Eocene Ostracoda Biostratigraphy In Chachang,yadong,Tibet

The Tethys-Himalayan tectonic domain attracts the attention of geoscientists around the world because of its unique and complex crustal structure.As one of the most important geological tectonic events since the end of the Mesozoic era,the collision between the Eurasian plate and the Indian plate was the main reason for the uplift of the Himalayas and the Tibetan Plateau.During the collision process,the two plates did not completely withdraw from the sea,in southern Tibet,therefore,there was a residual basin in southern Tibet.The study of the residual basin can provide a good basis for defining the collision time.The Zhepure Formation in the Yadong area of southern Tibet is the youngest marine sedimentary.The study of its geological age can infer the time of the disappearance of the residual basin and provide time constraints for the final extinction process of Tethys in Tibet.Micropaleontology plays an important role in biostratigraphic division,resource exploration,environmental evolution and paleogeography restoration.Ostracoda is one of the important means of stratigraphic division and correlation in Mesozoic and Cenozoic.In this thesis,the ostracoda fossils from the Sand-shale Member of the Zhepure Formation in the Chachang section,Yadong.A total of 74 samples were processed and 22 species of 14 ostracoda genera were identified.Two ostracoda assemblages have been establishe: Monsmirabilia subovata-Pokornyella acrocaudalis assemblage and Hermanites grophica-Monsmirabilia ovata assemblage.According to the characteristics of Ostracoda assemblages,it is suggested that the age of the Zhepure Formation should be the early Eocene Ypresian-Priabonian period.