GEOSCAN, résultats de la recherche


TitreAnatomy of the Kitimat fiord system, British Columbia
AuteurShaw, J; Stacey, C; Wu, Y; Lintern, G
SourceGeomorphology vol. 293, 2017 p. 108-129,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160108
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC103G; 103I/02; 103A/11; 103A/12; 103A/14; 103A/13
Lat/Long OENS-130.0000 -128.5000 54.0000 52.5000
Sujetsdeltas; topographie glaciaire; dépôts glaciaires; marges glaciaires; dépôts glaciomarins; fosses abyssales; caractéristiques sous-marines; moraines; transport des sediments; retrait de la glace; géologie marine; géologie des dépôts meubles/géomorphologie
Illustrationslocation maps; tables; digital elevation models; digital images
ProgrammeRisques géo marines, Géoscience pour la sécurité publique
Résumé(disponible en anglais seulement)
The geomorphic complexity of the Kitimat fiord system, on the active margin of British Columbia, Canada, is analyzed from four perspectives: 1) glacial landforms and sediments; 2) postglacial sedimentation; 3) Holocene fan deltas; and 4) submarine mass transport. Flow-parallel and flow-transverse glacial landforms show that grounded ice exiting the fiord system at the last glacial maximum streamed down Moresby Trough towards the Queen Charlotte trough mouth fan. After brief halts on the inner shelf, grounded ice margins cleared the fiord threshold perhaps by c. 13 ka 14C yr BP, and certainly before 12.1 ka 14C yr BP (13 ka Cal BP). In the fiords meltwater plumes deposited stratified glaciomarine sediments interbedded with debris flows. Temporary halts in retreat created substantial transverse moraines. A major hyperpycnal flow eroded the Kitkiata moraine and deposited an outburst mud deposit, perhaps sourced from an ice margin in the upper Skeena Valley. Postglacial sedimentation on fjord floors is spatially variable: drifts of mud > 90 m-thick corresponding with areas of low current velocity alternate with areas of non-deposition and erosion corresponding with areas of high velocity. Numerous minor rivers in the area created more than a hundred fan deltas whose size and morphology correlates with drainage basin size. While they can be classified in the Prior and Bornhold (1993) system, the numerically dominant small fan deltas (types 1 and 2) are unlikely to evolve into the larger types 3 and 4. Submarine mass transport was most frequent immediately following ice retreat (13¿10 ka 14C yr BP). The largest event (~1.2 km3) involved failure of glaciomarine sediment on a submarine moraine at Squally Channel, and consequent movement of material into the adjacent deep basin. This event occurred post-12.1 ka 14C yrs BP (13 ka Cal BP). In the postglacial phase, mass transport continued on a lesser scale up to the present day, most intensive in Kitimat Arm. From the perspective of glacial landforms, postglacial sedimentation and mass transport, this Pacific active margin fiord system has some parallels with fiord systems on Canada's east coast passive margin, and with Norwegian fiords, but the intensive development of Holocene fan deltas is strongly distinctive.
Résumé(Résumé en langage clair et simple, non publié)
Ce document résume la géologie marine de la côte du fjord du Pacifique qui a été étudié pour évaluer les géorisques marins.