摘要
我国的奥陶系不仅分布广泛,化石丰富,而且沉积类型相当齐全。有地台型沉积,有地槽型沉积,还有二者间过渡类型沉积。就动物群而言,有北美中大陆或北美太平洋型,也有欧洲-大西洋型,还有二者间混合类型。此外,尚有一些中国特有的生物类型。所以,研究中国的奥陶系对解决全球性奥陶纪生物沉积区系和类型的划分、对比,探索动物群的发生、迁移、演化等基本问题都具有一定的意义。
Basing on abundant materials accumulated by a host of geologists in China for over a decade,this paper deals mainly with the following respects:1.The Chinese Ordovician system,characterized by its wide distribution,a fairly complete and perfect set of stratigraphic types and rich fossil content,plays an important part in the cosmopolitan classification and correlation of the Ordovician,as well as in the research on the origin and evolution of the Ordovician biogeographic provinces.2.Taking into account lithofacial and biofacial characters and also the various types of the Ordovician for the whole world,the Chinese Ordovician is divisible into ten biostratigraphical regions,which may be grouped into the North China,the Yangtze and the Southeastern types(fig.1,chart 1).There is a striking resemblance between North American-Pacific Province and the North China type,also between the European-North Atlantic Province and Southeastern(SE)type,while the Yangtze type with well developed regional faunas represents a mixture Of the above two types.Obviously,the transional characters of the Yangtze type Ordovician are especially important in explaining the cosmopolitan subdivision and correlation of the Ordovician(chart 2).3.Synthesising the existing four main schemes of the Chinese Ordovician subdivision,on the basis of Huanghuachang section of Yichang,which will be selected as a stratotype,in association with the Ordovician in the Yangtze Gorges,the Chinese Ordovician system is subdivided into two series including 8 stages and 24 zones.These are correlated with corresponding units’of China and elsewhere in the world(chart 3).4.It is suggested that the Ordovician-Silurian boundary is best drawn at the top of the Kuanyinchiao formation with the Hirnantia-Kinnella faunas of Wufengian stage and that the Cambrian-Ordovician boundary is placed at the base of the Onychopyge-Leiostegium(Alloleiostegium)zone of the Yehli formation in North China,but in South China this boundary is placed at the base of Dictyonema sociale or Hysterolenus zone,corresponding to that between the Hirtodus hirsutus-Drepanodus simplex assemblage at the base of the Ordovician and the Proconodontus notchpeakensisOneotodus datsonensis assemblage at the top of the Cambrian in the Yangtze Gorges(chart 4).According to lithological characters and chiefly in consideration of the evolution of the faunas,the Upper-Lower Ordovician boundary is drawn either at the base of the Miaopoan Glyptograptus teretiusculus zone or at the top of the Kuniutanian Pterograptus elegans zone.
作者
汪啸风
Wang Xiaofeng(Yichang Institute of Geology and Minearal Resources,Chinese Academy of Geological Sciences)
出处
《地质学报》
1980年第1期1-8,89-92,共12页
Acta Geologica Sinica
