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Surficial sediments of Barkley Sound and adjacent continental shelf, Vancouver Island, British Columbia Carter, Lionel

Abstract

The bathymetry of Barkley Sound and the adjacent continental shelf off Vancouver Island, has been affected by glacial erosion. Several fjords (inlets) widen and coalesce to form the Sound, which is continuous with glacially eroded basins on the inner continental shelf. Basins are flanked by flat-topped banks, the larger of which merge with /the gently sloping outer shelf. Studies of surficial sediments for size, colour, mineralogy, organic carbon, CaCO₃ and fauna, led to recognition of five sediment types. (1) Modern sediments, at present accumulating in Barkley Sound and probably in continental shelf basins, are littoral sands and gravels, and deeper water, organic-rich muds. (2). Relict sands and well-rounded gravels mantle banks and parts of the outer continental shelf. (3) Authigenic sands composed of mixed-mineral glauconite pellets occur near the shelf break, where they are closely associated with (4) residual sediments derived from submarine exposures of Tertiary mudstone. (5) Organic sediments, composed of calcareous invertebrate remains, occur on small banks and beaches in Barkley Sound, Mineralogically, relict and modern sands are similar, consisting mainly of detrital plagioclase and rock fragments. However, there are marked differences between heavy mineral suites, which led to establishment of the Barkley Sound and Continental Shelf Provinces. The ultimate sources of the sediments are mainly djorites and intermediate to basic volcanic rocks.

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