68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

ORIGIN AND COMPOSITION OF A LITHALSA IN THE GREAT SLAVE LOWLAND, NORTHWEST TERRITORIES

Adrian Gaanderse, Carleton University (Canada)
Stephen Wolfe, Geological Survey of Canada, Natural Resources Canada (Canada)
Chris Burn, Carleton University (Canada)

Recognition of lithalsas in the Great Slave Lowland, NT, prompted an investigation to determine the geomorphic origin and composition of one lithalsa. Ice-poor conditions occur within the upper 4 m of substrate, with substantial increases in ice content at greater depths within clays. The lithalsa core is composed of layered ice lenses over 0.1 m thick, formed of isotopically-modern meteoric waters. The stratigraphy of clays, silts, and sands is sub-parallel, but domed in accordance with surficial relief of the lithalsa. The estimated differential heave between the lithalsa and an adjacent peatland is approximately 2.8 m, of which 2.17 m is directly accounted for by excess ice lenses within the upper 8.4 m of material. 14C dating indicates permafrost aggradation within the lithalsa occurred between 700 and 400 cal yr BP.