Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data
This paper presents the first integrated macroscale and microscale examination of subglacial till associated with the last‐glacial ( F raser G laciation) C ordilleran I ce S heet ( CIS ). A new statistical approach to quantifying till micromorphology (multivariate hierarchical cluster analysis for c...
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crwiley:10.1111/bor.12009 2024-09-15T18:12:33+00:00 Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data Neudorf, Christina M. Brennand, Tracy A. Lian, Olav B. 2013 http://dx.doi.org/10.1111/bor.12009 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fbor.12009 https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12009 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Boreas volume 42, issue 4, page 848-875 ISSN 0300-9483 1502-3885 journal-article 2013 crwiley https://doi.org/10.1111/bor.12009 2024-07-30T04:23:00Z This paper presents the first integrated macroscale and microscale examination of subglacial till associated with the last‐glacial ( F raser G laciation) C ordilleran I ce S heet ( CIS ). A new statistical approach to quantifying till micromorphology (multivariate hierarchical cluster analysis for compositional data) is also described and implemented. Till macrostructures, macrofabrics and microstructures support previous assertions that primary till in this region formed through a combination of lodgement and deformation processes in a temperate subglacial environment. Macroscale observations suggest that subglacial environments below the CIS were probably influenced by topography, whereby poor drainage of the substrate in topographically constricted areas, or on slopes adverse to the ice‐flow direction at glacial maximum, facilitated ductile deformation of the glacier bed. Microscale observations suggest that subglacial till below the CIS experienced both ductile and brittle deformation, including grain rotation and squeeze flow of sediment between grains under moist conditions, and microshearing, grain stacking and grain fracturing under well‐drained conditions. Macroscale observations suggest that ductile deformation events were probably followed by brittle deformation events as the substrate subsequently drained. The prevalence of ductile‐type microstructures in most till exposures investigated in this study suggests that ductile deformation signatures can be preserved at the microscale after brittle deformation events that result in larger‐scale fractures and shear structures. It is likely that microscale ductile deformation can also occur within distributed shear zones during lodgement processes. Cluster analysis of microstructure data and qualitative observations made from thin sections suggest that the relative frequency of countable microstructures in this till is influenced by topography in relation to ice‐flow direction (bed drainage conditions) as well as by the frequency and distribution of voids ... Article in Journal/Newspaper Ice Sheet Wiley Online Library Boreas n/a n/a |
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English |
description |
This paper presents the first integrated macroscale and microscale examination of subglacial till associated with the last‐glacial ( F raser G laciation) C ordilleran I ce S heet ( CIS ). A new statistical approach to quantifying till micromorphology (multivariate hierarchical cluster analysis for compositional data) is also described and implemented. Till macrostructures, macrofabrics and microstructures support previous assertions that primary till in this region formed through a combination of lodgement and deformation processes in a temperate subglacial environment. Macroscale observations suggest that subglacial environments below the CIS were probably influenced by topography, whereby poor drainage of the substrate in topographically constricted areas, or on slopes adverse to the ice‐flow direction at glacial maximum, facilitated ductile deformation of the glacier bed. Microscale observations suggest that subglacial till below the CIS experienced both ductile and brittle deformation, including grain rotation and squeeze flow of sediment between grains under moist conditions, and microshearing, grain stacking and grain fracturing under well‐drained conditions. Macroscale observations suggest that ductile deformation events were probably followed by brittle deformation events as the substrate subsequently drained. The prevalence of ductile‐type microstructures in most till exposures investigated in this study suggests that ductile deformation signatures can be preserved at the microscale after brittle deformation events that result in larger‐scale fractures and shear structures. It is likely that microscale ductile deformation can also occur within distributed shear zones during lodgement processes. Cluster analysis of microstructure data and qualitative observations made from thin sections suggest that the relative frequency of countable microstructures in this till is influenced by topography in relation to ice‐flow direction (bed drainage conditions) as well as by the frequency and distribution of voids ... |
format |
Article in Journal/Newspaper |
author |
Neudorf, Christina M. Brennand, Tracy A. Lian, Olav B. |
spellingShingle |
Neudorf, Christina M. Brennand, Tracy A. Lian, Olav B. Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
author_facet |
Neudorf, Christina M. Brennand, Tracy A. Lian, Olav B. |
author_sort |
Neudorf, Christina M. |
title |
Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
title_short |
Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
title_full |
Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
title_fullStr |
Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
title_full_unstemmed |
Till‐forming processes beneath parts of the Cordilleran Ice Sheet, British Columbia, Canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
title_sort |
till‐forming processes beneath parts of the cordilleran ice sheet, british columbia, canada: macroscale and microscale evidence and a new statistical technique for analysing microstructure data |
publisher |
Wiley |
publishDate |
2013 |
url |
http://dx.doi.org/10.1111/bor.12009 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fbor.12009 https://onlinelibrary.wiley.com/doi/pdf/10.1111/bor.12009 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_source |
Boreas volume 42, issue 4, page 848-875 ISSN 0300-9483 1502-3885 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1111/bor.12009 |
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Boreas |
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1810450131725582336 |