ABSTRACT: Investigations of the geomorphology and sedimentology of permafrost related pingos and palsas; ancient and modern.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Pingos and palsas are the two principal types of cryogenic mound and their distribution is controlled by (or at least related to) the occurrence of different permafrost types. Pingos are associated with both continuous and discontinuous permafrost cover. Palsas, on the other hand, are associated with sporadic and discontinuous permafrost cover. Although there are two generally accepted hypotheses of pingo formation: hydrostatic and hydraulic, not all contemporary arctic pingos can be readily explained by these. The initiation of a palsa growth cycle, through the localised deep penetration of winter frost, is thought to be linked to either the removal of insulating snow cover in winter or albedo variations brought about by vegetational changes. The fundamental mechanism of palsa growth, cryosuction, however, is the same for all palsas. To investigate the spectrum of pingos and palsas, case studies were undertaken on Banks Island, Northwest Territories, Canada; on Traill , east Greenland and near Kuujjuaq, northern Quéec, Canada. Certain arctic pingos do not match all the criteria demanded by the classic genetic hypotheses and there appears to be an overlap between the systems. Additionally, type examples of hydraulic pingos are thought to be located in positions which are dictated by sub-surface geological structures such as sills. An attempt has also been made to clarify the previous identification of features interpreted as relict `pingos' from four sites within England and Wales. In Québec the growth and disintegration of mineral palsas can develop a complex terrain of ridges and depressions in periods as short as 4000 years. This terrain has many similarities with the relic `pingo' sites of north west Europe and may tentatively be used as a modern analogue for these features, although the exact mechanisms of relict `pingo' formation are still not fully understood. Pre-Pleistocene `pingos' undoubtedly existed, however, their exact character remains obscure.

Bibliography of Canadian Geomorphology