (Sites 646 and 647) have yielded a persistent record of dinoflagellates and other marine palynomorphs. Hole 647A in the Labrador Sea contains an almost complete deep-water record of early Eocene through early late Oligocene sedimentation. Dinoflagellate assemblages indicate outer neritic to oceanic conditions throughout, but with possible increased influence from shelf environments during the early Eocene. Lower Eocene dinoflagellate assemblages are similar to coeval assemblages from the Rockall Plateau, but those from the middle through upper Eocene have mixed affinities, and are perhaps related to intensification of the proto-Gulf Stream. Oligocene dinoflagellate assemblages suggest the influence of both Arctic and North Atlantic watermasses at this site. A diverse marine palynoflora was recovered from upper Miocene and lowermost Pliocene sediments of Hole 646B in the central Labrador Sea. Palynomorph assemblages are thought to be largely allochthonous and may reflect changing bottom-water paleocurrents. The dinoflagellate flora consists of both oceanic and neritic species and indicates temperate surface-water conditions. Lower through lower upper Miocene dinoflagellates recovered from Baffin Bay (Hole 645E) indicate a cool-water, neritic environment. Assemblages have North Atlantic and Norwegian Sea affinities, but also contain notable protoperidiniacean elements. Dinoflagellate biostratigraphy estimates initiation of ice rafting in Baffin Bay at between 7.4 and 9.5 Ma. Increased terrigenous influx and apparent disappearance of certain dinoflagellate taxa occur in the middle to late Miocene and may be related to oceanographic changes or climatic deterioration. The erection of three new dinoflagellate genera, 19 new dinoflagellate species, and three new acritarch species, are among the many taxonomic proposals contained in this study of the Miocene. Several Miocene holotypes from Japan, have also been studied and compared to the Leg 105 material.