BASIS OF PRE-CAMBRIAN CORRELATION 2i 



The succession here is as follows:' 



Neo-Proterozoic \ Tung-yu limestone Slates, limestones 



(Hu-t'o system) / T'ou-t'sun slates and quartzite. 



Meso-Proterozoic / Si-t'ai series Chiefly chlorite schist ; quartzite 



conglomerate at the base. 



Siliceous marble, jasper, quartz- 



(Wu-t'ai system) \ Nan-t'ai series ite, and schist. 



Mica schists, gneiss, magnetite 



Shi-toui series quartize, and basal feldspathic 



qiiartzite. 



Eo-Proterozoic T'ai-shan complex Basal complex of varied gneisses 



and younger intrusions. 



The lowest of these series, the T'ai-shan, resembles the Keewatin 

 penetrated by Laurentian intrusions, being 



a metamorphic complex, the constituents of which are largely igneous, though 

 perhaps in part sedimentary in origin. ^ 



This was brought to a close by a period of intense diastrophism. 



Suceeding this: 



We distinguish with great certainty a great thickness of very early Proterozoic 

 sediments — the Wu-t'ai — which were intensely deformed and metamorphosed 

 during a mid-Proterozoic epoch of orogeny, owing to pressure exerted by the 

 outlying negative elements, and a later Proterozoic series — the Hu-t'o — which 

 represents shore conditions and which was moderately deformed by pressure 

 exerted by the same cause at the close of the Proterozoic. 



Applying therefore this criterion of diastrophic epochs to the 

 correlation of the Proterozoic succession of these widely separated 

 portions of the great northern nucleus, we obtain an identical result 

 in both cases — the diastrophic movements seem to have affected the 

 nucleus as a whole. 



It would seem that these diastrophic epochs designate certain of 

 the unconformities in the succession both in the Siberian portion of 

 the nucleus and in Laurentia, as major, dominant, and of special 

 importance, and others as subordinate and of minor importance. 

 We thus have indicated a division of the Proterozoic into Eo-, Meso- 

 and Neo-Proterozoic. On this basis of correlation the T'ai-shan 

 corresponds to the Keewatin-Laurentian complex; the Mu-t'ai to 

 the Lower and Middle Huronian, and the Hu-t'o to the Animikie- 

 Nastapoka series. 



I Research in China, Vol. II, p. 4. * Ihid., Vol. I, Part I, p. 19. 



