The bathymetry of Barkley Sound and the adjacent continental shelf off Vancouver Island, has been affected by glacial erosion. Several fiords 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 which terminates at the 200-m isobath, some 58 km from shore.

Studies of surficial sediments for size, color, mineralogy, organic carbon, CaCO₃, and fauna, led to recognition of 5 sediment types: (1) modern sediments, at present accumulating in Barkley Sound, 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 are present 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

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remains, are present on small banks and beaches in Barkley Sound.

Mineralogically, relict and modern sands are similar, consisting mainly of detrital plagioclase and lithic fragments. However, there are marked differences between heavy mineral suites, which led to the establishment of the Barkley Sound and continental shelf provinces. The ultimate sources of the sediments are mainly Mesozoic diorites and intermediate-basic volcanic rocks.

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