Terrain types in the southern Mackenzie River valley can be arranged into morphological series which are, in part, continuous and, in part, discontinuous, so as to allow speculation on the probable evolution of organic terrain in the area from frozen to unfrozen landscapes, accompanying the long-term amelioration of the climate during postglacial times. Stipploid terrain on gentle slopes retained its lineated character during progressive thawing. Similarly, polygoid terrain on frozen flats retained its reticulate character, though progressive thawing locally was probably associated with increasingly diffuse pattern boundaries, ultimately yielding marbloid organic terrain. Some frozen terrazoid terrain of raised peat probably evolved into unfrozen polygoid peatland by a progressive enlargement of water-filled depressions.

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