Tian Gan, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China, Taiyi Luo, Institue of Geochemistry, Chinese Academy of Sciences, Guiyang, China, Ke Pang, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China, Chuanming Zhou, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Key Laboratory of Economic Stratigraphy and Palaeogeography, Nanjing, China, Guanghong Zhou, School of Geography and Resources, Guizhou Education University, Guiyang, China and Bin Wan, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, State Key Laboratory of Paleobiology and Stratigraphy, Nanjing, China