| Titre | Gas hydrate occurrences along the Haida Gwaii margin - constraints on the geothermal regime and implications for fluid flow |
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| Auteur | Riedel, M; Rohr, K M M; Côté, M M; Schmidt, U; Richardson, T |
| Source | Tectonic, sedimentary, volcanic and fluid flow processes along the Queen Charlotte-Fairweather Fault System and surrounding continental margin; par Brothers, D (éd.); Barrie, J V (éd.); Greene, H G (éd.); Geosphere vol. 16, no. 1, 2019 p. 1-12, https://doi.org/10.1130/GES02103.1  Accès ouvert |
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| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190640 |
| Éditeur | Geological Society of America |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1130/GES02103.1 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Diffusé | 2019 12 19 |
| Résumé | (disponible en anglais seulement)
Seismic-reflection data along the Haida Gwaii margin collected from 1967 to 2013 were used to identify gas hydrate-related bottom-simulating reflectors (BSRs).
The BSRs occur along the Queen Charlotte Terrace only, within more strongly folded and tectonically deformed sedimentary ridges. The BSRs are absent within well-bedded and sediment-filled minibasins. The BSR is modeled as the base of the phase
boundary of the methane hydrate (structure I) stability zone and is used to estimate geothermal gradients. The P-wave velocity structure required to convert observed depths of the BSR in two-way time to meters below seafloor was constrained from
ocean-bottom seismometers. The BSR-derived gradients are lower than data from heat-probe deployments in the region, as well as predicted values from previous modeling of the large-scale tectonic thermal regime. Lower values of the BSR-derived thermal
gradients may be due to topographic effects across the ridges where BSRs were observed. The previously identified landward decrease in thermal gradients across the terrace was also identified to a lesser extent from the BSRs, in accordance with the
effects of oblique convergence of the Pacific plate with the North American plate. Geothermal gradients decreased from south to north by a factor of two, which is likely an effect of plate cooling due to an increase in age of the underlying plate
(ca. 8 Ma off southern Haida Gwaii to ca. 12 Ma at Dixon Entrance) as well as the fact that sediments triple in thickness over the same distance. This may be due to downward flexure of the underlying crust during transpression and/or a high flux of
sediments through Dixon Entrance. |
| GEOSCAN ID | 322177 |
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