Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins Peter T. Harris a,n , J. Vaughn Barrie b , Kim W. Conway b , H. Gary Greene c a Geoscience Australia, Environmental Geoscience Division, GPO Box 378, Canberra ACT 2601, Australia b Natural Resources Canada, Geological Survey of Canada: Pacific, Institute of Ocean Sciences, PO Box 6000, Sidney, BC, Canada V8L 4B2 c SeaDoc Society/Tombolo Lab, 942 Deer Harbor Rd., Eastsound, WA 98245, USA article info Available online 16 July 2013 Keywords: Submarine canyon Strike–slip fault British Columbia Canada Continental slope processes Canyon evolution Tectonically active continental slopes 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 (1200–1400 m 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 50–60 mm/yr and a small convergent component equal to about 3 mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500–3500 m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200–1400 m water depth). Consequently, canyons along this margin are short (4–8 km in length), closely spaced (around 800 m), and terminate uniformly along the 1400 m 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 4000 m depth, across the full breadth of the slope. Crown Copyright & 2013 Published by Elsevier Ltd. All rights reserved. 1. Introduction Submarine canyons incised into the continental slopes of active plate margins are subject to modification by tectonic processes. Orogenic and local compressional uplift produces a steep, moun- tain sediment source, and frequent earthquakes provide triggers for turbidity currents, factors which coincide with the greater occurrence and closer spacing of canyons on active versus passive continental margins (Harris and Whiteway, 2011). Submarine canyons in tectonically active regions may contain geomorphic expressions that relate to different forms of faulting. For example, canyons that incise margins characterized by strike–slip faulting exhibit thalwegs that are offset by horizontal displacement (Greene and Clark, 1979; Nagel et al., 1986; Greene and Hicks, 1990). Canyons that cut across extensional dip–slip faults might contain knick points (reaches of anomalously steep gradient) migrating up the thalweg (Mitchell, 2006), or a step or lip might be formed where reverse faulting occurs. In cases where extensional faulting is rapid compared with the rate of canyon entrenchment, hanging canyons might be formed. In this study we examine the geomorphology of submarine canyons located on the active plate margin off British Columbia, Canada, which is influenced by the Queen Charlotte Fault Zone (QCFZ). The results are compared and contrasted with canyons located adjacent to Monterey Bay, California, which are located on the central part of the San Andreas fault system and which are among the best-known canyon systems on earth. The main aim of this work is to attribute particular aspects of canyon morphology to the dominant tectonic process that caused their formation. 1.1. Queen Charlotte Fault Zone The QCFZ extends for over 350 km along the western margin of British Columbia offshore of the Haida Gwaii (Queen Charlotte) archipelago (Fig. 1) and is the northern equivalent of the San Andreas Pacific Plate–North American Plate boundary. This fault zone is near-vertical in dip and seismically active down to  21 km (Hyndman and Ellis, 1981) with mainly right–lateral transform motion of approximately 50–60 mm/yr (Prims et al., 1997; Rohr et al., 2000). The QCFZ extends northwards as the Fairweather Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsr2 Deep-Sea Research II 0967-0645/$ - see front matter Crown Copyright & 2013 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsr2.2013.06.017 n Corresponding author. Tel.: +61 04389 81162; fax: +61 02 6249 9920. E-mail address: Peter.Harris@ga.gov.au (P.T. Harris). Deep-Sea Research II 104 (2014) 83–92