CHAPTEE XIII. 



TERTIARY. 



Freshwater Beds. 



With the deposition of the red sandstone series the long suc- 

 cession of marine formations which we have 

 ^ Close of marine depod- pasged k reyieW) extending from lower Or- 



dovician times to the Jurassic period, comes 

 to an end. No trace of the marine Cretaceous or of the Eocene, 

 Oligocene, and Miocene formations which are so well developed 

 and widespread in the plains of Lower and Upper Burma has 

 been found on the uplands, and it is evident that, when the 

 Tertiary sea extended over what is now the valley of the Irra- 

 waddy, the Shan plateau had already been raised above its 

 waters. But the upheaval that resulted in this total cessation 

 of deposition was merely a local development of events that 

 affected a very large portion of the earth's surface at this 

 period. For a long time before this, signs had not been wanting 

 that the ancient Gondwana continent was being broken up. On 

 the west coast of India the Jurassic sea had penetrated nearlv 

 as far to the south as the latitude of Bombay ; and on the east 

 the Bay of Bengal, which must have appeared as a depression in 

 the old continent at an even earlier date, for Triassic rocks aro 

 known to occur on its shores in the Arakan Yoma, had extended 

 its waters in the Cretaceous period as far to the north as the 

 borders of Assam. The elevation of the Shan plateau is then but 

 a local manifestation of the great orogenic movements that ad- 

 vanced upon the Peninsula of India from three different directions ; 

 resulting on the west in the upheaval of the Suleiman ranges, 

 on the north in that of the Himalaya, and on the east in that 

 of the Assam and Arakan ranges. From this time on, therefore, 

 the history of the area we are dealing with is one of degradation 

 and modification of the superficial features ; and it was not until 

 the present configuration of hill and valley had been blocked out 

 that the deposition, at any rate of beds that have endured to the 

 present day, again set in. 



The rocks which have been ascribed to the Tertiary period in 

 j . j h r , t these hills consist of silts and soft sand-rock, 

 -so slightly consolidated that they break down 

 into a soft mud when immersed in water, — pebble and boulder 



