STRUCTURAL GEOLOGY OF THE NING-SHAN BASIN. 155 
closely appressed and the folds overthrust toward the southeast. Over- 
thrust faults were detected at Mi-chéng and also south of Ning-shan, and 
it is probable that they are quite numerous in the limestone mass. In 
the district northwest of Ning-shan the Carboniferous is faulted down 
against the Ordovician along two normal faults of moderate throw, and 
a third normal fault, stretching northwest of the other two but parallel 
to them, brings down the Ordovician in contact with the underlying 
T’ai-shan gneiss and forms the northwestern margin of the basin. We 
thus have in a small area, only about 6 miles across, close folding, over- 
thrust faulting, and normal faulting in complex relations. Our obser- 
vations do not suffice to untangle these relations in detail, but the map 
(atlas sheet FI) and the generalized structure sections, Figs. 48 and 
49, suffice to express the broad relations. 
There is one problem which remains obscure, namely, the abrupt 
termination of the Ning-shan basin toward the southwest. According to 
the strike and dip of the strata, the Paleozoic rocks should appear south- 
west of the Sha-ho, where we might expect that they would form high 
ridges as they do northeast of it; but the area in which we would look for 
them exhibits exposures of the T’ai-shan complex. It is evident from an 
inspection of the map that the overthrust fault along the southeast side 
of the basin gradually approaches the base of the Carboniferous rocks, 
cutting out the underlying Ki-chéu limestone, and it is highly probable that 
the Ta-yang limestone is lacking in consequence of Pre-Cambrian erosion 
over part of the area in which the overthrust brings the Paleozoics in 
abnormal contact with the T’ai-shan. It may thus occur that the Carbon- 
iferous is brought into overthrust contact with the T’ai-shan gneiss, and 
being eroded west of the Sha-ho, has exposed the latter below the plane 
of overthrust. The available facts of structure and distribution do not, 
however, afford a similar explanation for the abrupt termination of the 
high mountain range, which forms the extreme western corner of the 
basin, 8 miles, 13 kilometers, west by south of Ning-shan. We may infer 
that the Paleozoics end against a more or less complex system of overthrust 
or normal faults, but we have not the data by which to test the inference. 
The movements which have resulted in folds and overthrusts in 
this district apparently belong to a single episode of compression. The 
folding of the Ki-chéu limestone is shared by the Carboniferous strata, and 
the two appear to be conformable in dip where we observed them. We 
are thus led to assign the episode of deformation to a post-Carboniferous 
time. It is in all probability to be correlated with effects of compression, 
observed elsewhere in the mountains of Chi-li and Shan-si as a post-Jurassic 
movement. 
