126 RESEARCH IN CHINA. 
the limestone contains a layer of pink quartzite about 500 feet, 150 meters, 
thick, and the same bed appears again in a ravine further west (see Fig. 22). 
This succession is in both localities cut off by an unconformity with Cam- 
brian strata, upon which the Pre-Cambrian is overturned and more or less 
overthrust. 
Section of the Tou-ts’un group.—Between Téu-ts’un and Wu-t’ai-hién 
the Tdéu-ts’un slates and portions of the overlying limestones are well 
exposed, and the structure enables us to make a fairly satisfactory although 
incomplete section (Fig. 23). 

1 MILE 

Fic. 23 (Blackwelder. Atlas sheet CI, section C C.)—Wu-t’ai-hién, Shan-si. Téu-ts’un slates beneath 
Tung-yii limestones, etc. (Algonkian), exposed in the range cast of the Wu-t’ai-hién basin. 
e. Gray and pinkish limestone, accompanied by a light-colored limestone- 
breccia in an unknown relation. 
d. Dark purplish argillite. 
c. Gray and buff limestones, dense or finely crystalline. Contain parallel 
lamine of flint, which are often curved and become prominent on the 
weathered {Stirfaces oinsi5 cis oor oss sais orecelaroteve,d, lv erstoroebete wie aaa] meme ree eee 150 feet, 45 meters. 
&. Purple argillite with thin beds of limestone and one or two of quartzite. 
The argillites show mud cracks and are not schistose............... . 250 feet, 75 meters. 
a. An unknown thickness of gray argillites which are usually slaty. Like 
the slates of Liu-yiian these frequently contain grains of hematite and 
local thin layers of red dolomite. 
The basal member of this section is the equivalent of the gray slates 
at Liu-yiian, but in neither locality did we see what underlies them. The 
gray flinty limestones are regarded as belonging to the Tung-yii and bear 
a close resemblance to those of the Ta-yang formation in Chi-li. 
Vicinity of Wu-t’ar-hien.—The phase of the Hu-t’o system which 
appears at the head of the canyon south of Wu-t’ai-hién is unfamiliar, 
but on structural data we infer that it belongs to the upper or Tung-yii 
formation. Here the lowest Sinian strata are overthrust by a pink quartz- 
itic sandstone very similar to that associated with the gray limestone 
south of Téu-ts’un (see Fig. 38). If our interpretation of the structure 
is correct, this is in turn overthrust by dark reddish limestone associated 
with dark argillites and hard gray limestones. The position of these rocks 
in the general section of the Hu-t’o system is unknown. 
Section of the Tung-yt groupb.—The low range immediately east of 
Tung-yii is composed largely of limestones with interbedded soft slates; 
the prevailing colors are dark-gray, but light-gray, pink, and even buff 
layers are frequent. The purple slates outcrop only in the northern part 
of the range, where the limestones seem to lie upon them. A short distance 
