696 E. S. MOORE 



These major zones of disturbance run parallel to the main 

 structural features of the islands resulting from the orogenic and 

 epirogenic movements which produced New Zealand and the 

 adjacent islands. 



HISTORY OF THE LATER VOLCANIC ACTIVITY OF NEW ZEALAND 



There seems to be a general agreement among New Zealand 

 geologists that there were extensive post- Jurassic and pre-Mioeene 

 movements, resulting in much folding and in bringing the islands 

 nearly to their present geographical condition. The rocks formed 

 up to this time indicate, according to Marshall, 1 that the present 

 islands occupied a zone along the border of a continent now lost to 

 sight. The folding raised the mountain ranges from the sea bottom 

 and determined the major structures of the islands. There have 

 been numerous oscillations since that time, but these have not 

 materially altered the main structural features. Following these 

 great disturbances, which may be correlated with those of America 

 and Europe, there was inaugurated an important stage of igneous 

 activity which became very prominent in the Miocene and has 

 continued, more or less actively, since that time. There was some 

 igneous activity during the Jurassic, and even then hypersthene- 

 andesites, so common in later periods, began to make their appear- 

 ance. Igneous rocks of this age are found, according to Park, 2 in 

 the Hauraki Peninsula, while the andesites and rhyolites of the 

 Canterbury district in South Island are regarded by some geologists 

 as Jurassic. 



The greatest period of activity seems to have opened in the 

 Middle or Lower Miocene and to have extended into the Pliocene, 

 and even into the Recent, in North Island. During the Miocene, 

 which was also characterized by extensive orogenic and epirogenic 

 movements, the main centers of activity were the Otago, Banks, 

 and Hauraki peninsulas. The rocks of these areas generally rest 

 on Omaru sediments, which are regarded as Early Miocene. In 

 the Otago Peninsula the alkaline rocks were erupted at this time; 

 in the Banks Peninsula, rhyolite, andesite, and basalt; and in the 



1 P. Marshall, Geology of New Zealand (Wellington, N. Z., 191 2), p. 188. 



2 James Park, The Geology of New Zealand (Whitcombe & Tombs), p. 82. 



