GEOLOeT OF NEW ZEALAND. 217 



perhaps be placed here. Xo trace of a scoria-cone uor of a tuff-crater 

 exists anywhere in the South Island ; all the volcanic rocks, even 

 Banks's Peninsula, which is 3000 feet high, appear to have suflFered 

 from marine denudation. 



In the North Island volcanic ash beds and andesitic breccias are 

 found associated with the Waitemata Series near Auckland ; and the 

 trachytes (?) of Whangarei, the Great Barrier Island, and Coro- 

 mandel are no doubt of the same age. Eossil wood of Podocarpium 

 dacrydioides, TJ-ng., was obtained by Dr. Hochstetter from the tra- 

 chyte tuffs of both the Great Barrier and Coromandel ; and from the 

 much decomposed basaltic rocks behind Drury he obtained wood of 

 Nicolia zelandica, Ung., which Avas also found in the Pareora gravels 

 of Moutere Hills near JSTelson. On the Great Barrier Island the 

 trachytic cone of Ahumata, 1500 feet high, still retains a well-marked 

 tuff crater *, as also does Arid Island t. 



The andesites J, and gold-bearing propylites (?) of the Thames may 

 be of the same age, or they may possibly date back to the Oamarii 

 System ; but we have no evidence that any andesites in ]N"ew Zealand 

 are older than the Oamaru System §. A piece of carbonized wood 

 impregnated with iron pyrites, but showing plainly annual rings of 

 growth, was obtained from the gold-bearing propylites in the " Maid 

 of England" claim ||. 



Wanganui System. — There is no trace of volcanic action having 

 taken place in the South Island during this period or later ; but in 

 the North Island, on the western side of the main range, volcanic 

 eruptions on a large scale occurred from the commencement of the 

 Pareora and are even now not quite over. At Mt. Egmont in 

 Taranaki the first eruptions, perhaps of Pareora date, were trachytes 

 containing (according to Zirkel) both sanidine and oligoclase, and 

 are much like some of the rocks of Banks's Peninsula. These were 

 succeeded by dolerites and basalts. The bases of Ruapehu and of 

 Tongariro also appear to consist of trachytes, but here the later 

 eruptions have been dark-coloured rhyolites and pumice. These 

 siliceous eruptions appear to have commenced during the formation 

 of the upper part of the Wanganui System (Kereru Series), for no 

 pumice occurs in the lower beds. Khyolites are extensively developed 

 round Lake Taupo, and in the Hot-spring district. In the vaUey 

 of the Thames it appears that they are of later date than the 

 dolerites (? angite-andesites) of Cape ColviUe peninsula %. Around 

 Auckland and at the Bay of Islands basalts were the only lavas 

 erupted. 



^ Eep. Geol. Surv. 1868-69, p. 6. 



t Trans. N. Z. Inst. i. p. 164, new ed. p. 108. 



\ I am indebted to Prof. Ubich for the information that .the rocks called by 

 me dolerites. in Eep. Geol. Surv. 1863-69, p. 20, are typical augite-andesites 

 According to Dr. Hector they contain olivine (Geol, Eep. 1868-69, p. 42, no. ix.); 

 I saw none myself. 



§ See " On the Geological Structure of the Thames Goldfields," in Trans. 

 N. Z. Inst. yi. p. 272 ; and Cox, Eep. Geol. Surv. 1882, p 4. 



II Eep. Geol. Surv. 1868-69, p. 44. 

 «[ Cox, Eep. Geol. Surv. 1883, p. 20. 



