Sinian-Cambrian Boundary Section at Meishucun, Jinning, Yunnan

This is a geological boundary section located on the Tuan Shan hilltop, Xiao Wai Tou Shan and Baodaowan areas at the Kunyang phosphorus mine site northwest of Meishucun Hill Village. It is an important geological section for studies of the Sinian-Cambrian boundary, and it was selected by the International Working Group on the Precambrian-Cambrian Boundary as China’s international boundary stratotype. The section includes sedimentary layers of phosphate, carbonate and clastic rocks called the Yuhucun Formation and Qiongzhusi Formation. Algae fossils, trace fossils, small shell-bearing fauna fossils and trilobite fossils are present from the bottom to the top. Three boundary points were proposed for the base of the Cambrian: (1) The bottom of the first trilobite fossil bed, which corresponds to the bottom of the oldest Parabadiella trilobite fossil layer in the black shale bed in the Yu’an Member of the Qiongzhusi Formation; this early proposal was not adopted. (2) The bottom of the...