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TitleAge, frequency, and magnitude of diverse post-glacial and recent seabed instabilities on the Canadian Beaufort Sea margin
AuthorKing, E; Cameron, GORCID logo; Riedel, M; Li, MORCID logo; Blasco, S; Stashin, S; Ouellette, D; MacKillop, K; Paull, C; Dallimore, SORCID logo; Kuzyk, Z Z; O'Connor, D; Rohr, K; Côté, M; Duchesne, MORCID logo; Jin, Y K
SourceArctic Change 2020 abstracts (continued); Arctic Science 2021 p. 342, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20210425
PublisherCanadian Science Publishing
MeetingArctic Change 2020; December 7-10, 2020
Mediapaper; digital; on-line
File formatpdf; html
ProvinceNorthern offshore region; Northwest Territories; Yukon
AreaBeaufort Sea; Beaufort Shelf; Banks Island Shelf
Lat/Long WENS-155.0000 -112.0000 76.0000 68.0000
Subjectsmarine geology; surficial geology/geomorphology; stratigraphy; geophysics; Science and Technology; Nature and Environment; Health and Safety; continental margins; marine sediments; sediment stability; landslides; landslide deposits; debris flows; debris flow deposits; mass wasting; tsunami; structural features; faults; diapirs; currents; erosion; permafrost; ground ice; periglacial features; pingos; geophysical surveys; seismic surveys, marine; stratigraphic analyses; scarps; glacial history; glaciation; glacial erosion; earthquakes; earthquake magnitudes; salinity; depositional history; Risk assessment; Arctic; Phanerozoic; Cenozoic; Quaternary
ProgramPublic Safety Geoscience Beaufort Sea Exploration
Released2021 06 22
AbstractGeological framework investigations of the Beaufort Sea margin have identified five modes of post-glacial seabed and shallowly buried sediment instability: mega-scale slide failures, buried debris flows, large faults, current-induced erosion, and pingo (diapir) activity. Evaluating these modes is important for risk assessments, including tsunami potential, in Arctic communities. Morphological and seismostratigraphic cross-cutting relationships of mass failures tied to a core-based chronology reveal a large and recent component activated ~1.5 kyr ago, but lesser events on over-steepened scarps, occurred in the past century. Thus, despite demonstrated geotechnical stability in the (un-failed) uppermost sediments, failures are common, perhaps from factors at greater depth. Relating these to the deepest cut (>200 m) seabed valleys remains challenging making risk assessments premature. A small map area revealed twenty buried failures (millions m3 to 21 km3) which stem from at least 10 separate post-glacial and Holocene debris flow events, indicating a 1.5-3.5 kyr periodicity. Long-lived, periodic pre- and early glaciation failures are also common and are attributed to earthquake triggering and sediment pre-conditioning, including brackish porewater and rapid deposition. Deep-seated faults (>4 km) on the Beaufort Shelf appear inactive since onset of glaciations, but normal listric growth faults are present on the outer Banks Island Shelf. With >200 m down throw at depth and 10s to 100 m at the seabed, many cut the glacial erosion planes, for 10s of km along strike. Their earthquake magnitude reconstruction or tsunamigenic potential remains largely unknown. Beaufort Shelf-edge bottom currents, extrapolated from mooring data or measured directly, indicate periodic sediment erosion, locally from 5% to 17% of the time. This is spatially compatible with seabed erosion (10s cm to 10s m of removal) that initiated in the mid-Holocene. Shelf-break pingo (sediment/ice diapir) fields are now demonstrated to be structurally active.
Summary(Plain Language Summary, not published)
Marine investigations of the Beaufort Sea area identifying diverse forms of seabed instability are shown to be uncommonly active, including mega-scale mass failures, buried mudslides, large faults, current erosion, and pingo mounds/craters. Mapping and age-dating the mass-failures indicate a large event(s) was recent, ~1.5 kyr ago, but lesser events span time since glacier retreat and into the past decades. Their occurrence seems incongruous with geotechnical measurements, suggesting deeper-seated instabilities beyond reach by our techniques. Unique properties of the sediment and earthquakes seem to contribute. Faults are common but are only recent enough to reach the seabed in the east, causing large submarine cliffs. If they caused tsunamis is unclear. Local seabed current analysis indicates periodic sediment erosion, compatible with mapping observations. Some shelf-edge sediment/ice mounds and craters (pingos) are actively collapsing.

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