Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins

Abstract

Faulting commonly influences the geomorphology of submarine canyons that occur on active continental margins. Here, we examine the geomorphology of canyons located on the continental margin off Haida Gwaii, British Columbia, that are truncated on the mid-slope (1200–1400m water depth) by the Queen Charlotte Fault Zone (QCFZ). The QCFZ is an oblique strike–slip fault zone that has rates of lateral motion of around 50–60mm/yr and a small convergent component equal to about 3mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500–3500m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200–1400m water depth). Consequently, canyons along this margin are short (4–8km in length), closely spaced (around 800m), and terminate uniformly along the 1400m isobath, coinciding with the primary fault trend of the QCFZ. Vertical displacement along the fault has resulted in hanging canyons occurring locally. The Haida Gwaii canyons are compared and contrasted with the Sur Canyon system, located to the south of Monterey Bay, California, on a transform margin, which is not blocked by any accretionary prism, and where canyons thus extend to 4000m depth, across the full breadth of the slope.