Âge de la déglaciation finale et histoire postglaciaire de la végétation dans la partie centrale du Nouveau-Québec
Pollen and macrofossil analyses, as well as radiocarbon dating, of four cores of postglacial lake sediments collected from central Nouveau-Québec, provide an estimate of the minimum age for the disappearance of some of the last remnants of the Wisconsinan ice in Québec, and allow a reconstruction of...
| Published in: | Géographie physique et Quaternaire |
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| Main Authors: | , , |
| Format: | Text |
| Language: | French |
| Published: |
Les Presses de l'Université de Montréal
1982
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| Subjects: | |
| Online Access: | https://doi.org/10.7202/032470ar http://id.erudit.org/iderudit/032470ar |
| Summary: | Pollen and macrofossil analyses, as well as radiocarbon dating, of four cores of postglacial lake sediments collected from central Nouveau-Québec, provide an estimate of the minimum age for the disappearance of some of the last remnants of the Wisconsinan ice in Québec, and allow a reconstruction of the postglacial history of the vegetation. The final stages of déglaciation span from about 6200 to about 5600 years BP. The first date marks the time of inception of the final stagnation of the ice southwest of the terminal ice-divide and the second gives the minimum age of the final melting of the ice on the uplands north of the divide. The time which elapsed between the uncovering of the cored lake basins by the ice and the accumulation of datable organic matter in these was short due to the rapid colonisation of the newly uncovered land by trees, shrubs and herbs. Green alder (Alnus crispa) and larch (Larix laricina) dominated the landscape at first, but all the other species of trees and shrubs were already present. From ca. 5500 to 4400 years BP, the region supported a dense black spruce (Picea mariana) taiga. The main feature of the subsequent postglacial history of the vegetation is the opening of the arboreal cover around 4700 to 4400 years BP reflecting the cooling of the regional climate. The only indication of possible postglacial climatic fluctuations other than the general cooling trend are represented by two pollen influx pulses of white birch (Betula papyrifera) between 5760 and 4750 years BP and between 3600 and 2500 years BP, recorded at one of the sites. L'analyse poliinique, l'analyse macrofossile, ainsi que la datation au radiocarbone de quatre carottes de sédiments lacustres postglaciaires, ont permis d'établir l'âge minimal de la déglaciation et l'histoire postglaciaire de la végétation dans la partie centrale du Nouveau-Québec, où ont persisté quelques-uns des derniers lambeaux de la calotte glaciaire wisconsinienne au Québec. La déglaciation s'est échelonnée entre 6200 ans BP, qui ... |
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