Synthetic Study In Cold Seep Area, Shigatse, Tibet

The methane leakage in paleo-ocean cold seepage area profoundly affects on marine deposits. Widely developed in continental margin slope, cold seepage is closely related with the methane greenhouse gas, the biological resources under extreme conditions and natural gas hydrate resources, which has been widely concerned by the geoscientists in recent years. Authigenic carbonates or fossils representing ancient cold spring activities has been reported in the Precambrian to Quaternary strata in the world, but few in China. In this thesis, the Late Cretaceous seep carbonates in Shigatse, Tibet has been studied in such aspects as isotope geochemistry and biostratigraphy, the focus of which is the age determination of the seep carbonate strata.Mostly like tuberculosis/nodular, the cold seepage carbonatites in Shigatse area were devolped in the turbidites in the Shigatsefore-arc Basin, which are usually in such shapes as peanut, ginger or tubular, with a diameter of several centimeters to several meters. Mud crystallite and mass, and pyrite framboids were found in the interior of the cold seepage carbonatite. In addition, with an obvious negative bias(-23.8%), their δ13C value is obviously different from normal marine sediments.A certain number of microfossils mainly as foraminifera and radiolarians are gained in this work from the tuberculosis and its surrounding rock.Selected the fossil samples. 34 species of 18 foraminiferal genera and 22 species of 10 radiolarian genera are identified. Most of them are the common elements of the Cenomanian foraminiferal or radiolarian assemblage in Late Cretaceous, which, therefore, provides a Late Cretaceous Cenomanian age for the the seep carbonates in the study area.