Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing
Barkley Canyon is one of the few known sites worldwide with the occurrence of thermogenic gas seepage and formation of structure-II and structure-H gas hydrate mounds on the seafloor. This site is the location of continuous seafloor monitoring as part of the Ocean Networks Canada (ONC) cabled observ...
| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2022-04-01
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| Series: | Frontiers in Earth Science |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/feart.2022.852853/full |
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| author | M. Riedel M. Scherwath M. Römer C. K. Paull E. M. Lundsten D. Caress P. G. Brewer J. W. Pohlman L. L. Lapham N. R. Chapman M. J. Whiticar G. D. Spence R. J. Enkin K. Douglas |
| author_facet | M. Riedel M. Scherwath M. Römer C. K. Paull E. M. Lundsten D. Caress P. G. Brewer J. W. Pohlman L. L. Lapham N. R. Chapman M. J. Whiticar G. D. Spence R. J. Enkin K. Douglas |
| author_sort | M. Riedel |
| collection | DOAJ |
| description | Barkley Canyon is one of the few known sites worldwide with the occurrence of thermogenic gas seepage and formation of structure-II and structure-H gas hydrate mounds on the seafloor. This site is the location of continuous seafloor monitoring as part of the Ocean Networks Canada (ONC) cabled observatory off the west coast off Vancouver Island, British Columbia, Canada. We combine repeat remotely operated vehicle (ROV) seafloor video observations, mapping with an autonomous underwater vehicle (AUV), ship-, ROV-, and AUV-based identification of gas flares, as well as seismic and Chirp data to investigate the distribution of fluid migration pathways. Geologically, the site with the prominent gas hydrate mounds and associated fluid seepage is covering an area of ∼0.15 km2 and is situated on a remnant of a rotated fault block that had slipped off the steep flanks of the north-east facing canyon wall. The gas hydrate mounds, nearly constant in dimension over the entire observation period, are associated with gas and oil seepage and surrounded by debris of chemosynthetic communities and authigenic carbonate. The formation of gas hydrate at and near the seafloor requires additional accommodation space created by forming blisters at the seafloor that displace the regular sediments. An additional zone located centrally on the rotated fault block with more diffuse seepage (∼0.02 km2 in extent) has been identified with no visible mounds, but with bacterial mats, small carbonate concretions, and clam beds. Gas venting is seen acoustically in the water column up to a depth of ∼300 m. However, acoustic water-column imaging during coring and ROV dives showed rising gas bubbles to much shallower depth, even <50 m, likely a result of degassing of rising oil droplets, which themselves cannot be seen acoustically. Combining all observations, the location of the gas hydrate mounds is controlled by a combination of fault-focused fluid migration from a deeper reservoir and fluid seepage along more permeable strata within the rotated slope block. Fluids must be provided continuously to allow the sustained presence of the gas hydrate mounds at the seafloor. |
| first_indexed | 2024-12-11T22:50:34Z |
| format | Article |
| id | doaj.art-219d4027962a4d00814bd6f4e93a6155 |
| institution | Directory Open Access Journal |
| issn | 2296-6463 |
| language | English |
| last_indexed | 2024-12-11T22:50:34Z |
| publishDate | 2022-04-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Earth Science |
| spelling | doaj.art-219d4027962a4d00814bd6f4e93a61552022-12-22T00:47:28ZengFrontiers Media S.A.Frontiers in Earth Science2296-64632022-04-011010.3389/feart.2022.852853852853Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote SensingM. Riedel0M. Scherwath1M. Römer2C. K. Paull3E. M. Lundsten4D. Caress5P. G. Brewer6J. W. Pohlman7L. L. Lapham8N. R. Chapman9M. J. Whiticar10G. D. Spence11R. J. Enkin12K. Douglas13GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyOcean Networks Canada, University of Victoria, Victoria, BC, CanadaMARUM - Center for Environmental Sciences and Department of Geosciences at the University of Bremen, Bremen, GermanyMonterey Bay Aquarium Research Institute, Moss Landing, CA, United StatesMonterey Bay Aquarium Research Institute, Moss Landing, CA, United StatesMonterey Bay Aquarium Research Institute, Moss Landing, CA, United StatesMonterey Bay Aquarium Research Institute, Moss Landing, CA, United StatesU.S. Geological Survey, Woods Hole Coastal and Marine Science Center, Woods Hole, MA, United StatesUniversity of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD, United StatesSchool of Earth and Ocean Sciences, University of Victoria, Victoria, BC, CanadaSchool of Earth and Ocean Sciences, University of Victoria, Victoria, BC, CanadaSchool of Earth and Ocean Sciences, University of Victoria, Victoria, BC, CanadaGeological Survey of Canada, Pacific, Victoria, BC, CanadaGeological Survey of Canada, Pacific, Victoria, BC, CanadaBarkley Canyon is one of the few known sites worldwide with the occurrence of thermogenic gas seepage and formation of structure-II and structure-H gas hydrate mounds on the seafloor. This site is the location of continuous seafloor monitoring as part of the Ocean Networks Canada (ONC) cabled observatory off the west coast off Vancouver Island, British Columbia, Canada. We combine repeat remotely operated vehicle (ROV) seafloor video observations, mapping with an autonomous underwater vehicle (AUV), ship-, ROV-, and AUV-based identification of gas flares, as well as seismic and Chirp data to investigate the distribution of fluid migration pathways. Geologically, the site with the prominent gas hydrate mounds and associated fluid seepage is covering an area of ∼0.15 km2 and is situated on a remnant of a rotated fault block that had slipped off the steep flanks of the north-east facing canyon wall. The gas hydrate mounds, nearly constant in dimension over the entire observation period, are associated with gas and oil seepage and surrounded by debris of chemosynthetic communities and authigenic carbonate. The formation of gas hydrate at and near the seafloor requires additional accommodation space created by forming blisters at the seafloor that displace the regular sediments. An additional zone located centrally on the rotated fault block with more diffuse seepage (∼0.02 km2 in extent) has been identified with no visible mounds, but with bacterial mats, small carbonate concretions, and clam beds. Gas venting is seen acoustically in the water column up to a depth of ∼300 m. However, acoustic water-column imaging during coring and ROV dives showed rising gas bubbles to much shallower depth, even <50 m, likely a result of degassing of rising oil droplets, which themselves cannot be seen acoustically. Combining all observations, the location of the gas hydrate mounds is controlled by a combination of fault-focused fluid migration from a deeper reservoir and fluid seepage along more permeable strata within the rotated slope block. Fluids must be provided continuously to allow the sustained presence of the gas hydrate mounds at the seafloor.https://www.frontiersin.org/articles/10.3389/feart.2022.852853/fullgas hydratefluid seepageBarkley Canyon hydratesAUV (autonomous underwater vehicle)ROV (remote operated vehicle) |
| spellingShingle | M. Riedel M. Scherwath M. Römer C. K. Paull E. M. Lundsten D. Caress P. G. Brewer J. W. Pohlman L. L. Lapham N. R. Chapman M. J. Whiticar G. D. Spence R. J. Enkin K. Douglas Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing Frontiers in Earth Science gas hydrate fluid seepage Barkley Canyon hydrates AUV (autonomous underwater vehicle) ROV (remote operated vehicle) |
| title | Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing |
| title_full | Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing |
| title_fullStr | Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing |
| title_full_unstemmed | Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing |
| title_short | Barkley Canyon Gas Hydrates: A Synthesis Based on Two Decades of Seafloor Observation and Remote Sensing |
| title_sort | barkley canyon gas hydrates a synthesis based on two decades of seafloor observation and remote sensing |
| topic | gas hydrate fluid seepage Barkley Canyon hydrates AUV (autonomous underwater vehicle) ROV (remote operated vehicle) |
| url | https://www.frontiersin.org/articles/10.3389/feart.2022.852853/full |
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