STRATIGRAPHY OF CHI-LI AND SHAN-SI. 115 
Western section of the Wu-t’ai-shan.—The Wu-t’ai range was crossed by 
Willis in a rapid reconnaissance, between Tai-chéu and Tung-yti, 20 miles, 
32 kilometers, southwest of the above-described T’ai-shan-ho section. The 
northwestern foothills consist of granitoid gneiss, part of the extensive 
exposure of the basal complex north of the range. Three and one-half 
miles, 5.5 kilometers, up a canyon from its mouth, mica- and quartzite- 
schist come in with a vertical dip. The character of the contact with the 
granite was not observed, but is supposed to be that of deposition. The 
schists continue for 5 miles, 8 kilometers, to the summit of the range, which 
is composed of the prevailing chlorite-schist, that in this locality includes 
the horizon of conglomerate of large quartz and quartzite pebbles. The 
dip varies from 30° to 90° toward the northwest. Descending the southern 
slope, the conglomerate schist is found to extend across the valley into the 
separate range on the south. It is probably repeated by thrusts and folds. 
In the northern part of this section, between the granitoid gneiss and the 
summit of the range, the Wu-t’ai schists are folded in a closed and complex 
syncline. The occurrence of the schist-conglomerate is probably anticlinal 
in the main divide, and is very possibly overthrust toward the south upon 
a synclinal mass. Further southeast are heights of quartzite with nearly 
vertical dip. They were seen only from a distance, from the aggraded 
valley on the route to Tung-yti, but are supposed to represent the upper 
members of the Wu-t’ai system. They are in turn succeeded southeast- 
ward by strata of argillite, quartzite, and limestone, lying in more open 
folds, and these are, with confidence, assigned to the Hu-t’o system. 
In this section none of the distinctive strata of the Shi-tsui or Nan-t’ai 
sections were seen. ‘The siliceous strata are not more prominent than those 
at the base of the Si-t’ai, and the great body of chlorite-schists corresponds 
with the main part of that section. Conglomerates of quartz and quartz- 
ite pebbles up to 20 centimeters in diameter are very characteristic strata 
which make the identification complete. The absence of the Shi-tsui and 
Nan-t’ai rocks, which we regard as older and which should appear at the 
base between the Si-t’ai schists and the T’ai-shan complex, may be explained 
by overlap of the Si-t’ai or by overthrust of the T’ai-shan. The contact 
was indeterminate where seen. 
Observations southeast of Yau-t’du (atlas sheet C I).—The Wu-t’ai 
schists appear to extend along the southeast side of the T’ai-shan-ho valley 
for many miles, for they were found again in a valley which joins that 
river 2.5 miles, 4 kilometers, south of the Yau-t’6u coal district. The 
rocks there exposed consist of dark purplish biotite-schists, associated with 
thick masses of white quartzite and greenstone dikes. The float which is 
brought down the valley from the south contains fragments of granite and 
