492 Transactions. — Geology. 



from some explosive outburst of a Waitakerei volcano. At 

 the Tamaki it occurs as a thin bed 1 ft. thick not far from the 

 west head. There is a bay and two faults at least between 

 it and the Parnell grit. At St. Helier's Bay it occurs at 

 Watson's Point, the westerly head of the bay, among very 

 much contorted strata. It is not very far from the reef of 

 the Cheltenham breccia. At the Manukau it occurs near the 

 Wairau tuffs. Here it has been drawn out in a most curious 

 fashion. The spot is near an area of distortion. All the 

 lumps are elongated in the direction of the dip of the beds. 



At Cheltenham it occurs near the breccia, much crushed. 

 At Wairau Creek it occurs on the bank of the creek in the 

 most distorted part of the cliff, and has been crushed out com- 

 pletely, occurring as a lenticular mass. 



In all of these localities it seems to be a little above the 

 breccia. 



Across the neck on the North Shore no section can be seen, 

 but the dip continues regular. The tuff would therefore seem 

 to be more above the breccia than is usually the case, and 

 some fault may be present. 



In the section at Acheron Point the relative positions of 

 the beds are quite clear, but it is not so certain that there is 

 present an extension of the Cheltenham breccia seven or eight 

 miles away. The question of its position at Acheron Point 

 has already been dealt with in describing the Parnell grit. 



8. Conclusion. 



I have now described all the volcanic beds of the Waite- 

 mata series, and (to recapitulate) have come to the following 

 general conclusions : That in late Oligocene times, in the 

 shallow sea near Auckland, there rose a long line of vents, 

 which were at first very powerful and gave rise to several 

 coarse breccias, laid down amid conflicting currents on the 

 fossihferous sea-floor. But, as usual, after these first violent 

 eruptions, from which were derived the Cheltenham breccia 

 and the Whangaparaoa breccia, and no doubt several others, 

 besides the massive breccias found on the west coast, there 

 were other manifestations of volcanic activity, on the whole 

 more feeble, but some explosive eruptions on a large scale ; 

 and it is to these we must look for the source of the Wairau 

 tuffs and the Ponsonby tuff. Meanwhile the whole area 

 gradually sank, till, towards the close of the Miocene period, 

 the Palaeozoic islands and ridges were mostly covered by the 

 waves of the advancing sea, which laid down in regular suc- 

 cession shales and sandstones, even on the older lava-streams 

 of the Waitakerei vents. But at the same time, and pro- 

 bably earlier too, volcanic outbursts were taking place on the 

 Coromandel Peninsula, some of them of sufficient magnitude 



