436 Transactions. 



violent whilst the land was still submerged and sedimentation was still in 

 progress. Evidence of this is found at Mohinui, which is a volcanic neck 

 It is here clearly seen that water penetrated into the crevices of the volcanic 

 rock and caused its sudden solidification in the vitreous state. It is also 

 noticeable that the scoriaceous volcanic matter round this neck is quite 

 un oxidized. This inclusion of fragments of sedimentary beds in the volcanic- 

 material of submarine eruptions is well seen at Cape Horn, on the western 

 shore of the Manukau Harbour. Here large masses of the Waitemata beds 

 are included with the andesitic volcanic matter deposited by contempo- 

 raneous volcanic eruption. 



There appears to have been a centre of volcanic activity near the western 

 entrance of the Funnel, for a large mass of andesitic lava occurs here. 

 The rock is a typical hypersthene-andesite. On the shore opposite to Pakau- 

 rangi Point the rocks have been violently disturbed, hydraulic limestone, 

 " Waitemata beds," and volcanic lava being closely associated. The only- 

 visit paid to this locality took place at high tide, and the details could not 

 be observed. It is probable that the formation would be uncovered at low 

 tide to a sufficient extent to allow of an interpretation of the structure being- 

 found. • 



At this point there is a coarse conglomerate resting apparently with 

 unconformity on the Pakaurangi beds. This conglomerate has an interest 

 beyond the ordinary in that it contains some pebbles of a diorite which is 

 not known to occur in place anywhere in this district. The nearest locality 

 where plutonic rocks are definitely known to occur in place is Ahipara on 

 the west side and Mangonui on the east side of the North Island respectively, 

 but both of these places are some seventy-five miles distant. 



In the series of rocks thus arranged no distinct strati graphical break 

 was observed, though this point is most difficult to decide because of the 

 extent to which the rocks have been disturbed. Even at Pakaurangi Point, 

 where the stratification is clear and the exposures continuous, there are 

 some difficulties, and the strata are here clearly seen to be so disturbed as 

 to change completely in strike and dip within very short distances. 



Some previous observers have described several stratigraphical breaks 

 in this rock series. S. H. Cox* in 1879 represented the hydraulic limestone 

 as Cretaceo-Tertiary in age, while the limestone of the Gibraltar Rocks is 

 classed as Eocene, and is represented as folded in a synclinal manner while 

 resting on a highly eroded surface of the hydraulic limestone. However, 

 Cox correlates the limestone of the Gibraltar Rocks with the Waiomio 

 limestone at Kawakawa. In that place, as mentioned earlier, a bore has 

 clearly shown that the Waiomio limestone is lower in the series than the 

 hydraulic limestone. Cox also places the fossiliferous beds of Pakaurangi 

 Point (called by him Komiti Point) in the Miocene period, but he does not 

 indicate precisely the stratigraphical relation between the Pakaurangi beds 

 and the limestone of the Gibraltar Rocks which he calls Eocene. 



Parkf in 1885 classed the beds of Pakaurangi Point in the Eocene, but 

 all the other strata in the district are classed in the Cretaceo-Tertiary. In 

 1887 Park reported further on the same district. The Pakaurangi (Komiti) 

 Point beds are in this second paper placed in the Miocene. Most of the 

 other strata are placed in the Cretaceo-Tertiary. However, the white clays 



* S. H. Cox, Geology of the Rodney and Marsden Counties, Rep. Geol. Explor. dur. 

 1879-80, 1881, pp. 18, 19. ■ 



t J. Park, On the Kaipara District, Rep. Geol. Explor. dur. 1885, 1886, pp. 164-70. 



