Mksmkhhos . ~Sinff/c( /''()/ //!s iiiid l)r<i nKKji -Atjuit' itiK of \\ (.<( .\<'J.iOii. SIS' 



represented by a series of base-li'velled islands ; to the east the long line of 

 what is now the alpine peneplain rose from a shallow sea. 



Elevation now took place. In this portion of New Zealand the eleva- 

 tion was of the plateau-forming order, merging into the fold-movement of 

 the Kaikouras and North Island ranges. This fold-movement was accom- 

 panied, perhaps casually, by the foundering of the northern continuation of 

 the alpine peneplain. The elevation was accompanied in west Nelson 'oy 

 the intrusion of the unconsolidated ultrabasic j)ortions of the magmas, of 

 which the acid portions are represented by the granites that even in Miocene 

 times had been exposed by denudation. The lavas of Koiterangi and 

 Paringa and the dunites of the Pounamu formation belong to this period. 

 Here also belong the protogines and hornblende granulites produced b}" 

 movement along the alpine overthrust. The elevation was of a differential 

 nature, and the alpine peneplain was elevated more than the other pene- 

 plains. Again, different parts of the alpine peneplain were differentially 

 elevated, and the greatest elevations seem to be immediately opposite to 

 the depressions on the west of the overthrust. Thus in Westland, south of 

 the Wanganui, the alpine peneplain has been very greatly elevated, while 

 the granites which probably at one time occurred here to the west of the 

 overthrust have disappeared. Again, the alpine peneplain is relativelv 

 high between the Upper Maruia and the Wairau, and to the west of the 

 overthrust is the Kawatiri depression. Opposed to the Whakatu rift-valley 

 and the relatively depressed alpine j^^i^^'plain is the high land of the 

 Kaikouras. 



Draixage. 



The elevation of late Miocene times initiated a new cycle of erosion.. 

 The streams from the base-levelled land united to form larger streams, which 

 flowed through the rift-valleys across the newly deposited strata. Thus 

 the Aorere Avas formed from streams draining the west and north-west 

 of the Mount Arthur j)eneplain. The Whakamarama peneplain on eleva- 

 tion was tilted to the north and Avest, and the consequent streams flow 

 north-west to the sea ; later, the Kaituna broke through the eastern fault- 

 scarp and captured some of this drainage for the Aorere, which, however, 

 lost its head-waters to the Heaphy and Big Rivers.* The Takaka cut out 

 its channel along the Takaka and Karamea faults as far as the Upper 

 Karamea,f Avhich was afterwards captured by the Karamea in accordance 

 with the law of greatest slopes. The Kawatiri basin at this time drained 

 into the Whakatu, { while the Oweka rift-valley was drained by a river 

 having the head-Avaters of the Mokihiuui as its course, and its mouth near 

 Lake Brunner.§ Tributaries from the alpine peneplain floAved right across 

 the intervening Victoria peneplain : such were the Ahaura, Upper Grey, 

 and Inangahua, the volume of the latter being then increased by the present 

 Upper Maruia. Similarly, the Taramakau floAA-ed across the Wainihinihi 

 peneplain. 



A pause, in elevation permitted the river-SA'stems to mature and a vast 

 accumulation of gravels to be formed. These gravels occur in the valley.^ 

 of the Aorere auv^" Takaka. The Whakatu filled its A'alley AA'ith the Moutere 



* Cox : Geoi. Surv., Jso. 10, p. 67. 



t Mackay : Gold-deposits of N.Z., p. 11. 



i Cox : Geol. Surv., No. 16, p. 68. Park : Trans. X.Z. Inst,, vol. 37, p. 549. 



§ Haast : Geol. Exi^lor. of W. Nelson, p. 103. Marshall : Geog. of N.Z., pp. 140, UL 



