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TitleGeological processes on the Canadian Beaufort outer shelf and upper slope
AuthorBlasco, S; Bennett, R; MacKillop, K; Hughes-Clarke, J; Church, I
SourceASM2010 Conference Programme and Abstracts; 2010 p. 30
Alt SeriesEarth Sciences Sector, Contribution Series 20100319
MeetingArrcticNet Annual Science Meeting 2010; Ottawa; CA; December 14 - 17, 2010
ProvinceNorthern offshore region
AreaBeaufort Sea; Beaufort Shelf
Lat/Long WENS-140.0000 -132.0000 72.0000 69.0000
Subjectssurficial geology/geomorphology; paleoclimates; continental shelf; continental slope; glacial history; sea level changes; sea level fluctuations; depositional environment
ProgramOffshore Geoscience, Marine Geoscience for Arctic Economic Development
AbstractBeaufort 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 Amundsen has 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 upper slope. Sediment laden meltwater discharge across the shelf from the ablating Laurentide ice sheet provided the sediment source. Sheet flow 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 associated sea 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 ice-bearing permafrost appears to be correlative with the shelf break and sea level lowstand at the 100 m isobath. Pingo-like 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 edge in 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 significantly down slope. Upwelling processes at the shelf edge over time have prevented the accumulation of sediment over the last 9,000 years.