Late-glacial and early Holocene environments at Pine Hill Pond, Newfoundland, Canada: evidence from pollen and diatoms

The basal 150 cm of lacustrine sediment in a 380 cm core from Pine Hill Pond, eastern Newfoundland, includes the late-glacial and early Holocene and contains strong sedirnentological and paleoecological evidence for a climatic oscillation correlative with the Younger Dryas event. Basal late-glacial minerogenic sediments are overlain by a silty gyttja marking the onset of organic sedimentation. An overlying unit comprising 7 cm of silty clay marks a return to mineral sedimentation prior to subsequent uninterrupted deposition of organic sediments. During this phase, the reversion from shrub tundra to a sparser herb-shrub tundra pollen assemblage ( Oxyria digyna, Arremisia ) is a strong indicator of climatic deterioration at the site. The paleolimnological expression of the Younger Dryas event at this site is manifested by a sharp decrease of diatom concentrations followed by decreases in the relative frequencies of Fragilaria spp., which are largely replaced by a stratigraph-ically restricted group of unusual benthic forms, a rise in the relative frequency of chrysophyte cysts, and a crash in Pediastrum concentrations. The nature and timing of palynological and diatom changes are interpreted in terms of both the direct and indirect consequences of climatic deterioration, as well as within the stratigraphic context of sediment lithological changes.