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TitleBedrock erosional features and landforms, Cantley, Quebec: GAC-MAC field trip, May 28, 2011
DownloadDownloads
AuthorSharpe, D R
SourceGeological Survey of Canada, Open File 6979, 2017, 15 pages, https://doi.org/10.4095/300689
Year2017
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
ProvinceQuebec; Ontario
NTS31G/05; 31G/12
AreaCantley; Gatineau; Ottawa
Lat/Long WENS -76.0000 -75.5000 45.7500 45.2500
Subjectssurficial geology/geomorphology; general geology; glaciation; ice sheets; erosion; glacial erosion; glaciofluvial features; meltwater channels; erosional features; abrasion; glacial striations; glacial scours; potholes; landforms; glacial features; glacial deposits; solution; solution collapse; precipitates; carbonates; models; depositional environment; subglacial environment; ice detachment; ice reattachment; corrasion; cavitation; obstacle marks; ichelwannen; rat-tails; cavettos; Phanerozoic; Cenozoic; Quaternary
Illustrationsphotographs; location maps; geoscientific sketch maps; models
ProgramAquifer Assessment & support to mapping, Groundwater Geoscience
Released2017 06 13
AbstractSeveral erosional forms on bedrock at Cantley, Quebec, differ from well-known glacial abrasion forms. The forms consist of obstacle marks, hollows, depressions, and channels, which are defined by sharp rims, smooth inner surfaces, divergent flow features, and remnant ridges. These forms are found on lee, lateral, and overhung rock surfaces. This assemblage of features is best explained by differential erosion produced by separation eddies along lines of flow reattachment. Rapid, sediment-laden, turbulent, subglacial melt-water flows likely produced the forms by corrasion and cavitation erosion.
Ice-abrasion forms, such as striations, and such plucked forms as gouges and crescentic fractures are also present at the Cantley site. Pitted forms, polishing, and carbonate precipitate are also found. The occurrence of abrasion, pitting, polishing, and lee-side carbonate precipitate with meltwater forms suggests that the meltwater flows were subglacial. Decoupling of abrading ice from its bed temporarily suspended glacial abrasion, whereas reattachment of ice to the bed may have led to the rounding of sharp edges and the production of striations superposed on the glaciofluvial forms.
The association of forms produced both by glaciofluvial erosion and ice abrasion suggests that the glacier was alternately lifted from, and reattached to, the bed during periodic subglacial floods. These floods may have affected the dynamics of the ice sheet, and depositional sequences related to high-energy meltwater outbursts probably were laid down in adjacent basins.
Summary(Plain Language Summary, not published)
Several erosional forms on bedrock at Cantley, Quebec, differ from well-known glacial erosion forms. The forms mainly consist of hollows, depressions, and channels, which are interpreted to have been produced by rapid, sediment-laden, turbulent, melt-water flows under the glacier. The meltwater erosion forms are different, yet complementary to classic erosion forms such as striations that are also present at the site.
The association of forms produced both by glaciofluvial erosion and ice abrasion suggests that the glacier was alternately lifted from, and reattached to, the bed during periodic subglacial floods. The action of such large meltwater floods on the downaflow landscape helps map and estimate the location, size and properties of aquifers across southern Ontario.
GEOSCAN ID300689