Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska
Thirty-seven tephra beds, primarily from coal partings in the Sterling and Beluga formations, were successfully dated by the 40 Ar/ 39 Ar method providing a new and revised understanding of the chronostratigraphy of late Tertiary strata within Cook Inlet Basin. Meticulous sample preparation, multipl...
Published in: | Canadian Journal of Earth Sciences |
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Format: | Article in Journal/Newspaper |
Language: | English |
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2004
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Online Access: | http://dx.doi.org/10.1139/e04-057 http://www.nrcresearchpress.com/doi/pdf/10.1139/e04-057 |
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crcansciencepubl:10.1139/e04-057 2024-09-30T14:33:01+00:00 Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska Dallegge, Todd A Layer, Paul W 2004 http://dx.doi.org/10.1139/e04-057 http://www.nrcresearchpress.com/doi/pdf/10.1139/e04-057 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 41, issue 10, page 1159-1179 ISSN 0008-4077 1480-3313 journal-article 2004 crcansciencepubl https://doi.org/10.1139/e04-057 2024-09-05T04:11:14Z Thirty-seven tephra beds, primarily from coal partings in the Sterling and Beluga formations, were successfully dated by the 40 Ar/ 39 Ar method providing a new and revised understanding of the chronostratigraphy of late Tertiary strata within Cook Inlet Basin. Meticulous sample preparation, multiple analyses, and statistical evaluation of the data were required for these low-K, plagioclase- and hornblende-bearing tephras. Dating of subsurface core material provides the first subsurface-to-outcrop tie in Cook Inlet between well 212-24 in the Beluga River Unit and deposits in the Clam Gulch, Diamond Creek, and Fox Creek areas. The new 40 Ar/ 39 Ar chronostratigraphic framework place the age of upper part of the Kenai Group strata between 4.6 and 9.4 Ma and support the 8-Ma interpretation of the boundary between the Homerian and Clamgulchian paleobotanical stages. The 49-Ma age from core data in Pioneer Unit suggests the Tyonek Formation is older than previously thought or that these units belong to an older formation. The chronostratigraphic framework demonstrates significant offset on faults along the Kenai Peninsula, the presence of faults in slumps and vegetated areas, disconformities in the stratigraphic succession, and that parts of the Sterling and Beluga formations are time-equivalent strata representing lateral facies variations. Based on crosscutting relations and structural folding, the established chronohorizons indicate that much of the structural deformation in Cook Inlet is no older than early Pliocene in age. The repeated section, due to faulting and the coeval nature of the formations, could significantly affect previous resource assessments of coal and hydrocarbon distributions. Article in Journal/Newspaper Beluga Beluga* Alaska Canadian Science Publishing Gulch ENVELOPE(-61.483,-61.483,-63.997,-63.997) Canadian Journal of Earth Sciences 41 10 1159 1179 |
institution |
Open Polar |
collection |
Canadian Science Publishing |
op_collection_id |
crcansciencepubl |
language |
English |
description |
Thirty-seven tephra beds, primarily from coal partings in the Sterling and Beluga formations, were successfully dated by the 40 Ar/ 39 Ar method providing a new and revised understanding of the chronostratigraphy of late Tertiary strata within Cook Inlet Basin. Meticulous sample preparation, multiple analyses, and statistical evaluation of the data were required for these low-K, plagioclase- and hornblende-bearing tephras. Dating of subsurface core material provides the first subsurface-to-outcrop tie in Cook Inlet between well 212-24 in the Beluga River Unit and deposits in the Clam Gulch, Diamond Creek, and Fox Creek areas. The new 40 Ar/ 39 Ar chronostratigraphic framework place the age of upper part of the Kenai Group strata between 4.6 and 9.4 Ma and support the 8-Ma interpretation of the boundary between the Homerian and Clamgulchian paleobotanical stages. The 49-Ma age from core data in Pioneer Unit suggests the Tyonek Formation is older than previously thought or that these units belong to an older formation. The chronostratigraphic framework demonstrates significant offset on faults along the Kenai Peninsula, the presence of faults in slumps and vegetated areas, disconformities in the stratigraphic succession, and that parts of the Sterling and Beluga formations are time-equivalent strata representing lateral facies variations. Based on crosscutting relations and structural folding, the established chronohorizons indicate that much of the structural deformation in Cook Inlet is no older than early Pliocene in age. The repeated section, due to faulting and the coeval nature of the formations, could significantly affect previous resource assessments of coal and hydrocarbon distributions. |
format |
Article in Journal/Newspaper |
author |
Dallegge, Todd A Layer, Paul W |
spellingShingle |
Dallegge, Todd A Layer, Paul W Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
author_facet |
Dallegge, Todd A Layer, Paul W |
author_sort |
Dallegge, Todd A |
title |
Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
title_short |
Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
title_full |
Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
title_fullStr |
Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
title_full_unstemmed |
Revised chronostratigraphy of the Kenai Group from 40 Ar/ 39 Ar dating of low-potassium bearing minerals, Cook Inlet Basin, Alaska |
title_sort |
revised chronostratigraphy of the kenai group from 40 ar/ 39 ar dating of low-potassium bearing minerals, cook inlet basin, alaska |
publisher |
Canadian Science Publishing |
publishDate |
2004 |
url |
http://dx.doi.org/10.1139/e04-057 http://www.nrcresearchpress.com/doi/pdf/10.1139/e04-057 |
long_lat |
ENVELOPE(-61.483,-61.483,-63.997,-63.997) |
geographic |
Gulch |
geographic_facet |
Gulch |
genre |
Beluga Beluga* Alaska |
genre_facet |
Beluga Beluga* Alaska |
op_source |
Canadian Journal of Earth Sciences volume 41, issue 10, page 1159-1179 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e04-057 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
41 |
container_issue |
10 |
container_start_page |
1159 |
op_container_end_page |
1179 |
_version_ |
1811637051836071936 |