- Tyrrell Sea
The Tyrrell Sea, named for Canadian
geologist Joseph Tyrrell , is another name for prehistoricHudson Bay , namely as it existed during the retreat of theLaurentide Ice Sheet .Roughly 8,000 years BP, the Laurentide Ice Sheet thinned and split into two lobes, one centered over
Quebec -Labrador , the other overKeewatin . This drainedGlacial Lake Ojibway , a massiveproglacial lake south of the ice sheet, leading to the formation of the early Tyrrell Sea. [http://pubs.nrc-cnrc.gc.ca/rp/rppdf/e02-085.pdf] The weight of the ice had isostatically depressed the surface as much as 270-280 m below its current level, making the Tyrrell Sea much larger than modern Hudson Bay. [http://pubs.nrc-cnrc.gc.ca/rp/rppdf/e02-085.pdf] Indeed, in some places the shoreline was 100 to 250 km farther inland than at present. [http://geoinfo.amu.edu.pl/wpk/geos/GEO_6/GEO_PLATE_C-24.HTML] It was at its largest at roughly 7,000 years BP.(Pielou 223)Isostatic uplift proceeded rapidly after the retreat of the ice, as much as .09 m per year, causing the margins of the sea to regress quickly towards its present margins. [http://pubs.nrc-cnrc.gc.ca/rp/rppdf/e02-085.pdf] The rate of uplift decreased with time however, and in any event was nearly matched by sea-level rise from the melting ice sheets. [http://geoinfo.amu.edu.pl/wpk/geos/GEO_6/GEO_PLATE_C-24.HTML] When the Tyrrell Sea "became" Hudson Bay is difficult to define, as Hudson Bay is still shrinking from isostatic rebound.(Pielou 222-4)
References
* [http://geoinfo.amu.edu.pl/wpk/geos/GEO_6/GEO_PLATE_C-24.HTML "Geomorphology From Space, Plate C-24: Hudson Bay Shorelines."] (Accessed 3/7/06)
* [http://pubs.nrc-cnrc.gc.ca/rp/rppdf/e02-085.pdf Lajeuness, Patrick, and Michael Allard. "The Nastapoka drift belt, eastern Hudson Bay: implications of a stillstand of the Quebec-Labrador ice margin in the Tyrrell Sea at 8 ka BP." Canadian Journal of Earth Science, Vol. 40, 2003, pp. 65-76.] (Accessed 3/7/06)
*Pielou, E.C. "After the Ice Age". Chicago: University of Chicago Press, 1991.
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