| Titre | Recurrence of turbidity currents on a glaciated continental margins: a conceptual model from eastern Canada |
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| Auteur | Normandeau, A ;
Campbell, D C |
| Source | Journal of Sedimentary Research vol. 90, no. 10, 2020 p. 1305-1321, https://doi.org/10.2110/jsr.2020.66 |
| Image |  |
| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190551 |
| Éditeur | Society for Sedimentary Geology |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.2110/jsr.2020.66 |
| Media | en ligne; numérique |
| Formats | pdf; html |
| Province | Région extracotière de l'est; Nouvelle-Écosse; Terre-Neuve-et-Labrador |
| SNRC | 10 |
| Région | Océan Atlantique; The Gully; Shortland Canyon; Haldimand Canyon; Mohican Channel; Verril Canyon; Dawson Canyon; Bonnecamp Canyon; Logan Canyon |
| Lat/Long OENS | -60.0000 -55.5000 44.5000 41.0000 |
| Sujets | modèles; courants de turbidite; sédiments marins; dépôts glaciaires; dépôts glaciaires; transport des sediments; caractéristiques sous-marines; canyons sous-marins; marges continentales; plate-forme
continentale; talus continental; antecedents glaciaires; glaciation; nappes glaciaires; déglaciation; retrait de la glace; changements du niveau de la mer; levés géophysiques; levés acoustiques marins; sonar latéral; bathymétrie; carottes de sédiment
marin; turbidites; chronostratigraphie; antecedents de sedimentation; distribution des sédiments; glissements de terrain; dépôts de glissement de terrain; configurations lit; morphologie; débit de sedimentation; Calotte glaciaire Laurentide;
Infrastructure; sédiments glaciomarins; sédiments fluvioglaciaires; dépôts de versants; géologie marine; géologie des dépôts meubles/géomorphologie; sédimentologie; stratigraphie; géophysique; Nature et environnement; Sciences et technologie;
Phanérozoïque; Cénozoïque; Quaternaire |
| Illustrations | cartes de localisation; séries chronologiques; cartes géolscientiques généralisées; tableaux; profils géophysiques; photographies; images géophysiques; coupes lithologiques; diagraphies
géophysiques; profils; graphique à barres; modèles 3D |
| Programme | Géosciences marines pour la planification spatiale marine |
| Diffusé | 2020 11 30 |
| Résumé | (disponible en anglais seulement)
Turbidity currents in submarine canyons transport large volumes of sediment and carbon to the deep sea and are known to present a major risk to submarine
infrastructure. Understanding the origin, the triggers, the recurrence, and the timing of these events is important for predicting future events and mitigating their impact. Depending on the morphological and latitudinal setting of submarine canyons,
different external controls will govern the recurrence of turbidity currents. Here, we assess the recurrence of turbidity currents in shelf-incising submarine canyons off eastern Canada in order to examine the effects of external forcings such as
glacier retreat and sea level on the deep-water sedimentary record. We used multibeam bathymetry, sub-bottom profiles, and the analysis of turbidites in sediment cores to infer the triggers of turbidity currents over time and propose a conceptual
model for the activity of turbidity currents during glacial retreat. The chronostratigraphy of turbidites shows that turbidity current activity in the glaciated The Gully submarine canyon (eastern Canada) was highest between 24 ka cal BP (LGM) and 17
ka cal BP, with > 100 turbidites per 1,000 yr, when the ice sheet was directly delivering sediment to submarine canyons. As the ice margin retreated, the dominant sediment supply switched to glaciofluvial and then to longshore drift, while RSL
remained low. The recurrence of turbidity currents nonetheless decreased drastically to < 10 per 1000 yr during that time, pre-dating the rise in RSL. This timing suggests that the reduction of turbidity-current activity is closely linked to
retreating glaciers rather than to sea-level rise, which occurred later. Following the retreat of the ice sheet, sea level rose progressively to drown the shallow banks on the continental shelf, and turbidity currents ceased being active after 13 ka
cal BP. In the late Holocene, landslide and concomitant turbidity-current recurrence increased to 1 per 1,000 yrs, with at least four new events recorded in deep water. This study shows that glacial sediment supply and sea level controlled the type
of sediment supply to the continental slope, which in turn controlled the triggers of turbidity currents over time and the flushing of sediment to the deep water. By comparing with other glaciated margins, we propose a conceptual model explaining the
recurrence of turbidity currents, taking into account RSL change and the position of the ice margin relative to the shelf edge. This conceptual model can help predict turbidity-current activity and offshore geohazards on other ancient and modern
glaciated continental margins. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Nous avons évalué la récurrence des courants de turbidité dans les canyons sous-marins au large de l'est du Canada afin d'examiner les effets de
forçages externes tels que le retrait des glaciers et la hausse du niveau de la mer sur l'enregistrement sédimentaire. Nous proposons un modèle conceptuel expliquant la récurrence des courants de turbidité en tenant compte du niveau marin relatif et
de la position de la marge glaciaire par rapport au rebord du plateau continental. |
| GEOSCAN ID | 321867 |
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