Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic

High-precision strontium (Sr) isotopic measurements were obtained for 53 Pliocene and Pleistocene molluscan shells from emerged marine deposits around the coasts of Arctic North America to test whether such data can be used for chronostratigraphic purposes. 87 Sr/ 86 Sr ratios from Sr isotopic measu...

Full description

Bibliographic Details
Published in:Canadian Journal of Earth Sciences
Main Authors: Kaufman, Darrell, Carter, L. David, Miller, Gifford H., Farmer, G. Lang, Budd, David A.
Format: Article in Journal/Newspaper
Language:English
Published: Canadian Science Publishing 1993
Subjects:
Online Access:http://dx.doi.org/10.1139/e93-041
http://www.nrcresearchpress.com/doi/pdf/10.1139/e93-041
id crcansciencepubl:10.1139/e93-041
record_format openpolar
spelling crcansciencepubl:10.1139/e93-041 2023-12-17T10:25:11+01:00 Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic Kaufman, Darrell Carter, L. David Miller, Gifford H. Farmer, G. Lang Budd, David A. 1993 http://dx.doi.org/10.1139/e93-041 http://www.nrcresearchpress.com/doi/pdf/10.1139/e93-041 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 30, issue 3, page 519-534 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1993 crcansciencepubl https://doi.org/10.1139/e93-041 2023-11-19T13:38:46Z High-precision strontium (Sr) isotopic measurements were obtained for 53 Pliocene and Pleistocene molluscan shells from emerged marine deposits around the coasts of Arctic North America to test whether such data can be used for chronostratigraphic purposes. 87 Sr/ 86 Sr ratios from Sr isotopic measurements on many marine fossils from Arctic Ocean borderland sites are broadly consistent with their expected values based on independent age control and on a comparison with the Sr isotopic evolution of seawater recorded in deep-sea cores. All 87 Sr/ 86 Sr ratios measured for shells from Middle and Late Pleistocene deposits are consistent with expected values, but only 9 of 22 ratios in shells from older deposits are consistent with independent age estimates. Aberrant 87 Sr/ 86 Sr ratios are consistently higher than expected. At Nome, Alaska, and Baffin Island, Canada, all 87 Sr/ 86 Sr ratios are higher than expected. Because these shells were formed along the Pacific Ocean and Atlantic Ocean margins, respectively, their high 87 Sr/ 86 Sr ratios cannot be attributed to possible differences in the Sr isotopic evolution of the Arctic Ocean relative to that of remainder of the world's oceans. Radiogenic Sr from proximal river-water input, or leaching of detritus within the shell matrix, may have changed the 87 Sr/ 86 Sr ratios by as much as about 5 × 10 −5 , but these mechanisms cannot account for the very high 87 Sr/ 86 Sr values (from 20 × 10 −5 to 200 × 10 −5 higher than those of modern seawater) measured for some shells. Alteration by diagenetic fluids rich in radiogenic Sr is the most plausible explanation for the aberrant results. Diagenesis is recognized petrographically in the most altered shells by micritic overprinting of the original shell microstructure; in addition, one shell enriched in 87 Sr from Baffin Island exhibits a broad range (170 × 10 −5 ) of 87 Sr/ 86 Sr ratios across the shell, and an oxygen isotopic gradient (l.6‰) that is greater than the expected primary variability. Although our data suggest ... Article in Journal/Newspaper Arctic Arctic Ocean Baffin Island Baffin Nome Alaska Canadian Science Publishing (via Crossref) Arctic Arctic Ocean Baffin Island Canada Pacific Canadian Journal of Earth Sciences 30 3 519 534
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
Kaufman, Darrell
Carter, L. David
Miller, Gifford H.
Farmer, G. Lang
Budd, David A.
Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
topic_facet General Earth and Planetary Sciences
description High-precision strontium (Sr) isotopic measurements were obtained for 53 Pliocene and Pleistocene molluscan shells from emerged marine deposits around the coasts of Arctic North America to test whether such data can be used for chronostratigraphic purposes. 87 Sr/ 86 Sr ratios from Sr isotopic measurements on many marine fossils from Arctic Ocean borderland sites are broadly consistent with their expected values based on independent age control and on a comparison with the Sr isotopic evolution of seawater recorded in deep-sea cores. All 87 Sr/ 86 Sr ratios measured for shells from Middle and Late Pleistocene deposits are consistent with expected values, but only 9 of 22 ratios in shells from older deposits are consistent with independent age estimates. Aberrant 87 Sr/ 86 Sr ratios are consistently higher than expected. At Nome, Alaska, and Baffin Island, Canada, all 87 Sr/ 86 Sr ratios are higher than expected. Because these shells were formed along the Pacific Ocean and Atlantic Ocean margins, respectively, their high 87 Sr/ 86 Sr ratios cannot be attributed to possible differences in the Sr isotopic evolution of the Arctic Ocean relative to that of remainder of the world's oceans. Radiogenic Sr from proximal river-water input, or leaching of detritus within the shell matrix, may have changed the 87 Sr/ 86 Sr ratios by as much as about 5 × 10 −5 , but these mechanisms cannot account for the very high 87 Sr/ 86 Sr values (from 20 × 10 −5 to 200 × 10 −5 higher than those of modern seawater) measured for some shells. Alteration by diagenetic fluids rich in radiogenic Sr is the most plausible explanation for the aberrant results. Diagenesis is recognized petrographically in the most altered shells by micritic overprinting of the original shell microstructure; in addition, one shell enriched in 87 Sr from Baffin Island exhibits a broad range (170 × 10 −5 ) of 87 Sr/ 86 Sr ratios across the shell, and an oxygen isotopic gradient (l.6‰) that is greater than the expected primary variability. Although our data suggest ...
format Article in Journal/Newspaper
author Kaufman, Darrell
Carter, L. David
Miller, Gifford H.
Farmer, G. Lang
Budd, David A.
author_facet Kaufman, Darrell
Carter, L. David
Miller, Gifford H.
Farmer, G. Lang
Budd, David A.
author_sort Kaufman, Darrell
title Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
title_short Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
title_full Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
title_fullStr Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
title_full_unstemmed Strontium isotopic composition of Pliocene and Pleistocene molluscs from emerged marine deposits, North American Arctic
title_sort strontium isotopic composition of pliocene and pleistocene molluscs from emerged marine deposits, north american arctic
publisher Canadian Science Publishing
publishDate 1993
url http://dx.doi.org/10.1139/e93-041
http://www.nrcresearchpress.com/doi/pdf/10.1139/e93-041
geographic Arctic
Arctic Ocean
Baffin Island
Canada
Pacific
geographic_facet Arctic
Arctic Ocean
Baffin Island
Canada
Pacific
genre Arctic
Arctic Ocean
Baffin Island
Baffin
Nome
Alaska
genre_facet Arctic
Arctic Ocean
Baffin Island
Baffin
Nome
Alaska
op_source Canadian Journal of Earth Sciences
volume 30, issue 3, page 519-534
ISSN 0008-4077 1480-3313
op_rights http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining
op_doi https://doi.org/10.1139/e93-041
container_title Canadian Journal of Earth Sciences
container_volume 30
container_issue 3
container_start_page 519
op_container_end_page 534
_version_ 1785574139620229120