BASIS OF PRE-CAMBRIAN CORRELATION a7 
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 
ee series quartize, and basal feldspathic 
quartzite. 
o-Froterozoic......'.. 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. 
t Research in China, Vol. Il, p. 4. 2'Tibtd.,, Vol. 15 Part I, pi. 10. 
