304 LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



Thickness. 



The whole series is distinguished by its colour, which is gen- 

 erally a dark rod, often with a decided 

 i Lithological charac- purplish tinge ; but beds of grey, pepper and 

 salt sandstones, and bands of yellow clay are 

 sometimes interstratified, especially in the higher parts of the series. 

 ,,, ,, . The sandstones rule, soft and friable, 



Weathering. ' 



and are only occasionally hard enough to be used 

 as building stone ; consequently the areas composed of these rocks 

 are readily affected by denudation, and invariably consist of an 

 intricate network of ridges and ravines with no marked uniformity 

 in direction, the whole covered with dense forest, and almost 

 trackless ; the inhabitants being few and their villages and patches 

 of cultivation only met with at long intervals. 

 Nothing definite can be said about the thick- 

 ness of the formation, for the absence of continuous sections and 

 of an upper limit, coupled with the intense disturbance of the beds, 

 the prevalence of faults, and the enormous amount of denudation 

 that the series has undergone, make it impossible to give even an 

 approximate estimate, but it must amount to several thousand feet. 

 In the earlier stages of this epoch bands of limestone were 

 , formed at intervals, none of them more than 



Limestone bands. . , . . , . . 



a tew teet thick, but very uniform m thick- 

 ness and often persistent for several miles. They were perhaps accumu- 

 lated at times when, for one reason or another, the supply of 

 sandy or muddy sediment was cut off, and their absence from the 

 upper portion of the series is an indication of the setting in of 

 more uniform conditions as time went on. They are usually homo- 

 geneous in texture, very compact and fine-grained, but often 

 argillaceous and abounding in fossils, passing into shelly limestones. 

 Being easily weathered these bands form no conspicuous feature on 

 the surface, and owing to the density of the forest they can only 

 be traced at intervals, in the stream beds and on the paths, and the 

 course of those shown on the map is therefore partly conjectural ; but 

 they indicate very clearly the direction of the prevailing strike of the 

 formation, from N.N.E. to S.S.W., and the profound disturbance 

 that the rocks have undergone, for they generally dip at high 

 angles and are often vertical. 



It is evident that this formation must have once covered a 

 very much wider area than it dot's at present, 



Distribution. , * . , , , , , . 



but it has sunered so greatly from denudation 



