Fox. — The Waitemata Series. 491 



fairly certain that the Wairau tuffs are here about 70 ft. below 

 the Parnell grit, which coincides with the supposed general 

 position of the beds. The tuffs are more sandy and thinner 

 than at Wairau. 



The Wairau tuffs occur at the Tamaki, near the west head. 

 Apparently they are above the Orakei greensand, but faults 

 make it impossible to say with certainty. 



At Howick the Wairau tuffs again crop out, this time in 

 numerous thick bands separated by several layers of shale, 

 and shading off into sandstones. Here they are traversed by 

 numerous zeolite veins. They occur not far from the last 

 outcrop along Howick cliffs of the Parnell grit, but the rela- 

 tion between the two is obscured by several faults. 



At Maungamaungaroa Creek there is another outcrop, and, 

 judging from the dip, these beds should be nearly at the lowest 

 horizon of the Turanga greensands, the Parnell grit occurring 

 a little above the greensands. 



As seen in a section, close to Onehunga, on the Manukau 

 Harbour, the tuffs resemble the outcrop at Howick. 



With regard to the Wairau tuffs, I am inclined to think 

 that, just as in the case of the Cheltenham breccia, it is a 

 group on the whole synchronous (and probably marking a 

 gradual quiescence of the Waitakerei chain), but derived from 

 different vents along the chain, just as in the former case. 



Tamaki Tuff. 



At the Tamaki and at Maungamaungaroa Stream there 

 occurs a thin tuff (2 ft. thick), with numerous small lapilli, 

 traversed by veins of large calcite crystals. Its position is 

 30 ft. below the Orakei greensand, as seen at the Tamaki 

 Gulf, some distance from the west head. I have not seen it 

 elsewhere. 



The Ponsonby Tuff. 



The Ponsonby tuff is a most interesting bed. In the first 

 place, it is quite a thin bed, and yet has a wider distribution 

 than any bed in the Waitemata series. In the second place, 

 it shows some peculiar results of distortion. It is nowhere 

 more than 2 ft. thick, yet it occurs at the Tamaki, at St. 

 Helier's Bay, at the Manukau, at Ponsonby, at Cheltenham, 

 at Narrow Neck, at Wairau Creek, and at Deep Creek. 

 When unearthed it is a blue soft bed, rather sandy to the 

 touch, speckled with white flakes of kaohnised feldspar. 

 These flakes are thickly crowded together, sometimes as 

 many as 500 in a square inch. Occasionally a small red 

 patch of scoria is seen. The rock weathers to a pale-yellow 

 in which the white feldspars are still visible. 



On the whole, the bed grows thicker and coarser in a 

 north-westerly or westerly direction, and I believe it came 



