贵州思南奥陶纪末至志留纪初大息场组的笔石

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: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)和Korenograptus laciniosus(Churkin and Carter,1970)。自下而上可识别出相当Dicellograptus 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.chiai(Mu)之外,其它都是全球广布的物种。

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

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).