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Age of Seychelles–India break-up

Age of Seychelles–India break-up
Age of Seychelles–India break-up
Many continental flood basalt provinces are spatially and temporally linked with continental break-up. Establishing the relative timing of the two events is a key step in determining their causal relationship. Here we investigate the example of the Deccan Traps and the separation of India and the Seychelles. Whilst there has been a growing consensus as to the age of the main phase of the Deccan emplacement (65.5 ± 1 Ma, chron 29r), the age of the rifting has remained unclear. We resolve this issue through detailed seafloor magnetic anomaly modeling (supported by wide-angle and reflection seismic results) of the north Seychelles and conjugate Laxmi Ridge/Gop Rift margins, and geochemistry and 40Ar/39Ar geochronology of rocks from the north Seychelles margin. We show that syn-rift volcanics offshore the Seychelles Islands in the form of seaward-dipping reflectors were most likely erupted during chron 28n, and the first organized seafloor spreading at the Carlsberg Ridge also initiated during this chron at 63.4 Ma. The severing of the Seychelles occurred by a south-eastward ridge propagation that was completed by the start of chron 27n (~ 62 Ma). A brief, pre-28r phase of seafloor spreading occurred in the Gop Rift, possibly as early as 31r–32n (~ 71 Ma). Initial extension at the margin therefore preceded or was contemporaneous with the Deccan emplacement, and separation of the Seychelles was achieved less than 3.5 Ma afterwards. This is the shortest time interval between flood basalt emplacement and break-up yet reported for any continental flood basalt-rifted margin pair. A contributing factor to the apparently short interval in the Deccan case may be that rifting occurred by a ridge jump into already thinned continental lithosphere. However, we conclude that external plate-boundary forces, rather than the impact of a mantle plume, were largely responsible for the rifting of the Seychelles from India.
continental break-up, magnetic anomalies, deccan, laxmi ridge, gop rift
0012-821X
264-277
Collier, J.S.
19dfa4bb-f743-4ca8-b15f-0f72f3f7263c
Sansom, V.
6e7c72ea-bf51-49c6-add6-ff408b0fc824
Ishizuka, O.
8fe117e5-b0da-41ef-83ec-9e0bd6658747
Taylor, R.N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Whitmarsh, R.B.
8a17394e-90a9-404a-a40c-f0099e9bfc1f
Collier, J.S.
19dfa4bb-f743-4ca8-b15f-0f72f3f7263c
Sansom, V.
6e7c72ea-bf51-49c6-add6-ff408b0fc824
Ishizuka, O.
8fe117e5-b0da-41ef-83ec-9e0bd6658747
Taylor, R.N.
094be7fd-ef61-4acd-a795-7daba2bc6183
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Whitmarsh, R.B.
8a17394e-90a9-404a-a40c-f0099e9bfc1f

Collier, J.S., Sansom, V., Ishizuka, O., Taylor, R.N., Minshull, T.A. and Whitmarsh, R.B. (2008) Age of Seychelles–India break-up. Earth and Planetary Science Letters, 272 (1-2), 264-277. (doi:10.1016/j.epsl.2008.04.045).

Record type: Article

Abstract

Many continental flood basalt provinces are spatially and temporally linked with continental break-up. Establishing the relative timing of the two events is a key step in determining their causal relationship. Here we investigate the example of the Deccan Traps and the separation of India and the Seychelles. Whilst there has been a growing consensus as to the age of the main phase of the Deccan emplacement (65.5 ± 1 Ma, chron 29r), the age of the rifting has remained unclear. We resolve this issue through detailed seafloor magnetic anomaly modeling (supported by wide-angle and reflection seismic results) of the north Seychelles and conjugate Laxmi Ridge/Gop Rift margins, and geochemistry and 40Ar/39Ar geochronology of rocks from the north Seychelles margin. We show that syn-rift volcanics offshore the Seychelles Islands in the form of seaward-dipping reflectors were most likely erupted during chron 28n, and the first organized seafloor spreading at the Carlsberg Ridge also initiated during this chron at 63.4 Ma. The severing of the Seychelles occurred by a south-eastward ridge propagation that was completed by the start of chron 27n (~ 62 Ma). A brief, pre-28r phase of seafloor spreading occurred in the Gop Rift, possibly as early as 31r–32n (~ 71 Ma). Initial extension at the margin therefore preceded or was contemporaneous with the Deccan emplacement, and separation of the Seychelles was achieved less than 3.5 Ma afterwards. This is the shortest time interval between flood basalt emplacement and break-up yet reported for any continental flood basalt-rifted margin pair. A contributing factor to the apparently short interval in the Deccan case may be that rifting occurred by a ridge jump into already thinned continental lithosphere. However, we conclude that external plate-boundary forces, rather than the impact of a mantle plume, were largely responsible for the rifting of the Seychelles from India.

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More information

e-pub ahead of print date: 13 May 2008
Published date: 30 July 2008
Keywords: continental break-up, magnetic anomalies, deccan, laxmi ridge, gop rift
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 64017
URI: http://eprints.soton.ac.uk/id/eprint/64017
ISSN: 0012-821X
PURE UUID: 1878a528-3f1c-4588-9dbb-84a324ae46a5
ORCID for R.N. Taylor: ORCID iD orcid.org/0000-0002-9367-0294
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 25 Nov 2008
Last modified: 16 Mar 2024 03:11

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Contributors

Author: J.S. Collier
Author: V. Sansom
Author: O. Ishizuka
Author: R.N. Taylor ORCID iD
Author: T.A. Minshull ORCID iD
Author: R.B. Whitmarsh

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