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Sea-level and surface-water change in the western North Atlantic across the Oligocene–Miocene Transition: A palynological perspective from IODP Site U1406 (Newfoundland margin)

Sea-level and surface-water change in the western North Atlantic across the Oligocene–Miocene Transition: A palynological perspective from IODP Site U1406 (Newfoundland margin)
Sea-level and surface-water change in the western North Atlantic across the Oligocene–Miocene Transition: A palynological perspective from IODP Site U1406 (Newfoundland margin)
The Oligocene–Miocene transition (OMT; ~ 23.1 Ma) terminates the late Oligocene warming trend and is marked by a transient, large-amplitude expansion of Antarctic ice sheets. The associated glacial maximum, which is expressed by a ~ 1‰ positive shift in benthic foraminiferal oxygen-isotope values, is commonly referred to as the ‘Mi-1 isotope event’. Whereas the causes for the glacial maximum at the OMT are intrinsically connected to Southern Hemisphere ice-sheet dynamics, the behavior of the surface ocean in the Northern Hemisphere during this time is poorly known. To contribute to a better understanding of the paleoceanographic evolution during the OMT in the higher-latitude North Atlantic, we have analysed both marine and terrestrial palynomorphs from Integrated Ocean Drilling Program (IODP) Site U1406 offshore Newfoundland; this site has yielded a complete OMT section and exhibits a high-quality magnetostratigraphy that provides precise age control and allows reliable correlation to other records beyond Newfoundland. Our palynological data, which span the interval from 23.3 to 22.5 Ma and have a mean temporal resolution of 11.9 kyrs, show strong ~ 110-kyr eccentricity-paced oscillations during the earliest Miocene; these oscillations are in phase with similar cyclicity identified in previously published benthic foraminiferal oxygen-isotope records. More specifically, a pronounced sea-level variability is documented by the abundances of neritic dinoflagellate cysts (dinocysts) and terrigenous palynomorphs, which both reach maxima during peak glacial intervals as inferred from previously published South Atlantic benthic oxygen-isotope data. A decline in the abundance of warmer-water dinocysts suggests a surface-water cooling offshore Newfoundland from the latest Oligocene onwards. Surface-water productivity (as derived from the ratio between heterotrophic and autotrophic dinocysts) remained generally low throughout the studied interval. Notably, this ratio does not exhibit any correlation with changes in surface-water temperature, which is estimated from the ratio of warm-water over cold-water dinocysts. Together with the consistently low surface-water productivity, the lack of a correlation between surface-water productivity and temperature makes it highly unlikely that the observed paleoceanographic change was caused by a southward migration of the Arctic Front. Instead, we argue that our data may document an enhanced influence of the (Proto-) Labrador Current on surface waters offshore Newfoundland during the earliest Miocene that suppressed the influence of the Gulf Stream in this region of the Northwest Atlantic. We speculate that the enhanced influence of the (Proto-) Labrador Current was triggered by cooling of the northern hemisphere and possibly modulated by high-latitude sea-ice expansion.
0377-8398
57-71
Egger, Lisa M.
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Bahr, André
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Friedrich, Oliver
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Wilson, Paul A.
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Norris, Richard D.
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Van Peer, Tim E.
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Lippert, Peter C.
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Liebrand, Diederik
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Pross, Jörg
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Egger, Lisa M.
6fc5b4c3-694b-4532-8284-9ba107e4645e
Bahr, André
ff113c9b-74d3-40e1-ba22-0ddb05ffda5e
Friedrich, Oliver
680f066c-a4b1-4647-beb3-281addc1ee17
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Norris, Richard D.
9e0dfa1e-0c69-4666-bbf9-a5a14909d8f9
Van Peer, Tim E.
a0cd6c0c-54ff-4712-b861-76c90df08b66
Lippert, Peter C.
65409dec-6fd8-455e-8e4a-225dba999ce6
Liebrand, Diederik
e89fd857-7eef-4d88-b9ed-7c2931ee65e7
Pross, Jörg
7c848424-852f-467b-90f0-19d4f8d4ae01

Egger, Lisa M., Bahr, André, Friedrich, Oliver, Wilson, Paul A., Norris, Richard D., Van Peer, Tim E., Lippert, Peter C., Liebrand, Diederik and Pross, Jörg (2018) Sea-level and surface-water change in the western North Atlantic across the Oligocene–Miocene Transition: A palynological perspective from IODP Site U1406 (Newfoundland margin). Marine Micropaleontology, 139, 57-71. (doi:10.1016/j.marmicro.2017.11.003).

Record type: Article

Abstract

The Oligocene–Miocene transition (OMT; ~ 23.1 Ma) terminates the late Oligocene warming trend and is marked by a transient, large-amplitude expansion of Antarctic ice sheets. The associated glacial maximum, which is expressed by a ~ 1‰ positive shift in benthic foraminiferal oxygen-isotope values, is commonly referred to as the ‘Mi-1 isotope event’. Whereas the causes for the glacial maximum at the OMT are intrinsically connected to Southern Hemisphere ice-sheet dynamics, the behavior of the surface ocean in the Northern Hemisphere during this time is poorly known. To contribute to a better understanding of the paleoceanographic evolution during the OMT in the higher-latitude North Atlantic, we have analysed both marine and terrestrial palynomorphs from Integrated Ocean Drilling Program (IODP) Site U1406 offshore Newfoundland; this site has yielded a complete OMT section and exhibits a high-quality magnetostratigraphy that provides precise age control and allows reliable correlation to other records beyond Newfoundland. Our palynological data, which span the interval from 23.3 to 22.5 Ma and have a mean temporal resolution of 11.9 kyrs, show strong ~ 110-kyr eccentricity-paced oscillations during the earliest Miocene; these oscillations are in phase with similar cyclicity identified in previously published benthic foraminiferal oxygen-isotope records. More specifically, a pronounced sea-level variability is documented by the abundances of neritic dinoflagellate cysts (dinocysts) and terrigenous palynomorphs, which both reach maxima during peak glacial intervals as inferred from previously published South Atlantic benthic oxygen-isotope data. A decline in the abundance of warmer-water dinocysts suggests a surface-water cooling offshore Newfoundland from the latest Oligocene onwards. Surface-water productivity (as derived from the ratio between heterotrophic and autotrophic dinocysts) remained generally low throughout the studied interval. Notably, this ratio does not exhibit any correlation with changes in surface-water temperature, which is estimated from the ratio of warm-water over cold-water dinocysts. Together with the consistently low surface-water productivity, the lack of a correlation between surface-water productivity and temperature makes it highly unlikely that the observed paleoceanographic change was caused by a southward migration of the Arctic Front. Instead, we argue that our data may document an enhanced influence of the (Proto-) Labrador Current on surface waters offshore Newfoundland during the earliest Miocene that suppressed the influence of the Gulf Stream in this region of the Northwest Atlantic. We speculate that the enhanced influence of the (Proto-) Labrador Current was triggered by cooling of the northern hemisphere and possibly modulated by high-latitude sea-ice expansion.

Text Liebrand_et_al_PNAS_2017_Institutional_Copy - Accepted Manuscript
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More information

Accepted/In Press date: 15 November 2017
e-pub ahead of print date: 21 November 2017
Published date: 1 March 2018

Identifiers

Local EPrints ID: 416353
URI: https://eprints.soton.ac.uk/id/eprint/416353
ISSN: 0377-8398
PURE UUID: 1aceb28b-9f57-48a3-80f1-caa14426d189
ORCID for Tim E. Van Peer: ORCID iD orcid.org/0000-0003-3516-4198

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Date deposited: 14 Dec 2017 17:30
Last modified: 01 Mar 2018 17:31

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Contributors

Author: Lisa M. Egger
Author: André Bahr
Author: Oliver Friedrich
Author: Paul A. Wilson
Author: Richard D. Norris
Author: Tim E. Van Peer ORCID iD
Author: Peter C. Lippert
Author: Diederik Liebrand
Author: Jörg Pross

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