PHYSIOGRAPHY AND I,OESS. IO3 



Carolina* and the case being considered generic it was proposed that an 

 extended group of heights surviving above a peneplain should be called a 

 "unaka." It is highly probable that one or more unakas will be found in 

 Asia. 



The dissection of the Pei'-t'ai peneplain (using that name tentatively 

 as a general term) has proceeded differently in different regions. Where the 

 plain is buried beneath Tertiary deposits, as on the Amur, it may be said 

 to be intact. Where it has been slightly warped or elevated to a moderate 

 height over vast areas, as in northern Siberia, it is still clearly recogniz- 

 able in the featureless plateaus. It may also be seen as a general line of 

 some mountain profiles where its surface is more steeply tilted, as in the 

 northern Altai. It is found as a mere remnant in such summits as the 

 Bural-bas-tau and Pei-t'ai. It is no longer to be seen in districts such as 

 Shan-tung, where early Tertiary faulting gave rise to acutely accented 

 relief; nor in the Ts'in-ling-shan, where warping in mid-Tertiary time 

 occasioned the development of a mature but hilly landscape. 



Throughout North China we can distinguish three phases of physio- 

 graphic development later than the Pei'-t'ai plain: the T'ang-hien, one of 

 mature erosion; the Hin-chou, one of aggradation; and the Fon-ho, one of 

 mountain growth. In central China we recognized but two: the Ts'in-ling, 

 which corresponds to the first two; and the Yang-tzi, which is probably 

 closely equivalent to the Fon-ho. 



The distinction between the T'ang-hien and the Hin-chou epochs 

 depends upon the accumulation of the early deposits of loess, which covered 

 a vast area, but an area conditioned by depression and geographic position 

 with reference to streams flowing from the basins of central Asia. These 

 conditions were by no means universal ; they were bounded on the south by 

 the hill district of the Ts'in-ling-shan; and it is probable that outside the 

 region of their extent the distinction between the epochs can not be made. 

 The equivalent phase of mature topography, which we have called the Ts'in- 

 ling phase, will then be found where any feature older than the Fon-ho or 

 Yang-tzi' stage is recognizable. 



The Ts'in-ling stage of topographic development characterizes the sum- 

 mit views of the Ts'in-ling-shan, the mountains of the Han valley, and the 

 ranges of the middle Yang-tz'i region, where we traversed them from the 

 Wei valley to I-chang on the Yang-tzi'. It is marked by more or less decided 

 mature relief, above well-developed valley floors, in which the younger 

 canyons are cut. It presumably succeeds the Pei-t'ai peneplain, though the 

 earlier existence of the latter in this region can not be demonstrated, since 

 erosion progressed too far in the Ts'in-ling cycle. It certainly replaces the 

 tectonic relief which resulted from the Permo-Mesozoic folding. 



*Geomorphology ai the Appalachians, Hayes and Campbell, Nat. Geog. Soc. Mag., vol. vi, p. 63, 1894. 



