Abstract:There are a dolomite with limestone section which is with scores of meters thick in the upper part of Chaomidian formation.According to the definition of Sanshanzi formation given by“stratigraphic sortout”,that is,the bottom boundary of Sanshanzi formation is it when a large set of and continuous dolomite comes,so this section doesn t belong to Sanshanzi formation,and it should belong to Chaomidian formation.However,not only dolomite in Sanshanzi formation contains nodular chert,but also in large amount lim...