| Titre | Submarine permafrost dynamics along the Arctic shelf edge |
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| Auteur | Paull, C K; Dallimore, S ; Jin, Y K; Caress, D W; Lundsten, E M; Anderson, K; Gwiazda, R; Riedel, M; Melling, H; Duchesne, M J; King, E L |
| Source | American Geophysical Union, Fall Meeting 2019, abstracts; EP11B-01, 2019 p. 1  Accès ouvert |
| Liens | Online - En ligne
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| Image |  |
| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200368 |
| Éditeur | American Geophysical Union |
| Réunion | American Geophysical Union Fall Meeting 2019; San Francisco, CA; US; décembre 9-13, 2019 |
| Document | site Web |
| Lang. | anglais |
| Media | en ligne; numérique |
| Formats | html; pdf |
| Province | Territoires du Nord-Ouest; Région extracotière du nord |
| SNRC | 107; 117 |
| Région | Mer de Beaufort; Tuktoyaktuk Peninsula |
| Lat/Long OENS | -140.0000 -130.0000 72.0000 68.0000 |
| Sujets | pergélisol; glace fossile; marges continentales; plate-forme continentale; talus continental; sédiments marins; carottes de sédiment marin; structures sédimentaires; analyses thermiques; regimes
thermiques; échantillons d'eau interstitielle; géochimie de l'eau de mer; salinités du fond océanique; températures du fond océanique; caractéristiques périglaciaires; pingos; levés géophysiques; bathymétrie; topographie du fond océanique; méthane;
sulfates; carbonates; dégagements gazeux; salinité; effets cumulatifs; géologie marine; géologie des dépôts meubles/géomorphologie; sédimentologie; géochimie; Nature et environnement; Sciences et technologie; Phanérozoïque; Cénozoïque;
Quaternaire |
| Programme | Géoscience pour la sécurité publique Évaluation des géorisques terrestres et marins |
| Diffusé | 2019 12 01 |
| Résumé | (disponible en anglais seulement)
Exploration in the Canadian Beaufort Sea, offshore of the Tuktoyaktuk Peninsula, has revealed a remarkable a zone of rugose morphology at the shelf edge and
upper slope. This morphology is especially common in 100 to 200 m water depths where seafloor features include topographic mounds, pockmarks, slope parallel ridges, and slide scars. This area occurs at the seaward edge of a sub-sea ~600 m thick
relict permafrost zone and geothermal modelling suggests that the lower 100 m of the permafrost zone has decomposed during the Holocene. Sediment cores show escaping brackish waters with pore water chloride content indicating widespread down core
freshening, especially near the shelf edge on the upper slope. Bottom waters corresponding with this band have a mean annual temperature of less than -1.4°C, cold enough to freeze escaping brackish pore waters. Positive relief mound features are up
to 10 m high circular to oval shaped and ~50 m in diameter, occurring at a density of ~6 per km2. Pore and lense ice has been observed in sediment cores and we interpret these features as offshore pingos. Intermixed are circular topographic
depressions up to 20 m deep. Detailed investigations utilizing a mapping Autonomous Underwater Vehicle (AUV) to provide 1-m grid bathymetric and Chirp profiles, and Remotely Operated Vehicle observations, were made to provide insights as to the
origin and age of these features. AUV surveys of one 8 km2 area first conducted in 2013 were repeated in 2017. Repeat mapping shows significant changes within this 4-year period. Multiple circular or elongated depressions have developed which are up
to 10 m deep and 100 m long. A corresponding volume of newly accreted material around the depressions equal to the missing volume was not detected. No evidence for high methane concentrations were found within this survey area as pore waters sulfate
gradients indicate the sulfate-methane transition zone is >8 m below seafloor in most sediment cores and no chemosynthetic seep fauna or authigenic carbonates were seen. We attribute the concentrated band of features to be related to the on-going
degradation of relict permafrost, the expulsion of brackish waters, and formation of ground ice within the near seafloor sediments. These observations have significant geohazard implications, which may be characteristic of Arctic settings. |
| Sommaire | (Résumé en langage clair et simple, non publié)
L'article présente un modèle géologique pour tenir compte des terrains de plancher de mer perturbées lors de la transition entre la plate-forme
de Beaufort et la partie supérieure de la pente. La recherche a été effectuée dans le cadre de la SST Mer de Beaufort géorisques au sein du SSE d'activité de la sécurité publique programme géoscientifique. La recherche porte surtout pour faire
progresser la compréhension de l'environnement géologique et dans ce contexte l'unique propriétés des sédiments qui influencent certains risques géologiques, tels que marine plancher océanique, de soulèvement de règlement et vers le bas de la pente
des mouvements. |
| GEOSCAN ID | 327138 |
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