Early Paleozoic whole-rock Ce anomalies and secular eustatic changes in the Upper Yangtze region

The 65 whole-rock REE samples studied come from the classic sections of Ear ly Cambrian to Early Silurian in the Yichang area, Hubei Province. REE conc entrations tested on ICP-AES are normalized to the North American Shale Com posite (NASC), and Ce anomaly values are calculated based on log[3Ce(n)/(2L a(n)+Nd-n)]. With the whole-rock Ce anomaly used as a quantitative index of sea-level changes, 5 prominent eustatic circles are recognized, and a good corresponding relationship is observed between the black shale episodes an d the transgressive events. On account of the global distributions of coeva l black shares and the specified paleogeographic background of South China, a genetic hypothesis based on the model of O-2-minimum zone expansion is s uggested for the Early Paleozoic multi-episode black shales in South China.