The palynological record of Labrador Sea is from the ODP Site 646 located on the southwest Greenland rise. The chronostratigraphy is well constrained by the marine microfossil biostratigraphy and the magneto- stratigraphy. Sedimentation rates appear relatively uniform throughout the sequence and average ~9 cm/ka. Palynological analyses were performed in the Plio-Pleistocene sediments (480-0 m; 5.4-0 Ma) at 1.5 m intervals, which provided a time resolution of ca. 16 kyr. The Pliocene deposits are characterized by abundant prasinophytes (Cymatiosphaera) and dinoflagellate cysts (Protoperidiniales and Gonyaulacales). In the Gauss chronozone (3.4-2.47 Ma), the marine palynomorph assemblages reflect relatively low salinity (varying from 32 to 35 ppt), likely due to freshwater runoff, and cool conditions (ca. 8 to 11°C in summer) rather similar to present. Most samples are characterized by abundant pollen (> 1000/cm3), suggesting the existence of a dense vegetation over the source areas, the eastern Canada and Greenland. The assemblages are dominated by Pinus with common Picea, Tsuga, Sciadopitys, Betula and Alnus, along with Pteridophyte and Sphagnum spores. Such assemblages suggest influx from two main sources: (1) tree-pollen fluxes originating from a coniferous forest, where cool temperate and humid conditions prevailed according to the significant occurrence of Sciadopitys and Tsuga; and (2) inputs of shrub taxa pollen grains (Betula, Alnus and Ericaceae) originating from an open vegetation of forest tundra and shrub tundra related to a humid subarctic climate. The pollen and spores content of sediments probably relate to atmospheric influxes from southeastern Canada, where temperate conditions prevailed, in addition to fluvial inputs from southern Greenland, where subarctic climate can be inferred. The Pliocene interval, including the Gauss chronozone, is marked by small scale fluctuations in concentrations and taxa percentages, indicating changes in vegetational cover, hydrological conditions over southern Greenland and/or atmospheric trends across the Labrador Sea. A major shift in the Pliocene palynological record of the Labrador Sea occurs at about 2.5 Ma, coinciding with the first regional input of ice-rafted debris and the initiation of glaciations about the North Atlantic Ocean--a drastic drop in pollen and spore concentrations is accompanied by the decline of Sciadopitys and Tsuga, which indicates impoverishment of the vegetational cover and significant cooling in the source areas. In the central Baffin Bay, the drilling of 1200 m of sediment at ODP Site 645 revealed a sequence spanning the entire Neogene. The marine microfossil records are poor, notably because of sparse productivity and because of biogenic carbonate dissolution. Nevertheless, the magnetostratigraphy and a few biostratigraphic datums allowed to set a reasonable chronostratigraphy. Sedimentation rates throughout the Plio- Pleistocene are relatively high, (13.5 cm/kyr). Palynological analyses were performed at 1.5 to 3.0 m interval in Pliocene sediments. Above the Gilbert-Gauss boundary (3.4 Ma), the marine palynomorph assemblages are dominated by prasinophytes and protoperidiniales, which indicate a low salinity (<30ä), estuarine type environment. Abundant pollen and spores (up to 50,000/cm3) were recovered in most Pliocene samples, which indicates a dense vegetational cover in adjacent terrestrial areas, the Baffin Island and Greenland. The assemblages are characterized by both coniferous trees (Pinus and Picea) and non-arboreal (Alnus, Betula, Ericaceae, Sphagnum) components. Such assemblages closely resemble those of the modern Hudson Bay: they suggest the existence of coniferous boreal forest to shrub tundra vegetation with extensive peatlands in terrestrial regions surrounding Baffin Bay. During the Pliocene, the transition between the subarctic and low Arctic bioclimatic zones was probably located in the southern Baffin Bay region, 5o to 7o north of the present limit. The Gauss interval is marked by fluctuations in pollen and spore concentrations and percentages. These variations may reflect changes in vegetation source, fluvial inputs, atmospheric trends and/or sedimentary processes. They probably respond to climatic fluctuations, which may also be related to recurrent growth and decay of ice caps in circum-Arctic areas as shown by ice-rafting deposition in Baffin Bay. However, strong increase in ice-rafting deposition related to major glaciation is dated back to ca. 2.5 Ma.