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本文描述了采自湖北宜昌远安真金和界岭剖面奥陶系牯牛潭组顶部的牙形刺,它们有Baltoniodus prevariabilis,Drepanoistodus venustus,Panderodus gracilis,Periodon aculeatus,Protopanderodus calceatus,P.varicostatus?,Yangtzeplacognathus foliaceus和Y.protoramosus等,确认宜昌地区牯牛潭组顶部应归属于奥陶系达瑞威尔阶Pygodus serra带之Yangtzeplacognathus protoramosus亚带,并可与宜昌黄花场剖面和南京汤山外杆沟剖面同名组顶部及新疆柯坪羊吉坎剖面一间房组顶部的牙形刺带相对比。同时,它要比重庆城口大槽剖面牯牛潭组顶部的牙形刺带低3个带(Pygodus anserinus带至Baltoniodus variabilis带),这一事实也说明了牯牛潭组顶部在中国扬子地台的穿时性。
In this paper, we describe the conodonts collected from the top of the Ordovician Qiu Nantan Formation in Yuanan Zhenjinhejieling Section, Yichang, Hubei Province. They are Baltoniodus prevariabilis, Drepanoistodus venustus, Panderodus gracilis, Periodon aculeatus, Protopanderodus calceatus, P. varicostatus ?, Yangtzeplacognathus foliaceus and Y.protoramosus and so on, confirming that the top of the Yanniu Formation in Yichang is attributable to the Yangtzeplacognathus protoramosus subduction zone of the Pygodus serra belt of the Ordovician Darwarian Order, Top and Keping Yang Jikang Xinjiang section of the top of a group of condyloma with relatively. In the meantime, it is lower than the three conodonts (Pygodus anserinus to Baltoniodus variabilis) at the top of the Gushi Nintan Formation in Chongqing’s Goukou section. This fact also shows that the top of the Yanniutan Formation in the Yangtze Delta of China Wear time.