The Last Cordilleran Ice Sheet in Southern Yukon Territory
The Cordilleran Ice Sheet in Yukon radiated from ice-divides in the Selwyn, PeIIy1 Cassiar, and eastern Coast Mountains and was contiguous with a piedmond glacier complex from the St. Elias Mountains. Expansion of glaciers in divide areas could have been underway by 29 ka BP but these did not merge...
| Published in: | Géographie physique et Quaternaire |
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| Main Authors: | , , , |
| Format: | Text |
| Language: | English |
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Les Presses de l'Université de Montréal
1991
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| Subjects: | |
| Online Access: | http://id.erudit.org/iderudit/032880ar https://doi.org/10.7202/032880ar |
| Summary: | The Cordilleran Ice Sheet in Yukon radiated from ice-divides in the Selwyn, PeIIy1 Cassiar, and eastern Coast Mountains and was contiguous with a piedmond glacier complex from the St. Elias Mountains. Expansion of glaciers in divide areas could have been underway by 29 ka BP but these did not merge to form the ice sheet until after 24 ka BP. The firn line fell to approximately 1500 m at the climax of McConnell Glaciation. Flow within the ice sheet was more analogous to a complex of merged valley glaciers than to that of extant ice sheets: topographic relief was typically equal to or exceeded ice thickness, and strongly influenced ice flow. Surface gradients on the ice sheet were fractions of a degree. Steeper ice-surface gradients occurred locally along the digitate ice margin. Retreat from the terminal moraine was initially gradual as indicated by recessional moraines within a few tens of kilometres of the terminal moraine. Small magnitude readvances occurred locally. The ice sheet eventually disappeared through regional stagnation and downwasting in response to a rise in the firn line to above the surface of the ice sheet. Regional déglaciation was complete prior to approximately 10 ka BP. L'Inlandsis de la Cordillère a progressé dans le Yukon à partir des lignes de partage des glaces des monts Selwyn, PeIIy et Cassiar et de l'est de la chaîne Côtière; il était contigu à un glacier de piémont complexe en provenance des monts St. Elias. Les glaciers ont pu se développer dans les régions de partage des glaces à partir de 29 ka BP, mais ils ne se sont fusionnés pour former un inlandsis qu'à partir de 24 ka BP. À l'optimum de la Glaciation de McConnell, la ligne de névé s'est abaissée à environ 1500 m. L'écoulement à l'intérieur de l'inlandsis ressemblait davantage à celui d'un complexe de glaciers de vallées coalescents qu'à celui des inlandsis actuels: le relief rejoignait l'épaisseur de glace ou la dépassait et influençait grandement l'écoulement glaciaire. Sur l'inlandsis, les gradients du profil ... |
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