ABSTRACT: Le pingo d'Aishihik, sud-ouest du Yukon : caractères morphogénétiques et cadre temporel [The morphology, genesis and temporal context of the Aishihik Pingo (SW Yukon)]

CGRG Bibliography of Canadian Geomorphology
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Abstract

These new observations of the external and internal structures of the Aishihik mound confirm that it is a pingo, classically interpreted as being of the closed-system type, whereas it is at the southern limit of discontinuous permafrost. The external evidence supporting this conclusion is the conical form, with a height/diameter ratio of the order of 10 per cent (4,75/44m), a central crater, and a marshy and lacustrine environment. In addition to this, the internal evidence from the borings includes: a pure ice core 193 cm thick, with a mantle of unconsolidated sediments, the convexity of the monocrystalline ice lenses, and the presence of unfrozen material at the base. Normal faults and tensional fractures further bear witness to the development of internal pressure during growth of the pingo. Thermal profiles of the mantle show that the pingo is in equilibrium with the present climate (mean annual temperature of -4,4 degrees C). Palynologicalanalyses suggest that the silts which form the flanks of the pingo were deposited in the late glacial period. Mineralogical analyses show that the permafrost predates the White River Ash (1230 BP). Some palynological data suggest that the pingo was growing prior to the deposition of the White River Ash, and was reactivated after this event.

Bibliography of Canadian Geomorphology