10 GEOLOGICAL IlESEAUCHES IN 



V 



CHAPTER III. 

 OBSERVATIONS IN THE PROVINCE OF CHI H LI. 



Along the western boundary of the provmce of Chihli, the great delta-plain is 

 bounded by the outliers of the northwestern belt of N. E. S. W. ridges. The 

 foundation on which rest the limestone and volcanic rocks of Northern Chihli, 

 Shansi, and Shensi, consists of granite and the metamorphic schists; and where 

 this foundation forms the northwestern limit of the delta-plain, it forms also the 

 southeastern edge of the skeleton of the great table-land of Central Asia. 



We have seen that, in Central China, the granitic and metamorphic rocks that 

 support the limestone and Coal measures, rise to the level of the river, in, to say 

 the least, only rare instances, and then as the axial cores of ridges; the great 

 thickness of the overlying rocks making it highly probable that, from western 

 Sz'chuen to the Pacific, this foundation lies far below the level of the sea. But if 

 we cross the mountains from the delta-plain to the highlands of Mongolia, we find 

 that the surface of the granitic substructure lies everywhere above the sea, and 

 probably nowhere at a less height than 1000 feet. Were the limestone and 

 younger rocks removed, the country would present the appearance of a table-land 

 ribbed with high N. E. S. W. ridges, and very similar to southern Mongolia if we 

 suppose that divested of its lava beds. 



Along the edge of the plain, the limestone floor of the Coal measures rises 

 abruptly from under the delta-deposit, and forms, so to speak, the eastern facing of 

 these mountains. At the entrance to the Nankau pass, the strata trend N. 60° E. 

 and dip about 40° to S. E. Five or six miles farther west, it is followed by granite, 

 and between these points, strike and dip are very irregular. From the pass, the 

 limestone stretches away to N. E. toward Jehol, and to S. W., facing the plain, 

 toward Shansi. 



While the Coal measures probably remain intact imder the delta-plain, from the 

 mountains of Shantung to those of Chihli, they exist in these latter only in scattered 

 basins, where they have been partially preserved, by folds of the limestone, from 

 denudation. The most important instances of this kind facing the plain, are the 

 basins of Wangping (hien) and Fangshan (hicn) west of Peking, and of Pingting 

 (chau) in Shansi. 



The basins of Wangping (hien) and Fangshan (hien) lie in the mountains west 

 of Peking, where, rising from under the plain, they occupy synclinal folds of the 

 limestone, and are probably only two arms of a larger basin concealed under the 

 younger deposits to the eastward. The Wangping basin extends due Avest more 

 than thirty miles, with a breadth of about twelve miles. Along a great part of its 



