Abstract

Materials from two glacial and two nonglacial intervals are identified on north-central Vancouver Island, British Columbia. The oldest Pleistocene unit, Muchalat River drift, consists of till and overlying glaciolacustrine silt. It has been tentatively correlated with Dashwood drift of the Semiahmoo Glaciation. An overlying single exposure of mudflow sediment in the Gold River valley contains wood dated at 40 900 ± 2000 years BP within the time span of the Olympia nonglacial interval. The Olympia nonglacial interval was characterized by a period of degradation in which Olympia-age sediments were deposited in transient sedimentary environments and subsequently eroded. Gold River drift includes Gold River advance deposits, Gold River till, and Gold River late glacial deposits, and was deposited during the Fraser Glaciation. The Fraser Glaciation was well underway on north-central Vancouver Island by 25 200 ± 330 years BP. During the Fraser Glaciation maximum, which occurred after 20 600 ± 330 years BP, Coast Mountain ice flowed in a southwesterly direction across north-central Vancouver Island overtopping all but the highest peaks of the Vancouver Island Mountains. Deglaciation commenced prior to 12 930 ± 160 years BP and the ice had probably disappeared before 9500 years ago. During postglacial times rivers have dissected older Quaternary sediments and bedrock up to at least 40 m. Macroflora data recorded in postglacial lacustrine sediments suggest that the Hypsithermal Interval commenced before 8300 ± 70 years BP.

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