Abstract

Surface sediments from the Labrador Sea and Baffin Bay have been examined for their palynomorph content. Pollen and spore assemblages reflect the vegetation zones of eastern Canada, although long-distance atmospheric transport results in over-representation of Pinus and spores. A linear decrease of pollen input is observed with distance from the source vegetation; the abyssal domain receives less than 2% of the initial input. The abundance of dinoflagellate cysts reflects a relatively high primary productivity in surface water masses which seems proportional to the benthic productivity, as shown by the concentrations of organic linings of foraminifers. The relative abundance of dinoflagellate cyst taxa and principal component analysis led to the definition of three assemblages that can be related to sea-surface conditions and current pattern. The modern distribution of dinoflagellate cysts was used to interpret assemblages recovered in five box cores from the deep Labrador Sea. Results reveal important changes in sea-surface conditions during the Holocene. At the end of the last glacial period, the productivity in surface waters was sparse, notably on the continental slope off southwest Greenland. Shortly after the deglaciation, the primary productivity increased, probably due to the improvement of sea-surface conditions. At about 5000 BP, the dinoflagellate cyst concentrations and fluxes reach maximum values, and the assemblages are marked by the augmentation of Nematosphaeropsis labyrinthus relative to Operculodinium centrocarpum. This trend is associated with a cooling and the increased influence of the inner component of the Greenland Current in surface water masses of the Labrador Sea. It marks the establishment of modern conditions in the basin.

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