CHAPTER IX. 
OBSERVATIONS IN CENTRAL SHAN-SI. 
STRATIGRAPHY. 
By Eliot BLACKWELDER. 
INTRODUCTION. 
The formations which we found along our route of travel through 
Shan-si to Shen-si are essentially the same as those described in the pre- 
ceding account of the district north of T’ai-yiian-fu. The Pre-Cambrian 
rocks represented belong to two and possibly to three systems. They are 
followed by the Sinian and Shan-si systems of the Paleozoic, and over all 
is distributed the Huang-t’u formation. As it was not practicable to 
make detailed observations in the course of this rapid journey, the con- 
struction of a continuous section is not attempted. 
THE PRE-CAMBRIAN. 
Pre-Cambrian rocks occur in almost all of the higher mountains visible 
from the imperial highway. The existence of a somewhat extensive 
exposure to the west of T’ai-ytian-fu is indicated by the composition of 
the gravel, which is brought down to the plain by the W6n-shui-ho. In 
addition to the reddish sandstones and Sinian limestones which occur in 
the hills bordering the plain, this material comprises black-and-white 
hornblende-granite, coarse pink granite, hornblende-porphyry, basaltic 
rocks, and quartzites of various colors. These rocks are presumed to come 
from a rugged range of mountains, which is visible from the mouth of the 
Won-shui valley and appears to be 12 to 15 miles, 19 to 24 kilometers, 
distant toward the north. The rocks indicate the occurrence of the T’ai- 
shan complex and one or more of the Pre-Cambrian sedimentary series. 
About 5 miles, 8 kilometers, west of W6n-shui-hién, the monoclinal 
fold, which raises the entire Sinian system up from under the prevailing 
coal-measures, exposes beneath the Cambrian a system of rocks, which 
develops irregular hills of rounded contour. As seen from a distance, 
these hills are dark in color in contrast with the light buff tinge which is 
characteristic of exposures of the basal complex. ‘Topography and color 
suggest the dark limestones and slates of the Hu-t’o system, but Obrut- 
schov, who passed nearer the hills, mentions only gneiss and granite as 
lying beneath the Cambrian. 
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