Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica
A 58 m long azimuthally oriented ice core has been collected from the floating lateral sinistral shear margin of the lower Priestley Glacier, Terra Nova Bay, Antarctica. The crystallographic preferred orientations (CPO) and microstructures are described in order to correlate the geometry of anisotro...
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Online Access: | http://dx.doi.org/10.3389/feart.2021.702213 https://www.frontiersin.org/articles/10.3389/feart.2021.702213/full |
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crfrontiers:10.3389/feart.2021.702213 2024-09-15T17:43:25+00:00 Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica Thomas, Rilee E. Negrini, Marianne Prior, David J. Mulvaney, Robert Still, Holly Bowman, M. Hamish Craw, Lisa Fan, Sheng Hubbard, Bryn Hulbe, Christina Kim, Daeyeong Lutz, Franz Marsden Fund Korea Polar Research Institute 2021 http://dx.doi.org/10.3389/feart.2021.702213 https://www.frontiersin.org/articles/10.3389/feart.2021.702213/full unknown Frontiers Media SA https://creativecommons.org/licenses/by/4.0/ Frontiers in Earth Science volume 9 ISSN 2296-6463 journal-article 2021 crfrontiers https://doi.org/10.3389/feart.2021.702213 2024-08-13T04:04:24Z A 58 m long azimuthally oriented ice core has been collected from the floating lateral sinistral shear margin of the lower Priestley Glacier, Terra Nova Bay, Antarctica. The crystallographic preferred orientations (CPO) and microstructures are described in order to correlate the geometry of anisotropy with constrained large-scale kinematics. Cryogenic Electron Backscatter Diffraction analysis shows a very strong fabric ( c -axis primary eigenvalue ∼0.9) with c -axes aligned horizontally sub-perpendicular to flow, rotating nearly 40° clockwise (looking down) to the pole to shear throughout the core. The c -axis maximum is sub-perpendicular to vertical layers, with the pole to layering always clockwise of the c -axes. Priestley ice microstructures are defined by largely sub-polygonal grains and constant mean grain sizes with depth. Grain long axis shape preferred orientations (SPO) are almost always 1–20° clockwise of the c -axis maximum. A minor proportion of “oddly” oriented grains that are distinct from the main c -axis maximum, are present in some samples. These have horizontal c -axes rotated clockwise from the primary c -axis maximum and may define a weaker secondary maximum up to 30° clockwise of the primary maximum. Intragranular misorientations are measured along the core, and although the statistics are weak, this could suggest recrystallization by subgrain rotation to occur. These microstructures suggest subgrain rotation (SGR) and recrystallization by grain boundary migration recrystallization (GBM) are active in the Priestley Glacier shear margin. Vorticity analysis based on intragranular distortion indicates a vertical axis of rotation in the shear margin. The variability in c -axis maximum orientation with depth indicates the structural heterogeneity of the Priestley Glacier shear margin occurs at the meter to tens of meters scale. We suggest that CPO rotations could relate to rigid rotation of blocks of ice within the glacial shear margin. Rotation either post-dates CPO and SPO development or is ... Article in Journal/Newspaper Antarc* Antarctica ice core Priestley Glacier Frontiers (Publisher) Frontiers in Earth Science 9 |
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Frontiers (Publisher) |
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crfrontiers |
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unknown |
description |
A 58 m long azimuthally oriented ice core has been collected from the floating lateral sinistral shear margin of the lower Priestley Glacier, Terra Nova Bay, Antarctica. The crystallographic preferred orientations (CPO) and microstructures are described in order to correlate the geometry of anisotropy with constrained large-scale kinematics. Cryogenic Electron Backscatter Diffraction analysis shows a very strong fabric ( c -axis primary eigenvalue ∼0.9) with c -axes aligned horizontally sub-perpendicular to flow, rotating nearly 40° clockwise (looking down) to the pole to shear throughout the core. The c -axis maximum is sub-perpendicular to vertical layers, with the pole to layering always clockwise of the c -axes. Priestley ice microstructures are defined by largely sub-polygonal grains and constant mean grain sizes with depth. Grain long axis shape preferred orientations (SPO) are almost always 1–20° clockwise of the c -axis maximum. A minor proportion of “oddly” oriented grains that are distinct from the main c -axis maximum, are present in some samples. These have horizontal c -axes rotated clockwise from the primary c -axis maximum and may define a weaker secondary maximum up to 30° clockwise of the primary maximum. Intragranular misorientations are measured along the core, and although the statistics are weak, this could suggest recrystallization by subgrain rotation to occur. These microstructures suggest subgrain rotation (SGR) and recrystallization by grain boundary migration recrystallization (GBM) are active in the Priestley Glacier shear margin. Vorticity analysis based on intragranular distortion indicates a vertical axis of rotation in the shear margin. The variability in c -axis maximum orientation with depth indicates the structural heterogeneity of the Priestley Glacier shear margin occurs at the meter to tens of meters scale. We suggest that CPO rotations could relate to rigid rotation of blocks of ice within the glacial shear margin. Rotation either post-dates CPO and SPO development or is ... |
author2 |
Marsden Fund Korea Polar Research Institute |
format |
Article in Journal/Newspaper |
author |
Thomas, Rilee E. Negrini, Marianne Prior, David J. Mulvaney, Robert Still, Holly Bowman, M. Hamish Craw, Lisa Fan, Sheng Hubbard, Bryn Hulbe, Christina Kim, Daeyeong Lutz, Franz |
spellingShingle |
Thomas, Rilee E. Negrini, Marianne Prior, David J. Mulvaney, Robert Still, Holly Bowman, M. Hamish Craw, Lisa Fan, Sheng Hubbard, Bryn Hulbe, Christina Kim, Daeyeong Lutz, Franz Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
author_facet |
Thomas, Rilee E. Negrini, Marianne Prior, David J. Mulvaney, Robert Still, Holly Bowman, M. Hamish Craw, Lisa Fan, Sheng Hubbard, Bryn Hulbe, Christina Kim, Daeyeong Lutz, Franz |
author_sort |
Thomas, Rilee E. |
title |
Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
title_short |
Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
title_full |
Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
title_fullStr |
Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
title_full_unstemmed |
Microstructure and Crystallographic Preferred Orientations of an Azimuthally Oriented Ice Core from a Lateral Shear Margin: Priestley Glacier, Antarctica |
title_sort |
microstructure and crystallographic preferred orientations of an azimuthally oriented ice core from a lateral shear margin: priestley glacier, antarctica |
publisher |
Frontiers Media SA |
publishDate |
2021 |
url |
http://dx.doi.org/10.3389/feart.2021.702213 https://www.frontiersin.org/articles/10.3389/feart.2021.702213/full |
genre |
Antarc* Antarctica ice core Priestley Glacier |
genre_facet |
Antarc* Antarctica ice core Priestley Glacier |
op_source |
Frontiers in Earth Science volume 9 ISSN 2296-6463 |
op_rights |
https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.3389/feart.2021.702213 |
container_title |
Frontiers in Earth Science |
container_volume |
9 |
_version_ |
1810490396731506688 |