SINO-MONGOLIAN FRONTIER 



on the western margin of the same plain can only 

 be explained by the existence of a fault, such as I 

 have just described. Indeed there is no reason 

 why a fault should not occur here, for further 

 south and in an almost direct line with it a similar 

 fault occurs, running in a direction slightly west 

 of south, along the eastern side of the O Shan. 

 In this also the downthrow is on the east. Richt- 

 hofen, also, came to the conclusion that there was a 

 fault along the north-western margin of this plain. 



We put up at Huang-t'u-tsai, the place which 

 gives its name to the Huang-t'u formation, a name 

 given by Bailey Willis to the loess and various 

 other Quaternary deposits of North China. 



The following day we continued down a dry 

 stream bed and finally came out upon the T'ai-yiian 

 Fu plain once more. 



PART 3 



The Geology of the Upper Fen Kg Basin, 

 Western Shansi 



The geology of the country lying north-west 

 of the T'ai-yiian Fu plain, owing to the extensive 

 fault running down its north-western margin, is 

 in many ways a repetition of that of the country 

 traversed by the Chen-T'ai Railway. A new 

 feature, however, is presented in the form of 

 extensive outcrops of plutonic and metamorphic 

 rocks. 



263 



