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Structural controls on seepage of thermogenic and microbial methane since the last glacial maximum in the Harstad Basin, southwest Barents Sea

Crémière, Antoine and Chand, Shyam and Sahy, Diana and Thorsnes, Terje and Martma, Tõnu and Noble, Stephen R. and Pedersen, Jon Halvard and Brunstad, Harald and Lepland, Aivo (2018) Structural controls on seepage of thermogenic and microbial methane since the last glacial maximum in the Harstad Basin, southwest Barents Sea. Marine and Petroleum Geology, 98 . pp. 569-581. ISSN 0264-8172. https://resolver.caltech.edu/CaltechAUTHORS:20181212-104903325

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Abstract

The Harstad Basin is a structural block on the continental shelf of SW Barents Sea where gas hydrates likely occurred below the grounded ice-sheet during the last glaciation and it hosts active gas seepage at numerous seafloor sites. We present an integrated study of fluid flow systems in the Harstad Basin by combining seismic profile interpretations and gas flare mapping data with the geochemical results obtained on seafloor seeping gas and methane-derived carbonate crusts. More than 190 acoustic gas flares were registered in water column, many of them in association with pockmarks and carbonate crust fields. However, weak or absent seepage observed during remotely operated underwater vehicle transects across many pockmarks and crust fields suggests that seepage activity may have decreased since the last deglaciation. In the western Harstad Basin, seeps of microbial methane occur mainly above Tertiary formations that are pinching out below the glacial sediments. High amplitude seismic anomalies suggest the presence of gas pockets at the base of the glacial sediments and within Tertiary deposits. In contrast, gas seeping in the eastern Harstad Basin originates from a biodegraded thermogenic source tentatively connected to the deeply faulted Mesozoic rocks occurring below glacial sediments. This spatial variability in fluid sources is also recorded in the carbon isotope data of seafloor carbonate crusts, with δ^(13)C values typically between −55 and −42‰ and −40 and −20 ‰VPDB for carbonate crusts associated with microbial and thermogenic fluids, respectively. U-Th chronology combined with the stable isotope data suggests that this discrepancy in fluid sources over a distance of about 20 km has been stable since the last glaciation and highlights the significance of regional underlying geology in mediating fluid supply to the seafloor.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.marpetgeo.2018.07.010DOIArticle
ORCID:
AuthorORCID
Crémière, Antoine0000-0001-7382-2097
Martma, Tõnu0000-0001-5894-7692
Additional Information:© 2018 Elsevier Ltd. Received 7 February 2018, Revised 21 June 2018, Accepted 12 July 2018, Available online 10 August 2018.
Funders:
Funding AgencyGrant Number
Norges Geologiske UndersøkelseUNSPECIFIED
Norges Forskningsråd223259
Lundin Norway ASUNSPECIFIED
Record Number:CaltechAUTHORS:20181212-104903325
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20181212-104903325
Official Citation:Antoine Crémière, Shyam Chand, Diana Sahy, Terje Thorsnes, Tõnu Martma, Stephen R. Noble, Jon Halvard Pedersen, Harald Brunstad, Aivo Lepland, Structural controls on seepage of thermogenic and microbial methane since the last glacial maximum in the Harstad Basin, southwest Barents Sea, Marine and Petroleum Geology, Volume 98, 2018, Pages 569-581, ISSN 0264-8172, https://doi.org/10.1016/j.marpetgeo.2018.07.010. (http://www.sciencedirect.com/science/article/pii/S0264817218302885)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91727
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Dec 2018 18:53
Last Modified:03 Oct 2019 20:37

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