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TitleRegional subglacial quarrying and abrasion belowhard-bedded palaeo-ice streams crossing the Shield-Palaeozoic boundary of central Canada: the importance of substrate control
AuthorBukhari, SORCID logo; Eyles, N; Sookhan, S; Mulligan, RORCID logo; Paulen, RORCID logo; Krabbendam, M; Putkinen, N
SourceBoreas 2021 p. 1-25, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200742
Mediapaper; on-line; digital
File formatpdf; html
NTS30M/13; 30M/14; 30M/15; 30M/16; 30N/13; 30N/14; 30N/15; 31C; 31D; 31E/01; 31E/02; 31E/03; 31E/04; 31F/01; 31F/02; 31F/03; 31F/04
AreaLake Ontario; Kingston; Peterborough; Barrie; Picton; Lake Simcoe; Kawartha Lakes
Lat/Long WENS -80.0000 -76.0000 45.2500 43.7500
Subjectssurficial geology/geomorphology; geophysics; Nature and Environment; Science and Technology; glacial history; Wisconsinian glacial stage; glaciation; ice flow; glacial erosion; abrasion; bedrock geology; basement geology; lithology; sedimentary rocks; limestones; igneous rocks; metamorphic rocks; geophysical surveys; models; modelling; clasts; glacial deposits; glacial features; glacial landforms; moraines, hummocky; drumlins; drumlinoids; glacial grooves; glacial scours; escarpments; Canadian Shield; St. Lawrence Lowlands; Dummer Moraine; Laurentide Ice Sheet; Simcoe Ice Stream; Ontario Ice Stream; Glacial Lake Iroquois; Rochester Basin; Ontario Basin; Oak Ridges Moraine; ice streams; ice-flow directions; Phanerozoic; Cenozoic; Quaternary; Paleozoic; Precambrian
Illustrationsgeoscientific sketch maps; cross-sections; photographs; 3-D images
ProgramGEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Southern Mackenzie Surficial Mapping
Released2021 05 06
AbstractThree-dimensional surface visualization models derived from high-resolution LiDAR data provide new information about the type and scale of erosional processes below Late Wisconsin palaeo-ice streams traversing the boundary between Canadian Shield crystalline rocks with offlapping Palaeozoic limestones in central Ontario. The hard bed is directly analogous to that found below ice streams in East Antarctica and East Greenland and provides insight into the effects of abrupt changes in substrate type on subglacial processes. Erosion of hard crystalline Canadian Shield rock was largely ineffectual consisting of areal abrasion of rounded whalebacks and local lee side plucking. In contrast, fast flow over the strike of gently dipping well-bedded and jointed Palaeozoic limestones cut large flow-parallel grooves and ridges akin to mega-scale glacial lineations reflecting intense abrasion below narrow streams of subglacial debris dominated by hard crystalline Shield clasts (erodents). Regionally extensive plucking of structurally weak, well-jointed and bedded limestone produced large volumes of rubbly carbonate debris leaving a 25-km-wide belt of uncontrolled hummocky rubble terrain (long known as the Dummer Moraine in Southern Ontario) some 350 km long and locally as much as 10 m thick. Subglacial plucking and abrasion under fast flowing ice were highly effective in stripping limestone cover rocks from Precambrian basement, and over many glacial cycles, may have played a role in the location and excavation of numerous large and deep lake basins around the Shield-Palaeozoic boundary zone in North America.
Summary(Plain Language Summary, not published)
A collaborative effort by the University of Toronto, the Ontario Geological Survey, Geological Survey of Canada, British Geological Survey and Geological Survey of Finland to better understand the genesis of hummocky terrain at the margin of a 'hard' bedrock Shield, and the transition to softer Palaeozoic beds. This paper uses high-resolution LiDAR to map and examine the landforms.

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