STRATIGRAPHY OF CHI-LI AND SHAN-SI. 137 
of dark argillites and siliceous red limestones, inclined at high angles 
and cut by greenstone dikes. The Cambrian, resting upon the truncated 
stumps of these strata, dips gently southward (Fig. 33). At the base of 
the Sinian there is a dark red conglomerate with sandy matrix. The fact 
that this varies in thickness from nothing to 20 feet, 6 meters, or more indi- 
cates that the Pre-Cambrian topography in this region possessed slightly 
more noteworthy relief than in other localities examined. The conglom- 
erate contains quartzites, and also purplish argillites and limestones like 
those beneath it. This contact, which is to be seen about 4 miles, 6.5 
kilometers, to the south of Tung-yti, is exposed with exceptional clearness. 
The fifth example is from the base of the Ki-chéu-shan, not far from 
the contact shown in Fig. 31, but the Pre-Cambrian is represented by the 
greenish argillites, probably of the Hu-t’o system, which are cut by a 
basal dike that ends at the unconformity (Fig. 32). 
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Fic, 31 (Blackwelder. Han-yang, Shan-si, atlas sheet B II).—Unconformable contact of Cambrian 
shales upon Pre-Cambrian granite, beneath an overthrust mass of the latter. Foothills of Ki-chéu- 
shan southeast of Han-yang. 
From these examples it appears that, before the Sinian sediments were 
laid down, the older rocks had been folded and eroded until all three of 
the Pre-Cambrian systems had been exposed in various areas. 
SINIAN SYSTEM. 
General statement.—The Sinian rocks were found in three localities 
in the mountains between Pau-ting-fu and T’ai-yiian-fu: (1) near Ning- 
shan in Chi-li, (2) along the southern edge of the Wu-t’ai-shan district, 
and (3) on the northern flank of the Wu-t’ai range. As it is developed in 
those areas, the system consists of only two distinct formations; a basal 
group of reddish shales, sandstone, and impure limestone, and a thick series 
of grayish limestone, which, while presenting some internal variations, is 
fairly uniform and can not readily be subdivided. 
For the first of these we propose to extend from Shan-tung the name 
‘‘Man-t’o formation,’’ because the red shales of the two provinces are 
