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TitleComposition and origin of a lithalsa related to lake-level recession and Holocene terrestrial emergence, Northwest Territories, Canada
AuthorGaanderse, A J R; Wolfe, S A; Burn, C R
SourceEarth Surface Processes and Landforms vol. 43, issue 5, 2017 p. 1032-1043, https://doi.org/10.1002/esp.4302
Year2017
Alt SeriesNatural Resources Canada, Contribution Series 20160309
PublisherWiley-Blackwell
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS85J; 85K
AreaGreat Slave Lake
Lat/Long WENS-118.0000 -114.0000 63.0000 62.0000
Subjectssurficial geology/geomorphology; environmental geology; geochemistry; stratigraphy; geochronology; Nature and Environment; Science and Technology; Holocene; permafrost; ground ice; periglacial features; glacial lakes; water levels; emergence; ice lenses; stable isotope studies; oxygen isotopes; clays; sands; silts; peatlands; chlorine geochemistry; sodium geochemistry; postglacial evolution; radiometric dating; radiocarbon dating; pH patterns; sediment geochemistry; topography; Great Slave Lowland; Glacial Lake McConnell; lithalsas; climate change; permafrost thaw; cumulative effects; glaciolacustrine sediments; lacustrine sediments; alluvial sediments; landscape evolution; Phanerozoic; Cenozoic; Quaternary
Illustrationsgeoscientific sketch maps; photographs; correlation sections; ternary diagrams; profiles; plots; tables; schematic representations
ProgramClimate Change Geoscience, Land-based Infrastructure
Released2017 12 07
AbstractLithalsas 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 delta-18O 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.
Summary(Plain Language Summary, not published)
Lithalsas are topographically-raised permafrost mounds containing considerable volumes of ice lenses within their core. Lithalsas of the Great Slave Lowland, Northwest Territories, have developed in fine-grained glaciolacustrine, lacustrine, and alluvial deposits. Detailed investigations at one lithalsa revealed that, below 4 m depth, it was composed of ice-rich sediments with ice lenses up to 0.2 m thick. The observed ice accounted for about 2 of the 4 m difference in elevation between the top of the lithalsa and adjacent terrain. The lithalsa developed as recently as 700 to 300 years ago. A conceptual model of lithalsa formation and landscape evolution suggests that many lithalsas in the region developed recently in association with Holocene terrestrial emergence. Thawing of lithalsa terrain will result in substantive local subsidence and thermokarst development in this region.
GEOSCAN ID310546