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TitreRelative timing of sediment failures within slide-valley complexes in the Kugmallit Fan area of the central Beaufort Slope
AuteurCameron, G D M; King, E L; Blasco, S
SourceAssociation géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 40, 2017 p. 47
LiensOnline - En ligne
Année2017
Séries alt.Ressources naturelles Canada, Contribution externe 20170133
ÉditeurAssociation géologique du Canada
RéunionGAC-MAC Annual Meeting; Kingston; CA; mai 14-18, 2017
Documentpublication en série
Lang.anglais
Mediapapier; en ligne; numérique
Formatspdf
ProvinceTerritoires du Nord-Ouest
SNRC107C
Lat/Long OENS-136.0000 -132.0000 70.0000 69.0000
Sujetsglissements de pentes; milieu côtièr; érosion côtière; bathymétrie; levés au sonar; caractéristiques sous-marines; glissements de terrain; géologie des dépôts meubles/géomorphologie
ProgrammeRisques géo marines, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
Hydrocarbon 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.
Résumé(Résumé en langage clair et simple, non publié)
Les activités liées aux hydrocarbures sur la pente continentale de Beaufort suscitent des inquiétudes en raison des dangers géologiques dans la région. Deux complexes de glissements de sédiments à événements multiples géologiquement récents ont été identifiés. L'époque relative d'un maximum de cinq événements de glissement est connue. Les contraintes liées à la datation donnent à penser que ces glissements peuvent être récents. La proximité d'un groupe sismique suggère un mécanisme de déclenchement de glissements épisodiques et à grande échelle.
GEOSCAN ID304277