Abstract
Abstract Integrated Ocean Drilling Program (IODP) Expedition 311 at the Cascadia Margin, northeastern Pacific, provides an excellent opportunity to study the response of carbon isotopic compositions of benthic foraminifers to episodic methane seep events in a gas hydrate geosystem. The shallow infauna benthic foraminifer species Uvigerina peregrina and Bulimina mexicana collected from five sites (U1325, U1326, U1327, U1328, and U1329) exhibit dramatic negative carbon isotopic excursions (−0.75‰ to −2.74‰, −1.11‰ to −2.62‰, −0.51‰ to −2.75‰, −0.58‰ to −2.71‰, and −0.22‰ to −3.32‰ respectively) and positive oxygen isotopic anomalies (3.27‰ to 4.91‰, 3.16‰ to 4.78‰, 3.37‰ to 4.88‰, 3.45‰ to 4.88‰, and 3.4‰ to 4.88‰ respectively). Results indicate that gas hydrate dissociation influenced the dissolved inorganic carbon of the pore water via anaerobic oxidation of methane. SEM analysis of foraminifer tests and the comparative carbon isotopic analysis of previous works on this subject indicate minimal alteration...
Published Version
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