对香山群时代的商榷
Discussion on the Age of the Xiangshan Group
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摘要: 分布于宁夏中部的香山群划分为1~4个未命名的亚群,第一亚群中的薄层灰岩所含的三叶虫Holocephalites punctatus Zhou,Olenoides ningxiacus Zhou,Peronopsis ovalis Zhou组合时代为中寒武世,牙形石Furnishina asymmetrica Müller,F.furnishi Müller为晚寒武世,指示第一亚群的时代为中—晚寒武世。牙形石Cordylodus proavus Müller和Oistodiform分子在第二亚群的发现表明这个亚群的时代最可能属于晚寒武世—早奥陶世。然而,整个香山群的精确时代仍不能完全确定,因为它的第三亚群和第四亚群不是化石稀缺就是不含化石。Abstract: 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.
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Keywords:
- Ningxia /
- Xiangshan Group /
- Middle to Late Cambrian /
- Early Ordovician
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