Hutton. — On the Age of the Orakei Bay Beds. 311 



the Parnell grit dips southerly and reaches the sea-level some distance from 

 the head of the bay, so that all the rocks at the head of the bay must lie 

 above it. On the west side of the bay the Parnell grit is not seen ; and, in 

 my opinion, it either thins out or passes below the Point Britomart beds. 

 As, however, the section has two breaks, one in St. George's Bay and the 

 other in Mechanic's Bay, nothing certain can be made out ; but it is worthy 

 of notice that the beds above the Parnell grit on the east side of St. George's 

 Bay contain plant remains, as also do those at Point Britomart. Next, 

 with regard to Mr. McKay's first statement : To the east of Parnell, be- 

 tween Resolution Point and Hobson's Point, there is a break across Hob- 

 son's Bay, a mile in length, in which nothing definite can be seen. It is, 

 therefore, quite impossible for any one to say, from stratigrapbical evidence, 

 whether the beds at Hobson's Point are above or below the horizon of the 

 Parnell grit, and consequently whether they are or are not the equivalents 

 of the Point Britomart beds. It is indeed probable that, on the whole, the 

 rocks of the Waitemata series get younger to the westward ; but, although 

 usually nearly horizontal, they are subject to strong local disturbances — as 

 at Cape Horn, Freeman's Bay, Wangaparoa, and Parnell, — and it is as 

 likely as not that the very oldest beds in the series may have been brought 

 up at Parnell. 



Neither can Mr. McKay produce any evidence of an unconformity below 

 the Parnell grit. He says, " Respecting the question of an unconformity 

 between the Orakei Bay beds and the higher miocene rocks, I should submit 

 that, when estuarine muds and soft sandstones are suddenly succeeded by 

 coarse volcanic agglomerate, there is, by whatever degree the unconformity 

 is measured, most surely unconformity to a certain extent ; and when it is 

 determined that the beds above and below belong to different groups of 

 formations — e.g., the cretaceo-tertiary and the miocene — although no strati- 

 graphical unconformity were apparent, the conclusion that there is such 

 cannot be escaped."* Accordingly in his section from " Auckland north to 

 Wade" he shows the Parnell grit highly unconformable to the underlying 

 beds. The idea that an outbreak of volcanic energy must necessarily mark 

 an unconformity may be passed over in silence ; but if Mr. McKay had 

 proved that the two sets of beds belonged to two different formations of very 

 different ages, then all would allow that an unconformity was probable 

 although it might not be apparent. But this is just what Mr. McKay has 

 not done. He recognizes the few fossils found north of Lake Takapuna, 

 above a bed supposed to be the Parnell grit, as miocene, and says that they 

 differ from those found at Orakei ; but he makes no reference to the fact 

 that Mr. Cox had found the Orakei fossils mixed with miocene shells at 



* I.e., p. 106. 



