ABSTRACT: Geological processes on the Canadian Beaufort outer shelf and upper slope.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Beaufort Sea seabed research is being conducted in response to the recent federal government release of deep water leases for hydrocarbon exploration drilling. Under the ArcticNet seabed mapping project, the CCGS Amundsenhas continued to acquire multibeam, subbottom profile and sediment sample data to define the geological framework for geohazard assessment. Initial interpretation of these data is providing an insight into the geological processes that have been active on the Canadian Beaufort outer shelf and upper slope. The dynamics of the Beaufort outer shelf and upper slope are influenced by shelf processes that have been ongoing over the last 18,000 years. Progradational distal glacial outwash deposits cover the shelf and upperslope. Sediment laden meltwater discharge across the shelf from the ablating Laurentide ice sheet provided the sediment source. Sheet fl ow shifted to channel flow during deglaciation. Late glacial meltwater density flows eroded well defined linear drainage channels into the outwash deposits both across the shelf and down slope. During the last glacial period with the associatedsea level lowstand, the shelf was subaerially exposed out to the 100m isobath. Subaerial deposition of the glacial outwash on the exposed shelf was accompanied by the aggradation of permafrost. The northern limit of icebearingpermafrost appears to be correlative with the shelf break and sea level lowstand at the 100 m isobath. Pingolike features and gas venting occur discontinuously at the shelf edge. The spatial association of these features with the northern edge of permafrost probably indicates that fluids are migrating along the base of the relatively impermeable permafrost and escaping at the shelf edge. Rising sea level resulted in erosion of the outwash sediments and the deposition of thin transgressive deposits. At the shelf edgein 100m of water these sediments at 0.3 m below seabed are dated at 9000 BP. Overlying recent mud deposits form a thin veneer at the shelf edge that thickens signifi cantly down slope. Upwelling processes at the shelf edge over time have prevented the accumulation of sediment over the last 9,000 years.

Bibliography of Canadian Geomorphology