This research project was granted jointly by the National Natural Science Foundation of China(Grant No.40073001);the Key Project(97D0072)of Yunnan Provincial Foundation.
Twenty black shale samples, which are free from the influence of weathering, were collected from the Chengjiang Fauna-bearing horizon, central Yunnan Province, yielding a Pb-Pb isochron age of 534±60 Ma. Although thi...