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Continental hyperextension, mantle exhumation and thin oceanic crust at the continent-ocean transition, West Iberia: new insights from wide-angle seismic

Continental hyperextension, mantle exhumation and thin oceanic crust at the continent-ocean transition, West Iberia: new insights from wide-angle seismic
Continental hyperextension, mantle exhumation and thin oceanic crust at the continent-ocean transition, West Iberia: new insights from wide-angle seismic
Hyperextension of continental crust at the Deep Galicia rifted margin in the North Atlantic has been accommodated by the rotation of continental fault blocks, which are underlain by the S reflector, an interpreted detachment fault, along which exhumed and serpentinized mantle peridotite is observed. West of these features, the enigmatic Peridotite Ridge has been inferred to delimit the western extent of the continent-ocean transition. An outstanding question at this margin is where oceanic crust begins, with little existing data to constrain this boundary and a lack of clear seafloor spreading magnetic anomalies. Here we present results from a 160-km-long wide-angle seismic profile (WE-1). Travel-time tomography models of the crustal compressional velocity structure reveal highly thinned and rotated crustal blocks separated from the underlying mantle by the S-reflector. The S-reflector correlates with the 6.0 - 7.0 kms-1 velocity contours, corresponding to peridotite serpentinization of 60 - 30 %, respectively. West of the Peridotite Ridge, shallow and sparse Moho reflections indicate the earliest formation of an anomalously thin oceanic crustal layer, which increases in thickness from ~0.5 km at ~20 km west of the Peridotite Ridge to ~1.5 km, 35 km further west. P wave velocities increase smoothly and rapidly below top basement, to a depth of 2.8 - 3.5 km, with an average velocity gradient of 1.0 s-1. Below this, velocities slowly increase toward typical mantle velocities. Such a downward increase into mantle velocities is interpreted as decreasing serpentinization of mantle rock with depth.
COT, Galicia, rifting, serpentinization, hyperextension, wide-angle seismic
3177-3199
Davy, R.G.
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Minshull, T.A.
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Bayrakci, G.
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Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Klaeschen, D.
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Papenberg, C.
85928afb-f9b7-4cfe-8fd8-3a89b65d7916
Reston, T.J.
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Sawyer, D.S.
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Zelt, C.A.
5c02ce45-2f9f-4f21-8634-79729832ae44
Davy, R.G.
27b2af87-7c07-429e-94c6-5b66e65b5790
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Bayrakci, G.
e0b89aa5-d514-4ecb-91b1-8ed8bd472eda
Bull, J.M.
974037fd-544b-458f-98cc-ce8eca89e3c8
Klaeschen, D.
71af4fb3-19b5-4991-a4d2-944927a46504
Papenberg, C.
85928afb-f9b7-4cfe-8fd8-3a89b65d7916
Reston, T.J.
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Sawyer, D.S.
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Zelt, C.A.
5c02ce45-2f9f-4f21-8634-79729832ae44

Davy, R.G., Minshull, T.A., Bayrakci, G., Bull, J.M., Klaeschen, D., Papenberg, C., Reston, T.J., Sawyer, D.S. and Zelt, C.A. (2016) Continental hyperextension, mantle exhumation and thin oceanic crust at the continent-ocean transition, West Iberia: new insights from wide-angle seismic. Journal of Geophysical Research: Solid Earth, 121, 3177-3199. (doi:10.1002/2016JB012825).

Record type: Article

Abstract

Hyperextension of continental crust at the Deep Galicia rifted margin in the North Atlantic has been accommodated by the rotation of continental fault blocks, which are underlain by the S reflector, an interpreted detachment fault, along which exhumed and serpentinized mantle peridotite is observed. West of these features, the enigmatic Peridotite Ridge has been inferred to delimit the western extent of the continent-ocean transition. An outstanding question at this margin is where oceanic crust begins, with little existing data to constrain this boundary and a lack of clear seafloor spreading magnetic anomalies. Here we present results from a 160-km-long wide-angle seismic profile (WE-1). Travel-time tomography models of the crustal compressional velocity structure reveal highly thinned and rotated crustal blocks separated from the underlying mantle by the S-reflector. The S-reflector correlates with the 6.0 - 7.0 kms-1 velocity contours, corresponding to peridotite serpentinization of 60 - 30 %, respectively. West of the Peridotite Ridge, shallow and sparse Moho reflections indicate the earliest formation of an anomalously thin oceanic crustal layer, which increases in thickness from ~0.5 km at ~20 km west of the Peridotite Ridge to ~1.5 km, 35 km further west. P wave velocities increase smoothly and rapidly below top basement, to a depth of 2.8 - 3.5 km, with an average velocity gradient of 1.0 s-1. Below this, velocities slowly increase toward typical mantle velocities. Such a downward increase into mantle velocities is interpreted as decreasing serpentinization of mantle rock with depth.

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Accepted/In Press date: 13 April 2016
e-pub ahead of print date: 17 May 2016
Published date: 16 June 2016
Additional Information: Funded by Royal Society: Royal Society Wolfson Research Merit Award
Keywords: COT, Galicia, rifting, serpentinization, hyperextension, wide-angle seismic
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 392635
URI: http://eprints.soton.ac.uk/id/eprint/392635
PURE UUID: a37faf9f-36be-4bd6-9083-ade4b73c151c
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379
ORCID for J.M. Bull: ORCID iD orcid.org/0000-0003-3373-5807

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Date deposited: 14 Apr 2016 09:59
Last modified: 15 Mar 2024 03:04

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Contributors

Author: R.G. Davy
Author: T.A. Minshull ORCID iD
Author: G. Bayrakci
Author: J.M. Bull ORCID iD
Author: D. Klaeschen
Author: C. Papenberg
Author: T.J. Reston
Author: D.S. Sawyer
Author: C.A. Zelt

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