WARPING IN CENTRAL CHINA. 



Ill 



From Siberia we may return to central China. 



The Ts'in-ling-shan rises from the valley of the Wei' by a steep warped 

 surface and fault-scarp, which we ascribe to the Quaternary (Fon-ho, or 

 Yang-tzi) epoch. Among the heights of the range we recognize a mature 

 surface, which we attribute to the Ts'in-ling cycle of late Tertiary time. 

 It extends beyond the Ts'in-ling range, across the Han watershed to the 

 middle Yang-tzi region, and is strongly warped. The great features to 

 which the warping gives rise are four: the Ts'in-ling-shan, the Han down- 

 warp, the Kiu-lung-shan between the Han and the Yang-tz'i, and the present 

 basin of Ssi-ch'uan. 



The Ts'in-ling-shan is a long upwarp, the eastern continuation of the 

 Kuen-lung; it attains a general elevation of 7,000 to 9,000 feet, 2,100 to 

 2,700 meters, and in the special accent, the Ta-pai-shan, rises to 12,000 feet, 

 3,600 meters. On the south it sinks to the Han downwarp, which is a broad 

 depression having summit altitudes of about 3,000 feet, 900 meters, which 

 are modified by local upwarps that probably reach 6,000 feet, 1,800 meters, 

 and by two pronounced downwarps, those of Han-chung-fu and Hing-an-fu. 

 The floors of these basins are plains of aggradation, that of Han-chung-fu 

 approximately i ,500 feet, 450 meters, that of Hing-an-fu very nearly 800 feet, 

 240 meters, above sea; but the Ts'in-ling erosion surface sinks beneath the 

 Quaternary deposit, being depressed to a still lower level. At Hing-an-fu 

 the coarse gravels, sands, and clays form bluffs along the Han. The Red 

 Basin of Ss'i-ch'uan is a downwarp like the two mentioned, except that it is 

 very much larger, and, as the remarkable delta plain of Chung-t'ing-fu 

 shows, is a region of continued subsidence and aggradation. The Kiu-lung- 

 shan is an upwarp containing summit altitudes of 8,000 to possibly 12,000 

 feet, 2,400 to 3,600 meters. It lies between the basin of Ss'i-ch'uan which is 

 on the west and the great downwarp of the lower Yang-tz'i, its warped sur- 

 face passing beneath the flood-plain at I-chang. On the north it is bounded 

 by the Han downwarp. Southward it extends across the Yang-tzi, its 

 surface declining to depressions that are not yet observed. 



The warped surface of Central China, which may thus be analyzed, 

 exhibits differences of altitude of 12,000 feet. It is, so far as we saw it and 

 we believe generally, an erosion surface which, while retaining notable relief, 

 assumed mature features by the close of the Tertiary period. It may have 

 persisted at a low elevation into Quaternary time. During the Quaternary 

 it has been warped, giving rise to the great mountain chains and extensive 

 basins that now exist. The warping characterizes the Yang-tzi epoch of 

 erosion, and the youthful aspect of the canyons of that cycle is the ground 

 for the inference that the movement did not assume notable proportions 

 until Quaternary time. 



