88 Transactions. 



important change must be made in the age of the Thames 

 andesites, which rest on rocks that have hitherto been classed as 

 Cretaceo-tertiary. They must be accepted as of Upper Miocene 

 age at the earliest. 



Hill's observations prove the Miocene age of some acid 

 eruptions, probably that of the interior region near Taupo ; 

 so it appears that volcanic action commenced in the Thames 

 and Taupo regions almost simultaneously towards the end of 

 the Miocene period. 



At Auckland, Fox has shown that the scoria-beds in the 

 Waitemata series are of the same nature as the Waitakerei 

 rocks, and, as the Waitemata beds are Upper Miocene, there 

 can be no doubt that the great series of Waitakerei andesites 

 are of Upper Miocene age. The main features of the Waitakerei 

 rocks, stratigraphical, petrographical, and physiographical, are 

 repeated at many points further north, notably at Kamiti, 

 Kaipara Harbour ; Manaia Peaks, Whangarei ; the entrance to 

 Hokianga ; St. Paul, aud the surrounding district, Whangaroa : 

 south of Mangonui ; North Cape district. It therefore seems 

 reasonable to refer all these areas to eruptions of Upper Miocene 

 age. In making this correlation, it must be remembered that 

 the rocks have most striking characteristics in common, and 

 that in several cases actual stratigraphical evidence that war- 

 rants such a correlation is to be found. • 



There is little evidence as to the age of the rocks of Karioi 

 and Pirongia. Stratigraphically they rest upon Miocene lime- 

 stones, and are possibly of late Miocene age. The rocks are 

 dolerites, and differ markedly from all other volcanic material 

 of the North Island, so far as my experience goes. 



Another group of rocks about which there is at present 

 but little information is that of the older basalts between Kerikeri 

 and Orotere, and, further on, between Mangonui and Ahipara. 

 I know of no stratigraphical evidence as to their age, and they 

 are here termed " older " merety because of the mineralogies! 

 changes of serpentinisation that they have undergone, and 

 because of the extensive weathering changes by which their 

 surface has been altered. At Kerikeri they rest on Miocene 

 rocks. 



There appear, then, good evidences of great volcanic activity 

 towards the close of the Miocene; but this activity was more 

 pronounced in the northern part of the district than in the 

 southern, for in all the extensive Miocene rocks near Wanganui 

 there are no pumice or fragments of volcanic rock to be found, 

 even in the upper rocks of the series. That this period of 

 activity extended into the Pliocene is possible, though, owing 

 to the general absence of Pliocene deposits, there is no absolute 



