358 Transactions. 



far as present knowledge allows a conclusion to be made, indications of the 

 occurrence of gas or oil are met with at horizons distributed throughout 

 the whole thickness of these beds. It is true, nevertheless, that the amounts 

 are greater at lower levels ; but this is to be expected, since the more perfect 

 cover afforded by the increased thickness of overlying strata naturally 

 reduces the chances of the escape of oil. If it has originated in situ, the only 

 possible explanation of its origin is that it is due to the distillation of the 

 animal remains. The amount of vegetable matter included in these beds 

 is small and seemingly insufficient to account for the phenomena, but a 

 large amount of marine-animal matter does indeed occur. This includes 

 remains of Foraminifera, and above all of Mollvsca, whose shells are widely 

 distributed, and at times form banks several feet in thickness. By the 

 distillation of the animal matter they formerly were associated with, suffi- 

 cient hydrocarbon would be furnished to account for the oil in the strata, 

 and their wide distribution at various levels would account for the occur- 

 rence of oil through great depth. In this connection it may be noted that the 

 oyster-beds associated with the coal-measures in other parts of New Zealand 

 frequently give out a strong smell of petroleum when freshly broken. A 

 reference has been made previously to the existence of beds of carbonaceous 

 shale, which are interstratified in the papa rocks, but the origin of the car- 

 bonaceous matter is at present unknown. When analysed these show the 

 presence of oil, and they furnish absolute proof that it does exist in situ 

 in the Miocene beds. 



The sandstone layers which are interstratified with the mudstones of 

 this series would undoubtedly be suitable for the storage of the oil, and 

 thick covering mudstones would favour its retention; but the structure of 

 the country, as far as is known at present, hardly favours its concentration. 



As regards the existence of a deep-seated source, it must be admitted 

 that there is no direct evidence at present available from Taranaki. The 

 most suggestive fact is that the surface indications and the flow of oil are 

 specially strong in the immediate neighbourhood of the intrusive rocks 

 near Moturoa. This may be explained by supposing that leaks have occurred 

 up the surface of contact of these masses and the beds into which they 

 have been intruded, and that the disruptions which would occur when the 

 volcanic rocks were being forced into the surrounding sedimentaries would 

 afford a relatively easy path for leakage through them from lower levels. 

 There appears to be a close parallel between this occurrence and the 

 sensational wells of the East Mexico field in everything but volume 

 of flow. 



Further, in the valley of the Waitotara River, along a line of fault, the 

 surrounding clays are impregnated with hydrocarbons, and smell strongly 

 of petroleum. This is certainly due to a leak, but whether it is a leak from 

 a lower level in the Miocene beds or to a leak from a still lower horizon 

 it is impossible to say. The strongest evidence of the deep-seated origin 

 of the^oil is, however, obtainedTfrom other localities. 



In referring to the Kotuku district of the Grey Valley, Morgan says* that 

 the Cobden limestone underlying the marls of that locality is charged with 

 oil ; unfortunately, nothing certain is known of its origin in that region, but 

 the evidence undoubtedly points to a source below the limestone, and the 

 impregnations of the overlying clays are due to upward migrations. 



* Bulletin No.US^new series), N.Z. Geol. Surv., p. 143. 



