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The climatic and vegetational history of the postglacial in Central Saskatchewan



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Pollen and diatom samples from three lakes in the La Ronge area of central Saskatchewan provide information on the vegetation and climate for a period of time from 9,000 years ago to the present. Pollen stratigraphy can be presented in percentage form and as absolute influx data. Both methods were employed and fanned the basis of a numerical stratigraphic zonation and a description of vegetational sequences. From approximately 9,000 to 8,100 years ago the level of Glacial Lake Agassiz dropped from its Campbell Phase level of 423 m to below 370m above sea level. At this time most presently existing water-bodies became in outline and area much as they are today. The ice retreated from the Cree Lake Moraine close to 9,000 years ago, allowing Glacial Lake Agassiz to drain to the east. It is suggested that before 9,000 years ago the Polar Air Mass dominated the region. This resulted in stagnation of the glacier and stabilization of a zone of treeless vegetation close to the ice front. It also explains why tree pollen are absent from the lake sediments. After 9,000 years ago, the Pacific Air Mass became dominant, causing rapid ice retreat and permitting the northward expansion of spruce forest. Approximately 8,500 years ago, or even earlier, tree pollen became an important component of the pollen assemblage. From approximately 8,000 to 6,700 years ago, first alder and then pine migrated into the La Ronge area. This resulted in a true boreal forest much like the one now growing there. Between approximately 3,500 to 3,000 years ago, the conditions became slightly cooler and/or moister, rather like today's climate. Diatoms, several of which have not been previously recorded from Saskatchewan, reveal little additional information. Lake waters remained relatively unaltered since organic or calcareous sedimentation began 8,000 years ago. Only the southernmost of the three lakes studied, Marl Pond, displays a brief change from its normally slightly basic waters to slightly acidic, approximately 3,500 years ago. A more recent fluctuation to acid conditions is not yet clearly reflected in the diatom flora. ***Omissions*** Page 110, Para.2, Line 8, Ritchie (1968, p.325) should read: Lichti-Federovich and Ritchie (1968, p.325). Page 136, the omission of: Mott, R.J., 1975, Palynological studies of lake sediment profiles from southwestern New Brunswick: Canadian Journal of Earth Sciences. 12,pp. 273-288





Doctor of Philosophy (Ph.D.)


Geological Sciences


Geological Sciences




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