Abstract

Howe Sound is a complex fjord in terms of geomorphology and circulation pattern. Sediment is presently being deposited in its deep basins from four distinct sources: (1) land-derived sediment from the Squamish River; (2) suspended sediment originating from surface waters influenced by discharges from the nearby Fraser River; (3) reworked Pleistocene lag deposits found on some shore platforms and sills throughout the sound; and (4) mine tailings from a defunct Cu–Zn mine. A less distinct source is sediment deposited via gravity flows from fjord wall slopes, including side-entry fanglomerate deltas, and the major Squamish River delta.Grain size data have been used to differentiate depositional versus nondepositional environments. In addition, surficial sediment samples collected from depositional basins could be modelled in terms of their size–frequency distribution and distance from source. Those that deviate from a predicted grain size distribution were found to be bimodal. Partitioning of their probability curves allows the establishment of mixing ratios of the major sediment sources, and indicates that the Squamish-derived sediment accounts for between 80 and 100% of recent Howe Sound deposition. Semi-quantitative XRD results can resolve the dispersion-directions of each source and show that: (a) mica can be used to trace the Squamish sediment source: (b) the chlorite pattern indicates the Fraser sediment source; and (c) quartz is useful in delineating pathways of sediment resuspended from lag deposits. These pathways are also substantiated by gradients in Cu, Ni, and Zn concentrations in the sediments.

You do not currently have access to this article.