NEGATIVE Оґ13C EXCURSIONS IN FORAMINIFERAL RECORDS: THE HOLOCENE HISTORY OF METHANE EVENTS IN THE CENTRAL SEA OF OKHOTSK
S.P. Pletnev1, Yonghua Wu2, A.V. Romanova3, V.K. Annin1, I.V. Utkin1, O.F. Vereshchagina1
1V.I. Il’yichev Pacific Oceanological Institute, Far Eastern Branch of the Russian Academy of Sciences, ul. Baltiiskaya 43, Vladivostok, 690041, Russia
2First Institute of Oceanography, Jindao, 266061, China
3Far East Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, pr. 100-letiya 159, Vladivostok, 690022, Russia
Keywords: Benthic and planktonic foraminifera, oxygen and carbon isotope compositions, methane, methane emission, Sea of Okhotsk
Abstract
Several negative δ13C excursions in benthic foraminifera from gas-bearing core LV50-05 sampled offshore on the eastern slope of Sakhalin Island, Sea of Okhotsk, in an area of active methane seepage record the local history of methane events (ME). The core chronostratigraphy has been contsrained from AMS 14C ages and biostratigraphic data. Benthic foraminifera ( Nonionellina labradorica and Uvigerina parvocostata ) from some core intervals show normal marine δ13C values (about -1‰), but some intervals are marked by extremely depleted compositions as low as -34.5‰ δ13C (relative to VPDB). The negative δ13C excursions are interpreted as a record of seabed methane emanation during primary and secondary biomineralization of carbonate foraminifera. The results reveal four Holocene methane events (ME) in the area: two brief (ME-1 at 700-900 yr BP and ME-2 at 1200-1400 yr BP) and two long (ME-3 at 2500-4700 yr BP and ME-4 at 7400-10000 yr BP) events.
DOI: 10.15372/RGG2019107
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