UPPER AND LOWER MIOCENE, 35 



the Magyi Chaung, in block 2 of the Yenangyat oilfield, where a small 

 patch of Prome sandstone can also be seen, and besides this there are 

 more exposures in the stream-beds amongst the hills to the north of 

 the demarcated blocks. From these exposures alone we should not 

 learn much of the Prome beds in this part of the country, but for- 

 tunately our knowledge is somewhat supplemented by information 

 obtained from wells and borings, and even then it is very imperfect. 

 From the evidence we have, we see that the lower miocene (Prome) 

 beds consist of interstratified layers of shale and sandstone, the shales 

 predominating. 



Where the boundary between upper and lower miocene should 

 be placed is not very definite, as the beds in the two stages are 

 in many ways similar in character, and they are apparently con- 

 formable to one another. The difficulty in fixing the boundary is 

 also increased by the smallness of the exposures of Prome beds, and 

 by the way in which these exposures are obscured and covered 

 up by loose material. In the Singu and Tangyi hills I have, as 

 Dr. Noetling did, taken the junction as just on the top of the first 

 oil sand, as the Prome beds below differ from the Yenangyaung 

 beds above, in the different colour of their sandstones and in 

 places of their shales and in the absence of gypsum in the shales. 

 The Prome sandstones are massive, fine-grained and greyish in 

 colour, many of them are glauconitic, and then their colour is some- 

 what greenish ; the uppermost sandstone is in some places bluish- 

 grey. The shales are soft, and bluish-grey to black in colour, and 

 they may be distinguished from the Yenangyaung shales in not 

 containing any gypsum. Between the shales and the sandstones 

 there is every gradation of shaly sandstones and sandy shales besides 

 beds composed of alternate thin layers of shale and sandstone. 

 Of the total thickness of the Prome beds in these parts, there is 

 no evidence, only the uppermost beds being exposed, and although 

 over eight hundred feet have been bored through, the base has no- 

 where been reached. 



D 2 ( 35 ) 



