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TitleLithalsa distribution, morphology and landscape associations in the Great Slave Lowland, Northwest Territories, Canada
AuthorWolfe, S A; Stevens, C W; Gaanderse, A J; Oldenborger, G A
SourceGeomorphology vol. 204, 2013 p. 302-313,
Alt SeriesEarth Sciences Sector, Contribution Series 20130119
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNorthwest Territories
NTS85J/07; 85J/08; 85J/09; 85J/10; 85J/11; 85J/12; 85J/13; 85J/14; 85J/15; 85J/16
AreaYellowknife; Great Slave Lake
Lat/Long WENS-116.1667 -114.2500 62.8833 62.2500
Subjectssurficial geology/geomorphology; geophysics; hydrogeology; environmental geology; stratigraphy; permafrost; ground ice; periglacial features; frost heaving; talik; ice lenses; surface waters; streams; vegetation; remote sensing; photogrammetric techniques; airphoto interpretation; satellite imagery; geophysical logging; resistivity logging; boreholes; core samples; sediments; organic deposits; peatlands; glacial deposits; marine sediments; silts; clays; sands; groundwater; climate; stratigraphic analyses; modelling; topography; Holocene; Recent; Great Slave Lowland; Great Slave Upland; lithalsas; discontinuous permafrost; ponds; glaciolacustrine sediments; lacustrine sediments; alluvial sediments; glaciomarine sediments; climate change; infrastructure risks; permafrost thaw; geological hazards; Lidar surveys; spatial distribution; land cover; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; photographs; aerial photographs; cross-sections; schematic cross-sections; lithologic sections; geophysical logs; plots; histograms; tables
ProgramLand-based Infrastructure, Climate Change Geoscience
AbstractLithalsas are permafrost mounds formed by ice segregation in mineral-rich soil that occur within the zone of discontinuous permafrost. Nearly 1800 lithalsas were mapped using archival aerial photographs within the Great Slave Lowland, Northwest Territories, Canada. These are up to 8 m high and several hundred meters in length and width. One lithalsa, examined by electrical resistivity and boreholes, rises 4 to 6 m above an adjacent peatland, shows clear evidence of ice-segregation at depth and ground heave of between 2.5 and 4.0 m, and is estimated to have formed within the past 700 years. Regionally, lithalsas are typically located adjacent to ponds and streams with mature forms vegetated by deciduous (birch) forest or mixed (birch and spruce) forest with a herb-shrub understory and include circular, crescentic and linear forms. They are abundant within the Lowland region, which contains widespread glaciolacustrine, lacustrine and alluvial fine-grained sediments. The lithalsas are most common within the first few tens of meters above the present level of Great Slave Lake, indicating that many are late Holocene, and some less than 1000 years, in age. A comparison with lithalsas in contemporary environments reveals that comparatively warm but extensive discontinuous permafrost, fine-grained sediments (alluvial, lacustrine, marine or glaciomarine), and available groundwater supply provide the climatic and hydro-geological parameters for the development of lithalsas in permafrost terrain. The identification of lithalsas in this region is important given their sensitivity to climate change and potential hazards to northern infrastructure upon thawing.
Summary(Plain Language Summary, not published)
We undertook the first regional investigation of ice-rich terrain, known as lithalsas, found within the Great Slave Lowland of the Northwest Territories. Lithalsas are permafrost mounds formed by ice lens growth in mineral soil that occur within the zone of discontinuous permafrost. In our study area, lithalsa mounds can be up to 8 m high and many hundreds of metres in length. We mapped nearly 1800 of these in the Lowland area. Lithalsas are likely more common than previously recognized and are significant as they represent potentially ice-rich, thaw-sensitive, and frost-susceptible terrain that is sensitive to climatic and ecological disturbances.