24 RESEARCH IN CHINA. 



PRE-S1NIAN DIASTROPHISM.* 



Diastrophism is a phenomenon which finds expression in the oldest 

 rocks as well as in the youngest mountains of all continents, and of this 

 general fact Asia is the most striking illustration which the earth presents. 

 Large areas exhibit rocks which have been intensely deformed and are 

 among the most ancient known ; and the greatest mountain chains challenge 

 credulity by the evidence of their extreme youth. The earlier diastrophic 

 movements escape us in the mists of unrecorded ages of earth-history; we 

 take up the observation only where the facts become partly intelligible; 

 but from that remote time to the present we find a connected series of 

 events. 



Suess describes these facts and draws the conclusion that: 



The compressive force formerly acted throughout the entire expanse of the globe, 

 whereas now it is localized in certain special regions.")" 



An alternative view may be stated: namely, the widely distributed 

 effects of schistosity are produced in masses that lie in a relatively deep- 

 seated zone, where movement is somewhat uniformly distributed ; whereas, 

 special regions of folding are peculiar to a relatively superficial zone, in 

 which movement is localized and concentrated by special conditions of 

 structure and resistance. That is to say, the distinction between widely' 

 '. distributed and localized structures is one of depths rather than of times. 

 This view is stated more in detail in the final chapter of this volume. 

 Applying it to the explanation of the general structure of the Archean, 

 we may reason that the masses which that structure characterizes were 

 deformed in a zone at such a depth that they were below any localized 

 erogenic effects. That there were regions of special plication, even in the 

 Archean is probable, but the superficial folded masses have been eroded. 



Gneisses and schists constitute the T'ai-shan complex of China and 

 also the corresponding rocks described by many observers in Siberia, central 

 Asia, India, and Indo-China, and designated "older Archean." They are 

 everywhere fundamental rocks; their constitution is very complex; they 

 consist of minerals resulting from extreme metamorphism under great 

 pressure; and their larger structure exhibits repeated intrusions, often 



*Following Powell and Gilbert (U. S. G S. Monograph I, pp. 3-340) I shall use the term diastrophism 

 to denote all the processes of deformation of the earth's crust, and shall distinguish between orogenic move- 

 ments, which result in the commonly observed phenomena of mountain ranges and mountain structure, 

 and epeirogenic movements, which are expressed in the elevation or depression of broad areas and are 

 recorded in eroded surfaces or accumulated sediments. The distinction is one which has found little, 

 if any, recognition in the literature relating to Asia, but which is fundamental and clearly recognizable in 

 the geologic facts. 



|La Face de la Terre, vol. in, p. 7. 



