216 



CAPT. F. W. HUTIOIS^ OJT THE 



occurs, whicli, while agreeing well in ultimate analysis with specimens 

 obtained in other countries, does not contain any palagonite visible 

 to the naked eye. 



The andesites and trachytes forming the centre of the Dunedin 

 volcanic system are interbedded in the peninsula with sedimentary 

 rocks, probably of this age ; but the later eruptions of basaltic rocks 

 which surround the andesites may belong to the Pareora System*. 



According to Dr. von Haast, the results of whose extensive re- 

 searches on the structure of Banks's Peninsulaf I can in great part 

 confirm, there have been here, in addition to the quartz-rhy elites of the 

 Waipara System already mentioned, three periods of activity. To the 

 first of these belong the caldera of Lyttelton, Little Eiver, and Akarda, 

 in which the lava-flows are chiefly augite- andesites J and occasionally 

 trachytes. The dykes are chiefly trachytes, but occasionally augite- 

 andesites, and at least one is rhy elite §. To the second period belong 

 !Mt. Herbert and Mt. Sinclair, which are formed of andesites, but 

 without any visible dykes. To the third period belongs only Quail 

 Island in Lyttelton Harbour, also composed of andesites with dykes 

 of trachyte (?). The first and second of these periods of eruption 

 are quite evident, and both appear to have been entirely subaerial 

 in character. There does not, however, seem to be any means of 

 distinguishing the third from the second period, and it is compara- 

 tively insignificant. The quartz-rhy elites had suffered severely 

 from denudation, and thick beds of sandstone had been formed by 

 their disintegration, before the more basic eruptions took place ; 

 consequently we may consider these latter as younger than the 

 Waipara System. On the other hand the whole have suffered too 

 much from denudation to allow us to put anj^ of them later than 

 the Pareora System ; and as both periods of eruption were subaerial, 

 we have the interval between the Waipara and Oamaru Systems or 

 that between the Oamaru and Pareora Systems to choose between. 

 I think it probable that the calderas of Lyttelton and Akaroa belong 

 to the Oamaru System, but Mt. Herbert may belong to the Pareora 

 System. 



In the J^orth Island the trachytes (?) of Hick's Bay, near the 

 East Cape, are distinctly overlain by beds of the Tawhiti Series ||, 

 and they may therefore belong to the Oamaru System. 



Pareora System. — In the South Island basalts and basaltic tuffs 

 are interbedded with rocks of this system at Mt. Cookson, north of 

 the Hurimii plains. The basalts of Moeraki Peninsula are clearly 

 seen to overlie a Pareora clay (the Onekakara clay of ManteU ^), 

 and as they have undergone great denudation, we cannot put them 

 into the Wanganui System. The volcanic rocks of Timaru may also 



* Geology of Otago, p. 55. 



t Geology of Canterbury and Westland, p. 324, and Trans. ISi. Z. Institute, 

 xi. p. 495. 



\ Por the knowledge that these rocks are andesites I am indebted to Prof. 

 G. H. F. Ulrich, who has examined them microscopically. 



§ Ulrich. II Cox, Eep. Geol. Surv. 1876-77, p. 112. 



^ Geology of Otago, p. 61. 



