PHYSIOGRAPHY OF NORTHWESTERN CHINA. 217) 
younger Pre-Cambrian rocks, extend southwestward in an anticline, and 
that the syncline of Sinian strata which forms the Ki-chéu-shan, and which 
ends southwest of the T’ai-shan-ho, is limited to a width of 15 or 20 miles, 
25 or 30 kilometers, northwest to southeast. 
The valley of the Hu-t’o-ho northeast of the Hin-chéu basin lies 
between the Wu-t’ai-shan and the range which forms the outer border of 
the high plateaus of Mongolia. Our topographic surveys did not extend 
up the river beyond Hin-chéu, but I took some notes in a rapid trip to 
Tai-chéu and across the Wu-t’ai-shan to Tung-yii, of which I quote the 
following: 
At Hin-k’ou a ridge of quartzite extends across the valley from east to west and 
reduces it to a narrow water-gap. The quartzite is dark red, much jointed, and cut by 
basic green dikes. It belongs to the lower part or at the base of the Hu-t’o system, and 
may be seen dipping gently 10° to 30° toward the northwest. Oppusite Yuan-p’ing are 
craggy hills, consisting principally of gneisses of the T’ai-shan complex, and on their eastern 
slope are strata of the Hu-t’o system dipping southeast 30° to 40°. Thus the southwestern 
end of the Wu-t’ai-shan appears to be sculptured from a syncline in rocks of the Hu-t’o 
system, and the gneiss comes up from under them on the northwest. 
Between Yiian-p’ing and Kwo-hién we passed several caravans carrying coal from 
points on the Yang-wu-ho, and the escort reported mining at five or six places on the 
road to Ning-wu-fu, at intervals of about ro li, or 3 miles, apart, the nearest being 15 
or 20 miles from Yiian-p’ing. 
The mountains northwest from Kwo-hién exhibit a deeply eroded front, locally 
precipitous toward the top and sending out spurs into the plain below. Alluvial fans 
are confluent and extensive along the base of the range, rising approximately 1,000 feet 
above the plain, or one-fourth of the total height of the mountains. The outcropping 
cliffs present faces of limestone, probably Sinian, dipping apparently gently northwest. 
The structure of the range appears, however, to include folds or faults, which influence 
the elevation of these outcrops and suggest that the plateau is not one of simple flat strata. 
The valley is wide and flat, the river flowing through a flood-plain which is aggraded with 
gravel, sand, and loess. The effects of transportation by water are obvious in the wide 
distribution of the gravels, and the influence of the wind in sorting and distributing the 
finer materials is apparent in the sweeping clouds of dust and in extensive areas of dunes. 
We left the Hin-chéu basin by the main highway across the Shi-ling, 
and went up the deeply sunken wagon track over the surface of the 
Huang-t’u. In order to avoid clouds of dust in the canyon of the road- 
way, and gain a freer outlook, we took the footpath which follows the 
brink of the road, often 100 feet above it. On both sides stretched the 
smooth, even surface of the loess, which, being quite steeply inclined, is 
cut by many deep, parallel canyons. As we approached the summit we 
found the bed-rock of Sinian limestone outcropping in limited exposures. 
There is a long flat at the top of the pass and then a gradual descent to 
the basin of Huang-t’u-chai, a wide level scarcely a hundred feet lower, 
which overlooks the tributary of the Fén-ho. The level is composed of the 
