STRATIGRAPHY OF CHI-LI AND SHAN-SI. Ill 
thick mass of amphibolite (stratum 15), in which the large hornblende crys- 
tals form a matted network, embedded in the light grayish matrix of the 
rock. 
The sequence, as exposed in the section along the T’ai-shan-ho, is 
completed by about 1,300 feet, 400 meters, of schists and quartzites (strata 
19 and 20). At the base, following the mica-schists inapparent conformity, 
we found nearly 600 feet, 185 meters, of steel-gray quartzite. The rock is 
locally so rich in magnetite as to be almost black, and it disturbs the compass 
needle at a considerable distance from the outcrop. Banded jaspilites and 
red jasper occur in thin bands, interstratified with the quartzite. This 
member grades upward into a pink micaceous quartzite, which is usually 
massive, but sometimes schistose. Thin strata and partings of green 
schists are frequent. 
The structure of this sequence of strata is apparently that of a simple 
monocline dipping from 30° to 70° northward; but the gentler dips being 
near the southern end of thesection and the steeper ones at the northern end, 
there is a divergence of the strata upward which suggests a syncline that is 
closed and overturned southward. The southern and northern ends of the 
section are similar in that both are decidedly quartzose and contain biotite- 
schists. The black magnetite-quartzite (No. 19) may represent the ferru- 
ginous quartzite (No. 10), the iron peroxides being reduced to magnetite 
by the influence of the intrusive granite, from which we suppose the adjacent 
augen-gneiss (No. 21) to have been derived. The schists and quartzites 
(No. 20) would then correspond to the similar strata on the gently inclined 
southern limb (No. 5 to No. 9), and the lowermost members of the group, 
which are not present on the northern margin, would be cut out by the 
intrusive granite. 
Thus we may reasonably regard the Shi-tsui section as representing 
a body of sediments, partly duplicated in a synclinal fold and cut off by the 
intrusion of the granite, which now forms the augen-gneiss, that extends 
3 miles, 5 kilometers, upstream to Shang-ho-miau. 
Shang-ho-miau section (Strata 22 to 24, Plate XVIII).—In this section 
there is an alternation of marble, quartzites, and various kinds of schists, 
all of which are metamorphosed sediments. The best exposures occur near 
the temple, Shang-ho-miau, in the canyonof the T’ai-shan-ho and its western 
tributary, from 7 to 9 miles, 11 to 15 kilometers, northwest of Shi-tsui. The 
strata are steeply inclined and trend southwest in a narrow belt. 
Bordering the exposure of the augen-gneiss, on the southeast side 
of this belt, occurs a mass of garnet-staurolite-schist. This is followed by 
coarse-grained white marble, which is associated with thinner strata of 
garnet-schists. The next succeeding member consists of an alternation of 
