湖北宜昌远安真金和界岭奥陶系牯牛潭组顶部的牙形刺及其地层意义（英文）

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。

ORDOVICIAN CONODONTS FROM THE TOP PART OF THE KUNIUTAN FORMATION AT THE ZHENJIN AND JIELING SECTIONS OF YUAN'AN,YICHANG,HUBEI PROVINCE AND THEIR STRATIGRAPHICAL SIGNIFICANCE

This paper describes the conodonts from the top part of the Ordovician Kuniutan Formation at the Zhenjin and Jieling sections of Yuan'an County,Yichang, Hubei Province.They include Baltoniodus prevariabilis,Drepanoistodus venustus,Panderodus gracilis,Periodon aculeatus,Protopanderodus calceatus,P.varicostatus?,Yangtzeplacognathus foliaceus, and Y. protoramosus, which are referred to the Ordovician Darriwilian Yangtzeplacognathus protoramosus Subzone of the Pygodus serra Zone.This conodont fauna can be correlated with that from the top part of the same formation at the Huanghuachang section of Yichang,and at Waigangou section of Tangshan,Nanjing,and the top part of the Yijianfang Formation at the Yangjikan section,Kalpin County of Xinjiang.However,it is worthy of noting that the recorded fauna is 3conodont zones(the Pygodus anserinus,Yangtzeplacognathus jianyeensis,and Baltoniodus variabilis zones in ascending order),lower than that of the top part of the Kuniutan Formation at the Dacao section of Chengkou,Chongqing.This indicates a diachronous nature of the top part of the Kuniutan Formation in the Yangtze plateform of China.