ABSTRACT: Palsas and mineral permafrost mounds in Northern Quebec

CGRG Bibliography of Canadian Geomorphology
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Abstract

Palsas and mineral permafrost mounds are widespread periglacial landforms characteristic of the discontinuous permafrost zone. Palsas are found dominantly in the forest tundra and mineral permafrost mounds occur mainly in the shrub tundra zone in somewhat colder environments, although exceptions and transitional features between the two landform types do exist. Almost all palsas have a mineral core within which most of the ice segregation and heaving have taken place. Post-glacial marine silts are the dominant material in which all these landforms are developed. Both palsas and mineral permafrost mounds can form either by the growth or single mounds or by dissection of large peat or permafrost palteaus. A general parabolic function curve has been established between feature size and permafrost thickness. Thermal and isotopic data indicate that the permafrost is in equilibrium with present climatic regime. However, the thermal equilibriumin each feature is controlled by vegetation height and density which control snow distribution around the sides. Peat stratigraphy and 14C dates indicate that three generations of palsas and mineral permafrost mounds dominate amongst these landforms: from 1500 to 1050 BP, from 650 to 200 BP and very recent. For the last 150 years, degradation following active layer and slope processes has been dominant over incipience and growth of new features.

Bibliography of Canadian Geomorphology