Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska
The rocks of southwestern Umnak Island (Nikolski area) consist mainly of a slightly deformed marine sedimentary sequence intruded by hypabyssal quartz diorite sills and small plutons. Laminated and thin-bedded argillaceous and tuffaceous mudstone and siltstone reflect volcanic arc sedimentation from...
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1984
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crcansciencepubl:10.1139/e84-018 2023-12-17T10:22:39+01:00 Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska McLean, Hugh Hein, J. R. 1984 http://dx.doi.org/10.1139/e84-018 http://www.nrcresearchpress.com/doi/pdf/10.1139/e84-018 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 21, issue 2, page 171-180 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1984 crcansciencepubl https://doi.org/10.1139/e84-018 2023-11-19T13:39:07Z The rocks of southwestern Umnak Island (Nikolski area) consist mainly of a slightly deformed marine sedimentary sequence intruded by hypabyssal quartz diorite sills and small plutons. Laminated and thin-bedded argillaceous and tuffaceous mudstone and siltstone reflect volcanic arc sedimentation from late Eocene to early Oligocene time. Zeolite facies minerals formed during diagenesis include heulandite, analcime, quartz, chlorite, and smectite. Radiometric dates from sill rock and plutons yield apparent ages of about 30 Ma, i.e, middle Oligocene. Chemical data from igneous rocks exhibit calc-alkaline and tholeiitic volcanic arc differentiation trends. Dikes of pyroxene basalt yield K/Ar apparent ages as old at 17 Ma, and a columnar-jointed plug of pyroxene basalt is as young as 1 Ma. The fossil ages and radiometric dates from southwestern Umnak Island are similar to those reported from other central and eastern Aleutian islands, and indicate uniformity in the chronology and tectonic development of the archipelago during the Paleogene. Paleomagnetic data suggest possible northward movement but remain equivocal and more work is indicated. Article in Journal/Newspaper Archipelago Alaska Aleutian Islands Canadian Science Publishing (via Crossref) Canadian Journal of Earth Sciences 21 2 171 180 |
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Open Polar |
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Canadian Science Publishing (via Crossref) |
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crcansciencepubl |
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English |
topic |
General Earth and Planetary Sciences |
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General Earth and Planetary Sciences McLean, Hugh Hein, J. R. Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
topic_facet |
General Earth and Planetary Sciences |
description |
The rocks of southwestern Umnak Island (Nikolski area) consist mainly of a slightly deformed marine sedimentary sequence intruded by hypabyssal quartz diorite sills and small plutons. Laminated and thin-bedded argillaceous and tuffaceous mudstone and siltstone reflect volcanic arc sedimentation from late Eocene to early Oligocene time. Zeolite facies minerals formed during diagenesis include heulandite, analcime, quartz, chlorite, and smectite. Radiometric dates from sill rock and plutons yield apparent ages of about 30 Ma, i.e, middle Oligocene. Chemical data from igneous rocks exhibit calc-alkaline and tholeiitic volcanic arc differentiation trends. Dikes of pyroxene basalt yield K/Ar apparent ages as old at 17 Ma, and a columnar-jointed plug of pyroxene basalt is as young as 1 Ma. The fossil ages and radiometric dates from southwestern Umnak Island are similar to those reported from other central and eastern Aleutian islands, and indicate uniformity in the chronology and tectonic development of the archipelago during the Paleogene. Paleomagnetic data suggest possible northward movement but remain equivocal and more work is indicated. |
format |
Article in Journal/Newspaper |
author |
McLean, Hugh Hein, J. R. |
author_facet |
McLean, Hugh Hein, J. R. |
author_sort |
McLean, Hugh |
title |
Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
title_short |
Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
title_full |
Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
title_fullStr |
Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
title_full_unstemmed |
Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska |
title_sort |
paleogene geology and chronology of southwestern umnak island, aleutian islands, alaska |
publisher |
Canadian Science Publishing |
publishDate |
1984 |
url |
http://dx.doi.org/10.1139/e84-018 http://www.nrcresearchpress.com/doi/pdf/10.1139/e84-018 |
genre |
Archipelago Alaska Aleutian Islands |
genre_facet |
Archipelago Alaska Aleutian Islands |
op_source |
Canadian Journal of Earth Sciences volume 21, issue 2, page 171-180 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e84-018 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
21 |
container_issue |
2 |
container_start_page |
171 |
op_container_end_page |
180 |
_version_ |
1785551081303965696 |