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TitreDistribution and lithostratigraphic controls of massive ice in Northwest Territories and northern Yukon: new insights from seismic shothole drillers' logs
AuteurSmith, I R
SourceCANQUA, Canadian Quaternary Association annual meeting, abstracts; 2013 p. 1
Année2013
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130002
ÉditeurAssociation canadienne pour l'étude du Quaternaire
RéunionCANQUA; Edmonton; CA; août 18-21, 2013
Documentlivre
Lang.anglais
Mediapapier
Formatspdf
ProvinceTerritoires du Nord-Ouest; Yukon
SNRC106I; 106J; 106K; 106L; 106M; 106N; 106O; 106P; 107A; 107B; 107C/01; 107C/02; 107C/03; 107C/04; 107C/05; 107C/06; 107C/07; 107C/08; 107D; 107E/01; 107E/02; 107E/03; 107E/08
Lat/Long OENS-136.0000 -128.0000 70.5000 66.0000
Sujetsglace; morphologie de la glace; glace massive; lithostratigraphie; géologie des dépôts meubles/géomorphologie; stratigraphie; Cénozoïque; Quaternaire
ProgrammeInfrastructures terrestres, Géosciences de changements climatiques
Résumé(disponible en anglais seulement)
Massive ice and other ice-rich sediments (ground ice) are considered to be widespread in areas of northwestern mainland Canada. These conditions constitute significant existing and climate change-amplified hazard potential related to rapid coastal erosion and thermokarst in areas of potential infrastructure development. While many massive ice occurrences have been the subject of direct and detailed field investigation, including monitoring, the ability to detect, quantify, and predict the occurrence of such deposits over large spatial areas is often limited to outcrops and those cases where surface geomorphology (heaving or thermokarst) can be discerned, yet even here, thickness and lateral extents remain largely unknown.
Amongst the earliest (1970s) regional assessments of massive ice in the Tuktoyaktuk Peninsula and Richards Island area stemmed from analysis of ~15k seismic shothole drillers' log records by Mackay, Rampton and others. Recent research by Smith (2011) who recovered all available shothole drillers' log records from Industry archives within continental NWT and Yukon has expanded this knowledge base by orders of magnitude (344k records), from which new inferences about massive ice's thickness, depth, spatial extent, and over and under-lying lithostratigraphy can be drawn.
Massive ice is recorded in 2354 shothole drillers' logs, and ranges in thickness from an assigned 1.0 m minimum, up to 61 m, averaging 8.8 m (an additional 13 753 shothole drillers' logs reported ground ice, many of which likely represent massive ice, or what others have classified as 'icy sediments'). The upper limit of approximately 23% of all shothole massive ice records occur at surface (base of active layer), while ~56% initiate within the uppermost 5 m; less than 10% of massive ice bodies extend below 30 m depth. The highest concentrations of massive ice (46-51%) occur between 4 and 14 m depth. Significant variations are seen in the distribution of massive ice deposits, with highest occurrences in the Tuktoyaktuk Peninsula (51% of all massive ice records), Richards Island, Arctic Coastal Plain and northern Richardson mountains. Lesser concentrations are found in Eagle Plain, central Richardson Mountains, lower Mackenzie River, and Colville Hills; south of these regions, massive ice deposits are rare to absent. Associations between massive ice and shothole-derived surficial geology reinforce previous assertions that such deposits are most commonly found in areas of till cover, and that most massive ice bodies occur at the lithostratigraphic boundary between different materials (73% of the 1883 records which fully penetrate a massive ice body). Shothole-derived lithostratigraphy confirms overall trends in overlying and underlying materials, but suggests that the overlying till/underlying sand and gravel relationship has been overestimated, and that there is considerably greater variability in both the types of materials, and lithostratigraphic controls in different physiographic regions than has previously been identified.
Where sufficient data coverage warrants, the seismic shothole drillers' log-derived data provides a means for better regional characterization that can become integrated into environmental assessments and infrastructure engineering design and construction particularly in consideration of susceptibility to potential climatic change.
Résumé(Résumé en langage clair et simple, non publié)
Dans le nord du Canada, des dépôts de glace massive souterraine représentent un danger important, notamment pour toutes les infrastructures (routes, pipelines) et l'érosion côtière, et font l'objet de préoccupations majeures en ce qui a trait aux évaluations environnementales et à la conception technique. Une riche source d'information géoscientifique (diagraphies de forage en trou de tir sismique), récemment colligée à partir des archives de l'industrie, a permis d'accroître de plusieurs ordres de grandeur les renseignements sur l'emplacement, l'épaisseur et les contrôles de la formation de glace massive. Ces nouvelles données ont déjà été intégrées au processus de conception et d'approbation réglementaire de la route d'Inuvik à Tuktoyaktuk, et offrent de grandes possibilités pour prévoir les endroits où les dépôts de glace massive sont susceptibles de se trouver. Elles peuvent également servir à évaluer la sensibilité relative et le potentiel de risque de diverses zones en réponse aux éventuels changements climatiques. La recherche présentée met en évidence des découvertes majeures et offre des indications permettant de déterminer les zones où la recherche approfondie sur le terrain pourrait se concentrer, de même que les endroits où les nouvelles données contredisent ou soutiennent des reconstructions antérieures.
GEOSCAN ID292445