Chapter 22 Pacific margin, Canada shelf physiography: a complex history of glaciation, tectonism, oceanography and sea-level change

Abstract

AbstractCanada's western continental shelf can be broadly divided into three geographical regions: Salish Sea, Pacific North Coast and Vancouver Island Shelf. Each region's physiography has been uniquely impacted by a history of glaciation, tectonism, oceanography and sea-level change. Retreat of the Fraser Glaciation started from the Pacific towards the mainland of British Columbia first in the north on Haida Gwaii (16 14C ka BP) then outer Vancouver Island (14 14C ka BP), and generally progressed east with ice persisting on the Fraser lowland and northern British Columbia mainland, and possibly the central interbasin coast, until after 10 14C ka BP. Retreat on the Pacific North Coast was rapid, while downwasting and stagnation occurred in the Salish Sea. Sea levels responded to this deglacial history, with submergence of most of the Salish Sea by over 250 m before 12 14C ka BP then falling to approximately 100 m where it remained until approximately 10 14C ka BP, and emergence of the Vancouver Island Shelf with the development of a forebulge. In contrast, the Pacific North Coast crustal loading of the British Columbia mainland and development of a peripheral forebulge towards Haida Gwaii resulted in submergence of the mainland by 120 m and emergence of the western basin by more than 120 m, with regional variation throughout. Holocene sedimentation is primarily restricted to the coastal inlets and fjords, except for the southern Salish Sea off the Fraser River.