STRUCTURAL GEOLOGY OF THE MIDDLE YANG-TZI PROVINCE. 287 
t’an (Middle Paleozoic) shale occurs in its proper place below the lime- 
stone, but we did not see it. 
Between Nan-mu-ytian and Wu-shan-hién the Yang-tzi flows across 
a sequence of smaller and larger folds, chiefly of the Ki-sin-ling limestone, 
but at the head of the gorge consisting of the Wu-shan limestone. The 
sequence will best be understood by reference to the section (Fig. 61) 
which was sketched as we floated past the magnificent cliffs in which it 
was exposed. As we could not measure distances, the distribution along 
the river was noted, and has since been adjusted to Chevalier’s map of the 
Yang-tzi.* Two anticlines and a syncline bring the top of the Ki-sin-ling 
limestone high above the stream above and below Nan-mu-yiian. For 
several miles below Ts’ing-shi-tung the course is in the axis of a carinate 
syncline, a position determined by the Sin-t’an shale, although the canyon 
is now sunk below that formation in the Ki-sin-ling limestone. The 
thin beds of the latter dip very steeply, but above them, in a nearly flat 
position, the Wu-shan forms the upper cliffs. From half a mile above 
7 Saas 
Fic. 61. (Willis) ——Wu-shan gorge of the Yang-tzikiang. Section between Wu-shan-hién and Kuan- 
t’ou-k’6u, showing the folds in Paleozoic strata, from Cambro-Ordovician to Carboniferous, inclu- 
sive. a= Kuan-t’ou-k’6u; b= Nan-mu-ytian; c= Ts’ing-shi-tung; d= Wu-shan-hién. 

Ts’ing-shi-tung the synclinal valley extends westward, but is occupied 
only by a small tributary. The lower part of the Wu-shan gorge is cut 
across a great anticline of the Ki-sin-ling, the arch extending up to the 
mountain tops 3,000 feet or more above the river. The inner part of the 
anticline in the thin-bedded strata near the base of the formation is there- 
fore exposed along the water level, and is seen to be characterized by 
many sharp folds and possibly by minor overthrusts. The details could 
not be followed as we passed, but the major structure was clear. Finally, 
toward the west, the dip is continuous on the northwestern limb of the 
arch, and the Sin-t’an shale comes in above the limestone. The shale is 
overlaid by the Wu-shan limestone with the characteristic black chert 
of the lowest beds. There is a repetition of the shale and limestone with 
black chert, occasioned by a slight overthrust at this horizon of adjust- 
ment, and then follows the mass of the Wu-shan limestone forming the 
upper part of the Wu-shan gorge. Northwest of the grand arch of the 
Wu-shan limestone, probably one of the most superb exposures of a fold 
in the world, the K’ui-chéu red beds occur in the syncline, and the Yang- 
tzi valley is developed in them for some miles westward. 
*R. P, Le Chevalier. Carte du haut Yang-tze, 
