134 NOETLING: PETROLEUM IN BURMA. 



In going through the records the first feature noted is the 

 predominance of argillaceous beds ; in fact if we look at the sections 

 on pi. XVII it seems that the sequence consists of an enormous argil- 

 laceous series, here and there parted by thin beds of sandstone. The 

 predominance of the argillaceous beds in greater depth is therefore 

 quite in accordance with the character observed in the series super- 

 ficially exposed. 



It will be seen further, that the thickness of the various beds is 

 somewhat inconstant, a fact which has been mentioned already 

 (pp. 79 ff.). Although there seems to be a greater regularity in the 

 horizontal extension of the strata than may be observed at Yenan- 

 gyoung, it is certain, that a bed may locally attain a great thickness 

 whilst rapidly thinning out in other directions. On the other hand, 

 we may safely assume that certain beds observed in the bores, are of 

 very limited extent. 



The first oil sand affords the best instance of the first case ; it rapidly 

 increases in thickness from well No. 5, towards No. 3, while it 

 equally rapidly decreases from No. 1, towards No. 2. 



As an instance of the second supposition, the two sandy layers 

 found in wells Nos. 1, 2, and 3 between the first and second oil sands 

 may be quoted. It is absolutely certain that these two beds have not 

 been found in No. 5, where an uninterrupted bed of clay separates the 

 first and second oil sand. We are therefore bound to suppose that 

 they thin towards west. These instances could be easily increased 

 in number ; it seems for instance quite certain, that the two thick beds 

 of clay, which apparently divide the third oil sand in No. 5, nip out 

 to the west and are replaced by sandy beds> thus forming a thick 

 arenaceous layer which represents the third oil sand in well 

 No. 6. 



It is a plausible supposition, that when such changes take place 

 in a transverse direction, they would equally probably be met with in 

 a longitudinal direction. The chief beds of the Yenangyoung stage, 

 as superficially exposed, seem to be opposed to such a view, as they 

 are apparently very constant, but it does not necessarily follow that 

 the same applies to the petroliferous beds. However this question 

 , ( 180 ) 



