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Causes and consequences of diachronous V-shaped ridges in the North Atlantic Ocean

Causes and consequences of diachronous V-shaped ridges in the North Atlantic Ocean
Causes and consequences of diachronous V-shaped ridges in the North Atlantic Ocean
In the North Atlantic Ocean, the geometry of diachronous V-shaped features that straddle the Reykjanes Ridge is often attributed to thermal pulses which advect away from the center of the Iceland plume. Recently, two alternative hypotheses have been proposed: rift propagation and buoyant mantle upwelling. Here, we evaluate these different proposals using basin-wide geophysical and geochemical observations. The centerpiece of our analysis is a pair of seismic reflection profiles oriented parallel to flowlines that span the North Atlantic Ocean. V-shaped ridges and troughs are mapped on both Neogene and Paleogene oceanic crust, enabling a detailed chronology of activity to be established for the last 50 million years. Estimates of the cumulative horizontal displacement across normal faults help to discriminate between brittle and magmatic modes of plate separation, suggesting that crustal architecture is sensitive to the changing planform of the plume. Water-loaded residual depth measurements are used to estimate crustal thickness and to infer mantle potential temperature which varies by 25◦C on timescales of 3–8 Ma. This variation is consistent with the range of temperatures inferred from geochemical modeling of dredged basaltic rocks along the ridge axis itself, from changes in Neogene deep-water circulation, and from the regional record of episodic Cenozoic magmatism. We conclude that radial propagation of transient thermal anomalies within an asthenospheric channel that is 150 50 km thick best accounts for the available geophysical and geochemical observations.
2169-9356
8675–8708
Parnell-Turner, Ross
dbb5c554-7052-4365-938d-b73c5bbb4c94
White, Nicky
2fe72ea8-05d2-4164-a2a5-326b476d5dc9
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Jones, Stephen M.
7543978e-50cd-4b69-afd5-fd7131fdc08a
Maclennan, John
bf666f63-a308-4e23-8da6-c6f76fa77b41
Murton, Bramley J.
9076d07f-a3c1-4f90-a5d5-99b27fe2cb12
Parnell-Turner, Ross
dbb5c554-7052-4365-938d-b73c5bbb4c94
White, Nicky
2fe72ea8-05d2-4164-a2a5-326b476d5dc9
Henstock, Timothy J.
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Jones, Stephen M.
7543978e-50cd-4b69-afd5-fd7131fdc08a
Maclennan, John
bf666f63-a308-4e23-8da6-c6f76fa77b41
Murton, Bramley J.
9076d07f-a3c1-4f90-a5d5-99b27fe2cb12

Parnell-Turner, Ross, White, Nicky, Henstock, Timothy J., Jones, Stephen M., Maclennan, John and Murton, Bramley J. (2017) Causes and consequences of diachronous V-shaped ridges in the North Atlantic Ocean. Journal of Geophysical Research: Solid Earth, 122 (11), 8675–8708. (doi:10.1002/2017jb014225).

Record type: Article

Abstract

In the North Atlantic Ocean, the geometry of diachronous V-shaped features that straddle the Reykjanes Ridge is often attributed to thermal pulses which advect away from the center of the Iceland plume. Recently, two alternative hypotheses have been proposed: rift propagation and buoyant mantle upwelling. Here, we evaluate these different proposals using basin-wide geophysical and geochemical observations. The centerpiece of our analysis is a pair of seismic reflection profiles oriented parallel to flowlines that span the North Atlantic Ocean. V-shaped ridges and troughs are mapped on both Neogene and Paleogene oceanic crust, enabling a detailed chronology of activity to be established for the last 50 million years. Estimates of the cumulative horizontal displacement across normal faults help to discriminate between brittle and magmatic modes of plate separation, suggesting that crustal architecture is sensitive to the changing planform of the plume. Water-loaded residual depth measurements are used to estimate crustal thickness and to infer mantle potential temperature which varies by 25◦C on timescales of 3–8 Ma. This variation is consistent with the range of temperatures inferred from geochemical modeling of dredged basaltic rocks along the ridge axis itself, from changes in Neogene deep-water circulation, and from the regional record of episodic Cenozoic magmatism. We conclude that radial propagation of transient thermal anomalies within an asthenospheric channel that is 150 50 km thick best accounts for the available geophysical and geochemical observations.

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More information

Accepted/In Press date: 14 August 2017
e-pub ahead of print date: 9 October 2017
Published date: 14 November 2017

Identifiers

Local EPrints ID: 414347
URI: http://eprints.soton.ac.uk/id/eprint/414347
ISSN: 2169-9356
PURE UUID: c778d636-87ed-4c5c-abc1-277472fe0b80
ORCID for Timothy J. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

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Date deposited: 27 Sep 2017 16:30
Last modified: 07 Oct 2020 04:24

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