48 



LA TOUCHE : GEOLOGY OF NORTHERN SHAN STATES. 



or argillaceous, and lime is not present in any form : this is the 



more remarkable, since all the succeeding formations are, to a 



greater or less extent, of a calcareous nature. 



Except in the beds of the streams, and along the cuttings of the 



new roads that have been made through the 

 Paucity of outcrops. .... , , ° 



hills, outcrops of the rocks are not often 

 met with, owing to the thickness of the ' cover ' of clay and soil 

 in which the hill slopes are buried, and, moreover, they are so 

 thickly clothed with vegetation that landslips very seldom occur. 

 For this reason anything like a continuous section is not to be 

 seen, so that it has been found impossible to trace the different 

 varieties of rock from one locality to another. The strike of 

 the beds also is by no means constant ; for though it sometimes 

 remains the same for considerable distances, it is subject to abrupt 

 changes in direction, and this adds to the difficulty of following 

 out any particular band of rock. The strata are also greatly 

 dislocated by faults, which for the same reasons cannot be fol- 

 lowed up continuously for any distance, and these add greatly 

 to the complexity of the structure. It would, of course, be pos- 

 sible to work out the stratigraphy in much greater detail than 

 has been done, in spite of the scarcity of outcrops and other diffi- 

 culties, but it would entail an enormous amount of labour, and 

 since the series possess very little economic value, there would 

 be no object in spending time and labour upon it. 



Another circumstance that enhances the difficulty of dealing 



with the relations of the different beds of 

 Mode of weathering. . . . , .-, , . 



this series to each other and to the over- 

 lying formations is their mode of weathering. Wherever they 

 have been exposed to the atmosphere for any length of time 

 they become rotten and decomposed, and are not easily to be 

 distinguished from ordinary sandstones and shales, such as are 

 common among the succeeding formations. 

 Indications of altera- j fregh outcrops however, either in the 



tion. . 



streams or road cuttings, it is often possible 

 to discover some signs of alteration in the older rocks. The 

 quartzites, under the microscope, exhibit in some specimens a 

 secondary growth of the quartz grains, filling up the interstices 

 between them ; and the slates are usually spotted with minute 

 stains of iron oxide, probably resulting from the decomposition of 

 granules of iron pyrites, drawn out in the direction of the shear 



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