STRATIGRAPHY OF CHI-LI AND SHAN-SI. 133 
of the strata. The nodular layers and lamine are much more abundant 
than the separate nodules. They are usually blackish in color, but are 
sometimes gray or white. The thin quartzites, which have been mentioned 
as constituents of this limestone series, are usually white in color and occur 
in isolated beds 5 or 6 feet, 1.5 or 2 meters, in thickness. The entire 
sequence at this place is estimated at about 1,200 feet, 375 meters. 
The limestone is apparently overlain by a series of soft rocks, which 
consist partly of quartz-biotite, and sericite-schists, alternating with sev- 
eral layers of white quartzite. The thickest of these quartzites form 
several low ridges, which barely rise above the alluvium at the base of the 
limestone hills. The schist and quartzite group was not observed at any 
point beyond this locality northwest of Wan-hién. 
Vicinity of T’ang-hién.—The belt of the Ta-yang limestones was 
crossed three times in the region northwest of T’ang-hién. The gray, 
flinty limestones were found lying upon the basal complex and dipping 
gently northward (Fig. 30). Along much of the northern edge of the 
exposure the Sinian limestones are overthrust upon the older rocks and 
cut off whatever may have overlain the Ta-yang limestones. Near Nan- 
t’ang-mei, however, the fault apparently dies out and the uppermost 
Ta-yang limestones are overlain by about 100 feet, 30 meters, of conglom- 
eratic breccia (Fig: 27), which consists almost entirely of rounded pebbles 
and fragments of black, white, and banded flint, embedded in a hard sili- 
ceous matrix. Upon this lies a quartzite 50 feet, 15 meters, thick, which 
is in turn followed by more than 60 feet, 18 meters, of dark purple argillite. 
The conglomerate breccia was at first taken for a silicified fault breccia, but 
was found to have a more definite stratigraphic position and greater extent 
in the adjacent hills than would be expected. It exhibits a tendency to 
bedding and dips gently northwest with the overlying Sinian shales. From 
the underlying Ta-yang limestone, chert weathers out in great abundance 
and should occur in any basal conglomerate of an unconformable younger 
formation. The petrographic examination of a specimen of the conglomer- 
atic shows it to be of sedimentary clastic origin. Thus we are led to con- 
clude that it is a peculiar local deposit at the base of the Sinian, the lowest 
Sinian being elsewhere in this district and generally a red shale. Limited 
deposits of conglomerate of various local materials were, however, seen at 
several points in Shan-si. The silicified mass of the conglomerate-breccia 
is closely sheared on planes which strike N. 30° W. and dip 70° to 85° NE. 
It may also have been a plane of thrusting, and probably exhibits the 
characters of an auto-clastic rock as well as those of a basal conglomerate, 
though the particular specimen collected does not, under the microscope, 
show effects of strain. 
The village of Si-ta-yang is situated near the contact of the flinty 
limestones and the gneiss. The strata dip gently northward at first, but 
