论云南武定旧城组的地质时代

Age of the Jiucheng Formation of Wuding,Yunnan

通过地层层序与生物群分析，云南武定地区旧城组的时代相当于早泥盆世Ｅｍｓｉａｎ晚期。武定地区泥盆系连续沉积，旧城组之下为具“坡脚动物群”的坡脚组，与郁江组相当。旧城组应是四排阶的沉积，产有丰富的节甲鱼类化石，面貌与欧洲及澳大利亚同期的节甲鱼类相近。海口组应归入中泥盆世早期的Ｅｉｆｅｌｉａｎ阶，大致相当于湖南的跳马涧组。

The Jiucheng Formation in Wuding, Yunnan, is distingushed by its fish fossils, which include arthrodires Jiuchengia, Yinostius, Xiangshuiosteus, Exutaspis, Holonema and some antiarchs. Its age was considered as Eifelian, Middle Devonan. In this Paper,the comprehensive analysis of the Jiucheng Formation is made, and its geological age is referred to the Late Emsian, Early Devonian.In Wuding, the sequence of Devonian strata is continuous, and there is not any sedimentary gap between the Jiucheng Formation and the underlying Pojiao Formation or the overlying Haikou Formation. The Pojiao Formation, with the typical Pojiao fauna, corresponds roughly to the Yejiang Formation, and its age should be Early Emsian. The Haikou Formation of Yunnan corresponds to the Tiaomajian Formation of Hunan, since both formations yield Hunanolepis- Bothriolepis assemblage. On t he basis of the conodonts,tentaculitesand spore-pollen assemblages, the Qiziqiao Formation, which overlies the Tiaomajian Formation, has been considered to be of Early Givetian. Consequently, the Tiaomajian Formation should be of Eifelian in age. The same is true of the Haikou Formation. With regard to the early vertebrate fauna, the arthrodires of the Jiucheng Fomation are quite suggestive of those of the Verdalen Member and Grey Hock Formation in Spitsbergen, and of the Murrumbidgee Group in Australia. The age of those arthrodires in Europe and Australia is Late Emsian, Early Devonian,suggesting the Late Emsian age of the Jiucheng Formation in Wuding, Yunnan.