6o2 



E. C. ABENDANON 



lintestoire. 



I-ch'ang gorges. In the Mi-t'an gorge we see before us a west-dip- 

 ping limb of the gorges-hmestone formation, beneath which appears 

 the green shale formation, "Blackwelder and Wilhs' Sin-t'an shale." 

 Between the Mi-t'an and Niu-kan-ma-fei or Ox-liver gorges, we 

 find the Sin-t'an area. In about the middle of this area, which is 

 bordered in the W, S, and E by the high gorges-hmestone mountains, 

 occurs the low and sharp fold of Lung-tchoe of which a photo appears 

 on p. 43 of my publication on the Red Basin. This fold which has a 

 45° W-dipping and a io° E-dipping limb, itself dips steeply south 

 (see Fig. 8) . It exposes a reddish-brown limestone, in which I found 

 lower Silurian nautih, and many fine and very large Orthoceratite 

 casts. I therefore beheve that this must be the same hmestone as the 



Ki-sin-ling limestone of 

 Blackwelder and Willis. 

 On this limestone rests 

 the green shale forma- 

 tion (Sin-t'an-shale) and 

 above that the gorges- 

 limestone formation. 

 All this as far as the 

 right bank is concerned. 

 On the left bank, on the contrary, the Ki-sin-ling limestone 

 rises to much higher levels, and we find under the reddish-brown 

 limestone a crystalhne dark blue one, in layers, that are often separated 

 by several centimeters, as a result of the plication. The closing of the 

 narrow Sin-t'an basin by the gorges-limestone formation was not 

 observed by me toward the north, looking from the right bank. We 

 must still mention that, on the north bank, occurs, on top of the hori- 

 zontally cut off and W-dipping Sin-t'an shales a thick conglomerate 

 bed with large rounded-off pebbles, which must be originally from 

 the valley in the north. This bed is of a recent date and was formed 

 after the plication of the Red Basin, and while the Yang-tzi was cut- 

 ting its way deeper and deeper into the mountains. In the eastern 

 hmb of the fold of Lung-tchoe the green Sin-t'an shale formation con- 

 tains more hard quartzy sandstone beds than in the western hmb. 

 The formation also diminishes in thickness in that direction. The 

 inchne of the layers decreases and the Yang-tzi again enters the 



Fig. 8 



