406 Transactions. — Geology. 



horizon in North Canterbury and elsewhere. As the Amurf 

 limestone could not both underlie and overlie the same forma- 

 tion, Captain Hutton naturally concluded that the hydraulic 

 limestone had no connection with the Amuri limestone of the 

 South Island. 



In 1899 I revisited the north Auckland coalfields, and, 

 after a careful re-examination of the old sections and many 

 new, formed the opinion that the Geological Survey was- 

 right in correlating the hydraulic limestone with the x\muri 

 limestone, but wrong in placing the hydraulic limestone above 

 the Whangarei limestone. 



In 1874 Sir James Hector placed the "grey and chalk 

 marls " [hydraulic limestone] of the Kaipara district at the 

 top of the Cretaceo-tertiary series, in which he also included 

 the underlying greensands and Inocerarmis clays, in the fol- 

 lowing order : — '■^- 



[■4. Grey and chalk marls. 

 Cretaceo-tertiary j 5. Greensands and coal grits. 

 (6. Inoceramus clays, &c. 



Mr. Cox, in his report on the Kaipara district in 1880, also 

 refers the hydraulic limestone and underlying glauconitic 

 greensands to the Cretaceo-tertiary period. I He discusses 

 the stratigraphical position of the hydraulic limestone, and,, 

 when speaking of the large boulders incrusted with cone-in- 

 cone limestone at Batley, says, on page 21, " If these cone-in 

 cone beds are interstratified with the chalk marls and hy- 

 draulic limestones, as they appear to be, it would give a certain 

 amount of evidence in favour of the whole series being older 

 than I have considered it " — that is, than Cretaceo-tertiary. 

 On page 19 he gives a section near Captain Colbeck's, at 

 Pahi, in which the Whangarei limestone and what he calls 

 "Miocene greensands" are shown lying unconformably on 

 the hydraulic limestone. 



Mr. McKay, in 1883, in his report " On the Geology of the 

 Coal-bearing Area between Whangarei and Hokianga,":^ 

 places the Amiu'i [hydraulic] limestone and chalk marls below 

 the Ototara and Weka Pass stone [Oamaru stone] , and it is 

 noteworthy that, while Mr. Cox shows the Whangarei lime- 

 stone at Colbeck's resting in a narrow gutter excavated in the 

 hydraulic limestone, Mr. McKay states that the hydraidic 

 limestone is underlain conformably by the Whangarei lime- 

 stone (page 115), which obviously, according to this view, 

 could not be the equivalent of the Oamaru stone. 



In his report on Waitemata and Eodney Counties § in the 



♦ Repti. Geol. Expl., 1874, p. vi. 

 t Reps. Geol. Expl., 1879-80, p. 18. 

 \ Reps. Geol. Expl., 1883-84, p. 113. 

 ^ Loc. cit., p. 106. 



