IO6 RESEARCH IN CHINA. 



The eastern margin of this downwarp lies in the Yellow Sea, possibly 

 between the point of Korea and Shanghai. The mountains of southeastern 

 China may be said to limit it on the southeast. The Yang-tz'i defines it 

 northeast from the Tung-ting lake. The hills of An-hui and Hu-pe'i appear 

 to be within its area. 



The western margin of the downwarp is the slope of the mountains, 

 comprising the Khingan range in the north, the so-called plateau of Shan-si 

 in a mid-stretch, and the mountains of eastern Hu-pe'i further south. Von 

 Richthofen described the limit between the plain and the mountains as a 

 fault, which appears on his map, Versuch einer Tektonischen Karte des 

 nordlichen Chinas, as the Khingan Linie.* He does not cite any evidence 

 of faulting on the line itself, it being drawn indeed in the plain of alluvium ; 

 and according to our observations on three different sections the passage 

 from the plain to the mountains is a zone of warping, not a line of disloca- 

 tion. Where, in latitude 49, the Siberian railroad descends to the Sungari, 

 the eastern slope of the Khingan is a tilted, dissected, but unbroken pene- 

 plain. Where the Sha-ho, in latitude 39, has cut its autogenous valley, 

 and the hills about T'ang-hien lie half-buried in the plain, the effects of 

 modern warping are obvious. Normal faulting, though present in the 

 Ning-shan basin, occurred at a remote Tertiary date, and erosion has 

 reversed the relief to which it gave rise. Again, in latitude 31, where the 

 Yang-tz'i emerges from its profound gorges at I-chang, the mountain slope 

 that faces the far-spreading river plain is a tilted surface of erosion, showing 

 a continuous stratum of Carboniferous limestone, which toward the base is 

 overlain by the K'ui-chou red beds in appropriate stratigraphic sequence. 

 It is a warped surface, not a fault; and there is no evidence that it is limited 

 by a fault at the base. 



This zone of warping was crossed by von Richthofen along two routes 

 of travel in Shan-si; the one in latitude 33, northwest of "Hwai-king-fu;" 

 the other in latitude 38, on the great road from T'ai-yiian-fu to the eastern 

 plain. In the former traverse he ascended to the plateau over a mono- 

 clinal flexure on an erosion surface that is sculptured on Carboniferous 

 shales and Sinian limestones! an d that forms spurs between deep gulches. 

 The steep slopes of the spurs end in a line and thus simulate a fault-scarp, 

 but the structure is that of a simple flexure and is so described by the trav- 

 eler. At the more northerly crossing von Richthofen observed step-faulting 

 which he describes as follows :$ 



After having observed the structure of the mountains in southern Shan-si, it was 

 for me a matter of no slight interest to see in what manner the horizontal strata of the 

 plateau might break away or sink toward the Great Plain. As we have seen, the plateau 



*China, vol. II. f Ibid., vol. n, p. 407. I Ibid., vol. H, pp. 440-442. 



