Li Qing et al. (2010): Stable carbon isotopes of benthic foraminifers from IODP Expedition 311 as possible indicators of episodic methane seep events in a gas hydrate geosystem

Leg/Site/Hole:
IODP 311
IODP 311 U1325
IODP 311 U1326
IODP 311 U1327
IODP 311 U1329
Identifier:
2010-093227
georefid

10.2110/palo.2010.p10-011r
doi

Creator:
Li Qing
China University of Geosciences, Key Laboratory of Biogeology and Environmental Geology, Wuhan, China
author

Wang Jiasheng
Qingdao Institute of Marine Geology, China
author

Chen Jianwen
author

Wei Qing
author

Identification:
Stable carbon isotopes of benthic foraminifers from IODP Expedition 311 as possible indicators of episodic methane seep events in a gas hydrate geosystem
2010
Palaios
Society for Sedimentary Geology, Tulsa, OK, United States
25
10
671-681
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 per mil to -2.74 per mil, -1.11 per mil to -2.62 per mil, -0.51 per mil to -2.75 per mil, -0.58 per mil to -2.71 per mil, and -0.22 per mil to -3.32 per mil respectively) and positive oxygen isotopic anomalies (3.27 per mil to 4.91 per mil, 3.16 per mil to 4.78 per mil, 3.37 per mil to 4.88 per mil, 3.45 per mil to 4.88 per mil, and 3.4 per mil to 4.88 per mil 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 caused by diagenesis and authigenic carbonate precipitation. Carbon and oxygen isotopic values of these two species at Site U1327, U1328, and U1329 show episodic stratigraphic fluctuations, suggesting episodic gas hydrate dissociation and methane release possibly related to 100 ka sea-level fluctuations. delta (super 13) C of these two species at Site U1325 and U1326 at the stage of gas hydrate formation show one and two events of methane release respectively, indicating methane seeps occurred in the recent millennium probably because of the lowered sea level. The negative delta (super 13) C excursions and positive delta (super 18) O anomalies of benthic foraminifers could be indicators of episodic methane seep events associated with gas hydrate dissociation in marine gas hydrate geosystems.
English
Serial
Coverage:Geographic coordinates:
North:48.4700
West:-127.0300East: -126.4100
South:48.3900

Quaternary geology; Isotope geochemistry; benthic taxa; Bulimina; Bulimina mexicana; Buliminacea; C-13/C-12; carbon; Cenozoic; East Pacific; Expedition 311; Foraminifera; gas hydrates; gas seeps; Integrated Ocean Drilling Program; Invertebrata; IODP Site U1325; IODP Site U1326; IODP Site U1327; IODP Site U1329; isotope ratios; isotopes; microfossils; morphology; North Pacific; Northeast Pacific; O-18/O-16; oxygen; Pacific Ocean; Pleistocene; Protista; Quaternary; Rotaliina; sea-level changes; SEM data; stable isotopes; statistical analysis; tests; Uvigerina; Uvigerina peregrina; Uvigerinidae;

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