THE ESTABLISHMENT OF THE ORDOVICIAN DAHEBIANFORMATIONIN THE VICINITY OF XIAOJIN,SICHUAN PROVINCE

There outcrops a sequence of neritic clastic rocks and carbonate rocks at Dahebian,Xiaojin county,and Xia-zhuang of Wenchuan , Lixian county,Sichuan province.This sequence of strata shows distinct lithologic features andclear stratigraphic relationships with its overlying and underlying strata and is divisable and mappable. No formalstratigraphicunit has been set up for it. In 1992 ,the author found fossil crinoid stems in crystalline limestone at Xia-zhuang,Wenchuan,which were determined to be of Ordovician age. Therefore,a lithostratigraphic unit──the Da-hebian Formation──has been established for this sequence. This paper described the stratotype section of thisformation.