The surficial geology of the Canadian eastern Arctic and Polar continental shelves

Abstract

We divide the Arctic continental shelf of Canada into three regions: (1) the Baffin Shelf, (2) the Arctic Channels and (3) the Polar Shelf. All are deep ice-dominated shelves largely floored by relict sediments. Iceberg scours occur to depths of 315 m on the Baffin Shelf but scours at depths deeper than this, and most in the Arctic Channels, are relict. All areas have been affected by late glacial fluctuations of the Laurentide Ice Sheet and local glaciers. Three principal seismic stratigraphic units are recognized and are interpreted as a glacial, glacial marine and postglacial stratigraphic sequence. Seismic Unit I is a transparent unit (mud) that lies in basins, Unit II is acoustically stratified with a mantling geometry and Unit III is acoustically incoherent with a constructional geometry in places. Units II and III interfinger in some areas. Core samples show that Unit I consists of bioturbated hemipelagic muds with ice-rafted sand and gravel, Unit II varies from a massive to laminated mud deposited from suspension and Unit III, rarely sampled, is a diamicton. In the Arctic Channels Unit II is noticeably thinner than it is on Baffin Shelf. Radiocarbon dates on foraminifera or bivalves indicate that the base of Unit II varies from 30,000 years to circa 8000 years, whereas postglacial Unit I was deposited over the last 5000–7000 years. During much of the Holocene the shelves have been starved of sediments as fiord basins were exposed during ice retreat and served as sediment sinks.