Contrasting evolution of upper crustal velocities in young oceanic crust: Insights from the Southern Mid-Atlantic Ridge
Contrasting evolution of upper crustal velocities in young oceanic crust: Insights from the Southern Mid-Atlantic Ridge
Geophysical studies document rapid changes in upper crustal seismic velocities in young ocean crust that are attributed to infilling of cracks as a result of hydrothermal circulation. This study analyzes three seismic reflection profiles located on 0–6 Ma ocean crust on the slow-spreading southern Mid-Atlantic Ridge. Average velocities are ∼2.5 km/s at 0 Ma, 3.2 km/s at 0.5 Ma, and 4.0 km/s at 3.5 Ma. Velocities are relatively constant from 3.5 to 6 Myr. Velocity trends are similar along all profiles and on both ridge flanks; this similarity suggests that the underlying processes associated with the velocity changes are widespread. The trends are similar to those observed at the slow-spreading equatorial Mid-Atlantic Ridge. In contrast, velocities at the intermediate-spreading Juan de Fuca Ridge increase more slowly with age than observed at the Mid-Atlantic Ridge. We argue that processes related to spreading rate are a significant factor in the age-related physical property changes. In particular, we highlight that compression associated with stresses related to the axial valley morphology may result in more rapid crack closure on the slow-spreading Mid-Atlantic Ridge than in similar age crust at the intermediate-spreading Juan de Fuca Ridge where axial valley morphology is less pronounced. A secondary control of spreading rate might simply be the increased amount of time slow-spreading crust resides near the ridge axis where the most vigorous hydrothermal circulation occurs. The rate of change of seismic velocity in young crust may be further moderated by the impact of sediment cover on upper crustal alteration.
Crack closure, Mid-Atlantic Ridge, Velocity change
Christeson, Gail L.
60d59c1a-44ac-41d2-b291-49b2d84c8e99
Robert, William H.
1a99c8ed-1229-4133-840b-49c1d2251d09
Coggon, Rosalind M.
78a3f775-17b5-415e-97f2-26a0deffc444
Goff, John A.
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Evans, Aled D.
41a3083e-fb13-4f18-a35b-c0763afa7716
7 September 2025
Christeson, Gail L.
60d59c1a-44ac-41d2-b291-49b2d84c8e99
Robert, William H.
1a99c8ed-1229-4133-840b-49c1d2251d09
Coggon, Rosalind M.
78a3f775-17b5-415e-97f2-26a0deffc444
Goff, John A.
3677617d-c1a0-4c27-b6e5-acb4e734e7f1
Evans, Aled D.
41a3083e-fb13-4f18-a35b-c0763afa7716
Christeson, Gail L., Robert, William H., Coggon, Rosalind M., Goff, John A. and Evans, Aled D.
(2025)
Contrasting evolution of upper crustal velocities in young oceanic crust: Insights from the Southern Mid-Atlantic Ridge.
Tectonophysics, 914, [230905].
(doi:10.1016/j.tecto.2025.230905).
Abstract
Geophysical studies document rapid changes in upper crustal seismic velocities in young ocean crust that are attributed to infilling of cracks as a result of hydrothermal circulation. This study analyzes three seismic reflection profiles located on 0–6 Ma ocean crust on the slow-spreading southern Mid-Atlantic Ridge. Average velocities are ∼2.5 km/s at 0 Ma, 3.2 km/s at 0.5 Ma, and 4.0 km/s at 3.5 Ma. Velocities are relatively constant from 3.5 to 6 Myr. Velocity trends are similar along all profiles and on both ridge flanks; this similarity suggests that the underlying processes associated with the velocity changes are widespread. The trends are similar to those observed at the slow-spreading equatorial Mid-Atlantic Ridge. In contrast, velocities at the intermediate-spreading Juan de Fuca Ridge increase more slowly with age than observed at the Mid-Atlantic Ridge. We argue that processes related to spreading rate are a significant factor in the age-related physical property changes. In particular, we highlight that compression associated with stresses related to the axial valley morphology may result in more rapid crack closure on the slow-spreading Mid-Atlantic Ridge than in similar age crust at the intermediate-spreading Juan de Fuca Ridge where axial valley morphology is less pronounced. A secondary control of spreading rate might simply be the increased amount of time slow-spreading crust resides near the ridge axis where the most vigorous hydrothermal circulation occurs. The rate of change of seismic velocity in young crust may be further moderated by the impact of sediment cover on upper crustal alteration.
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Accepted/In Press date: 2 September 2025
e-pub ahead of print date: 3 September 2025
Published date: 7 September 2025
Keywords:
Crack closure, Mid-Atlantic Ridge, Velocity change
Identifiers
Local EPrints ID: 506326
URI: http://eprints.soton.ac.uk/id/eprint/506326
ISSN: 0040-1951
PURE UUID: 3393bddf-d4ec-46d8-92a8-fef342b852d4
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Date deposited: 04 Nov 2025 17:56
Last modified: 05 Nov 2025 03:00
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Contributors
Author:
Gail L. Christeson
Author:
William H. Robert
Author:
Rosalind M. Coggon
Author:
John A. Goff
Author:
Aled D. Evans
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