Abstract: When sorting stratigraphic units,it is found that the Muzuo Forrnation defined by predecessors in fact includestwo sequences of strata and that the time span of the Iower sequence-the series of metavolcanic rocks and pyro-clastic-continental clastic rocks-should be Qingbaikou’ an. So it is necessary to separate it from the Muzuo Forma-tion and establish a new lithostratigraphic unit the Lower Kasha Formation. This paper describes the stratotypesection of the Lower Kasha Formation.