Northwest Territories

ABSTRACT. Ground temperature records in the Lower Mackenzie Valley have been obtained for seven sites in the 1965 to 1966 period by installing thermistor cables in seismic shot holes drilled for the purpose. From the initial measurements, permafrost thickness is estimated at about 350 feet for Arctic Red River and 400 feet for a site 14 miles west of Fort McPherson. In the south-central part of the Mackenzie Delta, in an area of gradually shifting channels and infilling lakes, the depth is 350 feet, or possibly more. In the distal part of the Delta, where new islands are growing, permafrost is aggrading downwards in the saturated alluvial soils. At four sites within two feet of sea level, permafrost may be only 60 to I O O feet deep. Here, permafrost should continue to aggrade for many centuries more. RÉSUMÉ. Profondeurs du pergélisol, basse vallée du Mackenzie, T A.- O. Au moyen de cables à thermistor installés dans des puits sismiques forés à cette fin, on a relevé les tempéra-tures dans le sol pour sept sites de la basse vallée du Mackenzie, pour la période de I 965 à 1966. A partir de ces premières mesures, on estime l’épaisseur du pergélisol à environ 350 pieds ( I 20 m) pour Arctic Red River et à 400 pieds ( I 35 m) pour un site localisé