Marshall. — Geology of North Island. 81 



the peninsula. On the other hand, there is strong evidence of 

 pronounced structural lines in the bed of the Pacific in the 

 same direction as the mountain-ranges, and, if an intermediate 

 depth of 1,600 fathoms be disregarded, actually continuous with 

 the dominant structural features of the North Island. 



If we turn to the rocks of this portion of the land we find 

 three main types — (1) volcanic rocks of many kinds ; (2) Caino- 

 zoic sediments, probably of Miocene age ; and (3) intensely 

 folded and often contorted sandstones and shales, which have 

 been classed as Carboniferous, though there is no definite evidence 

 that they are older than the Mesozoic. With these are associated 

 in many northern localities the plutonic rocks previously noted. 



Of these three rock-groups, the first two are not folded, and 

 therefore afford no evidence as to the structural features at 

 present being considered. The slates and sandstones have, 

 however, been subjected to earth-pressure of an intense nature, 

 and it is from them that information is to be expected. Though 

 the whole of the area has been geologically examined, it is a 

 remarkable fact that there is in the reports that describe the 

 country practically no statement as to the direction of the 

 strike and dip of these older sediments. I was able to make 

 a few observations last summer in the Bay of Islands, and here 

 the beds are much contorted, and are often so changed that the 

 stratigraphic planes are completely obscured. However, from 

 the observations that could be made, there appeared to be a 

 north or north-north-east strike, and the same direction appeared 

 to be represented in the hills between Mangonui and the Oruru 

 Valley, and in the shales that are occasionally displayed in the 

 range extending from Reef Point to Raetea. This statement 

 is very general, but it remains the only indication of the structural 

 lines of the country. So far as it goes, it indicates that the trend 

 of the land is not a result of structural characters, but, as it were, 

 accidental, because here it happened that fragments of moun- 

 tains with a northerly strike in many ranges were left in such 

 large numbers as to constitute an apparent north-westerly 

 trend. This view is in accord with that expressed by Suess. 



At present a portion of the district is being examined in detail 

 by the reorganized Geological Survey, so definite information 

 mil shortly be forthcoming. 



The second matter of special interest is the occurrence of 

 plutonic rocks at various places, which has been noted by McKay, 

 who referred them to syenites or diorites. At Mangonui Town- 

 ship McKay states that these rocks are interbedded with sand- 

 stones and shales. Of this no evidence could be seen. Certainly 

 the character of the rocks varied somewhat : the colour is darker, 

 and they are more compact in some places than in others. When 



