| Title | Elements of surficial geology and glacial history of the Bonaparte Lake map area |
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| Author | Bednarski, J; Plouffe, A ; Huscroft, C A; McCuaig, S J |
| Source | CANQUA-CGRG Biennial Meeting, programme and abstracts volume; 2009 p. 38  Open Access |
| Links | Online - En ligne
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| Image |  |
| Year | 2009 |
| Alt Series | Earth Sciences Sector, Contribution Series 20090206 |
| Meeting | CANQUA - CGRG Biennial Meeting; Burnaby; CA; May 3-8, 2009 |
| Document | book |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia |
| NTS | 92P |
| Area | Bonaparte Lake |
| Lat/Long WENS | -122.0000 -120.0000 52.0000 51.0000 |
| Subjects | surficial geology/geomorphology; glacial deposits; glacial history; glacial landforms; glaciation; tills; ice flow; ice movement directions; Fraser Glaciation |
| Program | Mountain Pine Beetle |
| Abstract | Eleven 1:50 000 scale surficial geology maps covering the eastern part of the Bonaparte Lake map area (NTS 92P) were recently mapped by the Geological Survey of Canada as part of the Mountain Pine
Beetle Program. The surficial geology of this area is largely determined by the growth and subsequent waning of the Cordilleran Ice Sheet, which advanced from dispersal centres outside the study area in the Coast Mountains and Cariboo Mountains. Most
of the study area is a rolling plateau lying about 1200 m above sea level, which gradually rises to the east and is more rugged, culminating to over 2000 m in the Sushwap Highlands. The bedrock is very diverse with Mesozoic granitic rocks intruding
into sedimentary and volcanic formations of Mesozoic and Paleozoic age. In general, the eastward increase in ruggedness coincides with underlying batholiths and deformed miogeoclinal rocks. Much of the western part in the study area is covered by
Tertiary lavas, which are flat lying or gently dipping and obscure the older rocks. In general concordant uplands and plateaus are thought to be a Tertiary erosional surface that has been dissected by subsequent glaciation and fluvial incision. A
south-trending valley occupied by the North Thompson and Clearwater rivers provides maximum relief along the eastern edge of the mapped area. Stratigraphy in a number of the valleys shows significant deposition of glaciofluvial sand and gravel, and
more limited glaciolacustrine sand, which was deposited at the onset of the last glaciation, which culminated about 18 ka BP (Fraser Glaciation). Consequently, some large valley systems were in existence prior to the last glaciation. Extensive
glacial modification took place as most of the ridges in the area are rounded and bear evidence of glacial erosion. Till cover is usually thicker in the west and in valleys where it forms continuous blankets. Ice-flow features and till provenance in
the Bonaparte Lake area shows that glaciers originally flowed from the east off Cariboo/Columbia Mountains. This advance was subsequently deflected to the south by ice originating from the Coast Mountains west of the study area. At the height of the
Fraser Glaciation, coalescent ice over the Bonaparte Lake area flowed to the SSE from what must have been an ice divide immediately north of the study area over the Fraser Plateau. This ice divide likely bridged the main ice divides over the Coast
Mountains to the west and the Columbia Mountains to the east. As the ice thinned, the local topography imparted a greater influence on ice flow, especially evident is a strong southward ice flow down the North Thompson valley. As the plateau became
ice free, it was dissected by several large meltwater systems issuing from the retreating ice margins and extensive glaciofluvial sediments were deposited. Most of the large drainage systems drained westward into the Fraser River drainage, but some
meltwater systems also drained eastward into the North Thompson River valley when it became ice free. |
| GEOSCAN ID | 247884 |
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