PHYSIOGRAPHIC STAGES. 99 



movements with erosion is presented. The climatic factor is also recog- 

 nized and applied to aid in fixing the date of initial loess deposition. 



Four phases are distinguished : the first or oldest is a peneplain, a very 

 ancient and also very aged form, which is known from various parts of 

 northern Asia, and a remnant of which we named from its preservation in 

 the highest dome of the Wu-t'ai-shan, the Pei-t'ai form, developed during 

 the Pei-t'ai cycle. 



The next younger is a surface of mature erosion, which replaced any 

 older features in most of the areas we saw. It is a surface of moderate 

 relief, characterized by wide valleys and hills rarely a thousand feet high. 

 It is typically developed near T'ang-hien, Chi'-li, and we call it the T'ang- 

 hien stage. 



The third phase was one of aggradation in North China, the time of the 

 early loess deposits. The moderate relief of the preceding stage was to a 

 notable extent buried beneath the Huang-t'u, a formation consisting of 

 wind-sorted waste from the deserts of central Asia, whence the dust was 

 brought chiefly by rivers. The partly buried hills along the western mar- 

 gin of the Great Plain of eastern China afford an illustration of the aspect 

 of Chi'-li, Shan-si, and northern Shen-si at the time. The great mountain 

 ranges had not attained their present height. Attributing the desert waste 

 to the climatic change from Tertiary to Pleistocene, which may have 

 become effective in late Pliocene to the extent observed, we assign this 

 phase to that time and to the opening of the Pleistocene. We designate it 

 the Hin-chou stage, after the Hin-chou loess basin in Shan-si. 



The fourth and present physiographic stage we named for North China 

 the Fon-ho, from the river of that name, which, though older than the Fon- 

 ho epoch, still flows through Shan-si among characteristic features of that 

 stage. For South China, where the physiographic relations are somewhat 

 different, we applied the name Yang-tzi to what is very nearly or precisely 

 the same time division. It is an epoch of very decided mountain growth in 

 China; and if, as I believe, the principal continental upwarp of central Asia 

 is largely of the same date, it is the time of one of the most remarkable 

 diastrophic movements of which we have knowledge. It appears to fall 

 chiefly within the Quaternary, but may extend back into the Pliocene. 

 The typical features are warped and faulted surfaces, which result from 

 downward and upward movements of adjacent masses that underlie basins 

 and graben or constitute plateaus and mountain ranges. The amount of 

 sculpture is relatively slight, but great canyons like the Yang-tzi gorges have 

 been cut by antecedent rivers. 



Having thus summarized the results of our observations in China, I 

 suggest their broader relations. 



