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TitleIce-flow history and glacial transport in the Bonaparte lake map area of south central British Columbia
AuthorPlouffe, AORCID logo; Bednarski, J M; Huscroft, C A; McCuaig, S J
SourceCANQUA-CGRG Biennial Meeting, abstracts volume; 2009 p. 141
Alt SeriesEarth Sciences Sector, Contribution Series 20080728
MeetingCANQUA-CGRG Biennial Meeting; Burnaby, BC; CA; May 3-8, 2009
ProvinceBritish Columbia
AreaBonaparte Lake
Lat/Long WENS-122.0000 -120.0000 52.0000 51.0000
Subjectssurficial geology/geomorphology; glacial deposits; glacial landforms; glacial features; ice flow; ice transport directions; glacial history; tills; till analyses; glaciation; glacial history; Cenozoic; Quaternary
ProgramMountain Pine Beetle
Released2009 01 01
AbstractThe Bonaparte Lake map area lies within the Interior Plateau of south central British Columbia and is within the zone severely impacted by mountain pine beetle infestation. To diversify the severely impacted natural resource economy of this region, a regional till sampling and surficial geology mapping project has been implemented by the Geological Survey of Canada as part of the Mountain Pine Beetle Program of Natural Resources Canada. The objective of this activity is to evaluate the mineral potential of the area which is characterized by a nearly continuous and thick cover of glacial sediments.

During the 2007 and 2008 field seasons, till sampling was completed over a large sector of the Bonaparte Lake map area (NTS 92P). Till samples (2-3 kg) were collected for geochemical analyses at a spacing of 2-3 km along forestry roads. A few glaciofluvial sediment samples were collected where till was unavailable. Large bulk till samples (15 to 30 kg), for heavy mineral study, were taken on average at every second sample site, except in regions of high mineral potential where they were collected at every site. In addition to sampling, glacial striations were measured on bedrock outcrops to record changing ice-flow directions and to provide new insights into the ice-flow history of the area.

At the onset of glaciation, ice accumulated over the Cariboo Mountains and advanced towards the west and southwest over the Bonaparte Lake map area at least as far west as Loon Lake, Green Lake, and Lac la Hache. As the glaciation intensified, ice accumulated over the Interior Plateau, and a linear east-west trending ice divide developed north of the Bonaparte Lake map area resulting in general south-eastward, southward, and south-westward ice movements. The net effect of these two phases of ice flow is that glacial transport within the Bonaparte Lake region generally results from two vectors: the first one to the west and southwest, and a second one to the southeast, south or southwest. This new interpretation of the ice-flow history refines the glaciation model of central British Columbia originally proposed by H.W. Tipper which was largely based on the interpretation of macro-landforms (e.g. drumlins, flutings, crag-and-tail features) observed on aerial photographs.

These two phases of ice flow are well reflected by glacial transport. Evidence of westward transport (first phase) include a high percentage of granitic pebbles in till and abundant large granitic boulders at surface west of the Takomkane Batholith. Furthermore, high thorianite grain counts (ThO2) in the heavy mineral concentrates of till west and southwest of the Thuya Batholith are interpreted to result from the first westward ice movement. The second southward ice movement is reflected with high percentage of granitic pebbles in till south of the Raft and Thuya batholiths. This new interpretation of the ice-flow history and glacial transport will have important implication for mineral tracing in this region of high mineral potential. Indeed, high gold grain counts in some of the till samples still have unknown bedrock source and will be trace using these ice flow vectors.

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