BENTHIC FORAMINIFERA AND STABLE ISOTOPIC COMPOSITION OF GAS HYDRATE-BEARING SEDIMENTS FROM SHENHU AREA IN THE NORTHERN SOUTH CHINA SEA

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.