CGRG Bibliography of Canadian Geomorphology
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Author : Duk-Rodkin, A.; and Huntley, D.
Date : 2006.
Title : Quaternary geology and glacial limits of southern Mackenzie Mountains and Foothills.
Publication : Joint Annual Meeting of the Geological Association of Canada and the Mineralogical Association of Canada. University of Quebec in Montreal (UQAM) May 14-17, 2006.
Issue :
Page(s) :
Abstract
The Southern Mackenzie region has a complex glacial history. The region was glaciated by two ice masses from two different sources the mountains to the West and the plains to the East. Stratigraphic and geomorphologic evidence indicate that the two glaciers occupied this region at a slightly different time during the Late Pleistocene. The eastern continental ice sheet (Laurentide) advanced over the foothills and up major valleys before montane valley glaciers reach their maximum or during their initial stages of development ca. 30 ka. This pattern of glaciation is the same one that affected central and Northern Mackenzie Mountains in the Late Pleistocene. However, while areas north of the 64th parallel have an excellent geomorphic and pre-Late Pleistocene stratigraphic glacial record the southern areas have an excellent geomorphic and stratigraphic Late Pleistocene record. No old glaciation record has been found except in old glacial circs developed in the outer ranges filled with Late Pleistocene Laurentide sediments. The two ice masses caused major changes to the landscape of Southern Mackenzie region. The Laurentide Ice Sheet blocked the drainage of South Nahanni River causing the formation of a glacial lake that inundating approximate maximum area of 6000 km2 with an outlet to Yukon and Pacific Ocean. Preliminary recorded thickness of lacustrine sediments at various sites reveal about 120 metres at Virginia Falls. The ice sheet reached Virginia Falls and lower Flat River. Shield granite erratics were found over 100 km behind the foothills. During the continental ice sheet retreat and montane ice advance glacial Lake Nahanni cut an outlet to the East at First Canyon. This outlet joined the north flowing drainage that reached the Arctic Ocean. Another example of a major changed was the damming of Redstone River. This occurred ca 22 ka BP causing the Eastern flowing river to change its course northward. The channel incised through folded and faulted terrain triggering landsliding that continue today. Stratigraphic record of the region show glacial lacustrine and deltaic sediments formed pre advancing Laurentide Ice Sheet deposited over pre-Late Pleistocene east flowing fluvial deposits containing organic rich overbank deposits. This is followed by westward and northward Laurentide tillites overlapped by lacustrine sediments and another Laurentide till recording a readvance. This was followed by a local montane till devoid of shield erratics that extended as piedmont glaciers over Laurentide sediments. This was covered in turn by lacustrine and deltaic sediments of glacial Lake Mackenzie.
Bibliography of Canadian Geomorphology