SINO-MONGOLIAN FRONTIER 



exposing the archaic formations beneath. On 

 the north-western side of the range the strata 

 flatten out and probably continue horizontally 

 up to and beyond the Yellow River. I did not 

 notice any sign of the Hu-t'o series, but doubtless 

 they exist. 



North-east from Wu-chia-kou the geology of 

 the country immediately adjoining the Ning- 

 wu Fu district, as already stated in my geological 

 notes in Through Shen-Kan, shows a series of 

 shale and sandstone ridges (Shansi formation), 

 the strata of which dip to the east at angles 

 varying from 30° to 80°. The ridges are formed 

 by escarpments on the west and dip slopes on 

 the east. It is in some of the higher and more 

 gentle hollows, caused by this configuration, 

 that lie the fresh-water lakes, mentioned in 

 Chapter II of this book as having been newly 

 discovered in January of 1910. 



Here again the Shansi formation is replaced 

 westward by the Ki-ch'ou formation (limestone), 

 the strata of which dip to the east at very sharp 

 angles. The outcrop of archaic rock, which has 

 extended unbroken north-east from the Wu- 

 chia-kou district, has tapered down, disappear- 

 ing altogether before Ning-wu Fu is reached. 



267 



