60 GRIMES : MY1NGYAN, MAGWE AND PAKOKKU DISTRICTS. 



is not present at all. In the northern part of the Yenangyaung oil-field 



it is absent, but twenty-eight miles to the north in the Singu exposure 



of miocene beds there is a very considerable 



Its varying thickness 



indicates erosion-uncon- thickness of it. This varying thickness of the 



formity. . J ° 



uppermost miocene bed within a small area 

 points to an unconformity of erosion between the miocene and plio- 

 cene. The upper miocene beds and the pliocene beds overlying 

 them have approximately the same dip and strike, but owing to 

 the want of definite bedding planes it is impossible to observe this 

 accurately. 



With reference to the occurrence of petroleum in lower miocene 

 beds Dr. Noetling has shown 1 that in Burma as 



As to the possibility of ... 



occurrence of petroleum in other countries, it is only found in workable 



in lower miocene beds. , . ., , 



quantities at tn e crests of anticlinal folds and 

 where the crests are most elevated. 



In the Yenangyaung anticline we find the crest of the fold at its 

 highest level at Twingon, Khodaung and Berne and gradually sink- 

 ing both to the north and to the south, and so as the limits of the 

 workable area have been reached in the Yenangyaung oil-field 

 there is no hope of finding other workable areas along the Yenang- 

 yaung anticline at least within the limits of my survey. 



Surrounding the miocene area and resting on its strata with, as 

 we have just seen, unconformity of erosion, are the beds of the Irra- 

 waddi series, which are of pliocene age. 



In the neighbourhood of Yenangyaung, where the anticlinal arch 

 ^, , ,,.,,. riess to its greatest height, the Irrawaddi beds 



The Irrawaddi (plio- ° . 



cene) beds. have a fairly steep dip on both sides and be- 



tween the oil-field anr 1 the town of Yenangyaung Dr. Noetling has 

 measured 2 dips from 50 to 32 . Towards the north, owing to the 

 sinking of the anticlinal arch, the dips steadily decrease until in blocks 

 25N and 26N the Irrawaddi beds, where they become covered up 

 by more recent deposits, are lying almost horizontally and the dips 



1 Memoirs, G. S,, I., Vol. XXVII, Pt. 2. 



2 Memoirs, G. S., I„ Vol. XXVII, Pt. 2, Map. 

 ( 60 ) 



