STRATIGRAPHY OF CHI-LI AND SHAN-SI. 151 
TERTIARY. 
NING-SHAN FORMATION, 
Except for the Huang-t’u and river gravels, rocks later than the 
Shan-si series came to our notice in only one locality in the north Chi-li- 
Shan-si region, at Ning-shan, Chi-li. Northwest of the town, bordering 
the northern mountain range, is a group of low hills of rounded outlines. 
Their gravel-strewn slopes disclose beds of coarse conglomerate inclined 
gently away from the mountains. Cross-bedding is prevalent within the 
NW SE 

eae a 


yy “ | 
Se Yi 
SS ee HY Ny Wy} 
a iy LT i) iy 
== = UMM, 
oO 
° { 2MILES 
Fic. 46.—Yau-t’o district, Shan-si, atlas sheets C I and C II, section KK. Sinian forma- 
tion lying unconformably upon Algonkian metamorphic rocks and preserving a synclinal 
remnant of the Shan-si series. 
mass, as is evident where the material is not so coarse as to render the 
stratification obscure. The constituents of this rock are mostly masses 
of Sinian limestone, with cherts and a chert-breccia, which resembles that 
described from the base of the Sinian, near Nan-t’ang-mei. The pebbles, 
which average several centimeters in diameter and attain a maximum of 
over 63 centimeters, are fairly well rounded. Except where locally indu- 
rated into quartzitic layers, the rock is but weakly consolidated and 
weathers rather rapidly; it is harder, 
however, than the coal-bearing strata, 
and thus remains as hills while they 
waste away. 
re The relation of these gravels to 
Fic. 47 (Blackwelder).—Ning-shan, Chi-li. Ning- i : é wy = 
shan gravels (Tertiary) lying upon tilted the Shan-si series is plainly visible in 
and eroded Shan-si series (Carboniferous). q bluff bordering the main road, 2 
ee miles, 3.5 kilometers, north of Ning- 
shan (Fig. 47). There the yellow and red shales and white sandstone are 
seen tilted southward at an angle of 30°, but are truncated above by an 
approximately horizontal, though uneven, surface. Upon this old plain 
rest heavy beds of the conglomerate, with nearly horizontal stratification. 
The age of the Ning-shan formation has not been determined pre- 
cisely. Inasmuch as the conglomerate is separated by a considerable 
unconformity from the coal-measures, it is safe to say that it is Post- 
Carboniferous. ‘The section which reveals the unconformity also shows 
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