488 Transactions. — Geology. 



fectly conformable manner. The first outcrop, however, 

 occurring at the end of the bay, is a most peculiar one. 

 The grit thins out abruptly. This appearance is due, I 

 believe, to currents, which have produced " contemporaneous 

 erosion," and is not an example of " current-bedding." 



The thickness is about 15 ft., but apparently the bed thins 

 out abruptly. This strange resemblance to an injected lava 

 (there is, however, no alteration, of course, of the surrounding 

 beds) is frequently found in outcrops of the Cheltenham 

 breccia, but not so frequently in those of the Parnell grit. 



Sir A. Geikie, who gives a similar section, writes: "It 

 shows a deposit of shale which, during the course of its 

 formation, was eroded by a channel into which sand was 

 carried, after which the deposit of fine mud recommenced. 

 . It is evident that erosion took place, in a general 

 sense, during the same period with the accumulation of the 

 strata. . . . We may reasonably infer that erosion was 

 due to the irregular and more violent action of the very cur- 

 rents by which the sediment of the successive strata was 

 supplied." 



There is an example of "injection" in the Ponsonby tuff 

 which cannot be explained by current-bedding, as will be seen 

 later ; but current-bedding is sufficient explanation of many of 

 these unconformable appearances. 



From Howick to Turanga Creek there is no outcrop of the 

 grit along the cliffs. At Turanga Creek the greensands were 

 found by me resting unconformably on Maitai slates, without 

 any Papakura limestone between the two. 



Along the cliffy of the Manukau Harbour the beds, as a 

 rule, are almost Horizontal. In places, however, they have 

 been inclined at high angles, and here and there much dis- 

 turbed. It is generally at these spots of distortion that the 

 volcanic beds crop out. 



There is a wharf about a mile or a mile and a half from 

 Onehunga. At low water more of the grit can be seen, as it 

 forms the base of the cliffs between the fault and the White 

 Bluff. Bound the White Bluff the Parnell grit rises some- 

 what steeply ; but that section has already been drawn and 

 described in dealing with the question of the identity of the 

 two breccias. The Parnell grit is here about 12 ft. -15 ft. thick, 

 and it is not as coarse as in the eastern outcrops. 



About two miles beyond the bluff the Parnell grit is again 

 met with, and may be followed for some distance along the 

 base of the cliffs round Cape Horn, where its hardness has 

 been of great service in protecting the cliffs from the 

 effects of marine denudation (Plate XXXVIII., fig. 6). The 

 •section shown in fig. 7 is taken about three miles from 

 Little Muddy Creek, where the last section of the grit to the 



