CGRG Bibliography of Canadian Geomorphology
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Author : Cullen, J.R.; and Lian, O.B.
Date : 2009.
Title : Reinterpretation of a significant lithostratigraphic unit resting on the Last Interglaciation Muir Point Formation, southwestern British Columbia.
Publication : CANQUA–CGRG Biennial Meeting. May 3-8, 2009. Simon Fraser University, Burnaby Campus, Burnaby, British Columbia.
Issue : Programme and Abstracts Volume.
Page(s) : 62.
Abstract
Sedimentary units exposed in the sea cliffs at Muir Point, southern Vancouver Island, comprise some of the most widely-studied and climatically significant units in western Canada. Resting on glacigenic diamicton and indurated non-glacial gravels of unknown age are several organic-rich units that together comprise the Muir Point Formation, the regional holostratotype for the last interglaciation (marine oxygen isotope substage 5e, c. 130–116 ka). Directly overlying the Muir Point Formation is a unit, up to 6 m thick, that consists of a complex association of fluvial sand and gravel, peat lenses, and wood (unit 6 of Alley & Hicock 1986) that, on the basis of a single finite radiocarbon age (43.6 ka BP) has been associated with the Olympia nonglacial interval (marine oxygen isotope stage 3); the unit is directly overlain by till deposited during the last (Fraser) glaciation. Palynology has indicated that unit 6 was deposited when subalpine to near tree-line vegetation grew in cool-cold conditions that were significantly moister than present (Alley & Hicock 1986). New and improved radiocarbon ages from logs extracted from unit 6 indicate, however, that the unit is older than 52 ka BP, while optical dating of quartz sand suggest that the sediments that enclose the radiocarbon dated wood were deposited about 20 ka (cal. yrs). This age information, together with the chaotic sedimentology of the unit, suggests that the sediments and wood comprising unit 6 were reworked from the underlying Muir Point Formation during the advance stage of the Fraser Glaciation. If this interpretation is correct, then the paleoecology inferred from the pollen in unit 6 reflects cold and moist climate during the onset of the Fraser glaciation rather than a period of climate deterioration that occurred during the middle of the Olympia nonglacial interval.
Bibliography of Canadian Geomorphology