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TitleCharacteristics of glacial Lake McConnell clay, Great Slave Lowland, Northwest Territories
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AuthorAden, A A; Wolfe, S A; Percival, J B; Grenier, A
SourceGeological Survey of Canada, Current Research (Online) 2015-7, 2015, 16 pages, https://doi.org/10.4095/296860
Year2015
PublisherNatural Resources Canada
Documentserial
Lang.English
Mediadigital; on-line
File formatpdf
ProvinceNorthwest Territories
NTS85J/10
AreaBoundary Creek; Great Slave Lowland; Yellowknife
Lat/Long WENS-114.9694 -114.9569 62.5319 62.5264
Subjectssurficial geology/geomorphology; mineralogy; clays; glaciolacustrine deposits; permafrost; grain size analyses; textural analyses; Glacial Lake McConnell; Quaternary
Illustrationslocation maps; photomicrographs; tables; ternary diagrams; plots
ProgramLand-based Infrastructure, Climate Change Geoscience
Released2015 11 20
AbstractGrain-size analysis from a drilling program 30 km west of Yellowknife defined three distinct sediment groups: a lowermost clay-rich unit (Group 1), a middle silt-rich unit (Group 2), and a sand-rich upper unit (Group 3). Physical properties and mineralogy were investigated for two fine-grained clay samples by the GSC Sedimentology Laboratory and X-ray Mineralogy Laboratory, respectively; sediment texture was determined by the authors. Both samples plot above the A-line of the Casagrande plasticity chart, indicating they are clays with intermediate to high plasticity, and classified by Atterberg limit analysis as inactive. The majority of nonclay minerals in the clay-size fraction are quartz; and the remaining clay minerals are primarily detrital mica, chlorite, and kaolinite. Minor to trace amounts of mixed-layer clay minerals (most likely illite-smectite) are noted in the clay-size fractions, whereas only trace amounts are observed in other group samples. These analyses confirm that the two samples fall within Group 1, and are glaciolacustrine, originating from glacial Lake McConnell (ca. 13.0-9.5 ka), and derived primarily from local granitic bedrock, with perhaps some weathering or allogenic contribution, resulting in traces of mixed-layer clay minerals. Scanning electron microscope analysis revealed subrounded to subangular silt-size grains of detrital origin, randomly distributed in a clay matrix; with possible evidence of minor compaction within the soil. Coarser grain size, higher quartz content, and only trace mixed-layer clay minerals suggest that Group 2 and 3 sediments originate from reworking and redeposition of Group 1 sediments within lacustrine or alluvial settings. High ground-ice contents imply these sediments are prone to instability if thawed.
Summary(Plain Language Summary, not published)
Grain size analysis from a drilling program at a study site 30 km west of Yellowknife defined three distinct groupings of sediments: a lowermost clay-rich unit (Group 1), a middle silt-rich unit (Group 2) and a sand-rich upper unit (Group 3). Physical properties, mineralogy and sediment texture were determined for two fine-grained clay samples from the lowermost unit. Analyses confirm that the two samples fall within Group 1, and are glaciolacustrine, originating from Glacial Lake McConnell (ca. 13.0 ¿ 9.5 ka), and derived primarily from local granitic bedrock. High ground ice contents imply these sediments may be prone to instability.
GEOSCAN ID296860