CHAPTER I, ARCHEAN. 



The term Archean has been used in Asiatic geology by different writers 

 to cover various metamorphic but usually ancient rocks. Generally it is 

 applied to any highly metamorphic or igneous rocks which are older than 

 the oldest clearly recognized sediments of any particular district. In the 

 literature "Archean" thus covers rocks which range in age from the very 

 earliest pre-Paleozoics observed in the continent to Paleozoic, or possibly 

 even Mesozoic strata, where these have been greatly altered. Moreover, 

 the intrusives have commonly been grouped with the schists, although 

 they are certainly somewhat younger, and it is sometimes difficult to say 

 how much younger. Thus, granites which reav be of Paleozoic or Mesozoic 

 age are classed as pre-Paleozoic. 



In these volumes the term Archean is applied to a basal mass of gneisses 

 and schists, which is also designated the T'ai-shan complex. It is regarded 

 as basal because it underlies all other recognized groups and is separated 

 from them by an unconformity of a most distinct and profound character; 

 moreover, it is fundamental among rock masses known at the surface, 

 because it is itself apparently bottomless. Nothing distinct from it and 

 older than it has as yet been identified. 



The T'ai-shan complex is not everywhere followed by rocks of the 

 same age, the geologic record being incomplete in China as elsewhere. In 

 the Wu-t'ai district of northern Shan-si, it underlies the Shi'-tsui group of 

 the Wu-t'ai schists, probably the oldest group of sedimentary deposits 

 identified in Asia. The most probable rough correlation places this sequence 

 in parallelism with the lower Huronian and Keewatin of the Lake Superior 

 region of North America.* 



In northeastern China, in the province of Shan-tung, is the type locality 

 of the T'ai-shan complex, Mount T'ai. The most ancient rocks are there 

 overlain by Lower Cambrian strata and the pre-Cambrian sediments are 

 wanting; correlation with the Archean of the Wu-t'ai district is based on 

 similarity of lithologic and structural characters, which are common to all 

 the occurrences which we have classed as T'ai-shan and are not shared by 

 any other rock masses of known superior position in the geologic scale. 



* Report of special conimittec for the Lake Superior Region, Chicago Journal of Geology, vol. xiu, 

 p. 89, 1905. 



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