A palynological investigation of the late Quaternary vegetational history of the Baie Verte Peninsula, northcentral Newfoundland

Dyer, Alison K. (1986) A palynological investigation of the late Quaternary vegetational history of the Baie Verte Peninsula, northcentral Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Palynological studies of peat and lacustrine sediments in Atlantic Canada have provided outlines of the late- and postglacial development of the vegetation. Furthermore, these vegetational changes have permitted researchers to interpret late-glacial and Holocene climatic changes. On the Island of Newfoundland, however, the relative paucity of palynological work has hampered the development of a regional synthesis of vegetational and climatic history. This thesis examines the sequence of vegetational changes in northcentral Newfoundland in order to add to the knowledge of late Quaternary palaeoenvironments of this province. -- Duplicate cores from two lakes on the Baie Verte Peninsula were obtained for pollen analysis, radiocarbon dating, and loss-on-ignition analysis. The results indicate that the Peninsula was ice-covered during the Late Wisconsin and that the ice limit probably extended at least to the northern terminus. The northern highlands were deglaciated by 11,800 BP and dissipation of the ice progressed by downwasting and ice recession toward the interior of the peninsula. -- Pollen percentage, concentration and influx diagrams are presented and a tentative regional pollen zonation for the northern Baie Verte Peninsula is proposed as follows: (I) Gramineae-herb zone, before 11,800 BP; (IIa) Betula-Cyperaceae subzone, 11,800 to 10,000 BP; (IIb) Shrubs-Picea subzone, 10,000 to 8500 BP; (IIIa) Alnus-Abies subzone, 8500 to 6700 BP; (IIIb) Betula-Picea-Alnus subzone, 6700 to 3200 BP; (IV) Picea-Betula-Alnus zone, 3200 BP to present. -- Pioneering communities were replaced by a dwarf-shrub tundra after 11,800 BP. A prolonged shrub-tundra phase was probably a result of residual ice in lowland areas which acted as a physical barrier to tree migration and which may have affected the local climate. Arboreal immigration commenced after 9500 BP with Picea. The closing of the forest canopy and the development of a white birch-black spruce forest occurred after 6700 BP. From that time to about 3200 BP the climate was warmer and drier than at present. A subsequent cooling trend is inferred primarily from a resurgence of black spruce at the expense of white birch. A significant decline in total pollen abundance after 2000 BP is attributed to a decrease in the density of the regional vegetation and decreased sediment focussing.

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