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TitleMiddle Wisconsinan marine shells near Repulse Bay, Nunavut, Canada: implications for Marine Isotope Stage 3 ice-free conditions and Laurentide Ice Sheet dynamics in north-west Hudson Bay
AuthorMcMartin, IORCID logo; Campbell, J E; Dredge, L A
SourceJournal of Quaternary Science vol. 34, issue 1, 2019 p. 64-75,
Alt SeriesNatural Resources Canada, Contribution Series 20180184
Mediapaper; on-line; digital
File formatpdf; html
NTS46E/14; 46E/15; 46E/16; 46F/13; 46K/04; 46K/05; 46L/01; 46L/02; 46L/03; 46L/06; 46L/07; 46L/08
AreaRepulse Bay; Hudson Bay
Lat/Long WENS -87.0167 -85.8833 66.4500 65.9167
Subjectssurficial geology/geomorphology; paleontology; geochronology; Nature and Environment; glacial history; glaciation; Wisconsinian glacial stage; deglaciation; ice retreat; ice margins; ice flow; submergence; fossils; marine organisms; marine environments; ice sheets; sea ice; radiometric dating; radiocarbon dating; carbon-14 dates; glacial deposits; tills; sands; silts; clays; glacial landforms; glacial features; glacial striations; Laurentide Ice Sheet; Marine Isotope Stage 3; Mollusks; Rae Isthmus Ice Stream; proto-Roes Welcome Sound; Keewatin Ice Divide; Gulf of Boothia Ice Stream; Lancaster Sound Ice Stream; Canadian Shield; Hudson Bay Lowlands; Last Glacial Maximum; ice streams; limit of glaciation; submergence, marine; limit of submergence, marine; streamlined tills, carbonate; ice-flow directions; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; digital elevation models; photographs; tables
ProgramGEM2: Geo-mapping for Energy and Minerals Rae Province, Synthesis of glacial history
ProgramPolar Continental Shelf Program
Released2019 01 11
AbstractEvidence suggesting a reduction of the Laurentide Ice Sheet (LIS) during Marine Isotope Stage 3 (MIS 3) is widespread but the boundaries of the ice sheet and the timing of minimum ice extent are still poorly constrained. Radiocarbon dating of glacially transported marine mollusks in Rae Isthmus ice stream till south of Repulse Bay, Nunavut, Canada, provides new evidence for MIS 3 deglaciation in the north-west part of Hudson Bay. Middle Wisconsinan finite 14C ages varying between 31.7 and 39.2k 14C a BP (~35.0 and 43.7k cal a) indicate a marine event(s) for a minimum of ~8.7k cal years. Our findings suggest ice-free conditions in the ice stream source area in proto-Roes Welcome Sound, and therefore significant glacial recession of the LIS margin during the Middle Wisconsinan, much farther in the interior of the ice sheet than previously known. The marine incursion possibly occurred because of a calving bay developed from the north in the Gulf of Boothia - Committee Bay area following the recession and collapse of the ice stream. After the MIS 3 marine episode(s), the topographically controlled ice stream stemming from the eastern end of the Keewatin Ice Divide was re-activated, and maintained until deglaciation.
Summary(Plain Language Summary, not published)
Previously unknown, far-travelled glacial sediments containing tiny marine shell fragments dating back to a time prior to the last glacial maximum were discovered near the community of Repulse Bay, central mainland Nunavut. This discovery has implications for the history of the Laurentide Ice Sheet because it indicates the partial decay of a core area of the ice sheet in the middle of a glacial period, critical to climate change studies, and also it provides new geological knowledge on the provenance of surficial materials used to trace back mineralized debris to their bedrock sources in formerly glaciated terrain. This work was conducted under the Wager Bay North and Rae Glacial Synthesis activities at the Geological Survey of Canada, as part of Natural Resources Canada's Geo-mapping for Energy and Minerals (GEM1&2) Program.

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