182 Transactions. — Geology. 



circle round the bases of hills formed by older rocks. Not 

 only was the last touch given in the Eocene period to the 

 internal structure of the mountains, but the chief valleys were 

 also deeply scoured out, so that when the land sank again in 

 the Oligocene period these valleys were filled up with marine 

 limestones and other rocks. 



The Oligocene and Miocene were periods of depression, 

 separated by a slight upheaval which lasted only for a short 

 time. During most of the Middle Tertiary era New, Zealand 

 must have formed a narrow ridge of land, very irregular in 

 shape, running north-east and south-west, with some detached 

 islands on each side, three or four on the south-east side, and 

 a dozen or more to the north-west, none of them being very 

 high above the sea. 



In the older Pliocene came the last great upheaval. All 

 the islands were jonied together, and the land stretched away 

 to the east and south so as to include the Chatham and Auck- 

 land Islands, as well, perhaps, as Campbell and Macquarie 

 Islands ; while to the north it certainly extended to the 

 Kermadecs, and perhaps much further. On the mountains 

 of the South Island large glaciers were formed, and the 

 torrential rivers running from them tore into disconnected 

 fragments the Miocene marine rocks which obstructed their 

 valleys. Probably at this time more land than at present 

 existed in the Antarctic Ocean, for New Zealand added to 

 its flora and fauna many antarctic plants and marine animals. 

 But this land could not have connected New Zealand with 

 either Patagonia or South Africa, for if it had done so we 

 should certainly have had many more inmiigrants, including 

 land birds, and, probably, mammals. 



It is possible that this large extension of land to the east- 

 ward may have produced desert or steppe-like conditions in a 

 portion of New Zealand, evidence of which some botanists 

 think they find in our flora ; also, in the old lake at Kapua, 

 near Waimate, there is some slight evidence of a dry epoch 

 having, at that place, succeeded the diluvial epoch during 

 which the moas were buried.''' But this may have been due 

 to quite local causes. 



Subsidence seems to have commenced first in the southern 

 portion of the North Island, for in the newer Pliocene large 

 portions of what arc now dry land were under the sea, and 

 Cook Strait had been formed. But at a later date sinking 

 began in the South Island also, so that in the Pleistocene 

 period the sea at Amuri Bluff stood at least 500 ft. higher than 

 it does now. This sinking has again been followed by an 

 elevation of all parts of New Zealand, the centre of the 



* Trans. N.Z. Inst., vol. xxviii., p. 629. 



