甘肃省西大沟群

THE XIDAGOU GROUP IN GANSU

孙健初（１９３６）创名西大沟系，斯行健等（１９６２）改名为西大沟群。由于种种原因，后人所定西大沟系或西大沟群，均无一定标准；它在北祁连地区三叠系陆相地层的位置，意见分歧已久。笔者经过两年的考证与调查，证实现今西大滩河就是原西大沟系创名地。在此，重新补测了剖面，为建立北祁连地区三叠系陆相岩石地层序列奠定了基础，还进一步介绍了该群有关岩五地层单位宏观特征及分界标志。

Sun Jianchu(1936) coined the term“Xidagou system”,and later Si Xingjian et al.(1962)changed the term in-to the“Xidagou Group”.For a variety of reasons ,there are no definite criteria for defining the Xidagou System or Xidagou Group.Divergent views have long existed as to its podition in Triassic continental strata in the northern Qilian area.Through two years of investgations the author has demonstrated that the present Xidatan River is pre-cisely the naming place of the original Xidatan(‘gou’ means gully in Chinese)(Sun Jianchu,1936) and measured a new section,thus laying a foundation for establishing a sequence of Triassic continental strata in the northern Qil-ian area. This paper also introduces the macroscopic features and division indicators of the lithostratigraphic units of this group.