Proceedings Candian Symposium on Coastal Sand Dunes 1990, 137-157

I.P. MARTINI

Department of Land Resource Science, University of Guelph, Guelph, Ont. NlG 2Wl

On the tectonically stable, flat, open, subarctic, emerging coastal areas of the Hudson Bay Lowland modern sediments are derived from cannibalization of relatively thin Pleistocene drift and glacio-marine mud. A change occurs from absence of dunes in southern James Bay, to some partially deflated foredunes on the slightly sandier and more exposed coasts of subarctic northern James Bay, to low but well developed foredunes on the open beach ridges of southwestern Hudson Bay. Some beach ridges develop few, low, discontinuous shadow dunes in the lee of gravel clusters or of sparse grassy vegetation clumps; others develop sizable foredunes on the active ridge. The active tidal flat-beach-foredunes links show a gradation from sandy intertidal areas, to wide deflated frontal part of beach ridges, to low shadow foredunes anchored by clumps of Honkenia peploides, up into higher foredunes colonized by Elymus mollis. Numerous, shallow, pits dot the landward facing precipitation slopes of foredunes, dug by polar bears during the summer. Some of the pits breach the dune crests and develop into blowouts. The dunes become deflated as the land emerges and they are cut off from the sandy beach source. Dissected, star shaped, 3-5 m high dune remnants occur isolated over wide, flat, deflated, pebble armoured, exhumed beach ridge surfaces. Low vegetation patches trap some sand on the deflated surface imparting characteristic microtopography to it. Few low mounds or thin patches of sand are preserved under tundra which, farther inland (south), is replaced by fens, bogs or coniferous forests. Another byproduct of intense periods of deflation or farther inland where the vegetative protection is disrupted by fires, is the formation of thin, sorted sandy laminae in peat sequences which develop in inter-ridge areas.