Recognizing order in chaotic sequences of Quaternary sediments in the Canadian Cordillera
Episodic growth and decay of the Cordilleran ice sheet during the Pleistocene has imposed order on Quaternary stratigraphies in British Columbia and southern Yukon Territory. Although Quaternary deposits in this region are inherently complex, thick valley and lowland "lls consist of discrete pa...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.571.8870 http://www.sfu.ca/~jvenditt/geog213/readings/Clague_Quaternary_sediments_2000.pdf |
| Summary: | Episodic growth and decay of the Cordilleran ice sheet during the Pleistocene has imposed order on Quaternary stratigraphies in British Columbia and southern Yukon Territory. Although Quaternary deposits in this region are inherently complex, thick valley and lowland "lls consist of discrete packages of glacial sediments separated by unconformities or by generally thin, patchy interglacial deposits. Some unconformities de"ne former valley and lowland landscapes of similar relief to the present. Each package of glacial sediments displays stratigraphic order: distinctive #uvial and lacustrine units, deposited during the early stage of a glaciation and later overridden and eroded by glaciers, are overlain by retreat phase and interglacial #uvial, lacustrine, and marine sediments. Packages of glacial sediments contain one or more unconformities produced by glacial erosion; commonly the unconformities are better stratigraphic markers than tills, which are not always present, especially in valleys. The Quaternary stratigraphic record in the Canadian Cordillera becomes less complete with age, owing to repeated erosion during both interglaciations and glaciations. The most complete glacial sequence is the youngest, deposited during the late Wisconsin Fraser Glaciation. Deposits of the penultimate glaciation are common but generally incomplete. Only sporadic remnants of older, apparently Middle and Early Pleistocene glacial deposits are present in the Cordillera. ( 2000 Elsevier Science Ltd and INQUA. All rights reserved. |
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