GEOSCAN, résultats de la recherche


TitreTemporal variability of in situ methane concentrations in gas hydrate-bearing sediments near Bullseye Vent, Northern Cascadia Margin
AuteurLapham, L; Wilson, R; Riedel, M; Paull, C K; Holmes, M E
SourceGeochemistry, Geophysics, Geosystems (G3) vol. 14, no. 7, 2013 p. 2445-2459,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120155
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-126.8583 -126.8375 48.6833 48.6625
Sujetsgaz; hydrate; hydrocarbures; méthane; sédiments marins; fluides des pores; ethane; propane; sulfates; secousses séismiques; marges continentales; études des isotopes stables; isotopes de carbone; combustibles fossiles
ProgrammeHydrates de gaz, Caractérisation des Hydrates de gaz
Diffusé2013 07 30
Résumé(disponible en anglais seulement)
To assess the temporal variability in the methane fluxes from marine sediments that overly gas hydrate bearing sediments and the factors that might control its rate, in situ methane concentrations were measured near Bullseye Vent on the Northern Cascadia continental margin. A long-term sampling device collected overlying water and pore-fluid samples from 25 cm above seafloor, at the sediment-water interface (SWI), and 7 cmbsf (centimeters below seafloor) over a 9 month period (August 2009 -- May 2010). These samples provide a record at ~4 day resolution of in situ methane, ethane, propane, sulfate, and chloride concentrations, as well as stable carbon isotope ratios of methane (delta-13C-CH4) and dissolved inorganic carbon (delta-13C-DIC). We show that pore fluids near the SWI are saturated or supersaturated with respect to methane (delta-80 mM) and the methane flux from the seabed is variable over time. We hypothesized that regional seismic activity controlled this variable CH4 flux in the Northern Cascadia continental margin setting. However, we found no direct correlation between earthquakes and CH4 flux. We also posited alternative controls on CH4 flux variability, such as storms, regional oceanography and microbial activity. Again, no direct correlation was seen. This study takes first steps toward exploring which physical factors play a role in methane flux from hydrate-bearing sediments.