396 Transactions. — Geology. 



Papakura beds rest conformably on the brown-coal mea- 

 sures. 



8. The unconformity between the Waitematas and the 

 hydraulic limestone at the Wade has been pointed out both by 

 Mr. McKay and myself.''' 



In 1885 I contended for an unconformity between the "Wai- 

 tematas and the brown-coal measures, not because I had any 

 stratigraphical evidence to prove this, but only on account of 

 the conformable relations supposed by the Geological Survey 

 to exist between the brown-coal measures and the chalk- 

 marls, which I had shown to be unconformably overlain by the 

 Waitematas. The unconformity I placed at this point was 

 only a conditional one. 



In his progress report for 1885 Sir James Hector dis- 

 sents from my view that the Parnell grit is the horizontal 

 equivalent of the Takapuna breccia, which he considers of 

 Pliocene age and quite unconformable to the Waitemata 

 series.! In support of this he shows two views of a section 

 on the coast north of Lake Takapuna, which he believes 

 favours his unconformity. It should, however, be pointed out 

 that wherever the strata occupy a horizontal or undulating 

 position the breccia is seen to be interbedded with and quite 

 conformable to the adjacent beds, and at its base is frequently 

 more or less false-bedded with the underlying clays and sand- 

 stones. On the other hand, at points of severe local disturb- 

 ance, where the breccia is present, the softer and more yielding 

 clays and soft sandstones have in many instances been 

 crushed and contorted and often turned over the more com- 

 pact, heavy, and unyielding ash-bed, thus giving rise to 

 apparent unconformity. 



Sir James advances a rather curious theory for the origin 

 of this fossiliferous breccia. He supposes that it accumulated 

 in great pot-holes during volcanic eruptions in Pliocene times. 

 It would be interesting to know what formed these holes, also 

 what geological agencies were in operation at that time to 

 limit the distribution of the breccia and its imbedded life to 

 these repositories. 



As a matter of fact the breccia has a linear extension of 

 many miles, extending from the Waitemata to Whangaparaoa 

 Peninsula, and varying in thickness from 10ft. to 20ft. As to 

 its age, it contains Terchratclla dorsata, Pccteniiohjmorphoidcs, 

 Celleporina, and many net and branching corals and cup- 

 shaped Bryozoa, w^hicli led Mr. McKay to correlate it with the 

 slaty breccia at Cape Eodney, which has always been con- 

 sidered as Lower Miocene. | 



* " Geological Reports," 1883-84, p. 103 ; 1885-86, p. 162. 

 t " Geological Reports," 1885-86, p. xxxviii. 

 \ " Geological Reports," 1883-84, p. 101. 



