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Extension across the Indian-Arabian plate boundary: the Murray Ridge

Extension across the Indian-Arabian plate boundary: the Murray Ridge
Extension across the Indian-Arabian plate boundary: the Murray Ridge
Seismic reflection profiles from the Murray Ridge in the Gulf of Oman, northwest Indian Ocean, show a significant component of extension across the predominantly strike-slip Indian–Arabian plate boundary. The Murray Ridge lies along the northern section of the plate boundary, where its trend becomes more easterly and thus allows a component of extension. The Dalrymple Trough is a 25 km wide, steep-sided halfgraben, bounded by large faults with components of both strike-slip and normal motion. The throw at the seabed of the main fault on the southeastern side of the halfgraben reaches 1800 m. The northwest side of the trough is delineated by a series of smaller antithetic normal faults. Wide-angle seismic, gravity and magnetic models show that the Murray Ridge and Dalrymple Trough are underlain by a crystalline crust up to 17 km thick, which may be continental in origin. Any crustal thinning due to extension is limited, and no new crust has been formed. We favour a plate model in which the Indian–Arabian plate boundary was initially located further west than the Owen Fracture Zone, possibly along the Oman continental margin, and suggest that during the Oligocene–Early Miocene Indian Ocean plate reorganization, the plate boundary moved to the site of the present Owen Fracture Zone and that motion further west ceased. At this time, deformation began along the Murray Ridge, with both the uplift of basement highs, and subsidence in the troughs tilting the lowest sedimentary unit. Qalhat Seamount was formed at this time. Subsequent sediments were deposited unconformably on the tilted lower unit and then faulted to produce the present basement topography. The normal faulting was accompanied by hanging-wall subsidence, footwall uplift, and erosion. Flat-lying recent sediments show that the major vertical movements have ceased, although continuing earthquakes show that some faulting is still active along the plate boundary.
ARABIAN SEA, CRUSTAL STRUCTURE, OMAN GULF, PLATE BOUNDARIES
0956-540X
461-477
Edwards, R.A.
e733909a-1bd5-4302-ad8d-61e811b9d8fe
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
White, R.S.
3919ea9f-a09d-43c2-93fa-c7986055e486
Edwards, R.A.
e733909a-1bd5-4302-ad8d-61e811b9d8fe
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
White, R.S.
3919ea9f-a09d-43c2-93fa-c7986055e486

Edwards, R.A., Minshull, T.A. and White, R.S. (2000) Extension across the Indian-Arabian plate boundary: the Murray Ridge. Geophysical Journal International, 142 (2), 461-477. (doi:10.1046/j.1365-246x.2000.00163.x).

Record type: Article

Abstract

Seismic reflection profiles from the Murray Ridge in the Gulf of Oman, northwest Indian Ocean, show a significant component of extension across the predominantly strike-slip Indian–Arabian plate boundary. The Murray Ridge lies along the northern section of the plate boundary, where its trend becomes more easterly and thus allows a component of extension. The Dalrymple Trough is a 25 km wide, steep-sided halfgraben, bounded by large faults with components of both strike-slip and normal motion. The throw at the seabed of the main fault on the southeastern side of the halfgraben reaches 1800 m. The northwest side of the trough is delineated by a series of smaller antithetic normal faults. Wide-angle seismic, gravity and magnetic models show that the Murray Ridge and Dalrymple Trough are underlain by a crystalline crust up to 17 km thick, which may be continental in origin. Any crustal thinning due to extension is limited, and no new crust has been formed. We favour a plate model in which the Indian–Arabian plate boundary was initially located further west than the Owen Fracture Zone, possibly along the Oman continental margin, and suggest that during the Oligocene–Early Miocene Indian Ocean plate reorganization, the plate boundary moved to the site of the present Owen Fracture Zone and that motion further west ceased. At this time, deformation began along the Murray Ridge, with both the uplift of basement highs, and subsidence in the troughs tilting the lowest sedimentary unit. Qalhat Seamount was formed at this time. Subsequent sediments were deposited unconformably on the tilted lower unit and then faulted to produce the present basement topography. The normal faulting was accompanied by hanging-wall subsidence, footwall uplift, and erosion. Flat-lying recent sediments show that the major vertical movements have ceased, although continuing earthquakes show that some faulting is still active along the plate boundary.

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More information

Published date: 2000
Keywords: ARABIAN SEA, CRUSTAL STRUCTURE, OMAN GULF, PLATE BOUNDARIES

Identifiers

Local EPrints ID: 8732
URI: https://eprints.soton.ac.uk/id/eprint/8732
ISSN: 0956-540X
PURE UUID: b5afa526-b5e7-4ecd-80ae-b8d75b6f239e
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 24 Aug 2004
Last modified: 06 Jun 2018 12:52

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