34 NOETLING : PETROLEUM IN BURMA. 



and it will be sufficient to say that the composition of the fauna is 

 somewhat different from that of Singu and Yenangyat, and that it 

 holds most probably an intermediate position between those two 

 faunas. 



3.— Stratigraphical features. 



Any section from the river bank towards west at once demon- 

 strates that the strata form a rather high, but unsymmetrical, anticlinal 

 arch, the sides of which are formed by the beds of the Irawadi 

 series, while in its centre the Pegu series is exposed. 



Along the river bank the beds dip vertically, and in some places 

 are even reversed ; the vertical dip continues along a distance of 

 approximately 1,000 feet to the west from the river bank, that is to 

 say, the hill range running immediately along the river bank is 

 throughout composed of the steeply inclined beds of the Yenang- 

 young stage and Irawadi series. Towards west the dip gradually 

 lessens, and within a distance of about 600 feet from the western foot 

 of the hill range the strata dip at an angle of about 15 towards east. 

 Unfortunately the gradual change in the inclination of the beds can- 

 not be observed because a valley filled with debris intervenes. The 

 dip lessens gradually till finally the beds are seen to be perfectly 

 horizontal in the low ridge closing the valley in which the mud 

 volcanoes are situated towards north ; from this point the strata dip 

 rather quickly toward west, but the angle of about 12° to 15 is very 

 constant and does not increase as far as I have traced them towards 

 west. 



Judging from this structure, the strata form here a true fold, 

 on the top of which the mud volcanoes and natural oil springs are 

 situated. I am unable to say how far south this anticlinal arch 

 extends ; towards north it seems to come to an end within a few 

 miles of Minbu, where the alluvial plain of the Mon river butts 

 immediately on the tertiary rocks; but I am unable to say whether the 

 latter dip normally below the alluvial deposits, or whether a cross 

 fault has cut off the anticlinal. 



( 80 ) 



