Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada
Abstract Investigations of glacial sediment exposures in a former open pit in the Pine Point Mining District, Northwest Territories, reveal evidence of changes in stress magnitude as exhibited by the movement of deformation ‘fronts’ within subglacial tills, as evident through micromorphological anal...
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ftdoajarticles:oai:doaj.org/article:293f506fdeff4a4bb7e71bf51849ea2f 2023-05-15T16:40:43+02:00 Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada John Menzies Roger C. Paulen Jessey M. Rice M. Beth McClenaghan Natasha M. Oviatt Nitasha Dhillon 2019-06-01T00:00:00Z https://doi.org/10.1002/dep2.73 https://doaj.org/article/293f506fdeff4a4bb7e71bf51849ea2f EN eng Wiley https://doi.org/10.1002/dep2.73 https://doaj.org/toc/2055-4877 2055-4877 doi:10.1002/dep2.73 https://doaj.org/article/293f506fdeff4a4bb7e71bf51849ea2f The Depositional Record, Vol 5, Iss 2, Pp 230-246 (2019) Canada deformation fronts glacial microsedimentology microstructures NWT Geology QE1-996.5 article 2019 ftdoajarticles https://doi.org/10.1002/dep2.73 2022-12-31T12:43:34Z Abstract Investigations of glacial sediment exposures in a former open pit in the Pine Point Mining District, Northwest Territories, reveal evidence of changes in stress magnitude as exhibited by the movement of deformation ‘fronts’ within subglacial tills, as evident through micromorphological analysis. Indications of deformation, driven by stress fluctuations, were observed throughout a set of vertical subglacial till samples associated with the Laurentide Ice Sheet. These tills exhibit multiple sub‐lithofacies variations in concert with marked changes in microshear orientation, which can be directly related to changing stress levels within a subglacial deforming bed. The evidence of changes in till stress conditions is typical of subglacial tills occurring beneath an active temperate ice mass within a soft deforming bed. As differing ‘layers’ of till that form a mosaic‐like pattern become immobilized and ‘detached’ subjacent to the deforming bed sediments, a signature of this action is recorded within the tills as sequences of specific microstructures. These microstructures are part of a spectrum of micro‐forms that develop as consequence of changes in stress, porewater content and clay content within the ‘fault‐gouge’—like environment formed beneath an active temperate ice sheet. A model is developed that uses data from Pit O‐28 demonstrating where deformation ‘boundary front’ evidence in the form of deformation bands has developed as basal driven stress levels have penetrated active deforming sediments. The evidence from Pine Point indicates that till acts as an excellent palaeo‐strain record of past active glacial processes, subglacial basal thermal conditions and sediment mobility. Article in Journal/Newspaper Ice Sheet Northwest Territories Directory of Open Access Journals: DOAJ Articles Northwest Territories Canada Pine Point ENVELOPE(-114.449,-114.449,60.834,60.834) The Depositional Record 5 2 230 246 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Canada deformation fronts glacial microsedimentology microstructures NWT Geology QE1-996.5 |
spellingShingle |
Canada deformation fronts glacial microsedimentology microstructures NWT Geology QE1-996.5 John Menzies Roger C. Paulen Jessey M. Rice M. Beth McClenaghan Natasha M. Oviatt Nitasha Dhillon Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
topic_facet |
Canada deformation fronts glacial microsedimentology microstructures NWT Geology QE1-996.5 |
description |
Abstract Investigations of glacial sediment exposures in a former open pit in the Pine Point Mining District, Northwest Territories, reveal evidence of changes in stress magnitude as exhibited by the movement of deformation ‘fronts’ within subglacial tills, as evident through micromorphological analysis. Indications of deformation, driven by stress fluctuations, were observed throughout a set of vertical subglacial till samples associated with the Laurentide Ice Sheet. These tills exhibit multiple sub‐lithofacies variations in concert with marked changes in microshear orientation, which can be directly related to changing stress levels within a subglacial deforming bed. The evidence of changes in till stress conditions is typical of subglacial tills occurring beneath an active temperate ice mass within a soft deforming bed. As differing ‘layers’ of till that form a mosaic‐like pattern become immobilized and ‘detached’ subjacent to the deforming bed sediments, a signature of this action is recorded within the tills as sequences of specific microstructures. These microstructures are part of a spectrum of micro‐forms that develop as consequence of changes in stress, porewater content and clay content within the ‘fault‐gouge’—like environment formed beneath an active temperate ice sheet. A model is developed that uses data from Pit O‐28 demonstrating where deformation ‘boundary front’ evidence in the form of deformation bands has developed as basal driven stress levels have penetrated active deforming sediments. The evidence from Pine Point indicates that till acts as an excellent palaeo‐strain record of past active glacial processes, subglacial basal thermal conditions and sediment mobility. |
format |
Article in Journal/Newspaper |
author |
John Menzies Roger C. Paulen Jessey M. Rice M. Beth McClenaghan Natasha M. Oviatt Nitasha Dhillon |
author_facet |
John Menzies Roger C. Paulen Jessey M. Rice M. Beth McClenaghan Natasha M. Oviatt Nitasha Dhillon |
author_sort |
John Menzies |
title |
Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
title_short |
Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
title_full |
Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
title_fullStr |
Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
title_full_unstemmed |
Deformation ‘boundary front’ movements in subglacial tills—A microsedimentological perspective from till sequences near Pine Point, NWT, Canada |
title_sort |
deformation ‘boundary front’ movements in subglacial tills—a microsedimentological perspective from till sequences near pine point, nwt, canada |
publisher |
Wiley |
publishDate |
2019 |
url |
https://doi.org/10.1002/dep2.73 https://doaj.org/article/293f506fdeff4a4bb7e71bf51849ea2f |
long_lat |
ENVELOPE(-114.449,-114.449,60.834,60.834) |
geographic |
Northwest Territories Canada Pine Point |
geographic_facet |
Northwest Territories Canada Pine Point |
genre |
Ice Sheet Northwest Territories |
genre_facet |
Ice Sheet Northwest Territories |
op_source |
The Depositional Record, Vol 5, Iss 2, Pp 230-246 (2019) |
op_relation |
https://doi.org/10.1002/dep2.73 https://doaj.org/toc/2055-4877 2055-4877 doi:10.1002/dep2.73 https://doaj.org/article/293f506fdeff4a4bb7e71bf51849ea2f |
op_doi |
https://doi.org/10.1002/dep2.73 |
container_title |
The Depositional Record |
container_volume |
5 |
container_issue |
2 |
container_start_page |
230 |
op_container_end_page |
246 |
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1766031130143752192 |