3O RESEARCH IN CHINA. 



During the early Proterozoic a synclinorium developed on the site of 

 the present Wu-t'ai-shan of northern Shan-si, and in it were deposited 

 sediments which correspond in sequence with the progress of a cycle of 

 erosion from youth to old age and subsequent marine transgression. These 

 sediments were probably common to a zone which extends from the type 

 locality northeast and southwest; in the latter direction it enters the 

 Ts'in-ling-shan and thence curves west to northwest across Tibet in the 

 Kuen-lung system. The corresponding diastrophic movements were epei- 

 rogenic, and they passed into a phase of quiescence such as has since 

 repeatedly characterized such movements. It is probable that there was 

 more than one epoch of erosion, at least one unconformity being recognized 

 in the sedimentary series. 



At a period which may be described as mid-Pro terozoic, the zone of 

 early Proterozoic sediments was sharply and intensely deformed. The 

 disturbance was apparently accompanied by granitic intrusions of large 

 volume, which were then or afterward rendered schistose in common with 

 the folded strata. The events were complex. The movements may be 

 classed as orogenic, since they resulted in deformation of strata by folding 

 and thrusting in an apparently well-defined zone. The strikes follow the 

 Baikal direction, northeast-southwest in North China, change in the 

 Ts'in-ling-shan to east-west and northwest, and extend to the Kuen-lung. 

 They thus form an arc outside that of the Baikal-Saian curve, embrac- 

 ing Mongolia, as was perceived by von Richthofen* and has been brought 

 out by Suessf and others. This period of orogeny was for the provinces 

 affected equally as important, apparently, as the intense orogenic disturb- 

 ances which mark the Permo-Mesozoic period in Central Asia and the 

 western United States. It was very possibly an incident of a period of 

 diastrophic activity such as closed the Paleozoic. 



After a period of erosion, during which the altitudes that had resulted 

 from the preceding activity were materially or completely reduced, but of 

 which no sedimentary record is known, there followed a cycle characterized 

 by the deposition of littoral sediments in the typical district of the Wu-t'ai- 

 shan, and of marine limestones in a trough which traversed eastern China. 

 Strata, which may be equivalent, occur in the Nan-shan range of northern 

 Tibet. The deposits again correspond with the phases of an erosion cycle 

 from youth to old age, and finally represent a transgression over a low 

 continent . 



The last event of the Proterozoic (pre-Sinian) era was a movement 

 which is recorded in folding of the latest pre-Cambrian sediments ; although 

 possibly a local phenomenon of the littoral zone, so far as is yet known, it 



*China, vol. n, pp. 635 el seq., 647. 

 t Face de la Terre, vol. HI. 



