CHAPTER VII. 
STRUCTURAL GEOLOGY OF THE NING-SHAN BASIN. 
By BAILEY WILLIS. 

The Ning-shan basin is an isolated occurrence of Paleozoic rocks 
northwest of the city of T’ang-hién. The rocks of adjoining areas are 
Pre-Cambrian and consist of two series, the T’ai-shan gneissic complex, 
and the Ta-yang formation. The Paleozoic rocks consist of the Ki-chéu 
limestones, which are Cambro-Ordovician, and the Shan-si coal-bearing 
series, which is Carboniferous. There is also a small area of conglomerate, 
which is probably of late Mesozoic or Tertiary age. These strata have 
been described in the preceding chapter. In what follows regarding struc- 
tural geology, I rely to a great extent upon Blackwelder’s notes, as I was 
necessarily absent from the field of surveying during part of the time which 
we spent in the district. 
The structure of the T’ai-shan complex is that of an intricate sequence 
of gneisses, mostly of intrusive rocks, and is of such a character that 
the series is with reason referred to the Archean on the strength of the 
structural evidence. The Ta-yang limestones overlie the T’ai-shan uncon- 
formably, and are clearly differentiated from it stratigraphically and 
lithologically. They belong among the latest Pre-Cambrian rocks. Gray 
limestones, not notably metamorphosed, though, where argillaceous, locally 
schistose, they are distinguished from Paleozoic limestones by the occur- 
rence of chert in numerous layers and lenses. Although the bedding is 
massive, the strata are slightly folded and probably much repeated in the 
mountains north and northwest of Si-ta-yang. One of the best sections 
observed is between T’ang-hien and Nan-t’ang-mei. For 6 miles, 9.5 
kilometers, northwest of Ta-yang the surface consists of gneiss, thinly and 
but partly covered with loess. In the banks of a small stream which flows 
northeast, the contact of the cherty limestone on the gneiss is exposed, and 
thence for a distance of 3 miles, 5 kilometers, to Nan-t’ang-mei, limestone 
may be seen in the mountains adjacent to the valley. The dip is in general 
to the northwest, usually about 25°, with some slight anticlines and syn- 
clines. Two small normal faults hading steeply to the south are seen, 
and the strata are traversed by a dike of quartz-porphyry. ‘The facts as 
observed are indicated in the diagram, Fig. 27. At the northwestern end 
153 
