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| Keewatin Lobe | |
|---|---|
| Name | Keewatin Lobe |
| Type | Ice lobe |
| Location | North America |
| Status | Extinct (Pleistocene) |
Keewatin Lobe The Keewatin Lobe was a major ice lobe of the Laurentide Ice Sheet that advanced across parts of present-day Canada and the United States during the Pleistocene epoch, profoundly shaping the Hudson Bay drainage and adjacent landscapes. Influential in the development of features associated with the Wisconsin glaciation and the Last Glacial Maximum, it interacted with other lobes such as the Laurentide Ice Sheet#Keewatin-adjacent outlets and left stratigraphic, geomorphologic, and hydrologic legacies observable in regions including Manitoba, Saskatchewan, Ontario, North Dakota, and Minnesota.
The lobe represented a persistent ice mass originating from the Keewatin Province sector of the Laurentide Ice Sheet and operated within the wider context of Late Pleistocene glaciation phenomena explored by investigators from institutions like the Geological Survey of Canada, the United States Geological Survey, and universities such as the University of Manitoba and the University of Minnesota. Its flow regimes and margin positions were reconstructed using evidence from mapped drumlins of the Prince Albert region, moraines including Portage-type ridges, and proglacial lake sequences such as Lake Agassiz and Lake Winnipegosis, with correlations drawn to chronologies based on radiocarbon dating and optically stimulated luminescence studies.
The Keewatin Lobe developed as ice accumulation over the Canadian Shield outpaced ablation during stadials of the Pleistocene epoch, fed by sneeuw and firn fed from upland centers near the Keewatin Ice Divide and flowing radially toward lowlands near Hudson Bay and the Laurentian Channel. Interactions with tectono-stratigraphic elements of the Superior Province, sediment supply from the Boreal Shield, and thermal regimes influenced by underlying bedrock at sites like the Manitoba Escarpment governed its basal sliding and subglacial erosion. Episodes of readvance and retreat correspond to climate events recorded in the Greenland ice cores, North Atlantic marine isotope stages, and terrestrial stratigraphic sequences correlated with the Younger Dryas and earlier interstadials.
At its maximum, the lobe extended from accumulation centers on the Canadian Shield into plains of the Great Plains, reaching proximities to Minneapolis–Saint Paul, westward margins near Saskatoon, and eastern limits bordering the Ontario interior drainage. Margin features include terminal and recessional moraines mapped across Manitoba and North Dakota and meltwater channels feeding proglacial basins such as Lake Agassiz, whose shorelines like the Herman Beach and Norcross strandlines mark former extents. Adjoining ice masses like the Cordilleran Ice Sheet and the Greenland Ice Sheet were separate but contemporaneous in Pleistocene chronologies established by comparative stratigraphy and isotopic evidence.
Flow dynamics of the lobe involved basal sliding, regelation, and internal deformation studied through analogs from modern ice streams like Jakobshavn Glacier and modeled with frameworks used by groups at the University of Alaska Fairbanks and University of Cambridge. Subglacial processes produced streamlined landforms including drumlin fields near Winnipeg, longitudinal lineations observed in Saskatchewan tills, and extensive meltwater corridor systems comparable to the Funnelbeaker-analog pathways reconstructed in European Pleistocene studies. Sediment transport mechanisms produced layered tills, lodgement and melt-out deposits, and glaciotectonic deformation documented in cores from the Quaternary Research Center and regional boreholes.
Climate drivers influencing the lobe are tied to shifts recorded in proxies from Greenland, Antarctica, North Atlantic sediment cores like those from the North Atlantic Ocean, and terrestrial pollen sequences from sites studied by teams at the Royal Ontario Museum and the Canadian Museum of Nature. Glacial-associated albedo changes, ice-sheet feedbacks on atmospheric circulation patterns including shifts in the jet stream, and freshwater fluxes into the North Atlantic associated with melting ice impacted the Holocene onset and abrupt events such as the 8.2 kiloyear event. The lobe’s presence altered drainage networks, creating legacy wetlands, kettle lakes, and fertile till plains that influenced postglacial successional trajectories studied by ecologists at the University of Manitoba and conservation organizations like the Nature Conservancy.
The geomorphic imprint of the Keewatin Lobe directed migration routes and archaeological site preservation patterns important to researchers at institutions such as the Canadian Museum of History, the Smithsonian Institution, and academic programs in archaeology at the University of Calgary and University of Toronto. Postglacial landscapes hosted ecosystems supporting boreal forest colonization, peatland development, and species distributions involving taxa documented by the Royal Ontario Museum and the Canadian Wildlife Service. Indigenous histories and oral traditions of groups including the Cree, Métis, and Ojibwe reference transformed landscapes and waterways that correspond with geomorphologic reconstructions used in collaborative studies with provincial bodies like Manitoba Conservation.
Reconstruction of the lobe’s margins and chronology has been advanced by multidisciplinary teams employing remote sensing from platforms used by NASA, geophysical surveys executed by the Geological Survey of Canada, sediment core analyses published in journals affiliated with the Quaternary Research Association, and GIS mapping by centers such as the National Centre for Geographic Information and Analysis. Key datasets include digital elevation models, till provenance geochemistry, cosmogenic nuclide exposure ages generated at laboratories like the University of Oxford and ETH Zurich, and paleohydrological reconstructions integrated into regional models developed at the University of Minnesota and McGill University. Ongoing work focuses on refining interactions between ice dynamics, proglacial lakes like Lake Agassiz, and abrupt climate events recorded across North American Pleistocene archives.
Category:Glaciology Category:Pleistocene North America Category:Laurentide Ice Sheet