Method of deglaciation, age of submergence, and rate of uplift west and east of Hudson Bay, Canada
DOI:
https://doi.org/10.26485/BP/1962/11/28Keywords:
ice movement, Wisconsin glaciation, isostatic readjustment, rate of upliftAbstract
Directions of ice movement during the maximum stage of Wisconsin (last) glaciation are deduced only from the transport of erratics, from the positions of the outer terminal moraines, and from the area of greatest isostatic readjustment.
The successive positions of the ice margins during deglaciation are made clear with the help of De Geer moraines below the marine limit and by another type of minor moraine in the supraquatic area. The continental ice-sheet split into 2 parts at the time Hudson Bay Basin became free of the last ice-sheet. The final positions of the ice margins west of Hudson Bay are made clear by minor moraines, ice-dammed lakes, glaciofluvial channels, and shifts in directions of striae. This position of the last ice west of Hudson Bay has been named the "Keewatin ice divide".
Geological investigations, archaeological studies and radiocarbon dates indicate a similarity of events around Hudson Bay, commencing at the time Hudson Bay Basin was freed of the continental ice-sheet. The sea that then spread around Hudson Bay 5 000 to 6 000 years BC is named "Tyrrell Sea". The subsequent rate of land emergence has been measured by dating organic, shell, and bone materials related to strand lines. The rate of uplift decreased from an initial rapid uplift of about 600 cms per century to later a much decreased rate of 30 to 90 cms per century. A slightly warmer climate than present took place about 3 000 years BC as indicated by the radio carbon age on buried plants having now a more southerly distribution.
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