YENANGYOUNG. 115 



stage began, because there is no indication of the intersecting folds 

 in these beds, although it seems certain that they were deposited on 

 very uneven ground. 



The theory may be accepted or not, but I contend that it ex- 

 plains a number of very peculiar stratigraphical features in an un- 

 strained manner, for which it would be difficult to account in any 

 other way. I wish however to say that I do not want to generalize ; 

 the folds have hitherto been only observed within the limits of the 

 Yenangyoung oilfield, but it is quite probable that they may also 

 occur elsewhere. 



D. — General conclusions, and future prospects of the Yenang- 

 young oilfield. 



The numerous deep borings have shed so much light on the 

 extension of the Yenangyoung oilfield, that we are now in a 

 position to state with comparative accuracy that the Yenang- 

 young oilfield is of very limited extension, hardly exceeding 350 

 acres in superficial area. 



With regard to the vertical extension we are in a less definite 

 position ; we know that up to a depth of nearly a thousand feet a 

 series of sandy beds occur which may be petroliferous or not. 

 Whether the lower boundary of the oil bearing series has been 

 reached or not is impossible to say at present. Only an actual 

 test will decide this question, but for the present it seems to be 

 proved beyond doubt that it is the third oil sand, met with at 

 depths averaging from 200 to 250 feet from the surface up to 

 about 300 to 350 feet, which chiefly supplies the present yield. 

 As already stated, it is impossible to say whether richer sands may 

 exist at greater depths or not, and we have therefore only to deal 

 with those parts of the oil bearing series of which we know some- 

 thing definite. We know therefore as well as has been ascertained 

 for the present, that up to a depth of about 900 to 1,000 feet only 

 one bed of sandstone has been found capable of producing oil in 

 quantities. It is from this bed that the bulk of the pit wells and 

 nearly all the drilled wells draw their oil. It is safe to say that 

 12 ( 161 ) 



