Abstract

The 3 to 5 m thick muddy and sandy tidal flats on the western and southwestern shores of marine, mesotidal, subarctic, locally brackish, intracratonic basins of James Bay and Hudson Bay, resemble those of other basins, except they do not contain major tidal channels and they display characteristic features that reflect their cold setting. These features include the following: 1) surficial scours caused by ice floes or ice-pushed boulders and filled with poorly sorted, polymictic sand and gravel; 2) scattered, frost-resistant, subrounded, igneous and metamorphic glacial erratics locally reworked by sea ice; 3) frost-shattered, angular pebbles of limestone and dolostone; and 4) coarse, ice-rafted material enclosed in fine grained, water-laid deposits. The macro-infauna is restricted in numbers of species (primarily Macoma balthica and Hydrobia minuta) and locally in numbers of individuals (along brackish coasts).

The coastal marshes are dominated by Puccinellia phryganodes, Carex subspathacea, and Hyppuris tetraphilla, and the marsh deposits develop diagnostic laminae reflecting either mat root structure of Puccinellia phryganodes, or buried, discretely spaced hollow stems of Hippuris tetraphilla. The marshes grade landward into extensive emerging peatlands (fens and bogs), where, 100 km inland, 3 to 4 m of peat have accumulated in the last 3500 to 4000 years. Cryoturbation and other pedogenic processes imprint emerged suquences with convolutions and gleysolic characteristics.