Abstract
The results of pollen analysis of three sections of lake sediment, sampled in the Riding Mountain area of Manitoba, suggest a tentative division of each into four zones. The lower, interpreted as representing a closed white spruce forest, is followed by an apparently treeless episode tentatively interpreted as a grassland phase; this is followed by a zone which suggests indirectly the prevalence of deciduous forests, possibly dominated by poplar, birch, and oak. The development of the mixed boreal forest, which prevails today, is marked by a rise in the spruce and alder curves. The suggestion that the sections are post-Valders in age is corroborated to some extent by a carbon-14 age measurement of 9570 years from a sample of spruce wood excavated from the bottom of a filled-in kettle in the vicinity; associated gyttja yielded a pollen spectrum very similar to the I zones of the diagrams.
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