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TitleA chronology of post-glacial mass-transport deposits on the Canadian Beaufort Slope
 
AuthorRiedel, M; King, E L; Cameron, G D MORCID logo; Blasco, S; Conway, K W; Dallimore, S RORCID logo; Rohr, K; Jin, Y K; Hong, J K
SourceMarine Geology vol. 433, 106407, 2021 p. 1-18, https://doi.org/10.1016/j.margeo.2020.106407
Image
Year2021
Alt SeriesNatural Resources Canada, Contribution Series 20200384
PublisherElsevier B.V.
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceYukon; Northwest Territories
AreaBeaufort Sea; Canada
Lat/Long WENS-137.0000 -133.5000 71.1667 70.3333
SubjectsScience and Technology; stratigraphy; stratigraphic analyses; sediment transport; transportation; transport mechanisms; Beaufort Slope
Illustrationslocation maps; tables; stratigraphic sections; diagrams; graphs
ProgramPublic Safety Geoscience Beaufort Sea Exploration
Released2021 01 10
AbstractExtent and chronology of 24 buried and seabed-exposed mass transport deposits (MTDs) on the continental slope of the Canadian Beaufort Sea were compiled towards a regional geo-hazard assessment of the Beaufort region. A total of 2220 lines of 3.5 kHz sub-bottom profiler (SBP) data (~40,000 line kilometres) covering an area of 9740 km2 were analyzed to allow a new understanding of regional slope instability in the region. A regionally representative seismo-stratigraphy (type section, ca. 60 m thick) of the mainly stratified sediments mantling the slope and hosting the MTDs was defined. It occurs above a marked change in sedimentation style from mainly chaotic to stratified (with the exception of the MTDs). It comprises three sedimentary units bound by two prominent marker horizons but several additional minor horizons were picked from the SBP lines for chronologic control. In total, 20 MTDs mantled by sediments, and four slope failure events not buried by subsequent post-failure sediments were identified. Relative ages for these MTDs were defined by measuring the thickness of sediments overlying the MTD and linking that sediment package to the type section. Imaging from two 3-D seismic data volumes across the study region verified the MTD nature (failure elements) and down-slope continuity. Seismic amplitude and similarity attributes, enabled identification of a further 12 MTD events incompletely imaged by the SBP data. A composite chronostratigraphy based on 14C dating of foraminifera and shells was assembled. Despite that the type section is far thicker than sediment coring limits the sub-unit thickness varies up- and down-slope such that a selection of cores across the study region enabled its compilation. The marked change in sedimentation style at the base of the type section required substantial extrapolation to age date. Simple (quadratic function) age models project that its base signals the end of the last glacial maximum (LGM, Wisconsinan, or marine isotope stage 2 glaciation) and initiation of pro-glacial plume sedimentation (the deglacial), and finally post-glacial (marine) ultimately from the Mackenzie River. The MTD abundance above this contact defines an average recurrence rate of one MTD per ~1000 yrs. However, MTDs are clustered temporally with the highest number of events occurring just prior to the onset of the Younger Dryas at around 13 ka BP (cal.).
Summary(Plain Language Summary, not published)
Using high resolution and 3-D industry seismic and multibeam bathymetric data, numerous mass transport events have been identified, mapped and approximately dated on the central Beaufort Slope spanning the latest glaciation to the Recent. They are distributed throughout a sequence of glacimarine and post-glacial mud and also include large failure complexes at the seabed. They involve small volume (under 1 000 000 cubic metres) to large volume (>50 cubic kilometres) deposits or failure scars. Several sediment cores with radiocarbon dates are used to develop simple age models and then tied stratigraphically, via the seismic, to a type section. This, in turn, is tied to the stratigraphic horizons matching the mass failures. A failure event chronology through the last ~15 thousand years is constructed. An approximate periodicity of 1000 years is identified, but with most frequent events immediately following glaciation and the largest likely within the last 1000 years or less. Several suggestions for how the sediments were pre-conditioned for failure susceptibility are suggested and a tie to a nearby earthquake cluster tentatively linked to failure event triggering.
GEOSCAN ID327121

 
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