Researches on seawater REE over the world indicate that REE in the seawaterfrom various environments are different to a certain extent. Marine siliceous depos-its also exhibit a similar REE pattern to those of their surrounding seawater, inwhich Ce anomaly is the most obvious marker. As shown by studies on REE in theancient cherts of the known depositional environments, cherts from the continental-margin environment exhibit slight negative Ce anomaly or positive Ce anomaly andcherts from the ocean--basin environment exhibit obvious Ce anomaly, while chertsfrom the mid--oceanic ridge environment show intense negative Ce anomaly. There-fore the characteristics of the chert REE pattern can be used to distinguish differ-ent depositional environments. According to the Ce anomalies, the thickbedded che-rts occurring extensively in the Cambrian--Ordovitian in southern Jiangxi are infer-red to be formed in a transitional zone between the continental margin and theocean basin.