Speight. — Occurrence of Petroleum in New Zealand. 355 



Art. XXXVIII. — Note on the Occurrence of Petroleum in New Zealand. 

 By R. Speight, M.A., M.Sc, F.G.S. 



[Read before the Philosophical Institute of Canterbury, 2nd December, 1914.] 



The question of the origin of the petroleum known to occur in New Zealand 

 has a scientific interest apart from its economic importance, but, unfor- 

 tunately, the first is almost entirely dependent on the results which are 

 furnished by attempts to prove the capacity of the fields commercially, 

 and therefore, till a mass of evidence has accumulated as the result of boring 

 operations, conclusions as to its origin must be largely of a tentative nature 



In the following parts of New Zealand indications of the presence oi 

 petroleum certainly exist : (1) Taranaki ; (2) Gisborne and the East Coast 

 in the neighbourhood of Poverty Bay ; (3) east coast of Wellington, between 

 the Tararua Banges and the sea ; (4) in the valley of the Grey River, 

 especially near Kotuku. 



There are, in addition, other places of minor importance, such as the 

 Clarence Valley and Cheviot, which have given indications of less positive 

 nature. It must be clearly understood that, except, perhaps, in the first of the 

 above-mentioned districts, the present prospects of the oil industry are doubt- 

 ful; but the difficulties may eventually be obviated, and the actual result may 

 prove more satisfactory than the present state of affairs perhaps indicates. 

 Some of the difficulties are no doubt connected with drilling rather than the 

 absence of oil in commercial quantities. 



In all the districts cited the prevailing beds associated with the occur- 

 rence of oil consist of marine mudstones, marls, sands more or less coherent, 

 with shell beds, all. of Miocene or Mio-Pliocene age. The predominating 

 strata are, however, mudstones and marls, locally known as " papa," and 

 it is only where these exist in great thickness or continuity that the indica- 

 tions are strong. 



The most important problem to be considered is whether these beds 

 are the actual place of origin of the petroleum, or whether it is derived from 

 a more deep-seated source and has migrated to the overlying beds along 

 various lines of weakness or dislocation. A correct answer to this question 

 would prove of the highest value in framing estimates for the adequate 

 exploration of the petroleum-bearing areas. I therefore give the following 

 brief summary of the position in accordance with the evidence now available ; 

 and it will be more convenient to refer first to the Taranaki area, since it 

 is the best known and, according to present evidence, the most promising. 



The strata which cover the greater part of the Province of Taranaki 

 consist of the typical Miocene rocks of the North Island — viz., mudstones, 

 sandstones, shell beds, and occasional bands of conglomerate which dip west 

 and south-west at low angles in the neighbourhood of New Plymouth, but 

 when followed towards the lower course of the Waitotara River change 

 their direction of dip to the south-east, the line of strike turning approxi- 

 mately through a right angle. The thickness of these beds certainly exceeds 

 4,000 ft., as is disclosed by the bores at New Plymouth, and may be much 

 greater, and they are apparently little disturbed by dislocations or other 



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