26 C. R. VAN HISE THE PROBLEM OF THE PRE-CAMBRIAN 



^?;t ° T^?"^ ■ , iT^:^^ limestone | gj^^ limestone, and quai tzite. 



(Neo-Proterozoic). Tou-tsun slates j ' ' ^ 



Unconformity. 



Si-t'ai series Chiefly chlorite schist ; quartzite 



conglomerate at the base. 

 Unconformity. 



Wu-t'ai system -j Nan-t'ai series Siliceous marble, jasper quartz- 



(Eo-Proterozoic) . 



ite, and schist. 

 Unconfoi'mity. 



Shi-tsui series Mica schists, gneiss, magnetite 



quartzite, and basal feld- 

 spathic quartzite. 

 Unconformity. 



T'ai shan complex Basal complex of varied gneisses 



(Archean). and younger intrusives. 



The descriptions of the Archean, or basement complex, show that it 

 consists dominantly of gneisses, probably largely derived from igneous 

 rocks. Within these gneisses are various intrusives among which granite 

 predominates. Very subordinate masses of sedimentary materials are 

 found. In short, the descriptions of this complex show that it has all of 

 the characteristics of the Archean. The four sedimentary series uncon- 

 formably above the Archean are composed of rocks which were originally 

 muds, grits, conglomerates, and limestones. In other words, they have 

 all of the characteristics of the Algonkian. 



There is thus a remarkable similarity between the Archean and the 

 Algonkian of China and similar groups in North America. Indeed, the 

 number of certainly recognized groups of sedimentary rocks of pre- 

 Cambrian age are precisely the same as the Lake Superior region. Willis 

 suggests that the three lower series which he groups into the Wu-t'ai sys- 

 tem are equivalent to the Huronian of the Lake Superior region, which 

 also is divisible into three unconformable series. This would leave the 

 Hu-t'o system to be correlated with the Keweenawan. However, it would 

 not be well to too strongly emphasize the close correlation suggested; but 

 certainly the similarity of the succession is astonishing and suggests the 

 possibility that in the future we may yet be able to correlate the uncon- 

 formable series in the Algonkian in provinces separated as far from one 

 another as the Lake Superior region and northern China. The similarity 

 of the succession in Finland gives additional emphasis to this suggestion. 



In the classification of the Algonkian presented by Willis for China he 

 introduces into the nomenclature of the pre-Cambrian the words "Neo- 

 Proterozoic" and "Eo-Proterozoic." I wish to question this suggested 

 practice, since I can see no philosophical Imsis on which such a division 

 can be made ; nor do the facts as described seem to me to require any such 

 division. Indeed, no adequate reason is advanced or even suggested for 



