|Title||Relative timing of sediment failures within slide-valley complexes in the Kugmallit Fan area of the central Beaufort Slope, offshore Northwest Territories|
|Author||Cameron, G D M; King, E L; Murray, D; Kuzyk, Z A; Blasco, S|
|Source||Geological Survey of Canada, Scientific Presentation 74, 2017, 1 sheet, https://doi.org/10.4095/306013 (Open Access)|
|Publisher||Natural Resources Canada|
|Province||Northern offshore region; Northwest Territories|
|NTS||107F/05; 107F/06; 107F/11; 107F/12; 107F/13; 107F/14; 107G/03; 107G/04; 107G/05; 107G/06; 107G/11; 107G/12; 117E/07; 117E/8; 117E/09; 117E/10; 117E/15; 117E/16; 117H/01; 117H/02; 117H/07; 117H/08; 117H/09;
|Lat/Long WENS||-138.0000 -134.0000 71.7500 70.3750|
|Subjects||marine geology; surficial geology/geomorphology; geophysics; stratigraphy; geochronology; continental margins; continental slope; continental shelf; submarine fans; landslides; landslide deposits; slope
stability; slope failures; slumps; slump structures; scarps; debris flows; debris flow deposits; marine sediments; geophysical surveys; acoustic surveys, marine; sonar surveys; side-scan sonar; seismic surveys, marine; postglacial deposits; glacial
deposits; sedimentary structures; earthquakes; epicentres; seismic risk; Recent; Holocene; Pleistocene; seafloor topography; bathymetry; fluid migration; stratigraphic correlations; marine sediment cores; geological history; depositional history;
sedimentation; sedimentation rates; radiometric dating; carbon-14 dates; modelling; Beaufort Slope; Kugmallit Fan; Kugmallit Slide Valley; Ikit Slide Valley; Amundsen cruise 2009804; Amundsen cruise 2010804; Amundsen cruise 2011804; Amundsen cruise
2014804; geological hazards; multibeam bathymetry; lead dating; cesium dating; slope angles; Phanerozoic; Cenozoic; Quaternary|
|Illustrations||location maps; geoscientific sketch maps; geophysical images; profiles; correlation sections; models; diagrams|
|Program||Marine Geohazards, Public Safety
|Released||2017 10 12|
|Abstract||Hydrocarbon related activities on the Beaufort Slope raise 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.|
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.
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 flow deposits 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 areas are recognized, based on cross-cutting relationships. Maximum failure event age is constrained locally by recognition of translated parent blocks as young as 1300 cal yrs BP. in
shallow cores. Minimum Pb 210 ages for failures in Ikit Valley can be as young at 230 yrs BP.
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
|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.