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TitleSearching for Ontario's 'missing' ice streams
 
AuthorMulligan, RORCID logo; Marich, A; Paulen, RORCID logo
SourceGAC®-MAC 2021, London, Canada: Exploring Geosciences Through Time and Space/GAC®-MAC 2021, London, Canada : Explorer les géosciences à travers le temps et l'espace; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 44, 2021 p. 230 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 2.45 MB)
Image
Year2021
Alt SeriesNatural Resources Canada, Contribution Series 20210299
PublisherGeological Association of Canada
MeetingGeological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2021; London, ON; CA; November 1-5, 2021
Documentserial
Lang.English
Mediadigital; on-line
File formatpdf
ProvinceOntario
NTS31B; 31C; 31D; 31E; 31F; 31G; 31K; 31L; 31M; 32D; 32E; 32L; 32M; 40; 41; 42; 43; 44D; 52; 53A; 53B; 53C; 53D; 53F; 53G; 53H; 53I; 53J; 53K; 53O; 53P; 54A; 54B
Lat/Long WENS -95.2500 -74.0000 57.0000 7.0833
Subjectssurficial geology/geomorphology; Nature and Environment; Science and Technology; glacial history; glaciation; ice flow; deglaciation; glacial erosion; sediment transport; sediment dispersal; depositional history; ice margins; glacial deposits; glacial landforms; glacial features; tills; moraines; lineations; glacial scours; proglacial lakes; modelling; climate effects; topography; bedforms; Laurentide Ice Sheet; Canadian Shield; ice streams; ice-flow directions; Digital elevation data; Phanerozoic; Cenozoic; Quaternary
ProgramGEM-GeoNorth: Geo-mapping for Energy and Minerals GEM Program Coordination
Released2021 11 01
AbstractThe advance and retreat of the Laurentide Ice Sheet (LIS) across Ontario extensively modified the landscape through erosion of bedrock and pre-existing sediment, and deposition of thick sediment sequences along the margins of ice lobes during deglaciation. The recent release of high-resolution (<2 m) LiDAR and other digital terrain data for large areas of Ontario enables improved mapping of glacial landforms at regional scales. Increasingly, over the last decade, the existence - and influence - of paleo-ice streams on the landscape has been recognized. Mega-scale glacial lineations (MSGL), a landform assemblage diagnostic of paleo-ice streams, can be difficult to identify from the ground, but are readily visible on these high resolution digital elevation model datasets and hold significant implications for paleoglaciological reconstructions. Developing an understanding of the onset, evolution, timing, and interactions between paleo-ice streams and their beds is critical to understanding ice sheet evolution and provides important constraint to models of ice sheet response to climate changes. As glacial morphotypes, MSGL in Ontario occur in clusters, in areas mapped as coarse-grained till in Canadian Shield terrain, as isolated till mounds surrounded by streamlined bedrock, and in larger swarms in thicker (>40 m) unconsolidated sediment zones. Commonly, larger clusters of MSGL occur within or along the margins of large topographic lowlands, and in many cases, MSGL long-axes are parallel to the lows, or diverge from or converge towards the central portions of low-lying terrain. The downflow extents of numerous clusters are commonly marked by large moraine complexes, representing clear flow sets. Within each flowset, a wide variety of sediment-cored, mixed, and bedrock-cored bedforms exist. Low-relief (<6 m high) MSGL are also observed across regional bedrock highs separating lowland flowsets. Small (<3 m high) recessional moraines overlie the MSGL across portions of the exposed beds. Large areas of iceberg scouring are observed downflow of the MSGL clusters in areas inundated by proglacial lakes during deglaciation. The abundance of MSGL suggest a larger proportion of the LIS margin developed ice streams than previously recognized, particularly in hard-bedded Canadian Shield areas. MSGL distribution and relationships with local to regional topography and antecedent bedforms suggest several ice streams were initiated within topographic lows as the ice sheet thinned during deglaciation. Ice stream propagation was likely enhanced in many areas due to the existence of deep proglacial lakes fronting the ice margin. Future work involves field-mapping the surficial geology of several parts of the exposed beds of these inferred paleo-ice streams to refine understanding of sediment-landform assemblages and collect samples to improve knowledge on the timing of ice stream activity in the region.
Summary(Plain Language Summary, not published)
This work is an ongoing process of re-examination of various glacial landscapes of the Canadian Shield, using publicly available LiDAR data, to augment our knowledge of the last glaciation of North America. This new higher resolution digital elevation data reveals additional information not historically documented or observed from older aerial photographs.
GEOSCAN ID329193

 
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