Mulgan. — The Waitemata Series. 427 



Section VI.— Geit-beds of the Whangaparaoa Peninsula. 



The next important outcrops of these volcanic grits are on 

 the Whangaparaoa Peninsula, where they occur in consider- 

 able numbers and exhibit; great variety of texture. As else- 

 where, they lie here conformably between the other members 

 of the series, which have been much disturbed in their 

 vicinity. 



Starting from the northern side and travelling east, the 

 ash-beds are first met with in a place called Coal-mine Bay. 

 Here the grit occurs as a well-marked band dipping north at 

 an angle of 8°. In composition and appearance this bed corre- 

 sponds with those described previously, being perhaps, on the 

 whole, a little coarser in texture. It varies from fine to 

 coarse, the coarser material being below, shading into a fine 

 conglomerate. The exposure at this place is not large, but 

 about half a mile further on the same band outcrops again 

 and forms a reef running for some distance into the sea. The 

 included blocks, which are numerous, consist of a hard, com- 

 pact, fresh-looking andesite, with large porphyritic crystals of 

 augite and a triclinic feldspar. Examined microscopically a 

 section from one of these blocks showed a ground-mass and 

 porphyritic constituents almost identical with those already 

 described. The feldspars comprise the varieties andesine and 

 oligoclase, and, as in the other sections, show numerous in- 

 clusions of augite and magnetite. The augite crystals are per- 

 haps larger than those in the other rocks described, whilst the 

 olivine, although showmg crystalline form, is much altered, 

 and is not present in sufficient quantities to form an essential 

 constituent. Chlorite, evidently an alteration product, occurs 

 in several places in abundance. (Specific gravity, 2-8.) 



From Coal-mine Bay east the grits and fine conglomerates 

 are numerous, cropping out at intervals all along the coast. 

 They are similar in appearance to the one just described, ex- 

 cept that they become distinctly coarser towards the point to 

 the east The beds here have been so disturbed and the ex- 

 posures in places are so small that it is impossible to establish 

 any stratigraphical connection between individual outcrops. 

 In both grits and conglomerates fossils occur from top to 

 bottom. The included fragments here reach a diameter of 

 from 1 ft. Gin. to 2ft., and occur in greater abundance than 

 in the grits nearer Auckland. 



Towards the end of the point great blocks of andesite ap- 

 pear, measuring in one case at least 18 ft. across. This huge 

 mass must have fallen on the bottom and been covered up 

 with sediment. The force with which the mass fell may have 

 displaced the strata, causing the appearance presented in the 

 figure in the margin. It may, moreover, have fallen in water. 



