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Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data

Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data
Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data
The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data were the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high-resolution two-dimensional (2-D) airgun, sweep frequency SYSIF, and three-dimensional (3-D) p-cable seismic reflection data were acquired at the south-eastern part of the ridge between 2011 and 2013. The CSEM and seismic data contain profiles across and along the ridge, passing several active and inactive pockmarks. Joint interpretation of resistivity models obtained from CSEM and seismic reflection data provides new information regarding the fluid composition beneath the pockmarks. There is considerable variation in transverse resistance and seismic reflection characteristics of the gas hydrate stability zone (GHSZ) between the ridge flanks and chimneys beneath pockmarks. Layered seismic reflectors on the flanks are associated with around 300 Ωm2 transverse resistance, whereas the seismic reflectors within the chimneys exhibit amplitude blanking and chaotic patterns. The transverse resistance of the GHSZ within the chimneys vary between 400 and 1200 Ωm2. Variance attributes obtained from the 3-D p-cable data also highlight faults and chimneys, which coincide with the resistivity anomalies. Based on the joint data interpretation, widespread gas hydrate presence is likely at the ridge, with both hydrates and free gas contained within the faults and chimneys. However, at the active chimneys the effect of gas likely dominates the resistive anomalies.
1525-2027
1111-1125
Goswami, Bedanta K.
c2e137f2-fe5d-4814-9df0-e956fe8075a8
Weitemeyer, Karen A.
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Bünz, Stefan
23aa04cd-7a71-4550-b218-d857af41be49
Minshull, Timothy A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Westbrook, Graham K.
ccd95de7-a1a1-4fc9-be37-f1a487bb65ca
Ker, Stephan
3daed197-4ba3-4ed2-b7d4-ff267c2350c1
Sinha, Martin C.
794c3012-d0e8-4d2f-b328-c8cfd56c5976
Goswami, Bedanta K.
c2e137f2-fe5d-4814-9df0-e956fe8075a8
Weitemeyer, Karen A.
22c524f6-b24d-4d2a-a46d-16b06c70a5d1
Bünz, Stefan
23aa04cd-7a71-4550-b218-d857af41be49
Minshull, Timothy A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Westbrook, Graham K.
ccd95de7-a1a1-4fc9-be37-f1a487bb65ca
Ker, Stephan
3daed197-4ba3-4ed2-b7d4-ff267c2350c1
Sinha, Martin C.
794c3012-d0e8-4d2f-b328-c8cfd56c5976

Goswami, Bedanta K., Weitemeyer, Karen A., Bünz, Stefan, Minshull, Timothy A., Westbrook, Graham K., Ker, Stephan and Sinha, Martin C. (2017) Variations in pockmark composition at the Vestnesa Ridge: Insights from marine controlled source electromagnetic and seismic data. Geochemistry, Geophysics, Geosystems, 18 (3), 1111-1125. (doi:10.1002/ggge.v18.3).

Record type: Article

Abstract

The Vestnesa Ridge marks the northern boundary of a known submarine gas hydrate province in the west Svalbard margin. Several seafloor pockmarks at the eastern segment of the ridge are sites of active methane venting. Until recently, seismic reflection data were the main tool for imaging beneath the ridge. Coincident controlled source electromagnetic (CSEM), high-resolution two-dimensional (2-D) airgun, sweep frequency SYSIF, and three-dimensional (3-D) p-cable seismic reflection data were acquired at the south-eastern part of the ridge between 2011 and 2013. The CSEM and seismic data contain profiles across and along the ridge, passing several active and inactive pockmarks. Joint interpretation of resistivity models obtained from CSEM and seismic reflection data provides new information regarding the fluid composition beneath the pockmarks. There is considerable variation in transverse resistance and seismic reflection characteristics of the gas hydrate stability zone (GHSZ) between the ridge flanks and chimneys beneath pockmarks. Layered seismic reflectors on the flanks are associated with around 300 Ωm2 transverse resistance, whereas the seismic reflectors within the chimneys exhibit amplitude blanking and chaotic patterns. The transverse resistance of the GHSZ within the chimneys vary between 400 and 1200 Ωm2. Variance attributes obtained from the 3-D p-cable data also highlight faults and chimneys, which coincide with the resistivity anomalies. Based on the joint data interpretation, widespread gas hydrate presence is likely at the ridge, with both hydrates and free gas contained within the faults and chimneys. However, at the active chimneys the effect of gas likely dominates the resistive anomalies.

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Goswami_et_al-2017-Geochemistry,_Geophysics,_Geosystems - Version of Record
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Accepted/In Press date: 10 February 2017
Published date: 24 March 2017
Organisations: Geology & Geophysics, Ocean and Earth Science

Identifiers

Local EPrints ID: 411947
URI: http://eprints.soton.ac.uk/id/eprint/411947
ISSN: 1525-2027
PURE UUID: 1a0825b9-b182-449d-a045-3e50c518ebb6
ORCID for Timothy A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

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Date deposited: 03 Jul 2017 16:31
Last modified: 28 Jan 2022 02:36

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Contributors

Author: Bedanta K. Goswami
Author: Karen A. Weitemeyer
Author: Stefan Bünz
Author: Stephan Ker
Author: Martin C. Sinha

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