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 Hil l Pond, eastern Newfoundland, includes the late-glacial and early Holo cene and contains strong sedimentological and paleoecological evidence for a climatic oscillation correlative with the Younger Dryas event. Basal late-glacial minerogenic sediments are overlain by a silty gyttj a marking the onset of organic sedimentation. An overlying unit compri sing 7 cm of silty clay marks a return to mineral sedimentation prior to subsequent uninterrupted deposition of organic sediments. During th is phase, the reversion from shrub tundra to a sparser herb-shrub tund ra pollen assemblage (Oxyria digyna, Artemisia) is a strong indicator of climatic deterioration at the site. The paleolimnological expressio n of the Younger Dryas event at this site is manifested by a sharp dec rease of diatom concentrations followed by decreases in the relative f requencies of Fragilaria spp., which are largely replaced by a stratig raphically restricted group of unusual benthic forms, a rise in the re lative frequency of chrysophyte cysts, and a crash in Pediastrum conce ntrations. The nature and timing of palynological and diatom changes a re interpreted in terms of both the direct and indirect consequences o f climatic deterioration, as well as within the stratigraphic context of sediment lithological changes.