CHAPTER XIV. 



SUB-RECENT AND RECENT DEPOSITS. 



(i) Sub-recent : Old River terraces. 



The remains of deposits that can truly be described as sub- 

 recent, that is to say, accumulated under con- 

 Mode of occurrence. . ... _ . . , 



ditions similar to those now in existence, but 



actually undergoing denudation, are not of great extent in the 

 Shan hills. The few ancient river terraces that occur are only to 

 be met with in the valleys of those rivers that traverse the rocks 

 older than the Plateau Limestone, in the northern portion of the 

 States, for the limestone is so readily soluble that it is quite an 

 uncommon occurrence to find even a talus of fragments of this 

 rock at the foot of a scarp ; and pebble beaches in the streams 

 that flow over it are practically non-existent. 



Of the old river terraces that do exist the most important are 

 the ruby gravels of the Mogok valley and the 



Mogok valley. „ , ,. 



surrounding district ; the tourmaline gravels 

 in the Mong Long sub-State ; and the terraces in the valley of the 

 Nam-Tu. All these deposits have been already described in vari- 

 ous papers. The alluvial gravels of Mogok have been dealt with 

 by Prof. Judd and Mr. Barrington Brown in their work on the 

 Rubies of Burma. 1 Two stages of alluvium are mentioned, the 

 one a recent deposit forming the floor of the valley, and the other 

 an old river gravel deposited at a higher elevation with its base 

 on a level with, or slightly above, the surface of the present 

 „ , , , , . alluvium. There is some reason to suppose 



Old lake basin. _ _ _ . . . ** 



that a good deal of the alluvial flats, 

 which are now being excavated and washed for rubies, belong 

 to a condition of things that has now passed away, and must there- 

 fore be considered as sub-recent ; for during the process of washing 

 the gravel for gems considerable numbers of stone implements and 

 of bronze fish-hooks, the latter probably of Chinese manufacture, 

 are obtained in places well removed from the actual river coi rse, 

 and in the lower part of the deposit which contains the rubies. 



1 Phil. Trans. Roy. "oc, London, Vol. 187A, p. 164, 



