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TitleConverging ice streams: an unreasonable hypothesis for deposition of the Oak Ridges Moraine, southern Ontario
 
AuthorSharpe, D R; Russell, H A J; Pugin, A
SourceCanadian Journal of Earth Sciences vol. 57, no. 7, 2019 p. 781-800, https://doi.org/10.1139/cjes-2019-0021 Open Access logo Open Access
Image
Year2019
Alt SeriesNatural Resources Canada, Contribution Series 20180421
PublisherNRC Research Press
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProvinceOntario
NTS30M/13; 30M/14; 30M/15; 31D/02; 31D/03; 31D/04
AreaUxbridge; Aurora
Lat/Long WENS -79.6667 -78.6667 44.6667 43.6667
Lat/Long WENS -80.0000 -78.5000 44.2500 43.7500
Subjectssurficial geology/geomorphology; sedimentology; stratigraphy; Nature and Environment; Science and Technology; postglacial deposits; organic deposits; glacial deposits; glacial landforms; glacial features; moraines; tills; sands; muds; clays; silts; gravels; channel deposits; drumlins; eskers; meltwater channels; paleocurrents; paleocurrent directions; glacial lakes; sediments; glacial history; glaciation; Wisconsinian glacial stage; ice sheets; ice flow; depositional history; stratigraphic analyses; tunnel valleys; lineations; hydraulic gradients; deformation; stratification; geophysical surveys; seismic surveys; models; boreholes; grain size analyses; Oak Ridges Moraine; Rice Lake Wedge; Pontypool Wedge; Newmarket Till; Halton Till; Halton Ice Stream; Simcoe Ice Stream; Saginaw-Huron Ice Stream; ice streams; ice-flow directions; glaciofluvial sediments; glaciolacustrine sediments; diamicton; spillways; mega-scale glacial lineations; alluvial sediments; Phanerozoic; Cenozoic; Quaternary
Illustrationsdigital elevation models; geoscientific sketch maps; 3-D models; cross-sections, stratigraphic; tables; seismic profiles; lithologic sections; profiles; photographs; block diagrams
ProgramGroundwater Geoscience, Aquifer Assessment & support to mapping
Released2019 12 20
AbstractThe hypothesis that Oak Ridges Moraine (ORM) formed between converging ice streams requires critical testing. Available data (e.g., digital elevation models, maps, seismic profiles, continuous cores, and pit exposures) are inconsistent with the converging ice stream hypothesis. Combined analysis of landform and subsurface data permits testing the ORM area stratigraphic sequence and sedimentary origin. Stratigraphic data indicate that drumlinized Newmarket Till, incised by north- south-oriented (tunnel) valleys, extends beneath ORM. Thus, streamlining on Newmarket Till is older than ORM and has no direct bearing on its formation. The north-south-trending valleys truncate streamlined Newmarket Till, extend to bedrock, have inset eskers, and occur beneath ORM. Hence, these valleys are older than ORM and have a subglacial rather than a proglacial origin. Overlying the mega-scale lineations and incised channels are topographically elevated (>300ma.s.l.), ORM glaciofluvial- glaciolacustrine sequences. Its east to west paleoflow trend indicates an east-west-oriented hydraulic gradient, orthogonal to expected gradients of proposed north-south converging ice streams. The exclusive presence of ORM meltwater sediments, with rare deformation, is incompatible with a converging ice stream, deforming-bed hypothesis. Halton sediment grades upward from stratified sand (ORM) to interbedded diamicton and glaciolacustrine sediment, rather than deformation till. Halton sediment overlies ORM and consequently the proposed Halton ice streaming is younger than the moraine. Halton Till is present in few of the predicted ice stream areas, and where Halton Till is present, it has no mega-scale lineations. In sum, the weight of evidence unequivocally argues against a converging ice-stream process model for the ORM.
Summary(Plain Language Summary, not published)
This presentation makes the case that the ORM was not formed by fast flowing ice streams because the hypothesis does not conform with published field data on sediment type, geometry, composition and former flow directions. ORM formed from discharge of stored glacial meltwater at the end of the last glacial episode. Its sand and gravel composition makes it one of the most important groundwater resources in the Toronto region and in southern Ontario.
GEOSCAN ID313769

 
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