BENTHIC FORAMINIFERA AND STABLE ISOTOPIC COMPOSITION OF GAS HYDRATE-BEARING SEDIMENTS FROM SHENHU AREA IN THE NORTHERN SOUTH CHINA SEA
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摘要: 为评价水合物甲烷对底栖有孔虫群落结构和同位素的影响,对南海北部神狐海域获取天然气水合物的钻孔BY3岩心,进行底栖有孔虫群落结构和稳定同位素分析,发现含水合物层底栖有孔虫丰度、分异度下降,群落中以内生种占绝对优势,有孔虫破碎率增加;与不含水合物层中的底栖有孔虫相比,含水合物层的底栖有孔虫碳同位素值出现较明显的负偏移。含水合物层中的Uvigerina spp.、Cibicides spp.和Oridorsalis spp.的δ13C平均值分别为-1.61‰、-0.79‰和-1.80‰,而在不含水合物层它们的δ13C平均值分别为-0.88‰、-0.27‰和-1.04‰;其中Uvigerina spp.和Oridorsalis spp.的δ13C最轻值均出现在含水合物层,分别为-1.83‰和-2.29‰。这些说明底栖有孔虫在生长和埋藏过程中可能受到沉积物中甲烷水合物形成和演化的影响。Abstract: The successful gas hydrate expedition from Shenhu area in the northern South China Sea, provides an opportunity to study the influence of gas hydrate methane on the benthic foraminifera and their stable isotopic composition. In this study,benthic foraminifera and their carbon isotopes in hole BY3 from the Shenhu area were reported.The results show there has no obvious distinction in benthic foraminifera assemblage composition between gas hydrate-bearing sediments and non-gas hydrate-bearing sediments. The carbon stable isotope analyses of species(Uvigerina spp., Cibicides spp.and Oridorsalis spp.) reveal a distinction in foraminifera between gas hydrate-bearing sediments and non-gas hydrate-bearing sediments. Uvigerina spp., Cibicides spp.and Oridorsalis spp.collected from gas hydrate-bearing sediments exhibit highly variable and strongly depleted δ13C values, with values as -1.61‰,-0.79‰ and -1.80‰ respectively; and mean values are -0.88‰,-0.27‰ and -1.04‰ respectively from non-gas hydrate-bearing sediments.The extremely negative δ13C values of Uvigerina spp.and Oridorsalis spp.are -1.83‰ and -2.29‰ respectively,which occurred in gas hydrate-bearing sediments.The studies imply that the high carbon isotopic excursion were affected by gas hydrate methane.
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Key words:
- benthic foraminifera /
- assemblage composition /
- carbon isotopes /
- gas hydrate /
- South China Sea
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