290 RESEARCH IN CHINA. 
of the Wu-shan limestone, but the underlying Sin-t’an (Middle Paleozoic) 
shale. Nine-tenths of the section is, however, in the Wu-shan limestone, 
ranging at the river level from the base of the formation to the top. 
Just north of San-shi-li-p’u the K’ui-chéu red beds are involved in 
a small anticline and syncline, and then rise upon the first great anticline 
of the Wu-shan. The arch rises sufficiently to expose about one-half of 
the Wu-shan, and near its center the limestone strata are crumpled on 
the concave side of the curve. An open syncline of very minor propor- 
tions connects this arch with the next one to the north, which is also a 
relatively small feature. We then come to the great arch which brings 
up the base of the Carboniferous limestone, as shown in the photograph on 
the Wu-shan-hién sheet, d 6 of the altas, and which contains an overthrust 
from the north, within the Wu-shan formation. The fact of this over- 
thrust was observed, but its relations to the fold in the higher cliffs could 
not be, and neither could those below the river level. It follows, there- 
fore, that the internal structure which is delineated on the section is, to 
a certain extent, hypothetical. The displacement on the fault is probably 
small, and the dislocation would perhaps not be seen in anything but a 
deep canyon section. The view of the party surveying in the canyon was 
taken near the center of this arch (atlas sheet d 7). 
At Ta-ning-hién and for several miles north of that point, the Wu-shan 
limestone is exposed in the canyon walls in long sweeping curves of strata. 
The river is sunk below the top of the limestone at Ta-ning-hién, and the 
K’ui-chou red beds do not occur at that town. We do not know whether 
they appear in the syncline toward the east or the west, but as the streams 
which here enter the river are small, it is probable that the basin is of 
limited extent. Were it otherwise, the town would probably lie upon one 
of the through routes following a valley, which in that case would be 
developed on the syncline. Two miles north of Ta-ning-hién we saw the 
limestone somewhat contorted in the axis of the sharp syncline, and the 
strata north of that point were vertical. The underlying Sin-t’an shales 
here come to the surface for the first time northwest of the Wu-shan arch, 
a distance of perhaps 35 miles, 55 kilometers. The fold is a compressed 
anticline about 3,000 feet, 900 meters, across in the shale, with nearly 
parallel limbs. Its height could only be inferred. Northward beyond it 
is a sequence of close folds in the Wu-shan, extending 2.5 miles, 4 kilometers, 
and comprising two synclines and an anticline. The southern of the two 
synclines is faulted in the center, and in the northern the strata are very 
sharply folded together. The whole constitutes a sort of double keel of 
Wu-shan limestone, which here sinks the black chert horizon perhaps 
8,000 or 10,000 feet, 2,400 or 3,000 meters, below the river level, 
