贵州思南奥陶纪末至志留纪初大息场组的笔石

LATEST ORDOVICIAN TO EARLY SILURIAN GRAPTOLITES OF THE DAXICHANG FORMATION IN SINAN,GUIZHOU,CHINA

贵州思南奥陶纪末至志留纪初大息场组的笔石研究结果表明,大息场组共产出笔石6属7种.Styra-cograptus chiai ( Mu, 1949), Normalograptus mirnyensis (Obut and Sobolevskaya, 1967 ), Normalograptus ajjeri(Legrand, 1977).Metaclimacograptus hughesi(Nicholson, 1869).Avitograptus as 加s(Davies, 1929).Atavograptus(Jones, 1909)和 Korenograptus (Churkin and Carter, 1970) o 自下而上可识别出相当 Dicellograp-tus complexus 带、Akidograptus ascensus 带和 Cystograptus vesiculosus-Coronograptus cyphus 带的 3 个含笔石地层带。虽然大息场组的笔石动物群分异度较低,但全都是上扬子区奥陶-志留系之交的常见属种,除S. chiaiCMu)之外,其它都是全球广布的物种。

Based on graptolite beds of the Daxichang Formation in Sinan, Guizhou, investigated by Yu et al., a study on the graptolite fauna is carried out in the present paper. Seven graptolite species assigned to six genera described herein are Styracograptus chiai ( Mu, 1949 ), Normalograptus mirnyensis ( Obut and Sobolevskaya,1967 ), NormaLograptus ajjeri (Legrand, 1977 ), MetacLimacograptus hughesi (Nicholson,1869), Avitograptus avitus (Davies, 1929), Atavograptus atavus (Jones, 1909 ) and Korenograptus laciniosus (Churkin and Carter, 1970). The graptolite beds correspond to the DiceLlograptus complexus Biozone, Akidograptus ascensus Biozone and Cystograptus vesiculosus- Coronograptus cyphus Biozone in ascending order. The graptolite fauna is low-diversity composed mostly of global species throughout the Ordovician and Silurian transition, except for one species, Styracograptus chiai (Mu).