Carboniferous-Permian Carbon Isotope Stratigraphy of Succession from Xainza (Tibet), China

Abstract

Carbon isotopic composition recorded several major events in the development and evaluation of the earth. Possibly, Carbon isotopic composition is the cause or the result of such big events. Carboniferous-Permian, as the most important turning point of earth development history, developed the biggest Phanerozoic glacier whose drift beds are widely distributed among the various ancient Gondwanaland continental blocks. We can carry out comparative study with each continental block. Good outcrop of Chinese carboniferous sequence and continuously developed stratum are fit for building chronostratigraphic framework and proceeding global comparative studies. The paper researches on carbon and oxygen isotope of the samples from Carboniferous-Permianstratigraphic boundary which are collected from the east Yongzhu bridge of Xainza County in Tibet Autonomous Region, China. Moreover, we compare it with carbon isotope curve of the same period coming from the Kongshan section in Jiangsu Province, the Zhongdi sectionand Naqing section in Guizhou Province of the south China. It is the first time to propose the concrete beds location of Carboniferous-Permian stratigraphic boundary of Xainzadistrict which is one set of yellow limestone below the LagaFormaion.In previous studies, index fossils were not found in LagaFm. It was roughly defined as a diachronous lithostratigraphic unit simply by 26 genera of brachiopods and 8 genera of rugose corals. In this paper, based on a comparative study with carbon isotope curves, the Laga Fm. is identified as a time-transgressive formation.