Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska
We present an apatite fission-track (AFT) study of five plutonic rocks and seven metamorphic rocks across 310 km of the YukonTanana Upland in east-central Alaska. Samples yielding ~40 Ma AFT ages and mean confined track lengths > 14 µm with low standard deviations cooled rapidly from >...
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crcansciencepubl:10.1139/e01-015 2023-12-17T10:51:35+01:00 Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska Dusel-Bacon, Cynthia Murphy, John M 2001 http://dx.doi.org/10.1139/e01-015 http://www.nrcresearchpress.com/doi/pdf/10.1139/e01-015 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 38, issue 8, page 1191-1204 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 2001 crcansciencepubl https://doi.org/10.1139/e01-015 2023-11-19T13:38:51Z We present an apatite fission-track (AFT) study of five plutonic rocks and seven metamorphic rocks across 310 km of the YukonTanana Upland in east-central Alaska. Samples yielding ~40 Ma AFT ages and mean confined track lengths > 14 µm with low standard deviations cooled rapidly from >120°C to <50°C during a 35 Ma period, beginning at about 40 Ma. Data from samples yielding AFT ages >40 Ma suggest partial annealing and, therefore, lower maximum temperatures (~90105°C). A few samples with single-grain ages of ~20 Ma apparently remained above ~50°C after initial cooling. Although the present geothermal gradient in the western YukonTanana Upland is ~32°C/km, it could have been as high as 45°C/km during a widespread Eocene intraplate magmatic episode. Prior to rapid exhumation, samples with ~40 Ma AFT ages were >3.82.7 km deep and samples with >50 Ma AFT ages were >3.32.0 km deep. We calculate a 440320 m/Ma minimum rate for exhumation of all samples during rapid cooling. Our AFT data, and data from rocks north of Fairbanks and from the Eielson deep test hole, indicate up to 3 km of post-40 Ma vertical displacement along known and inferred northeast-trending high-angle faults. The predominance of 4050 Ma AFT ages throughout the YukonTanana Upland indicates that, prior to the post-40 Ma relative uplift along some northeast-trending faults, rapid regional cooling and exhumation closely followed the Eocene extensional magmatism. We propose that Eocene magmatism and exhumation were somehow related to plate movements that produced regional-scale oroclinal rotation, northward translation of outboard terranes, major dextral strike-slip faulting, and subduction of an oceanic spreading ridge along the southern margin of Alaska. Article in Journal/Newspaper Alaska Yukon Canadian Science Publishing (via Crossref) Yukon Fairbanks Eielson ENVELOPE(-61.500,-61.500,-70.583,-70.583) Canadian Journal of Earth Sciences 38 8 1191 1204 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences Dusel-Bacon, Cynthia Murphy, John M Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
topic_facet |
General Earth and Planetary Sciences |
description |
We present an apatite fission-track (AFT) study of five plutonic rocks and seven metamorphic rocks across 310 km of the YukonTanana Upland in east-central Alaska. Samples yielding ~40 Ma AFT ages and mean confined track lengths > 14 µm with low standard deviations cooled rapidly from >120°C to <50°C during a 35 Ma period, beginning at about 40 Ma. Data from samples yielding AFT ages >40 Ma suggest partial annealing and, therefore, lower maximum temperatures (~90105°C). A few samples with single-grain ages of ~20 Ma apparently remained above ~50°C after initial cooling. Although the present geothermal gradient in the western YukonTanana Upland is ~32°C/km, it could have been as high as 45°C/km during a widespread Eocene intraplate magmatic episode. Prior to rapid exhumation, samples with ~40 Ma AFT ages were >3.82.7 km deep and samples with >50 Ma AFT ages were >3.32.0 km deep. We calculate a 440320 m/Ma minimum rate for exhumation of all samples during rapid cooling. Our AFT data, and data from rocks north of Fairbanks and from the Eielson deep test hole, indicate up to 3 km of post-40 Ma vertical displacement along known and inferred northeast-trending high-angle faults. The predominance of 4050 Ma AFT ages throughout the YukonTanana Upland indicates that, prior to the post-40 Ma relative uplift along some northeast-trending faults, rapid regional cooling and exhumation closely followed the Eocene extensional magmatism. We propose that Eocene magmatism and exhumation were somehow related to plate movements that produced regional-scale oroclinal rotation, northward translation of outboard terranes, major dextral strike-slip faulting, and subduction of an oceanic spreading ridge along the southern margin of Alaska. |
format |
Article in Journal/Newspaper |
author |
Dusel-Bacon, Cynthia Murphy, John M |
author_facet |
Dusel-Bacon, Cynthia Murphy, John M |
author_sort |
Dusel-Bacon, Cynthia |
title |
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
title_short |
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
title_full |
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
title_fullStr |
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
title_full_unstemmed |
Apatite fission-track evidence of widespread Eocene heating and exhumation in the Yukon-Tanana Upland, interior Alaska |
title_sort |
apatite fission-track evidence of widespread eocene heating and exhumation in the yukon-tanana upland, interior alaska |
publisher |
Canadian Science Publishing |
publishDate |
2001 |
url |
http://dx.doi.org/10.1139/e01-015 http://www.nrcresearchpress.com/doi/pdf/10.1139/e01-015 |
long_lat |
ENVELOPE(-61.500,-61.500,-70.583,-70.583) |
geographic |
Yukon Fairbanks Eielson |
geographic_facet |
Yukon Fairbanks Eielson |
genre |
Alaska Yukon |
genre_facet |
Alaska Yukon |
op_source |
Canadian Journal of Earth Sciences volume 38, issue 8, page 1191-1204 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e01-015 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
38 |
container_issue |
8 |
container_start_page |
1191 |
op_container_end_page |
1204 |
_version_ |
1785576879643688960 |