Glacial and postglacial landforms and processes adjacent to King William Island, Nunavut, Canadian Arctic Archipelago

The subaerial morphology of coastal King William Island and the bathymetry of adjacent offshore channels of the Canadian Arctic Archipelago have been explored with terrestrial/marine LiDAR and multibeam sonar surveys. During the Late Wisconsinan, the Laurentide Ice Sheet extended northward across most of the Canadian Arctic and imprinted the buried landscape. Analysis of the survey data elucidates both glacial and postglacial processes that have shaped the seafloor in channels of the south-central Canadian Arctic Archipelago. Glacial landforms include multiple, parallel, elongated, ridges many kilometres in length (mega-scale glacial lineations), and fields of drumlins; both of these features are indicative of ice flow direction, generally to the north. During ice sheet retreat, eskers and tunnel valleys formed beneath the ice and swarms of icebergs were released at the calving front. The keels of numerous icebergs incised the seabed with a pattern of furrows flanked by berms; these iceberg ploughmarks provide insight into paleocurrent directions in the archipelago during glacial retreat. Iceberg ploughmarks subaerially exposed on King William Island indicate a formerly higher sea level than at present. Postglacial landforms include raised beaches on King William Island, formed during the lowering of sea level to its present elevation. Extensive fields of small seabed pockmarks, 2 to 3 m in diameter, were likely formed by the release of gas within the sea floor sediment. A biogenic or petrogenic source for the gas has yet to be determined. Enigmatic, flat-bottomed pits, about 30 m in diameter, may be strudel scour or may be also related to gas release. Work is continuing to determine if Hexactinellid sponge reefs populate Victoria Strait west of King William Island. The seabed morphology in Victoria Strait strongly resembles that of sponge reefs mapped in the Pacific Ocean off British Columbia, where these reefs preferentially grow on ridges of coarse-grained glacial deposits exposed on the seabed.