STRUCTURAL GEOLOGY OF SHAN-TUNG. 69 
NORMAL FAULTING IN WESTERN SHAN-TUNG. 
Distribution.—As mapped by von Richthofen three principal faults 
define the broken area and a fourth cuts into it north and south. Of the 
three which bound it, one lies along the southern base of the T’ai-shan chain, 
striking N. 65° E., with the upthrow on the northern side. The existence 
of this fault is indicated by the presence of rocks of Middle Cambrian age 
in the plain near T’ai-an-fu, at the base of the great mass of granite and 
gneiss of Pre-Cambrian age, which constitutes the T’ai-shan. This may be 
called the T’ai-shan fault. The second limiting fault lies along the south- 
western margin of the area, between the Sinian rocks of the southwestern 
foothills and the Pre-Cambrian rocks of the Kiu-nti-shan and Shi-mén- 
shan. We did not observe this fault and it has not been traced by a 
geologist throughout its extent. It was observed by von Richthofen 
near I-chéu-fu, and is represented on our map as given by him. It is 
possible that it is not a continuous fault, but is offset, as are the two ranges 
above named (see Plate XII). The upthrow is on the northeast, and 
the fault is closely parallel and similar in dislocation to that which we 
have designated Na and which passes through Sin-t’ai. On the north- 
eastern side of the faulted area von Richthofen shows a line of contact 
between the Sinian and the Pre-Cambrian rocks of the I-shan, which 
appears to indicate another great dislocation nearly parallel to these two. 
The fault which comes into the area from the north was recognized by von 
Richthofen near Po-shan, and is one of the series traced by us to 
Yen-chuang. 
The effect of these great dislocations is to define a sunken area within 
high mountain chains. Roughly speaking, the area is a triangle. Its acute 
apex is pointed toward the west and is situated west of T’ai-an-fu, between 
the T’ai-shan and the Shi-mén-shan. Its southwestern side corresponds 
with the Shi-mén-shan fault. Its northern side, consisting of the T’ai- 
shan and the I-shan faults, is offset along the north-south Po-shan fault, 
and its southwestern side sinks gently beneath the adjacent sea without a 
break. As the upthrow of all these principal faults is on the northeastern 
or northwestern side, the general effect is to produce a series of tilted blocks. 
Within the area of dislocation the details of faulting are such that 
there are many peaks quite as high as the crests of the surrounding ranges, 
except the T’ai-shan. As will be further discussed in connection with the 
physiography, the master streams lie along the downthrown margins of 
the greater blocks, and the valley of the W6n-ho, which, even for Shan- 
tung, is unusually broad and level, probably corresponds with an extensive 
depressed area. 
