川西金沙江—带志留—泥盆纪然西组的建立

THE ESTABLISHMENT OF THE SILURIAN-DEVONIAN RANXI FORMATION IN THE VICINITY OF THE JINSHA RIVER,WESTERN SICUAN

川西金沙江一带的志留—泥盆纪地层，前人没有建立岩石地层单位。笔者通过地层清理，发现该套地层层序及与上覆地层接触关系清楚，岩性特征明显，且含一定生物化石，具备建立岩石地层单位条件。根据前人所测白玉县山岩乡然西剖面，将上述地层正式建组───然西组。本文对然西组层型剖面进行了描述。

No lithostratigraphic unit has been set up for the Silurian-Devonian strata in the vicinity of the Jinsha River,western Sichuan. Through sorting stratigraphic units,the author found that this sequence of strata has clear contact relationships with its overlying strata,shows distinct lithologic features and contains certain fossils,so it meets the conditions for establishing a lithostrtqtigraphic unit.So with the Ranxi section of the Baiyushan Rock Formation measured by predecessors as a holostratotype section,a normal formation──the Ranxi Formation──was estab-lished for the above-metioned sequence of strata. This paper describes the stratotype section of the Ranxi Forma-tion.