GEOLOGY OF NORTHERN SHAN STATES AND YUNNAN 21 1 



As shown, this broad band of limestone continues into Yunnan 

 and is thus directly correlated with the Devonian and Permo- 

 Carboniferous limestone of that province. 



JURASSIC (nam YAU BEDS) 



At one point in approximate latitude 23° 47' longitude 98° 15' 

 on the flanks of the dome-shaped anticline in which the older 

 sediments are exposed, beds of coarse conglomerates, with the 

 pebbles largely of limestone, were noted. A short distance from 

 this point extensive beds of red sandstone were encountered lying 

 above the Plateau limestone. Their position and character are 

 fairly strong evidence in assigning them to the Nam Yau, but the 

 scant opportunity for examining them makes their definite determi- 

 nation unadvisable. This is especially true as they also resemble 

 the Red Bed series of Yunnan (Permian-Triassic) , as described by 

 Coggin Brown, and may possibly represent a southern outlier of 

 those beds. 



No Jurassic beds have as yet been identified in Yunnan. 



TERTIARY 



Fairly extensive deposits of Tertiary beds are present in the 

 Nam Tu valley, but they were not noted elsewhere, although it 

 is possible that small remnants are present in some of the other 

 valleys in the Plateau limestone. They are found as unconsoli- 

 dated sands and clays and often contain extensive deposits of lignite 

 and sub-bituminous coal. 



RECENT 



All the more prominent river valleys are covered with deposits 

 of recent alluvium, probably with the exception of the Shweli 

 valley in the Namhkam area, always of fluviatile origin. In the 

 case of the Shweli valley the broad plain about thirty miles long, 

 with an average width of five or six miles, probably represents an 

 old lake bed similar to the numerous ones which have been noted 

 in Yunnan. Recent elevation with consequent renewed erosion 

 by the Shweli has largely concealed its former character. 



It has not been attempted to show these deposits on the accom- 

 panying map, as it only tends to confuse the relations of the under- 

 lying consolidated formations. 



