Bell and Clarke. — Geological Reconiiaissance of Northernmost N .Z . 619 



A very similar grit-bed occurs at the north end of Wharekau Bay, un- 

 conformably overlying the mass of igneous and sedimentary rocks which 

 constitutes the North Cape headland. 



(2.) Upper Beds. — Between Parengarenga North Head and Wharekau 

 Bay the Coal Point Series forms a syncline, the upper beds being exposed 

 along the coast-line. These beds, which are coarse volcanic breccias in- 

 cluding fragments of stone up to 2 ft. in diameter, interbedded in their 

 lowest parts with finer sedimentaries, occupy the sea-front as far as Coal 

 Point. They exhibit a rude stratification, and are in some places seamed 

 with calcite veinlets, and in others with stringers of opal. 



At Coal Point a seam of impure lignite about 6 chains long and 1 ft. 6 in. 

 thick, striking east and west, and dipping to the south at 35°, is inter- 

 bedded with the breccias. The outcrop is interesting as afiording evidence 

 of the probable presence of a land-surface here during the accumulation 

 of the breccias, but is of no economic importance. 



The Coal Point Series throughout the rest of the area in which it occurs 

 is represented only by the breccias which belong to the upper horizon. 

 Good exposures are to be seen on the track from Parengarenga Harbour 

 to Te Paki Sheep-station, where pebbles of sedimentary rocks occur amongst 

 the volcanic fragments, and at the eastern point of Spirits Bay. At this 

 latter place " the lower three or four feet" of the breccias " are so crowded 

 with remains of a species of Scalpellum as to form an impure shelly lime- 

 stone."* 



(3.) Petrology. — Megascopically the constituent fragments of the Coal 

 Point grits and breccias would be identified as andesitic rocks of medium 

 grain, showing phenocrysts of plagioclase and pyroxene. The small frag- 

 ments from the lower grits are usually more basic in appearance than the 

 boulders of the coarse breccias. 



Microscopic sections of the basal grits show that they are composed of 

 fragments of lava closely agreeing with those found in the overlying coarse 

 breccias. In the grit fragments, however, crystals of highly altered oUvine 

 are rather frequent. The grits are much seamed with veinlets of a zeohte, 

 apparently natrohte. 



Representative sections from the coarse breccias show that the preva- 

 lent rock is an augite-andesite, with a hyalopilitic groundmass in which 

 glass predominates over feldspar laths and augite granules. The augite 

 phenocrysts, which vary much in abundance in different sections, are pale 

 brown or yellow in colour. Porphyritic feldspars are abundant, the domi- 

 nant ones being andesine and labradorite, the latter being the more fre- 

 quent and having many glass inclusions. (Plate LVI, fig. 1.) 



(4.) Correlation and Age. — The lowest beds of the Coal Point Series 

 contain fossil MoUusea which are apparently of Miocene age. McKayf 

 correlates them with the lignite-bearing beds of Cooper's Beach and the 

 fine-grained tuffs at the base of the volcanic breccias of Whangaroa Harbour. 



The Scalpellum found at the base of the breccias in Spirits Bay is re- 

 garded by Hector and McKay as identical with thatj occurring at Chamber- 

 lain's Island, near Auckland, in strata which, it is agreed by Cox,§ Park,|| 



* McKay, Rep. G.S., 1894, p. 82. 

 fRep. G.S., 1894, pp. 82, 83. 



j More recently described by Benhani as Pollicipes aucklandicvs : Geol. Mag. , 

 March, 1903, p. 110. 



§ Rep. G.S., 1879-80, p. 16. 



I) Trans. N.Z. Inst., 1889, p. 394. 



