82 RESEARCH IN CHINA. 



the deposits he had seen previously were in strata conformable to his 

 Kohlenkalk (Sinian). Those were, however, of Carboniferous age, whereas 

 these may probably be of Lower Jurassic, according to plants collected by 

 Lorenz and described by Potonie. 



Throughout northwestern China, from the eastern outcrops of the Car- 

 boniferous coal-measures west of Peking and the western margin of the great 

 plains, the area of red and yellow sandstones overlying the coal-measures is 

 very extensive. Von Richthofen called these strata " Ueberkohlensand- 

 steine " or " Plateauschichten, " on account of their relation to the coal- 

 measures, their indeterminate age, and their occurrence in the extensive 

 synclinoria which form the elevated districts of Shan-si. He gives but 

 one section,* in which he distinguishes from below upward the following 

 members : 



(1) Sandstone and shale of the coal-measures with several small coal-beds. 



(2) The principal anthracite bed which is accompanied by black slates. 



(3) A series of mostly dark shales and soft yellow sandstones. 



(4) Reddish yellow clayey shales with occasional thin sandstone layers. 



(5) Green and red shales, which are very thin-bedded and hard and break up into 

 fine debris. These are interbedded with some thin sandstones which form benches. 



(6) Soft and also hard sandstones, heavily bedded ; 100 feet thick. 



(7) Bright-colored shales like those in 5, which also alternate with a few sandstone 

 beds. The principal colors are green, gray, blue, and red ; thickness, 1 20 feet. 



(8) Firm sandstones of a greenish color, very evenly bedded with white mica ; in part 

 containing quartz grains as large as peas, which also occur of still larger size and form 

 solid conglomerates. 



(9) Shales and sandstones of dominantly red color. 



The last member is probably not the top of the series, the total thick - 

 of which is estimated at 3,000 feet, whereas that of the underlying 

 -measures (which are included in the preceding section) is said to vary 



from 400 to 600 feet.f 



At Ta-tung-fu, northern Shan-si, f is a sequence of strata which is 



peculiar not only in being remote from other similar basins, but in the 



great thickness of strata and of the individual coal-beds. Von Richthofen 



describes it as follows: 



Lower Jura; coarse quartzose sandstones with clayey matrix, interbedded with white 

 strata of tripoli and also of siliceous calcareous formation, both containing remains of plant 

 stems; also coal-beds, which are associated with black shales. The visible thickness is 

 1,200 feet. The character and color of the strata vary continually. The strike is north 

 30 east, the dip is in a direction north 60 west, at first at an angle of 40, which lessens 

 to 10, and the upper beds lie almost flat. 



*China, Tol. n, pp. 414-415. 



^Ibid., page 453. 



%Ibid., vol. n, pp. 356-359- 



