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TitleDynamics of sediments on a glacially influenced, sediment starved, current-swept continental margin: the SE Grand Banks Slope off Newfoundland
 
AuthorRashid, HORCID logo; Piper, D J WORCID logo; MacKillop, K; Ouellette, D; Vermooten, M; Muñoz, A; Jiménez, P
SourceMarine Geology vol. 408, 2018 p. 67-86, https://doi.org/10.1016/j.margeo.2018.11.012
Year2018
Alt SeriesNatural Resources Canada, Contribution Series 20180295
PublisherElsevier BV
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceEastern offshore region; Newfoundland and Labrador
Lat/Long WENS -48.5833 -46.1667 46.5000 45.2500
Subjectsmarine geology; surficial geology/geomorphology; geophysics; geochemistry; engineering geology; mineralogy; stratigraphy; continental margins; continental slope; marine sediments; contourites; muds; currents; landslide deposits; debris flow deposits; glacial deposits; tills; landslides; debris flows; slope failures; isotopic studies; oxygen isotopes; x-ray fluorescence analyses; marine sediment geochemistry; marine sediment cores; geophysical surveys; acoustic surveys, marine; side-scan sonar; bathymetry; seismic surveys, marine; seismic reflection surveys; seismic profiles; geological history; glacial history; depositional history; sedimentation; stratigraphic analyses; stratigraphic correlations; sediment transport; sediment distribution; source areas; scarps; escarpments; gullies; channels; slope stability analyses; atterberg limits; plastic limit analysis; liquid limit analysis; earthquakes; facies analyses; models; Grand Banks Slope; Laurentide Ice Sheet; Heinrich Layers; Labrador Current; glaciomarine sediments; ice streams; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; tables; seismic profiles; profiles; lithologic sections; geophysical logs; plots; correlation sections; models; cartoons
ProgramPublic Safety Geoscience Marine Geohazards
Released2018 11 22
AbstractThe SE Grand Banks Slope is unusual on the glaciated eastern Canadian margin in that it was remote from ice stream and glacial ice of the Laurentide Ice Sheet (LIS). It thus allows an analysis of the role of contour currents and landslides in sculpting the continental margin, processes that are largely masked where downslope proglacial sediment supply dominated. Detailed oxygen isotope, geotechnical, pXRF, and bulk sediment geochemical analyses were made on seven piston cores and were placed in context using multi-beam bathymetry and high-resolution seismic reflection profiles. Cores have a record of sedimentation back to MIS6 preserved in autochthonous sediment and slide blocks, contourites and mass-transport deposits (MTDs). Detrital?carbonate-rich Heinrich layers (H) are present throughout the succession, but red mud layers of glacial meltwater origin from ice-streams in the SE sector of the LIS are identified only during MIS2 and late MIS3. Both layers allowed high-resolution correlation between cores. Sediments on the upper slope above H2 are condensed and the section above H1 is<50 cm thick, indicating that the powerful Labrador Current winnowed the section above H2. In contrast to the upper slope, approximately 3 to 5m sediments were recorded in the mid-slope above H2 suggesting that the Labrador Current was weaker. Regional stratigraphic variations compared to Flemish Pass and Orphan Basin to the north suggest that NE Newfoundland sources of sediment played an important role and may have been previously underestimated. This study demonstrates that across-margin thickness variations reflect the character and distribution of the Labrador Current sediment transport system through time.
Five horizons with MTDs with headscarps generally up to 25m high are recognized in the upper 50-70 m. Thick MTDs are blocky in cores and in their seismic and bathymetric expression resemble spreads, with local thin mud clast conglomerates that ran out as debris flows over the contemporaneous seabed. Geotechnical data suggest that the seabed is stable under static conditions, although there is geological evidence for fluid escape and geotechnical evidence for under-consolidation. Weak layers along which failure took place are found somewhere around H3-H4 and at or near the top of H5 and MIS6. The low plasticity and liquid limit of the H layers make these layers susceptible to failure during cyclic loading. Episodic earthquakes are the most likely cause of failure.
Summary(Plain Language Summary, not published)
Defines the style, age and weak layers of submarine landslides in the Salar Basin, SE Grand Banks Slope.
GEOSCAN ID313096

 
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