La météorisation des grès des terrasses de Bug Creek, Territoires du Nord-Ouest, Canada.
The purpose of this study is to determine the origin of the sediments that lie on the treads of the cryoplanation terraces of the Richardson Mountains in the Northwest Territories, Canada. A series of 15 bore holes were done on the treads of the terraces, at the bottom of which organic material was...
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University of Ottawa (Canada)
2009
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| Online Access: | http://hdl.handle.net/10393/9136 http://dx.doi.org/10.20381/ruor-16164 |
| Summary: | The purpose of this study is to determine the origin of the sediments that lie on the treads of the cryoplanation terraces of the Richardson Mountains in the Northwest Territories, Canada. A series of 15 bore holes were done on the treads of the terraces, at the bottom of which organic material was found and dated by radiocarbon method. Petrographic, granulometric, exoscopic and geochemical analyses were done on the sandstone of the Aklavik Formation of the Bug Creek Group, on the surface sediments and on the core sediments. The objectives of these analyses were to compare the petrology of the local sandstone to the sediments found on the treads of the terraces, to determine the granulometric distribution of the sediments, to determine the scarp's rate of weathering and the chronology of the events that took place. The results show that the sediments are produced by disintegration of the local sandstone of the Aklavik Formation. The weathering of the rock causes an increase in the intergranular porosity and fractures in the grains of quartz. The weathering of the sandstone releases sands, silts and clay. This material constitutes a potential source of loess in glacial times. The accumulation of sediments that lie currently on the treads of the terraces which are derived from the weathering of the sandstone, could have begun to accumulate about 5397 +/- 84 BP or even earlier at about 9420 +/- 90 BP. A weathering rate of the rock scarp was calculated at about 20 mm/1000 years and would seem to indicate that the terraces could have started to develop in the Tertiary period. |
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