466 Transactions.- — Geology. 



I believe that the real reason for this deceptive appearance 

 is to be found in current-bedding. The ancient sea which 

 washed the flanks of the Waitakerei hills was probably 

 studded with islands, of which few now remain. The prox- 

 imity to the surface, however, of the Palaeozoic quartzites and 

 silky slates, some of which the Cheltenham breccia did not 

 cover, is evidence of their former existence. This may have 

 produced violent and conflicting currents which deposited the 

 breccia on the earlier sands and mud-flats in a somewhat 

 irregular way. The Waitakerei hills w T ere not very far distant, 

 and the isthmus of Auckland was then a narrow strait. 



The argument for a Pliocene age rests entirely on the 

 supposed unconformability. The argument for a Miocene age 

 rests on overwhelming fossil evidence and also on stratigraphy. 

 The unconformability might not, in any case, be serious, and 

 the appearance may be otherwise explained ; but Oligocene 

 fossils, unless derivative, could not be found in a Pliocene bed. 



The stratigraphy points to an Oligocene age for the Chel- 

 tenham breccia. It may be shown that the breccia is strati- 

 graphically below the Parnell grit ; that there is no volcanic 

 bed between the Parnell grit and the Orakei greensand ; and 

 that the Cheltenham breccia is consequently inferior to the 

 Orakei greensand — a Lower Miocene bed. It may further be 

 shown that the Orakei greensand is the equivalent in position 

 and fossil contents of the upper parts of the Turanga green- 

 sands which overlie the Papakura limestone ; and it follows 

 that the Cheltenham breccia is either the equivalent of the 

 lower greensands at Turanga (and therefore at the bottom of 

 the Lower Miocene) or of the limestone at Papakura (and 

 therefore at the top of the Oligocene). The evidence for each 

 of these propositions is given below. 



(a.) The breccia is below the Parnell grit. This has been 

 incidentally shown in discussing the question of their identity ; 

 but it will now be necessary to give the evidence which leads 

 me to consider the coarse beds at Wairau Creek, Cheltenham 

 Beach, and the White Bluff to be all outcrops of one bed. In 

 lithological contents the beds are very similar, differing 

 almost wholly in the varying size of the lava fragments of 

 which they are mainly composed. The arrangement, too, is 

 similar, the coarsest fragments being about a third of the 

 way from the bottom. The agreement in fossil contents is 

 shown in three parallel columns on pages 468-9. 



At the White Bluff I had not more than ten minutes to 

 collect, but was fortunate enough to come upon a very fossil- 

 iferous patch of Bryozoa. With a more careful search I think 

 it very probable that other Pectens at least would be found ; 

 but, at all events, the fossil contents are very similar. The 

 identifications were made chiefly by a comparison with the 



