Discussion on the Age of the Xiangshan Group

The Xiang shan Group distributed in the middle part of the Ning xia Hui Autonomous Region has been divided into four unnamed subgroups.The occurrence of the trilobites Holocephalites punctatus Zhou, Olenoides ningxiacus Zhou,Peronopsis ovalis Zhou and conodonts Furnishina asymmetrica Müller,F. furnishi Müller from the thin-bedded limest one in its first subgroup suggests that the first subgroup of the Xiangshan Group ranges in age from the Middle to Late Cambrian.The conodonts Cordylodus proavus Müller and Oistodiform element recorded from the upper part of its second subgroup suggests that the subgroup is most likely of Late Cambrian to early Ordovician.However,the precise age of the whole Xiangshan Group is uncertain because its third and fourth subgroups are either poorly fossiliferous or no fossil srespectively.