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Seismic structure of the Mid-Atlantic Ridge, 8-9S

Minshull, T.A., Bruguier, N.J. and Brozena, J.M. (2003) Seismic structure of the Mid-Atlantic Ridge, 8-9S Journal of Geophysical Research, 108, (B11), 02513-[22pp]. (doi:10.1029/2002JB002360).

Record type: Article


The Mid-Atlantic Ridge at 8–9°S is characterized by a transition from axial valley to axial high and recent episodes of ridge jumping and ridge propagation. We present constraints on the structure of 0–4 Ma crust in this region on the basis of the analysis of wide-angle seismic data from a grid of profiles across and parallel to the current and abandoned spreading centers. A 350–800 m thick oceanic layer 2A, interpreted as high-porosity extrusive basalts, is underlain by a ~2.0–2.5 km layer 2B with velocities which increase with age and decrease in the vicinity of the pseudofaults. Layer 3 velocities are uniform across the area except for a possible localized anomaly at the ridge axis. The crustal thickness varies from 6–7 km near the pseudofaults formed by ridge propagation to 9–10 km at the segment center of the recently (~0.3 Ma) abandoned spreading center. Seismically determined crustal thickness and density variations and age-related lithospheric cooling can plausibly account for all observed variations in gravity across the area, and there is no requirement for the thicker crust at the segment center to be underlain by hot mantle. The transition from axial valley to axial high occurs at a crustal thickness of ~8 km.

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Published date: November 2003
Keywords: mid-ocean ridge, South Atlantic, crustal structure, morphology, seismic velocity.


Local EPrints ID: 1368
ISSN: 0148-0227
PURE UUID: 97be61a5-2f8d-4429-bff7-b568394ce3fd
ORCID for T.A. Minshull: ORCID iD

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Date deposited: 19 Apr 2004
Last modified: 17 Jul 2017 17:16

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Author: T.A. Minshull ORCID iD
Author: N.J. Bruguier
Author: J.M. Brozena

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