PROCEEDIXGS OF SECTIOX C. 371 



The other rocks of this volcanic district are andesites (mica, augite, 

 and hypersthene varieties). They were called melaphyres by Haast, 

 though Hutton afterwards described their true nature. In a few in- 

 stances the hypersthene is replaced by enstatite. The ground mass of 

 these rocks is hyalopilitic, but the felspar microlites seldom have a 

 parallel arrangement and augite microlites are more abundant than 

 felspar in the light-brown glass. 



The period of eruption of these rocks appears to have been the 

 later Jurassic, for the tertiary rocks rest on them unconformably, and 

 the lavas have shared in the folding to which the underlying Jurassic 

 sediments have been subjected. They constitute the quartz porphyry 

 and melaphyre system of Van Haast. 



Volcanic rocks of Post-Miocene date are common on both east and 

 west coast districts. For the greater part these rocks are basalt. This 

 is the case at Mount Pleasant, in Southland. At the Haast mouth and 

 at Koiterangi, in Westland, the same is the case. Basalts are said by 

 the geological survey to occur in the Awatere and Clarence Valleys. 

 Basalts and dolerites are abundant near Palmerston and at Waihola. 

 At Timaru and Oamaru there are similar rocks, but at the latter place 

 much of the rock is glassy, and true tachylite is in great quantity. In 

 associated tuffs at Kakanui, large masses of augite, hornblende, felspar, 

 and peridotite occur. It is impossible to say exactly what is the age 

 of this series of volcanic rocks. They are spoken of above as Post- 

 Miocene. New Zealand geologists, as a body, would hardly assent to 

 this statement. With the exception of the Oamaru occurrences the 

 volcanics rest everywhere upon Cainozoic rocks, usually unconformably. 

 The exact age of these sedimentaries has been a rich subject for argu- 

 ment and dispute. Sir J. Hector and the officers of his survey classed 

 most of them as Cretaceo-Tertiary. Captain Hutton considered them 

 Oligocene. and Professor Park thinks them Miocene, which agrees with 

 the views of the present author. 



The Oamaru occurrence is rather different, for here the dolerites 

 and tachylites are interstratified with sediments to which these various 

 ages have been assigned. They are, therefore, slightly older than the 

 others. 



The main volcanic areas of the South Island are Otago Peninsula 

 and Banks' Peninsula. The former has clear relations to underlying 

 sediments of the doubtful age referred to above. It is unconformable to 

 them, and, in the author's opinion, must be late Miocene or even Pliocene. 

 The rocks are of very varied and peculiar tj^Des. They have been des- 

 cribed in the Q.J.G.S., 1906, and it is impossible in a general paper of 

 this kind to do more than indicate the nature of the variations. 



Nepheline syenites occur sparingly. Tinguaites are abundant, 

 and show connection with camptonites, teschenites, and bostonites. 



A very large series of true volcanic rocks is present. It includes 

 trachytes, which differ from the bostonites only in geological occur- 

 rence. Phonolites are in great quantity and variety ; trachytoid. and 

 nephelinitoid types being represented. Cossyrite is frequent in the more 



