326 J. 8S. Lee—An Outline of Chinese Geology. 
c. Sitai Series. A thick series of monotonous, fine-grained chlorite- 
schists grading downwards into a basal conglomerate, which 
latter contains such pebbles “‘as the underlying Nantai Series 
would furnish’. _ 
b. Nantai Series. Largely consists of dark quartzite and siliceous marble 
with a subordinate amount of schist; the total thickness is 
probably less than 2,000 feet. 
a, Shitsui Series. Stratified schists, gneiss, and schistose quartzite 
predominate in this series. The apparent thickness is estimated 
at 12,000 feet; but the real thickness may not be more than 
6,500 feet. 
According to Willis and Blackwelder, the Huto System is exposed 
in the Tou-tsun, Liu-yuan, Tung-yu districts, near the Wutai-shan, 
and in the northern slope of the Ki-chou-shan (about long. 113° E., 
lat. 38° 30’ N.). It consists of two series :— 
Upper. Tung-yu Limestone. Limestones with subordinate slates; the 
former sometimes contain beds of quartzite, and sometimes layers of 
flints ; total thickness 3,500—5,000 feet. 
Lower. Tou-tsun Slate. Grey phyllite or slate with occasional thin 
layers of limestone or dolomite ; total thickness 3,000 feet or more. 
In the same area the above-mentioned authors distinguish a third 
formation of limestone, the Ta-yang Limestone, containing 
numerous characteristic layers of flints and occasional beds of 
quartzite. With good reason they assign the Ta-yang Limestone to 
the Nankou (Huto) System. From lithological similarity and from 
the parallelism of stratigraphical sequence, Willis correlates the 
Ta-yang Limestone and other Huto rocks with the series of flinty 
limestone of Nankou, north-western Chi-li, and of the Hwei-lu 
district, south-western Chi-li, that underlies the fossiliferous 
Cambrian. He therefore proposes to replace the term Huto System 
by the term Nankou System when the equivalency of the two is 
eventually established. 
Although rocks of approximate Algonkian age in Chi-li and north- 
eastern Shan-si permit of a twofold grouping the application of this 
classification outside this area is problematical. Pending further 
research, a collective name would be useful for denoting those rocks 
found in all parts of China that are equivalent to a part or the whole 
of the Wutai and the Nankou (Huto) Systems. For this purpose 
we may conveniently use a united term, the Wutai-Nankou Systems. 
The Wutai-Nankou Systems thus defined would include, in 
addition to the rocks so far mentioned, the chlorite-schist, biotite- 
schist, crystalline limestone, slates, quartzite, and other highly 
altered sedimentary strata in the eastern and middle Tsing-ling 
Range; a part of the highly metamorphosed strata in the north- 
western Nan-shan Ranges, namely, on the southern side of the 
Tolai-shan, in the Da-ssue-shan, the Ritter Mountain, and the 
Muschketov Range; the ‘‘ pre-Cambrain”’ quartzite and quartzose 
phyllite with green grits exposed between Kwei-lin and 
the Si-kiang, in the province of Kwei-chou, and other “ pre- 
Cambrain”’ rocks that occur to the west of Kien-kiang, in the 
