78 president's address — section c. 



moire crystalline schists tO' the east, seprrmtines make their appear- 

 ance, and arei continuous apparently for over fifty miles. The 

 band of serpentine is generally less than a quarter of a mile wide, 

 and frequently not more than 300 or 400 feet. 



Further north in the regions of t-ie Wect Coist that have been 

 mapped, Morgan suggests that the Lower Palaeozoic rocks were 

 folded along approximately north-westerly axes in later Palaeozoic 

 times, and were then invaded by plutonic rocks. Further move- 

 ment occurred during Cretaceous times. Henderson (1917) would 

 think that the plutonic masses were intruded in two series, the 

 older gneissic series being pre-Ordovician, the younger granitic 

 rocks being of late Mesozoic age formed during the principal era 

 of Mesozoic intrusion, when where was developed a great series of 

 ma or fractures parallel with the trend of the Alps, and adds: 



There is no doubt but that the force that crumpled that range 

 produced lines of weakness in the foreland, against which the 

 folding took place." Here, however, tne axis of the Mesozoic 

 folding was oblique to the grain of the basement rocks, and 

 faulting of the latter, especially if in long strips, becomes very 

 obvious. Further orogenic crust-movement occurring here in 

 Tertiary times is, however, noted below. 



In most of the North Island less complexity is seen in the strike 

 of the older rocks, though the slight obliquity of the roughly north- 

 north-easterly strike of the fold to the north-east faults has been 

 noted by Cotton in several districts. In the North Auckland 

 Peninsula, however, great difficulties occur, and little new infor- 

 mation has b 'len recorded since Marshall (1912) summarised the 

 local variation of strike, and indorsed Suess' comment that the 

 north-western coast in no way represents the actual trend of the 

 mountains. As will appear, this folding was practically com- 

 pleted by Middle Ctetaceous times, whon sedimentation occurred 

 locally. It is generally known as the post-Hokoaaui orogeny. 



The igneous rocks erupted during thfs period of folding include 

 ultrabasic and basic types, and probably also granites. Com- 

 mencing at the North Cape, there are gabbrcs, norites, and harz- 

 ber2[ites, the age of which is not definitely known (Bell, 1910). The 

 noritei, and especially the diorite of Ahipara and Monganui are 

 perhaps of pre-Maitai age, though Marshall's latest statement 

 therron (1912) classes them as post Matai. They have a strong 

 likene-s to certain Fiordland rocks. Sills ( ?) ol serpentine 

 occur near Auckland, and on the Mokau Eiver in North 

 Taranaki, and these invade the Mesozoic sediments. So also do 

 the long complex sills of Dun Mountain, and the narrow sills in 

 the Alps stretching south-westwards through the Nelson Province 

 into Westland. In the neighbourhood of the last, there occur 

 intrusions of granite, &c. , and the usual porphyritic and lampro- 

 phyric dyke-rocks. Some of these are of an alkaline facies 



