356 Transactions. 



deformations ; but owing to the infrequency of good sections this statement 

 is subject to revision ; in one or two' places undoubted faults of small throw 

 are existent. Rising through these sediments and covering them over 

 considerable areas are the volcanics from Mount Egmont and numerous 

 small parasitic cones round the base of the mountain, as well as the igneous 

 masses of the Kaitaki and Pouakai Ranges. The age of these mountains 

 must be considerably greater than the cone of Egmont, but there is no strong 

 evidence that they are of pre-Miocene age, although that is extremely pro- 

 bable. A notable constituent of the sandstone beds intcrstratified with the 

 mudstones and marls of this age are fragments of hornblende crystals similar 

 to the mineral occurring in the Taranaki volcanics. These would seem 

 to indicate that a considerable area of igneous rocks was existent in the 

 neighbourhood while the petroleum-bearing beds were being laid down. 

 This fact mav have some bearing on the date of the intrusive rocks at 

 Moturoa, but, owing to the obscuring of the contacts between these and the 

 intruded rock by the overburden of fragmentary volcanic matter, no con- 

 clusion can be come to at present ; all the same, it is remarkable that bores 

 co aid have been put down to 4,000 ft. within but a short distance of these 

 masses. It seems, therefore, reasonable to suppose that they were intrusive 

 into the Miocene rocks as well as into the pre-existing masses. 



The interstratification of sand with close impervious beds of mudsione 

 and marl would undoubtedly furnish satisfactory conditions for the storage 

 of hydrocarbons were they int oduced into the beds, but they do not furnish 

 prospects for great concentration. If the field proves satisfactory it will 

 have the* character of one which will produce steady yields rather than 

 sensational returns for- a short period. 



The evidence for the presence of petroleum, apart from the actual vicinity 

 of Moturoa, where flowing wells occur, is based on the following :— 



(I.) The existence of slight seepages of oil in various places remote from 

 New Plymouth, and distributed over an area stretching from the sea near 

 Waitara to the Waitotara River. 



(2.) The existence of gas emanations over the same area, including 

 those recorded by Clarke.* Outside the area, therein referred to, they are 

 widely distributed, the most important occurrences being near Inglewood, 

 at Huiroa, in the Mangaone Valley, in the Waitara River. Such gas dis- 

 charges are known to occur as far to the east as Whangamomona. 



(3.) Beds of oil-bearing shale of lenticular shape, but not extensive 

 in area, occur in several places, interstratified in the papa rocks. 



(4.) In addition, there are sulphuretted-hydrogen and saline springs in 

 various places, these not being in themselves evidence of the occurrence 

 of petroleum, but are frequently associated with it. 



(5.) The occurrence of mud volcanoes, which are frequently found in 

 oil regions, has been recorded from various parts of the district, but the 

 evidence on which these reports have been made is somewhat doubtful. 



These various lines of evidence show that oil is found over a fairly wide 

 area, but they do not show that it is found in sufficient quantities to be 

 commercially valuable : that can be demonstrated only by boring. The 

 original theory for the origin of Taranaki petroleum was based on the sup- 

 position that its distribution was very local, and entirely confined to the 

 neighbourhood of Moturoa ; but the evidence that it is widely distributed 

 on the coast and inland between the Waitotara and the Mokau Rivers is 



* Bulletin No. 14 (new series), N.Z. Geol. Surv., pp. 43-45. 



