Holocene Pollen Records and Peatland Development, Northeastern Manitoba
Peatlands cover extensive parts of northeastern Manitoba that have low relief and impermeable substrates, with peat thicknesses varying between 25 and 400 cm. Peat reserves average 1.5 x 106 m3/km2. Fens, forested plateau bogs, and polygonal plateau bogs are the prevalent peatland types. The thickes...
Published in: | Géographie physique et Quaternaire |
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Main Authors: | , |
Format: | Text |
Language: | English |
Published: |
Les Presses de l'Université de Montréal
2003
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Subjects: | |
Online Access: | http://id.erudit.org/iderudit/010328ar https://doi.org/10.7202/010328ar |
Summary: | Peatlands cover extensive parts of northeastern Manitoba that have low relief and impermeable substrates, with peat thicknesses varying between 25 and 400 cm. Peat reserves average 1.5 x 106 m3/km2. Fens, forested plateau bogs, and polygonal plateau bogs are the prevalent peatland types. The thickest peat deposits consist of Sphagnum bogs that developed on glaciolacustrine or marine silt. Thinner deposits are composed of fen peat, or bog peat developed on sandy till. There is a positive relationship between peat thickness and time since postglacial emergence of the land. Also, recently emerged areas are dominated by fen peat, whereas bog peat is more prevalent on older surfaces. Pollen analysis of peat cores show that spruce trees have been abundant in the region south of Churchill for the past 6300 years. Local changes in peat type and accumulation rate occurred as bog and fen habitats changed, probably in response to changes in water table induced by aggradation and degradation of permafrost. Other taxa typical of boreal forest occupied suitable habitats similar to today, with bog and fen habitats increasing as paludification continued through time. Dans le nord-est du Manitoba, les tourbières occupent de vastes superficies peu accidentées et dont le substrat est imperméable. L’épaisseur de la tourbe varie entre 25 et 400 cm. À travers la région, le volume de tourbe moyen est de 1,5 x 106 m3/km2. Les principaux types de tourbières sont les tourbières minérotrophes, les plateaux palsiques arborés et les plateaux palsiques à polygones. Les dépôts les plus épais se trouvent dans les tourbières ombrotrophes à Sphagnum qui se sont développées sur des silts glaciolacustres ou marins. Des dépôts plus minces sont constitués de tourbe calcique ou de tourbe acide développées sur le till sableux. Il existe une relation positive entre l’épaisseur de la tourbe et le temps écoulé depuis l’émersion postglaciaire. On note également que les terrains récemment émergés sont dominés par la tourbe calcique, tandis que la tourbe ... |
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