Thomson. — Diastrophic Correlation and Districts in the Notocene. 401 



Waitotaran, those of Wanganui are Castleeliffian . Regional sea-advance and 

 sea-retreat may have been operative all the time, but differential movements 

 of the land surface were certainly also operative in an important measure, 

 and the total effect of the movements of land and sea resulted in the forma- 

 tion of sedimentary series in different districts, each of which resembles a full 

 cycle of sedimentation but does not coincide in point of phase with the 

 series of other districts. 



We are thus led to the discrimination of minor diastrophic districts in 

 New Zealand during the general relative inactivity between the great post- 

 Hokonui and Kaikoura deformations. Two such districts were indicated 

 by me (1916, No. 2) in contrasting the Amuri and Ototara limestones, and 

 there are many others. It is the presence of these districts that has given 

 rise to the problems of classification and correlation which have so much 

 impeded geological inquiry in New Zealand, and it will be by a clearer 

 recognition of them that the problems will be elucidated. 



Marshall (1916, No. 1) has supplemented his original diastrophic argu- 

 ment for the correlation of all the younger limestones of New Zealand by 

 an argument based on palaeontological grounds. His conclusion as to the 

 equivalence in age of the Ototara and Amuri limestones is directly opposed 

 to the conclusions drawn by me (1916, No. 2), and one or the other must 

 be wrong. As a matter of fact, Marshall has reasoned incorrectly. The 

 Ototara limestone contains Amphistegina, and so also do the polyzoal 

 limestones of Whangarei (Horahora and Waro). " The frequent occurrence 

 of Amphistegina thus points decisively to a Miocene age for this rock, and 

 this organism may be used to correlate all those limestones in which it 

 occurs, for it appears to be the same species in all of them." In passing, 

 it may be pointed out that the premises do not justify the conclusion. The 

 genus Amphistegina, on Marshall's own showing, ranges from Upper Eocene 

 to Recent, and the species in question may, like other species of Foraminifera 

 have a range nearly as large as that of the genus. Having thus correlated the 

 Ototara and Whangarei limestones, Marshall then states that it is the general 

 opinion of geologists that the Whangarei limestone is a lower horizon than 

 the hydraulic limestone in the North of Auckland, or at least that the two 

 limestones belong to the same series. The Amuri limestone, he continues, 

 has always been correlated with the hydraulic limestone, and is therefore 

 of approximately the same age as the Ototara limestone. No palaeonto- 

 logical evidence has been presented for the correlation of the Amuri and 

 the Whangarei hydraulic limestones, and, until it has, the correlation of 

 the Amuri limestone with the Ototara limestone by the intermediary of 

 the Whangarei hydraulic and polyzoal limestones cannot be given any 

 weight. 



Marshall supports his arguments by stating that " the Otaio lime- 

 stone, which is always regarded as an outcrop of the Amuri limestone, 

 and which is a very fine-grained type of rock with an abundance of 

 Globigerina, also contains this Amphistegina, which is apparently the same 

 species as in other parts of the country." The only reason advanced 

 for regarding the Otaio limestone as an outcrop of the Amuri lime- 

 stone is its lithological nature. It is not directly underlain, as is the 

 Amuri limestone, by Cretaceous rocks. It lies within the diastrophic 

 district of north-east Otago and South Canterbury, where the sequence 

 commences with Ngaparan coal-beds, and within which no Cretaceous rocks 

 have ever been found. The typical Amuri limestone is always underlain 

 by rocks containing Cretaceous fossils, and has never been found resting 



