Marshall. — Geology of North Island, 79 



EXPLANATION OF PLATES XI AND XII. 

 Plate XL 



1. Fracture cleavage in rock-face, lower schists, Alexandra. (Photo by 

 Professor Park.) 



Plate XII. 



1. Fracture cleavage in boulder, Bannockburn Bridge. (Photograph.) 



2. Section of chlorite-schist, Dunstan Range. Magnetite (black) marks 



the foliation-planes. Chlorite (cloudy) and quartz (clear) are present. 



X 32 diameters. 

 3a. Section of granular chlorite-schist, Gibbston. Shows large recrystal- 



lized feldspars and quartz, x 32 diameters. 

 36. Same negative as 3a ; printed deep, to show centric arrangement of 



epidote and twinning of feldspar. 



Art. V. — Geology of Centre and North of North Island. 

 By P. Marshall, M.A., D.Sc. 



[Bead before the Otago Institute, \0th September, 1907.] 

 Plate XIII. 



A great deal of interest is attached to the northern part of 

 the North Island from a geological point of view. This interest 

 is partly a result of the direction of the trend of the land, which,, 

 somewhat to the west of north, offers a striking contrast to that 

 of the rest of the Dominion, which is directed north-east and 

 south-west. It is of some importance to know whether this 

 direction of the northern portion indicates a new structural 

 direction, or whether the land is composed of broken fragments 

 of mountain-ranges parallel to the great structural feature of 

 the North Island — the Tararua-Euahine-Kaimanawa-Raukumara 

 chain. 



Additional interest attaches to the extreme north, because 

 here Mr. McKay has mentioned the occurrence of intrusive 

 masses and " sills " of crystalline rocks of plutonic character,, 

 which he has classified with the syenites. Except for the 

 occurrence of tonalites and other dioritic rocks from the Cape 

 Colville Peninsula, and of granites as boulders in conglomerates 

 at Alexandra and at Gisborne, plutonic rocks are unknown in 

 the North Island. From a popular point of view, the greatest 

 interest attaches to this part of New Zealand because volcanic 

 action has been more pronounced here than elsewhere, and is 

 still maintained spasmodically. No comprehensive attempt has 

 been made to deal with these volcanic areas since Hochstetter's 

 time, though much information has been gained by several 

 investigators in various parts of the district. 



