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No change in Southern Ocean circulation in the Indian Ocean from the Eocene through Late Oligocene

No change in Southern Ocean circulation in the Indian Ocean from the Eocene through Late Oligocene
No change in Southern Ocean circulation in the Indian Ocean from the Eocene through Late Oligocene

Deciphering the evolution of Southern Ocean circulation during the Eocene and Oligocene has important implications for understanding the development of the Antarctic Circumpolar Current and transition to Earth's "icehouse" climate. To better understand ocean circulation patterns in the Indian Ocean sector of the Southern Ocean, we generated a new fossil fish tooth neodymium isotope record (εNd) from the upper Eocene to upper Oligocene sections (36-23 Ma) of Ocean Drilling Program Sites 744 and 748 (Kerguelen Plateau, Indian Ocean). Reconstructed seawater εNd values from fossil fish teeth are used to trace changes in water masses across ocean basins. The records from Site 748 and Site 744 reveal a gradual shift from εNd values around -6.5 to -7.5 in the late Eocene to εNd values between -7.5 and -8.3 by the late Oligocene, consistent with a Circumpolar Deep Water (CDW) influence at the Kerguelen Plateau throughout the Oligocene. We interpret the shift to less radiogenic values to reflect the increased export of Northern Component Water to the Southern Ocean, likely into the proto-CDW. However, the records show no major change in water mass composition around the Kerguelen Plateau that would accompany an increase in Pacific throughflow related to the opening of Drake Passage and imply that Pacific throughflow via the Drake Passage occurred by the late Eocene. High-frequency variability in eNd values at Site 744 is interpreted as an imprint of Oligocene glacial activity, with a particularly pronounced excursion at 32.6 Ma roughly coinciding with other glacial weathering indicators around Antarctica.

Eocene-Oligocene transition, Kerguelen Plateau, Neodymium isotopes, Southern Ocean
2572-4525
Wright, Nicky M.
70d18346-3214-4e7c-97d5-818a0407d7ff
Scher, Howie D.
e8ccbb0d-3b13-449f-be6a-b3bdc0f19e08
Seton, Maria
84499ecf-4def-44e8-8cd4-2be4ce70c6e7
Huck, Claire E.
c11ab07a-a14f-4703-b914-8dbabb38839c
Duggan, Brian D.
26c98850-769f-44bd-9a63-053dc8372197
Wright, Nicky M.
70d18346-3214-4e7c-97d5-818a0407d7ff
Scher, Howie D.
e8ccbb0d-3b13-449f-be6a-b3bdc0f19e08
Seton, Maria
84499ecf-4def-44e8-8cd4-2be4ce70c6e7
Huck, Claire E.
c11ab07a-a14f-4703-b914-8dbabb38839c
Duggan, Brian D.
26c98850-769f-44bd-9a63-053dc8372197

Wright, Nicky M., Scher, Howie D., Seton, Maria, Huck, Claire E. and Duggan, Brian D. (2018) No change in Southern Ocean circulation in the Indian Ocean from the Eocene through Late Oligocene. Paleoceanography and Paleoclimatology. (doi:10.1002/2017PA003238).

Record type: Article

Abstract

Deciphering the evolution of Southern Ocean circulation during the Eocene and Oligocene has important implications for understanding the development of the Antarctic Circumpolar Current and transition to Earth's "icehouse" climate. To better understand ocean circulation patterns in the Indian Ocean sector of the Southern Ocean, we generated a new fossil fish tooth neodymium isotope record (εNd) from the upper Eocene to upper Oligocene sections (36-23 Ma) of Ocean Drilling Program Sites 744 and 748 (Kerguelen Plateau, Indian Ocean). Reconstructed seawater εNd values from fossil fish teeth are used to trace changes in water masses across ocean basins. The records from Site 748 and Site 744 reveal a gradual shift from εNd values around -6.5 to -7.5 in the late Eocene to εNd values between -7.5 and -8.3 by the late Oligocene, consistent with a Circumpolar Deep Water (CDW) influence at the Kerguelen Plateau throughout the Oligocene. We interpret the shift to less radiogenic values to reflect the increased export of Northern Component Water to the Southern Ocean, likely into the proto-CDW. However, the records show no major change in water mass composition around the Kerguelen Plateau that would accompany an increase in Pacific throughflow related to the opening of Drake Passage and imply that Pacific throughflow via the Drake Passage occurred by the late Eocene. High-frequency variability in eNd values at Site 744 is interpreted as an imprint of Oligocene glacial activity, with a particularly pronounced excursion at 32.6 Ma roughly coinciding with other glacial weathering indicators around Antarctica.

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Accepted/In Press date: 20 December 2017
e-pub ahead of print date: 5 February 2018
Keywords: Eocene-Oligocene transition, Kerguelen Plateau, Neodymium isotopes, Southern Ocean

Identifiers

Local EPrints ID: 418084
URI: http://eprints.soton.ac.uk/id/eprint/418084
ISSN: 2572-4525
PURE UUID: 68a03720-ec64-4093-8e63-d2ddd2c60e35

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Date deposited: 22 Feb 2018 17:30
Last modified: 28 Apr 2022 04:02

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Contributors

Author: Nicky M. Wright
Author: Howie D. Scher
Author: Maria Seton
Author: Claire E. Huck
Author: Brian D. Duggan

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