Cascadia Margin

IODP Preliminary Report Leg 311 (Northern Cascadia Margin)... 

IODP Expedition 311 Scientists, Cascadia Margin gas hydrates. IODP Prel. Rept., 311. doi 10 2204/iodp. pr.311. (2005). 

P9a Northern Cascadia Margin Samples and Spence(1992) Pohlman et al. (2005)... 

Hydrate formation from gas dissolution of rising water Hyndman and Davis (1992) proposed that as methane-unsaturated water rises, it becomes saturated at lower pressures. As the saturated (or supersaturated) water passes through the phase stability zone, hydrate formation occurs without a free gas zone. This model results in a maximum hydrate concentration at the three-phase (BSR) boundary with a successively lower hydrate amounts above the BSR as was shown to be the case in Cascadia Margin ODP Drill Sites 889 and 890 by Hyndman et al. (1996). 

Table 7.7 contrasts FHF and DLF hydrates. It should be emphasized that both hydrates are end-member types with the frequent occurrence of mixed types. For example, while Table 7.7 typifies Blake Ridge as DLF hydrates and Barkley Canyon as FHF hydrates, there is often a mixture of both types as shown in the Leg 204 study in the Cascadia Margin. As a second example, while the Gulf of Mexico is normally known for FHF hydrate deposits, Hutchinson et al. (2004) provide evidence for some elements that have DLF characteristics. 

P9 Cascadia Margin off Vancouver 30 km wide band, 300 m subbottom Hyndman and Spence (1992) Yuan et al. (1996)... 

P8 Cascadia Margin off Oregon 73 m subbottom depth undefined area Westbrook et al. (1994)... 

Luff, R., Wallmann, K., 2003. Fluid flow, methane fluxes, carbonate precipitation and biogeochemical turnover in gas hydrate-bearing sediments at Hydrate Ridge, Cascadia Margin Numerical modeling and mass balances. Geochim. Cosmochim. Acta 67 (18), 3403-3421. 

Heeschen, K., Trehu, A., Collier, R.W., Suess, E., and Rehder, G, 2003. Distribution and height of methane bubble plumes on the Cascadia Margin characterized by acoustic imaging Geophysical Research Letters, 30 10.1029/2003GL016974. 

Torres, M.E., Wallmann, K., Trehu, A.M., Bohrmann, G, Borowski, W.S., and Tomaru, H., 2004. Gas hydrate growth, methane transport, and chloride enrichment at the southern summit of Hydrate Ridge, Cascadia margin off Oregon. Earth and Planetary Science Letters, 226 225-241. 

Westbrook, G.K., Carson, B., Musgrave, R.J., et al. 1994. Proceedings, initial reports. Ocean Drilling Program, Leg 146 Cascadia Margin, 611 pp. 

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