DIVISION OF THE SILURIAN ZHUSHAN ROCK GROUP ON THE SHAANXI-HUBEI BORDER

Near the border between Shannxi province and Hubei province,there outcrops a sequence of carbonaceouspelite , pelitic clastic rocks with siliceous rocks and limestone,in which tectonometamorphism is relatively strongand fossils are rare. In 1930 Li Ji and Zhu Sen named it the Zhushan System. During 1964 to 1990,different organi-zations made different classifications of this sequence （Table 1）.The authors have worked on sorting the strati-graphic units in recent years. They hold that the great majority of this sequence is Silurian strata,whose lithologiesand fossils are different from those of the Daguiping and Meishanya Formations and whose rocks show well-devel-oped schistosity and ductile shear so that it is difficult to reconstruct its primary structure. Therefore,they assignthis sequence of strata to the Silurian Zhushan Rock Group.