806 Transactions. 



Petroleum. 



In west Nelson traces of oil are found at Karamea, Reefton, Dobson, and 

 Kotuku. At Reefton the oil occurs in connection with certain shales under- 

 lying the coal. As pointed out by Morgan and Webb,* the source of the 

 oil is undoubtedly the beds of the coal series. At Karamea and Reefton the 

 shales and claystones which carry the oil are upturned by pov/erful faults, 

 and the structure is synclinal. 



At Dobson the bore from which the oil issues penetrates the western 

 limb of the Brunner anticline. Between this bore and the crest of the 

 anticline runs a branch of the great Mount William fault, to the west of 

 which the oil will occur. At Kotuku the oil-permeated gravels lie over 

 the northern continuation of the Ross fault, and it seems feasible to siippose 

 that these supplies of petroleum are soaking up along this fault. The struc- 

 ture of the underlying coal-beds will be monoclinal. 



Summary. 



(1.) The coals of west Nelson, as first suggested by Professor Park.f 

 have accumulated as marginal (probably drift) deposits. 



(2.) The coal-measures belong to one system only, and present an un- 

 broken sequence. 



(3.) The more higlilv carbonized coals are generally the more elevated, 

 or, more exactly, those from above which the impervious strata have been 

 removed wholly or in part. This " stripping " permitted a relatively rapid 

 escape of distillation-products and a relatively rapid distillation of the 

 vegetable matter. It should be noted that Professor Parkf has long in- 

 sisted on the influence exercised by the character of the overlying measures 

 in determining the formation of different classes of coal. 



(4.) The chances of large supplies of petroleum being found in west 

 Nelson are not good. A certain amount may occur along faults. 



Art. XXXVI. — On the Genesis of the Surface Forms and Present Drainage- 

 sijstems of West Nelson. 



By J. Henderson, D.Sc, A.O.S.M. 



Communicated by Professor James Park. 



{Read before the Otago Institute, 14th Septemher, 190V.] 



The term " west Nelson " as here used includes all that part of the north- 

 west of the South Island which lies to the west of the main divide and north 

 of the Taramakau. This portion of New Zealand has an area of close on 

 8,000 square miles, and consists of a series of earth-blocks, which at one 

 time presented a comparatively even surface, but which have suffered 

 such a differential elevation that some of the blocks have been raised till 

 their surfaces are 5,000 ft. or more above the surfaces of the other blocks, 



* Morgan : Geol. Surv., 3rd Ann. Rep. (n.s.), pp. 9, 10. Webb : Idc»i, p. 23. 

 t Park : " Geology of New Zealand," 1910, p. 280 et seq. 

 t Park : " Mining Geologv," 2nd ed., 1907, p. 32. 



