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TitleMiddle Wisconsinan marine shells near Repulse Bay, Nunavut, Canada: implications for MIS 3 ice-free conditions in northwest Hudson Bay
AuthorMcMartin, IORCID logo; Campbell, J; Dredge, L
Source20th Congress of the International Union for Quaternary Research (INQUA), online programme; 2019 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20180359
PublisherInternational Union for Quaternary Research
MeetingINQUA 2019: 20th Congress of the International Union for Quaternary Research; Dublin; IE; July 25-31, 2019
DocumentWeb site
Mediaon-line; digital
File formathtml; pdf (Adobe® Reader®)
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; ice flow; glaciation; ice retreat; ice margins; Wisconsinian glacial stage; submergence; source areas; fossils; radiometric dating; radiocarbon dating; glacial deposits; source rocks; models; Laurentide Ice Sheet; Hudson Bay Lowlands; Keewatin Ice Divide; Molluscs; Marine Isotope Stage 3; streamlined tills, carbonate; ice streams; ice-flow directions; limit of glaciation; submergence, marine; Phanerozoic; Cenozoic; Quaternary
ProgramGEM2: Geo-mapping for Energy and Minerals Rae Province, Synthesis of glacial history
Released2019 07 01
AbstractEvidence suggesting reduction of the Laurentide Ice Sheet (LIS) during MIS 3 is widespread but the boundaries of the ice sheet and timing of the minimum ice extent are still poorly constrained. The idea that the Middle Wisconsin was a period of significant glacial recession in the core area of the LIS has long been debated, and is still disputed today, particularly in the Hudson Bay Lowlands (HBL). Radiocarbon dating of glacially transported marine molluscs in streamlined till south of Repulse Bay, Nunavut, Canada, provides new evidence for MIS 3 deglaciation in the northwest part of Hudson Bay. Middle Wisconsinan finite 14C ages on 8 mollusc samples varying between 31.7 and 39.2 14C ka BP (~35.0 and 43.7 cal ka BP) indicate a marine event(s) for a minimum of ~8.7 cal ka. The fossiliferous calcareous till is derived from Paleozoic carbonates in proto-Roes Welcome Sound, and was deposited by a topographically controlled ice stream stemming from the eastern end of the Keewatin Ice Divide. Our findings suggest prior ice-free conditions in the ice stream source area indicating significant glacial recession of the LIS margin during the Middle Wisconsinan, much farther in the interior of the ice sheet than previously known. We propose here various possible configurations of ice limits during MIS 3 for the extended Repulse Bay region. The marine incursion possibly occurred as a result of a calving bay developed from the north in the Gulf of Boothia-Committee Bay area following the recession and collapse of an ice stream which was re-activated after the MIS 3 marine episode(s), and maintained until deglaciation. Alternatively, the development of a calving bay(s) from the east up Hudson Strait may have permitted deglaciation of Roes Welcome Sound and possibly other parts of Hudson Bay. Although these configurations of the LIS may not answer the recurring question whether MIS 3 was a time when the HBL were ice free, they significantly contrast with recent paleo-ice sheet models that suggest full ice conditions in the Repulse Bay region and can therefore contribute to the debate and configuration of the LIS during MIS 3.
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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