Lithalsas of the Great Slave Lowland, Northwest Territories, occur within fine-grained glaciolacustrine, lacustrine, and alluvial deposits. Detailed investigations of a lithalsa revealed that it is composed of ice-rich sediments with ice lenses up to 0.2 m thick below 4 m depth. The observed ice accounted for about 2 m of the 4 m between the top of the lithalsa and adjacent terrain. The ice is isotopically similar to modern surface water, but enriched in δ18O relative to local precipitation. Total soluble cation concentrations are low in the basal, Shield-derived and unweathered glaciolacustrine sediments of the lithalsa. Higher concentrations in the overlying Holocene-aged lacustrine and alluvial deposits may be due to greater ion availability in Holocene surface waters. Increasing Cl- and Na+ concentrations in clays at depth likely relate to exclusion and migration of these dissolved ions in pore water during ice lens formation though total soluble cations remain comparatively low. The lithalsa developed 700 to 300 cal yr BP. A conceptual model of lithalsa formation and landscape evolution illustrates that this feature and more than 1800 other lithalsas in the region have developed in association with Holocene terrestrial emergence following lake-level recession. Copyright

ground ice, lake-level recession, lithalsa, soil geochemistry, stable isotopes
Earth Surface Processes and Landforms
Department of Geography and Environmental Studies

Gaanderse, A.J.R. (Adrian J.R.), Wolfe, S.A, & Burn, C. (2018). Composition and origin of a lithalsa related to lake-level recession and Holocene terrestrial emergence, Northwest Territories, Canada. Earth Surface Processes and Landforms, 43(5), 1032–1043. doi:10.1002/esp.4302