The black shale series in Early Cambrian Hetang Formation and Huangboling Formation are well developed in Shitai area, Anhui Province. They have distinguished REE geochemical characteristics, i.e., total REE contents are very low; LREE are more abundant than HREE; δEu=0.81~2.32 (1.1 on average), δCe=0.52~0.97 (0.77 on average). The δEu and δCe values change regularly, i.e., the δCe values decrease and then increase from bottom to top in the sedimentary section, but with an increasing tendency on the whole, whereas things are just the opposite for δEu values. REE geochemical characteristics and their systematic changes in the sedimentary section suggest that there existed a process of ingression-regression in this area in the Early Cambrian period. The black shale series resulted from the mixing between normal seawater sediments and hot seawater sediments and were deposited under the transitional condition from reduction to semi-reduction and weak oxidation in a shallow-sea clinoform zone of a relatively deep sea environment with dry climate.
