MIDDLE YANG-TZI-KIANG GORGES 6ii 



3. In transgression for some kilometers toward the east we find 

 my green shale formation, Blackwelder's middle Paleozoic Sin-t'an 

 shale, which thins out not far to the east of Miao-ho at the lower 

 entrance of the Ox-liver gorge. To the east of the Nan-t'ou anti- 

 cline this formation does not seem to occur either. 



4. To the Sin-t'an shale succeeds my gorges-limestone formation, 

 Blackwelder's Upper Carboniferous Wu-shan limestone. 



Now we see the remarkable fact that the Nan-t'ou area, which 

 proved to be an eastern land-ridge for the older formation, becomes a 

 sea, together with the eastern part, during the Upper Carboniferous 

 period. This sea very probably in transgression spread over a great 

 part of China. After the limestone formation the area of Nan-t'ou 

 again resumes its role of boundary wall between an eastern and a 

 western basin. 



5. The (probably) Permian and Lower Triassic reddish-brown 

 formation only occurs in an eastern part of the Red Basin, not in its 

 center. It extends along the Yang-tzi as far downstream as Yeh- 

 t'an, but not as far as Hsiang-chi. 



6. The (probably) Upper Triassic slaty limestone formation extends 

 even less far toward the east. It thins out already above Yeh-t'an. 

 Neither of these formations occur to the east of the Nan-t'ou anticline. 



7. Overlying this transgrades the Rhetian sandstone formation 

 in the Red Basin itself far to the west. Although the area of Nan-t'ou 

 is again a land limit against which the sandstone formation thins out, 

 this same Rhetian sandstone, which contains coal measures, occurs 

 in the East China Basin and also in other parts of China. We already 

 noticed before that the formation itself extends farther east than the 

 coal layers, which occur in higher levels. 



8. This retrogression of the sediments westward is continued, and 

 we find the shell-marl strata of probably Cretaceous age only in the 

 middle of the Red Basin, whilst it thins out in more or less extensive 

 lenticular layers between Wan-hien and K'ui-chou-fu. 



9. After this again comes a period of transgression. The K'ui- 

 chou formation extends to the western limb of the Nan-t'ou anticline. 

 It seems that this anticline did not act as dividing line for the upper 

 levels of this formation, for we find the I-ch'ang formation over- 

 lying its eastern limb, as far as it has not been washed away by ero- 



