Quaternary environmental change in the Stikine Plateau region, northwestern British Columbia, Canada

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Records of Quaternary environmental change have been resolved on the Stikine Plateau of northwestern British Columbia. Glacial sediment has been preserved between Early Pleistocene basalt flows on Mt. Edziza and underneath Middle Pleistocene basalt flows in the Stikine River valley. The Mt. Edziza record indicates that regional ice advanced from the southwest and west of Mt. Edziza and inundated the plateau. Radiometric and paleomagnetic dating indicates sediment deposition occurred during isotope stages 24 to 26. Paleomagnetic sampling resulted in the resolution of the Jaramillo normal polarity event within the section. The Stikine River valley section indicates that river blockage and glaciolacustrine sediment deposition occurred at about 330 ± 30 ka (isotope stage 10). The blockage was a result of early ice advance in the Coast Mountains and eventual regional ice cover is indicated by till overlying the glaciolacustrine sediment. Advance-phase glaciolacustrine sediment deposited in the Stikine River valley is a record of blockage of the Stikine River by alpine glaciation during early Fraser glaciation time. The extent and thickness (>150 m) of the section indicates that a considerable lag occurred between alpine and Cordilleran ice advance into the region. Boulder lags, perched meltwater paleochannels and extensive scouring indicate that post-glacial fluvial incision was swift and that stagnant ice may have resided in the valley during deglaciation. A palynological investigation of Susie Lake, eastern Boundary Ranges, Coast Mountains, has yielded a comprehensive Late Quaternary biostratigraphic record. Paleovegetational zones record initial colonization (by 10,000 - 7800 BP), establishment of a spruce and fir forest ecotone established by warming climate (about 7800-4200 BP), gradual cooling and precipitation inc·rease accompanied by migration of lodgepole pine into the region (about 4200 - 2100 BP) and moist and cool conditions and a lowering of treeline (about 2100 BP - Present). Late Holocene oral history records are powerful tools for the resolution of physical environmental change in remote, isolated areas. Landslides have produced river blockage and flooding; the landslides occur in unstable lacustrine deposits and failure is triggered by concentrated spring runoff. Volcanic activity may have occurred as little as 160 years ago. Although subsequent verification is desirable, oral histories may provide the initial evidence of past geological events.
Bibliography: p. 289-313.
Spooner, I. S. (1994). Quaternary environmental change in the Stikine Plateau region, northwestern British Columbia, Canada (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/15661