98 Transactions. 



scarp can be of no great height, and the higher facets, like those in the 

 Upper Kaiwarra and Silver Stream Valleys, probably form part of a fault- 

 line scarp. 



The Old Fault-line." 



It is possible that the old line of fracture, the extent of which has been 

 indicated in these notes, represents, in the Wellington area, the Kaikoura 

 orogenic movement,* which was accompanied in Marlborough by the for- 

 mation of enormous reversed faults. This view gains some support from 

 the fact that the numerous planes of movement of this old distributed 

 fault at the head of the Tinakori Stream dip north-west, whereas the 

 Wellington fault-scarp faces the south-east. 



It is not, however, advisable to attempt a correlation with any par- 

 ticular fracture in the South Island. f 



Art. XLII. — Note on the Andesites of White Island. 



By B, Speight, M.Sc, F.G.S. 



[Bead before the Philosophical Institute of Canterbury, 3rd December, 1913.] 



When Mr. W. E. B. Oliver visited White Island in December, 1912, in 

 order to examine the ecological conditions of its vegetation, he collected 

 specimens of rocks from various points, and kindly handed them over to 

 the Canterbury Museum. The collection includes specimens of sulphur 

 and crystals of gypsum ; but more interesting from the geological stand- 

 point are the volcanic rocks. The only published description of igneous 

 material from this locality is that by W. A. MacLeod, in a paper entitled 

 " Note on a Hypersthene Andesite from White Island. "J In this he 

 describes a solitary specimen, giving its macroscopic and microscopic cha- 

 racters, and also a chemical analysis of the rock. The collection made 

 by Oliver appears to be fairly complete, and includes variations from 

 MacLeod's rock. I have therefore furnished a few additional notes on 

 the character of the lavas of this interesting island. 



It has been pointed out by various authors that the island lies on a 

 broken line of volcanic vents stretching from Euapehu in a north-easterly 

 direction across the Pacific, and including Mounts Tauhara, Edgecumbe, 

 the Kermadec Islands, and various centres of activity near the Tonga 

 Group. Marshall would terminate the line with this group, § but if this 

 line be continued it will pass through the Samoan and Sandwich Island 

 volcanic lines at the point of their present maximum intensity. This may 

 be only a coincidence, but, if so, it is a somewhat striking one. It points 

 rather to the intersection of a line of crustal weakness running north-east 

 with two others running north-west by west (see Dana, " Characteristics of 



* C. A. Cotton, Geogr. Journal, vol. 42 (1913), p. 227. 



fSee, however, A. McKay, Geol. Surv. of N.Z., Reports 1890-91 (1892), p. 19. 



% Trans. N.Z. Inst., vol. 31, 1899, p. 488. 



§ Report Trans. Aust. Assoc. Adv. Sci., 1909, p. 446. 



