西秦岭的志留系

<正> 西秦岭西段的志留系,最早由叶连俊、关士聪(1944)报道,白龙江群代表古道岭灰岩以下的一套浅变质岩系。通过近年来工作的结果,白龙江群包括下泥盆统,志留系下、中、上三统,及上奥陶统和更老的地层,如下表所示:

The Silurian of western Qinling

In this paper Baiyigou section, Nanshimengou section and Xiaolianggou section are selected as type sections of Silurian in Western Qinling. Lower Silurian Tewo Group divided into three formations, S Anzigou formation (Akidograptus zone, Diplograptus modestus zone, Pristiograptus leei zone, Pernerograptus limaiulus layer, and Rastrites approximates layer), S} Gezi formation (Monogr-aptus sedgtvickii zone, and Spirograptus turriculatus zone), S Jiannigou formation (Okaavites spiralis zone). Middle Silurian Zhouqu Group containing two formations, S21 Xiaolianggou formation (Cyrto-graptus sakmaricus zone and C. insectus zone), S22 Miaogou formation (Stegospira nucleola zone). Upper Silurian Bailongjiang Group can be subdivided into two formations, S31 Hongshuigou formation (Protathyris ingens-Atrypoidea quadrata assemblege or Spathognathotus silurica zone), S32 Nanshimengou formation (Atrypoidea-Gannania zone or Ligonodina elcgans fs. zone or Heyuncunoccras zone).