CHAPTER VII. CONTINENTAL ASIA. 



CRETACEOUS. 



A geologist taught only by observation in China, outside of Tibet, 

 would know nothing of the Cretaceous. No strata are known which may be 

 correlated with the strata that represent the period in America and Europe. 

 We would look for marine or continental deposits in the middle Yang-tzi 

 region or the Red Basin of Ssi-ch'uan, where they might cap the Jurassic 

 in the deeper synclines; or about the margins of the great alluvial plain of 

 the Yang-tzi and the Huang-ho, where they might outcrop in the foothills; 

 but they are not found. If they ever existed above the known Jurassic they 

 have been eroded; if they underlie the plain they are overlapped. 



Nor are Cretaceous strata of any kind known in the vast area of Asia 

 north of Tibet, east of the Urals, and south of northern Siberia. No other fact 

 than this, perhaps, more sharply challenges the hypothesis that the present 

 mountain ranges and basins of central Asia date from a pre-Cretaceous 

 time. Highlands without waste and waste without deposit in these interior 

 basins are inconceivable; but though the plateaus are affected by post- 

 Cretaceous dislocations which expose even the ancient crystallines, there 

 is no trace of deposition during the Cretaceous period. The surface that 

 could for so long a time maintain a blank record must have been a land 

 in which transportation and aggradation had ceased in consequence of 

 uniformity and flatness of slope a well-developed peneplain. Even on 

 such a surface subaerial decay must produce residual material and the 

 atmosphere do some work; but the product might be worked over into 

 later deposits, as it probably has been. 



Some of the waste from this Cretaceous land found its way into the 

 southern Tethys, where it formed the Giumal sandstone. The area of 

 deposition extends throughout the Himalayas, over southern Tibet, and 

 through Kashmir into Afghanistan and Persia.* 



The rock is a greenish-gray sandstone, sometimes very siliceous, and 

 of considerable thickness. There is a transition to it from the underlying 

 Jurassic shales, and it is separated by a sharp but conformable contact from 

 the overlying upper Cretaceous limestone, which extensively overlaps it. 

 Thus, in the latest Jurassic, lower Cretaceous, and upper Cretaceous of 



*Griesbach: Memoirs G. S. I. xxin, p. 81. 



95 



