MIDDLE YANG-TZ'l-KIANG GORGES 607 



In the Geologic du Bassin Rouge, pp. 163, 164, 1 remarked concern- 

 ing this : 



Although the formation of I-ch'ang misses the characteristic appearance of 

 the K'ui-chou formation, we may safely presume that both are of the same geo- 

 logical age, especially as concerns the formation of I-ch'ang and the upper levels 

 of those of K'ui-chou. In the syncline of Lao-k'ui-chou we have observed 

 similar red and white more or less sandy argillites and we might imagine that 

 the coarser material was deposited in the Basin, while the finer matter was col- 

 lected on the outside. 



Finally I must still mention the occurrence of a thick conglomerate 

 bed with pebbles of a size ranging from that of a marble to that of a 

 fist and more, which is found on both sides of the river above the 

 present water level, and which point to an old river formation. It 

 therefore dates after the plication of the Red Basin, and has been 

 formed by the action of the hydrographical system, which appeared 

 after the plication. 



According to my idea Pumpelly has wrongly interpreted the sig- 

 nification of the conglomerate layer. He writes: 



Near the city of I-ch'ang, at the eastern mouth of the gorge, the limestone 

 strata, trending here NE and dipping about 80° to SE, are covered by apparently 

 conformable beds of fine-grained gray sandstone, which toward the top soon 



merges into a coarse conglomerate This conglomerate is followed by 



a red sandstone, which, above I-tu, dips easterly, and below that place westerly. ^ 



Hence Pumpelly considers this conglomerate as a level in the 

 I-ch'ang formation. 



From K'ui-chou to I-ch'ang, the Yang-tzi thus cuts through the 

 high mountain ranges, here rising to 1,200 m, which form the bound- 

 ary between the Red Basin of Ssi-ch'uan and the East China plain. 

 The structure of these mountain ranges, may appear clear from the 

 geological map and the different sketches. The deep gully, cut out 

 by the Yang-tzi in these ranges exposes a succession of the finest and 

 most interesting pictures of its inner structure. It is, as we see, a 

 succession of folds, in which faults only play a secondary part. 



The above suggests the following questions which I shall consider 

 consecutively : 



I. The tectonic signification of these folds. 



I Smithsonian Contributions to Knowledge, Vol. XV, "Geological Researches in 

 China, Mongolia, and Japan," p. 7. 



