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TitleConverging ice streams: a failed hypothesis for deposition of the Oak Ridges Moraine
AuthorSharpe, D RORCID logo; Russell, H A JORCID logo; Pugin, A J -M
SourceCANQUA-AMQUA Ottawa 2018, Joint Meeting of the Canadian and American Quaternary Associations, Crossing Borders in the Quaternary, program; 2018 p. 85
LinksOnline - En ligne (complete volume - volume complet, pdf, 11.5 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20180299
MeetingCANQUA-AMQUA 2018: Joint meeting of the Canadian and American Quaternary Associations; Ottawa, ON; CA; August 7-11, 2018
Mediapaper; on-line; digital
File formatpdf
NTS30M/13; 30M/14; 31D/01; 31D/02; 31D/04; 31D/05; 31D/08; 31G/05; 40P/16
Subjectssurficial geology/geomorphology; stratigraphy; glacial history; glaciation; ice flow; depositional history; depositional environment; glacial deposits; moraines; glacial landforms; eskers; glacial features; meltwater channels; Oak Ridges Moraine; Halton Till; ice-flow directions; ice streams; spillways; glaciofluvial sediments; glaciolacustrine sediments; Phanerozoic; Cenozoic; Quaternary
ProgramGroundwater Geoscience Aquifer Assessment & support to mapping
Released2018 08 01
AbstractThe hypothesis that the Oak Ridges Moraine (ORM) formed between two converging (roughly NS) ice streams is tested based on readily available, high-resolution field data. These data include DEMs, geological mapping, shallow reflection seismic profiles, continuous core, and analysis of sediment type, architecture, and paleoflow. Combined these data refute the converging ice stream hypothesis for deposition of the ORM. Streamlined landforms, which are used to re-construct ice stream flow paths, are defined by surface mapping, seismic profiles and cored boreholes to trend beneath ORM; they illustrate that the streamlining event is older and has no direct bearing on the formation of ORM. Meltwater channels that truncate the streamlined landforms (linked to the ORM ice stream hypothesis) are inferred to represent (sub-aerial) spillways, which end at the north side of ORM. These NS meltwater channels truncate the streamlined forms and they also trend beneath ORM; they have eskers on their floors, and thus, are subglacial and not sub-aerial channels. Halton Till, the inferred southern, ice-stream bed, is not present in the areas of the predicted ice-stream flow path. Halton Till occurs in transition from ORM glaciofluvial sediment, and comprises interbedded diamicton and glaciolacustrine sediment, not the predicted ice-stream, deforming-bed sediment facies. ORM glaciofluvial to glaciolacustrine sediment has a clear east to west paleoflow in conflict with the ~NS sediment flux required by the converging ice stream hypothesis. In summary, the proposed ice stream hypothesis fails to explain the field data related to deposition of 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.

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