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Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism

Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism
Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism
Seismic reflection data from the Makran continental margin indicate the presence of a strong and widespread bottom simulating reflector (BSR). We apply a nonlinear full waveform inversion technique to multichannel reflection data from this area, to investigate the detailed velocity structure and hence the origin of the BSR. Our result shows an abrupt decrease in the compressional wave velocity from 2.2 to 1.3 km/s at a depth of 500 m below the sea-bed. The low velocity zone is unusually thick (~200–350 m), and may contain large quantities of free gas, similar to some of the recently drilled Blake Ridge sites of ODP Leg 164. The voluminous free gas may have been generated by the dissociation of gas hydrates as a consequence of the upward movement of the base of gas-hydrate stability field, relative to the sediment column, due to uplift and sedimentation in the accretionary wedge.
MAKRAN, ARABIAN SEA, INDNW, CONTINENTAL MARGINS, ACCRETIONARY PRISMS, GAS HYDRATES, SEISMIC REFLECTION, BOTTOM SIMULATING REFLECTORS
0025-3227
3-12
Sain, K.
2cc59169-e0e1-482e-91b5-b357177b20d6
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Singh, S.C.
b23f1231-1b5d-4843-8b12-0d32fc7bc2c1
Hobbs, R.W.
a9a99163-c8a3-4d29-b673-61260be15157
Sain, K.
2cc59169-e0e1-482e-91b5-b357177b20d6
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Singh, S.C.
b23f1231-1b5d-4843-8b12-0d32fc7bc2c1
Hobbs, R.W.
a9a99163-c8a3-4d29-b673-61260be15157

Sain, K., Minshull, T.A., Singh, S.C. and Hobbs, R.W. (2000) Evidence for a thick free gas layer beneath the bottom simulating reflector in the Makran accretionary prism. Marine Geology, 164 (1-2), 3-12. (doi:10.1016/S0025-3227(99)00122-X).

Record type: Article

Abstract

Seismic reflection data from the Makran continental margin indicate the presence of a strong and widespread bottom simulating reflector (BSR). We apply a nonlinear full waveform inversion technique to multichannel reflection data from this area, to investigate the detailed velocity structure and hence the origin of the BSR. Our result shows an abrupt decrease in the compressional wave velocity from 2.2 to 1.3 km/s at a depth of 500 m below the sea-bed. The low velocity zone is unusually thick (~200–350 m), and may contain large quantities of free gas, similar to some of the recently drilled Blake Ridge sites of ODP Leg 164. The voluminous free gas may have been generated by the dissociation of gas hydrates as a consequence of the upward movement of the base of gas-hydrate stability field, relative to the sediment column, due to uplift and sedimentation in the accretionary wedge.

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More information

Published date: 2000
Keywords: MAKRAN, ARABIAN SEA, INDNW, CONTINENTAL MARGINS, ACCRETIONARY PRISMS, GAS HYDRATES, SEISMIC REFLECTION, BOTTOM SIMULATING REFLECTORS

Identifiers

Local EPrints ID: 8733
URI: https://eprints.soton.ac.uk/id/eprint/8733
ISSN: 0025-3227
PURE UUID: 12631607-f292-4985-97d6-0ba16d333d5a
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

Catalogue record

Date deposited: 13 Sep 2004
Last modified: 19 Jul 2019 01:05

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