Marshall. — Geology of Cape. Runaway District. 



285 



All the specimens collected show a great similarity in composition and 

 structure. There are two distinct types, holocrystalline and glassy. The 

 glassy type is formed almost entirely of a dark-brown glass with incipient 

 crystallization in black semi-opaque patches. There are no crystals or 

 microlites present. 



The holocrystalline rocks are somewhat diabasic in structure, often 

 ophitic, with relatively little olivine, which is nearly completely changed 

 into serpentine. The feldspar is mainly labradorite much decomposed. 

 The augite is nearly colourless, and is always allotriomorphic. Iron -ore is 

 plentiful, apparently entirely ilmenite. These two types closely resemble 

 those that are found at Oamaru, where also they are interbedded with the 

 limestone of Tertiary age. They have been described by Hutton.* Huttonf 

 also describes several other glassy types of a similar nature. He afterwards 

 states that the rocks occur interstratified with sedimentary rocks of Oamaru 

 age at intervals from Look-out Point, near Hampden, to Castle Hill, a 

 distance of 150 miles. | McKay and Sollas describe similar types from the 



HICK* BAY 



Maftai 

 system 



Mason River, in South Nelson, where again they are interistratified with 

 limestone rocks of Oamaru age.§ It thus appears that over a wide extent 

 of the eastern coast-line of New Zealand submarine eruptions of a basic 

 nature occurred at the time when the limestone of Oamaru age was under- 

 going deposition. It has been suggested in another paper that the lime- 

 stone of this series was deposited approximately at the same time throughout 

 New Zealand, and that it was laid down when the country had reached its 

 maximum of physical depression .|| If this be the case, it is evident that this 

 widespread series of submarine eruptions was practically simultaneous, 

 and ushered in a period of general epeirogenic elevation in the New Zealand 

 region. 



* Trans. N.Z. Inst., vol. 19, 1886, p. 417. 



t Jour. Rov. Soc. N.S.W., 1889, p. 152. 



% Trans. 1SLZ. Inst., vol. 32, 1899, p. 170. 



§ " Rocks of Cape Colville Peninsula," vol. 2, p. 168. 



i| Trans. N.Z. Inst., vol. 43, 1910, p. 404. 



