OBSERVATIONS IN CENTRAL SHAN-SI. 175 
throughout the region. If, on the other hand, the strata are more or less 
folded, it is probable in view of the moderate thickness of the Shan-si 
coal-measures that the underlying Sinian limestone, and possibly the 
Pre-Cambrian rocks, constitute the surface over extensive areas, and the 
coal-measures occur in more or less restricted synclines. In general it 
seems probable that the structure of the so-called plateaus of Shan-si is 
marked by extensive folds having a north-by-east south-by-west parallel 
arrangement. 
NORMAL FAULTING. 
(See map, Plate XXIII.) 
The normal faults of Shan-si and Shen-si lie en échelon in a curve of 
450 miles, 725 kilometers, trending from south by west at the north to 
nearly east-west at the southwestern end, and convex toward the southeast. 
The downthrow is on the inner concave side of the curve, the upthrow on 
the eastern or southern side. The fractures are not continuous, as each 
one passes into a warped surface at either end. The altitude of the moun- 
tain ranges associated with the faults varies accordingly, and thus we have 
great crests like that of the Ho-shan alternating with moderate altitudes, 
which are crossed by the principal highways. 
The most northern of the normal faults of this system is that along 
the base of the Ki-chéu-shan, bounding the Hin-chéu basin on its south- 
eastern margin. Stratigraphic evidence of faulting is found near the 
northeastern end, where the Sinian strata are duplicated in the hills south 
of Tung-yii; but similar relations are not visible along the greater part 
of the course of the fault, as the rocks of the downthrow are deeply buried 
beneath the loess that fills the Hin-chéu basin. The straight front of the 
range, the manner in which the short ridges which mark it are truncated 
by steep triangular facets that fall approximately into a common surface, 
and the occurrence of slickens and grooves on such surfaces, suffice, how- 
ever, to establish the fact of faulting. The preservation of slickens or 
grooves on the fault facets is, it is true, not common, as they are liable to 
erosion; but we have an observation by Blackwelder, who found them on 
a surface of coarse red granite, 4 miles, 6.5 kilometers, southeast of Han- 
yang, at a point where the rock rises with a steep front from the alluvial 
fans. He describes the surface as striking south 60° west, dipping 63° 
northwest, and strongly grooved in a vertical direction. 
The second element of the fault system which we observed is the 
Ho-shan fault south of T’ai-yiian-fu. Between it and the Ki-chéu-shan 
fault there is a space of 75 miles, 120 kilometers, and the two are not in 
alinement. The more northern one ends further to the west. The Ho-shan 
fault runs about north 10° east, and defines the valley of the Fén from 
the vicinity of P’ing-yang-hién to abreast of Hung-tung-hién. Its length 
