宁夏香山群的时代探讨

香山群主要分为４个亚群，在第一和第三亚群的灰岩扁豆体中采获三叶虫化石。香山群与下伏中奥陶统来钵山组关系为整合接触，不整合伏于志留系、泥盆系、石炭系之下。从沉积相序分析，香山群与下伏米钵山组表现为从大陆斜坡相至深海盆地相的特征。将香山群重新厘定，置于中奥陶统上部。

THE AGE OF THE XIANGSHAN GROUP IN NINGXIA

The Xiangshan Group may be divided into four subgroups.Trilobite fossils were collected from lenticular limestone bodies in the first and third subgroups.The Xiangshan Group is underlain conformably by the Middle Ordovician Miboshan Group and is in turn ovelain unconformably by the Silurian,Devonian and Carboniferous.Analysis of sedimentary facies sequences indicates that the Xiangshan Group has inseparable genetic relation to the lower Miboskan Formation,which is manifested by the change from the slope facies to abyssal basin facies.So the authors revise the stratigraphic position of the Xiangshan Group and place it in the upper part of the Middle Ordovician.