PROTEROZOIC, CENTRAL CHINA. 13 



Sinian (Cambrian) transgression; and if that be the case it falls into von 

 Rich thof en's "Obersinisch." 



In Shan-tung von Richthofen distinguished a metamorphic series 

 which included limestone and certain quartzites. The two were not seen 

 in contact and their relations remain indeterminate between themselves 

 as well as to similar metamorphic formations elsewhere. The sequence, 

 which includes crystalline limestone, occurs in eastern Shan-tung, between 

 Chef oo and Tong-chou-fu, with a thickness of several thousand feet. The 

 lower part is mica schist, which, higher in the succession, gives place more 

 and more to alternating limestone beds which attain great thickness and 

 make up the upper part of the system in the "Kung-sun-shan." This strati- 

 graphic sequence resembles that of the lower Wu-t'ai series of Shan-si, and 

 the antiquity of the rocks, as judged by schistosity and metamorphism, is 

 similar ; but the series may be of some other Proterozoic age. 



The quartzites occur near Ch'ang-kiu-hien, in eastern Shan-tung, and 

 constitute a mountain mass cut through by diorite. They are much folded 

 in a region where the Sinian is not, and are of pre-Sinian age, probably 

 equivalent to the Ta-ku-shan quartzites, according to von Richthofen. 



PRE-SINIAN ROCKS OF CENTRAL CHINA. 



The typical occurrences of rocks of the Wu-t'ai and Hu-t'o or Nan- 

 k'ou systems are confined to the eastern part of the continent. They lie 

 2 to 4 of longitude west of the present eastern coast, between the parallels 

 of 38 and 40 north. In the same latitude they are 24 to 26 east of the 

 central meridian of Asia, which we may take as longitude 90 east. They 

 are apparently isolated areas, known only in the mountainous region of 

 northwestern China, and may eventually prove to be provincial systems, 

 which can not be precisely correlated with terranes of other regions. A 

 similar condition exists in North America, where rocks of Proterozoic age 

 are known in several widely separated districts, but they have not been 

 more closely correlated than as earlier and later Proterozoic. Nevertheless, 

 rocks having the lithologic characters of the Wu-t'ai and Nan-k'ou strata 

 and holding a somewhat similar position between those which are classed 

 as Archean and deposits which are identified as Paleozoic, are known else- 

 where in Asia, and it is desirable to place them roughly in parallelism. 



Our own observations are limited to a single section of the Ts'in-ling- 

 shan, Shen-si, and the outcrop in the lower Yang-tzi' gorges, Hu-pei.* Von 

 Richthofen, f Loczy.f and Obrutchov are the original observers upon 



*Vol. i, pp. 265 and 313. 



t China, vol. n, p. 557 et seq. 



JReise des Grafen Sze'chenyi in Ostasien, vol. I, chapters vn, vm, and rx. 



Northern China and the Nan-shan (in Russian). 



