Submarine geomorphology of a glaciated active margin, British Columbia, Canada

Abstract

Based on high-resolution multibeam-sonar data and low-resolution (GEBCO) data we classify the geomorphology of Canada’s Pacific margin within the four bioregions designated by Fisheries and Oceans Canada for management of biological resources. We designate fourteen units. Nine continental shelf units are: fiords, bedrock terrain, offshore banks, Haida Gwaii platform, Haida Gwaii shelf, Vancouver Island shelf, incised shelf, glacial trough, and major delta. On the continental slope we identify the canyon zone, the accretionary wedge (off Vancouver Island), and the transform (Queen Charlotte Fault) terrain. The abyssal zone is treated as a single unit with two components: seafloor spreading terrain, and abyssal plain with fans, seamounts, and channels. Hexactinellid sponge reefs of various morphologies are found in three of the continental shelf geomorphic units, and cover up to 10 % of the seafloor in the glacial trough category. Examples based on multibeam sonar imagery are used to display the chief characteristics of the fourteen units as well as the geomorphic diversity within them. Compared with Canada’s east-coast glaciated passive margin, geomorphic similarities include: 1) the panoply of glacial landforms; and 2) shelf terrain dissected by sub-glacial meltwater. Major differences include: 1) the presence of unique ‘tectonic’ terrains on the Pacific continental slopes; 2) hexactinellid sponge bioherm reefs are unique to the Pacific margin; 3) the absence of glacio-tectonic terrains on the Pacific shelves; and 4) the absence of ‘classic’ trough-mouth fans on the Pacific margin.