MIDDLE YANG-TZi-KIANG GORGES 603 



overlying limestone formation, rising to mountain-heights, in which 

 is cut the Niu-kan-ma-fei-hia. 



In this gorge the dip of the layers soon again becomes W, and so, 

 going down-stream, we find ever deeper levels, until, immediately 

 after the end of the gorge near Miao-ho, the green shales reappear, 

 but now in very much thinner beds. 



This shale formation {Sin-fan shale) thins out, in the western 

 limb of the anticline of Nan-f ou, from west to east. 



The Ki-sin-ling limestone, which was exposed by the fold of Lung- 

 tchoe, in the Sin-fan area, does not again show itself east of the Niu- 

 kan-ma-fei-hia . 



As Blackwelder and Willis have observed in the upper course of 

 the Ta-ning-ho the Sin-t'an shale to be in conformity with the Ki-sin- 

 ling limestone, so that this limestone formation appears to extend as 

 far as Sin-t'an, the thinning out of both formations toward the east 

 would increase the signification of age of the anticline of Nan-t'ou. 

 More about this later. 



About the geoglogical structure of the Niu-kan-ma-fei-hia or Lu- 

 kan gorge and the Mi-t'an gorge Willis again gives a description 

 greatly differing from my own. He writes:^ 



The Lu-kan gorge is a canyon across the Ki-sin-ling Hmestone, which dips 

 NW. Above Sin-t'an the overlying middle Paleozoic shale, which we have 

 named from its occurrence at this point, is succeeded by the Wu-shan limestone, 

 dipping 40° NW and giving rise to the Mi-t'an gorge. 



I presume that while going so swiftly downstream the fold of 

 Lung-tchoe was overlooked, and so the whole structure was wrongly 

 interpreted. According to Willis, a deep valley would have to occur 

 between the two limestone formations. The photo on p. 43 of my 

 Geologie du Bassin Rouge shows instead of a valley a high mountain 

 range of gorges-limestone. 



At the lower end of the Lu-kan gorge the trend of the layers is 

 NNW-SSE. Underlying the but slightly developed green shale 

 formation appear the crystaUine schists, which trend NS and dip 

 20° W\ They consist of mica, chlorite, and hornblende schists, alter- 

 nating with nearly pure quartz beds and intersected by dykes of 

 melaphyre. Near the lower opening of the Lu-kan gorge (Niu-kan- 



I Research in China, Vol. II, Part i, p. 286. 



