GEOLOGY OF NEW ZEALAND. 197 



not possible to prove its existence. The rocks of the Oamaru and 

 younger systems are found at nearly equal elevations on both 

 islands ; but are higher in the central part of the Xorth Island than 

 elsewhere. On the contrary, the rocks of the Waipara and older 

 systems go to considerably greater heights in the South than in the 

 !N'orth Island, consequently the " Cook's Strait fault," if it exists, 

 was probably formed in the interval between the deposition of the 

 Waipara and Oamaru Systems, the downthrow being to the 

 north. 



Rocks belonging to the Hokaniii System are found on the eastern 

 side of the Maitais in the Euahine range in Wellington, and in the 

 Eaukamara range near the East Cape. In the Kawhia and Eaglan 

 districts, in the Auckland Province, they lie on the western side of 

 the Maitais. So probably the ge-anticlinal of the South Island runs 

 through the centre of the North Island from Wanganui to the Bay 

 of Plenty. 



All the rock systems, up to the Hokaniii inclusive, have much 

 the same lithological characters throughout New Zealand, and can 

 be broken up into series, which are chronologically distinct. They 

 may be called " continental formations," that is, rocks formed on 

 the shore of a continent with large rivers. All the rock systems 

 above the Hokanuis are, on the contrary, very variable in litho- 

 logical character in different localities, even when not far apart ; 

 the only exceptions being a few limestones, probably the relics of 

 coral reefs. These may be considered as " insular formations," that 

 is, as having been deposited round the margin of islands, from 

 which ran no great rivers. It is impossible, at any rate at present, 

 to divide these latter systems into series which are in all cases 

 chronologically distinct. The series here are geographical, and over- 

 lap each other ; but I have to some extent indicated their probable 

 relations, in the table of formations. 



Ei'upiive rocks cover but a small area in the South Island. Iso- 

 lated exposures of granite occur along the ge-anticlinal axis from 

 Paringa Eiver in Westland to Lake Eotoiti in jSTelson, and in a few 

 other places west of the axis, the largest area being in the south- 

 west of Otago, at Preservation and Chalky Sounds. On the east 

 there are a few patches of volcanic rocks of younger date. In the 

 North Island, also, volcanic rocks are rare on the east side of the 

 main range ; but on the western side, from the centre of the island 

 to Auckland, they cover more than half the country, and appear 

 again in great force further north, between Hokianga and the Bay 

 of Islands. There is no granite in the North Island. 



Dr. Hector has estimated the percentage of area covered by these 

 different formations as follows * : — 



North Island. South IsJand. 



Waipara System upwards 56-4<i 24-72 



Manapoim to Hokaniii Systems 11-92 73-37 



Eruptive Eocks 31-62 1-91 



100-00 10000 



* Handbook of New Zealand, 1880. I have altered the arrangement. 



