Sedimentary deformation relating to episodic seepage in the last 1.2 million years: a multi-scale seismic study from the Vestnesa Ridge, eastern Fram Strait

Frontiers in Earth Science

Earth Science

Andreia Plaza-Faverola¹  Frances Cooke¹  Stefan Bünz¹  Sunny Singhroha¹  Henry Patton¹  Nabil Sultan²  Hariharan Ramachandran³  Jochen Knies⁴  Heather Bedle⁵ 

[1] CAGE—Centre for Arctic Gas Hydrate, Environment and Climate, UiT (The Arctic University of Norway), The Arctic University of Norway, Tromsø, Norway;Geo-Ocean, UMR6538, Ifremer, CNRS, UBO, UBS, Plouzané, France;Institute of GeoEnergy Engineering, Heriot-Watt University, Edinburgh, United Kingdom;NGU—Geological Survey of Norway, Trondheim, Norway;School of Geosciences, The University of Oklahoma, Norman, OK, United States;

关键词: sediment fracturing;    episodic seepage;    high-resolution seismic attributes;    glacial dynamics;    Fram Strait;   

DOI  :  10.3389/feart.2023.1188737

 received in 2023-03-17, accepted in 2023-05-16,  发布年份 2023

来源: Frontiers

【 摘 要 】

Seafloor hydrocarbon seepage is a natural fluid release process that occurs worldwide on continental shelves, slopes, and in deep oceanic basins. The Vestnesa sedimentary ridge in the eastern Fram Strait hosts a deep-water gas hydrate system that became charged with hydrocarbons ∼2.7 Ma and has experienced episodic seepage along the entire ridge until a few thousand years ago, when seepage activity apparently ceased in the west but persisted in the east. Although it has been documented that faults and fractures play a key role in feeding the seeps with thermogenic gases, the mechanisms controlling seepage periodicity remain poorly understood. Here we integrate high-resolution P-cable 3D seismic and Chirp data to investigate the spatial and temporal evolution of high-resolution fractures and fluid flow features in the west of the Vestnesa Ridge. We characterize sediment deformation using a fracture density seismic attribute workflow revealing two highly deformed stratigraphic intervals and associated small-scale pockmarks (<20 m diameter). Chronostratigraphic constraints from the region show that these two highly deformed intervals are influenced by at least three major climatic and oceanic events during the last 1.2 million years: the Mid-Pleistocene Transition (∼1.25–0.7 Ma), the penultimate deglaciation (∼130 ka) and the last deglaciation (Heinrich Stadial 1: ∼16 ka). These periods of deformation appear associated with seismic anomalies potentially correlated with buried methane-derived authigenic carbonate and have been sensitive to shifts in the boundary of the free gas-gas hydrate interface. Our results show shifts (up to ∼30 m) in the depth of the base of the gas hydrate stability zone (GHSZ) associated with major changes in ocean bottom water temperatures. This ocean-driven effect on the base of the GHSZ since the Last Glacial Maximum coincides with the already highly deformed Mid-Pleistocene Transition sedimentary interval and likely enhanced deformation and gas leakage along the ridge. Our results have implications for understanding how glacial cycles impact fracture formation and associated seepage activity.

【 授权许可】

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Copyright © 2023 Cooke, Plaza-Faverola, Bünz, Sultan, Ramachandran, Bedle, Patton, Singhroha and Knies.