QUATERNARY. 187 
The depth of the Huang-t’u in the Great Plain is indeterminate. 
At a maximum it may reach a thousand feet, 300 meters, or more. ‘Toward 
the marginal mountains it gradually lessens by rise of the underlying rock 
surface, as water shoals toward a shore, and becomes so thin that hills 
protrude, and eventually the valley floors rise above the level of the plain 
of Huang-t’u. ‘This is well illustrated in the geologic maps of the vicinity 
of T’ang-hién (atlas sheets G I and F I and in Plate XXIV). Northeast 
and southwest of Si-ta-yang is a flat surface, eroded on gneiss and Ta-yang 
limestone, which we regard as an old valley floor. It is thinly covered with 
Huang-t’u, which may be the remnant of a once deeper deposit of the Hin- 
ché6u stage* or a more recent accumulation of wind-blown dust. In the 
Ning-shan basin there is a similar ancient valley floor, which is covered by 
the Huang-t’u to a depth of 25 to 4o feet, 7.5 to 12 meters, and possibly toa 
greater depth in some places. This deposit forms a terrace about 120 feet, 
36 meters, above the present channel of the Hang-ho, and appears to have 
accumulated in the old valley before the modern canyon was cut. It may 
reasonably be regarded as a deposit of the Hin-chéu stage. We did not 
observe distinctive characters which would enable us to separate it from the 
relatively recent alluvial Huang-t’u of the Great Plain, but closer inspection 
might possibly discover them. 
Along the Sha-ho across the divide into Shan-si and the Wu-t’ai moun- 
tains, the Huang-t’u formation, though not entirely wanting, is far less 
generally present than one might anticipate from accounts of its wide- 
spread occurrence in this part of China. After leaving the Ning-shan basin 
we saw nothing which could be distinguished from ordinary coarse alluvium 
until we reached the pass in the bend of the Sha-ho, 8 miles, 13 kilometers, 
northwest of Féu-p’ing. At this point there is an accumulation of yellow 
earth having the characteristic vertical cleavage, yet mingled with much 
sand and gravel, which appears to have been deposited in the channel of the 
river when it still flowed in a straight course toward Foéu-p’ing and just 
before it was diverted eastward to the canyon in which it now takes its 
circuitous course. The deposit is very limited in extent and thickness, 
and is clearly a special phase of the alluvium of the Sha-ho. 
The divide between Chi-li and Shan-si, where flat, is thinly covered 
with residual soil, but not by the Huang-t’u formation. In this respect it 
resembles the broad summits of the Wu-t’ai-shan. The valleys of the 
Ts’ing-shui-ho and the T’ai-shan-ho are floored with beds of coarse gravel 
and obstructed by large alluvial cones of shingle, gravel, and clay, the wash 
of rock and residual soil on the mountain slopes, but there is no extensive 
*The name Hin-chdéu is given to a stage of physiographic history during which the Huang-t’u first 
began to accumulate; the last epoch of the Pliocene or the earliest of the Pleistocene. 
