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TitleRelative timing of sediment failures within slide-valley complexes in the Kugmallit Fan area of the central Beaufort Slope
AuthorCameron, G D MORCID logo; King, E L; Blasco, S
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 40, 2017 p. 47 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20170133
PublisherGeological Association of Canada
MeetingGAC-MAC Annual Meeting; Kingston; CA; May 14-18, 2017
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
AreaKugmallit Fan; Beaufort Slope
Lat/Long WENS-136.0000 -132.0000 70.0000 69.0000
Subjectssurficial geology/geomorphology; slope failures; coastal environment; coastal erosion; bathymetry; sonar surveys; submarine features; landslides
ProgramPublic Safety Geoscience Marine Geohazards
Released2017 01 01
AbstractHydrocarbon related activities on the Beaufort Slope raises concerns about slope geohazards. Ubiquitous seabed and shallow sub-surface sediment slide complexes have been identified on the Beaufort Slope, from multibeam bathymetry and high-resolution sub-bottom sonar data collected mainly in 2009 and 2010. Multiple shallowly-buried failures indicate a long-term history of periodic failure, but those at the seabed are generally larger.

Two geologically recent, large, multiple-event failure complexes have been identified; the Ikit and Kugmallit slide-valley complexes. Neither have appreciable overlying sediment despite continuous Holocene deposition recognized from sonar profiles in nearby parent sediment. The Ikit complex is about 24 km wide, along the shelf break and about 54 km downslope, with undefined total run-out, covering over 1900 sq. km. The Kugmallit complex is narrower at 14 km wide and 68 km long, with undefined total run-out, covering 1550 sq. km.

Some failure scarps exceed 100 m relief and evacuated volumes exceed 100 cubic km, placing these amongst Canada¿s largest surficial failures. Stratified Holocene and largely glacigenic blankets, tens to over 100 m thick including presumably LGM material, have been removed in the deepest valleys. Failures span the entire post-glacial sediment sequence, but an underpinning buried interval appears more prone to collapse.

Large and numerous retrogressive failure types are identified within the slide valley complexes. Blocky to disintegrated rotational slumps have been identified and occur near the top of the valleys. Numerous and thick (10s to 50m) debris flows have been identified with cross-cutting lobes and tongues which have runouts from 100s of m to 100 km. Relative timing of as many as five failure events is recognized, based on cross-cutting relationships. Maximum failure event age is constrained locally by recognition of translated parent blocks as young as 1300 years BP cal. in shallow cores. Minimum ages are pending from Pb 210 age dating of 8 to 25cm thick post-slide mud in push cores.

Removal of confining sediments presents opportunity for continued retrogressive failure. Failure-prone unit behavior suggests sediment preconditioning in the subsurface . The state of in-situ or introduced excess pore pressures in the region is not known. Proximity to an earthquake cluster suggests a trigger mechanism for episodic and widespread failure, but temporal and causal relationships are not yet established.
Summary(Plain Language Summary, not published)
Hydrocarbon related activities on the Beaufort Slope raises concerns about geological hazards in the area. Two geologically recent, large, multiple-event sediment failure complexes have been identified. Relative timing of as many as five failure events is recognized. Age dating constraints suggests that these failures may be young in age. Proximity to an earthquake cluster suggests a trigger mechanism for episodic and widespread failure.

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