90 RESEARCH IN CHINA. 
intricate forms. In composition they are usually earthy and are often 
rich in feldspars. Although prevailingly soft and friable, the rock is locally 
cemented into a quartzitic arkose. The sandstone varies in the one direc- 
tion to shaly sandstone and even to thin local shales, and on the other 
hand it grades into conglomeratic sandstone and typical conglomerate. 
Of these two extreme phases the conglomerate is much the more prominent. 
The pebbles consist almost entirely of quartz and chert of various colors, 
with occasional fragments of granite. In size the fragments rarely exceed 
the diameter of 6 or 7 centimeters and are usually much smaller. All 
of these sandy rocks are prevailingly red or maroon in color, with variations 
toward dull brown and yellowish tints. Numerous dikes of igneous rocks, 
which are described in later pages, have been intruded through the sand- 
stone at various points. 
Throughout most of this area the bedding of the sandstone is nearly 
horizontal. On account of the cross-bedding, observations of the dip 
must be made with care and discrimination; but where the major strati- 
fication planes are apparent the dip is seen to be undulatory, varying from 
maxima of 30° northeast and 25° southwest. On the extreme southern 
border of the exposure the rocks dip to the northeast, while in the last 
outcrops visible on the northern edge the strata dip gently southward. 
The general structure, therefore, is that of a flat synclinorium. 
On the north side, the Yung-ning sandstone, as exposed, is separated 
from the metamorphic rocks north of it by massive porphyry intrusions 
and a flat sandy valley; the relations, therefore, could not be observed 
directly. The conglomeratic quartzite of Li-kuan-ts’un seems to belong 
more appropriately with the white crystalline limestone and schists upon 
which it appears to lie, than with the Yung-ning formation. It not only 
lacks the red color of the sandstones, but it is much more thoroughly con- 
solidated than they are. As already stated, von Richthofen crossed this 
range after nightfall and therefore could not see the geologic features of 
the hills. His inference that the rocks belonged to the Yung-ning forma- 
tion, which appears south of Li-kuan-ts’un, is probably erroneous. 
On the southern border of the exposure of the Yung-ning sandstone 
the lowest member of that formation, to a thickness of about 50 feet, con- 
sists of coarse conglomerate. The pebbles average nearly as large as hen’s 
eggs, scattered individuals having a diameter of as much as 4 inches. As 
in the conglomerates in the higher horizons in the sandstones, these pebbles 
are composed of quartz, quartzite, and chert. The matrix is quartzite 
and is so rich in ferric oxides that it presents a deep reddish-brown color, 
like the rest of the sandstone. Toward the base of the member the pebbles 
become larger and more closely crowded—a common characteristic of 
basal conglomerates. This conglomerate, which, by virtue of its superior 
