CHAPTER XVI. 
ROCKS FROM NORTHERN AND CENTRAL CHINA. 

By Exviotr BLACKWELDER. 

INTRODUCTION. 
In the chapters on stratigraphy, the field relations of the rocks have 
been described and the prominent varieties have been briefly discussed. 
The more elaborate descriptions of rocks, depending upon the microscopical 
study of the specimens collected, are reserved for this portion of the report. 
The rocks have been classified in the first instance by districts, secondly 
by geologic age, thirdly by mode of origin, and fourthly by petrographic 
character. In the detailed geological report, six districts were distinguished 
for convenience in description. In the present work eleven will be recog- 
nized, some of which correspond to those mentioned above, while others 
are either new or have been formed by subdivision of the old districts. 
They are named as follows: Khin-gan district, Liau-tung district, Liau-si 
district, Peking basin, western Shan-tung, eastern Shan-tung, western 
Chi-li, Wu-t’ai district, Ts’in-ling district, Han river district, and Yang- 
tzi gorge district. Within each of these divisions there is a_ general 
similarity among the rocks, as contrasted with the assemblages which 
characterize other areas. It is not intended, however, to convey the 
idea that they represent definite petrographic provinces; the material at 
our command is, in most cases, entirely insufficient to attempt a classi- 
fication of that nature which could stand the test of more detailed work 
in the future. The sedimentary and metamorphic rocks are here classified 
according to the system used by Van Hise,* while the igneous varieties 
are named and arranged in general accordance with the usage of recent 
petrographers. 
In studying the rocks from China, the writer has had the privilege of 
consulting Professor J. P. Iddings, of the University of Chicago, and Profes- 
sors C. K. Leith, W. H. Hobbs, and W. O. Hotchkiss, of the University of 
Wisconsin. The advice and criticism they have freely given add largely 
to the value of the work. 
* Van Hise: A Treatise on Metamorphism, U. S. Geol. Survey, Monograph xLvu. 
357 
