6o6 E. C. ABENDANON 



In the Mi-t'an gorge we saw that this level of the gorges-limestone 

 formation was steeply inclined, and on both sides of the river had 

 been excavated into deeply grooved cross valleys. In the eastern 

 limb of the Nan-t'ou anticline which has a much fainter dip, the river 

 has completely altered its course, where it reached this softer level in 

 the hard hmestone formation. Afterward it again bends round to 

 an ESE course, and cuts through ever-higher levels of the gorges- 

 limestone formation, until, at the end of the I-ch'ang gorge, it makes 

 a sharp curve to the south. In this latter part of the gorge occur 

 many minor plications in the layers which, as a whole, continue to 

 dip io° SE. The limestone strata, gently sloping away, disappear 

 under the I-ch'ang series. 



Although I did not perceive it, Willis again assumed the existence 

 of the Sin-t'an shale and the Ki-sin-ling limestone in the I-ch'ang 

 gorge. He writes : 



The lowest or I-ch'ang gorge of the Yang-tzi is cut across the Wu-shan 

 limestone which rises at the rate of about i,ooo feet a mile till the Sin-t'an (middle 

 Paleozoic) shale appears from beneath it. Further upstream the Ki-sin-ling 

 (Cambro-Ordovician) limestone forms a second gorge, and passing from a dip 

 of io° to a nearly horizontal position, gives rise to the mesa like heights above 

 Huang-ling -miau . ^ 



But the deep erosive valleys in the Sin-t'an shale altogether fail to 

 prove that the above quoted view of the structure of the I-ch'ang gorge 

 is correct. The photo published by me on p. 25 of my Geologic du 

 Bassin Rouge shows high rising cliffs of limestone on the left side of 

 the Yang-tzi, where, according to Willis, a deep erosive valley of 

 Sin-t'an shale ought to exist. My photos on p. 28 sufficiently prove 

 that Willis' idea, that the Ki-sin-ling limestone borders the right side 

 of the Yang-tzi from Nan-t'ou till Huang-ling-miau, is not in accord- 

 ance with the reality. 



Below the I-ch'ang gorge the Yang-tzi enters upon its lower 

 course, and, to far below I-tu, it cuts across a formation of sandstone 

 and red argillite layers, which between I-ch'ang and I-tu are folded 

 into a broad and flat antichne. 



Blackwelder calls this "apparently a recurrence of the K'ui-ch6u 

 formation."^ 



I Research in China, Vol. I, p. 286. 

 a Op. cit., p. 287. 



