|Titre||Marine evidence for a glacial ice stream in Amundsen Gulf, Canadian Arctic Archipelago|
|Auteur||MacLean, B; Blasco, S; Bennett, R; Lakeman, T; Hughes-Clarke, J; Kuus, P; Patton, E|
|Source||42nd International Arctic Workshop, program and abstracts; par Institute of Arctic and Alpine Research (INSTAAR); 2012 p. 51-52|
|Liens||Program & Abstracts online |
|Séries alt.||Secteur des sciences de la Terre, Contribution externe 20110348|
|Réunion||42nd International Arctic Workshop; Winter Park, Colorado; US; mars 7-9, 2012|
|Media||papier; en ligne; numérique|
|Province||Région extracotière du nord|
|SNRC||76M; 76N; 77B; 86P; 86O; 87A; 87C; 87D; 97C; 97D; 97E; 97F; 97G; 97H|
|Lat/Long OENS||-128.0000 -108.0000 72.0000 67.5000|
|Sujets||rainures glaciaires; elements glaciaires; moraines; déglaciation; directions des mouvements de la glace; géologie des dépôts meubles/géomorphologie; géologie marine; Quaternaire|
|Programme||Géoscience marine pour le développement économique de l'Arctique, Géoscience en mer|
|Résumé||(disponible en anglais seulement)|
The study area lies at the southwestern end of the Northwest Passage adjacent to the Beaufort Sea. It comprises Amundsen Gulf, Dolphin and Union Strait and
Coronation Gulf. High resolution multibeam sonar imagery and sub-bottom profiles of the seabed have been acquired by ArcticNet and Ocean Mapping Group, University of New Brunswick on transits through these waterways for the past decade. Studies of
these data revealed a variety of seabed features including glacial sole marks or flutings, drumlins, a moraine, ice-contact strata, current scours, iceberg scours, bedrock outcrops and discontinuous sediment deposits of variable thickness.
presence of glacial ice streams in channels of the Canadian Arctic Archipelago was postulated by earlier workers based on various parameters including regional morphologies (Denton and Hughes, 1981), satellite imagery (Clark and Stokes, 2001; Stokes
et al., 2005), satellite imagery and limited marine data (Stokes et al., 2006; Des Angelis and Kleman, 2007) and from marine data (MacLean et al., 2010). A glacial ice stream in Amundsen Gulf was interpreted by Stokes et al. (2006) from a study of
satellite imagery and limited marine data.
The pattern of sole marks or glacial flutings on the seabed in Amundsen Gulf now evident from extensive multibeam imagery, and ice flow patterns identified on the adjacent mainland and islands by Dyke
and Prest (1987), Sharpe (1992) and Kerr (1994) confirm that an ice stream of the Laurentide Ice Sheet occupied Amundsen Gulf, Coronation Gulf, Dolphin and Union Strait and parts of the adjacent terrestrial areas during the Last Glacial Maximum,
26,500-19,000 calibrated years BP. Part of the northwestward-flowing ice stream was deflected around the Colville Mountains on Victoria Island and rejoined the main ice stream in Amundsen Gulf by way of Prince Albert Sound. . The grounded ice
stream extended northwestward to the margin of the inner shelf in the Beaufort Sea at a depth of 450 m. Retreat from that maximum position began prior to 13,000 cal yr BP (Scott et al., 2009).
The bathymetry of Amundsen Gulf and known extent of
the ice stream on land indicates the ice was at least 700 m thick in the gulf. Thick, multi-sequence deposits of ice-contact sediments in the northwestern part of Amundsen Gulf suggest that a number of ice retreats and re-advances occurred in that
region. A series of moraines at the northwestern end of the gulf mark temporary positions of the ice stream front during final retreat. Early stages of ice retreat may have been associated with meltwater discharge under the ice stream as evidenced by
current erosion associated with some of the sole marks or glacial flutings. Melting at the leading edge of the ice stream resulted in calving of icebergs and the generation of keel-scour marks in the seabed. Retreat of the ice was relatively rapid as
indicated by generally sparse deglacial glaciomarine sediment in Amundsen Gulf. Based on terrestrial radiocarbon dates the retreating ice front had reached eastern Amundsen Gulf by about 12,000 cal yr BP (10.7 14C ka BP, Sharpe 1992; Kerr, 1994,
A later ice re-advance trending to the west and west-southwest formed extensive drumlin fields on southern Victoria Island (Sharpe, 1992; Stokes et al. (2006). This event is also evident in northwestern Coronation Gulf, in Dolphin and Union
Strait, and on the adjacent mainland where those trends are superimposed on the earlier northwesterly ice flow features (St-Onge and McMartin, 1987). The lack of Holocene sediments draping the sole marks or flutings, and outcrops of exposed bedrock
and glaciomarine sediment indicates very low sedimentation rates in most areas of Amundsen Gulf since ice retreat.