MIDDLE YANG-TZi-KIANG GORGES 589 



7. The slaty limestone formation, 300 to 400 m. 



8. The sandstone formation, with layers of coal, whose flora 

 belongs to the Rhetian, 600 m. 



9. A formation, 1,800 to 2,500 m., of alternating strata of sand- 

 stone and argillite, the former of which are generally of eolian origin. 

 This has been named by me the K'ui-chdu formation. 



Between 8 and 9 there is, in the middle of the Red Basin, a series 

 of marls, 50 m. thick, but this is lacking in the bordering part. 



The formations 7 and 8 I believe I may count as belonging to the 

 Permian or to the Lower Triassic, and to the Upper Triassic. 



The stratum between 8 and 9 seems to belong to the chalk forma- 

 tion, so that the K'ui-chdu formation, in which I did not find any 

 organic remains, may be considered as belonging to the chalk forma- 

 tion, and, taking into account the thickness of the formation, it 

 might be assumed that the deposit continued into the Tertiary Period. 



The folds of the Red Basin of Ssi-ch'uan are of later date than the 

 K'ui-chdu formation. As latest formation must be named the 

 following : 



10. A conglomerate bank, which I have encountered in several 

 parts along the Yang-tzi-kiang. The bowlders and pebbles in this 

 conglomerate generally are of eruptive origin whereas the cement 

 consists of a calcareous siliceous tufa. This must therefore be the 

 latest formation, whose origin dates after the folding of the Red Basin. 



We will now describe the structural geology of the Middle Yang- 

 tzi-kiang gorges going downstream from K'ui-chdu to I-ch'ang. 

 Coming from the synchnal area, west of K'ui-chdu-fu, the Yang-tzi- 

 for the first time encounters the high gorges-limestone mountain 

 ranges, to the east of that place. On the left bank the river tries to 

 penetrate the softer upper strata so that a creek is formed there. But 

 as the softer layers, which formerly spread out like a mantle over 

 the anticlinal gorges-limestone mountain range, and nowadays have 

 been washed away from the crests of this range, still, as a whole, form 

 a kind of dam, the Yang-tzi is forced to make a bend toward the first 

 of the great gorges: the Fong-hiang-hia or gorge of K'ui-chdu-fu. 

 This gorge being a deep incision of the big river through the mountain 

 range east of K'ui-chdu-fu, clearly shows its structure. 



The gorges-limestone strata strike about ENE-WSW and dip 



