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TitleCompositional changes in deglacial red mud event beds off the Laurentian Channel reveal source mixing, grain-size partitioning and ice retreat
AuthorLeng, W; von Dobeneck, T; Just, J; Govin, A; St-Onge, G; Piper, D J WORCID logo
SourceQuaternary Science Reviews vol. 215, 2019 p. 98-115, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180365
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
ProvinceNewfoundland and Labrador; Nova Scotia; New Brunswick; Prince Edward Island; Quebec; Eastern offshore region
NTS1; 2; 10; 11; 12; 20; 21; 22
AreaLaurentian Channel; Laurentian Fan; Grand Banks of Newfoundland; Gulf of St. Lawrence; Cabot Strait; Atlantic Ocean
Lat/Long WENS -72.0000 -52.0000 52.0000 43.0000
Subjectsmarine geology; surficial geology/geomorphology; geochemistry; mineralogy; stratigraphy; continental margins; continental shelf; continental slope; glacial history; ice sheets; deglaciation; ice retreat; depositional history; marine sediments; muds; detritus; red beds; moraines; pebble lithology; provenance; source areas; grain size distribution; major element geochemistry; magnetic properties; magnetite; hematite; sediment transport; sediment dispersal; dispersal patterns; geochemical dispersion; element distribution; mineral distribution; models; core samples; bedrock geology; lithology; stratigraphic analyses; stratigraphic correlations; Laurentide Ice Sheet; Laurentian Channel Ice Stream; Laurentian Ice Stream; Grand Banks Slope; Canadian Shield; Appalachian Province; Outer Laurentian Depression; Outer Laurentian Moraine; Laurentian Moraine; Cabot Depression; glaciomarine sediments; Phanerozoic; Cenozoic; Quaternary
Illustrationsgeoscientific sketch maps; bar graphs; plots; profiles; geophysical images; frequency distribution diagrams; tables; 3-D diagrams; ternary diagrams; models
ProgramPublic Safety Geoscience Marine Geohazards
Released2019 05 23
AbstractBetween 22 and 17 cal ka BP, five large meltwater events from within the Laurentian Channel Ice Stream deposited mud beds meters thick across a large area of the Laurentian Fan and adjacent continental slopes. This study determines the sources of these event beds and relates them to the glaciological evolution of the retreating Laurentian Ice Stream. We analyzed major element and magnetic mineral contents of these event beds and compare them with a new collection of 80 source reference samples from the Gulf of St. Lawrence area. Element ratios suggest a steady compositional change from older to younger outburst event beds, while element-specific offsets from reference sample compositions indicate grain-size and mineral/element partitioning during suspension transport. Their magnetic properties place event beds on the source mixing trend of four reference samples groups, which represent two magnetite-rich sources (Canadian Shield and/or Southern Newfoundland) and two hematite-rich sources (Appalachian red beds). Using a deterministic linear source mixing model based on IRM100mT, HIRM and Ca%, we find that the earlier two outburst events had higher contributions from granitic and calcareous sources than the later three events. Combining materials, timing and scenarios of the outburst events with ice-sheet retreat and ice-stream dynamics, we argue that the subglacial sediment depocenter of the earlier two event beds was located in the lower Laurentian Channel while that of the later three events was upstream from Cabot Strait.
Summary(Plain Language Summary, not published)
This study identifies the changing sources of very thick mud deposits in deep water off Nova Scotia. The rapid deposition of these beds makes them particularly susceptible to submarine landsliding.

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