148 RESEARCH IN CHINA. 
the Carboniferous period. There is no evidence that sediments of Silurian 
or Devonian times were deposited in any part of northeastern China which 
we saw. 
SHAN-SI SYSTEM. 
General statement.—Under the name Shan-si system we include the 
coal-bearing strata, which are so characteristic of central Shan-si, and also 
the red sandstones, which overlie the coal-measures in apparent conformity. 
Isolated patches of the coal-measures occur among the mountains 
in western Chi-li, in synclinal troughs in the Sinian limestones. In Shan-si 
we found them again in detached areas south of Wu-t’ai-hién, and widely 
distributed around ‘T’ai-yiian-fu, and thence southward to the mountains 
on the southern edge of the province. The weak shales are carved into 
lowlands or hills with gentle slopes; the sandstones form hills and plateaus 
higher than the shales and subordinate in relief to the rugged limestone 
mountains. 

A 100 FEET \\\ 
Fic. 42 (Willis) —Tién-hua, Shan-si, atlas sheet C I. Unconformity at the base of the Shan-si coal- 
measures, showing surficial deposits of Carboniferousage immediately above the Ordovician limestone. 
a=limestone agglomerate, flesh-colored; pebbles up to 20 cm., matrix crystalline limestone and green 
shale layers; no definite bedding; structure massive; an altered superficial tufa. b=layer of greenish 
shale with limestone pebbles or concretions: 2 feet, 0.6 meters, thick; c= limestone, crystalline, flesh- 
colored, indistinctly agglomeratic; d=shale, dark green, calcareous, with dark red irregular layers and 
nodules of earthy ferruginous material, formerly bog-ore; 6 feet, 2 meters, thick; e= bog-iron ore, 
dark red, irregularly placed with gray shale; f = shale, very light gray, calcareous, with pebbles. 
In the Ning-shan district, Chi-h.—In the mountains northwest of T’ang- 
hién, three small areas of the Shan-si rocks lie in the trough of a single 
large syncline, which strikes east-northeast to west-southwest. 
Only a portion of the total thickness of the coal-measures remains, 
even in the Ning-shan coal-field, which is the largest of these patches; the 
red-brown sandstone of Shan-si is entirely absent. The coal-measures 
consist of variegated shales and sandstones of various colors, the sand- 
stones being more characteristic of the upper horizons. Coal-seams are 
interbedded with the shales near the base of the formation. Igneous 
rocks were not seen. 
