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TitleSediment density flow distribution on wave-influenced deltas
AuthorNormandeau, AORCID logo; Eamer, J; Bernatchez, P; Didier, D; Lajeunesse, P; Montero-Serrano, J C; Limoges, A
SourceSedimentology 2022 p. 1-42,
Alt SeriesNatural Resources Canada, Contribution Series 20220037
Mediapaper; digital; on-line
File formatpdf
SubjectsScience and Technology; Nature and Environment; sedimentology; deltas; turbidity currents; St. Lawrence Estuary
Illustrationsdiagrams; tables; photographs; satellite imagery
ProgramMarine Geoscience for Marine Spatial Planning
Released2022 08 19
AbstractDeltas are at the transition between fluvial and marine sedimentary environments where sediment density flows are often triggered during high river discharge events, forming submarine channels and sediment waves. On wave-influenced deltas, longshore currents are particularly efficient at transporting sediment alongshore, reducing the likelihood of sediment density flows from occurring at river mouths. This study describes four deltaic sedimentary systems at different stages of their evolution on a formerly glaciated continental inner shelf of eastern Canada in order to better understand the distribution of sediment density flows on wave-influenced deltas. Three types of settings are recognized as being prone to sediment density flows: (i) in the early stages of wave-influence and on large deltas, converging longshore currents can lead to offshelf sediment transport; (ii) on wave-influenced to wave-dominated deltas, a sandy spit can re-route the river mouth and sediment density flows form where the spit intersects the delta lip; (iii) in advanced stages of wave-dominated deltas and during their demise, rocky headlands are exposed and can intersect the slope, where off-shelf sediment transport occurs. These types of sediment density flows were all characterized by debris flows or surge-type turbidity currents which have limited offshore run-out. More rarely, hyperpycnal flows form at the river mouths, especially where the river incises glaciomarine clays prone to landsliding in the river, which increases fine-grained fluvial suspended sediment concentration. Overall, these results highlight the predominance of fluvial-dominated deltas during a phase of relative sea-level fall combined with high sediment supply. However, as soon as sediment supply diminishes, wave action remobilizes sediment alongshore modifying the distribution and types of sediment density flows occurring on wave-influenced deltas.
Summary(Plain Language Summary, not published)
This study examines the distribution of submarine avalanches on deltas where wave action dominates the remobilisation of sediment.

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