STRATIGRAPHY OF CHI-LI AND SHAN-SI. IOs; 
which he had already seen in many other parts of China. Willis, en route 
from Tai-chéu to Chang-hién-pu, also found gneiss 3 miles, 5 kilometers, 
south of the base of the northern slope. It is a granitoid gneiss cut 
by large dikes of schistose greenstone, and is followed by quartzite and 
schists of the Wu-t’ai system. 
Another small area of gneiss, which may possibly be part of the T’ai- 
shan complex, or may be much younger, is exposed in the higher portion 
of the Wu-t’ai range, on the summit and upper slope of Pei-t’ai. 
CORRELATION. 
In the provinces of Shan-si, Chi-li, and Shan-tung the oldest meta- 
morphic complex presents almost identical development, and we believe 
that we have to deal with the same basal system in the several areas. The 
rocks appear to be largely of igneous origin, though in part sedimentary, 
and contain abundant acid and basic intrusions belonging to many genera- 
tions of igneous activity. They are characterized by exceedingly complex 
structure and advanced metamorphism. ‘The stratigraphic position is 
everywhere basal, the complex underlying Paleozoic or Algonkian sediments 
and being itself bottomless. Such is the identity of constitution and 
stratigraphic position throughout northern China that the name T’ai-shan, 
applied to the system in the type locality in Shan-tung, is extended to the 
other masses which we observed in Chi-li and Shan-si. 

SS 
wh XS 
Ca Sa 
<i AS Sg 
AR S NN S 
S ANS Tae Wd = Se SSS 
\ ROA NAY x BWR 
CN 2? NOS 
. 
a 
fo) 2 ‘MILE 

Fic. 20 (Blackwelder).—4 miles, 6 kilometers, south of Shi-tsui, Shan-si. Augen-gneiss in contact with 
lower members of the Shi-tsui series. a= biotite and chlorite-schists; b = mottled green and pink 
amphibolite; c= white sericite-schist; d= brownish arkose quartzite; e= biotite-schist; f= brown 
micaceous quartzite; g = massive gray augen-gneiss. 
The characters of the T’ai-shan complex are so distinctive and so fun- 
damental that we feel justified in correlating it with the similar systems of 
America and Europe, as the Archean; but we also recognize that the 
masses to which the name is applied in this report and accompanying 
maps include granites and other intrusives of Algonkian and later eras. 
UNCLASSIFIED PRE-CAMBRIAN. 
Augen-gneiss.—Along the T’ai-shan-ho, 4 to 7 miles, 6 to 11 kilometers, 
above Shi-tsui (Plate XVIII), and again about 4 miles, 6 kilometers, below 
that village (Fig. 20), we found a gneiss which is different from any seen 
