126 noetling: petroleum in burma. 



Section 2. — Geological Features. 



A. The pliocene or Irawadi series. 

 The lithological characters of the Irawadi series differ in no 

 way from those mentioned in previous chapters. We notice soft 

 whitish or yellowish sandstones, sometimes with strings of hard 

 concretions and ferruginous conglomerates. I have not found 

 any fossil remains on the eastern side of the Tangyi-range, but ac- 

 cording to Dr. Oldham's statements, vertebrate fossils are not uncom- 

 mon on its western side in the valley of the Yaw river. Within the 

 area of the Yenangyat oil field I have not attempted to subdivide the 

 Irawadi series, but I think it is quite possible that a subdivision 

 similar to that of Yenangyoung will be feasible when fossils have 

 been systematically collected in the Yaw valley. 



B. The Miocene. 



(a) The upper miocene or Yenangyoung stage. 



Lithological characters. — Although in general the same, the 

 Yenangyoung stage as developed near Yenangyat differs in the pre- 

 ponderance of argillaceous beds, while the more sandy beds are sub- 

 ordinate. 



The clay is generally of olive green colour, but bluish beds are 

 not unfrequent, and in fact the bed which closes the series has a dark 

 bluish colour. The usual hard concretions in strings or uninterrupt- 

 ed layers are found throughout the series. They form sometimes 

 the top of a hill, the overlaying clay being denuded away. 



The sandstones are yellowish or olive coloured, finely grained, 

 generally soft, but sometimes they form hard layers. 



Gypsum is very common in all the argillaceous beds. 



Paloeontological characters. — There was apparently an inver- 

 tebrate fauna living during the deposit of the above beds, as indi- 

 cated by numerous fragments of shells. I have, however, never 

 succeeded in finding complete specimens, but some of the fragments 

 apparently belonged to the genus Cardium, while others probably 

 represent the genus Cyrena. 



( 172 ) 



