Publication Date:
2022-05-26
Description:
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Prouty, N. G., Brothers, D. S., Kluesner, J. W., Barrie, J. V., Andrews, B. D., Lauer, R. M., Greene, H. G., Conrad, J. E., Lorenson, T. D., Law, M. D., Sahy, D., Conway, K., McGann, M. L., & Dartnell, P. Focused fluid flow and methane venting along the Queen Charlotte fault, offshore Alaska (USA) and British Columbia (Canada). Geosphere, 16(6), (2020): 1336-1357, doi:10.1130/GES02269.1.
Description:
Fluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ∼850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic plates offshore southeastern Alaska (USA) and western British Columbia (Canada). Indications for fluid seepage along the QCF margin include gas bubbles originating from the seafloor and imaged in the water column, chemosynthetic communities, precipitates of authigenic carbonates, mud volcanoes, and changes in the acoustic character of seismic reflection data. Cold seeps sampled in this study preferentially occur along the crests of ridgelines associated with uplift and folding and between submarine canyons that incise the continental slope strata. With carbonate stable carbon isotope (δ13C) values ranging from −46‰ to −3‰, there is evidence of both microbial and thermal degradation of organic matter of continental-margin sediments along the QCF. Both active and dormant venting on ridge crests indicate that the development of anticlines is a key feature along the QCF that facilitates both trapping and focused fluid flow. Geochemical analyses of methane-derived authigenic carbonates are evidence of fluid seepage along the QCF since the Last Glacial Maximum. These cold seeps sustain vibrant chemosynthetic communities such as clams and bacterial mats, providing further evidence of venting of reduced chemical fluids such as methane and sulfide along the QCF.
Description:
The authors thank officers and crew of the CCGS Vector and CCGS John P. Tully; M. Baker (USGS), R. Garrison (UCSC), J. Fitzpatrick, (USGS), N. Vokhshoori (UCSC), and C. Maupin (Texas A&M University, College Station, Texas, USA) for laboratory and sample assistance; and J. Pohlman (USGS) for helpful comments. Input from two anonymous reviewers substantially improved the manuscript. The USGS Coastal and Marine Hazards and Resource Program funded this study. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Additional geochemical and geophysical data to support this project can be found in Prouty et al. (2019) and Balster-Gee et al. (2017a, 2017b), respectively.
Repository Name:
Woods Hole Open Access Server
Type:
Article
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