| Title | High permafrost ice contents in Holocene slope deposits as observed from shallow geophysics and a coring program in Pangnirtung, Nunavut, Canada |
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| Author | Carbonneau, A -S; Allard, M; L'Hérault, E; LeBlanc, A -M |
| Source | American Geophysical Union Fall Meeting, abstracts volume; 2011 p. 1 |
| Links | Online - En ligne
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| Image |  |
| Year | 2011 |
| Alt Series | Earth Sciences Sector, Contribution Series 20110386 |
| Meeting | AGU Fall Meeting 2011; San Francisco; US; December 5-9, 2011 |
| Document | book |
| Lang. | English |
| Media | on-line; digital |
| File format | pdf |
| Province | Nunavut |
| NTS | 26I/04 |
| Area | Pangnirtung; Baffin Island |
| Lat/Long WENS | -66.0000 -65.5000 66.2500 66.0000 |
| Subjects | surficial geology/geomorphology; Nature and Environment; permafrost; freezing ground; ground ice; ground temperatures; Holocene; Cenozoic; Quaternary |
| Program | Climate Change Geoscience |
| Released | 2011 01 01 |
| Abstract | A study of permafrost conditions was undertaken in the Hamlet of Pangnirtung, Nunavut, by the Geological Survey of Canada (GSC) and Université Laval's Centre d'études nordiques (CEN) to support decision
makers in their community planning work. The methods used for this project were based on geophysical and geomorphological approaches, including permafrost cores drilled in surficial deposits and ground penetrating radar surveys using a GPR Pulse EKKO
100 extending to the complete community area and to its projected expansion sector. Laboratory analysis allowed a detailed characterization of permafrost in terms of water contents, salinity and grain size. Cryostratigraphic analysis was done via
CT-Scan imagery of frozen cores using medical imaging softwares such as Osiris. This non destructive method allows a 3D imaging of the entire core in order to locate the amount of the excess ice, determine the volumetric ice content and also
interpret the ice-formation processes that took place during freezing of the permafrost.
Our new map of the permafrost conditions in Pangnirtung illustrates that the dominant mapping unit consist of ice-rich colluvial deposits. Aggradationnal ice
formed syngenitically with slope sedimentation. Buried soils were found imbedded in this colluvial layer and demonstrates that colluviation associated with overland-flow during snowmelt occurred almost continuously since 7080 cal. BP. In the eastern
sector of town, the 1 to 4 meters thick colluviums cover till and a network of ice wedges that were revealed as spaced hyperbolic reflectors on GPR profiles. The colluviums also cover ice-rich marine silt and bedrock in the western sector of the
hamlet; marine shells found in a permafrost core yielded a radiocarbon date of 9553 cal. BP which provides a revised age for the local deglaciation and also a revised marine submergence limit.
Among the applied methods, shallow drilling in
coarse grained permafrost, core recovery and CT-Scan allowed the discovery of the importance of Holocene slope processes on shaping the surface of the terrain and leading to the observed cryostructures and ice contents in the near surface permafrost.
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| GEOSCAN ID | 290072 |
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