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Saturday, 16 August 2014

Raised shorelines, Polar Bear Provincial Park, Ontario


Polar Bear Provincial Park lies on the corner of James Bay, where it opens out into Hudson Bay proper.  This area has one of the highest rates of present-day isostatic recovery / land uplift anywhere in the world -- thought to be about 1.2m per century.  Not surprisingly, this low-lying landscape, at least in the coastal zone, is dominated by raised marine features.  

In the top photo (a vertical satellite image) we can see beach ridges galore and even old spits with arcuate tips. I'm not sure what the altitude of the marine limit is here, but I would guess it to be 100m at least......

In the lower photo, an oblique aerial photo, you can see to the right an area which is above the marine limit, with no raised marine features, and on the left a landscape dominated by beach ridges -- hundreds of them, following the contours of the landscape and stepping down all the way to present sea-level.

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Postscript, 17th August 2014.   I underestimated the altitude of the marine limit pretty drastically.  Not far away, in the Rivière Nastapoka area, eastern Hudson Bay (Quebec) the marine limit is at 248m, and there are abundant signs in the landscape of a dramatic inundation by the sea particularly beneath an altitude of 205m.  See this paper:

Géographie physique et Quaternaire
Volume 57, numéro 1, 2003, p. 65-83
Late Quaternary Deglaciation, Glaciomarine Sedimentation and Glacioisostatic Recovery in the Rivière Nastapoka Area, Eastern Hudson Bay, Northern Québec
Patrick Lajeunesse et Michel Allard




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