GEOLOGY OF CENTRAL SHEN-SI. 303 
yet the fossils collected above and below indicate that Silurian and Devo- 
nian time are represented by very meager sediments. Much further north, 
in Shan-si, we found an unconformity by erosion at the base of the Car- 
boniferous. Somewhere in the intermediate zone there should be the 
conglomerates of the littoral between the flat lowland and the clean sea 
bottom. This conglomerate north of Tséng-kia-pa may be such an occur- 
rence. The character of the Wu-shan strata is that of the base of the 
formation, and the position indicated by our observations of strike and 
dip, traced from the contact with the Sin-t’an argillites south of Pai-kiu- 
hia, is close to or on that contact. The sequence from older to younger 
is from the conglomerate to the Wu-shan, unless the strata are over- 
turned. A conglomerate was observed at this horizon on the Han near 
Yii-fang-p’ing, atlas sheet a 4. On these grounds we regard this con- 
glomerate as being at the base of the Wu-shan. 
The Hung-shui-ho, which 
pe hatin he flows eastward past Tséng-kia- 
: == ~- Een, pa, brings down large quantities 
Sip ae ane Ih: of gabbro, but we did not see 
- erie le ——~., any intrusives in place in this 
ig 
Sa ae part of the section. 
a ae a. < 
<—— About 2 miles, 3. kilo- 
—-—- meters, south of Pa-kua-miau 
a arr the Wu-shan formation is suc- 
ji ~ ceeded by hard gneissic gray- 
ee a wackes, which appear to come 
Fic. 65.—Fold overthrust southward near Ku-niu-tu, in over the black slates and 
oe: argillites. These schists are 
brown-gray or russet-colored rocks, in which micas have developed in 
parallel arrangement. That the rock is, however, only moderately 
metamorphosed is indicated by the fact that the larger grains of quartz 
and feldspar in the original graywacke are still unaltered. The gray- 
wackes continue in a northwesterly direction, with northeasterly dips, 
and become associated near Pa-li-kuan with silvery gray slates, which 
recur in the valley southeast of P’ing-li-hién. In the interval of 5 miles, 
8 kilometers, our route was occasionally on black slates and siliceous 
argillites of the Wu-shan formation, either because we meandered across 
the contact or because of outcrops on minor folds. 
The graywacke and silvery slates of this section, from south of Pa- 
kua-miau to P’ing-li are unfamiliar rocks, not like the Sin-t’an shale in 
any metamorphic phase of that formation which we recognized, and yet 
in sequence with the Wu-shan limestone. The structural relations are 
