Origin of the Dolomitic Ooids Formed in the Pliocene Shizigou Formation in the Qaidam Basin, Northern Tibet Plateau and Implications for Climate Change

The concentric layers of ooids from the modern environment are mostly aragonite and those ancient calcite Mg-calcite. Dolomitic rare usually formed via replacement or calcite. Here, dolomitic were found in Pliocene Shizigou Formation Qaidam Basin, Northern Tibet Plateau. This paper focuses on whether is a primary precipitate. Optical microscope scanning electron observation, combined with X-ray diffraction cathodoluminescence analyses, indicate that mineral ooid cortices poorly ordered dolomite. Extracellular polymeric substances pyrite ooids, indicating microbe participation was involved formation ooids. Firstly, grow offshore lake floor. Due to involvement sulfate-reducing bacteria dissolved silica, nanominerals precipitated extracellular substances. Then, transported strong hydrodynamic surf zones, where random abraded form flattened plates as new polished layer. In addition, comparison between carbon oxygen isotopic compositions minerals different periods lakes had lower salinity more humid than Pleistocene lakes. Therefore, may be an effective proxy for reflecting climatic change uplift history