Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada
The structural geology of the northeastern Paleoproterozoic Amer belt, central Nunavut, has been evaluated in light of new field mapping combined with legacy data and independently acquired subsurface geophysics data. Proterozoic sequences Ps1–Ps4 of the Amer supergroup unconformably overlie Archean...
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crcansciencepubl:10.1139/cjes-2022-0083 2023-12-17T10:47:44+01:00 Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada White, Joseph Clancy Calhoun, Lydia Jefferson, Charles W. 2023 http://dx.doi.org/10.1139/cjes-2022-0083 https://cdnsciencepub.com/doi/full-xml/10.1139/cjes-2022-0083 https://cdnsciencepub.com/doi/pdf/10.1139/cjes-2022-0083 en eng Canadian Science Publishing https://creativecommons.org/licenses/by/4.0/deed.en_GB Canadian Journal of Earth Sciences volume 60, issue 7, page 1078-1103 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 2023 crcansciencepubl https://doi.org/10.1139/cjes-2022-0083 2023-11-19T13:39:10Z The structural geology of the northeastern Paleoproterozoic Amer belt, central Nunavut, has been evaluated in light of new field mapping combined with legacy data and independently acquired subsurface geophysics data. Proterozoic sequences Ps1–Ps4 of the Amer supergroup unconformably overlie Archean basement. Of these sequences, Ps1–Ps3 have been intensely deformed (D 1 ) in association with the Snowbird Orogeny (2.05–1.865 Ga). Ps4 was deposited unconformably on the first three sequences and exhibits none of the D 1 effects. Deformation within Ps4 is slight compared to the underlying sequences and is restricted to D 2 folding that occurred in the 1.84–1.81 Ga Hudsonian Orogeny. Deformation of sequences Ps1–Ps3 forms the core of this study. D 1 comprises imbricate thrusting, intersequence detachment, and three generations of isoclinal folding and transposition. The stratigraphic order is maintained in many areas by decoupling of sequence packages along incompetent units so as not to “mix” lithologies; there is a fundamental mechanical stratigraphy. Within sequences, transposition can be otherwise intense. The resultant architecture is a shallowly southwest-dipping sequence of tectonically rotated and transposed layering (primary and tectonic) similar in many ways in orientation regardless of whether preserved with original bedding features or completely transposed. D 1 folding is characterized by recumbent folds, noncylindrical folds that are sometimes rooted in detachments, verging to the northeast. D 2 folding is controlled by the pre-existing large-scale D 1 fabric, resulting in the overturned synforms that parallel the belt. Post-D 2 fault modification of northern side of the belt along northwest-trending faults is interpreted to relate to extension and exhumation. Article in Journal/Newspaper Nunavut Canadian Science Publishing (via Crossref) Nunavut Canada Canadian Journal of Earth Sciences 60 7 1078 1103 |
institution |
Open Polar |
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Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences White, Joseph Clancy Calhoun, Lydia Jefferson, Charles W. Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
topic_facet |
General Earth and Planetary Sciences |
description |
The structural geology of the northeastern Paleoproterozoic Amer belt, central Nunavut, has been evaluated in light of new field mapping combined with legacy data and independently acquired subsurface geophysics data. Proterozoic sequences Ps1–Ps4 of the Amer supergroup unconformably overlie Archean basement. Of these sequences, Ps1–Ps3 have been intensely deformed (D 1 ) in association with the Snowbird Orogeny (2.05–1.865 Ga). Ps4 was deposited unconformably on the first three sequences and exhibits none of the D 1 effects. Deformation within Ps4 is slight compared to the underlying sequences and is restricted to D 2 folding that occurred in the 1.84–1.81 Ga Hudsonian Orogeny. Deformation of sequences Ps1–Ps3 forms the core of this study. D 1 comprises imbricate thrusting, intersequence detachment, and three generations of isoclinal folding and transposition. The stratigraphic order is maintained in many areas by decoupling of sequence packages along incompetent units so as not to “mix” lithologies; there is a fundamental mechanical stratigraphy. Within sequences, transposition can be otherwise intense. The resultant architecture is a shallowly southwest-dipping sequence of tectonically rotated and transposed layering (primary and tectonic) similar in many ways in orientation regardless of whether preserved with original bedding features or completely transposed. D 1 folding is characterized by recumbent folds, noncylindrical folds that are sometimes rooted in detachments, verging to the northeast. D 2 folding is controlled by the pre-existing large-scale D 1 fabric, resulting in the overturned synforms that parallel the belt. Post-D 2 fault modification of northern side of the belt along northwest-trending faults is interpreted to relate to extension and exhumation. |
format |
Article in Journal/Newspaper |
author |
White, Joseph Clancy Calhoun, Lydia Jefferson, Charles W. |
author_facet |
White, Joseph Clancy Calhoun, Lydia Jefferson, Charles W. |
author_sort |
White, Joseph Clancy |
title |
Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
title_short |
Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
title_full |
Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
title_fullStr |
Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
title_full_unstemmed |
Paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern Paleoproterozoic Amer belt, Nunavut, Canada |
title_sort |
paradoxical mid-crustal displacements and stratigraphic continuity: structural evolution of the northeastern paleoproterozoic amer belt, nunavut, canada |
publisher |
Canadian Science Publishing |
publishDate |
2023 |
url |
http://dx.doi.org/10.1139/cjes-2022-0083 https://cdnsciencepub.com/doi/full-xml/10.1139/cjes-2022-0083 https://cdnsciencepub.com/doi/pdf/10.1139/cjes-2022-0083 |
geographic |
Nunavut Canada |
geographic_facet |
Nunavut Canada |
genre |
Nunavut |
genre_facet |
Nunavut |
op_source |
Canadian Journal of Earth Sciences volume 60, issue 7, page 1078-1103 ISSN 0008-4077 1480-3313 |
op_rights |
https://creativecommons.org/licenses/by/4.0/deed.en_GB |
op_doi |
https://doi.org/10.1139/cjes-2022-0083 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
60 |
container_issue |
7 |
container_start_page |
1078 |
op_container_end_page |
1103 |
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1785571693722337280 |